Inclusive ϱ 0 production in γ p → ϱ 0 + anything is studied at 2.8, 4.7, and 9.3 GeV, using the SLAC linearly polarized backscattered laser photon beam and the 82 inch hydrogen bubble chamber. Over this energy range the inclusive inelastic ϱ 0 cross section rises from 6.0 μb to 20.5 μb. The multiplicity, i.e. the average number of μ 0 mesons per inelastic hadronic event, has an energy dependence consistent with 1n s .
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In 205 GeV / c π − p inelastic interactions, negative particles with transverse momentum greater than 1.0 GeV / c moving forward in the center of mass outnumber similar positive particles by a factor of 3.7 to 1, greatly in excess of the corresponding ratio for small transverse momentum. The asymmetry is reversed in the backward direction. The forward asymmetry is most prominent in 2-, 4-, and 6-prong interactions, but both forward and backward asymmetries are also substantial for higher multiplicity interactions.
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We present stdies of events triggered on two high-pT jets, produced inpp collisions at the CERN Intersecting Storage Rings (ISR) at\(\sqrt s \)=63 GeV, using a large solid angle calorimeter. The cross-section for producing two jets is measured in the dijet mass range 17–50 GeV/c2. A high-statistics sample of dijet events, where each jet has transverse energy above 10 GeV, is used to study the structure of jets and the associated event. We find the longitudinal fragmentation function to be similar to that of jets emerging frome+e− collisions but considerably harder than that observed at the Super Proton Synchrotron (SPS)\(p\bar p\) Collider. A steepening of the fragmentation function is observed when increasing the jet energy. Studies of the charge distribution in jets show that these predominantly originate from fragmenting valence quarks. The transverse energy and particle flows are presented as functions of the azimuthal distance from the jet axis.
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FRAGMENTATION FUNCTION FOR ET(JET) > 10 GEV.
Seventy-one events containing charmed-particle decays have been observed in an experiment using the SLAC Hybrid Facility exposed to a backward-scattered photon beam. Several improvements were made to the apparatus since the previous experiment on charm photoproduction. Results for the charmed-meson lifetimes are consistent with the published results from the previous experiment and the two data samples have been combined yielding a total sample of 136 charm events. After imposing rigorous cuts, 50 neutral, 48 charged, and 2 charged/neutral ambiguous decays remain. From these, the charmed-meson lifetimes are measured to be &=(8.6±1.3−0.3+0 .7)×10−13 sec, &=(6.1±0.9±0.3)×10 −13 sec, and their ratio &=1.4±0.3− 0.1+0.2. The total charm cross section at a photon energy of 20 GeV has been measured to be (62±8−10+15) nb. There is evidence for both DD¯X and D¯Λc+X production with σD¯Λc+X/σcharm=(71± 11±6)%.
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Sixty-two charm events have been observed in an exposure of the SLAC Hybrid Facility toa backward sacttered laser beam. Based on 22 neutral and 21 charged decays we have measured the charmed-meson lifetimes to be τD0=(6.8−1.8+2.3)×10−13 sec, τD±=(7.4−2.0+2.3)×10−13 sec and their ratio τD±τD0=1.1−0.3+0.6. The inclusive charm cross section at a photon energy of 20 GeV has been measured to be 56−23+24 nb. Evidence is presented for a non-DD¯ component to charm production, consistent with (35±20)% Λc+ production and some D*± production. We have found no unambiguous F decays.
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We have studied inclusive production of KS0, Λ, and Λ¯ particles in 20-GeV γp interactions and have found features similar to those observed in both hadronic and leptonic interactions. The production cross sections, charged-particle multiplicities, and average Λ polarization are reported. Inclusive distributions of x and pT are shown and discussed in terms of quark fragmentation models. Production cross sections for K*(890) and Σ*(1385) are also reported.
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Cross sections are presented for the inclusive photoproduction of KS0, Λ, Λ¯, Ξ−, Ξ¯−, Σ0, and Σ*±(1385) at 20 GeV. An upper limit to Ω− production is also given. The data come from 284 000 hadronic events photoproduced in the SLAC 1-m hydrogen-bubble-chamber hybrid facility exposed to a nearly monochromatic, polarized 20-GeV backscattered photon beam. A comparison of the KS0, Λ, Λ¯, and Ξ− rates per inelastic event to π±p data show that γp rates are consistent with being higher than the π±p rates, providing evidence of an ss¯ component of the photon. The pair cross sections for KS0KS0, KS0Λ, KSoΛ¯, and ΛΛ¯ are presented. The xF distributions of the Λ, Λ¯, and Ξ− are compared to a quark-diquark fusion model, giving information on strange-baryon photoproduction mechanisms.
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The ν¯μ charged-current total cross section has been measured with the Fermilab 15-ft bubble chamber plus the external muon identifier and internal "picket fence." Beam monitoring information used for the flux calculation was obtained from Blair et al., whose detector operated in the same dichromatic beam. The present result, averaged over ν¯μ energies from 5 to 250 GeV, is σE=(0.340±0.019±0.022)×10−38 cm2/(GeV nucleon) for an isoscalar target.
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Forty-seven charm events have been observed in an exposure of the SLAC Hybrid Facility bubble chamber to a 20-GeV backward-scattered laser beam. Thirty-seven events survive all the necessary cuts imposed. Based on this number the total charm cross section is calculated to be 63−28+33 nb.
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We present a new measurement of the total photoproduction cross section performed with the H1 detector at HERA. For an average centre of mass energy of 200GeV a value of $\sigma_{tot}~{\gamma{p}}= 165\pm2\pm11\mu$b has been obtained. A detailed analysis of the data in adequate kinematic regions enabled a decomposition of the total cross section in its elastic, single diffractive dissociation and remaining non-diffractive parts, based on safe assumptions on the double diffractive dissociation contribution.
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Total GAMMA P cross section.
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