The inclusive production cross section of Λ, Λ¯ in e+e− annihilation at a c.m. energy of 29 GeV has been measured with the time-projection-chamber detector at PEP. The average Λ, Λ¯ multiplicity has been measured to be 0.197 ± 0.012(stat.) ±0.017(syst.). Λ−Λ¯ pairs have been observed in jets for the first time, and the average number of Λ−Λ¯ pairs per event has been measured to be 0.042 ± 0.017 ± 0.014.
No description provided.
No description provided.
No description provided.
We report a measurement of the reaction γγ→K+K−π+π− in both tagged and untagged events at PEP. The cross section rises with invariant γγ mass to about 15 nb at 2 GeV and falls slowly at higher masses. We find clear evidence for the processes γγ→φπ+π− and γγ→K*0(892)Kπ. Upper limits (95% C.L.) of 1.5 and 5.7 nb in the mass range from 1.7 to 3.7 GeV are obtained for φρ0 and K*0K¯*0 production, respectively.
No description provided.
No description provided.
Untagged sample, (non-resonant).
This paper reports the results of an experiment measuring the parameters of various electroproduction reactions for a range in the electroproduction variables 0.7<Q2<4 GeV2 and 2<W2<16 GeV2. This report is limited to nondiffractive exclusive channels, with detailed results regarding the πΔ final states, statistically limited results for KΛ final states, and upper limits on the production of a number of event topologies containing a single unseen neutral particle.
No description provided.
No description provided.
No description provided.
Evidence for a narrow state decaying into an F meson and a photon has been obtained in e+e− annihilation events at 29-GeV c.m. energy. This state lies 139.5 ± 8.3(stat.) ± 9.7(syst.) MeV above the F-meson mass and is consistent with the expected F* meson. The F mesons are identified by a peak in the K+K−Kπ± mass at 1.948±0.028±0.010 GeV.
IN (K+K-PI+) THE AUTHORS INCLUDE OTHER DECAY MODES SUCH AS (AK*0 K+),(PHI PI+),(K+ K- PI+,PI0),(K+ K- MU+ NU) WHICH CANNOT BE RESOLVED.
The inclusive production cross sections and transverse momentum distributions of K*0 and KS0 mesons in e+e− annihilation at a center-of-mass energy of 29 GeV have been measured by means of the time projection chamber detector in the PEP-4 experiment. The mean multiplicites are found to be 0.49 ± 0.04(stat.) ± 0.07(syst.) (K*0+K―*0) and 1.22 ± 0.03(stat.) ±0.15(syst.) (K0+K―0) per event.
No description provided.
No description provided.
No description provided.
Production of φ mesons in e+e− annihilation at a center-of-mass energy of 29 GeV has been observed with the time-projection chamber detector at the PEP storage ring. The φ production rate has been measured in the energy range 0.075<x<0.55 (x=2Eφs), giving 0.077±0.012(stat)±0.016(syst) φ's per event. The average value of pt2 relative to the thrust axis is 1.0±0.4 (GeV/c)2.
No description provided.
EXTRAPOLAATION TO ALL X USES LUND MONTE CARLO PREDICTIONS.
ERRORS ARE BOTH STATISTICAL AND SYSTEMATIC. PT IS MEASURED RELATIVE TO THE EVENT THRUST AXIS, AND IS FOUND TO HAVE A MEAN VALUE OF 1.0 +- 0.4 GEV.
The production of the ω meson by virtual photons has been measured as a function of Q2 and W. The ratio of ω production to ρ0 production is independent of Q2 in contrast to indications at lower values of W.
We have measured exclusive ρ0, ω, and φ meson electroproduction at the Cornell Wilson Synchrotron. The final ρ0 data sample included 4637 four-constraint e+p→e+π++π−+p events, with incident energy E=11.5 GeV and electroproduction variables Q2 and W in the region 0.7<Q2<4 GeV2 and 1.9<W<4 GeV. We find that the width of the forward ρ0 diffraction peak increases rapidly as the lifetime of the intermediate hadron states decreases below cΔτ=1 fm and that the peak is wider for longitudinal ρ0 than it is for transverse ρ0. The longitudinal-transverse cross-section ratio Rp=σLσT, obtained assuming s-channel helicity conservation, becomes constant at high Q2. At fixed W the diffractive vector-meson-dominance (VMD) model reproduces the Q2 dependence of our cross section, σ=(σT+εσL), but is is not able to account for the rapid decrease in the cross section with increasing W we observe. We find that σωσρ depends on W but is independent of Q2 for 0.7<Q2<3 GeV2 and 2.2<W<3.7 GeV. However, σω is substantially larger than the diffractive VMD cross section. Our results for σφ are consistent with the Q2 dependence of the diffractive VMD model for 0.8<Q2<4 GeV2 and 2<W<3.7 GeV, but this model again fails to predict the W dependence we observe.
FOUR CHANNEL FIT TO TWO PION PRODUCTION ASSUMING NO INTERFERENCE.
DEPENDENCE OF TOTAL, LONGITUDINAL (L) AND TRANSVERSE (U) DIFFERENTIAL CROSS SECTIONS ON C*DELTA(TAU), THE FORMATION TIME FOR VIRTUAL INTERMEDIATE HADRON STATES. DELTA(TAU) IS 1/DELTA(E) WHERE DELTA(E) IS E(RF=LAB,P=3) - NU = SQRT(NU**2 + Q2 + M(RHO)**2) - NU.
No description provided.
The cross section for the fully constrained reaction ep→eppp¯ has been determined as a function of the electroproduction variables Q2 and s, in the range 0.7<Q2<3 GeV2 and 8<s<16 GeV2. Evidence is presented and cross-section estimates are made for resonances in the final-state p¯p system.
The cross section for virtual photon are derived from E- P cross section bydividing on the virtual-photon flux factor.
The cross section for virtual photon are derived from E- P cross section bydividing on the virtual-photon flux factor.
Bose-Einstein correlations between like-sign pions have been investigated in e+e− annihilation at √s =29 GeV using the Time Projection Chamber detector at the SLAC e+e− storage ring PEP. The production rate of like-sign pion pairs with small relative momentum is found to be increased by more than 50% over the rate expected for uncorrelated production of pions. From the correlation length, a typical source radius of 0.65 fm is derived. Data are consistent with a spherical shape of the pion source. No dependence of radius or correlation strength on the event multiplicity is observed.
Forum