Gail Hanson

We have observed a very sharp peak in the cross section for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{hadrons}, {e}^{+}{e}^{\ensuremath{-}}$, and possibly ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ at a center-of-mass energy of 3.105\ifmmode\pm\else\textpm\fi{}0.003 GeV. The upper limit to the full width at half-maximum is 1.3 MeV.

We have found events of the form e++e−→e±+μ∓+missingenergy, in which no other charged particles or photons are detected. Most of these events are detected at or above a center-of-mass energy of 4 GeV. The missing-energy and missing-momentum spectra require that at least two additional particles be produced in each event. We have no conventional explanation for these events.Received 18 August 1975DOI:https://doi.org/10.1103/PhysRevLett.35.1489©1975 American Physical Society

We present evidence, from a study of multihadronic final states produced in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation at center-of-mass energies between 3.90 and 4.60 GeV, for the production of a new neutral state with mass 1865\ifmmode\pm\else\textpm\fi{}15 MeV/${\mathit{c}}^{2}$ and decay width less than 40 MeV/${\mathit{c}}^{2}$ that decays to ${K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}$ and ${K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}$. The recoil-mass spectrum for this state suggests that it is produced only in association with systems of comparable or larger mass.

We have observed a second sharp peak in the cross section for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{hadrons}$ at a center-of-mass energy of 3.695\ifmmode\pm\else\textpm\fi{}0.004 GeV. The upper limit of the full width at half-maximum is 2.7 MeV.

We have found evidence for jet structure in ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{hadrons}$ at center-of-mass energies of 6.2 and 7.4 GeV. At 7.4 GeV the jet-axis angular distribution integrated over azimuthal angle was determined to be proportional to $1+(0.78\ifmmode\pm\else\textpm\fi{}0.12){cos}^{2}\ensuremath{\theta}$.

We report evidence for the production of a new narrow charged state in e+e− annihilation at a center-of-mass energy of 4.03 GeV. This state, which has a mass of 1876± 15 MeV/c2, is observed in the exotic channel K∓π±π±, but not in the nonexotic channel K∓π+π−. It is produced primarily in association with a system of mass 2.01±0.02 GeV/c2. These characteristics are just those expected of a charged charmed meson.Received 21 July 1976DOI:https://doi.org/10.1103/PhysRevLett.37.569©1976 American Physical Society

The status of the research on muon colliders is discussed and plans are outlined for future theoretical and experimental studies. Besides continued work on the parameters of a 3-4 and 0.5 TeV center-of-mass (CoM) energy collider, many studies are now concentrating on a machine near 0.1 TeV (CoM) that could be a factory for the s-channel production of Higgs particles. We discuss the research on the various components in such muon colliders, starting from the proton accelerator needed to generate pions from a heavy-Z target and proceeding through the phase rotation and decay ($\pi \to \mu \nu_{\mu}$) channel, muon cooling, acceleration, storage in a collider ring and the collider detector. We also present theoretical and experimental R & D plans for the next several years that should lead to a better understanding of the design and feasibility issues for all of the components. This report is an update of the progress on the R & D since the Feasibility Study of Muon Colliders presented at the Snowmass'96 Workshop [R. B. Palmer, A. Sessler and A. Tollestrup, Proceedings of the 1996 DPF/DPB Summer Study on High-Energy Physics (Stanford Linear Accelerator Center, Menlo Park, CA, 1997)].

The total cross section for hadron production by ${e}^{+}{e}^{\ensuremath{-}}$ annihilation has been measured at center-of-mass energies between 2.4 and 5.0 GeV. Aside from the very narrow resonances $\ensuremath{\psi}(3105)$ and $\ensuremath{\psi}(3695)$, the cross section varies between 32 and 17 nb over this region with structure in the vicinity of 4.1 GeV.

We have observed a radiative transition from the ψ to a state decaying into KSK±π∓, with mass M = 1.44−0.015+0.01 GeV/c2 and width Γ = 0.05−0.02+0.03 GeV/c2. We tentatively identify this state as the E(1420). Assuming that this state is an isospin singlet, we have determined the branching fraction product B(ψ → γE) × B(E × KKπ) = (3.6 ± 1.4) × 10−3.

We observe a resonance in the total cross section for hadron production in e+e− annihilation at a mass of 3772±6 MeV/c2 having a total width of 28±5 MeV/c2 and a partial width to electron pairs of 370±90 eV/c2.Received 27 June 1977DOI:https://doi.org/10.1103/PhysRevLett.39.526©1977 American Physical Society

We present a study of the decay properties of charmed D mesons produced near the peak of the ψ''(3770) resonance in e+e− annihilation. Branching fractions for nine Cabibbo-favored and three Cabibbo-suppressed decay modes are presented along with upper limits on one additional Cabibbo-favored and four additional Cabibbo-suppressed decay modes. A study of Kππ-decay-mode Dalitz plots reveals a large quasi-two-body pseudoscalar-vector component for the D0 decays and an apparent nonuniform population on the Dalitz plot for the D+ decay into K−π+π+. Using tagged events, we measure the charged-particle multiplicity and strange-particle content of D decays. A measurement of the D+ and D0 semileptonic decay fractions indicates that the D+ has a significantly longer lifetime than the D0.Received 11 February 1981DOI:https://doi.org/10.1103/PhysRevD.24.78©1981 American Physical Society

We present the properties of 105 events of the form e+ + e− → e+- + μ∓ + missing energy, in which no other charged particles or photons are detected. The simplesthypothesis compatible with all the data is that these events come from the production of a pair of heavy leptons, the mass of the lepton being in the range 1.6 to 2.0 GeV/c2

The average lifetime of bottom hadrons was measured with the Mark II vertex detector at the storage ring PEP. The lifetime was determined by measuring the impact parameters of leptons produced in bottom decays. τb=(12.0+4.5−3.6±3.0)×10−13 sec was found.Received 2 August 1983DOI:https://doi.org/10.1103/PhysRevLett.51.1316©1983 American Physical Society

We have measured the mass of the Z boson to be 91.14±0.12 GeV/c2, and its width to be 2.42+0.45−0.35 GeV. If we constrain the visible width to its standard-model value, we find the partial width to invisible decay modes to be 0.46±0.10 GeV, corresponding to 2.8±0.6 neutrino species, with a 95%-confidence-level upper limit of 3.9.Received 12 October 1989DOI:https://doi.org/10.1103/PhysRevLett.63.2173©1989 American Physical Society

We present a new high-statistics measurement of the cross section for the process e+e−→e+e−π+π− at a center-of-mass energy of 29 GeV for invariant pion-pair masses M(π+π−) between 350 MeV/c2 and 1.6 GeV/c2. We observe the f2(1270) and measure its radiative width to be 3.15±0.04±0.39 keV. We also observe an enhancement in the π+π− spectrum near 1 GeV. General agreement is found with unitarized models of the γγ→π+π− reaction that include final-state interactions.Received 27 March 1990DOI:https://doi.org/10.1103/PhysRevD.42.1350©1990 American Physical Society

We present cross sections for e+e−→hadrons, e+e−, and μ+μ− near 3095 MeV. The ψ(3095) resonance is established as having an assignment JPC=1−−. The mass is 3095 ±4 MeV. The partial width to electrons is Γe=4.8±0.6 keV and the total width Γ=69±15 keV. Total rates and interference measurements for the lepton channels are in accord with μ−e universality.Received 7 April 1975DOI:https://doi.org/10.1103/PhysRevLett.34.1357©1975 American Physical Society

We have measured the total cross section for electron-positron annihilation into three or more hadrons, with at least two charged particles in the final state. The measurement was made at a center-of-mass energy of 4 GeV with a $2\ensuremath{\pi}\ensuremath{-}\mathrm{s}\mathrm{r}$ nonmagnetic detector. With 88 events detected, we obtain a model-independent lower limit on the hadron production cross section of 9.6 \ifmmode\pm\else\textpm\fi{} 1.4 nb; a calculation of detection efficiency based on invariant phase-space production of pions leads to a total cross section of 26 \ifmmode\pm\else\textpm\fi{} 6 nb. This cross section is 4.7 \ifmmode\pm\else\textpm\fi{} 1.1 times the theoretical total cross section for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$. The average charged multiplicity is $\overline{n}=4.2\ifmmode\pm\else\textpm\fi{}0.6$.

We have studied momentum spectra for D0 (D0) and D± mesons produced near 4 GeV in e+e− annihilation and find that production is dominated by two-body reactions involving D and D∗ states where the D∗ (charged and neutral) have masses near 2.01 GeV/c2. A detailed study of D momentum spectra near Ecm = 4.028 GeV allows determination of masses and branching ratios of D and D∗ states. Lastly we find that events containing a D0 meson conserve strangeness, thus establishing upper limits on D0-D0 mixing and on the effects of charm changing neutral currents.

We observe a resonancelike structure in the total cross section for hadron production by ${e}^{+}{e}^{\ensuremath{-}}$ colliding beams at a mass of 4414 \ifmmode\pm\else\textpm\fi{} 7 MeV having a total width $\ensuremath{\Gamma}=33\ifmmode\pm\else\textpm\fi{}10$ MeV. From the area under this resonance, we deduce the partial width to electron pairs to be ${\ensuremath{\Gamma}}_{\mathrm{ee}}=440\ifmmode\pm\else\textpm\fi{}140$ eV. Further structure of comparable width is present near 4.1 GeV.

We describe the status of our effort to realize a first neutrino factory and the progress made in understanding the problems associated with the collection and cooling of muons towards that end. We summarize the physics that can be done with neutrino factories as well as with intense cold beams of muons. The physics potential of muon colliders is reviewed, both as Higgs Factories and compact high energy lepton colliders. The status and timescale of our research and development effort is reviewed as well as the latest designs in cooling channels including the promise of ring coolers in achieving longitudinal and transverse cooling simultaneously. We detail the efforts being made to mount an international cooling experiment to demonstrate the ionization cooling of muons.

We have measured the mass of the Z boson to be 91.11±0.23 GeV/c2, and its width to be 1.61+0.60−0.43 GeV. If we constrain the visible width to its standard-model value, we find the partial width to invisible decay modes to be 0.62±0.23 GeV, corresponding to 3.8±1.4 neutrino species.Received 24 July 1989DOI:https://doi.org/10.1103/PhysRevLett.63.724©1989 American Physical Society

Measurements of ψ(3097) and ψ′(3686) branching fractions for selected hadronic decays are presented. The ratio of ψ′ to ψ branching fractions for these decays is consistent with the ratio of branching fractions to lepton pairs, with the exception of the decays to pπ and K∗K for which this ratio is substantially smaller.Received 25 April 1983DOI:https://doi.org/10.1103/PhysRevLett.51.963©1983 American Physical Society

A peak in the $p{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ and $\overline{p}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ invariant-mass spectra at 2.285\ifmmode\pm\else\textpm\fi{}0.006 GeV/${\mathit{c}}^{2}$ is observed, which is associated with the lowest-lying charmed baryon (${\ensuremath{\Lambda}}_{c}$). A cross section times branching ratio of 0.037\ifmmode\pm\else\textpm\fi{}0.012 nb at ${E}_{\mathrm{c}.\mathrm{m}.}=5.2$ GeV is measured with a substantial fraction of the events produced with an equal recoiling mass. New measurements of inclusive $p$ and $\ensuremath{\Lambda}$ cross sections are also presented, allowing an estimate of the branching ratio $B({\ensuremath{\Lambda}}_{c}\ensuremath{\rightarrow}p{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})=0.022\ifmmode\pm\else\textpm\fi{}0.010$.

We have observed the decay ${{D}^{*}}^{+}\ensuremath{\rightarrow}{D}^{0}{\ensuremath{\pi}}^{+}$ and have measured its $Q$ value to be 5.7\ifmmode\pm\else\textpm\fi{}0.5 MeV. The decay width of the ${{D}^{*}}^{+}$ is less than 2.0 MeV/${\mathit{c}}^{2}$. The observation of ${{D}^{*}}^{+}\ensuremath{\rightarrow}({K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}){\ensuremath{\pi}}^{+}$ but not of ${{D}^{*}}^{+}\ensuremath{\rightarrow}({K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}){\ensuremath{\pi}}^{+}$ sets an upper limit on the amount of ${D}^{0}\ensuremath{-}{\overline{D}}^{0}$ mixing.

From a study of $D$ mesons produced in the decay $\ensuremath{\psi}(3772)\ensuremath{\rightarrow}D\overline{D}$, we have determined the masses of the ${D}^{0}$ and ${D}^{+}$ mesons to be 1863.3\ifmmode\pm\else\textpm\fi{}0.9 ${\mathrm{M}\mathrm{e}\mathrm{V}/\mathit{c}}^{2}$ and 1868.3\ifmmode\pm\else\textpm\fi{}0.9 ${\mathrm{M}\mathrm{e}\mathrm{V}/\mathit{c}}^{2}$, respectively. Under the assumption that the $\ensuremath{\psi}(3772)$ has a definite isospin and decays only to $D\overline{D}$, the ${D}^{0}$ branching fractions to ${K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$, ${\overline{K}}^{0}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, and ${K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ are (2.2\ifmmode\pm\else\textpm\fi{}0.6)%, (4.0 \ifmmode\pm\else\textpm\fi{} 1.3)%, and (3.2\ifmmode\pm\else\textpm\fi{}1.1)% and the ${D}^{+}$ branching fractions to ${\overline{K}}^{0}{\ensuremath{\pi}}^{+}$ and ${K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{+}$ are (1.5\ifmmode\pm\else\textpm\fi{}0.6)% and (3.9\ifmmode\pm\else\textpm\fi{}1.0)%.

The OPAL experiment at the CERN LEP collider recently upgraded its silicon strip microvertex detector from one coordinate readout (φ only) to two coordinate readout (φ and z). This allows three dimensional vertex reconstruction and should improve lifetime measurements as well as b quark jet identification. This paper describes the new microvertex detector system with emphasis on the novel techniques and new components used to obtain the second coordinate information. These include the use of back-to-back single-sided detectors with orthogonally oriented readout strips, a gold printed circuit on a thin glass substrate to route the z strip signals to the electronics at the end of the detector, and the use of MX7 readout chips. Results on the performance of the new detector are presented.

The reactions ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$ and ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ have been measured at center-of-mass energies 3.0, 3.8, and 4.8 GeV and production angles of $50\ifmmode^\circ\else\textdegree\fi{}<\ensuremath{\theta}<130\ifmmode^\circ\else\textdegree\fi{}$ over all azimuthal angles. Agreement with quantum electrodynamics is excellent. New limits for cutoff parameters in quantum-electrodynamic-breakdown models are given.

Measurements of multihadron production in e+e− annihilation at center-of-mass energies between 2.6 and 7.8 GeV are presented. Aside from the narrow resonances ψ(3095) and ψ(3684), the total hadronic cross section is found to be approximately 2.7 times the cross section for the production of muon pairs at c.m. energies below 3.7 GeV and 4.3 times the muon-pair cross section at c.m. energies above 5.5 GeV. Complicated structure is found at intermediate energies. Charged-particle multiplicities and inclusive momentum distributions are presented.Received 12 April 1982DOI:https://doi.org/10.1103/PhysRevD.26.969©1982 American Physical Society

We present experimental evidence for the existence of the decay ψ(3684)→γχ, χ→4π±, 6π±, π+π−K+K−, π+π−, and K+K−. There is clear evidence for at least two χ states, one at 3.41 ± 0.01 GeV/c2 and the other at 3.53±0.02 GeV/c2. The χ(3410) decays into ππ and KK and thus must have even spin and parity.Received 11 August 1975DOI:https://doi.org/10.1103/PhysRevLett.35.821©1975 American Physical Society

We observe $\ensuremath{\psi}(3684)$ to decay into $\ensuremath{\psi}(3095)$ with a branching ratio of 0.57 \ifmmode\pm\else\textpm\fi{} 0.08. The branching ratio for the particular decay mode $\ensuremath{\psi}(3095)+{\ensuremath{\pi}}^{+}+{\ensuremath{\pi}}^{\ensuremath{-}}$ is measured to be 0.32 \ifmmode\pm\else\textpm\fi{} 0.04. Remaining decays leading to $\ensuremath{\psi}(3095)$ are largely, but not entirely, accounted for by the mode $\ensuremath{\psi}(3095)+{\ensuremath{\pi}}^{0}+{\ensuremath{\pi}}^{0}$ if the two pions in this decay are in a state of zero isospin.

We present measurements of inclusive anomalous muon production in e+e− annihilations in three energy ranges. In all three ranges we observe a large anomalous muon production rate in two-prong events which is compatible with the expected decays of pairs of heavy leptons. In the highest energy range there is also appreciable anomalous muon production in multiprong events which, due to its magnitude and momentum dependence, must come in part from a source other than a heavy lepton.Received 8 November 1976DOI:https://doi.org/10.1103/PhysRevLett.38.117©1977 American Physical Society

Events of the type ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}{\ensuremath{\eta}}^{\ensuremath{'}}(958)$ have been observed with the Mark II detector at SPEAR by detecting the decay mode ${\ensuremath{\eta}}^{\ensuremath{'}}\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}\ensuremath{\gamma}$. From the observed cross section and known branching fractions of the ${\ensuremath{\eta}}^{\ensuremath{'}}$ is ${\ensuremath{\Gamma}}_{\ensuremath{\gamma}\ensuremath{\gamma}}=5.9\ifmmode\pm\else\textpm\fi{}1.6\ifmmode\pm\else\textpm\fi{}1.2$ keV and the total width is $\ensuremath{\Gamma}=300\ifmmode\pm\else\textpm\fi{}90\ifmmode\pm\else\textpm\fi{}60$ keV (statistical and systematic errors).

We have measured the electroproduction of hadrons from nuclei and compare it to the electroproduction from deuterium. We find an attenuation of the forward component which increases with $A$. The attenuation is less for lower hadronic momenta, but is not a strong function of the other electroproduction variables.

We have observed an azimuthal asymmetry in inclusive hadron

.Approximately 438 pb-1 of e + e- data from the OPAL detector, taken with the LEP collider running at centre-of-mass energies of 192-209 GeV, are analyzed to search for evidence of chargino pair production, \({\mathrm{e}}^ + {\mathrm{e}}^-\to\tilde\chi^ + _1\tilde\chi^-_1\), or neutralino associated production, \({\mathrm{e}}^ + {\mathrm{e}}^-\to\tilde\chi^0_2\tilde\chi^0_1\). Limits are set at the 95% confidence level on the product of the cross-section for the process \({\mathrm{e}}^ + {\mathrm{e}}^-\to\tilde\chi^ + _1\tilde\chi^-_1\) and its branching ratios to topologies containing jets and missing energy, or jets with a lepton and missing energy, and on the product of the cross-section for \({\mathrm{e}}^ + {\mathrm{e}}^-\to\tilde\chi^0_2\tilde\chi^0_1\) and its branching ratio to jets. R-parity conservation is assumed throughout this paper. When these results are interpreted in the context of the Constrained Minimal Supersymmetric Standard Model, limits are also set on the masses of the \(\tilde\chi^{\pm}_1, \tilde\chi^0_1\) and \(\tilde\chi^0_2\), and regions of the parameter space of the model are ruled out. Nearly model-independent limits are also set at the 95% confidence level on \(\sigma({\mathrm{e}}^ + {\mathrm{e}}^-\to\tilde\chi^ + _1\tilde\chi^-_1)\) with the assumption that each chargino decays via a W boson, and on \(\sigma({\mathrm{e}}^ + {\mathrm{e}}^-\to\tilde\chi^0_2\tilde\chi^0_1)\) with the \(\tilde\chi^0_2\) assumed to decay via a Z0.

A study of b quark hadronisation is presented using inclusively reconstructed B hadrons in about four million hadronic Z decays recorded in 1992-2000 with the OPAL detector at LEP. The data are compared to different theoretical models, and fragmentation function parameters of these models are fitted. The average scaled energy of weakly decaying B hadrons is determined to be <xe>=0.7193+-0.0016(stat)+0.0036-0.0031(syst)

The production of the charmed meson state ${D}^{*+}$ has been observed in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation at 29 GeV. The fragmentation function for charmed quarks appears to be peaked about $z=0.5$.

We present a measurement of the cross section for the reaction e+e− → e+e−π+π−π+π−at SPEAR. This channel is found to be large and dominated by the process γγ → ϱ0ϱ0 → π+π−π+π−. The cross section, which is small just above the four-pion threshold, exhibits a large enhancement near the ϱ0ϱ0 threshold.

We present evidence for the existence of an intermediate state observed in the decay sequence $\ensuremath{\psi}(3684)\ensuremath{\rightarrow}\ensuremath{\psi}(3095)\ensuremath{\gamma}\ensuremath{\gamma}$. The mass of the state is either 3500 \ifmmode\pm\else\textpm\fi{} 10 or 3270 \ifmmode\pm\else\textpm\fi{} 10 MeV. The branching fraction of the sequence is (3.6 \ifmmode\pm\else\textpm\fi{} 0.7)%.

In a study of ${\ensuremath{\psi}}^{\ensuremath{'}}$ (3684) radiative decays with the Mark II detector at SPEAR, the decay sequence ${\ensuremath{\psi}}^{\ensuremath{'}}\ensuremath{\rightarrow}\ensuremath{\gamma}{\ensuremath{\eta}}_{c}$ (2980) is observed, with the ${\ensuremath{\eta}}_{c}$ (2980) decaying into several completely reconstructed hadronic modes. A mass $M=2980\ifmmode\pm\else\textpm\fi{}8$ ${\mathrm{M}\mathrm{e}\mathrm{V}/\mathit{c}}^{2}$ and a width $\ensuremath{\Gamma}&lt;40$ ${\mathrm{M}\mathrm{e}\mathrm{V}/\mathit{c}}^{2}$ (90%) confidence level) are obtained, and estimates of some of the decay branching ratios are presented.

We have observed anomalous electron production in multiprong events produced by ${e}^{+}{e}^{\ensuremath{-}}$ annihilation at the $\ensuremath{\psi}(3772)$. For electron momenta greater than 300 MeV/c we measure an anomalous electron production cross section of 1.1 \ifmmode\pm\else\textpm\fi{} 0.3 nb. The measured spectrum is consistent with that expected for semileptonic $D$ decay. With reasonable assumptions we find the branching ratio for $D$ decay to an electron plus additional particles, averaged over the neutral and charged $D$, to be (7.2\ifmmode\pm\else\textpm\fi{}2.8)%.

Cross sections for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{hadrons}, {e}^{+}{e}^{\ensuremath{-}}, \mathrm{and} {\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ near 3684 MeV are presented. The $\ensuremath{\psi}(3684)$ resonance is established as having the assignment ${J}^{\mathrm{PC}}={1}^{\ensuremath{-}\ensuremath{-}}$. The mass is 3684 \ifmmode\pm\else\textpm\fi{} 5 MeV. The partial width for decay to electrons is ${\ensuremath{\Gamma}}_{e}=2.1\ifmmode\pm\else\textpm\fi{}0.3$ keV and the total width is $\ensuremath{\Gamma}=228\ifmmode\pm\else\textpm\fi{}56$ keV.

This report summarizes the work of the Energy Frontier Higgs Boson working group of the 2013 Community Summer Study (Snowmass). We identify the key elements of a precision Higgs physics program and document the physics potential of future experimental facilities as elucidated during the Snowmass study. We study Higgs couplings to gauge boson and fermion pairs, double Higgs production for the Higgs self-coupling, its quantum numbers and $CP$-mixing in Higgs couplings, the Higgs mass and total width, and prospects for direct searches for additional Higgs bosons in extensions of the Standard Model. Our report includes projections of measurement capabilities from detailed studies of the Compact Linear Collider (CLIC), a Gamma-Gamma Collider, the International Linear Collider (ILC), the Large Hadron Collider High-Luminosity Upgrade (HL-LHC), Very Large Hadron Colliders up to 100 TeV (VLHC), a Muon Collider, and a Triple-Large Electron Positron Collider (TLEP).

Charged-particle tracking in the international Muon Ionisation Cooling Experiment (MICE) will be performed using two solenoidal spectrometers, each instrumented with a tracking detector based on 350 {\mu}m diameter scintillating fibres. The design and construction of the trackers is described along with the quality-assurance procedures, photon-detection system, readout electronics, reconstruction and simulation software and the data-acquisition system. Finally, the performance of the MICE tracker, determined using cosmic rays, is presented.

Cachexia is a debilitating skeletal muscle wasting condition for which we currently lack effective treatments. In the context of cancer, certain chemotherapeutics cause DNA damage and cellular senescence. Senescent cells exhibit chronic activation of the transcription factor NF-κB, a known mediator of the proinflammatory senescence-associated secretory phenotype (SASP) and skeletal muscle atrophy. Thus, targeting NF-κB represents a logical therapeutic strategy to alleviate unintended consequences of genotoxic drugs. Herein, we show that treatment with the IKK/NF-κB inhibitor SR12343 during a course of chemotherapy reduces markers of cellular senescence and the SASP in liver, skeletal muscle, and circulation and, correspondingly, attenuates features of skeletal muscle pathology. Lastly, we demonstrate that SR12343 mitigates chemotherapy-induced reductions in body weight, lean mass, fat mass, and muscle strength. These findings support senescent cells as a promising druggable target to counteract the SASP and skeletal muscle wasting in the context of chemotherapy.

Quark and gluon jets with equal energies are identified in three-jet hadronicZ 0 events, using reconstructed secondary vertices from heavy quark decay in conjunction with energy ordering of the jets to anti-tag the gluon jets. Selection of jets from a symmetric event topology allows their properties to be compared in a simple and direct manner. The jets under study have an energy of about 24 GeV. It is observed that gluon jets have a larger angular width than quark jets and yield a softer particle energy spectrum. Correspondingly, the mean particle multiplicity is found to be larger for gluon than for quark jets. Correcting the distributions for residual misidentification of the quark and gluon jets, the ratio of mean particle multiplicty of gluon relative to quark jets is measured to be $$\frac{{\left\langle n \right\rangle _{gluon} }}{{\left\langle n \right\rangle _{quark} }} = 1.27 \pm 0.04(stat.) \pm 0.06(syst.),$$ where the jets are defined using thek ⊥ jet finder. The numerical value of this ratio is found to be sensitive to the choice of the jet algorithm. The experimental results are compared to Monte Carlo calculations which incorporate perturbative QCD along with different assumptions about the hadronization process.

From a sample of 3308 e+e− → τ+τ− events with an estimated background of 1.9%, we find 964 τ → eνν, 903 τ → μνν, and 309 τ → π(K)ν candidates. Efficiency and background estimates determined from both Monte Carlo and control sample studies yield the following branching ratios: B(τ → eνν) = 17.4 ± 0.5 (stat) ± 0.4 (sys)%, B(τ → μνν) = 16.8 ± 0.5 ± 0.4%, and B(τ → π(K)ν) = 12.1 ± 0.7 ± 0.5%. These values are in good agreement with previous measurements. The measured lepton branching ratios, when combined with the world-average measured value for the τ lifetime, yield a ratio of the τ Fermi coupling constant to that of the lighter leptons given by Gτ/Ge,μ = 0.92 ± 0.04, where it is assumed Ge = Gμ ≡ Ge,μ. The average τ polarization at the Z° resonance is measured to be −0.01±0.09 from an analysis of the momentum spectra of the electron, muon, and pion candidates, implying that the ratio of vector to axial vector couplings of the τ to the Z° is ντ/ατ = 0.01 ± 0.04. The measurements of the average polarizations in the forward and backward hemispheres lead to the efficiency-corrected, forward-backward polarization asymmetry AFBpol = −0.22 ± 0.10, implying for the electron couplings to the Z° the ratio νe/αe = 0.15±0.07. Since these values for the tau and electron couplings are consistent with one another, we assume lepton universality to derive ν/α = 0.05 ± 0.04 and a value for the weak mixing angle of sin2θW = 0.237 ± 0.009, with no ambiguity introduced by the relative signs of ν and α.

The differential cross sections for lepton pair production in e+e− annihilation at 29 GeV have been measured and found to be in good agreement with the standard model of the electroweak interaction. With the assumption of e−μ−τ universality, the weak neutral-current couplings are determined to be ga2=0.23±0.05 and gv2=0.03±0.04.Received 29 August 1983DOI:https://doi.org/10.1103/PhysRevLett.51.1941©1983 American Physical Society

The Mark II detector has been upgraded in preparation for its role as the first detector to take data at the Stanford Linear Collider. The new detector components include the central drift chamber, the time-of-flight system, the coil, the endcap electromagnetic calorimeters and the beam energy and luminosity measuring devices. There have also been improvements in detector hermeticity. All of the major components were installed for a test run at the PEP storage ring (√s = 29 GeV) in 1985. This paper describes the upgraded detector, including its trigger and data acquisition systems, and gives performance figures for its components. Future improvements are also discussed.

Quark and gluon jets in e+e− three-jet events at LEP are identified using lepton tagging of quark jets, through observation of semi-leptonic charm and bottom quark decays. Events with a symmetry under transposition of the energies and directions of a quark and gluon jet are selected: these quark and gluon jets have essentially the same energy and event environment and as a consequence their properties can be compared directly. The energy of the jets which are studied is about 24.5 GeV. In the cores of the jets, gluon jets are found to yield a softer particle energy spectrum than quark jets. Gluon jets are observed to be broader than quark jets, as seen from the shape of their particle momentum spectra both in and out of the three-jet event plane. The greater width of gluon jets relative to quark jets is also visible from the shapes of their multiplicity distributions. Little difference is observed, however, between the mean value of particle multiplicity for the two jet types.

The mass and width of the W boson are measured using e+e– → W+W– events from the data sample collected by the OPAL experiment at LEP at centre-of-mass energies between 170 GeV and 209 GeV. The mass (m W) and width (Γ W) are determined using direct reconstruction of the kinematics of W+W– → ${\text{q\ifmmode\expandafter\bar\else\expandafter\=\fi{q}}}{\ell }\nu$ and W+W– → ${\text{q\ifmmode\expandafter\bar\else\expandafter\=\fi{q}q\ifmmode\expandafter\bar\else\expandafter\=\fi{q}}}$ events. When combined with previous OPAL measurements using W+W– → $ {\ell }\nu {\ell }\nu $ events and the dependence on of the WW production cross-section at threshold, the results are determined to be $ \begin{array}{*{20}c} {{m_{{\text{W}}} = 80.415 \pm 0.042 \pm 0.030 \pm 0.009\;{\text{GeV}}}} \\ {{\Gamma _{{\text{W}}} = 1.996 \pm 0.096 \pm 0.102 \pm 0.003\;{\text{GeV}}}} \\ \end{array} $ where the first error is statistical, the second systematic and the third due to uncertainties in the value of the LEP beam energy. By measuring in the channel using several different determinations of the direction of jets with differing sensitivities to soft particles, a limit is also obtained on possible final-state interactions due to colour reconnection effects inW+W– → ${\text{q\ifmmode\expandafter\bar\else\expandafter\=\fi{q}q\ifmmode\expandafter\bar\else\expandafter\=\fi{q}}}$ events. The consistency of the results for the W mass and width with those inferred from other electroweak parameters provides an important test of the Standard Model of electroweak interactions.

Bose-Einstein correlations between like-sign charged track pairs have been studied in e+e− annihilation hadronic events at centre-of-mass energies around the Z0 peak as a function of Q, the four-momentum difference of the pair. The measurement was performed with the OPAL detector at LEP. Assuming the charged tracks to be pions, the observed Bose-Einstein enhancement was used to extract the values of the strength of the effect and the radius of the pion emitting source, which were found to be λ=0.866±0.032±0.140 and R0=0.928±0.019±0.150 fm, respectively, where the first error is statistical and the second is systematic. The results do not show significant variation in comparison to e+e− annihilation measurements at lower centre-of-mass energies. If non-pion track contamination is taken into account, the value of the strength λ becomes consistent with unity.

A high-statistics study of $\ensuremath{\psi}$ decays into baryon final states has been done with the Mark II detector at SPEAR. A detailed test of baryon-antibaryon decay modes is presented. Substantial resonance formation is observed in multibody decays of the $\ensuremath{\psi}$ involving baryons. Branching ratios for a large number of decay modes are given, including the radiative decay $\ensuremath{\psi}\ensuremath{\rightarrow}p\overline{p}\ensuremath{\gamma}$. The flavor-SU(3)-forbidden decays $\ensuremath{\psi}\ensuremath{\rightarrow}{\ensuremath{\Sigma}}^{\ifmmode\pm\else\textpm\fi{}}(1385){\overline{\ensuremath{\Sigma}}}^{\ensuremath{\mp}}$+charge conjugate are observed with substantial branching ratios.

This document summarizes the work of the Accelerator Working Group (AWG) of the International Scoping Study (ISS) of a Future Neutrino Factory and Superbeam Facility. The main goal of the activity was to reach consensus on a baseline design for a Neutrino Factory complex, including proton driver parameters, choice of target, front-end design, acceleration system design, and decay ring geometry. Another goal was to explore the commonality, if any, between the proton driver for a Neutrino Factory and those for a Superbeam or Beta Beam facility. In general, the requirements for either of the latter facilities are less stringent than those for a Neutrino Factory. Here, we discuss concepts, parameters, and expected performance of the required subsystems for our chosen baseline design of a Neutrino Factory. We also give an indication of the main R&D tasks — many of which are already under way — that must be carried out to finalize facility design approaches.

We have studied the Dalitz plot for the recently observed charged state decaying into ${K}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ at 1876 MeV/${\mathit{c}}^{2}$ and we find that the final state is incompatible with a natural spin and parity assignment. This information, coupled with the earlier observation of the ${K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}$ decay mode (a final state of natural spin and parity) of the neutral state at 1865 MeV/${\mathit{c}}^{2}$, suggest parity nonconservation in the decays of these objects if they are members of the same isomultiplet as their proximity in mass suggests.

We present the inclusive photon spectra observed in ψ(3095) and ψ(3684) decays. The decay ψ(3684)→γχ(3415) is observed with a branching fraction of 0.075 ± 0.026. Evidence is presented for three intermediate states in the decay sequence ψ(3684)→γγψ(3095) with masses of 3504, 3543, and 3455 or 3340 MeV.Received 21 September 1976DOI:https://doi.org/10.1103/PhysRevLett.37.1596©1976 American Physical Society

The total momentum and transverse momentum spectra of electrons in e+e− annihilation at 29 GeV have been measured. The inclusive cross section is determined to be 14.4±1.6±5.2 pb for momenta greater than 2 GeV/c. The average semielectronic branching ratios of charm and bottom quarks are measured to be (6.3±1.2±2.1)% and (11.6±2.1±1.7)%, respectively. The fragmentation function for bottom quarks is determined to be peaked at high z, with 〈z〉b=0.75±0.05±0.04.Received 4 March 1983DOI:https://doi.org/10.1103/PhysRevLett.50.1542©1983 American Physical Society

The ${D}^{\ensuremath{\circ}}$ Cabibbo-suppressed decay modes ${\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ and ${K}^{\ensuremath{-}}{K}^{+}$ have been observed and the following ratios of ${D}^{\ensuremath{\circ}}$ partial decay widths have been measured: $\frac{\ensuremath{\Gamma}({D}^{\ensuremath{\circ}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})}{\ensuremath{\Gamma}({D}^{\ensuremath{\circ}}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})}=0.033\ifmmode\pm\else\textpm\fi{}0.015$ and $\frac{\ensuremath{\Gamma}({D}^{\ensuremath{\circ}}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{K}^{+})}{\ensuremath{\Gamma}({D}^{\ensuremath{\circ}}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})}=0.113\ifmmode\pm\else\textpm\fi{}0.030$.

The OPAL experiment at the CERN LEP collider recently increased the geometrical acceptance of its silicon microvertex detector. The azimuthal coverage is improved by adding one pair of detector modules to each of the two layers, while the polar angle coverage is extended by adding new detector modules in line with the existing ones. This improves the efficiency for high quality tracking in OPAL and in particular for b quark tagging in Higgs boson searches. A description of the detector is given, with emphasis on new or modified elements with respect to the earlier version. Results on the performance of the new detector are presented.

The process $\mathrm{e}^+\mathrm{e}^- \to\gamma\gamma(\gamma)$ is studied using data collected by the OPAL detector at LEP between the years 1997 and 2000. The data set corresponds to an integrated luminosity of 672.3 pb-1 at centre-of-mass energies lying between 181 GeV and 209 GeV. Total and differential cross-sections are determined and found to be in good agreement with the predictions of QED. Fits to the observed angular distributions are used to set limits on parameters from several models of physics beyond the Standard Model such as cut-off parameters, contact interactions of the type $\mathrm{e}^+\mathrm{e}^- \gamma\gamma$ , gravity in extra spatial dimensions and excited electrons. In events with three photons in the final state the mass spectrum of photon pairs is investigated. No narrow resonance $X\to\gamma\gamma$ is found and limits are placed on the product of the $\rm X \gamma$ production cross-section and branching ratio.

A search for the Standard Model Higgs boson has been performed with the OPAL detector at LEP based on the full data sample collected at s≈192–209 GeV in 1999 and 2000, corresponding to an integrated luminosity of approximately 426 pb−1. The data are examined for their consistency with the background-only hypothesis and various Higgs boson mass hypotheses. A lower bound of 109.7 GeV is obtained on the Higgs boson mass at the 95% confidence level. At higher masses, the data are consistent with both the background and the signal-plus-background hypotheses.

The strong coupling constant, αs, has been determined in hadronic decays of theZ 0 resonance, using measurements of seven observables relating to global event shapes, energy correlations and jet rates. The data have been compared with resummed QCD calculations, which are combined with theO( s 2 ) theory. The seven measurements agree to about 10% and the final results, based on a weighted average, is: $$\alpha _s (M_{Z^0 } ) = 0.120 \pm 0.006,$$ where the error includes both experimental and theoretical uncertainties. This value corresponds to renormalization scale $$\mu = M_{Z^0 } $$ and the error includes the uncertainty in this choice of scale. The present measurement complements previous determinations using theO( s 2 ) QCD matrix elements alone, and yields a compatible result, with comparable errors.

A search for single top quark production via flavour changing neutral currents (FCNC) was performed with data collected by the OPAL detector at the e+e− collider LEP. Approximately 600 pb−1 of data collected at s=189–209 GeV were used to search for the FCNC process e+e−→tc(u)→bWc(u). This analysis is sensitive to the leptonic and the hadronic decay modes of the W boson. No evidence for a FCNC process is observed. Upper limits at the 95% confidence level on the single top production cross-section as a function of the centre-of-mass energy are derived. Limits on the anomalous coupling parameters κγ and κZ are determined from these results.

A search for stable and long-lived massive particles of electric charge |Q/e|=1 or fractional charges of 2/3, 4/3, and 5/3 is reported using data collected by the OPAL detector at LEP, at centre-of-mass energies from 130 to 209 GeV. These particles are assumed to be pair-produced in e+e− collisions and not to interact strongly. No evidence for the production of these particles was observed. Model-independent upper limits on the production cross-section between 0.005 and 0.028 pb have been derived for scalar and spin-1/2 particles with charge ±1. Within the framework of the Constrained Minimal Supersymmetric Standard Model (CMSSM), this implies a lower limit of 98.0 (98.5) GeV on the mass of long-lived right- (left-)handed scalar muons and scalar taus. Long-lived charged heavy leptons and charginos are excluded for masses below 102.0 GeV. For particles with fractional charge ±2/3, ±4/3 and ±5/3, the upper limit on the production cross-section varies between 0.005 and 0.020 pb. All mass and cross-section limits are derived at the 95% confidence level and are valid for particles with lifetimes longer than 10−6 s.

A search for pair-produced doubly charged Higgs bosons has been performed using data samples corresponding to an integrated luminosity of about 614 pb−1 collected with the OPAL detector at LEP at centre-of-mass energies between 189 GeV and 209 GeV. No evidence for a signal has been observed. A mass limit of 98.5 GeV/c2 at the 95% confidence level has been set for the doubly charged Higgs particle in left–right symmetric models. This is the first search for doubly charged Higgs bosons at centre-of-mass energies larger than 91 GeV.

V o l u m e 160B, n u m b e r 1,2,3 PHYSICS LETTERS 3 October 1985 UPPER LIMIT O N B°B ° MIXING IN e + e - ANNIHILATION AT 29 GeV ~ T. SCHAAD, M.E. NELSON 1, G. ABRAMS, D. AMIDEI 2, A.R. BADEN, T. BARKLOW, A.M. BOYARSKI, J. BOYER, M. BREIDENBACH, P.R. BURCHAT, D.L. BURKE, F. BUTLER, J.M. D O R F A N , G.J. FELDMAN, G. GIDAL, L. G L A D N E Y 3, M.S. GOLD, G. GOLDHABER, L. G O L D I N G 4, j. HAGGERTY, G. HANSON, K. HAYES, D. HERRUP, R.J. HOLLEBEEK, W.R. INNES, J.A. JAROS, I. JURICIC, J.A. K A D Y K , D. KARLEN, S.R. KLEIN, A.J. L A N K F O R D , R.R. LARSEN, B.W. LECLAIRE, M. LEVI 5, N.S. LOCKYER 3, V. LIJTH, C. MATTEUZZI 5, R.A. ONG, M.L. PERL, B. RICHTER, K. RILES, M.C. ROSS, P.C. ROWSON, H. SCHELLMAN 2, W.B. SCHMIDKE, R. SCHWITTERS, P.D. SHELDON, G.H. TRILLING, C. DE LA VAISSIERE 6, D.R. WOOD, J.M. YELTON 7 and C. ZAISER Stanford Linear Accelerator Center, Stanford Unwerslty, Stanford, CA 94305, USA Lawrence Berkeley Laboratory and Department of Physws, Umverstty of Cahforma, Berkeley, CA 94720, USA Department of Physws, Harvard Unwerstty, Cambridge, MA 02138, USA Recewed 21 June 1985 The rate of ddepton production m the process e+e - --* hadrons at Vs- = 29 GeV is found to be m good agreement with predictions based on semdeptomc decays of bottom and charm hadrons. We determine that the average probability for a semdeptonlc decay of a hadron lnmally containing a b quark to produce a positive lepton is less than 0 12 at the 90% confidence level and set upper hmlts on B°B ° rmxing. New knowledge of the weak mixing angles, im- posed by the long B lifetime [1,2], a lower bound on the t quark mass [3], and a small ratio [4] of F(b-*u)/ P(b ~ c), has led to predictions that B 0 mesons and, to a much lesser extent, B 0 mesons should exhibit mixing [5,6]. B 0 ~0 mixing can lead to the production of like- sign dileptons in the process e+e - ~ BOBX -> BOBX l This work was supported in part by the Department of Energy, contracts DE-AC03-76SF00515 (SLAC), DE-AC03- 76SF00098 (LBL), and DE-AC02-76ER03064 (Harvard) Present address: California Institute of Technology, Pasadena, CA 91125, USA Present address Umverslty of Chicago, Clucago, IL 60637, USA. Present address University of Pennsylvania, Pluladelptua, PA 19104, USA. Present address Therma-Wave, Inc., Fremont, CA 94539, USA. Present address: CERN, CH-1211 Geneva 23, Switzerland. Present address: LPNHE, Umverslt6 Pierre et M a n e Cune, F-75230 Pans, France Present address Oxford Umverslty, Oxford, England £ - £ - X ,1. Recently, the CLEO collaboration ,2 has reported an upper limit on B0B 0 mixing from the rate of like.sign dileptons produced in the decay of the T(4s). The UA1 collaboration [8] has observed like-sign dimuon events, leading to speculations in the literature [9] that these events could arise from B s 0 - B - 0 s mixing. In this letter, we report a measurement of dflepton rates in e+e - annihilation at an energy above the B 0 production threshold. Here, we always imply the charge conjugate reaction. We use t h e Particle Data Group convention that B (B) hadrons in t h e absence of mixing decay into positive (negative) lep- tons. The t~pes_of neutral B m e s o n s are denoted by B~ = bd and B~ = bs. The CLEO collaboration has set an upper limit on the di- lepton ratio Y n q = ( N n q n q + N~O=O)/N~O~O = N~±/N +- ~a va~a nd~d ndDd The limit set isYB~ < 0.30 at 90% C L under the assump- tion of equal semileptortic branching ratios. Since the B m e s o n s are in an l = 1 state, mixing is suppressed by inter- ference effects (see ref. [12]) a n d Y B ~ = rd, where r d = 0370-2693/85/$ 03.30 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)

The anomalous eμ and 2-prong μx events produced in e+e− annihilation are used to determine the properties of the proposed τ charged lepton. We find the τ mass is 1.90 ± 0.10 GeV/c2; the mass of the associated neutrino, ντ, is less than 0.6 GeV/c2 with 95% confidence; V - A coupling is favored over V + A coupling for the τ − ντ current; and the leptonic branching ratios are 0.186 ± 0.010 ± 0.028 from the eμ events and 0.175 ± 0.027 ± 0.030 from the μx events where the first error is statistical and the second is systematic.

We present a high statistics measurement of the branching ratio for the decayτ−→π−μτ using data obtained with the Mark II detector at the SLAC e+e− storage ring SPEAR. We have used events from the center-of-mass energy region 3.52 to 6.7 GeV to determine thatB(τ−→π−μτ)=0.117±0.004±0.018. From electron-muon events in the same data sample, we have determined thatB(τ−→π−μτ)/B(τ−→e−−μeμτ)=0.66±0.03±0.11. We present measurements of the mass and spin of theτ and the mass of the τ neutrino based, for the first time, on a hadronic decay mode of the τ.

We observe anomalous eμ and e-hadron events in e+e− collisions at SPEAR in an experiment that uses a lead-glass counter system to identify electrons. The anomalous events are observed in the two-charged-prong topology. Their properties are consistent with the production of a pair of heavy leptons in the reaction e+e−→τ+τ− with subsequent decays of τ± into leptons and hadrons. Under the assumption that they come only from this source, we measure the branching ratios B(τ→eνeντ)=(22.4±5.5)% and B(τ→h+neutrals)=(45±19)%.Received 6 July 1977DOI:https://doi.org/10.1103/PhysRevLett.39.1058©1977 American Physical Society

Results of studies of radiative decays of the ψ(3684) using the SLAC-LBL magnetic detector at the electron storage ring SPEAR are presented. There are three high-mass states produced in ψ(3684) radiative decays, with masses of 3414±3, 3503±4, and 3551±4 MeV where the errors given do not include an overall mass-scale uncertainty of ±4 MeV. There is some evidence for a fourth such state at either 3455 or 3340 MeV. The branching ratio for ψ(3684) radiative decay into the state at 3414 MeV is found to be (7.5 ± 2.6)%. The decay modes of these states into hadrons and into γψ(3095) are studied, yielding information about the branching ratios, spins, and parities of the states. The results are interpreted in the charmonium picture of the high-mass states.Received 3 August 1977DOI:https://doi.org/10.1103/PhysRevD.17.1731©1978 American Physical Society

We present here a measurement of six branching ratios of $\ensuremath{\psi}(3095)$ corresponding to the decays $\ensuremath{\psi}(3095)\ensuremath{\rightarrow}\ensuremath{\rho}\ensuremath{\pi}$, $2({\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})$, $2({\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})1{\ensuremath{\pi}}^{0}$, $3({\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})$, $3({\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})1{\ensuremath{\pi}}^{0}$, and $4({\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}})1{\ensuremath{\pi}}^{0}$. From this study, the isospin and $G$-parity quantum numbers are found to be ${I}^{G}={0}^{\ensuremath{-}}$.

Data from ${e}^{+}{e}^{\ensuremath{-}}$ annihilation into hadrons at 4.8 GeV center-of-mass energy were used to search for charmed mesons in the mass range 1.5 to 4.0 GeV/${\mathit{c}}^{2}$. We looked for narrow peaks in the invariant-mass distributions for ${K}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$, ${{K}_{s}}^{0}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, ${K}^{+}{K}^{\ensuremath{-}}$, ${K}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$, ${{K}_{s}}^{0}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$, ${{K}_{s}}^{0}{K}^{\ifmmode\pm\else\textpm\fi{}}$, and ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$. We present upper limits for the inclusive production cross section times the branching ratio for charmed mesons having these decay modes.

We have observed events of the type μ±+(3π)∓ in e+e− interactions at center-of-mass energies above 6 GeV. The properties of the events are consistent with their coming from the heavy-lepton decays τ→μνν¯ and τ¯→ν¯3π or τ¯→ν¯4π. The three-charged-pion invariant-mass distribution shows a significant peak at a mass 1.1 GeV/c2. We find the branching ratio into three charged and any number of neutral pions B(τ+→ν¯π+π+π−nπ0)=0.18±0.065.Received 13 February 1978DOI:https://doi.org/10.1103/PhysRevLett.40.1120©1978 American Physical Society

The production of enutral kaons in e+e− annihilation has been measured for c.m. energies between 3.4 GeV and 7.6 GeV. Near 4 GeV the inclusive KS cross section shows an increase and structure similar to total hadron production. Roughly 40–45% of all hadronic final states contain kaons, except at 4.028 GeV and 4.415 GeV, where a significantly larger kaon fraction is observed.

In a sample of multihadron events with a π0 from e+e− annihilation data at 3.77-GeV center-of-mass energy, we observe the decay D0→K−π+π0 with direct observation of the π0. The observed branching fraction is (12±6)%.Received 6 October 1977DOI:https://doi.org/10.1103/PhysRevLett.40.74©1978 American Physical Society

Hadronic event shape distributions from e+e- annihilation measured by the OPAL experiment at centre-of-mass energies between 91 GeV and 209 GeV are used to determine the strong coupling {\alpha}S. The results are based on QCD predictions complete to the next-to- next-to-leading order (NNLO), and on NNLO calculations matched to the resummed next-to-leading-log-approximation terms (NNLO+NLLA). The combined NNLO result from all variables and centre-of-mass energies is {\alpha}S(mZ0) = 0.1201 {\pm} 0.0008(stat.) {\pm} 0.0013(exp.) {\pm} 0.0010(had.) {\pm} 0.0024(theo.). while the combined NNLO+NLLA result is {\alpha}S(mZ0) = 0.1189 {\pm} 0.0008(stat.) {\pm} 0.0016(exp.) {\pm} 0.0010(had.) {\pm} 0.0036(theo.). The completeness of the NNLO and NNLO+NLLA results with respect to missing higher order contributions, studied by varying the renormalization scale, is improved compared to previous results based on NLO or NLO+NLLA predictions only. The observed energy dependence of {\alpha}S agrees with the QCD prediction of asymptotic freedom and excludes the absence of running.

A facility that can deliver beams of electron and muon neutrinos from the decay of a stored muon beam has the potential to unambiguously resolve the issue of the evidence for light sterile neutrinos that arises in short-baseline neutrino oscillation experiments and from estimates of the effective number of neutrino flavors from fits to cosmological data. In this paper, we show that the nuSTORM facility, with stored muons of $3.8\text{ }\mathrm{GeV}/\mathrm{c}\text{ }\ifmmode\pm\else\textpm\fi{}\text{ }10%$, will be able to carry out a conclusive muon neutrino appearance search for sterile neutrinos and test the LSND and MiniBooNE experimental signals with $10\ensuremath{\sigma}$ sensitivity, even assuming conservative estimates for the systematic uncertainties. This experiment would add greatly to our knowledge of the contribution of light sterile neutrinos to the number of effective neutrino flavors from the abundance of primordial helium production and from constraints on neutrino energy density from the cosmic microwave background. The appearance search is complemented by a simultaneous muon neutrino disappearance analysis that will facilitate tests of various sterile neutrino models.

We have found evidence for jet structure in ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{hadrons}$ at center-of-mass energies of 6.2 and 7.4 GeV. At 7.4 GeV the jet-axis angular distribution integrated over azimuthal angle was determined to be proportional to $1+(0.78\ifmmode\pm\else\textpm\fi{}0.12){cos}^{2}\ensuremath{\theta}$.

Using muon candidates in 133 000 hadronic decays of the Z0, recorded by the OPAL detector at LEP, we have measured the fraction of events containing semi-leptonic decays of b flavoured hadrons. An analysis based on fitting the shape of the momentum and transverse momentum distributions of the muon candidates gave the result: (Γ(Z0→bb)Γ(Z0→hadrons))×Br(b→μ)=0.0226±0.0007±0.0013, and also yielded: (Γ(Z0→cc)Γ(Z0→hadrons))×Br(c→μ)=0.0176±0.0025±0.0042. Using the charge of the muon and the angle of the event thrust axis with respect to the electron beam, in a b-enriched event sample, we measured the forward-backward asymmetry for Z0 → bb decays. Without correction for B0B0 mixing, the asymmetry was found to be AbFB = 0.072±0.042±0.010.

The production of the octet and decuplet baryons Λ, Ξ−, Σ(1385)±, Ξ(1530)0 and Ω− and the corresponding antibaryons has been measured in a sample of 485 000 hadronic Z0 decays. Results on differential and integrated cross sections are presented. The differential cross section of Λ baryons is found to be softer than the one predicted by the Jetset and Herwig Monte Carlo generators. The measured decuplet yields are found to disagree with the simple diquark picture where only one tuning parameter for spin 1 diquarks is used. Comparisons of the momentum spectra for Λ and Ξ− with the predictions of an analytical QCD formula are also presented.

Using a sample of 5558 Z0 → τ+τ− decays produced at LEP a direct test of CP-invariance in the neutral current reaction e+e− → τ+τ− is performed. Samples of events where eachy τ decays into a single particle have been isolated for the construction of CP-odd observables. Three different event classes are considered: lepton-lepton, lepton-hadron, and hadron-hadron. No evidence for a non-zero expectation value of the considered CP-observables and hence for CP-violation is observed. Quantitatively, we deduce from this null result an estimate on the weak dipole moment d̃τ(m2Z = (−4.5 ± 5.3 ± 1.4) × 10−17 e cm for the lepton-lepton signature and d̃τ(m2Z = (1.4 ± 3.7 ± 1.3) × 10−17 e cm for the hadron-hadron signature. Combining these results we place a limit with 95% confidence of |d̃τ|⩽7.0 × 10−17 e cm.

A search for scalar leptoquarks has been performed with data from the OPAL detector at the e+e− storage ring LEP. In a data sample corresponding to an integrated luminosity of 6.3 pb−1 no evidence for leptoquark production was observed where the leptoquark decays into a quark and either a charged lepton (e, μ, τ) or a neutrino. An upper limit of 1.7 pb on the production cross section for leptoquarks is obtainedassuming a branching ratio of 50% for the decay of the leptoquark into the channels with a charged lepton. Lower limits on the leptoquark mass between 41.4 and 46.4 GeV/c2 at 95% CL are obtained, depending on the effecte SU(2) × U(1) invariant couplings assigned to the leptoquark.

We observe both the JPC=1++ f1(1285) and the JPC=0−+ η’(958) in tagged two-photon interactions and the η’(958) in untagged interactions. The measured Q2 dependence and decay distribution support the f1(1285) spin and parity assignment. The radiative width of the f1(1285) is measured as (M2/Q2)Γγγ*=9.4±2.5±1.7 keV, on the assumption of a ρ-pole form factor.Received 18 September 1987DOI:https://doi.org/10.1103/PhysRevLett.59.2012©1987 American Physical Society

We confirm the observation of a spin-1 resonance at 1423 MeV in the ${K}_{S}^{0}$${K}^{\ifmmode\pm\else\textpm\fi{}}$${\ensuremath{\pi}}^{\ensuremath{\mp}}$ system produced in single-tagged two-photon interactions. The Dalitz plot indicates that this resonance decays primarily via a ${K}^{\mathrm{*}}$K intermediate state. We measure a radiative width times branching ratio ${\mathit{B}}_{\mathit{KK}\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}\mathrm{\ensuremath{\pi}}}$(${\mathit{M}}^{2}$/${\mathit{Q}}^{2}$)${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\gamma}\ensuremath{\gamma}\mathrm{*}}$=3.2\ifmmode\pm\else\textpm\fi{}1.4\ifmmode\pm\else\textpm\fi{}0.6 keV on the assumption of a \ensuremath{\rho}-pole form factor.

Direct electrons are observed in baryon events produced in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation at center-of-mass energies above the ${\ensuremath{\Lambda}}_{c}{\overline{\ensuremath{\Lambda}}}_{c}$ threshold. These events are attributed to charmed-baryon pair production and subsequent ${\ensuremath{\Lambda}}_{c}$ semileptonic decay. Various semileptonic branching ratios of the ${\ensuremath{\Lambda}}_{c}$ are determined, including $B({\ensuremath{\Lambda}}_{c}\ensuremath{\rightarrow}{e}^{+}X)=(4.5\ifmmode\pm\else\textpm\fi{}1.7)%$.

The charged-particle multiplicities of hadronic events deriving from produced bottom or charm quarks have been measured in the Mark II detector at PEP in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation at 29 GeV. For events containing one semileptonic and one hadronic weak decay, we find multiplicities of 15.2\ifmmode\pm\else\textpm\fi{}0.5\ifmmode\pm\else\textpm\fi{}0.7 for bottom and 13.0\ifmmode\pm\else\textpm\fi{}0.5\ifmmode\pm\else\textpm\fi{}0.8 for charm. The corresponding multiplicities of charged particles accompanying the pair of heavy hadrons are 5.2\ifmmode\pm\else\textpm\fi{}0.5\ifmmode\pm\else\textpm\fi{}0.9 for bottom, and 8.1\ifmmode\pm\else\textpm\fi{}0.5\ifmmode\pm\else\textpm\fi{}0.9 for charm.

We present a measurement of the cross section for hadron production by e+e− annihilation in the vicinity of the previously observed resonance near 3.77 GeV. The data are used to determine the parameters of the ψ(3770) resonance. The values found are: mass, 3764±5 MeV/c2, total width, 23.5±5 MeV, and partial width to electron pairs, 276±50 eV.Received 26 November 1979DOI:https://doi.org/10.1103/PhysRevD.21.2716©1980 American Physical Society

The charged-particle multiplicity distribution in $\ensuremath{\tau}$ decays is determined from data collected at the ${e}^{+}{e}^{\ensuremath{-}}$ storage ring PEP. The one-, three-, and five-charged-particle inclusive branching fractions are (86 \ifmmode\pm\else\textpm\fi{} 2)%, (14 \ifmmode\pm\else\textpm\fi{} 2)%, and 0.5%, respectively.

The inclusive production of antiprotons and $\ensuremath{\Lambda}'\mathrm{s}$ in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation has been measured as a function of the c.m. energy in the range 3.7-7.6 GeV. We find that the baryon cross section has a behavior different from the total hadronic production. Our results show a rapid rise in the ratio $\frac{{\ensuremath{\sigma}}_{\overline{p}}}{{\ensuremath{\sigma}}_{\ensuremath{\mu}\ensuremath{\mu}}}$ between 4.4 and 5 GeV, consistent with what would be expected from charmed baryon production. $\overline{\ensuremath{\Lambda}}$ production is 10-15% of $\overline{p}$ production at all energies.

With use of three-prong $\ensuremath{\tau}$ decays observed by the Mark II detector at the Stanford Linear Accelerator Center (PEP), the $\ensuremath{\tau}$ lifetime is measured to be (4.6\ifmmode\pm\else\textpm\fi{}1.9)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ sec.

The prompt photon decay $\ensuremath{\psi}(3095)\ensuremath{\rightarrow}\ensuremath{\gamma}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ has been studied with the Mark II detector at SPEAR. This channel is found to contain a $\ensuremath{\gamma}{\ensuremath{\rho}}^{0}{\ensuremath{\rho}}^{0}$ component with ${\ensuremath{\rho}}^{0}{\ensuremath{\rho}}^{0}$ masses concentrated between 1.4 and 2.0 GeV/${\mathit{c}}^{2}$. The branching fraction for the $\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\gamma}{\ensuremath{\rho}}^{0}{\ensuremath{\rho}}^{0}$ decay with masses less than 2.0 GeV/${\mathit{c}}^{2}$ is measured to be (1.25\ifmmode\pm\else\textpm\fi{}0.35\ifmmode\pm\else\textpm\fi{}0.40)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}3}$.

We present branching ratios for several mesonic decay modes of the ψ(3095). The two-body and quasi-two-body final states have branching ratios that follow the general pattern of behavior expected for the decay of an SU(3) singlet via an SU(3)-symmetric interaction. The π+π− and K+K− mass spectra in ωππ, ωKK, φππ, and φKK final states show remarkable differences that are most readily interpretable in terms of the Okubo-Zweig-Iizuka rule.Received 3 January 1977DOI:https://doi.org/10.1103/PhysRevD.15.1814©1977 American Physical Society

We have searched the mass region 3.2 to 5.9 GeV for evidence of narrow resonances in e+e−→hadrons. We find no evidence for any such resonances other than the ψ(3695) in this region with a sensitivity ranging from about 12 to 45% of the integrated cross section of the ψ(3695). The more stringent bounds apply to resonances of a few MeV width, while the looser bounds apply to resonances of up to 20 MeV width.Received 13 January 1975DOI:https://doi.org/10.1103/PhysRevLett.34.762©1975 American Physical Society

We have observed the decay $\ensuremath{\psi}(3684)\ensuremath{\rightarrow}\ensuremath{\psi}(3095)\ensuremath{\eta}$ with a branching fraction of (4.3\ifmmode\pm\else\textpm\fi{}0.8)%. This measurement, together with previous measurements of $\ensuremath{\psi}(3684)\ensuremath{\rightarrow}\ensuremath{\psi}(3095)+\mathrm{anything}$, $\ensuremath{\psi}(3684)\ensuremath{\rightarrow}\ensuremath{\psi}(3095){\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, and $\ensuremath{\psi}(3684)\ensuremath{\rightarrow}\ensuremath{\psi}(3095)\ensuremath{\gamma}\ensuremath{\gamma}$, indicates that isospin is conserved in the decay $\ensuremath{\psi}(3684)\ensuremath{\rightarrow}\ensuremath{\psi}(3095)\ensuremath{\pi}\ensuremath{\pi}$ and establishes the isospin and $G$ parity of the $\ensuremath{\psi}(3684)$ to be ${I}^{G}={0}^{\ensuremath{-}}$.

We observe evidence for the production of b-flavoured baryons in decays of the Z0 boson with the OPAL detector at LEP. We find 68 Λl−, Λl+ candidates in 458 583 hadronic Z0 decays. We interpret this as a signal of 55 ± 9+0.3−3.1 events from the semi-leptonic decays of b baryons. Assuming weakly decaying b baryons produced in Z0 decays are mostly Λb particles, we measure the product branching ratio (Γbb/Γhad) f (b→Λb) B (Λb→Λl−vX), averaged over the electron and muon channels, to be (6.2±1.0±1.5)×10−4.

The production of K0 mesons in e+e− interactions at center of mass energies in the region of the Z0 mass has been investigated with the OPAL detector at LEP. The rate is found to be 2.10±0.02±0.14 K0, Z0 per hadronic event. The predictions from the JETSET and HERWIG generators agree very well with both the rate and the scale invariant cross section (1/σhadβ) (dσ/dxE) for K0 production. Comparisons of the inclusive momentum spectrum with predictions of an analytical QCD formula and with data from lower center of mass energies are presented.

The production dynamics of baryon-antibaryon pairs are investigated using hadronic Z0 decays, recorded with the OPAL detector, which contain at least two identified Λ baryons. The rapidly difference for ΛΛ pairs shows the correlations expected from models with a chain-like production of baryon-antibaryon pairs. If the baryon number of a Λ is compensated by a Λ, the Λ is found with a probability of 53% in an interval of ±0.6 around the Λ rapidity. This correlation strength is weaker than predicted by the Herwig Monte Carlo and the Jetset Monte Carlo with a production chain of baryon-antibaryon, and stronger than predicted by the UCLA model. The observed rapidity correlations can be described by the Jetset Monte Carlo with a dominant production chain of baryon-meson-antibaryon, the popcorn mechanism. In addition to the short range correlations, one finds an indication of a correlation of ΛΛ pairs in opposite hemispheres if both the Λ and the Λ have large rapidities. Such long range correlations are expected if the primary quark flavours are compensated in opposite hemispheres and if these quarks are found in energetic baryons. Rates for simultaneous baryon and strangeness number compensation for ΛΛ, Ξ−Ξ+ and Ξ−Λ (Λ+ Λ) are measured and compared with different Monte Carlo models.

A search for the single production of doubly-charged Higgs bosons is performed using e+e− collision data collected by the OPAL experiment at centre-of-mass energies between 189 GeV and 209 GeV. No evidence for the existence of H±± is observed. Upper limits are derived on hee, the Yukawa coupling of the H±± to like-signed electron pairs. A 95% confidence level upper limit of hee< 0.071 is inferred for M(H±±)<160 GeV assuming that the sum of the branching fractions of the H±± to all lepton flavour combinations is 100%. Additionally, indirect constraints on hee from Bhabha scattering at centre-of-mass energies between 183 GeV and 209 GeV, where the H±± would contribute via t-channel exchange, are derived for M(H±±)<2 TeV. These are the first results both from a single production search and on constraints from Bhabha scattering reported from LEP.

Searches for a scalar top quark and a scalar bottom quark have been performed using a data sample of 438 pb−1 at centre-of-mass energies of s=192–209 GeV collected with the OPAL detector at LEP. No evidence for a signal was found. The 95% confidence level lower limit on the scalar top quark mass is 97.6 GeV if the mixing angle between the supersymmetric partners of the left- and right-handed states of the top quark is zero. When the scalar top quark decouples from the Z0 boson, the lower limit is 95.7 GeV. These limits were obtained assuming that the scalar top quark decays into a charm quark and the lightest neutralino, and that the mass difference between the scalar top quark and the lightest neutralino is larger than 10 GeV. The complementary decay mode of the scalar top quark decaying into a bottom quark, a charged lepton and a scalar neutrino has also been studied. The lower limit on the scalar top quark mass is 96.0 GeV for this decay mode, if the mass difference between the scalar top quark and the scalar neutrino is greater than 10 GeV and if the mixing angle of the scalar top quark is zero. From a search for the scalar bottom quark, a mass limit of 96.9 GeV was obtained if the mass difference between the scalar bottom quark and the lightest neutralino is larger than 10 GeV.