J. Richman

Based on the full BABAR data sample, we report improved measurements of the ratios R(D(*))=B(B[over ¯]→D(*)τ(-)ν[over ¯](τ))/B(B[over ¯]→D(*)ℓ(ℓ)(-)ν[over ¯](ℓ)), where ℓ is either e or μ. These ratios are sensitive to new physics contributions in the form of a charged Higgs boson. We measure R(D)=0.440±0.058±0.042 and R(D(*))=0.332±0.024±0.018, which exceed the standard model expectations by 2.0σ and 2.7σ, respectively. Taken together, our results disagree with these expectations at the 3.4σ level. This excess cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model.

The new detector for data recording by the CLEO collaboration at the Cornell Electron Storage Ring is described. This detector has been designed to optimize studying e+ e− annihilation into hadronic matter at a total energy of 10 GeV. It consists of high precesion charged particle tracking chambers and an electromagnetic calorimeter together with systems for particle identification. The design of the detector and its performance over the first year and a half of operation are presented.

Based on the full BaBar data sample, we report improved measurements of the ratios R(D(*)) = B(B -> D(*) Tau Nu)/B(B -> D(*) l Nu), where l is either e or mu. These ratios are sensitive to new physics contributions in the form of a charged Higgs boson. We measure R(D) = 0.440 +- 0.058 +- 0.042 and R(D*) = 0.332 +- 0.024 +- 0.018, which exceed the Standard Model expectations by 2.0 sigma and 2.7 sigma, respectively. Taken together, our results disagree with these expectations at the 3.4 sigma level. This excess cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model. Kinematic distributions presented here exclude large portions of the more general type III two-Higgs-doublet model, but there are solutions within this model compatible with the results.

Searches for lepton-flavor-violating decays of a tau lepton to a lighter mass lepton and a photon have been performed with the entire data set of (963+/-7)x10{6} tau decays collected by the BABAR detector near the Upsilon(4S), Upsilon(3S) and Upsilon(2S) resonances. The searches yield no evidence of signals and we set upper limits on the branching fractions of B(tau{+/-}-->e{+/-}gamma)<3.3x10{-8} and B(tau{+/-}-->mu{+/-}gamma)<4.4x10{-8} at 90% confidence level.

Using the CLEO II detector, we have measured the differential cross sections for exclusive two-photon production of light pseudoscalar mesons ${\ensuremath{\pi}}^{0},$ \ensuremath{\eta}, and ${\ensuremath{\eta}}^{\ensuremath{'}}.$ From our measurements we have obtained the form factors associated with the electromagnetic transitions ${\ensuremath{\gamma}}^{*}\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}}\mathrm{meson}.$ We have measured these form factors in the momentum transfer ranges from 1.5 to 9, 20, and $30{\mathrm{GeV}}^{2}$ for ${\ensuremath{\pi}}^{0},$ \ensuremath{\eta}, and ${\ensuremath{\eta}}^{\ensuremath{'}},$ respectively, and have made comparisons to various theoretical predictions.

Dark sectors charged under a new Abelian force have recently received much attention in the context of dark matter models. These models introduce a light new mediator, the so-called dark photon (A'), connecting the dark sector to the Standard Model. We present a search for a dark photon in the reaction e+e- -> gamma A', A'-> e+e-, mu+mu- using 514 fb-1 of data collected with the BABAR detector. We do not observe a significant signal and we set 90% confidence level upper limits on the mixing strength between the photon and dark photon at the level of 10^-4 - 10^-3 for dark photon masses in the range 0.02 - 10.2 GeV. We further constrain the range of the parameter space favored by interpretations of the discrepancy between the calculated and measured anomalous magnetic moment of the muon.

We study the reaction e+e- --> e+e-pi0 and measure the gamma gamma* --> pi0 transition form factor in the momentum transfer range from 4 to 40 GeV^2. The analysis is based on 442 fb^-1 of integrated luminosity collected at PEP-II with the BABAR detector at e+e- center-of-mass energies near 10.6 GeV.

A precise measurement of the cross section of the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}(\ensuremath{\gamma})$ from threshold to an energy of 3 GeV is obtained with the initial state radiation (ISR) method using $232\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data collected with the BABAR detector at ${e}^{+}{e}^{\ensuremath{-}}$ center-of-mass energies near 10.6 GeV. The ISR luminosity is determined from a study of the leptonic process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}\ensuremath{\gamma}(\ensuremath{\gamma})$. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the $\ensuremath{\pi}\ensuremath{\pi}$ cross section measured from threshold to 1.8 GeV is $\mathbf{(}514.1\ifmmode\pm\else\textpm\fi{}2.2(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}3.1(\mathrm{syst})\mathbf{)}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$.

We present evidence for D0-D(0) mixing in D(0)-->K(+)pi(-) decays from 384 fb(-1) of e(+)e(-) colliding-beam data recorded near square root s=10.6 GeV with the BABAR detector at the PEP-II storage rings at the Stanford Linear Accelerator Center. We find the mixing parameters x('2)=[-0.22+/-0.30(stat)+/-0.21(syst)] x 10(-3) and y(')=[9.7+/-4.4(stat)+/-3.1(syst)] x 10(-3) and a correlation between them of -0.95. This result is inconsistent with the no-mixing hypothesis with a significance of 3.9 standard deviations. We measure R(D), the ratio of doubly Cabibbo-suppressed to Cabibbo-favored decay rates, to be [0.303+/-0.016(stat)+/-0.010(syst)]%. We find no evidence for CP violation.

In a search for $B\ensuremath{\rightarrow}c\overline{c}\ensuremath{\gamma}K$ decays with the BABAR detector, where $c\overline{c}$ includes $J/\ensuremath{\psi}$ and $\ensuremath{\psi}(2S)$, and $K$ includes ${K}^{\ifmmode\pm\else\textpm\fi{}}$, ${K}_{S}^{0}$, and ${K}^{*}(892)$, we find evidence for $X(3872)\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\gamma}$ and $X(3872)\ensuremath{\rightarrow}\ensuremath{\psi}(2S)\ensuremath{\gamma}$ with $3.6\ensuremath{\sigma}$ and $3.5\ensuremath{\sigma}$ significance, respectively. We measure the product of branching fractions $\mathcal{B}\mathbf{(}{B}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}X(3872){K}^{\ifmmode\pm\else\textpm\fi{}}\mathbf{)}\ifmmode\times\else\texttimes\fi{}\mathcal{B}\mathbf{(}X(3872)\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\gamma}\mathbf{)}=[2.8\ifmmode\pm\else\textpm\fi{}0.8(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.1(\mathrm{syst})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ and $\mathcal{B}\mathbf{(}{B}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}X(3872){K}^{\ifmmode\pm\else\textpm\fi{}}\mathbf{)}\ifmmode\times\else\texttimes\fi{}\mathcal{B}\mathbf{(}X(3872)\ensuremath{\rightarrow}\ensuremath{\psi}(2S)\ensuremath{\gamma}\mathbf{)}=[9.5\ifmmode\pm\else\textpm\fi{}2.7(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.6(\mathrm{syst})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$.

A precise measurement of the cross section of the process $e^+e^-\to\pi^+\pi^-(\gamma)$ from threshold to an energy of 3GeV is obtained with the initial-state radiation (ISR) method using 232fb$^{-1}$ of data collected with the BaBar detector at $e^+e^-$ center-of-mass energies near 10.6GeV. The ISR luminosity is determined from a study of the leptonic process $e^+e^-\to\mu^+\mu^-(\gamma)\gamma_{\rm ISR}$, which is found to agree with the next-to-leading-order QED prediction to within 1.1%. The cross section for the process $e^+e^-\to\pi^+\pi^-(\gamma)$ is obtained with a systematic uncertainty of 0.5% in the dominant $\rho$ resonance region. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the measured $\pi\pi$ cross section from threshold to 1.8GeV is $(514.1 \pm 2.2({\rm stat}) \pm 3.1({\rm syst}))\times 10^{-10}$.

We present a study of the decays B^{0,+} --> J/psi pi^+ pi^- pi^0 K^{0,+}, using 467 10^6 BBbar pairs recorded with the BABAR detector. We present evidence for the decay mode X(3872) --> J/psi omega, with product branching fractions B(B^+ --> X(3872)K^+) B(X(3872) --> J/psi omega) =[0.6\pm0.2\stat \pm 0.1\syst ] 10^{-5}, and B(B^0 --> X(3872)K^0) B(X(3872) --> J/psi omega) =[0.6\pm0.3\stat \pm 0.1\syst ] 10^{-5}. A detailed study of the pi^+ pi^- pi^0 mass distribution from X(3872) decay favors a negative-parity assignment.

In a sample of 471 million BB events collected with the BABAR detector at the PEP-II e+e- collider we study the rare decays B -> K(*) l+ l-, where l+ l- is either e+e- or mu+mu-. We report results on partial branching fractions and isospin asymmetries in seven bins of di-lepton mass-squared. We further present CP and lepton-flavor asymmetries for di-lepton masses below and above the J/psi resonance. We find no evidence for CP or lepton-flavor violation. The partial branching fractions and isospin asymmetries are consistent with the Standard Model predictions and with results from other experiments.

We study the processes ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}2({\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}){\ensuremath{\pi}}^{0}\ensuremath{\gamma}$, $2({\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})\ensuremath{\eta}\ensuremath{\gamma}$, ${K}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}$ and ${K}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\eta}\ensuremath{\gamma}$ with the hard photon radiated from the initial state. About 20 000, 4300, 5500, and 375 fully reconstructed events, respectively, are selected from $232\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of BABAR data. The invariant mass of the hadronic final state defines the effective ${e}^{+}{e}^{\ensuremath{-}}$ center-of-mass energy, so that the obtained cross sections from the threshold to about 5 GeV can be compared with corresponding direct ${e}^{+}{e}^{\ensuremath{-}}$ measurements, currently available only for the $\ensuremath{\eta}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and $\ensuremath{\omega}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ submodes of the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}2({\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}){\ensuremath{\pi}}^{0}$ channel. Studying the structure of these events, we find contributions from a number of intermediate states, and we extract their cross sections where possible. In particular, we isolate the contribution from ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\omega}(782){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and study the $\ensuremath{\omega}(1420)$ and $\ensuremath{\omega}(1650)$ resonances. In the charmonium region, we observe the $J/\ensuremath{\psi}$ in all these final states and several intermediate states, as well as the $\ensuremath{\psi}(2S)$ in some modes, and we measure the corresponding branching fractions.

We present a study of the decays B0,+→J/ψωK0,+ using 383×106 B¯¯¯B events obtained with the BABAR detector at PEP-II. We observe Y(3940)→J/ψω, with mass 3914.6+3.8−3.4(stat)±2.0(syst) MeV/c2, and width 34+12−8(stat)±5(syst) MeV. The ratio of B0 and B+ decay to YK is 0.27+0.28−0.23(stat)+0.04−0.01(syst), and the relevant B0 and B+ branching fractions are reported.Received 14 November 2007DOI:https://doi.org/10.1103/PhysRevLett.101.082001©2008 American Physical Society

We report the results of a search for $Z(4430)^-$ decay to $J/\psi\pi^-$ or $\psi(2S)\pi^-$ in $B^{-,0}\to \jpsi\pi^- K^{0,+}$ and $B^{-,0}\to \psitwos \pi^- K^{0,+}$ decays. The data were collected with the BABAR detector at the SLAC PEP-II asymmetric-energy $e^+e^-$ collider operating at center of mass energy 10.58 \gev, and the sample corresponds to an integrated luminosity of 413 fb$^{-1}$. Each $K\pi$ mass distribution exhibits clear $K^{\ast}(892)$ and $K^{\ast}_2(1430)$ signals, and the efficiency-corrected spectrum is well-described by a superposition of the associated Breit-Wigner intensity distributions, together with an $S$-wave contribution obtained from the LASS $I=1/2$ $K\pi$ scattering amplitude measurements. Each $K\pi$ angular distribution varies significantly in structure with $K\pi$ mass, and is represented in terms of low-order Legendre polynomial moments. We find that each $J/\psi\pi$ or $\psi(2S)\pi$ mass distribution is well-described by the reflection of the measured $K\pi$ mass and angular distribution structures. We see no significant evidence for a $Z(4430)^-$ signal for any of the processes investigated, neither in the total $J/\psi\pi$ or $\psi(2S)\pi$ mass distribution, nor in the corresponding distributions for the regions of $K\pi$ mass for which observation of the $Z(4430)^-$ signal was reported. We obtain branching fraction upper limits ${\cal{B}}(B^-\to Z^-\bar{K^0}, Z^-\to J/\psi\pi^-)<1.5\times 10^{-5}$, ${\cal{B}}(B^0\to Z^-K^+, Z^-\to J/\psi\pi^-)<0.4\times 10^{-5}$, ${\cal{B}}(B^-\to Z^-\bar{K^0}, Z^-\to \psi(2S)\pi^-)<4.7\times 10^{-5}$, and ${\cal{B}}(B^0\to Z^-K^+, Z^-\to \psi(2S)\pi^-)<3.1\times 10^{-5}$ at 95% confidence level, where the $Z(4430)^-$ mass and width have been fixed to the reported central values.

We search for the flavor-changing neutral-current decays $B\ensuremath{\rightarrow}{K}^{(*)}\ensuremath{\nu}\overline{\ensuremath{\nu}}$, and the invisible decays $J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\nu}\overline{\ensuremath{\nu}}$ and $\ensuremath{\psi}(2S)\ensuremath{\rightarrow}\ensuremath{\nu}\overline{\ensuremath{\nu}}$ via $B\ensuremath{\rightarrow}{K}^{(*)}J/\ensuremath{\psi}$ and $B\ensuremath{\rightarrow}{K}^{(*)}\ensuremath{\psi}(2S)$, respectively, using a data sample of $471\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs collected by the BABAR experiment. We fully reconstruct the hadronic decay of one of the $B$ mesons in the $\ensuremath{\Upsilon}(4S)\ensuremath{\rightarrow}B\overline{B}$ decay, and search for the $B\ensuremath{\rightarrow}{K}^{(*)}\ensuremath{\nu}\overline{\ensuremath{\nu}}$ decay in the rest of the event. We observe no significant excess of signal decays over background and report branching fraction upper limits of $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{K}^{+}\ensuremath{\nu}\overline{\ensuremath{\nu}})&lt;3.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$, $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{K}^{0}\ensuremath{\nu}\overline{\ensuremath{\nu}})&lt;8.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$, $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{K}^{*+}\ensuremath{\nu}\overline{\ensuremath{\nu}})&lt;11.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$, $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{K}^{*0}\ensuremath{\nu}\overline{\ensuremath{\nu}})&lt;9.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$, and combined upper limits of $\mathcal{B}(B\ensuremath{\rightarrow}K\ensuremath{\nu}\overline{\ensuremath{\nu}})&lt;3.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ and $\mathcal{B}(B\ensuremath{\rightarrow}{K}^{*}\ensuremath{\nu}\overline{\ensuremath{\nu}})&lt;7.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$, all at the 90% confidence level. For the invisible quarkonium decays, we report branching fraction upper limits of $\mathcal{B}(J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\nu}\overline{\ensuremath{\nu}})&lt;3.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ and $\mathcal{B}(\ensuremath{\psi}(2S)\ensuremath{\rightarrow}\ensuremath{\nu}\overline{\ensuremath{\nu}})&lt;15.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ at the 90% confidence level. Using the improved kinematic resolution achieved from hadronic reconstruction, we also provide partial branching fraction limits for the $B\ensuremath{\rightarrow}{K}^{(*)}\ensuremath{\nu}\overline{\ensuremath{\nu}}$ decays over the full kinematic spectrum.

We present a study of resonances in exclusive decays of $B$ mesons to ${\overline{D}}^{(*)}{D}^{(*)}K$. We report the observation of the decays $B\ensuremath{\rightarrow}{\overline{D}}^{(*)}{D}_{s1}^{+}(2536)$ where the ${D}_{s1}^{+}(2536)$ is reconstructed in the ${D}^{*0}{K}^{+}$ and ${D}^{*+}{K}_{S}^{0}$ decay channels. We report also the observation of the decays $B\ensuremath{\rightarrow}\ensuremath{\psi}(3770)K$ where the $\ensuremath{\psi}(3770)$ decays to ${\overline{D}}^{0}{D}^{0}$ and ${D}^{\ensuremath{-}}{D}^{+}$. In addition, we present the observation of an enhancement for the ${\overline{D}}^{*0}{D}^{0}$ invariant mass in the decays $B\ensuremath{\rightarrow}{\overline{D}}^{*0}{D}^{0}K$, at a mass of $({3875.1}_{\ensuremath{-}0.5}^{+0.7}\ifmmode\pm\else\textpm\fi{}0.5)\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ with a width of $({3.0}_{\ensuremath{-}1.4}^{+1.9}\ifmmode\pm\else\textpm\fi{}0.9)\text{ }\text{ }\mathrm{MeV}$ (the first errors are statistical and the second are systematic). Branching fractions and spin studies are shown for the three resonances. The results are based on $347\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data collected with the BABAR detector at the PEP-II $B$ factory.

The process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}p\overline{p}\ensuremath{\gamma}$ is studied using $469\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of integrated luminosity collected with the BABAR detector at the SLAC National Accelerator Laboratory, at an ${e}^{+}{e}^{\ensuremath{-}}$ center-of-mass energy of 10.6 GeV. From the analysis of the $p\overline{p}$ invariant mass spectrum, the energy dependence of the cross section for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}p\overline{p}$ is measured from threshold to 4.5 GeV. The energy dependence of the ratio of electric and magnetic form factors, $|{G}_{E}/{G}_{M}|$, and the asymmetry in the proton angular distribution are measured for $p\overline{p}$ masses below 3 GeV. The branching fractions for the decays $J/\ensuremath{\psi}\ensuremath{\rightarrow}p\overline{p}$ and $\ensuremath{\psi}(2S)\ensuremath{\rightarrow}p\overline{p}$ are also determined.

We present an analysis of exclusive charmless semileptonic $B$-meson decays based on $377\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs recorded with the BABAR detector at the $\mathit{\ensuremath{\Upsilon}}(4S)$ resonance. We select four event samples corresponding to the decay modes ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$, ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$, ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ensuremath{-}}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$, and ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$ and find the measured branching fractions to be consistent with isospin symmetry. Assuming isospin symmetry, we combine the two $B\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\ell}\ensuremath{\nu}$ samples, and similarly the two $B\ensuremath{\rightarrow}\ensuremath{\rho}\ensuremath{\ell}\ensuremath{\nu}$ samples, and measure the branching fractions $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\ell}}^{+}\ensuremath{\nu})=(1.41\ifmmode\pm\else\textpm\fi{}0.05\ifmmode\pm\else\textpm\fi{}0.07)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ and $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ensuremath{-}}{\ensuremath{\ell}}^{+}\ensuremath{\nu})=(1.75\ifmmode\pm\else\textpm\fi{}0.15\ifmmode\pm\else\textpm\fi{}0.27)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$, where the errors are statistical and systematic. We compare the measured distribution in ${q}^{2}$, the momentum transfer squared, with predictions for the form factors from QCD calculations and determine the Cabibbo-Kobayashi-Maskawa matrix element $|{V}_{ub}|$. Based on the measured partial branching fraction for $B\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\ell}\ensuremath{\nu}$ in the range ${q}^{2}&lt;12\text{ }\text{ }{\mathrm{GeV}}^{2}$ and the most recent QCD light-cone sum-rule calculations, we obtain $|{V}_{ub}|=(3.78\ifmmode\pm\else\textpm\fi{}{0.13}_{\ensuremath{-}0.40}^{+0.55})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$, where the errors refer to the experimental and theoretical uncertainties. From a simultaneous fit to the data over the full ${q}^{2}$ range and the FNAL/MILC lattice QCD results, we obtain $|{V}_{ub}|=(2.95\ifmmode\pm\else\textpm\fi{}0.31)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ from $B\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\ell}\ensuremath{\nu}$, where the error is the combined experimental and theoretical uncertainty.

We describe a measurement of the time-integrated luminosity of the data collected by the BABAR experiment at the PEP-II asymmetric-energy e+e- collider at the ϒ(4S), ϒ(3S), and ϒ(2S) resonances and in a continuum region below each resonance. We measure the time-integrated luminosity by counting e+e-→e+e- and (for the ϒ(4S) only) e+e-→μ+μ- candidate events, allowing additional photons in the final state. We use data-corrected simulation to determine the cross-sections and reconstruction efficiencies for these processes, as well as the major backgrounds. Due to the large cross-sections of e+e-→e+e- and e+e-→μ+μ-, the statistical uncertainties of the measurement are substantially smaller than the systematic uncertainties. The dominant systematic uncertainties are due to observed differences between data and simulation, as well as uncertainties on the cross-sections. For data collected on the ϒ(3S) and ϒ(2S) resonances, an additional uncertainty arises due to ϒ→e+e-X background. For data collected off the ϒ resonances, we estimate an additional uncertainty due to time dependent efficiency variations, which can affect the short off-resonance runs. The relative uncertainties on the luminosities of the on-resonance (off-resonance) samples are 0.43% (0.43%) for the ϒ(4S), 0.58% (0.72%) for the ϒ(3S), and 0.68% (0.88%) for the ϒ(2S).

We study the reactions e+e−→e+e−η(') in the single-tag mode and measure the γγ∗→η(') transition form factors in the momentum-transfer range from 4 to 40 GeV2. The analysis is based on 469 fb−1 of integrated luminosity collected at PEP-II with the BABAR detector at e+e− center-of-mass energies near 10.6 GeV.11 MoreReceived 5 January 2011DOI:https://doi.org/10.1103/PhysRevD.84.052001© 2011 American Physical Society

We present measurements of Collins asymmetries in the inclusive process e+e- -->pi pi X, where pi stands for charged pions, at a center-of-mass energy of 10.6 GeV. We use a data sample of 468 fb-1 collected by the BABAR experiment at the PEP-II B factory at SLAC, and consider pairs of charged pions produced in opposite hemispheres of hadronic events. We observe clear asymmetries in the distributions of the azimuthal angles in two distinct reference frames. We study the dependence of the asymmetry on several kinematic variables, finding that it increases with increasing pion momentum and momentum transverse to the analysis axis, and with increasing angle between the thrust and beam axis.

We study the process ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\psi}(2S){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ with initial-state-radiation events produced at the PEP-II asymmetric-energy collider. The data were recorded with the BABAR detector at center-of-mass energies at and near the $\mathrm{\ensuremath{\Upsilon}}(\mathrm{nS})$ ($n=2,3,4$) resonances and correspond to an integrated luminosity of $520\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. We investigate the $\ensuremath{\psi}(2S){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ mass distribution from 3.95 to $5.95\text{ }\text{ }\mathrm{GeV}/{c}^{2}$, and measure the center-of-mass energy dependence of the associated ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\psi}(2S){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ cross section. The mass distribution exhibits evidence of two resonant structures. A fit to the $\ensuremath{\psi}(2S){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ mass distribution corresponding to the decay mode $\ensuremath{\psi}(2S)\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ yields a mass value of $4340\ifmmode\pm\else\textpm\fi{}16\text{ }(\text{stat})\text{ }\ifmmode\pm\else\textpm\fi{}9\text{ }(\text{syst})\text{ }\text{ }\mathrm{MeV}/{c}^{2}\text{ }$ and a width of $94\ifmmode\pm\else\textpm\fi{}32\text{ }(\text{stat})\text{ }\ifmmode\pm\else\textpm\fi{}13\text{ }(\text{syst})\text{ }\text{ }\mathrm{MeV}$ for the first resonance, and for the second a mass value of $4669\ifmmode\pm\else\textpm\fi{}21\text{ }(\text{stat})\text{ }\ifmmode\pm\else\textpm\fi{}3\text{ }(\text{syst})\text{ }\text{ }\mathrm{MeV}/{c}^{2}\text{ }$ and a width of $104\ifmmode\pm\else\textpm\fi{}48\text{ }(\text{stat})\text{ }\ifmmode\pm\else\textpm\fi{}10\text{ }(\text{syst})\text{ }\text{ }\mathrm{MeV}$. In addition, we show the ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ mass distributions for these resonant regions.

The authors review the experimental measurements and theoretical descriptions of leptonic and semileptonic decays of particles containing a single heavy quark, either charm or bottom. Measurements of bottom semileptonic decays are used to determine the magnitudes of two fundamental parameters of the standard model, the Cabibbo-Kobayashi-Maskawa matrix elements ${V}_{\mathrm{cb}}$ and ${V}_{\mathrm{ub}}$. These parameters are connected with the physics of quark flavor and mass, and they have important implications for the breakdown of $\mathrm{CP}$ symmetry. To extract precise values of $|{V}_{\mathrm{cb}}|$ and $|{V}_{\mathrm{ub}}|$ from measurements, however, requires a good understanding of the decay dynamics. Measurements of both charm and bottom decay distributions provide information on the interactions governing these processes. The underlying weak transition in each case is relatively simple, but the strong interactions that bind the quarks into hadrons introduce complications. The authors also discuss new theoretical approaches, especially heavy-quark effective theory and lattice QCD, which are providing insights and predictions now being tested by experiment. An international effort at many laboratories will rapidly advance knowledge of this area of physics during the next decade.

We study the e+e−→Λ¯¯¯Λγ, Λ¯¯¯Σ0γ, Σ0¯¯¯Σ0γ processes using 230 fb−1 of integrated luminosity collected by the BABAR detector at e+e− center-of-mass energy of 10.58 GeV. From the analysis of the baryon-antibaryon mass spectra the cross sections for e+e−→Λ¯¯¯Λ, Λ¯¯¯Σ0, Σ0¯¯¯Σ0 are measured in the dibaryon mass range from threshold up to 3 GeV/c2. The ratio of electric and magnetic form factors, |GE/GM|, is measured for e+e−→Λ¯¯¯Λ, and limits on the relative phase between Λ form factors are obtained. We also measure the J/ψ→Λ¯¯¯Λ, Σ0¯¯¯Σ0, and ψ(2S)→Λ¯¯¯Λ branching fractions.24 MoreReceived 12 September 2007DOI:https://doi.org/10.1103/PhysRevD.76.092006©2007 American Physical Society

We present updated measurements of time-dependent CP asymmetries in fully reconstructed neutral B decays containing a charmonium meson. The measurements reported here use a data sample of (465±5)×106 Υ(4S)→B¯¯¯B decays collected with the BABAR detector at the PEP-II asymmetric energy e+e− storage rings operating at the SLAC National Accelerator Laboratory. The time-dependent CP asymmetry parameters measured from JψK0S, JψK0L, ψ(2S)K0S, ηcK0S, χc1K0S, and J/ψK∗(892)0 decays are: Cf=0.024±0.020(stat)±0.016(syst) and −ηfSf=0.687±0.028(stat)±0.012(syst).Received 10 February 2009DOI:https://doi.org/10.1103/PhysRevD.79.072009©2009 American Physical Society

We observe the decays ${D}_{s1}^{*}(2710{)}^{+}\ensuremath{\rightarrow}{D}^{*}K$ and ${D}_{sJ}^{*}(2860{)}^{+}\ensuremath{\rightarrow}{D}^{*}K$ and measure their branching fractions relative to the $DK$ final state. We also observe, in the ${D}^{*}K$ mass spectrum, a new broad structure at a mass of $(3044\ifmmode\pm\else\textpm\fi{}{8}_{\mathrm{stat}}(\genfrac{}{}{0}{}{+30}{\ensuremath{-}5}{)}_{\mathrm{syst}})\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ having a width $\ensuremath{\Gamma}=(239\ifmmode\pm\else\textpm\fi{}{35}_{\mathrm{stat}}(\genfrac{}{}{0}{}{+46}{\ensuremath{-}42}{)}_{\mathrm{syst}})\text{ }\text{ }\mathrm{MeV}$. To obtain this result we use $470\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data recorded by the BABAR detector at the PEP-II asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ storage rings at the Stanford Linear Accelerator Center running at center-of-mass energies near 10.6 GeV.

We report a direct measurement of D0−D¯0 mixing parameters through a time-dependent amplitude analysis of the Dalitz plots of D0→KS0π+π− and, for the first time, D0→KS0K+K− decays. The low-momentum pion πs+ in the decay D*+→D0πs+ identifies the flavor of the neutral D meson at its production. Using 468.5 fb−1 of e+e− colliding-beam data recorded near s=10.6 GeV by the BABAR detector at the PEP-II asymmetric-energy collider at SLAC, we measure the mixing parameters x=[1.6±2.3(stat)±1.2(syst)±0.8(model)]×10−3, and y=[5.7±2.0(stat)±1.3(syst)±0.7(model)]×10−3. These results provide the best measurement to date of x and y. The knowledge of the value of x, in particular, is crucial for understanding the origin of mixing.Received 28 April 2010DOI:https://doi.org/10.1103/PhysRevLett.105.081803© 2010 The American Physical Society

We present measurements of the decays B+ -> X(3872) K+ and B0 -> X(3872) K0 with X(3872) -> Jpsi pi+ pi-. The data sample used, collected with the BABAR detector at the PEP-II e+e- asymmetric-energy storage ring, corresponds to 455 x 10^6 BBbar pairs. Branching fraction measurements of BF(B+ -> X(3872) K+) x BF(X(3872) -> Jpsi pi+ pi-) = (8.4 +/- 1.5 +/- 0.7) x 10^{-6} and BF(B0 -> X(3872) K0) x BF(X(3872) -> Jpsi pi+ pi- = (3.5 +/- 1.9 +/- 0.4) x 10^{-6} are obtained. We set an upper limit on the natural width of the X(3872) of Gamma < 3.3 MeV/c^2 at the 90% confidence level.

We present measurements of the semileptonic decays B--->D0tau-nutau, B--->D*0tau-nutau, B0-->D+tau-nutau, and B0-->D*+tau-nutau, which are potentially sensitive to non-standard model amplitudes. The data sample comprises 232x10(6) Upsilon(4S)-->BB decays collected with the BABAR detector. From a combined fit to B- and B0 channels, we obtain the branching fractions B(B-->Dtau-nutau)=(0.86+/-0.24+/-0.11+/-0.06)% and B(B-->D*tau-nutau)=(1.62+/-0.31+/-0.10+/-0.05)% (normalized for the B0), where the uncertainties are statistical, systematic, and normalization-mode-related.

We report the results of a study of the exclusive charmless semileptonic decays, ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$, ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$, ${B}^{+}\ensuremath{\rightarrow}\ensuremath{\omega}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$, ${B}^{+}\ensuremath{\rightarrow}\ensuremath{\eta}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$, and ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\eta}}^{\ensuremath{'}}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$ ($\ensuremath{\ell}=e$ or $\ensuremath{\mu}$) undertaken with approximately $462\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs collected at the $\ensuremath{\Upsilon}(4S)$ resonance with the BABAR detector. The analysis uses events in which the signal $B$ decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions in several bins of ${q}^{2}$, the square of the momentum transferred to the lepton-neutrino pair, for ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$, ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$, ${B}^{+}\ensuremath{\rightarrow}\ensuremath{\omega}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$, and ${B}^{+}\ensuremath{\rightarrow}\ensuremath{\eta}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$. From these distributions, we extract the form-factor shapes ${f}_{+}({q}^{2})$ and the total branching fractions $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\ell}}^{+}\ensuremath{\nu})=(1.45\ifmmode\pm\else\textpm\fi{}{0.04}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.06}_{\mathrm{syst}})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ (combined ${\ensuremath{\pi}}^{\ensuremath{-}}$ and ${\ensuremath{\pi}}^{0}$ decay channels assuming isospin symmetry), $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}\ensuremath{\omega}{\ensuremath{\ell}}^{+}\ensuremath{\nu})=(1.19\ifmmode\pm\else\textpm\fi{}{0.16}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.09}_{\mathrm{syst}})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ and $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}\ensuremath{\eta}{\ensuremath{\ell}}^{+}\ensuremath{\nu})=(0.38\ifmmode\pm\else\textpm\fi{}{0.05}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.05}_{\mathrm{syst}})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$. We also measure $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\eta}}^{\ensuremath{'}}{\ensuremath{\ell}}^{+}\ensuremath{\nu})=(0.24\ifmmode\pm\else\textpm\fi{}{0.08}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.03}_{\mathrm{syst}})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$. We obtain values for the magnitude of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element $|{V}_{ub}|$ by direct comparison with three different QCD calculations in restricted ${q}^{2}$ ranges of $B\ensuremath{\rightarrow}\ensuremath{\pi}{\ensuremath{\ell}}^{+}\ensuremath{\nu}$ decays. From a simultaneous fit to the experimental data over the full ${q}^{2}$ range and the FNAL/MILC lattice QCD predictions, we obtain $|{V}_{ub}|=(3.25\ifmmode\pm\else\textpm\fi{}0.31)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$, where the error is the combined experimental and theoretical uncertainty.

We perform a study of the exclusive production of $D \bar D$, $D \bar D^*$, and $D^* \bar D^*$ in initial-state-radiation events, from $e^+ e^-$ annihilations at a center-of-mass energy near 10.58 GeV, to search for charmonium and possible new resonances. The data sample corresponds to an integrated luminosity of 384 $fb^{-1}$ and was recorded by the BaBar experiment at the PEP-II storage rings. The $D \bar D$, $D \bar D^*$, and $D^* \bar D^*$ mass spectra show clear evidence of several $\psi$ resonances. However, there is no evidence for $Y(4260) \to D \bar D^*$ or $Y(4260)\to D^* \bar D^*$.

We perform amplitude analyses of the decays $B^0 \to K^+K^-K^0_S$, $B^+ \rightarrow K^+K^-K^+$, and $B^+ \to K^0_S K^0_S K^+$, and measure CP-violating parameters and partial branching fractions. The results are based on a data sample of approximately $470\times 10^6$ $B\bar{B}$ decays, collected with the BABAR detector at the PEP-II asymmetric-energy $B$ factory at the SLAC National Accelerator Laboratory. For $B^+ \to K^+K^-K^+$, we find a direct CP asymmetry in $B^+ \to \phi(1020)K^+$ of $A_{CP}= (12.8\pm 4.4 \pm 1.3)%$, which differs from zero by $2.8 \sigma$. For $B^0 \to K^+K^-K^0_S$, we measure the CP-violating phase $\beta_{\rm eff} (\phi(1020)K^0_S) = (21\pm 6 \pm 2)^\circ$. For $B^+ \to K^0_S K^0_S K^+$, we measure an overall direct CP asymmetry of $A_{CP} = (4 ^{+4}_{-5} \pm 2)%$. We also perform an angular-moment analysis of the three channels, and determine that the $f_X(1500)$ state can be described well by the sum of the resonances $f_0(1500)$, $f_2^{\prime}(1525)$, and $f_0(1710)$.

We study the process $e^+e^-\to J/\psi\pi^{+}\pi^{-}$ with initial-state-radiation events produced at the PEP-II asymmetric-energy collider. The data were recorded with the BaBar detector at center-of-mass energies 10.58 and 10.54 GeV, and correspond to an integrated luminosity of 454 $\mathrm{fb^{-1}}$. We investigate the $J/\psi \pi^{+}\pi^{-}$ mass distribution in the region from 3.5 to 5.5 $\mathrm{GeV/c^{2}}$. Below 3.7 $\mathrm{GeV/c^{2}}$ the $\psi(2S)$ signal dominates, and above 4 $\mathrm{GeV/c^{2}}$ there is a significant peak due to the Y(4260). A fit to the data in the range 3.74 -- 5.50 $\mathrm{GeV/c^{2}}$ yields a mass value $4244 \pm 5$ (stat) $ \pm 4$ (syst)$\mathrm{MeV/c^{2}}$ and a width value $114 ^{+16}_{-15}$ (stat)$ \pm 7$(syst)$\mathrm{MeV}$ for this state. We do not confirm the report from the Belle collaboration of a broad structure at 4.01 $\mathrm{GeV/c^{2}}$. In addition, we investigate the $\pi^{+}\pi^{-}$ system which results from Y(4260) decay.

We present a search for the decay ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}\ensuremath{\nu}$ using $467.8\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs collected at the $\ensuremath{\Upsilon}(4S)$ resonance with the BABAR detector at the SLAC PEP-II $B$-Factory. We select a sample of events with one completely reconstructed ${B}^{\ensuremath{-}}$ in the hadronic decay mode (${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{(*)0}{X}^{\ensuremath{-}}$ and ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}J/\ensuremath{\psi}{X}^{\ensuremath{-}}$). We examine the rest of the event to search for a ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}\ensuremath{\nu}$ decay. We identify the ${\ensuremath{\tau}}^{+}$ lepton in the following modes: ${\ensuremath{\tau}}^{+}\ensuremath{\rightarrow}{e}^{+}\ensuremath{\nu}\overline{\ensuremath{\nu}}$, ${\ensuremath{\tau}}^{+}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}\ensuremath{\nu}\overline{\ensuremath{\nu}}$, ${\ensuremath{\tau}}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}\overline{\ensuremath{\nu}}$ and ${\ensuremath{\tau}}^{+}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{+}\overline{\ensuremath{\nu}}$. We find an excess of events with respect to the expected background, which excludes the null signal hypothesis at the level of $3.8\ensuremath{\sigma}$ (including systematic uncertainties) and corresponds to a branching fraction value of $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}\ensuremath{\nu})=({1.83}_{\ensuremath{-}0.49}^{+0.53}(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.24(\mathrm{syst}))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$.

We present a measurement of the Cabibbo-Kobayashi-Maskawa matrix element $|{V}_{\mathrm{cb}}|$ and the form-factor slope ${\ensuremath{\rho}}^{2}$ in $\overline{B}\ensuremath{\rightarrow}D{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}}$ decays based on $460\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ events recorded at the $\ensuremath{\Upsilon}(4S)$ resonance with the BABAR detector. $\overline{B}\ensuremath{\rightarrow}D{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}}$ decays are selected in events in which a hadronic decay of the second $B$ meson is fully reconstructed. We measure $\mathcal{B}({B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{0}{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})/\mathcal{B}({B}^{\ensuremath{-}}\ensuremath{\rightarrow}X{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})=(0.255\ifmmode\pm\else\textpm\fi{}0.009\ifmmode\pm\else\textpm\fi{}0.009)$ and $\mathcal{B}({\overline{B}}^{0}\ensuremath{\rightarrow}{D}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})/\mathcal{B}({\overline{B}}^{0}\ensuremath{\rightarrow}X{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})=(0.230\ifmmode\pm\else\textpm\fi{}0.011\ifmmode\pm\else\textpm\fi{}0.011)$, along with the differential decay distribution in $\overline{B}\ensuremath{\rightarrow}D{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}}$ decays. We then determine $\mathcal{G}(1)|{V}_{\mathrm{cb}}|=(42.3\ifmmode\pm\else\textpm\fi{}1.9\ifmmode\pm\else\textpm\fi{}1.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ and ${\ensuremath{\rho}}^{2}=1.20\ifmmode\pm\else\textpm\fi{}0.09\ifmmode\pm\else\textpm\fi{}0.04$, where $\mathcal{G}(1)$ is the hadronic form factor at the point of zero recoil.

We have performed a search for the eta_b(1S) meson in the radiative decay of the Upsilon(2S) resonance using a sample of 91.6 million Upsilon(2S) events recorded with the BABAR detector at the PEP-II B factory at the SLAC National Accelerator Laboratory. We observe a peak in the photon energy spectrum at E_gamma = 609.3 {+4.6} {-4.5} (stat) +/- 1.9 (syst) MeV, corresponding to an eta_b(1S) mass of 9394.2 {+4.8} {-4.9} (stat) +/- 2.0 (syst) MeV/c^2. The branching fraction for the decay Upsilon(2S) --> gamma eta_b(1S) is determined to be [3.9 +/-1.1 (stat) {+1.1} {-0.9} (syst)] x 10^(-4). We find the ratio of branching fractions B[Upsilon(2S) --> gamma eta_b(1S)]/B[Upsilon(3S) --> gamma eta_b(1S)] = 0.82 +/- 0.24 (stat) {+0.20}{-0.19} (syst).

We study the process $\gamma \gamma \to J/\psi \omega$ using a data sample of 519.2 $fb^{-1}$ recorded by the BaBar detector at SLAC at the PEP-II asymmetric-energy $e^+ e^-$ collider at center-of-mass energies near the $\Upsilon(nS)$ ($n = 2,3,4$) resonances. We confirm the existence of the charmonium-like resonance X(3915) decaying to $J/\psi \omega$ with a significance of 7.6 standard deviations, including systematic uncertainties, and measure its mass $(3919.4 \pm 2.2 \pm 1.6) MeV/c^2$ and width $(13 \pm 6 \pm 3) MeV$, where the first uncertainty is statistical and the second systematic. A spin-parity analysis supports the assignment $J^P=0^+$ and therefore the identification of the signal as due to the $\chi_{c0}(2P)$ resonance. In this hypothesis we determine the product between the two-photon width and the final state branching fraction to be $(52 \pm 10 \pm 3) eV$

Cross sections for the reactions e(+)e(-) -> K+K-pi(+)pi(-), K+K-pi(0)pi(0), and

Recent astrophysical and terrestrial experiments have motivated the proposal of a dark sector with GeV-scale gauge boson force carriers and new Higgs bosons. We present a search for a dark Higgs boson using 516 fb-1 of data collected with the BABAR detector. We do not observe a significant signal and we set 90% confidence level upper limits on the product of the Standard Model-dark sector mixing angle and the dark sector coupling constant.

We have searched for two-body charmless hadronic decays of $B$ mesons. Final states include $ππ$, $K π$, and $KK$ with both charged and neutral kaons and pions; $πρ$, $K ρ$, and $K^*π$; and $Kϕ$, $ K^*ϕ$, and $ϕϕ$. The data used in this analysis consist of 2.6~million $B\bar{B}$~pairs produced at the $Υ(4S)$ taken with the CLEO-II detector at the Cornell Electron Storage Ring (CESR). We measure the branching fraction of the sum of $B^0 \rightarrow π^+π^-$ and $B^0 \rightarrow K^+π^-$ to be $(1.8^{+0.6+0.2}_{-0.5-0.3}\pm0.2) \times 10^{-5}$. In addition, we place upper limits on individual branching fractions in the range from $10^{-4}$ to $10^{-6}$.

Using the CLEO II detector and a sample of 955 000 Υ(4S) decays we have confirmed charmless semileptonic decays of B mesons. In the momentum interval 2.3–2.6 GeV/c we observe an excess of 107±15±11 leptons, which we attribute to b→ulν. This result yields a model-dependent range of values for ‖Vub/Vcb‖ that is lower than has been obtained in previous studies. For the inclusive spectator model of Altarelli et al. we find ‖Vub/Vcb‖=0.076±0.008. Models that describe b→ulν with a limited set of exclusive final states give ‖Vub/Vcb‖=0.06-0.10.Received 7 September 1993DOI:https://doi.org/10.1103/PhysRevLett.71.4111©1993 American Physical Society

A search for charmonium and other new states is performed in a study of exclusive initial-state-radiation production of D¯¯¯D events from electron-positron annihilations at a center-of-mass energy of 10.58 GeV. The data sample corresponds to an integrated luminosity of 384 fb−1 and was recorded by the BABAR experiment at the PEP-II storage ring. The D¯¯¯D mass spectrum shows clear evidence of the ψ(3770) plus other structures near 3.9, 4.1, and 4.4 GeV/c2. No evidence for Y(4260)→D¯¯¯D is observed, leading to an upper limit of B(Y(4260)→D¯¯¯D)/B(Y(4260)→J/ψπ+π−)<1.0 at 90% confidence level.Received 6 October 2007DOI:https://doi.org/10.1103/PhysRevD.76.111105©2007 American Physical Society

We present a measurement of the branching fraction and photon-energy spectrum for the decay B→Xsγ using data from the BABAR experiment. The data sample corresponds to an integrated luminosity of 210 fb−1, from which approximately 680 000 B¯¯¯B events are tagged by a fully reconstructed hadronic decay of one of the B mesons. In the decay of the second B meson, an isolated high-energy photon is identified. We measure B(B→Xsγ)=(3.66±0.85stat±0.60syst)×10−4 for photon energies Eγ above 1.9 GeV in the B rest frame. From the measured spectrum we calculate the first and second moments for different minimum photon energies, which are used to extract the heavy-quark parameters mb and μ2π. In addition, measurements of the direct CP asymmetry and isospin asymmetry are presented.Received 29 November 2007DOI:https://doi.org/10.1103/PhysRevD.77.051103©2008 American Physical Society

We present a study of excited charm-strange baryon states produced in $e^+e^-$ annihilations at or near a center-of-mass energy of $10.58\mathrm{Ge\kern -0.1em V}$, in a data sample with an integrated luminosity of $384 fb^{-1}$ recorded with the BABAR detector at the PEP-II $e^+e^-$ storage rings at the Stanford Linear Accelerator Center. We study strong decays of charm-strange baryons to $\Lambda_c^+K^0_{\scriptscriptstyle S}$, $\Lambda_c^+K^-$, $\Lambda_c^+K^-\pi^+$, $\Lambda_c^+K^0_{\scriptscriptstyle S}\pi^-$, $\Lambda_c^+K^0_{\scriptscriptstyle S}\pi^-\pi^+$, and $\Lambda_c^+K^-\pi^+\pi^-$. This study confirms the existence of the states $\Xi_c(2980)^+$, $\Xi_c(3077)^+$, and $\Xi_c(3077)^0$, with a more accurate determination of the $\Xi_c(2980)^+$ mass and width. We also present evidence for two new states, $\Xi_c(3055)^+$ and $\Xi_c(3123)^+$, decaying through the intermediate resonant modes $\Sigma_c(2455)^{++}K^-$ and $\Sigma_c(2520)^{++}K^-$, respectively. For each of these baryons, we measure the yield in each final state, determine the statistical significance, and calculate the product of the production cross-section and branching fractions. We also measure the masses and widths of these excited charm-strange baryons.

We measure branching fractions and integrated rate asymmetries for the rare decays B→K(*)l+l−, where l+l− is either e+e− or μ+μ−, using a sample of 384×106 B¯¯¯B events collected with the BABAR detector at the PEP-II e+e− collider. We find no evidence for direct CP or lepton-flavor asymmetries. However, for dilepton masses below the J/ψ resonance, we find evidence for unexpectedly large isospin asymmetries in both B→Kl+l− and B→K∗l+l− which differ, respectively, by 3.2σ and 2.7σ, including systematic uncertainties, from the standard model expectations.Received 25 July 2008DOI:https://doi.org/10.1103/PhysRevLett.102.091803©2009 American Physical Society

A search for the Z(3930) resonance in gamma gamma production of the DDbar system has been performed using a data sample corresponding to an integrated luminosity of 384 fb^-1 recorded by the BABAR experiment at the PEP-II asymmetric-energy electron-positron collider. The DDbar invariant mass distribution shows clear evidence of the Z(3930) state with a significance of 5.8 sigma. We determine mass and width values of (3926.7 +- 2.7 +- 1.1) MeV/c^2 and (21.3 +- 6.8 +- 3.6) MeV, respectively. A decay angular analysis provides evidence that the Z(3930) is a tensor state with positive parity and C-parity (J^PC = 2^++); therefore we identify the Z(3930) state as the chi_c2(2P) meson. The value of the partial width Gamma_(gamma gamma)xB(Z(3930)-> DDbar) is found to be (0.24 +- 0.05 +- 0.04) keV.

The e+ e- --> p anti-p cross section and the proton magnetic form factor have been measured in the center-of-mass energy range from 3.0 to 6.5 GeV using the initial-state-radiation technique with an undetected photon. This is the first measurement of the form factor at energies higher than 4.5 GeV. The analysis is based on 469 fb-1 of integrated luminosity collected with the BABAR detector at the PEP-II collider at e+e- center-of-mass energies near 10.6 GeV. The branching fractions for the decays J/psi --> p anti-p and psi(2S) --> p anti-p have also been measured.

A search for the neutrinoless, lepton-flavor violating decay of the τ lepton into three charged leptons has been performed using an integrated luminosity of 468 fb−1 collected with the BABAR detector at the PEP-II collider. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (1.8–3.3)×10−8 at 90% confidence level.Received 24 February 2010DOI:https://doi.org/10.1103/PhysRevD.81.111101©2010 American Physical Society

We search for single-photon decays of the Υ(1S) resonance, Υ → γ + invisible, where the invisible state is either a particle of definite mass, such as a light Higgs boson A⁰, or a pair of dark matter particles, χχ. Both A⁰ and χ are assumed to have zero spin. We tag Υ(1S) decays with a dipion transition Υ(2S) → π⁺π⁻Υ(1S) and look for events with a single energetic photon and significant missing energy. We find no evidence for such processes in the mass range m(A⁰) ≤ 9.2 GeV and m(χ) ≤ 4.5 GeV in the sample of 98 × 10⁶ Υ(2S) decays collected with the BABAR detector and set stringent limits on new physics models that contain light dark matter states.

We study the rare B meson decays B{+-,0} --> J/\psi\ K^+ K^- K{+-,0}, B{+-,0} --> J/\psi\ \phi\ K{+-,0}, and search for B0 --> J/\psi\ \phi, using 469 million BBbar events collected at the Upsilon(4S) resonance with the BABAR detector at the PEP-II e+e- asymmetric-energy collider. We present new measurements of branching fractions and a study of the J/\psi\phi mass distribution in search of new charmonium-like states. In addition, we search for the decay B0 --> J/\psi\ \phi, and find no evidence of a signal.

We study the lepton forward-backward asymmetry AFB and the longitudinal K* polarization FL, as well as an observable P2 derived from them, in the rare decays B->K*l+l-, where l+l- is either e+e- or mu+mu-, using the full sample of 471 million BBbar events collected at the Upsilon(4S) resonance with the Babar detector at the PEP-II e+e- collider. We separately fit and report results for the B+->K*+l+l- and B0->K*0l+l- final states, as well as their combination B->K*l+l-, in five disjoint dilepton mass-squared bins. An angular analysis of B+->K*+l+l- decays is presented here for the first time.

Using a sample of $2.6\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $\ensuremath{\Upsilon}(4\mathrm{S})\ensuremath{\rightarrow}B\overline{B}$ events collected with the CLEO II detector at the Cornell Electron Storage Ring, we have measured the form factors for ${\overline{B}}^{0}\ensuremath{\rightarrow}{D}^{*+}{\ensuremath{\ell}}^{\ensuremath{-}}\overline{\ensuremath{\nu}}$. We perform a three-parameter fit with the joint distribution of four kinematic variables to obtain the form-factor ratios ${R}_{1}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.18\ifmmode\pm\else\textpm\fi{}0.30\ifmmode\pm\else\textpm\fi{}0.12$ and ${R}_{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.71\ifmmode\pm\else\textpm\fi{}0.22\ifmmode\pm\else\textpm\fi{}0.07,$ and the form-factor slope ${\ensuremath{\rho}}_{{A}_{1}}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.91\ifmmode\pm\else\textpm\fi{}0.15\ifmmode\pm\else\textpm\fi{}0.06,$ which is closely related to the slope of the Isgur-Wise function. The form-factor ratios are consistent with predicted corrections to the heavy-quark symmetry limit ${R}_{1}{\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}R}_{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$.

We have measured the B0B¯0 mixing probability, χd, using a sample of 965 000 BB¯ pairs from Υ(4S) decays. Counting dilepton events, we find χd=0.157±0.016±0.018−0.021+0.028. Using tagged B0 events, we find χd=0.149±0.023±0.019±0.010. The first (second) error is statistical (systematic). The third error reflects a ±15% uncertainty in the assumption, made in both cases, that charged and neutral B pairs contribute equally to dilepton events. We also obtain a limit on the CP impurity in the Bd0 system, ‖Re(εB0)‖<0.045 at 90% C.L.Received 29 April 1993DOI:https://doi.org/10.1103/PhysRevLett.71.1680©1993 American Physical Society

We present measurements of spectral moments extracted from the invariant mass distributions of the final states of hadronic τ decay products recorded in the CLEO detector. From a fit of theoretical predictions to the measurements of spectral moments and the total hadronic decay width of the τ, we determine the strong coupling constant and a set of non-perturbative QCD parameters. The strong coupling constant is measured to be αs(mτ) = 0.306 ± 0.024, which when extrapolated to the Z mass, yields αs(Mz) = 0.114 ± 0.003.

The shape of the hadronic form factor f+(q2) in the decay D0 --> K- e+ nue has been measured in a model independent analysis and compared with theoretical calculations. We use 75 fb(-1) of data recorded by the BABAR detector at the PEPII electron-positron collider. The corresponding decay branching fraction, relative to the decay D0 --> K- pi+, has also been measured to be RD = BR(D0 --> K- e+ nue)/BR(D0 --> K- pi+) = 0.927 +/- 0.007 +/- 0.012. From these results, and using the present world average value for BR(D0 --> K- pi+), the normalization of the form factor at q2=0 is determined to be f+(0)=0.727 +/- 0.007 +/- 0.005 +/- 0.007 where the uncertainties are statistical, systematic, and from external inputs, respectively.

We present a combined measurement of the Cabibbo-Kobayashi-Maskawa matrix element $|{V}_{cb}|$ and of the parameters ${\ensuremath{\rho}}^{2}$, ${R}_{1}(1)$, and ${R}_{2}(1)$, which fully characterize the form factors for the ${B}^{0}\ensuremath{\rightarrow}{D}^{*\ensuremath{-}}{\ensuremath{\ell}}^{+}{\ensuremath{\nu}}_{\ensuremath{\ell}}$ decay in the framework of heavy-quark effective field theory. The results, based on a selected sample of about 52 800 ${B}^{0}\ensuremath{\rightarrow}{D}^{*\ensuremath{-}}{\ensuremath{\ell}}^{+}{\ensuremath{\nu}}_{\ensuremath{\ell}}$ decays, recorded by the BABAR detector, are ${\ensuremath{\rho}}^{2}=1.157\ifmmode\pm\else\textpm\fi{}0.094\ifmmode\pm\else\textpm\fi{}0.027$, ${R}_{1}(1)=1.327\ifmmode\pm\else\textpm\fi{}0.131\ifmmode\pm\else\textpm\fi{}0.043$, ${R}_{2}(1)=0.859\ifmmode\pm\else\textpm\fi{}0.077\ifmmode\pm\else\textpm\fi{}0.021$, and $\mathcal{F}(1)|{V}_{cb}|=(34.7\ifmmode\pm\else\textpm\fi{}0.4\ifmmode\pm\else\textpm\fi{}1.0)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$. The first error is the statistical and the second is the systematic uncertainty. Combining these measurements with the previous BABAR measurement of the form factors, which employs a different fit technique on a partial sample of the data, we improve the statistical precision of the result, ${\ensuremath{\rho}}^{2}=1.191\ifmmode\pm\else\textpm\fi{}0.048\ifmmode\pm\else\textpm\fi{}0.028$, ${R}_{1}(1)=1.429\ifmmode\pm\else\textpm\fi{}0.061\ifmmode\pm\else\textpm\fi{}0.044$, ${R}_{2}(1)=0.827\ifmmode\pm\else\textpm\fi{}0.038\ifmmode\pm\else\textpm\fi{}0.022$, and $\mathcal{F}(1)|{V}_{cb}|=(34.4\ifmmode\pm\else\textpm\fi{}0.3\ifmmode\pm\else\textpm\fi{}1.1)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$. Using lattice calculations for the axial form factor $\mathcal{F}(1)$, we extract $|{V}_{cb}|=(37.4\ifmmode\pm\else\textpm\fi{}0.3\ifmmode\pm\else\textpm\fi{}1.2{\ifmmode\pm\else\textpm\fi{}}_{1.4}^{1.2})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$, where the third error is due to the uncertainty in $\mathcal{F}(1)$. We also present a measurement of the exclusive branching fraction, $\mathcal{B}=(4.69\ifmmode\pm\else\textpm\fi{}0.04\ifmmode\pm\else\textpm\fi{}0.34)%$.

Using 467 $fb^{-1}$ of $e^+e^-$ annihilation data collected with the BaBar detector, we measure $\frac{{\cal{B}}(\tau^- \to \mu^- \bar{\nu}_\mu \nu_\tau)}{{\cal{B}}(\tau^- \to e^- \bar{\nu}_e \nu_\tau)} = (0.9796 \pm 0.0016 \pm 0.0036)$, $\frac{{\cal{B}}(\tau^- \to \pi^- \nu_\tau)}{{\cal{B}}(\tau^- \to e^- \bar{\nu}_e \nu_\tau)} = (0.5945 \pm 0.0014 \pm 0.0061)$, and $\frac{{\cal{B}}(\tau^- \to \K^- \nu_\tau)}{{\cal{B}}(\tau^- \to e^- \bar{\nu}_e \nu_\tau)} = (0.03882 \pm 0.00032 \pm 0.00057)$, where the uncertainties are statistical and systematic, respectively. From these precision $\tau$ measurements, we test the Standard Model assumption of $\mu$-$e$ and $\tau$-$\mu$ charge current lepton universality and provide determinations of $|V_{us}|$ experimentally independent of the decay of a kaon and which we compare with the value predicted from the unitarity of the Cabibbo-Kobayashi-Maskawa matrix.

We present searches for rare or forbidden charm decays of the form $X_c^+\to h^\pm\ell^\mp\ell^{(\prime)+}$, where $X_c^+$ is a charm hadron ($D^+$, $D^+_s$, or $\Lambda_c^+$), $h^\pm$ is a pion, kaon, or proton, and $\ell^{(\prime)\pm}$ is an electron or muon. The analysis is based on $384 fb^{-1}$ of $e^+e^-$ annihilation data collected at or close to the $\Upsilon(4S)$ resonance with the BaBar detector at the SLAC National Accelerator Laboratory. No significant signal is observed for any of the 35 decay modes that are investigated. We establish 90% confidence-level upper limits on the branching fractions between $1 \times 10^{-6}$ and $44 \times 10^{-6}$ depending on the channel. In most cases, these results represent either the first limits or significant improvements on existing limits for the decay modes studied.

We present a measurement of ${D}^{0}\mathrm{\text{\ensuremath{-}}}{\overline{D}}^{0}$ mixing and $CP$ violation using the ratio of lifetimes simultaneously extracted from a sample of ${D}^{0}$ mesons produced through the flavor-tagged process ${D}^{*+}\ensuremath{\rightarrow}{D}^{0}{\ensuremath{\pi}}^{+}$, where ${D}^{0}$ decays to ${K}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$, ${K}^{\ensuremath{-}}{K}^{+}$, or ${\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$, along with the untagged decays ${D}^{0}\ensuremath{\rightarrow}{K}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ and ${D}^{0}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{K}^{+}$. The lifetimes of the $CP$-even, Cabibbo-suppressed modes ${K}^{\ensuremath{-}}{K}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ are compared to that of the $CP$-mixed mode ${K}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ in order to measure ${y}_{CP}$ and $\ensuremath{\Delta}Y$. We obtain ${y}_{CP}=[0.72\ifmmode\pm\else\textpm\fi{}0.18(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.12(\mathrm{syst})]%$ and $\ensuremath{\Delta}Y=[0.09\ifmmode\pm\else\textpm\fi{}0.26(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.06(\mathrm{syst})]%$, where $\ensuremath{\Delta}Y$ constrains possible $CP$ violation. The ${y}_{CP}$ result excludes the null mixing hypothesis at $3.3\ensuremath{\sigma}$ significance. This analysis is based on an integrated luminosity of $468\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected with the BABAR detector at the PEP-II asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider.

Based on a sample of 500 million ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}c\overline{c}$ events recorded by the BABAR detector at c.m. energies of close to 10.6 GeV, we report on a study of the decay ${D}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{e}^{+}{\ensuremath{\nu}}_{e}$. We measure the ratio of branching fractions, ${R}_{D}=\mathcal{B}({D}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{e}^{+}{\ensuremath{\nu}}_{e})/\mathcal{B}({D}^{0}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})=0.0713\ifmmode\pm\else\textpm\fi{}0.001{7}_{\text{stat}}\ifmmode\pm\else\textpm\fi{}0.002{4}_{\text{syst}}$, and use the present world average for $\mathcal{B}({D}^{0}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})$ to obtain $\mathcal{B}({D}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{e}^{+}{\ensuremath{\nu}}_{e})=(2.770\ifmmode\pm\else\textpm\fi{}0.06{8}_{\text{stat}}\ifmmode\pm\else\textpm\fi{}0.09{2}_{\text{syst}}\ifmmode\pm\else\textpm\fi{}0.03{7}_{\text{ext}})\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}3}$ where the third error accounts for the uncertainty on the branching fraction for the reference channel. The measured dependence of the differential branching fraction on ${q}^{2}$, the four-momentum transfer squared between the $D$ and the $\ensuremath{\pi}$ meson, is compared to various theoretical predictions for the hadronic form factor, ${f}_{+,D}^{\ensuremath{\pi}}({q}^{2})$, and the normalization $|{V}_{cd}|\ifmmode\times\else\texttimes\fi{}{f}_{+,D}^{\ensuremath{\pi}}({q}^{2}=0)=0.1374\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0ex}{0ex}}0.003{8}_{\text{stat}}\ifmmode\pm\else\textpm\fi{}0.002{2}_{\text{syst}}\ifmmode\pm\else\textpm\fi{}0.000{9}_{\text{ext}}$. is extracted from a fit to data. Using the most recent LQCD prediction of ${f}_{+,D}^{\ensuremath{\pi}}({q}^{2}=0)=0.666\ifmmode\pm\else\textpm\fi{}0.029$, we obtain $|{V}_{cd}|=0.206\ifmmode\pm\else\textpm\fi{}0.00{7}_{\text{exp}}\ifmmode\pm\else\textpm\fi{}0.00{9}_{\mathrm{LQCD}}$. Assuming, instead, $|{V}_{cd}|=|{V}_{us}|=0.2252\ifmmode\pm\else\textpm\fi{}0.0009$, we obtain ${f}_{+,D}^{\ensuremath{\pi}}({q}^{2}=0)=0.610\ifmmode\pm\else\textpm\fi{}0.02{0}_{\text{exp}}\ifmmode\pm\else\textpm\fi{}0.00{5}_{\text{ext}}$. The ${q}^{2}$ dependence of ${f}_{+,D}^{\ensuremath{\pi}}({q}^{2})$ is compared to a variety of multipole parametrizations. This information is applied to ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{e}^{+}{\ensuremath{\nu}}_{e}$ decays and, combined with an earlier ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{e}^{+}{\ensuremath{\nu}}_{e}$ measurement by BABAR, is used to derive estimates of $|{V}_{ub}|$.

We present results from an analysis of B0 to rho+rho- decays using 383.6 million BB-bar pairs collected by the BaBar detector at the PEP-II asymmetric-energy B Factory at SLAC. The measurements of the B0 to rho+rho- branching fraction, longitudinal polarization fraction f_L, and the CP-violating parameters S_{long} and C_{long} are: B(B0-> rho+rho-) = (25.5 +/- 2.1 (stat) +3.6/-3.9 (syst))*10^-6 f_L = 0.992 +/- 0.024 (stat) +0.026/-0.013 (syst) S_{long} = -0.17 +/- 0.20 (stat) +0.05/-0.06 (syst) C_{long} = 0.01 +/- 0.15 (stat) +/- 0.06 (syst) We determine the unitarity triangle angle alpha, using an isospin analysis of B to rhorho decays. One of the two solutions, alpha = [73.1, 117.0] degrees at 68% CL is compatible with standard model-based fits of existing data. Constraints on the unitarity triangle are also evaluated using an SU(3) symmetry based approach.

We present updated measurements of the branching fractions and CP asymmetries for B0→π0π0, B±→π±π0, and B±→K±π0. Based on a sample of 383×106 Υ(4S)→B¯¯¯B decays collected by the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC, we measure B(B0→π0π0)=(1.47±0.25±0.12)×10−6, B(B±→π±π0)=(5.02±0.46±0.29)×10−6, and B(B±→K±π0)=(13.6±0.6±0.7)×10−6. We also measure the CP asymmetries Cπ0π0=−0.49±0.35±0.05, Aπ±π0=0.03±0.08±0.01, and AK±π0=0.030±0.039±0.010. Finally, we present bounds on the Cabibbo-Kobayashi-Maskawa angle α using isospin relations.Received 18 July 2007DOI:https://doi.org/10.1103/PhysRevD.76.091102©2007 American Physical Society

We perform a time-dependent amplitude analysis of $B^0 \to K^0_S\pi^+\pi^-$ decays to extract the CP violation parameters of $f_0(980) K^0_S$ and $\rho^0(770) K^0_S$ and the direct CP asymmetry of $K^{*+}(892) \pi^-$. The results are obtained from a data sample of $(383 \pm 3) \times 10^6$ $B\bar{B}$ decays, collected with the BABAR detector at the PEP-II asymmetric-energy $B$ factory at SLAC. We find two solutions, with an equivalent goodness-of-fit. Including systematic and Dalitz plot model uncertainties, the combined confidence interval for values of the CP parameter $\beta_{eff}$ in $B^0$ decays to $f_0(980) K^0_S$ is $18^o < \beta_{eff} < 76^o$ at 95% confidence level (C.L). CP conservation in $B^0$ decays to $f_0(980) K^0_S$ is excluded at $3.5\sigma$ including systematic uncertainties. For $B^0$ decays to $\rho^0(770) K^0_S$, the combined confidence interval is $-9^o < \beta_{eff} < 57^o$ at 95% C.L. In decays to $K^{*+}(892) \pi^-$ we measure the direct CP asymmetry to be $A_{CP}=-0.20 \pm 0.10 \pm 0.01 \pm 0.02$. The measured phase difference (including $B^0\bar{B}^0$ mixing) between decay amplitudes of $B^0 \to K^{*+}(892) \pi^-$ and $\bar{B}^0 \to K^{*-}(892) \pi^+$, excludes the interval $-137^o < \Delta\Phi(K^{*+}(892) \pi^-) < -5^o$ at 95% C.L.

We search for invisible decays of the Υ(1S) meson using a sample of 91.4×106 Υ(3S) mesons collected at the BABAR/PEP-II B factory. We select events containing the decay Υ(3S)→π+π−Υ(1S) and search for evidence of an undetectable Υ(1S) decay recoiling against the dipion system. We set an upper limit on the branching fraction B(Υ(1S)→invisible)<3.0×10−4 at the 90% confidence level.Received 20 August 2009DOI:https://doi.org/10.1103/PhysRevLett.103.251801©2009 American Physical Society

A Dalitz plot analysis of approximately 13 000 D+s decays to π+π−π+ has been performed. The analysis uses a 384 fb−1 data sample recorded by the BABAR detector at the PEP-II asymmetric-energy e+e− storage ring running at center of mass energies near 10.6 GeV. Amplitudes and phases of the intermediate resonances which contribute to this final state are measured. A high precision measurement of the ratio of branching fractions is performed: B(D+s→π+π−π+)/B(D+s→K+K−π+)=0.199±0.004±0.009. Using a model-independent partial wave analysis, the amplitude and phase of the S wave have been measured.Received 9 December 2008DOI:https://doi.org/10.1103/PhysRevD.79.032003©2009 American Physical Society

We measure the rate of D0−¯¯¯D0 mixing with the observable yCP=(τKπ/τKK)−1, where τKK and τKπ are, respectively, the mean lifetimes of CP-even D0→K+K− and CP-mixed D0→K−π+ decays, using a data sample of 384 fb−1 collected by the BABAR detector at the SLAC PEP-II asymmetric-energy B Factory. From a sample of D0 and ¯¯¯D0 decays where the initial flavor of the decaying meson is not determined, we obtain yCP=[1.12±0.26(stat)±0.22(syst)]%, which excludes the no-mixing hypothesis at 3.3σ, including both statistical and systematic uncertainties. This result is in good agreement with a previous BABAR measurement of yCP obtained from a sample of D*+→D0π+ events, where the D0 decays to K−π+, K+K−, and π+π−, which is disjoint with the untagged D0 events used here. Combining the two results taking into account statistical and systematic uncertainties, where the systematic uncertainties are assumed to be 100% correlated, we find yCP=[1.16±0.22(stat)±0.18(syst)]%, which excludes the no-mixing hypothesis at 4.1σ.Received 7 August 2009DOI:https://doi.org/10.1103/PhysRevD.80.071103©2009 American Physical Society

We present evidence of D0−¯¯¯D0 mixing using a time-dependent amplitude analysis of the decay D0→K+π−π0 in a data sample of 384 fb−1 collected with the BABAR detector at the PEP-II e+e− collider at the Stanford Linear Accelerator Center. Assuming CP conservation, we measure the mixing parameters x′Kππ0=[2.61+0.57−0.68(stat)±0.39(syst)]%, y′Kππ0=[−0.06+0.55−0.64(stat)±0.34(syst)]%. This result is inconsistent with the no-mixing hypothesis with a significance of 3.2 standard deviations. We find no evidence of CP violation in mixing.Received 28 July 2008DOI:https://doi.org/10.1103/PhysRevLett.103.211801©2009 American Physical Society

We study the reaction e+e- --> e+e- eta_c, eta_c --> K_S K+- pi-+ and obtain eta_c mass and width values 2982.2+-0.4+-1.6 MeV/c^2 and 31.7+-1.2+-0.8 MeV, respectively. We find Gamma(eta_c --> gamma gamma)B(eta_c --> K anti-K pi)=0.374+-0.009+-0.031 keV, and measure the gamma gamma* --> eta_c transition form factor in the momentum transfer range from 2 to 50 GeV^2. The analysis is based on 469 fb-1 of integrated luminosity collected at PEP-II with the BABAR detector at e+e- center-of-mass energies near 10.6 GeV.

We report on analyses of tau lepton decays $\tau^- \to \eta K^- \nu_{\tau}$ and $\tau^- \to \eta \pi^- \nu_{\tau}$, with $\eta \to \pi^+ \pi^- \pi^0$, using 470 fb$^{-1}$ of data from the Babar experiment at PEP-II, collected at center-of-mass energies at and near the $\Upsilon(4S)$ resonance. We measure the branching fraction for the $\tau^- \to \eta K^- \nu_{\tau}$ decay mode, $\Br(\tau^- \to \eta K^- \nu_{\tau}) = (1.42\pm0.11\text{(stat)}\pm0.07\text{(syst)})\times10^{-4}$, and report a 95% confidence level upper limit for the second-class current process $\tau^- \to \eta \pi^- \nu_{\tau}$, $\Br(\tau^- \to \eta \pi^- \nu_{\tau}) < 9.9\times10^{-5}$.

We report a search for CP violation in the decay \tau- -> \pi - \K^0_S (>= 0 \pi 0) \nu_\tau\ using a dataset of 437 million \tau\ lepton pairs, corresponding to an integrated luminosity of 476 fb^{-1}, collected with the BABAR detector at the PEP-II asymmetric energy e+e- storage rings. The CP-violating decay-rate asymmetry is determined to be (-0.45 +/- 0.24 +/- 0.11)%, approximately three standard deviations from the Standard Model prediction of (0.33 +/- 0.01)%.

Measurement of the B(0) -> pi(-)l(+)nu and B(+) -> eta(l)l(+)nu branching fractions, the B(0) -> pi(-)l(+)nu and B(+) -> eta l(+

Using 347.5 fb-1 of data recorded by the BABAR detector at the PEP-II electron-positron collider, 244*10^3 signal events for the D+ --> K- pi+ e+ nu_e decay channel are analyzed. This decay mode is dominated by the \bar{K}^*(892)^0 contribution. We determine the \bar{K}^*(892)^0 parameters: m_{K^*(892)^0}=(895.4 +- 0.2 +- 0.2) MeV/c^{2}, \Gamma^0_{K^*(892)^0}=(46.5 +- 0.3 +- 0.2) MeV/c^{2} and the Blatt-Weisskopf parameter $r_{BW}=2.1 +- 0.5 +- 0.5 (GeV/c)^{-1} where the first uncertainty comes from statistics and the second from systematic uncertainties. We also measure the parameters defining the corresponding hadronic form factors at q^{2}=0 (r_{V} = V(0) / A_{1}(0)=1.463 +- 0.017 +- 0.031, r_{2} = A_{2}(0) / A_{1}(0) = 0.801 +- 0.020 +- 0.020) and the value of the axial-vector pole mass parameterizing the q^2 variation of A_{1} and A_{2}: m_{A}=(2.63 +- 0.10 +- 0.13) GeV/c^{2}. The S-wave fraction is equal to (5.79 +- 0.16 +- 0.15)%. Other signal components correspond to fractions below 1%. Using the D+ --> K- pi+ pi+ channel as a normalization, we measure the D+ semileptonic branching fraction: BR(D+ --> K- pi+ e+ nu_e) = (4.04 +- 0.03 +- 0.04 +- 0.09) \times 10^{-2} where the third uncertainty comes from external inputs. We then obtain the value of the hadronic form factor A_1 at q^{2}=0: A_{1}(0) = 0.6226 +- 0.0056 +- 0.0065 +- 0.0074. Fixing the P-wave parameters we measure the phase of the S-wave for several values of the Kpi mass. These results confirm those obtained with Kpi production at small momentum transfer in fixed target experiments.

We analyze the decay B0--&gt;K+ pi- pi0 with a sample of 454 million B Bbar events collected by the BaBar detector at the PEP-II asymmetric-energy B factory at SLAC, and extract the complex amplitudes of seven interfering resonances over the Dalitz plot. These results are combined with amplitudes measured in B0--&gt;K_S pi+ pi- decays to construct isospin amplitudes from B0--&gt;K* pi and B0--&gt;rho K decays. We measure the phase of the isospin amplitude Phi_3/2, useful in constraining the CKM unitarity triangle angle gamma and evaluate a CP rate asymmetry sum rule sensitive to the presence of new physics operators. We measure direct CP violation in B0--&gt;K*+ pi- decays at the level of 3 sigma when measurements from both B0--&gt;K+ pi- pi0 and B0--&gt;K_S pi+ pi- decays are combined.

We search for a low-mass scalar CP-odd Higgs boson, A0, produced in the radiative decay of the Upsilon resonance and decaying into a tau+tau- pair: Upsilon(1S)->gamma A0. The production of Upsilon(1S) mesons is tagged by Upsilon(2S)->pi+pi-Upsilon(1S) transitions, using a sample of (98.3+/-0.9) million Upsilon(2S) mesons collected by the BaBar detector. We find no evidence for a Higgs boson in the mass range 3.5 GeV<= m(A0)<=9.2 GeV, and combine these results with our previous search for the tau decays of the light Higgs in radiative Upsilon(3S) decays, setting limits on the coupling of A0 to the b/bbar quarks in the range 0.09-1.9. Our measurements improve the constraints on the parameters of the Next-to-Minimal-Supersymmetric Standard Model and similar theories with low-mass scalar degrees of freedom.

We present Dalitz plot analyses for the decays of $B$ mesons to ${D}^{\ensuremath{-}}{D}^{0}{K}^{+}$ and ${\overline{D}}^{0}{D}^{0}{K}^{+}$. We report the observation of the ${D}_{s1}^{*}(2700{)}^{+}$ resonance in these two channels and obtain measurements of the mass $M({D}_{s1}^{*}(2700{)}^{+})={2699}_{\ensuremath{-}7}^{+14}\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and of the width $\mathrm{\ensuremath{\Gamma}}({D}_{s1}^{*}(2700{)}^{+})={127}_{\ensuremath{-}19}^{+24}\text{ }\text{ }\mathrm{MeV}$, including statistical and systematic uncertainties. In addition, we observe an enhancement in the ${D}^{0}{K}^{+}$ invariant mass around $2350--2500\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ in both decays ${B}^{0}\ensuremath{\rightarrow}{D}^{\ensuremath{-}}{D}^{0}{K}^{+}$ and ${B}^{+}\ensuremath{\rightarrow}{\overline{D}}^{0}{D}^{0}{K}^{+}$, which we are not able to interpret. The results are based on $429\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data containing $471\ifmmode\times\else\texttimes\fi{}1{0}^{6}B\overline{B}$ pairs collected at the $\mathrm{\ensuremath{\Upsilon}}(4S)$ resonance with the BABAR detector at the SLAC National Accelerator Laboratory.

We report on a search for eleven lepton-number violating processes B+ -> X- l+ l'+ with X- = K-, pi-, rho-, K*- or D- and l+/l'+ = e+ or mu+, using a sample of 471+/-3 million BBbar events collected with the BaBar detector at the PEP-II e+e- collider at the SLAC National Accelerator Laboratory. We find no evidence for any of these modes and place 90% confidence level upper limits on their branching fractions in the range $(1.5-26)\times 10^{-7}$.

We report results from a search for the decays ${\mathit{B}}^{0}$\ensuremath{\rightarrow}${\mathrm{\ensuremath{\pi}}}^{+}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$, ${\mathit{B}}^{0}$\ensuremath{\rightarrow}${\mathit{K}}^{+}$${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$, and ${\mathit{B}}^{0}$\ensuremath{\rightarrow}${\mathit{K}}^{+}$${\mathit{K}}^{\mathrm{\ensuremath{-}}}$. We find 90% confidence level upper limits on the branching fractions, ${\mathit{B}}_{\mathrm{\ensuremath{\pi}}\mathrm{\ensuremath{\pi}}}$2.9\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$, ${\mathit{B}}_{\mathit{K}\mathrm{\ensuremath{\pi}}}$2.6\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$, and ${\mathit{B}}_{\mathit{K}\mathit{K}}$0.7\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$. While there is no statistically significant signal in the individual modes, the sum of ${\mathit{B}}_{\mathrm{\ensuremath{\pi}}\mathrm{\ensuremath{\pi}}}$ and ${\mathit{B}}_{\mathit{K}\mathrm{\ensuremath{\pi}}}$ exceeds zero with a significance of more than 4 standard deviations, indicating that we have observed charmless hadronic B decays.

A search for the neutrinoless, lepton-flavor violating decay of the tau lepton into three charged leptons has been performed using 376 fb−1 of data collected at an e+e− center-of-mass energy around 10.58 GeV with the BABAR detector at the SLAC PEP-II storage rings. In all six decay modes considered, the numbers of events found in data are compatible with the background expectations. Upper limits on the branching fractions are set in the range (4–8)×10−8 at 90% confidence level.Received 27 August 2007DOI:https://doi.org/10.1103/PhysRevLett.99.251803©2007 American Physical Society

We perform the first three-dimensional measurement of the amplitudes of B→ψ(2S)K* and B→χc1K* decays and update our previous measurement for B→J/ψK*. We use a data sample collected with the BABAR detector at the PEP-II storage ring, corresponding to 232×106 BB¯ pairs. The longitudinal polarization of decays involving a JPC=1++ χc1 meson is found to be larger than that with a 1-- J/ψ or ψ(2S) meson. No direct CP-violating charge asymmetry is observed.Received 5 April 2007DOI:https://doi.org/10.1103/PhysRevD.76.031102©2007 American Physical Society

We report searches for $B$-meson decays to the charmless final states $\ensuremath{\rho}{K}^{*}$ and ${f}_{0}(980){K}^{*}$ with a sample of $232\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs collected with the BABAR detector at the PEP-II ${e}^{+}{e}^{\ensuremath{-}}$ collider. We measure in units of ${10}^{\ensuremath{-}6}$ the following branching fractions, where the first error quoted is statistical and the second systematic, or upper limits are given at the 90% confidence level : $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}{K}^{*+})&lt;6.1$, $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{+}{K}^{*0})=9.6\ifmmode\pm\else\textpm\fi{}1.7\ifmmode\pm\else\textpm\fi{}1.5$, $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{\ensuremath{-}}{K}^{*+})&lt;12.0$, $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}{K}^{*0})=5.6\ifmmode\pm\else\textpm\fi{}0.9\ifmmode\pm\else\textpm\fi{}1.3$, $\mathcal{B}\mathbf{(}{B}^{+}\ensuremath{\rightarrow}{f}_{0}(980){K}^{*+}\mathbf{)}=5.2\ifmmode\pm\else\textpm\fi{}1.2\ifmmode\pm\else\textpm\fi{}0.5$, and $\mathcal{B}\mathbf{(}{B}^{0}\ensuremath{\rightarrow}{f}_{0}(980){K}^{*0}\mathbf{)}&lt;4.3$. For the significant modes, we also measure the fraction of longitudinal polarization and the charge asymmetry: ${f}_{L}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{+}{K}^{*0})=0.52\ifmmode\pm\else\textpm\fi{}0.10\ifmmode\pm\else\textpm\fi{}0.04$, ${f}_{L}({B}^{0}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}{K}^{*0})=0.57\ifmmode\pm\else\textpm\fi{}0.09\ifmmode\pm\else\textpm\fi{}0.08$, ${\mathcal{A}}_{CP}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{+}{K}^{*0})=\ensuremath{-}0.01\ifmmode\pm\else\textpm\fi{}0.16\ifmmode\pm\else\textpm\fi{}0.02$, ${\mathcal{A}}_{CP}({B}^{0}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}{K}^{*0})=0.09\ifmmode\pm\else\textpm\fi{}0.19\ifmmode\pm\else\textpm\fi{}0.02$, and ${\mathcal{A}}_{CP}\mathbf{(}{B}^{+}\ensuremath{\rightarrow}{f}_{0}(980){K}^{*+}\mathbf{)}=\ensuremath{-}0.34\ifmmode\pm\else\textpm\fi{}0.21\ifmmode\pm\else\textpm\fi{}0.03$.

We report on our search for decays proceeding via a tree-level b-->c quark transition in which a gluon radiates into an ss[over ] pair. We present observations of the decays B;{-}-->D_{s};{+}K;{-}pi;{-} and B[over ];{0}-->D_{s};{+}K_{S};{0}pi;{-} and evidence for B;{-}-->D_{s};{+}K;{-}K;{-} and set upper limits on the branching fractions for B[over ];{0}-->D_{s};{+}K_{S};{0}pi;{-} and B;{-}-->D_{s};{+}K;{-}K;{-} using 383x10;{6} Upsilon(4S)-->BB[over ] events collected by the BABAR detector at SLAC. We present evidence that the invariant mass distributions of D_{s};{+}K;{-} pairs from B;{-}-->D_{s};{+}K;{-}pi;{-} decays are inconsistent with the phase-space model, suggesting the presence of charm resonances lying below the D_{s};{+}K;{-} threshold.

We present results for the moments of observed spectra in inclusive semileptonic B-meson decays to charm hadrons Bbar --> X_c l- nubar. Moments of the hadronic-mass and the combined mass-and-energy spectra for different minimum electron or muon momenta between 0.8 and 1.9 GeV/c are obtained from a sample of 232x10^{6} Y(4S) --> B Bbar events, collected with the BABAR detector at the PEP-II asymmetric-energy B-meson factory at SLAC. We also present a re-evaluation of the moments of electron-energy spectra and partial decay fractions BR(Bbar --> X_c e- nubar for minimum electron momenta between 0.6 and 1.5 GeV/c based on a sample of 51x10^{6} Y(4S) --> B Bbar events. The measurements are used for the extraction of the total decay fraction, the Cabibbo-Kobayashi-Maskawa (CKM) matrix element |V_cb|, the quark masses m_b and m_c, and four heavy-quark QCD parameters in the framework of a Heavy Quark Expansion (HQE). We find BR(Bbar --> X_c l- nubar) = (10.64 +/- 0.17 +/- 0.06)% and |V_cb| = (42.05 +/- 0.45 +/- 0.70) x 10^{-3}.

Using the entire sample of 467 million Y(4S) --> BBbar decays collected with the BaBar detector at the PEP-II asymmetric-energy B factory at SLAC, we perform a "GLW" analysis of B+- --> D K+- decays, using decay modes in which the neutral D meson decays to either CP-eigenstates or non-CP-eigenstates. We measure the partial decay rate charge asymmetries for CP-even and CP-odd D final states to be A_CP+ = 0.25+-0.06+-0.02 and A_CP- = -0.09+-0.07+-0.02, respectively, where the first error is the statistical and the second is the systematic uncertainty. The parameter A_CP+ is different from zero with a significance of 3.6 standard deviations, constituting evidence for direct CP violation. We also measure the ratios of the charged-averaged B partial decay rates in CP and non-CP decays, R_CP+ = 1.18+-0.09+-0.05 and R_CP- = 1.07+-0.08+-0.04. We infer frequentist confidence intervals for the angle gamma of the (db) unitarity triangle, for the strong phase difference delta_B, and for the amplitude ratio r_B, which are related to the B- --> DK- decay amplitude by r_Be^{i(delta_B-gamma)} = A(B- --> anti-D0 K^-)/A(B- --> D0 K-). Including statistical and systematic uncertainties, we obtain 0.24<r_B<0.45 (0.06<r_B<0.51) and, modulo 180 degrees, 11.3 degrees < gamma < 22.7 degrees or 80.9 degrees < gamma < 99.1 degrees or 157.3 degrees < gamma < 168.7 degrees (7.0 degrees < gamma < 173.0 degrees) at the 68% (95%) confidence level.

We search for CP violation in a sample of 4.7×104 Cabibbo suppressed D0→K+K−π+π− decays. We use 470 fb−1 of data recorded by the BABAR detector at the PEP-II asymmetric-energy e+e− storage rings running at center-of-mass energies near 10.6 GeV. CP violation is searched for in the difference between the T-odd asymmetries, obtained using triple product correlations, measured for D0 and ¯¯¯D0 decays. The measured CP violation parameter is AT=(1.0±5.1stat±4.4syst)×10−3.Received 17 March 2010DOI:https://doi.org/10.1103/PhysRevD.81.111103©2010 American Physical Society

The absolute branching fractions for the decays $D^-_s\!\rightarrow\!\ell^-\bar{\nu}_{\ell}$ ($\ell=e$, $\mu$, or $\tau$) are measured using a data sample corresponding to an integrated luminosity of 521 fb$^{-1}$ collected at center of mass energies near 10.58 GeV with the \mbox{\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}} detector at the PEP-II $e^+e^-$ collider at SLAC. The number of $D^-_s$ mesons is determined by reconstructing the recoiling system $DKX\gamma$ in events of the type $e^+e^-{\rightarrow}DKXD^{*-}_s$, where $D^{*-}_s\rightarrow D^-_s\gamma$ and $X$ represents additional pions from fragmentation. The $D^-_s\!\rightarrow\!\ell^-\bar{\nu}_{\ell}$ events are detected by full or partial reconstruction of the recoiling system $DKX\gamma\ell$. The branching fraction measurements are combined to determine the $D^-_s$ decay constant $f_{D_s} = (258.6 \pm 6.4 \pm 7.5)$ MeV, where the first uncertainty is statistical and the second is systematic.

We report measurements of partial branching fractions for inclusive charmless semileptonic B decays Bbar --> Xu l nubar, and the determination of the CKM matrix element |V_{ub}|. The analysis is based on a sample of 467 million Upsilon(4S) --> BBar decays recorded with the BaBar detector at the PEP-II e^+ e^- storage rings. We select events in which the decay of one of the B mesons is fully reconstructed and an electron or a muon signals the semileptonic decay of the other B meson. We measure partial branching fractions DeltaB in several restricted regions of phase space and determine the CKM element |V_{ub}| based on four different QCD predictions. For decays with a charged lepton momentum p_l^* > 1.0 GeV in the B meson rest frame, we obtain DeltaB = (1.80 \pm 0.13 (stat.) \pm 0.15 (sys.) \pm 0.02 (theo.)) \times 10^{-3} from a fit to the two-dimensional mX-q^2 distribution. Here, mX refers to the invariant mass of the final state hadron X and q^2 is the invariant mass squared of the charged lepton and neutrino. From this measurement we extract |V_{ub}| = (4.33\pm 0.24 (exp.) \pm 0.15 (theo.)) \times 10^{-3} as the arithmetic average of four results obtained from four different QCD predictions of the partial rate. We separately determine partial branching fractions for B^0 and B^- decays and derive a limit on the isospin breaking in Bbar --> Xu l nubar decays.

We search for the rare decay of the ${D}^{0}$ meson to two photons, ${D}^{0}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$, and present a measurement of the branching fraction for a ${D}^{0}$ meson decaying to two neutral pions, $B({D}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0})$. The data sample analyzed corresponds to an integrated luminosity of $470.5\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected by the BABAR detector at the PEP-II asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider at SLAC. We place an upper limit on the branching fraction, $B({D}^{0}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma})&lt;2.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$, at 90% confidence level. This limit improves on the existing limit by an order of magnitude. We also find $B({D}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0})=(8.4\ifmmode\pm\else\textpm\fi{}0.1\ifmmode\pm\else\textpm\fi{}0.4\ifmmode\pm\else\textpm\fi{}0.3)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$.

We have searched for the lepton-number violating processes ${B}^{+}\ensuremath{\rightarrow}{h}^{\ensuremath{-}}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{+}$ with ${h}^{\ensuremath{-}}={K}^{\ensuremath{-}}/{\ensuremath{\pi}}^{\ensuremath{-}}$ and ${\ensuremath{\ell}}^{+}={e}^{+}/{\ensuremath{\mu}}^{+}$, using a sample of $471\ifmmode\pm\else\textpm\fi{}3$ million $B\overline{B}$ events collected with the BABAR detector at the PEP-II ${e}^{+}{e}^{\ensuremath{-}}$ collider at the SLAC National Accelerator Laboratory. We find no evidence for these decays and place 90%-confidence-level upper limits on their branching fractions $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{e}^{+}{e}^{+})&lt;2.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$, $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{e}^{+}{e}^{+})&lt;3.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$, $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{+})&lt;10.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$, and $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{+})&lt;6.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$.

We present results of a search for $CP$ violation in ${B}^{0}\mathrm{\text{\ensuremath{-}}}\text{ }{\overline{B}}^{0}$ mixing with the BABAR detector. We select a sample of ${B}^{0}\ensuremath{\rightarrow}{D}^{*\ensuremath{-}}X{\ensuremath{\ell}}^{+}\ensuremath{\nu}$ decays with a partial reconstruction method and use kaon tagging to assess the flavor of the other $B$ meson in the event. We determine the $CP$ violating asymmetry ${\mathcal{A}}_{CP}\ensuremath{\equiv}[N({B}^{0}{B}^{0})\ensuremath{-}N({\overline{B}}^{0}{\overline{B}}^{0})]/[N({B}^{0}{B}^{0})+N({\overline{B}}^{0}{\overline{B}}^{0})]=(0.06\ifmmode\pm\else\textpm\fi{}{0.17}_{\ensuremath{-}0.32}^{+0.38})%$, corresponding to ${\ensuremath{\Delta}}_{CP}=1\ensuremath{-}|q/p|=(0.29\ifmmode\pm\else\textpm\fi{}{0.84}_{\ensuremath{-}1.61}^{+1.88})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$.

We present measurements of the branching fractions of 3-prong and 5-prong tau decay modes using a sample of 430 million tau lepton pairs, corresponding to an integrated luminosity of 468 fb-1, collected with the BaBar detector at the PEP-II asymmetric energy e+e- storage rings. The τ- --&gt; (3π)- ην, τ- --&gt; (3π)- ων, and τ- --&gt; π- f_1(1285)ν, branching fractions are presented as well as a new limit on the branching fraction of the isospin-forbidden, second-class current, τ- --&gt; π-η'(958)ν, decay. We find no evidence for charged kaons in these decay modes and place the first upper limits on their branching fractions.

We study the process e+e- -> pi+pi-pi+pi-gamma, with a photon emitted from the initial-state electron or positron, using 454.3 fb^-1 of data collected with the BABAR detector at SLAC, corresponding to approximately 260,000 signal events. We use these data to extract the non-radiative sigma(e+e- ->pi+pi-pi+pi-) cross section in the energy range from 0.6 to 4.5 Gev. The total uncertainty of the cross section measurement in the peak region is less than 3%, higher in precision than the corresponding results obtained from energy scan data.

We study the processes $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}\ensuremath{\eta}$ and $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ using a data sample of $519\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider at center-of-mass energies at and near the $\mathit{\ensuremath{\Upsilon}}(nS)$ ($n=2,3,4$) resonances. We observe ${\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ and ${\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}\ensuremath{\eta}$ decays, measure their relative branching fraction, and perform a Dalitz plot analysis for each decay. We observe the ${K}_{0}^{*}(1430)\ensuremath{\rightarrow}K\ensuremath{\eta}$ decay and measure its branching fraction relative to the $K\ensuremath{\pi}$ decay mode to be $\mathcal{R}({K}_{0}^{*}(1430))=\frac{\mathcal{B}({K}_{0}^{*}(1430)\ensuremath{\rightarrow}K\ensuremath{\eta})}{\mathcal{B}({K}_{0}^{*}(1430)\ensuremath{\rightarrow}K\ensuremath{\pi})}=0.092\ifmmode\pm\else\textpm\fi{}0.02{5}_{\ensuremath{-}0.025}^{+0.010}$. The ${\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}\ensuremath{\eta}$ and ${K}_{0}^{*}(1430)\ensuremath{\rightarrow}K\ensuremath{\eta}$ results correspond to the first observations of these channels. The data also show evidence for ${\ensuremath{\eta}}_{c}(2S)\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ and first evidence for ${\ensuremath{\eta}}_{c}(2S)\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}\ensuremath{\eta}$.

We present measurements of Collins asymmetries in the inclusive process $e^+e^- \rightarrow h_1 h_2 X$, $h_1h_2=KK,\, K\pi,\, \pi\pi$, at the center-of-mass energy of 10.6 GeV, using a data sample of 468 fb$^{-1}$ collected by the BaBar experiment at the PEP-II $B$ factory at SLAC National Accelerator Center. Considering hadrons in opposite thrust hemispheres of hadronic events, we observe clear azimuthal asymmetries in the ratio of unlike- to like-sign, and unlike- to all charged $h_1 h_2$ pairs, which increase with hadron energies. The $K\pi$ asymmetries are similar to those measured for the $\pi\pi$ pairs, whereas those measured for high-energy $KK$ pairs are, in general, larger.

A measurement of absolute integrated luminosity is presented using the CLEO II detector operating at the CESR e+e− storage ring. Independent analyses of three different final states (e+e−, γγ, and μ+μ−) at √s ⋍ 10 GeV normalize to the expected theoretical cross sections and correct for detection efficiencies. The resulting luminosities are measured with systematic errors of ±1.8%, ±1.6%, and ±2.2%, respectively, and are consistent with one another. The combined luminosity has a systematic error of ±1.0%.

Using 385 fb−1 of e+e− collisions, we study the amplitudes of the singly Cabibbo-suppressed decay D0→K−K+π0. We measure the strong phase difference between the ¯¯¯D0 and D0 decays to K∗(892)+K− to be −35.5°±1.9°(stat)±2.2°(syst), and their amplitude ratio to be 0.599±0.013(stat)±0.011(syst). We observe contributions from the Kπ and K−K+ scalar and vector amplitudes, and analyze their angular moments. We find no evidence for charged κ, nor for higher spin states. We also perform a partial-wave analysis of the K−K+ system in a limited mass range.Received 26 April 2007DOI:https://doi.org/10.1103/PhysRevD.76.011102©2007 American Physical Society

With a sample of $232\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $\mathit{\ensuremath{\Upsilon}}(4S)\ensuremath{\rightarrow}B\overline{B}$ events collected with the BABAR detector, we study the decays of $B$ mesons to $p\overline{p}h$ final states, where $h={\ensuremath{\pi}}^{+}$, ${K}_{S}^{0}$, ${K}^{*0}$, or ${K}^{*+}$. We report evidence for the ${B}^{0}\ensuremath{\rightarrow}p\overline{p}{K}^{*0}$ decay, with a branching fraction $(1.47\ifmmode\pm\else\textpm\fi{}0.45(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.40(\mathrm{syst}))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$, and for the ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\eta}}_{c}{K}^{*+}$ decay, with the branching fraction of $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\eta}}_{c}{K}^{*+})\ifmmode\times\else\texttimes\fi{}\mathcal{B}({\ensuremath{\eta}}_{c}\ensuremath{\rightarrow}p\overline{p})=({1.57}_{\ensuremath{-}0.45}^{+0.56}(\mathrm{stat}{)}_{\ensuremath{-}0.36}^{+0.46}(\mathrm{syst}))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$, and provide improved measurements of the branching fractions of the other modes of this type. We also report the measurements of the charge asymmetry consistent with zero in the ${B}^{+}\ensuremath{\rightarrow}p\overline{p}{\ensuremath{\pi}}^{+}$, ${B}^{0}\ensuremath{\rightarrow}p\overline{p}{K}^{*0}$, and ${B}^{+}\ensuremath{\rightarrow}p\overline{p}{K}^{*+}$ modes. No evidence is found for the pentaquark candidate ${\ensuremath{\Theta}}^{+}$ in the mass range 1.52 to $1.55\text{ }\text{ }\mathrm{GeV}/{c}^{2}$, decaying into $p{K}_{S}^{0}$, or the glueball candidate ${f}_{J}(2220)$ in the mass range $2.2&lt;{m}_{p\overline{p}}&lt;2.4\text{ }\text{ }\mathrm{GeV}/{c}^{2}$, and branching fraction limits are established for both at the ${10}^{\ensuremath{-}7}$ level.

We present updated measurements of time-dependent CP asymmetries in fully-reconstructed neutral B decays to several CP eigenstates containing a charmonium meson. The measurements use a data sample of (383 +/- 4) x 10^6 Y(4S)-> BBbar decays collected with the BABAR detector at the PEP-II B factory. We determine sin2beta = 0.714 +/- 0.032 (stat) +/- 0.018 (syst) and |lambda| = 0.952 +/- 0.022 (stat) +/- 0.017 (syst).

We present the result from a precision measurement of the mass of the $\tau$ lepton, $M_\tau$, based on $423 fb^{-1}$ of data recorded at the $\Upsilon(4S)$ resonance with the BaBar detector. Using a pseudomass endpoint method, we determine the mass to be $1776.68 \pm 0.12 (stat) \pm 0.41 (syst) MeV$. We also measure the mass difference between the $\tau^+$ and $\tau^-$, and obtain $(M_{\tau^{+}}-M_{\tau^{-}})/M^\tau_{AVG} = (-3.4 \pm 1.3 (stat) \pm 0.3 (syst)) \times 10^{-4}$, where $M^\tau_{AVG}$ is the average value of $M_{\tau^+}$ and $M_{\tau^-}$.