Inclusive hadron production in muon-proton inelastic scattering has been measured for q2>0.5 (GeV/c)2 and 10<ν<135 GeV. The results are presented in the form of the transverse momentum distribution of charged hadrons and the hadron invariant structure function F(x′). Results are given for different regions of q2 and s.
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Inclusive and semi-inclusive cross sections for gp0 production in 100, 200, and 360 GeV/c π−p interactions are presented. Differential cross sections for ρ0 production as functions of c.m. rapidity and transverse momentum are compared with the corresponding differential cross sections for pion production. Effects of various methods of estimating background on the values obtained for ρ0 production cross sections are discussed. About 10% of the final-state charged pions appear to come from ρ0 decay. Thus, while ρ0 production and decay is a significant source of final-state pions, other sources must contribute the majority of the produced pions.
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We present results on the jet structure observed in multihadronic events produced by e+e− annihilation in the Mark I magnetic detector at SPEAR. The evidence for jet structure and the jet-axis angular distribution are reported. We give inclusive distributions of the hadrons in Feynman x, rapidity, and transverse momentum relative to the jet axis.
Observed particle PT with respect to jet axis for events with three or more detected charged particles.
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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).
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CHARGED PARTICLE MULTIPLICITY DISTRIBUTIONS.
Inclusive $K^0$ and $\Lambda$ photoproduction has been investigated at HERA with the H1 detector at an average photon-proton center of mass energy of 200 GeV in the transverse momentum range 0.5 <p_t <5 GeV. The production rates as a function of $p_t$ and center of mass rapidity are compared to those obtained in deep inelastic scattering at $\av{Q^2}=23 GeV^2$. A similar comparison is made of the rapidity spectra of charged particles. The rate of strangeness photoproduction is compared with $p\bar p$ measurements. The observations are also compared with next-to-leading order QCD calculations and the predictions of a Monte Carlo model.
Additional systematic uncertainty given above.
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A thrust analysis of Large-Rapidity-Gap events in deep-inelastic ep collisions is presented, using data taken with the H1 detector at HERA in 1994. The average thrust of the final states X, which emerge from the dissociation of virtual photons in the range 10 < Q2 < 100 GeV2, grows with hadronic mass M_X and implies a dominant 2-jet topology. Thrust is found to decrease with growing Pt, the thrust jet momentum transverse to the photon-proton collision axis. Distributions of Pt2 are consistent with being independent of MX. They show a strong alignment of the thrust axis with the photon-proton collision axis, and have a large high-Pt tail. The correlation of thrust with MX is similar to that in e+e- annihilation at sqrt(see)=MX, but with lower values of thrust in the ep data. The data cannot be described by interpreting the dissociated system X as a qqbar state but inclusion of a substantial fraction of qqbarg parton configurations leads naturally to the observed properties. The soft colour exchange interaction model does not describe the data.
PT distribution of the photon-originated jet relative to the to the GAMMA* P collision axis in the jet center-of-mass frame, divided by the total GAMMA* P cross section for the respective M_x bin. Jet momentum defined as vector sum of momenta in the positive(negative) thrust hemisphere (thrust jet momentum).
PT distribution of the photon-originated jet relative to the to the GAMMA* P collision axis in the jet center-of-mass frame, divided by the total GAMMA* P cross section for the respective M_x bin. Jet momentum defined as vector sum of momenta in the positive(negative) thrust hemisphere (thrust jet momentum).
PT distribution of the photon-originated jet relative to the to the GAMMA* P collision axis in the jet center-of-mass frame, divided by the total GAMMA* P cross section for the respective M_x bin. Jet momentum defined as vector sum of momenta in the positive(negative) thrust hemisphere (thrust jet momentum).
Photoproduction data collected with the H1 detector at HERA in 1994 are used to study the cross-sections for inclusive charged particle production and the structure of the photon. The differential cross-sections dsigma/dpT2, for |eta| < 1 in the HERA laboratory frame, and dsigma/deta for pT > 2 GeV/c and pT > 3 GeV/c have been measured. Model calculations of these cross-sections, based on perturbative QCD, indicate that the results are sensitive to the parton densities of the photon as well as to higher order effects, which are phenomenologically treated by multiple interactions. This sensitivity is exploited to determine the leading order x_gamma distribution of partons in the photon using a new method based on high pT charged particles. The gluon content of the photon is extracted and found to rise with decreasing x_gamma.
Inclusive gamma-p cross section for charged particles in the photoproduction data.
The measured differential pseudorapidity distribution for inclusive chargedparticle production.
Measurements of inclusive production of the Lambda, Xi- and Xi*(1530) baryons in two-photon collisions with the L3 detector at LEP are presented. The inclusive differential cross sections for Lambda and Xi- are measured as a function of the baryon transverse momentum, pt, and pseudo-rapidity, eta. The mean number of Lambda, Xi- and Xi*(1530) baryons per hadronic two-photon event is determined in the kinematic range 0.4 GeV < pt< 2.5 GeV, |eta| < 1.2. Overall agreement with the theoretical models and Monte Carlo predictions is observed. A search for inclusive production of the pentaquark theta+(1540) in two-photon collisions through the decay theta+ -> proton K0s is also presented. No evidence for production of this state is found.
Differential cross section for LAMBDA production.
Differential cross section for LAMBDA production.
Differential cross section for XI- production.
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