S. Rahatlou

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.

This paper reports measurements of processes: e+e−→γKS0K±π∓, e+e−→γK+K−π0, e+e−→γϕη, and e+e−→γϕπ0. The initial-state radiated photon allows to cover the hadronic final state in the energy range from thresholds up to ≈4.6 GeV. The overall size of the data sample analyzed is 232 fb−1, collected by the BABAR detector running at the PEP-II e+e− storage ring. From the Dalitz plot analysis of the KS0K±π∓ final state, moduli, and relative phase of the isoscalar and the isovector components of the e+e−→KK*(892) cross section are determined. Parameters of ϕ and ρ recurrences are also measured, using a global fitting procedure which exploits the interconnection among amplitudes, moduli, and phases of the e+e−→KS0K±π∓, K+K−π0, ϕη final states. The cross section for the OZI-forbidden process e+e−→ϕπ0, and the J/ψ branching fractions to KK*(892) and K+K−η are also measured.33 MoreReceived 28 October 2007DOI:https://doi.org/10.1103/PhysRevD.77.092002©2008 American Physical Society

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 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.

SABRE aims to directly measure the annual modulation of the dark matter interaction rate with NaI(Tl) crystals. A modulation compatible with the standard hypothesis, in which our Galaxy is immersed in a dark matter halo, has been measured by the DAMA experiment in the same target material. Other direct detection experiments, using different target materials, seem to exclude the interpretation of such modulation in the simplest scenario of WIMP-nucleon elastic scattering. The SABRE experiment aims to carry out an independent search with sufficient sensitivity to confirm or refute the DAMA claim. The goal of the SABRE experiment is to achieve the lowest background rate for a NaI(Tl) experiment (order of 0.1 cpd/kg/keVee in the energy region of interest for dark matter). This challenging goal could be achievable by operating high-purity crystals inside a liquid scintillator veto for active background rejection. In addition, twin detectors will be located in the northern and southern hemispheres to identify possible contributions to the modulation from seasonal or site-related effects. The SABRE project includes an initial Proof-of-Principle phase at LNGS (Italy), to assess the radio-purity of the crystals and the efficiency of the liquid scintillator veto. This paper describes the general concept of SABRE and the expected sensitivity to WIMP annual modulation.

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 study the processes $e^+ e^-\to K^+ K^- \pi^+\pi^-\gamma$, $K^+K^-\pi^0\pi^0\gamma$ and $K^+ K^- K^+ K^-\gamma$, where the photon is radiated from the initial state. About 34600, 4400 and 2300 fully reconstructed events, respectively, are selected from 232 \invfb of \babar data. The invariant mass of the hadronic final state defines the effective \epem center-of-mass energy, so that the $K^+ K^- \pi^+\pi^-\gamma$ data can be compared with direct measurements of the $e^+ e^-\to K^+K^- \pipi$ reaction; no direct measurements exist for the $e^+ e^-\to K^+ K^- \pi^0\pi^0$ or $\epem\to K^+ K^- K^+ K^-$ reactions. 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 $e^+ e^-\to\phi(1020) f_{0}(980)$ and study its structure near threshold. In the charmonium region, we observe the $J/\psi$ in all three final states and several intermediate states, as well as the $\psi(2S)$ in some modes, and measure the corresponding branching fractions. We see no signal for the Y(4260) and obtain an upper limit of $\BR_{Y(4260)\to\phi\pi^+\pi^-}\cdot\Gamma^{Y}_{ee}<0.4 \ev$ at 90% C.L.

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.

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 CP-violating asymmetries of neutral charmed mesons in the modes D0 --> K- K+ and D0 --> pi- pi+ with the highest precision to date by using D0 --> K- pi+ decays to correct detector asymmetries. An analysis of 385.8 fb-1 of data collected with the BaBar detector yields values of aCP(KK) = (0.00 +/- 0.34 (stat.) +/- 0.13 (syst.))% and aCP(pipi) = (-0.24 +/- 0.52 (stat.) +/- 0.22 (syst.))%, which agree with Standard Model predictions.

We present a search for the decay ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}\ensuremath{\nu}$ using $383\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ 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 tag $B$ in a hadronic decay mode (${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{(*)0}{X}^{\ensuremath{-}}$), and 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 ${\ensuremath{\tau}}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0}\overline{\ensuremath{\nu}}$. We find a $2.2\ensuremath{\sigma}$ excess in data and measure a branching fraction of $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}\ensuremath{\nu})=({1.8}_{\ensuremath{-}0.8}^{+0.9}(\mathrm{stat}.)\ifmmode\pm\else\textpm\fi{}0.4(\mathrm{bkg}.\text{ }\mathrm{syst}.)\ifmmode\pm\else\textpm\fi{}0.2(\mathrm{other}\text{ }\mathrm{syst}.))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$. We calculate the product of the $B$ meson decay constant ${f}_{B}$ and $|{V}_{ub}|$ to be ${f}_{B}\ifmmode\cdot\else\textperiodcentered\fi{}|{V}_{ub}|=({10.1}_{\ensuremath{-}2.5}^{+2.3}(\mathrm{stat}.{)}_{\ensuremath{-}1.5}^{+1.2}(\mathrm{syst}.))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\text{ }\text{ }\mathrm{GeV}$.

Discovering a Higgs boson at the LHC will address a major outstanding issue in particle physics but will also raise many new questions. A concerted effort to determine the couplings of this new state to other Standard Model fields will be of critical importance. Precise knowledge of these couplings can serve as a powerful probe of new physics, and will be needed in attempts to accommodate such a new boson within specific models. In this paper, we present a method for constraining these couplings in a model-independent way, focusing primarily on an exclusive analysis of the gamma gamma final state. We demonstrate the discriminating power of fully exclusive analyses, and discuss ways in which information can be shared between experimentalists and theorists in order to facilitate collaboration in the task of establishing the true origins of any new physics discovered at the LHC.

We report the results of a study of the exclusive charmless semileptonic decay, B --> pi l nu, undertaken with approximately 227 million BBbar pairs collected at the Upsilon(4S) resonance with the BaBar detector. The analysis uses events in which the signal B decays are reconstructed with an innovative loose neutrino reconstruction technique. We obtain partial branching fractions in 12 bins of q2, the momentum transfer squared, from which we extract the f+(q2) form-factor shape and the total branching fraction BF(B0 --> pi l nu) = (1.46 +- 0.07(stat) +- 0.08(syst)) x 10^-4. Based on a recent unquenched lattice QCD calculation of the form factor in the range q2 > 16 GeV^2, we find the magnitude of the CKM matrix element |Vub| to be (4.1 +- 0.2(stat) +- 0.2(syst) +0.6-0.4(FF)) x 10^-3, where the last uncertainty is due to the normalization of the form factor.

We report observations of CP violation in the decays B(0) --> K(+)pi(-) and B(0) --> pi(+)pi(-) in a sample of 383 x 10(6) Upsilon(4S) --> BB[over] events. We find 4372+/-82 B(0) --> K(+)pi(-) decays and measure the direct CP-violating charge asymmetry A(Kpi) = -0.107+/-0.018(stat)(-0.004)(+0.007)(syst), which excludes the CP-conserving hypothesis with a significance of 5.5 standard deviations. In the same sample, we find 1139+/-49 B(0) --> pi(+)pi(-) decays and measure the CP-violating asymmetries S(pipi) = -0.60+/-0.11(stat)+/-0.03(syst) and C(pipi) = -0.21+/-0.09(stat)+/-0.02(syst). CP conservation in B(0) --> pi(+)pi(-) (S(pipi) = C(pipi) = 0) is excluded at a confidence level 1-C.L. = 8 x 10(-8), corresponding to 5.4 standard deviations.

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 report results of a search for CPT and Lorentz violation in B0−¯¯¯B0 oscillations using inclusive dilepton events from 232×106 Υ(4S)→B¯¯¯B decays recorded by the BABAR detector at the PEP-II B Factory at SLAC. We find 2.8σ significance, compatible with no signal, for variations in the complex CPT violation parameter z at the Earth’s sidereal frequency and extract values for the quantities Δaμ in the general Lorentz-violating standard-model extension. The spectral powers for variations in z over the frequency range 0.26 yr−1 to 2.1 solar day−1 are also compatible with no signal.Received 19 November 2007DOI:https://doi.org/10.1103/PhysRevLett.100.131802©2008 American Physical Society

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, $\mathcal{B}=(4.69\ifmmode\pm\else\textpm\fi{}0.04\ifmmode\pm\else\textpm\fi{}0.34)%$.

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

A measurement of the τ−→K−π0ντ branching fraction has been made using 230.2 fb−1 of data recorded by the BABAR detector at the PEP-II e+e− collider, located at the Stanford Linear Accelerator Center (SLAC), at a center-of-mass energy √s close to 10.58 GeV. We measure B(τ−→K−π0ντ)=(0.416±0.003(stat)±0.018(syst))%.Received 18 July 2007DOI:https://doi.org/10.1103/PhysRevD.76.051104©2007 American Physical Society

We report measurements of B-meson decays into two- and three-body final states containing two charmed baryons using a sample of 230 million Y(4S) -> B Bbar decays. We find significant signals in two modes, measuring branching fractions BF(B^- -> \Lambda_c^+ \Lambda_c^- K^-) = (1.14 +- 0.15 +- 0.17 +- 0.60) x 10^{-3} and BF(B^- -> \Xi_c^0 \Lambda_c^-) x BF(\Xi_c^0 -> \Xi^- \pi^+) = (2.08 +- 0.65 +- 0.29 +- 0.54) x 10^{-5}, where the uncertainties are statistical, systematic, and from the branching fraction BF(\Lambda_c^+ -> p K^- \pi^+), respectively. We also set upper limits at the 90% confidence level on two other modes: BF(B0bar -> \Xi_c^+ \Lambda_c^-) x BF(\Xi_c^+ -> \Xi^- \pi^+ \pi^+) < 5.6 x 10^{-5} and BF(B0bar -> \Lambda_c^+ \Lambda_c^- K0bar) < 1.5 x 10^{-3}. We observe structure centered at an invariant mass of 2.93 GeV/c^2 in the \Lambda_c^+ K^- mass distribution of the decay B^- -> \Lambda_c^+ \Lambda_c^- K^-.

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 the observation of charmless hadronic decays of charged B mesons to the final state K+K−π+. Using a data sample of 347.5 fb−1 collected at the Υ(4S) resonance with the BABAR detector, we observe 429±43 signal events with a significance of 9.6σ. We measure the inclusive branching fraction B(B+→K+K−π+)=[5.0±0.5(stat)±0.5(syst)]×10−6. Inspection of the Dalitz plot of signal candidates shows a broad structure peaking near 1.5 GeV/c2 in the K+K− invariant mass distribution. We find the direct CP asymmetry to be consistent with zero.Received 3 August 2007DOI:https://doi.org/10.1103/PhysRevLett.99.221801©2007 American Physical Society

We present a search for the decay ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}\ensuremath{\nu}$ using $383\ifmmode\times\else\texttimes\fi{}{10}^{6}B\overline{B}$ pairs collected at the $\ensuremath{\Upsilon}(4S)$ resonance with the BABAR detector at the SLAC PEP-II $B$-Factory. A sample of events with one reconstructed semileptonic $B$ decay (${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{0}\ensuremath{\ell}\ensuremath{-}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}}X$) is selected, and in the recoil a search for ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}\ensuremath{\nu}$ is performed. The $\ensuremath{\tau}$ is identified in the following channels: ${\ensuremath{\tau}}^{+}\ensuremath{\rightarrow}{e}^{+}\ensuremath{\nu}\overline{\ensuremath{\nu}}$, ${\ensuremath{\tau}}^{+}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}\ensuremath{\nu}\overline{\ensuremath{\nu}}$, ${\ensuremath{\tau}}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}\overline{\ensuremath{\nu}}$, and ${\ensuremath{\tau}}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0}\overline{\ensuremath{\nu}}$. We measure a branching fraction of $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}\ensuremath{\nu})=(0.9\ifmmode\pm\else\textpm\fi{}0.6(\mathrm{stat}.)\ifmmode\pm\else\textpm\fi{}0.1(\mathrm{syst}.))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$. In the absence of a significant signal, we calculate an upper limit at the 90% confidence level of $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}\ensuremath{\nu})&lt;1.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$. We calculate the product of the $B$ meson decay constant ${f}_{B}$ and $|{V}_{\mathrm{ub}}|$ to be ${f}_{B}\ifmmode\cdot\else\textperiodcentered\fi{}|{V}_{\mathrm{ub}}|=({7.2}_{\ensuremath{-}2.8}^{+2.0}(\mathrm{stat}.)\ifmmode\pm\else\textpm\fi{}0.2(\mathrm{syst}.))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\text{ }\text{ }\mathrm{GeV}$.

We report the results of a CP violation analysis of the decay B+/- --> D(pipipi0)K+/-, where D(pipipi0) indicates a neutral D meson detected in the final state pi+pi-pi0, excluding K_S pi0. The analysis makes use of 324 million e+e- --> BB events recorded by the BaBar experiment at the PEP-II e+e- storage ring. By analyzing the pi+pi-pi0 Dalitz plot distribution and the B+/- --> D(pipipi0)K+/- branching fraction and decay rate asymmetry, we calculate parameters related to the phase gamma of the CKM unitarity triangle. We also measure the magnitudes and phases of the components of the D0 --> pi+pi-pi0 decay amplitude.

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 study the processes $e^+ e^-\to 2(\pi^+\pi^-)\pi^0\gamma$, $2(\pi^+\pi^-)\eta\gamma$, $K^+ K^-\pi^+\pi^-\pi^0\gamma$ and $K^+ K^-\pi^+\pi^-\eta\gamma$ with the hard photon radiated from the initial state. About 20000, 4300, 5500 and 375 fully reconstructed events, respectively, are selected from 232 fb$^{-1}$ of BaBar data. The invariant mass of the hadronic final state defines the effective $e^+ e^-$ center-of-mass energy, so that the obtained cross sections from the threshold to about 5 GeV can be compared with corresponding direct \epem measurements, currently available only for the $\eta\pi^+\pi^-$ and $\omega\pi^+\pi^-$ submodes of the $e^+ e^-\to 2(\pi^+\pi^-)\pi^0$ 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 $e^+ e^-\to\omega(782)\pi^+\pi^-$ and study the $\omega(1420)$ and $\omega(1650)$ resonances. In the charmonium region, we observe the $J/\psi$ in all these final states and several intermediate states, as well as the $\psi(2S)$ in some modes, and we measure the corresponding branching fractions.

We report on the response of microchannel plates (MCPs) to single relativistic particles and to electromagnetic showers. Particle detection by means of secondary emission of electrons at the MCP surface has long been proposed and is used extensively in ion time-of-flight mass spectrometers. What has not been investigated in depth is their use to detect the ionizing component of showers. The time resolution of MCPs exceeds anything that has been previously used in calorimeters and, if exploited effectively, could aid in the event reconstruction at high luminosity colliders. Several prototypes of photodetectors with the amplification stage based on MCPs were exposed to cosmic rays and to 491 MeV electrons at the INFN-LNF Beam-Test Facility. The time resolution and the efficiency of the MCPs are measured as a function of the particle multiplicity, and the results used to model the response to high-energy showers.

We analyze the decay B0 --> K+ K- K0 using 383 million B-Bbar events collected by the BaBar detector at SLAC to extract CP violation parameter values over the Dalitz plot. Combining all K+ K- K0 events, we find A_CP = -0.015 +/- 0.077 +/- 0.053 and beta_eff = 0.352 +/- 0.076 +/- 0.026 rad, corresponding to a CP violation significance of 4.8 sigma. A second solution near pi/2 - beta_eff is disfavored with a significance of 4.5 sigma. We also report A_CP and beta_eff separately for decays to phi(1020) K0, f0(980) K0, and K+ K- K0 with m_{K+ K-} > 1.1 GeV/c^2.

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 have searched for ${D}^{0}\ensuremath{-}{\overline{D}}^{0}$ mixing in ${D}^{*+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{D}^{0}$ decays with ${D}^{0}\ensuremath{\rightarrow}{K}^{(*)}e\ensuremath{\nu}$ in a sample of ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}c\overline{c}$ events produced near 10.58 GeV. The charge of the slow pion from charged ${D}^{*}$ decay tags the charm flavor at production, and it is required to be consistent with the flavor of a fully reconstructed second charm decay in the same event. We observe 3 mixed candidates compared to 2.85 background events expected from simulation. We ascribe a 50% systematic uncertainty to this expected background rate. We find a central value for the mixing rate of $0.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$. Using a frequentist method, we set corresponding 68% and 90% confidence intervals at $(\ensuremath{-}5.6,7.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ and $(\ensuremath{-}13,12)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$, respectively.

Using 385 fb−1 of e+e− collision data collected at center-of-mass energies around 10.6 GeV, we search for time-integrated CP violation in the Cabibbo-suppressed decays D0/¯¯¯D0→π−π+π0 and D0/¯¯¯D0→K−K+π0 with both model-independent and model-dependent methods. Measurements of the asymmetries in amplitudes of flavor states and CP eigenstates provide constraints on theories beyond the standard model, some of which predict CP violation in amplitudes at the 1% level or higher. We find no evidence of CP violation and hence no conflict with the standard model.Received 27 February 2008DOI:https://doi.org/10.1103/PhysRevD.78.051102©2008 American Physical Society

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 report a measurement of CP-violating asymmetries in B0-->(rhopi)0-->pi+pi-pi0 decays using a time-dependent Dalitz plot analysis. The results are obtained from a data sample of 375 million Y(4S) --> BBbar decays, collected by the BaBar detector at the PEP-II asymmetric-energy B Factory at SLAC. We measure 26 coefficients of the bilinear form-factor terms occurring in the time-dependent decay rate of the B0 meson. We derive the physically relevant quantities from these coefficients. In particular, we measure a constraint on the angle alpha of the Unitarity Triangle.

We present searches for the leptonic decays B+→ℓ+ν and the lepton flavor violating decays B0→ℓ±τ∓, where ℓ=e, μ, with data collected by the BABAR experiment at SLAC. This search demonstrates a novel technique in which we fully reconstruct the accompanying ¯¯¯B in Υ(4S)→B¯¯¯B events, and look for a monoenergetic lepton from the signal B decay. The signal yield is extracted from a fit to the signal lepton candidate momentum distribution in the signal B rest frame. Using a data sample of approximately 378×106 B¯¯¯B pairs (342 fb−1), we find no evidence of signal in any of the decay modes. Branching fraction upper limits of B(B+→e+ν)<5.2×10−6, B(B+→μ+ν)<5.6×10−6, B(B0→e+τ−)<2.8×10−5 and B(B0→μ+τ−)<2.2×10−5, are obtained at 90% confidence level.Received 7 January 2008DOI:https://doi.org/10.1103/PhysRevD.77.091104©2008 American Physical Society

We report a Dalitz-plot analysis of the charmless hadronic decays of neutral $B$ mesons to ${K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{0}$. With a sample of $(231.8\ifmmode\pm\else\textpm\fi{}2.6)\ifmmode\times\else\texttimes\fi{}{10}^{6}\mathit{\ensuremath{\Upsilon}}(4S)\ensuremath{\rightarrow}B\overline{B}$ decays collected by the BABAR detector at the PEP-II asymmetric-energy $B$ Factory at SLAC, we measure the magnitudes and phases of the intermediate resonant and nonresonant amplitudes for ${B}^{0}$ and ${\overline{B}}^{0}$ decays and determine the corresponding $CP$-averaged branching fractions and charge asymmetries. The inclusive branching fraction and $CP$-violating charge asymmetry are measured to be $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0})=({35.7}_{\ensuremath{-}1.5}^{+2.6}\ifmmode\pm\else\textpm\fi{}2.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ and ${\mathcal{A}}_{CP}=\ensuremath{-}{0.030}_{\ensuremath{-}0.051}^{+0.045}\ifmmode\pm\else\textpm\fi{}0.055$ where the first errors are statistical and the second systematic. We observe the decay ${B}^{0}\ensuremath{\rightarrow}{K}^{*0}(892){\ensuremath{\pi}}^{0}$ with the branching fraction $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{K}^{*0}(892){\ensuremath{\pi}}^{0})=({3.6}_{\ensuremath{-}0.8}^{+0.7}\ifmmode\pm\else\textpm\fi{}0.4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. This measurement differs from zero by 5.6 standard deviations (including the systematic uncertainties). The selected sample also contains ${B}^{0}\ensuremath{\rightarrow}{\overline{D}}^{0}{\ensuremath{\pi}}^{0}$ decays where ${\overline{D}}^{0}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, and we measure $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{\overline{D}}^{0}{\ensuremath{\pi}}^{0})=(2.93\ifmmode\pm\else\textpm\fi{}0.17\ifmmode\pm\else\textpm\fi{}0.18)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$.

The "\tau\to 3\pi\eta\nu" decay with the "\eta \to \gamma\gamma" mode is studied using 384 fb^-1 of data collected by the BaBar detector. The branching fraction is measured to be (1.60+/-0.05+/-0.11)x10^-4. It is found that "\tau \to f1 \pi \nu to 3\pi \eta \nu" is the dominant decay mode with a branching fraction of (1.11+/-0.06+/-0.05)x10^-4. The first error on the branching fractions is statistical and the second systematic. In addition, a 90% confidence level upper limit on the branching fraction of the "\tau \to \eta'(958) \pi \nu" decay is measured to be 7.2x10^-6. This last decay proceeds through a second-class current and is expected to be forbidden in the limit of isospin symmetry.

We report the observation of the b -> d penguin-dominated decay B0 -> K*0 K*0bar with a sample of 383.2 +/- 4.2 million BBbar pairs collected with the BaBar detector at the PEP-II asymmetric-energy e^+e^- collider at the Stanford Linear Accelerator Center. The measured branching fraction is Br(B0 -> K*0 K*0bar) = [1.28^{+0.35}_{-0.30} +/- 0.11] x 10^{-6} and the fraction of longitudinal polarization f_L (B0 -> K*0 K*0bar) = 0.80^{+0.10}_{-0.12} +/- 0.06. The first error quoted is statistical and the second systematic. We also obtain an upper limit at the 90% confidence level on the branching fraction for Br(B0 ->K*0 K*0) < 0.41 x 10^{-6}.

We perform an amplitude analysis of B+/--->phi(1020)K*(892)+/- decay with a sample of about 384 x 10(6) BB[over ] pairs recorded with the BABAR detector. Overall, twelve parameters are measured, including the fractions of longitudinal fL and parity-odd transverse f perpendicular amplitudes, branching fraction, strong phases, and six parameters sensitive to CP violation. We use the dependence on the Kpi invariant mass of the interference between the JP=1(-) and 0+ Kpi components to resolve the discrete ambiguity in the determination of the strong and weak phases. Our measurements of fL=0.49+/-0.05+/-0.03, f perpendicular=0.21+/-0.05+/-0.02, and the strong phases point to the presence of a substantial helicity-plus amplitude from a presently unknown source.

We report a measurement of the branching fractions for _B-->D(*)(pi)l- _nu(l) decays based on 341.1 fb(-1) of data collected at the Upsilon(4S) resonance with the BABAR detector at the SLAC PEP-II e+ e- storage rings. Events are tagged by fully reconstructing one of the B mesons in a hadronic decay mode. We obtain B(B- -->D(0)l-_nu(l)=(2.33+/-0.09(stat)+/-0.09(syst)%, B(B- -->D(*0)l-_nu(l)=(5.83+/-0.15(stat) +/-0.30(syst) %, B(_B(0)-->D+l-_nu(l)=(2.21+/-0.11(stat) +/-0.12(syst)%, B(_B(0)-->D(*)l-_nu(l)=(5.49+/-0.16(stat)+/-0.25(syst)%, B(B- -->D+pi-l-_nu(l)=(0.42+/-0.06(stat)+/-0.03(syst)%, B(B- -->D(*)+pi-l-_nu(l)=(0.59+/-0.05(stat)+/-0.04(syst)%, B(_B(0)-->D(0)pi+l-_nu(l)=(0.43+/-0.08(stat)+/-0.03(syst)%, and B(_B(0)-->D(*0)pi+l-_nu(l)=(0.48+/-0.08(stat)+/-0.04(syst)%.

A search for lepton flavor violating decays of a τ to a lighter-mass charged lepton and an ω vector meson is performed using 384.1 fb−1 of e+e− annihilation data collected with the BABAR detector at the Stanford Linear Accelerator Center PEP-II storage ring. No signal is found, and the upper limits on the branching ratios are determined to be B(τ±→e±ω)<1.1×10−7 and B(τ±→μ±ω)<1.0×10−7 at 90% confidence level.Received 6 November 2007DOI:https://doi.org/10.1103/PhysRevLett.100.071802©2008 American Physical Society

INFN Kids is a science education project of the Italian National Institute for Nuclear Physics addressed to young people of Primary and Middle schools age. The initiative aims at raising children’s curiosity towards science with a focus on Physics, inspiring them with science by illustrating the different research fields that INFN is pursuing, the development in technologies along with the applications in everyday life and presenting people who animate science. It gathers technicians and researchers of thirteen units and National labs in the design and realization of multimedia products, laboratory-based activities, comics, science demos and exhibits. The activities are conducted online and in person in schools, science festivals and at INFN’s sites. The adopted methodologies and the didactic tools (lectures, interactive lessons, hands-on sessions, science games) involve children in the direct exploration of natural phenomena. Given the manifold plan of activities the recipients of the project are also teachers and families, and this allowed to expand and use different formats to meet the audience’s requests. We here present an overview of the ongoing initiatives to share our experiences and we illustrate in particular the comics centered on the characters Leo and Alice that drive children in the investigation of the micro and macro world, and the laboratory-based activities designed to introduce kids some fundamental concepts related to matter and its inner structure.

We present an analysis of inclusive Ω0c baryon production and decays in 230.5 fb−1 of data recorded with the BABAR detector. Ω0c baryons are reconstructed in four final states (Ω−π+, Ω−π+π0, Ω−π+π+π−, Ξ−K−π+π+) and the corresponding ratios of branching fractions are measured. We also measure the momentum spectrum in the e+e− center-of-mass frame. From the spectrum, we observe Ω0c production from B decays and in c¯c events, and extract the two rates of production.Received 17 March 2007DOI:https://doi.org/10.1103/PhysRevLett.99.062001©2007 American Physical Society

We present measurements of $CP$-violating asymmetries in the decay ${B}^{0}\ensuremath{\rightarrow}{a}_{1}^{\ifmmode\pm\else\textpm\fi{}}(1260){\ensuremath{\pi}}^{\ensuremath{\mp}}$ with ${a}_{1}^{\ifmmode\pm\else\textpm\fi{}}(1260)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$. The data sample corresponds to $384\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs collected with the BABAR detector at the PEP-II asymmetric $B$ factory at SLAC. We measure the $CP$-violating asymmetry ${\mathcal{A}}_{CP}^{{a}_{1}\ensuremath{\pi}}=\ensuremath{-}0.07\ifmmode\pm\else\textpm\fi{}0.07\ifmmode\pm\else\textpm\fi{}0.02$, the mixing-induced $CP$ violation parameter ${S}_{{a}_{1}\ensuremath{\pi}}=0.37\ifmmode\pm\else\textpm\fi{}0.21\ifmmode\pm\else\textpm\fi{}0.07$, the direct $CP$ violation parameter ${C}_{{a}_{1}\ensuremath{\pi}}=\ensuremath{-}0.10\ifmmode\pm\else\textpm\fi{}0.15\ifmmode\pm\else\textpm\fi{}0.09$, and the parameters $\ensuremath{\Delta}{C}_{{a}_{1}\ensuremath{\pi}}=0.26\ifmmode\pm\else\textpm\fi{}0.15\ifmmode\pm\else\textpm\fi{}0.07$ and $\ensuremath{\Delta}{S}_{{a}_{1}\ensuremath{\pi}}=\ensuremath{-}0.14\ifmmode\pm\else\textpm\fi{}0.21\ifmmode\pm\else\textpm\fi{}0.06$. From these measured quantities we determine the angle ${\ensuremath{\alpha}}_{\mathrm{eff}}=78.6\ifmmode^\circ\else\textdegree\fi{}\ifmmode\pm\else\textpm\fi{}7.3\ifmmode^\circ\else\textdegree\fi{}$.

We present a study of the decays ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{+}\ensuremath{\gamma}$, ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}\ensuremath{\gamma}$, and ${B}^{0}\ensuremath{\rightarrow}\ensuremath{\omega}\ensuremath{\gamma}$. The analysis is based on data containing $347\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ events recorded with the BABAR detector at the PEP-II asymmetric $B$ factory. We measure the branching fractions $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{+}\ensuremath{\gamma})=({1.10}_{\ensuremath{-}0.33}^{+0.37}\ifmmode\pm\else\textpm\fi{}0.09)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ and $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}\ensuremath{\gamma})=({0.79}_{\ensuremath{-}0.20}^{+0.22}\ifmmode\pm\else\textpm\fi{}0.06)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$, and set a 90% C.L. upper limit $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}\ensuremath{\omega}\ensuremath{\gamma})&lt;0.78\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. We also measure the isospin-averaged branching fraction $\mathcal{B}\mathbf{(}B\ensuremath{\rightarrow}(\ensuremath{\rho}/\ensuremath{\omega})\ensuremath{\gamma}\mathbf{)}=({1.25}_{\ensuremath{-}0.24}^{+0.25}\ifmmode\pm\else\textpm\fi{}0.09)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$, from which we determine $|{V}_{\mathrm{td}}/{V}_{\mathrm{ts}}|={0.200}_{\ensuremath{-}0.020}^{+0.021}\ifmmode\pm\else\textpm\fi{}0.015$, where the first uncertainty is experimental and the second is theoretical.

We present updated measurements of CP-violating asymmetries in the decays B0-->D*(+/-)D(-/+) and B0-->D+D- using (383+/-4) x 10(6)B(B) pairs collected by the BABAR detector at the SLAC PEP-II B factory. We determine the time-integrated CP asymmetry A(D*(+/-)D(-/+))=0.12+/-0.06+/-0.02, and the time-dependent asymmetry parameters to be C(D*+D-)=0.18+/-0.15+/-0.04, S(D*+D-)=-0.79+/-0.21+/-0.06, C(D*-D+)=0.23+/-0.15+/-0.04, S(D*-D+)=-0.44+/-0.22+/-0.06, C(D+D-)=0.11+/-0.22+/-0.07, and S(D+D-)=-0.54+/-0.34+/-0.06, where the first uncertainty is statistical and the second is systematic.

Using 226×106 B¯¯¯B events recorded on the Υ(4S) resonance with the BABAR detector at the SLAC e+e− PEP-II storage rings, we reconstruct B−→D*0e−¯νe decays using the decay chain D*0→D0π0 and D0→K−π+. From the dependence of their differential rate on w, the dot product of the four velocities of B− and D*0, and using the form factor description by Caprini et al. with the parameters F(1) and ρ2A1, we obtain the results ρ2A1=1.16±0.06±0.08, F(1)|Vcb|=(35.9±0.6±1.4)×10−3, and B(B−→D*0e−¯νe)=(5.56±0.08±0.41)%.Received 14 January 2008DOI:https://doi.org/10.1103/PhysRevLett.100.231803©2008 American Physical Society

The properties of the Ξ(1530) resonance are investigated in the Λ+c→Ξ−π+K+ decay process. The data sample was collected with the BABAR detector at the SLAC PEP-II asymmetric-energy e+e− collider operating at center-of-mass energies 10.58 and 10.54 GeV. The corresponding integrated luminosity is approximately 230 fb−1. The spin of the Ξ(1530) is established to be 3/2. The existence of an S-wave amplitude in the Ξ−π+ system is inferred, and its interference with the Ξ(1530)0 amplitude provides the first clear demonstration of the Breit-Wigner phase motion expected for the Ξ(1530). The P1(cosθΞ−) Legendre polynomial moment indicates the presence of a significant S-wave amplitude for Ξ−π+ mass values above 1.6 GeV/c2, and a dip in the mass distribution at approximately 1.7 GeV/c2 is interpreted as due to the coherent addition of a Ξ(1690)0 contribution to this amplitude. This would imply JP=1/2− for the Ξ(1690). Attempts at fitting the Ξ(1530)0 line shape yield unsatisfactory results, and this failure is attributed to interference effects associated with the amplitudes describing the K+π+ and/or Ξ−K+ systems.5 MoreReceived 12 March 2008DOI:https://doi.org/10.1103/PhysRevD.78.034008©2008 American Physical Society

We have performed a search for the flavor-changing neutral-current decays B→πℓ+ℓ−, where ℓ+ℓ− is either e+e− or μ+μ−, using a sample of 230×106 Υ(4S)→B¯¯¯B decays collected with the BABAR detector. We observe no evidence of a signal and measure the upper limit on the isospin-averaged branching fraction to be B(B→πℓ+ℓ−)<9.1×10−8 at 90% confidence level. We also search for the lepton-flavor-violating decays B→πe±μ∓ and measure an upper limit on the isospin-averaged branching fraction of B(B→πe±μ∓)<9.2×10−8 at 90% confidence level.Received 9 March 2007DOI:https://doi.org/10.1103/PhysRevLett.99.051801©2007 American Physical Society

We present partial branching fractions for inclusive charmless semileptonic B decays Bbar --> X_u ell nubar, and the determination of the CKM matrix element |V_{ub}|. The analysis is based on a sample of 383 million Y(4S) decays into B Bbar pairs collected with the BaBar detector at the PEP-II e+ e- storage rings. We select events using either the invariant mass M_X of the hadronic system, the invariant mass squared, q^2, of the lepton and neutrino pair, the kinematic variable P_+ or one of their combinations. We then determine partial branching fractions in limited regions of phase space: Delta B = (1.18 +- 0.09_{stat.} +- 0.07_{syst.} +- 0.01_{theo.}) x 10^{-3} (M_X < 1.55 GeV/c^2), Delta B = (0.95 +- 0.10_{stat.} +- 0.08_{syst.} +- 0.01_{theo.}) x 10^{-3} (P_+ < 0.66 GeV/c), and Delta B = (0.81 +- 0.08_{stat.} +- 0.07_{syst.} +- 0.02_{theo.}) x 10^{-3} (M_X < 1.7 GeV/c^2, q^2 > 8 GeV^2/c^4). Corresponding values of |V_{ub}| are extracted using several theoretical calculations.

Cerium-doped Lutetium-Yttrium Oxyorthosilicate (LYSO:Ce)is one of the most widely used Cerium-doped Lutetium based scintillation crystals. Initially developed for medical detectors it rapidly became attractive for High Energy Particle Physics (HEP) applications, especially in the frame of high luminosity particle colliders. In this paper, a comprehensive and systematic study of LYSO:Ce ($[Lu_{(1-x)}Y_x]_2SiO_5$:$Ce$) crystals is presented. It involves for the first time a large number of crystal samples (180) of the same size from a dozen of producers.The study consists of a comparative characterization of LYSO:Ce crystal products available on the market by mechanical, optical and scintillation measurements and aims specifically, to investigate key parameters of timing applications for HEP.

We present a search for the lepton flavor violating decay B+→K+τ∓μ± using 383×106 B¯¯¯B events collected by the BABAR experiment. The branching fraction for this decay can be substantially enhanced in new physics models. The kinematics of the tau from the signal B decay are inferred from the K+, μ, and other B in the event, which is fully reconstructed in one of a variety of hadronic decay modes, allowing the signal B candidate to be fully reconstructed. We observe no excess of events over the expected background and set a limit of B(B+→K+τμ)<7.7×10−5 at 90% confidence level, where the branching fraction is for the sum of the K+τ−μ+ and K+τ+μ− final states. We use this result to improve a model-independent bound on the energy scale of flavor-changing new physics.Received 9 August 2007DOI:https://doi.org/10.1103/PhysRevLett.99.201801©2007 American Physical Society

We study the time-dependent Dalitz plot of D-->K_{S};{0}pi;{+}pi;{-} in B;{0}-->D;{(*)}h;{0} decays, where h;{0} is a pi;{0}, eta, eta;{'}, or omega meson and D;{*}-->Dpi;{0}, using a data sample of 383x10;{6} Upsilon(4S)-->BB[over ] decays collected with the BABAR detector. We determine cos2beta=0.42+/-0.49+/-0.09+/-0.13, sin2beta=0.29+/-0.34+/-0.03+/-0.05, and |lambda|=1.01+/-0.08+/-0.02, where the first error is statistical, the second is the experimental systematic uncertainty, and the third, where given, is the Dalitz model uncertainty. Assuming the world average value for sin2beta and |lambda|=1, cos2beta>0 is preferred over cos2beta<0 at 86% confidence level.

We present the results of searches for decays of B mesons to final states with a b1 meson and a charged pion or kaon. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent 382x10(6) BB[over ] pairs produced in e+e- annihilation. The results for the branching fractions are, in units of 10(-6), B(B+-->b1(0)pi+)=6.7+/-1.7+/-1.0, B(B+-->b1(0)K+)=9.1+/-1.7+/-1.0, B(B0-->b1(-/+)pi(+/-))=10.9+/-1.2+/-0.9, and B(B0-->b1(-)K+)=7.4+/-1.0+/-1.0, with the assumption that B(b1-->omega pi)=1. We also measure charge and flavor asymmetries A(ch)(B+-->b1(0)pi+)=0.05+/-0.16+/-0.02, Ach(B+-->b1(0)K+)=-0.46+/-0.20+/-0.02, A(ch)(B0-->b1(-/+)pi(+/-))=-0.05+/-0.10+/-0.02, C(B0-->b1(-/+)pi(+/-))=-0.22+/-0.23+/-0.05, DeltaC(B0-->b1(-/+)pi(+/-))=-1.04+/-0.23+/-0.08, and A(ch)(B0-->b1(-)K+)=-0.07+/-0.12+/-0.02. The first error quoted is statistical, and the second systematic.

We present branching fraction measurements of the decays B(+)-->a(1)(+)(1260)K(0) and B(0)-->a(1)(-)(1260)K(+) with a(1)(+/-)(1260)-->pi(-/+)pi(+/-)pi(+/-). The data sample corresponds to 383 x 10(6) BB pairs produced in e(+)e(-) annihilation through the Upsilon(4S) resonance. We measure the products of the branching fractions B(B(+)-->a(1)(+)(1260)K(0)B(a(1)(+)(1260)-->pi(-)pi(+)pi(+))=(17.4+/-2.5+/-2.2) x 10(-6) and B(B(0)-->a(1)(-)(1260)K(+)B(a(1)(-)(1260)-->pi(+)pi(-)pi(-)) = (8.2+/-1.5+/-1.2) x 10(-6). We also measure the charge asymmetries A(ch)(B(+)-->a(1)(+)(1260)K(0) = 0.12+/-0.11+/-0.02 and A(ch)(B(0)-->a(1)(-)(1260)K+) = -0.16+/-0.12+/-0.01. The first uncertainty quoted is statistical and the second is systematic.

Motivated by the polarization anomaly in the B->phi(1020)K*(892) decay, we extend our search for other K* final states in the decay B0->phi(1020)K^*0 with the K*0->K+pi- invariant mass above 1.6 GeV. The final states considered include the K*(1680)0, K3*(1780)0, K4*(2045)0, and a Kpi spin-zero nonresonant component. We also search for B0->phiDbar0 decay with the same final state. The analysis is based on a sample of about 384 million BBbar pairs recorded with the BABAR detector. We place upper limits on the branching fractions BR(B0->phiK*(1680)0)<3.5*10^-6, BR(B0->phiK3*(1780)0)<2.7*10^-6, BR(B0->phiK4*(2045)0)<15.3*10^-6, and BR(B0->phiDbar0)<11.7*10^-6 at 90% C.L. The nonresonant contribution is consistent with the measurements in the lower invariant mass range.

We present measurements of the branching fractions for ${B}^{0}$-meson decays to ${\ensuremath{\eta}}^{\ensuremath{'}}{K}^{0}$ and $\ensuremath{\omega}{K}^{0}$, and of the branching fractions and $CP$-violation charge asymmetries for ${B}^{+}$-meson decays to $\ensuremath{\eta}{\ensuremath{\pi}}^{+}$, $\ensuremath{\eta}{K}^{+}$, ${\ensuremath{\eta}}^{\ensuremath{'}}{\ensuremath{\pi}}^{+}$, ${\ensuremath{\eta}}^{\ensuremath{'}}{K}^{+}$, $\ensuremath{\omega}{\ensuremath{\pi}}^{+}$, and $\ensuremath{\omega}{K}^{+}$. The data, collected with the BABAR detector at the Stanford Linear Accelerator Center, represent $383\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs produced in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation. The measurements agree with previous results; we find no evidence for direct $CP$ violation.

We present a search for the decays B0→e+e−, B0→μ+μ−, and B0→e±μ∓ using data collected with the BABAR detector at the PEP-II e+e− collider at SLAC. Using a data set corresponding to 384×106 B¯¯¯B pairs, we do not find evidence of any of the three decay modes. We obtain upper limit on the branching fractions, at 90% confidence level, of B(B0→e+e−)<11.3×10−8, B(B0→μ+μ−)<5.2×10−8, and B(B0→e±μ∓)<9.2×10−8.Received 10 December 2007DOI:https://doi.org/10.1103/PhysRevD.77.032007©2008 American Physical Society

We present measurements of the branching fractions for the decays B;{+/-}-->a_{1};{+/-}(1260)pi;{0} and B;{+/-}-->a_{1};{0}(1260)pi;{+/-} from a data sample of 232x10;{6} BB[over ] pairs produced in e;{+}e;{-} annihilation through the Upsilon(4S) resonance. We measure the branching fraction B(B;{+/-}-->a_{1};{+/-}(1260)pi;{0})xB(a_{1};{+/-}(1260)-->pi;{-}pi;{+}pi;{+/-})=(13.2+/-2.7+/-2.1)x10;{-6} with a significance of 4.2sigma, and the branching fraction B(B;{+/-}-->a_{1};{0}(1260)pi;{+/-})xB(a_{1};{0}(1260)-->pi;{-}pi;{+}pi;{0})=(20.4+/-4.7+/-3.4)x10;{-6} with a significance of 3.8sigma, where the first error quoted is statistical and the second is systematic.

We perform a measurement of the CP asymmetry in b-->sgamma decays using a sample of 383 x 10(6) B[over] B events collected by the BABAR detector at the SLAC PEP-II asymmetric B factory. We reconstruct 16 flavor-specific B decay modes containing a high-energy photon and a hadronic system X_(s) containing an s quark. We measure the CP asymmetry to be -0.011+/-0.030(stat)+/-0.014(syst) for a hadronic system mass between 0.6 and 2.8 GeV/c(2).

We present constraints on the angle γ of the unitarity triangle with a Dalitz analysis of neutral D decays to KSπ+π− from the processes B0→¯¯¯D0K*0 (¯¯¯B0→D0¯¯¯¯K*0) and B0→D0K*0 (¯¯¯B0→¯¯¯D0¯¯¯¯K*0) with K*0→K+π− (¯¯¯¯K*0→K−π+). Using a sample of 371×106 B¯¯¯B pairs collected with the BABAR detector at PEP-II, we constrain the angle γ as a function of rS, the magnitude of the average ratio between b→u and b→c amplitudes.Received 15 May 2008DOI:https://doi.org/10.1103/PhysRevD.79.072003©2009 American Physical Society

We report on a search for the process B+→¯¯¯¯K*0(892)K+ using 232×106 Υ(4S)→B¯¯¯B decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. From a signal yield of 25±13[stat]±7[syst] B+→¯¯¯¯K*0(892)(→K−π+)K+ events, we place an upper limit on the branching fraction B(B+→¯¯¯¯K*0(892)K+) of 1.1×10−6, at the 90% confidence level.Received 8 June 2007DOI:https://doi.org/10.1103/PhysRevD.76.071103©2007 American Physical Society

We study the decays B0 to J/psi pi+pi- and B+ to J/psi pi+pi0, including intermediate resonances, using a sample of 382 million BBbar pairs recorded by the BaBar detector at the PEP-II e+e- B factory. We measure the branching fractions B(B0 ->J/psi rho0) = (2.7 +/- 0.3 +/- 0.17) x 10-5 and B(B+ ->J/psi rho+) = (5.0 +/- 0.7 +/-0.31) x 10-5. We also set the following upper limits at the 90% confidence level: B(B0 -> J/psi pi+ \pi- non-resonant) < 1.2 x 10-5, B(B0 -> J/psi f_2(1270)) < 4.6 x 10-6, and B(B+ -> J/psi pi+ pi0 non-resonant) < 4.4 x 10-6. We measure the charge asymmetry in charged B decays to J/psi rho to be -0.11 +/- 0.12 +/- 0.08.

We present a measurement of the time-dependent CP-violating asymmetries in B0→K0Sπ0 decays based on 383×106 Υ(4S)→B¯¯¯B events collected by the BABAR experiment at the PEP-II asymmetric-energy B Factory at the Stanford Linear Accelerator Center. We measure the direct CP-violating asymmetry CK0Sπ0=0.24±0.15±0.03 and the CP-violating asymmetry in the interference between mixing and decay SK0Sπ0=0.40±0.23±0.03, where the first errors are statistical and the second are systematic. On the same sample, we measure the decay branching fraction, obtaining B(B0→K0π0)=(10.3±0.7±0.6)×10−6.Received 20 July 2007DOI:https://doi.org/10.1103/PhysRevD.77.012003©2008 American Physical Society

We report a measurement of the time-dependent CP-asymmetry parameters $\cal S$ and $\cal C$ in color-suppressed $B^0 \to D^{(*)0} h^0$ decays, where $h^0$ is a $\pi^0$, $\eta$, or $\omega$ meson, and the $D^0$ decays to one of the CP eigenstates $K^+K^-$, $K_S\pi^0$, or $K_S\omega$. The data sample consists of $383\times 10^{6}$ $\Upsilon(4S)\to B\bar{B}$ decays collected with the BABAR detector at the PEP-II asymmetric-energy $B$-factory at SLAC. The results are ${\cal S}= -0.56 \pm 0.23 \pm 0.05$ and ${\cal C}= -0.23\pm 0.16\pm 0.04$, where the first error is statistical and the second is systematic.

Branching fraction and asymmetry measurements of charmless $B^0\to K^{*0}h^+_1h^-_2$ ($h_{1,2}$ = $K$, $\pi$) decays are presented, using a data sample of 383 million $\Upsilon(4S) \to$ $B\bar{B$} decays collected with the BaBar detector at the PEP-II asymmetric-energy $B$-meson factory at SLAC. The results are: ${\cal B}$($B^0 \to K^{*0}K^+ K^-)$ = (27.5 $\pm$ 1.3 $\pm$ 2.2) $\times$ 10$^{-6}$, ${\cal B}$($B^0$ $\to$ $K^{*0}\pi^+ K^-$) = (4.6 $\pm$ 1.1 $\pm$ 0.8) $\times$ 10$^{-6}$ and ${\cal B}$($B^0$ $\to$ $K^{*0}\pi^+\pi^-$) = (54.5 $\pm$ 2.9 $\pm$ 4.3) $\times$ 10$^{-6}$. The first errors quoted are statistical and the second are systematic. An upper limit is set for ${\cal B}$($B^0$ $\to$ $K^{*0}K^+ \pi^-$) $<$ 2.2 $\times$ 10$^{-6}$ at 90% confidence level. We also present measurements of CP-violating asymmetries for the observed decays.

Using 383 x 10(6) BBover pairs from the BABAR data sample, we report results for branching fractions of six charged B-meson decay modes, where a charged kaon recoils against a charmless resonance decaying to KKover* or etapipi final states with mass in the range (1.2-1.8) GeV/c2. We observe a significant enhancement at the low KKover* invariant mass which is interpreted as B+-->eta(1475)K+, find evidence for the decay B+-->eta(1295)K+, and place upper limits on the decays B+-->eta(1405)K+, B+-->f1(1285)K+, B+-->f1(1420)K+, and B+-->phi(1680)K+.

We measure the absolute branching fraction for D0→K−π+ using partial reconstruction of ¯¯¯B0→D*+Xℓ−¯νℓ decays, in which only the charged lepton and the pion from the decay D*+→D0π+ are used. Based on a data sample of 230×106 B¯¯¯B pairs collected at the Υ(4S) resonance with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC, we obtain B(D0→K−π+)=(4.007±0.037±0.072)%, where the first uncertainty is statistical and the second is systematic.Received 18 April 2007DOI:https://doi.org/10.1103/PhysRevLett.100.051802©2008 American Physical Society

We present a measurement of the time-dependent $CP$ asymmetry for the neutral $B$-meson decay into the $CP=+1$ final state ${K}_{S}^{0}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$, with ${K}_{S}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$. We use a sample of approximately 227 million $B$-meson pairs recorded at the $\mathit{\ensuremath{\Upsilon}}(4S)$ resonance with the BABAR detector at the PEP-II $B$-Factory at SLAC. From an unbinned maximum likelihood fit, we extract the mixing-induced $CP$-violation parameter $S=0.72\ifmmode\pm\else\textpm\fi{}0.71\ifmmode\pm\else\textpm\fi{}0.08$ and the direct $CP$-violation parameter $C=0.23\ifmmode\pm\else\textpm\fi{}0.52\ifmmode\pm\else\textpm\fi{}0.13$, where the first uncertainty is statistical and the second systematic.

We search for the decays B0->rho0rho0, B0->rho0f0, and B0->f0f0 in a sample of about 384 million Upsilon(4S)->BBbar decays collected with the BABAR detector at the PEP-II asymmetric-energy e+e- collider at SLAC. We find evidence for B0->rho0rho0 with 3.5 sigma significance and measure the branching fraction BR = (1.07+-0.33+-0.19)10^-6 and longitudinal polarization fraction f_L = 0.87+-0.13+-0.04, where the first uncertainty is statistical, and the second is systematic. The uncertainty on the CKM unitarity angle alpha due to penguin contributions in B-> rho rho decays is 18 degrees at the 1 sigma level. We also set upper limits on the B0->rho0f0 and B0->f0f0 decay rates.

We determine the relative branching fractions of semileptonic $B$ decays to charmed final states. The measurement is performed on the recoil from a fully reconstructed $B$ meson in a sample of $362\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs collected at the $\ensuremath{\Upsilon}(4S)$ resonance with the BABAR detector. A simultaneous fit to a set of discriminating variables is performed on a sample of $\overline{B}\ensuremath{\rightarrow}DX{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}}$ decays to determine the contributions from the different channels. We measure $\ensuremath{\Gamma}({B}^{\ensuremath{-}}\ensuremath{\rightarrow}D{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})/\ensuremath{\Gamma}({B}^{\ensuremath{-}}\ensuremath{\rightarrow}DX{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})=0.227\ifmmode\pm\else\textpm\fi{}0.014\ifmmode\pm\else\textpm\fi{}0.016$, $\ensuremath{\Gamma}({B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{*}{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})/\ensuremath{\Gamma}({B}^{\ensuremath{-}}\ensuremath{\rightarrow}DX{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})=0.582\ifmmode\pm\else\textpm\fi{}0.018\ifmmode\pm\else\textpm\fi{}0.030$, and $\ensuremath{\Gamma}({B}^{\ensuremath{-}}\ensuremath{\rightarrow}{D}^{**}{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})/\ensuremath{\Gamma}({B}^{\ensuremath{-}}\ensuremath{\rightarrow}DX{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})=0.191\ifmmode\pm\else\textpm\fi{}0.013\ifmmode\pm\else\textpm\fi{}0.019$ for the charged $B$ sample, and $\ensuremath{\Gamma}(\overline{{B}^{0}}\ensuremath{\rightarrow}D{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})/\ensuremath{\Gamma}(\overline{{B}^{0}}\ensuremath{\rightarrow}DX{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})=0.215\ifmmode\pm\else\textpm\fi{}0.016\ifmmode\pm\else\textpm\fi{}0.013$, $\ensuremath{\Gamma}(\overline{{B}^{0}}\ensuremath{\rightarrow}{D}^{*}{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})/\ensuremath{\Gamma}(\overline{{B}^{0}}\ensuremath{\rightarrow}DX{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})=0.537\ifmmode\pm\else\textpm\fi{}0.031\ifmmode\pm\else\textpm\fi{}0.036$, and $\ensuremath{\Gamma}(\overline{{B}^{0}}\ensuremath{\rightarrow}{D}^{**}{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})/\ensuremath{\Gamma}(\overline{{B}^{0}}\ensuremath{\rightarrow}DX{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})=0.248\ifmmode\pm\else\textpm\fi{}0.032\ifmmode\pm\else\textpm\fi{}0.030$ for the neutral $B$ sample, where uncertainties are statistical and systematic, respectively.

We present a search for ${B}^{0}$ decays to charmless final states involving an $\ensuremath{\eta}$ meson, a charged pion, and a second charged pion or kaon. The data sample corresponds to $383\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs collected with the BABAR detector operating at the PEP-II asymmetric-energy $B$ factory at SLAC. We find no significant signals and determine the following 90% C.L. upper limits: $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{a}_{0}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})\ifmmode\times\else\texttimes\fi{}\mathcal{B}({a}_{0}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\eta}{\ensuremath{\pi}}^{\ensuremath{-}})&lt;3.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$, $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{a}_{0}^{\ensuremath{-}}{K}^{+})\ifmmode\times\else\texttimes\fi{}\mathcal{B}({a}_{0}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\eta}{\ensuremath{\pi}}^{\ensuremath{-}})&lt;1.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$, $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{a}_{0}(1450{)}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})\ifmmode\times\else\texttimes\fi{}\mathcal{B}({a}_{0}(1450{)}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\eta}{\ensuremath{\pi}}^{\ensuremath{-}})&lt;2.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$, $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{a}_{0}(1450{)}^{\ensuremath{-}}{K}^{+})\ifmmode\times\else\texttimes\fi{}\mathcal{B}({a}_{0}(1450{)}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\eta}{\ensuremath{\pi}}^{\ensuremath{-}})&lt;3.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$, $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}\ensuremath{\eta}{\ensuremath{\rho}}^{0})&lt;1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$, and $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}\ensuremath{\eta}{f}_{0}(980))\ifmmode\times\else\texttimes\fi{}\mathcal{B}({f}_{0}(980)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})&lt;0.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$.

We present an updated measurement of the $CP$-odd fraction and the time-dependent $CP$ asymmetries in the decay ${B}^{0}\ensuremath{\rightarrow}{D}^{*+}{D}^{*\ensuremath{-}}$ using $(383\ifmmode\pm\else\textpm\fi{}4)\ifmmode\times\else\texttimes\fi{}{10}^{6}B\overline{B}$ pairs collected with the BABAR detector. We determine the $CP$-odd fraction to be $0.143\ifmmode\pm\else\textpm\fi{}0.034(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.008(\mathrm{syst})$. The time-dependent $CP$ asymmetry parameters are determined to be ${C}_{+}=\ensuremath{-}0.05\ifmmode\pm\else\textpm\fi{}0.14(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.02(\mathrm{syst})$ and ${S}_{+}=\ensuremath{-}0.72\ifmmode\pm\else\textpm\fi{}0.19(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.05(\mathrm{syst})$. The nonzero value of the measured ${S}_{+}$ indicates the evidence of $CP$ violation at the $3.7\ensuremath{\sigma}$ confidence level.

The CMS Electromagnetic Calorimeter (ECAL) is made of about 75 000 lead tungstate crystals. The 61 200 crystals of the barrel part are read by Avalanche Photodiodes (APD) with internal amplification of the signal. Since the gain strongly depends on the bias voltage, the APDs require a very stable power supply system. To preserve the high energy resolution of the calorimeter, a stability of the bias voltage of the order of 10-4 is required over several months, a typical interval between absolute calibrations of the full read-out chain with physics events. This paper describes the high voltage power supply system developed for CMS ECAL and its performances as measured in laboratory tests and during test-beam operations of several modules of the calorimeter.

We present for the first time a measurement of the weak phase $2\ensuremath{\beta}+\ensuremath{\gamma}$ obtained from a time-dependent Dalitz plot analysis of ${B}^{0}\ensuremath{\rightarrow}{D}^{\ensuremath{\mp}}{K}^{0}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ decays. Using a sample of approximately $347\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs collected by the BABAR detector at the PEP-II asymmetric-energy storage rings and assuming the ratio $r$ of the $b\ensuremath{\rightarrow}u$ and $b\ensuremath{\rightarrow}c$ decay amplitudes to be 0.3, we obtain $2\ensuremath{\beta}+\ensuremath{\gamma}=(83\ifmmode\pm\else\textpm\fi{}53\ifmmode\pm\else\textpm\fi{}20)\ifmmode^\circ\else\textdegree\fi{}$ and the equivalent solution at $+180\ifmmode^\circ\else\textdegree\fi{}$. The magnitudes and phases for the resonances associated with the $b\ensuremath{\rightarrow}c$ transitions are also extracted from the fit.

We present the first observation of the decay ${B}^{+}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{+}{K}^{0}$, using a data sample of $348\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected at the $\ensuremath{\Upsilon}(4S)$ resonance with the BABAR detector. The branching fraction and charge asymmetry are measured to be $({8.0}_{\ensuremath{-}1.3}^{+1.4}\ifmmode\pm\else\textpm\fi{}0.6)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ and $(\ensuremath{-}12.2\ifmmode\pm\else\textpm\fi{}16.6\ifmmode\pm\else\textpm\fi{}2.0)%$, respectively, where the first uncertainty is statistical and the second is systematic. The charge asymmetry is defined by ${\mathcal{A}}_{\mathrm{ch}}=({\ensuremath{\Gamma}}_{{B}^{\ensuremath{-}}}\ensuremath{-}{\ensuremath{\Gamma}}_{{B}^{+}})/({\ensuremath{\Gamma}}_{{B}^{\ensuremath{-}}}+{\ensuremath{\Gamma}}_{{B}^{+}})$ with ${\ensuremath{\Gamma}}_{{B}^{\ifmmode\pm\else\textpm\fi{}}}$ the ${B}^{\ifmmode\pm\else\textpm\fi{}}$ decay rate. The significance of the observed branching fraction, including systematic uncertainties, is 7.9 standard deviations.

We present results of a search for the decays $B^0 \to \ell^+\ell^-\gamma$ ($\ell=e$, $\mu$). The search is performed using $320\times 10^{6}$ $B\bar{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the BABAR detector at the PEP-II $B$ Factory at SLAC. We find no significant signal and set the following branching fraction upper limits at the 90% confidence level: $\mathcal{B}(B^0\to e^+e^-\gamma)<1.2\times 10^{-7}$ and $\mathcal{B}(B^0\to \mu^+\mu^-\gamma)<1.5\times 10^{-7}$.

Hundreds of concurrent collisions per bunch crossing are expected at future hadron colliders. Precision timing calorimetry has been advocated as a way to mitigate the pileup effects and, thanks to their excellent time resolution, microchannel plates (MCPs) are good candidate detectors for this goal. We report on the response of MCPs, used as secondary emission detectors, to single relativistic particles and to electromagnetic showers. Several prototypes, with different geometries and characteristics, were exposed to particle beams at the INFN-LNF Beam Test Facility and at CERN. Their time resolution and efficiency are measured for single particles and as a function of the multiplicity of particles. Efficiencies between 50% and 90% to single relativistic particles are reached, and up to 100% in presence of a large number of particles. Time resolutions between 20 ps and 30 ps are obtained.

We report the observation of $\e^+e^-\to \phi\eta$ near $\sqrt{s}$ = 10.58 GeV with 6.5 $\sigma$ significance in the $K^+K^-\gamma\gamma$ final state in a data sample of 224 $fb^{-1}$ collected by the BaBar experiment at the PEP-II $e^+e^-$ storage rings. We measure the restricted radiation-corrected cross section to be $\sigma(\e^+e^- \to \phi \eta) =$$2.1\pm 0.4 (\mathrm{stat})\pm 0.1(\mathrm{syst}) \mathrm{fb}$ within the range $|\cos\theta^*| < 0.8$, where $\theta^*$ is the center-of-mass polar angle of the $\phi$ meson. The $\phi$ meson is required to be in the invariant mass range of 1.008 $< m_{\phi} <$ 1.035 \gevcc. The radiation-corrected cross section in the full $\cos\theta^*$ range is extrapolated to be $2.9\pm 0.5 (\mathrm{stat})\pm 0.1(\mathrm{syst}) \mathrm{fb}$.

A sampling calorimeter using cerium fluoride scintillating crystals as active material, interleaved with heavy absorber plates, and read out by wavelength-shifting (WLS) fibers is being studied as a calorimeter option for detectors at the upgraded High-Luminosity LHC (HL-LHC) collider at CERN. A prototype has been exposed to electron beams of different energies at the INFN Frascati (Italy) Beam Test Facility. This paper presents results from the studies performed on the prototype, such as signal amplitudes, light yield and energy resolution.

At the high luminosity LHC (HL-LHC) about 200 concurrent interactions are expected, with a spread between the interaction vertices of few centimeters in the beam direction and 200 ps in the collision time. A time of flight resolution of the order of 30 ps would be able to reduce neutral particles pile-up contamination at the calorimeter level of about one order of magnitude, restoring pile-up conditions similar to what is routinely sustained in the current run of the LHC . Micro-channel plates have been used in PMT configuration as fast charged particles detector (resolution of better than 20 ps have been achieved with commercial devices), however they are not particularly radiation tolerant, mostly due to the ion feedback on the photocathode. The possibility of using micro-channel plates without a photocathode (i-MCP) has been studied in several test beams. Different MCP geometries are compared with the goal to identify the optimal configuration. Efficiency of more then 70% with a time resolution of better than 40 ps are achieved for single charged particles, leading to an efficiency close to 100% for EM shower after few radiation lengths. This open the possibility to use i-MCPs as a timing layer in a sampling calorimeter or to use it in a pre-shower device independent from the calorimeter technology.

We search for decays of a B meson into a neutral D meson and a kaon, with the D meson decaying into K+pi-pi0. This final state can be reached through the b --> c transition B- -> D0K- followed by the doubly Cabibbo-suppressed D0 --> K+pi-pi0, or the b --> u transition B- --> D0bar K- followed by the Cabibbo-favored D0bar --> K+ pi-pi 0. The interference of these two amplitudes is sensitive to the angle gamma of the unitarity triangle. We present preliminary results based on 226 10^{6} e+e- --> Y(4s) --> BBbar events collected with the BABAR detector at SLAC. We find no significant evidence for these decays and we set a limit R_ADS =(BR(B- -->[K+pi-pi0]_D K-)+ BR(B+ --> [K-pi+pi0]_D K+))/(BR(B- -->[K-p i+pi0]_D K-)+ BR(B+ --> [K+pi-pi0]_D K+))<0.039 at 95% confidence level, which we translate with a Bayesian approach into r_B = |A(B- --> D0bar K-)|/|A(B- --> D0bar K-)| < 0.185 at 95% confidence level.

We have searched for the rare decay B+→D+sπ0. The analysis is based on a sample of 232×106 Υ(4S)→B¯¯¯B decays collected with the BABAR detector at the SLAC PEP-II e+e− storage ring. We find 19.6 signal events, corresponding to a significance of 4.7σ. The extracted signal yield including statistical and systematic uncertainties is 20.1+6.8+0.4−6.0−1.5, and we measure B(B+→D+sπ0)=(1.5+0.5−0.4±0.1±0.2)×10−5, where the first uncertainty is statistical, the second is systematic, and the last is due to the uncertainty on the D+s decay and its daughter decay branching fractions.Received 16 November 2006DOI:https://doi.org/10.1103/PhysRevLett.98.171801©2007 American Physical Society

We present measurements of the time-dependent CP-violating asymmetries in B0→K0SK0SK0S decays based on 384×106 Υ(4S)→B¯¯¯B decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We obtain the CP asymmetry parameters C=0.02±0.21±0.05 and S=−0.71±0.24±0.04, where the first uncertainties are statistical and the second systematic. These results are consistent with standard model expectations.Received 27 February 2007DOI:https://doi.org/10.1103/PhysRevD.76.091101©2007 American Physical Society

We present a search for $B$ decays to a charged scalar meson ${a}_{0}^{+}$ and a ${\ensuremath{\pi}}^{0}$ where the ${a}_{0}^{+}$ decays to an $\ensuremath{\eta}$ meson and a ${\ensuremath{\pi}}^{+}$. The analysis was performed on a data sample consisting of $383\ifmmode\times\else\texttimes\fi{}{10}^{6}$ $B\overline{B}$ pairs collected with the BABAR detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. We find no significant signal and set an upper limit on the product branching fraction $\mathcal{B}({B}^{+}\ensuremath{\rightarrow}{a}_{0}^{+}{\ensuremath{\pi}}^{0})\ifmmode\times\else\texttimes\fi{}\mathcal{B}({a}_{0}^{+}\ensuremath{\rightarrow}\ensuremath{\eta}{\ensuremath{\pi}}^{+})$ of $1.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ at the 90% confidence level.

A prototype for a sampling calorimeter made out of cerium fluoride crystals interleaved with tungsten plates, and read out by wavelength-shifting fibres, has been exposed to beams of electrons with energies between 20 and 150 GeV, produced by the CERN Super Proton Synchrotron accelerator complex. The performance of the prototype is presented and compared to that of a Geant4 simulation of the apparatus. Particular emphasis is given to the response uniformity across the channel front face, and to the prototype׳s energy resolution.

I-MCP is an R&D project aimed at the exploitation of secondary emission of electrons from the surface of micro-channel plates (MCP) for single ionizing particles and fast timing of showers in high rate environments. Results from tests with electrons with energies up to 50 GeV of MCP devices with different characteristics are presented. In particular detection efficiency and time resolution are measured for a range of MCP prototypes: different MCP channel diameter and layers configuration are studied. Devices operated in I-MCP configuration, where the particle detection proceed through direct ionization of the MCP layers, are studied in comparison with the more usual PMT-MCP configuration. The results show efficiencies up to 70% for single charge particle detection for I-MCP devices with a time resolution of about 40 ps. The efficiency raise to 100% in response to high energy electromagnetic showers.

Future high rate hadron colliders are expected to have hundreds of concurrent proton-proton interactions in the same bunch crossing, deteriorating the energy resolution and identification capabilities of calorimeters. The possibility to distinguish neutral particles coming from different interaction vertices is being pursued as a tool to reduce pile-up contamination in calorimeters, and restore optimal performance. A time of flight resolution of the order of 20 ps will be able to reduce neutral particles pile-up contamination at the calorimeter level by about one order of magnitude, restoring pile-up conditions similar to what is routinely sustained in the current run of the LHC . Micro-channel plates (MCP) can be used in PMT configuration as fast charged particles detector (resolution of better then 30 ps can be achieved with commercial devices). However they are not particularly radiation tolerant, mostly due to the ion feedback on the photocathode. The possibility of using micro-channel plates without a photocathode (i-MCP) has been studied in several test beams. Different MCP geometries are compared with the goal to identify the optimal configuration. Efficiency of more than 70% with a time resolution of better than 40 ps are achieved for single charged particles, leading to an efficiency close to 100% for EM shower after few radiation lengths. This opens the possibility to use i-MCPs as a timing layer in a sampling calorimeter or to use it in a pre-shower device independent from the calorimeter technology. Preliminary results on the radiation hardness of the i-MCP configuration will be also presented.

A sampling calorimeter using cerium fluoride scintillating crystals as active material, interleaved with absorber plates made of tungsten, and read out by wavelength-shifting fibres has been tested with high-energy electron beams at the CERN SPS H4 beam line, as well as with lower-energy beams at the INFN Frascati Beam Test Facility in Italy. Energy resolution studies revealed a low stochastic term (<10%/E). This result, combined with high radiation hardness of the material used, marks this sampling calorimeter as a good candidate for the detectors׳ forward regions during the high luminosity phase of LHC.

We have searched for prompt production of χc1, χc2 and X(3872) in continuum e+e− annihilations using a 386 fb−1 data sample collected around √s=10.6 GeV with the BABAR detector using the γJ/ψ decay mode. After accounting for the feed-down from ψ(2S)→γχc1,2, no significant signal for prompt χc1,2 production is observed. We present improved upper limits at 90% confidence level on the production cross sections of 77 fb for χc1 and 79 fb for χc2, for events where the χc momentum exceeds 2.0 GeV and there are at least three additional charged tracks. These limits are consistent with NRQCD predictions. We also set an upper limit on the prompt production of X(3872) through the decay X(3872)→γJ/ψ.Received 12 July 2007DOI:https://doi.org/10.1103/PhysRevD.76.071102©2007 American Physical Society

The CMS electromagnetic calorimeter (ECAL) comprises 75848 scintillating lead tungstate crystals. 61200 crystals are contained in the ECAL Barrel section and are read out by avalanche photodiode (APD) with internal gain of about 50. This gain is achieved with a high voltage (HV) of about 400 Volts. The gain stability requirement implies a supply voltage stable to within 0.01%. We describe our experience with the installed Barrel HV power supply system, which has been used for data taking since 2008.

The High-Luminosity phase of the Large Hadron Collider at CERN (HL-LHC) poses stringent requirements on calorimeter performance in terms of resolution, pileup resilience and radiation hardness. A tungsten-CeF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> sampling calorimeter is a possible option for the upgrade of current detectors. A prototype, read out with different types of wavelength-shifting fibers, has been built and exposed to high energy electrons, representative for the particle energy spectrum at HL-LHC, at the CERN SPS H4 beam line. This paper shows the performance of the prototype, mainly focussing on energy resolution and uniformity. A detailed simulation has been also developed in order to compare with data and to extrapolate to different configurations to be tested in future beam tests. Additional studies on the calorimeter and the R&D projects ongoing on the various components of the experimental setup will be also discussed.

In this dissertation, a measurement of CP-violating effects in decays of neutral B meson is presented. The data sample for this measurement consists of about 88 million {Upsilon}(4S) {yields} B{bar B} decays collected between 1999 and 2002 with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider, located at the Stanford Linear Accelerator Center. One neutral B meson is fully reconstructed in the CP eigenstates J/{psi} K{sub S}{sup 0}, {psi}(2S)K{sub S}{sup 0}, {chi}{sub c1}K{sub S}{sup 0}, and {eta}{sub c}K{sub S}{sup 0}, or in the flavor eigenstates D(*){sup -} {pi}{sup +}/{rho}{sup +}/a{sub 1}{sup +} and J/{psi} K*{sup 0} (K*{sup 0} {yields} K{sup +}{pi}{sup -}). The other B meson is determined to be either a B{sup 0} or a {bar B}{sup 0}, at the time of its decay, from the properties of its decay products. The proper time {Delta}t elapsed between the decay of the two mesons is determined by reconstructing their decay vertices, and by measuring the distance between them. The CP asymmetry amplitude sin2{beta} is determined by the distributions of {Delta}t in events with a reconstructed B meson in CP eigenstates. The detector resolution and the b-flavor-tagging parameters are constrained by the {Delta}t distributions of events with a fully reconstructed flavor eigenstate. From a simultaneous maximum-likelihood fit to the {Delta}t distributions of all selected events in CP and flavor eigenstates, the value of sin2{beta} is measured to be 0.755 {+-} 0.074(stat) {+-} 0.030(syst). This value is in agreement with the Standard Model prediction, and represents a successful test of the Kobayashi-Maskawa mechanism of CP violation.

IMCP is an R&D project aimed at the exploitation of secondary emission of electrons from the surface of microchannel plates (MCP) for fast timing of showers in high rate environments. The usage of MCPs in “ionisation” mode has long been proposed and is used extensively in ion time-of-flight mass spectrometers. What has not been investigated in depth is their use to detect the ionizing component of showers. The fast time resolution of MCPs exceeds anything that has been previously used in calorimeters and, if exploited effectively, could aid in the event reconstruction at high luminosity colliders. Results from tests with electrons with energies up to 150 GeV of MCP devices with different characteristics will be presented, in particular detection efficiency and time resolution.