None
No description provided.
Inclusive production of ϱ0,K*±(892), andf is studied in\(\bar p\)p interactions at 12 GeV/c. The inclusive cross sections for ϱ0,K*±(892), andf are found to be 6.7±0.3 mb, 1.0±0.2 mb, and 1.4±0.3 mb, respectively. The differential cross sections are presented as a function of c.m. rapidity, Feynmanx and square of the transverse momentumpT2. Comparison with the correspondingpp data shows some interesting differences which can be attributed to the\(\bar p\)p annihilation. The results are compared with the predictions of the quark fusion model.
No description provided.
No description provided.
No description provided.
Results are reported of an experiment to measure the cross section for production of the D*+ (D*−) in 200-GeV/c π−N interactions. We observe 78 ± 26 events corresponding to a D*-production cross section dσdy=1.6±0.5 μb at y=0.
No description provided.
We report a high-statistics study of the reaction p+W→μ++μ−+X with use of an intense 400-GeV/c proton beam, a magnetized-iron beam dump, and a wide-acceptance detector. Using data near xF=0, we have extracted the nucleon sea-quark distribution and find it to be a factor 1.6±0.3 larger than that obtained by inelastic charged-current neutrino scattering. We then compare the Drell-Yan prediction with our data including the previously unexplored region of large xF and find excellent agreement for a wide range of μ-pair invariant mass.
Dimuon mass mass distribution at XFP=0.1.
Dimuon production for varying mass as function of XFP.
Dimuon production for varying mass as function of XFP.
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 → ϱ 0 ϱ 0 → π + π − π + π − . The cross section, which is small just above the four-pion threshold, exhibits a large enhancement near the ϱ 0 ϱ 0 threshold.
Axis error includes +- 0.0/0.0 contribution (THE QUOTED ERRORS INCLUDE VARIOUS SYSTEMATIC ERRORS ADDED QUADRATICALLY).
The final states of charged hadrons produced in 280 GeV μp scattering are analysed with respect to their planarity and jet structure. Distributions of p ⊥ 2 in and p ⊥ out 2 are presented. A two jet structure in the forward hemisphere is observed for events with high p ⊥ tracks are predicted by QCD models.
PTIN**2 is the sum of the PTIN components squared.
PTOUT**2 is the sum of the PTOUT components squared.
Measurements of the reaction γ p → p π + π − π + π − are presented, in which π + π − π + π − systems with masses up to 3 GeV are produced from fragmentation of the incident photon. The reaction is dominated by production of the large peak of the ϱ′(1600) meson and, at higher masses ≳2 GeV, y production of jet-like 4 π systems. The ϱ′(1600) meson is produced by a predominantly s -channel helicity conserving mechanism. At higher masses there are also indications of ϱπ peaks, of masses 1.3 GeV (the A 2 meson) and 1.75 GeV, produced with a recoiling π meson by a mechanism consistent with the Deck effect.
CORRECTED FOR TAILS OF BREIT-WIGNER RESONANCE USED IN FIT AND ALLOWING FOR 10 PCT BACKGROUND.
Inclusive cross sections for production of π+, π−, p, d, H3, He3, and He4 have been measured at laboratory angles from 10° to 145° in nuclear collisions of Ne + Naf, Ne + Cu, and Ne + Pb at 400 MeV/nucleon, C + C, C + Pb, Ne + NaF, Ne + Cu, Ne + Pb, Ar + KCl, and Ar + Pb at 800 MeV/nucleon, and Ne + NaF and Ne + Pb at 2.1 GeV/nucleon. The production of light fragments in proton induced collisions at beam energies of 800 MeV and 2.1 GeV has also been measured in order to allow us to compare these processes. For equal-mass nuclear collisions the total integrated yields of nuclear charges are well explained by a simple participant-spectator model. For 800 MeV/nucleon beams the energy spectra of protons at c.m. 90° are characterized by a "shoulder-arm" type of spectrum shape with an exponential falloff at high energies, whereas those of pions are of a simple exponential type. The inverse of the exponential slope, E0, for protons is systematically larger than that for pions. This value of E0 is larger for heavier-mass projectiles and targets. It also increases monotonically with the beam energy. The angular anisotropy of protons is larger than that of pions. The yield ratio of π− to total nuclear charge goes up with the beam energy, whereas the yields of composite fragments decrease. The ratio of low-energy π− to π+, as well as that of H3 to He3, is larger than the neutron to proton ratio of the system. The spectrum shape of the composite fragments with mass number A is explained very well by the Ath power of the observed proton spectra. The sizes of the interaction region are evaluated from the observed coalescence coefficients. The radius obtained is typically 3-4 fm. The yield ratio of composite fragments to protons strongly depends on the projectile and target masses and the beam energy, but not on the emission angle of the fragments. These results are compared with currently available theoretical models. NUCLEAR REACTIONS Ne + NaF, Ne + Cu, Ne + Pb, EA=400 MeV/nucleon; C + C, C + Pb, Ne + NaF, Ne + Cu, Ne + Pb, Ar + KCl, Ar + Pb, EA=800 MeV/nucleon; Ne + NaF, Ne + Pb, EA=2100 MeV/nucleon; p + C, p+ NaF, p + KCl, p + Cu, p + Pb, E=800 MeV; p + C, p + NaF, p + KCl, p + Cu, p + Pb, E=2100 MeV; measured σ(p,θ) for π+, π−, p, d, H3, He3, and He4.
No description provided.
No description provided.
No description provided.
We have measured the reaction ee → μμ and ee → ττ at center of mass energies from 9.4 to 31.6 GeV. The production cross sections are in agreement with the predictions of quantum electrodynamics, resulting in cutoff parameter limits of 70–100 GeV at 95% c.l. The branching ratio for τ → μν ν has been determined as [1.78 ± 2.0 (statist.) ± 1.8(syst.)]% The existence of a new sequential heavy lepton with a mass <14.5 GeV is excluded at 95% c.l.
No description provided.
No description provided.
The energy dependence of the average of the charged multiplicity and its dispersion in π + /K + /p interaction on protons at 147 GeV/ c is found to be the same as in e + e − annihilations if an “effective energy” variable is used instead of the total energy. The effective energy S eff is defined as the invariant mass of all secondaries left after the two leading particles have been removed. Fitting the expression aS eff b to the average charge multiplicity 〈 n ch 〉, we find the power b to be in good agreement with the value of 0.25 predicted by Fermi's statistical model and by Landau's hydrodynamical model.
BINS IN WEFF SELECTED SO AS TO YIELD 200 EVENTS IN EACH BIN.
200 EVENTS IN EACH BIN IN WEFF.
50 EVENTS IN EACH BIN IN WEFF.
Forum