We have measured the inclusive prompt electron cross section over a wide momentum range (P>0.5 GeV/c) with the PEP-4 TPC detector. The semielectronic branching fractions of thec andb quarks are (9.1±0.9 (stat.)±1.3 (syst.))% and (11.0±1.8±1.0)%, respectively. Theb quark fragmentation function peaks at highz with 〈zb〉=0.74±0.05±0.03. The axial couplings to the neutral current areac=2.3±1.4±1.0 for thec quark andab=−2.0±1.9±0.5 for theb quark.
No description provided.
No description provided.
No description provided.
We have measured the inclusive branching ratio for B→ψX to be (1.09±0.16±0.21)%, and the exclusive branching ratios for B−→ψK− and B¯ ¯0 *0 to be (0.09±0.05)% and (0.41±0.18)%, respectively. The mass difference between neutral and charged B mesons is 1.1±2.1 MeV, while the difference between the mass of Υ(4S) and twice the mean B-meson mass is 18.5±3.0 MeV. The ψ momentum distribution implies a substantial two-body decay (in agreement with direct measurements), but also some combination of B→ψX with MX>1.5 GeV, and B→ψ’X.
No error for cross-section given in text.
No description provided.
We present the general properties of jets produced bye+e− annihilation. Their production and fragmentation characteristics have been studied with charged particles for c.m. energies between 12 and 43 GeV. In this energy rangee+e− annihilation into hadrons is dominated by pair production of the five quarksu, d, s, c andb. In addition, hard gluon bremsstrahlung effects which are invisible at low energies become prominent at the high energies. The observed multiplicity distributions deviate from a Poisson distribution. The multiplicity distributions for the overall event as well as for each event hemisphere satisfy KNO scaling to within ∼20%. The distributions ofxp=2p/W are presented; scale breaking is observed at the level of 25%. The quantityxpdδ/dxp is compared with multigluon emission calculations which predict a Gaussian distribution in terms of ln(1/x). The observed energy dependence of the maximum of the distributions is in qualitative agreement with the calculations. Particle production is analysed with respect to the jet axis and longitudinal and transverse momentum spectra are presented. The angular distribution of the jet axis strongly supports the idea of predominant spin 1/2 quark pair production. The particle distributions with respect to the event plane show clearly the growing importance of planar events with increasing c.m. energies. They also exclude the presence of heavy quark production,e+e−→Q\(\bar Q\) for quark masses up to 5<mQ<20.3 GeV (|eQ|=2/3) and 7<mQ<19 GeV (|eQ|=1/3). The comparison of 1/σtotdδ/dpT measured at 14, 22 and 34 GeV suggests that hard gluon bremsstrahlung contributes mainly to transverse momenta larger than 0.5 GeV/c. The rapidity distribution forW≧22 GeV shows an enhancement away fromy=0 which corresponds to an increase in yield of 10–15% compared to the centre region (y=0). The enhancement probably results from heavy quark production and gluon bremsstrahlung. The particle flux around the jet axis shows with increasing c.m. energy a rapidly growing number of particles collimated around the jet axis, while at large angles to the jet axis almost noW dependence is observed. For fixed longitudinal momentump‖ approximate “fan invariance” is seen: The shape of the angular distribution around the jet axis is almost independent ofW. The collimation depends strongly onp‖. For smallp‖,p‖<0.2 GeV/c, isotropy is observed. With increasingp‖ the particles tend to be emitted closer and closer to the jet axis.
R VALUES BELOW 32.5 GEV ARE IDENTICAL TO THOSE GIVEN IN BRANDELIK ET AL., PL 113B, 499 (1982).
No description provided.
CHARGED PARTICLE MULTIPLICITY DISTRIBUTIONS.
Results onK0 and Λ production ine+e− annihilation at c.m. energies of 14, 22 and 34 GeV are presented. The shape of theK0 and Λ differential cross sections are very similar to each other and to those of π±,K± and\(p(\bar p)\). Scaling violations are observed forK0 production. We obtain a value for the probability to produce strange quark-antiquark pairs relative to that to produce up or down quark-antiquark pairs of 0.35±0.02±0.05. The value ofRh=σ(e+e-→hX)/σµµ is shown to rise steadily with c.m. energy for all particle species. At 34 GeV we find 1.48±0.05K0 and 0.31±0.03 Λ per event. We have searched for possible Λ polarization. The production ofK0's and Λ's in jets is examined as a function ofpT2 and rapidity and compared to that of all charged particles; the yields in two and three jets are also investigated. Results are presented from events with two baryons\((\Lambda ,\bar \Lambda ,por\bar p)\) observed.
No description provided.
No description provided.
No description provided.
In a sample of B mesons from the decay of the ϒ(4S) produced in e+e− collisions at the Cornell Electron Storage Ring, inclusive protons, antiprotons, lambdas, and antilambdas have been observed. Lower limits to the B-to-baryon branching ratios are derived.
NUMERICAL VALUES OF DATA SUPPLIED BY E.H. THORNDIKE. CORRECTED ANTI(PROTON) PRODUCTION FROM UPSI(4S) DECAY.
NUMERICAL VALUES OF DATA SUPPLIED BY E.H. THORNDIKE. CORRECTED ANTI(LAMBDA) PRODUCTION FROM UPSI(4S) DECAY.
The inclusive production of η mesons at CM energies around 34 GeV has been studied for e + e − annihilation into hadrons. The average number of η-mesons per event is found to be 0.72 ± 0.10 (stat.) ± 0.18 (syst.). The abundance of η's is studied as a function of event shape parameters and it is compared to the corresponding π 0 rates.
No description provided.
Production of pions, kaons, protons and antiprotons has been studied in e + e − annihilations at 12 and 30 GeV centre of mass energy using time of flight techniques. The fractional yield of charged kaons and baryons appears to rise with outgoing particle momentum. At our highest energy at least 40% of e + e − annihilations into hadrons are estimated to contain baryons.
No description provided.
No description provided.
No description provided.
The pp->pp phi reaction has been studied at the Cooler Synchrotron COSY-Juelich, using the internal beam and ANKE facility. Total cross sections have been determined at three excess energies epsilon near the production threshold. The differential cross section closest to threshold at epsilon=18.5 MeV exhibits a clear S-wave dominance as well as a noticeable effect due to the proton-proton final state interaction. Taken together with data for pp omega-production, a significant enhancement of the phi/omega ratio of a factor 8 is found compared to predictions based on the Okubo-Zweig-Iizuka rule.
K+ K- invariant mass distribution.
Total cross sections.
Differential decay distribution of the K+ in the rest frame of the PHI-meson w.r.t. the beam.
Inclusive momentum spectra and multiplicity distributions of charged particles measured with BESII detector at center of mass energies of 2.2,2.6,3.0,3.2,4.6 and 4.8 GeV are presented. Values of the second binomial moment, $R_2$, obtained from the multiplicity distributions are reported. These results are compared with both experimental data from high energy $e^+e^-$, $ep$ and $p\bar{p}$ experiments and QCD calculations.
Measured xi =-ln(2p/sqrt(s)) spectra for centre of mass energy 2.2 GeV.. Errors are statistical and systematic added in quadrature.
Measured xi =-ln(2p/sqrt(s)) spectra for centre of mass energy 2.6 GeV.. Errors are statistical and systematic added in quadrature.
Measured xi =-ln(2p/sqrt(s)) spectra for centre of mass energy 3.0 GeV.. Errors are statistical and systematic added in quadrature.
We have used the momentum spectrum of leptons produced in semileptonic B-meson decays to set a 90%-confidence-level upper limit on Γ(b→ulν)Γ(b→clν) of 4%. We also measure the semileptonic branching fractions of the B meson to be (12.0±0.7±0.5)% for electrons and (10.8±0.6±1.0)% for muons.
No description provided.
No description provided.
Forum