We have measured the asymmetry of the cross section for γp→π+n from a polarized target at 5 and 16 GeV. The range of four-momentum transfer was 0.02<~−t<~1.0 GeV2. The π+ mesons were produced in a polarized butanol target and detected with the Stanford Linear Accelerator Center 20−GeVc spectrometer. A sizable asymmetry was found at both 5 and 16 GeV, a typical value being -0.6 near −t=0.3 GeV2. A small amount of data on the asymmetry of other photoproduction processes was also obtained.
No description provided.
No description provided.
No description provided.
Cross sections for the reactions γp→K+Λ and γp→K+Σ0 have been measured at squared four-momentum transfer (−t) from 0.005 to 2 GeV2, at photon energies 5, 8, 11, and 16 GeV. For −t>0.2 GeV2 each of the K+ cross sections is about ⅓ of the π+n photoproduction cross section, having nearly the same energy and momentum-transfer dependence. The K+ cross sections fall off at small |t|, however, in contrast to the sharp forward spike seen in π+n; this leads to a disagreement with an SU(3) prediction for −t<0.1 GeV2. The ratio of K+Σ0 to K+Λ cross sections is typically between 0.5 and 1.0.
'1'.
'1'.
'1'.
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.
Numerical values supplied by M.Levi.
Data requested from authors.
Extrapolated to full angular range.
η production has been investigated by the Mark II collaboration at the SLAC e+e− storage ring PEP. η particles are reconstructed by their γγ decay mode. The η fragmentation function has been measured and found to be in good agreement with the Lund-model prediction. η′ production has been measured for the first time in high-energy e+e− annihilation. There is evidence at the 3σ level for Ds± decay into ηπ± and η′π±.
Numerical values supplied by G.Wormser.
Z = 0.0 point extrapolated using LUND fragmentation model.
Z = 0.0 point extrapolated using LUND fragmentation model.
The cross section for the production of π+π− or K+K− pairs in γγ interactions is measured for mππ between 1.7 and 3.5 GeV/c2 and for two intervals of γγ center-of-mass scattering angle. Results are compared with predictions of a QCD model.
Data read off graph.
Data read off graph.
Inclusive ψ production in e+e− annihilation at 29 GeV has been measured with the Mark II detector. The ψ cross section is found to be 1.1±0.5±0.4 pb. After subtraction of the expected contribution from B decay, an upper limit of 0.02σμμ is obtained for other sources of ψ production.
No description provided.
We present results on Λc+ production in 29-GeV e+e− annihilation. The Λc+ are observed via their semileptonic decays to Λe+X and Λμ+X. With radiative corrections, we find σ(e+e−→Λc+X)〉BΛc+→eΛX)= 1.5±0.6±0.5 pb or 0.0038±0.0015±0.0012 Λc+→Λe+X decay per hadronic event, and σ(e+e−Λc+X)B(Λc+→μΛX)= 1.4±1.4±0.4 pb or 0.0035±0.0035±0.0011 Λc+→Λμ+X decay per hadronic event. These results can be used to place constraints on the predictions of various production models.
Cross sections * branching ratio for LAMBDA/C+ production in LAMBDA E+ decay channel.
Cross sections * branching ratio for LAMBDA/C+ production in LAMBDA MU+ decay channel.
The production of Λ hyperons in e+e− annihilation has been measured as a function of their total momenta, transverse momenta, and the event thrust. The total production rate is 0.213±0.012±0.018 Λ or Λ¯ per hadronic event. The observation of correlations in rapidity and angles for events with two detected Λ decays supports fragmentation models with local baryon-number compensation.
No description provided.
No description provided.
No description provided.
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− annihilation at 29GeV. For events containing one semileptonic and one hadronic weak decay, we find multiplicities of 15.2±0.5±0.7 for bottom and 13.0±0.5±0.8 for charm. The corresponding multiplicities of charged particles accompanying the pair of heavy hadrons are 5.2±0.5±0.9 for bottom, and 8.1±0.5±0.9 for charm.
.
.
.
A search for single electrons from the decay of singly produced scalar electrons has been made at the PEP storage ring at SLAC. No events of this type have been found in 123 pb−1 of data, resulting in a cross-section limit of less than 2.4×10−2 pb within the detector acceptance, and a 95%-confidence-level lower limit on the scalar-electron mass of 22.2 GeV/c2.
No description provided.
Forum