The spectrum of protons produced in pp collisions at 31 GeV total energy

Data are reported on the distributions in longitudinal and transverse momentum of protons produced in the range 0.5 < x < 1.0 (x = Feynman variable) and 0.2 < p_T² < 1.8 (GeV/c)² in proton-proton collisions at 31 GeV c.m. energy at the CERN ISR. The invariant inelastic cross section shows a peak at high longitudinal momenta. The shape of this peak suggests substantial production of states with masses up to at least 7 GeV.     

High transverse momentum π0 production by π− and π+ on protons at 280 GeV/c

The inclusive cross sections for π⁰ production by π^? and π⁺ on protons have been measured with a beam momentum of 280 GeV/c using a fine grained electromagnetic calorimeter and the CERN Omega spectrometer. The transverse momentum and Feynmanx _F ranges covered are 4.0<p _T <7.0 GeV/c and ?0.45<x _F <0.6 respectively. The data are compared with leading order QCD calculations.     

High transverse momentum prompt photon production by π− and π+ on protons at 280 GeV/c

The inclusive cross sections for prompt photon production by π^? and π⁺ on protons have been measured with a beam momentum of 280 GeV/c using a fine grained electromagnetic calorimeter and the CERN Omega spectrometer. The transverse momentum and Feynmanx _F ranges covered are 4.0<p _T <7.0GeV/c and ?0.45<x _F <0.55 respectively. A quantitative comparison of the prompt photon cross section with next-to-leading order QCD predictions using Duke and Owens structure functions is performed.     

Spin dependence of the inclusive reaction p + p (polarized) → π0 + X at 24 GeV/c for high-pTπ0 produced in the central region

The spin dependence of π⁰ inclusive production by 24 GeV/c protons has been measured using a polarized target for Fhe Feynman x near 0 in the transverse momentum range 1.0 < p_T < 2.5 GeV/c. The results indicate a negative updown asymmetry growing strongly with p_T and greater than 50% in absolute value for p_T greater than 2 GeV/c.     

Analysis of transverse momentum distributions forpp interactions at 360 GeV/c in the framework of a quark-diquark fragmentation model

Using a quark-diquark fragmentation model, in which either the Field-Feynman or the Lund model is coupled with a quark-diquark distribution function, we study transverse momentum distributions,p _T, for the inclusive reactionspp→hadron +anything at 360 GeV/c. We find that a primordial mean transverse momentum 〈k _T〉?0.4 GeV/c can well reproduce thep _T ² distributions of charged hadrons, π⁰,K _s ⁰ , Λ⁰,K ^* and Σ^* and the Feynmanx?p _T correlations. We confirm that a diquark in a proton plays an important rôle in reproducing thex?p _T correlation of Λ⁰.     

Inclusive production of protons, anti-protons and neutrons in p+p collisions at 158 GeV/c beam momentum

New data on the production of protons, anti-protons and neutrons in p+p interactions are presented. The data come from a sample of 4.8 million inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c beam momentum. The charged baryons are identified by energy loss measurement in a large TPC tracking system. Neutrons are detected in a forward hadronic calorimeter. Inclusive invariant cross sections are obtained in intervals from 0 to 1.9 GeV/c (0 to 1.5 GeV/c) in transverse momentum and from ?0.05 to 0.95 (?0.05 to 0.4) in Feynman x for protons (anti-protons), respectively. p _T integrated neutron cross sections are given in the interval from 0.1 to 0.9 in Feynman x. The data are compared to a wide sample of existing results in the SPS and ISR energy ranges as well as to proton and neutron measurements from HERA and RHIC.     

The transverse momentum of partons in large pT processes

An approximate method is used to investigate the effects of parton transverse momentum in large p_T particle production within the framework of hard scattering models. We derive an approximate expression for the mean bias towards the trigger of each of the two participating partons and find that event one of the partons is biased more than the other, even with a 90° trigger. We treat the transverse momentum of partons and their closely related off-mass-shell behaviour as a perturbation in the equation for the single-particle inclusive cross section, and then expand in a Taylor series. We calculate the first non-zero correction term and find that to this order, the cross section is increased by parton transverse momentum effects by typically a factor of 1.7 for p_T = 3 GeV/c with 〈k_T〉 = 500 MeV/c, or 1.25 for p_T = 3 GeV/c with 〈k_T〉 = 300 MeV/c, and that the correction decreases rapidly with increasing p_T.     

Energy dependence of transverse momentum invariant distribution of pions and neutral kaons in K−p interactions between 14.3 and 70 GeV/c

The energy dependence of the transverse momentum invariant distribution of pions and neutral kaons is studied in K^?p interactions between 14.3 and 70 GeV/c. The large P_T part of the distributions violates the Feynman scaling and, above P_T ? 1.5 GeV/c, appears to be reasonably described by hard scattering models. The variation of the average transverse momentum is also studied as a function of the c.m. reduced longitudinal momentum, and its behaviour is compared to the data obtained via the hadronic shower produced in lepton-hadron interactions.     

Soft photon production in 450 GeV/cp-Be collisions

We have measured the inclusivep _T spectra of soft photons produced at central and backward rapidities in 450 GeV/cp-Be collisions down to 1 MeV/c in transverse momentum. In the region 1<p _T <20 MeV/c an excess of photons over those expected from hadronic decays is observed. This excess is comparable, within systematic errors, with estimates of direct photons produced via hadronic bremsstrahlung. An upper limit is derived on the presence of additional sources of direct photons at small transverse momentum.     

Observation of leading particles in pp interactions with large transverse momentum secondaries at the CERN-ISR

Events with a positive particle of large transverse momentum emitted at medium angles have been studied using the split field magnet spectrometer at the CERN-ISR at a c.m. energy of √s = 52.5 GeV. Positive particles with large longitudinal momentum, |x| > 0.5, i.e., leading particles, associated to large p_T events, are analysed.     

Transverse Momentum Distributions of Charged Particles Produced in Deuteron-Carbon Interactions at 4.2A GeV/c

In this work, the behavior of transverse momentum (p_T) and maximum p_T (p_Tmax) distribution of light-flavored hadrons, produced in deuteron-carbon (dC) interactions at 4.2A GeV/c, is presented. We use the data, provided by the Laboratory of High Energy (LHE) with propane bubble chamber of 2 m of the Joint Institute for Nuclear Research (JINR), Dubna Russia. The results of the experimental data are compared with the predictions of the cascade model, Dubna version. Three regions in terms of the p_T-distributions trend are observed for all types of particles, where p_T ～ 1 and 1.5 GeV/c are the limiting values for pions and protons, respectively, in the region-III, for which the p_T > 0.375 GeV/c. The protons’ contribution to this region is an order of magnitude more than of the mesons and the distribution of the latter decreases faster than of the former. The model cannot predict the experimental results in the region-III, completely, where the number of particles is less than in the experiment.     

Gluon multiple scattering and the transverse momentum dependence of J/ψ production in nucleus-nucleus collisions

A J/ψ meson is mainly formed by gluon fusion for 200 GeV pp collisions. In reactions with nuclei the gluons (g) scatter off other nucleons (N) before fusing to a J/ψ, which thenshows additional transverse momentum p_T. Fitting the value of the parameter σ_gN〈p²_T〉_gN to describe the gluon multiple scattering effect in proton-nucleus data, we can reproduce the p_T distribution of J/ψ production in 200 GeV/A nucleus-nucleus collisions. The origin of the p_T distribution is traced to soft gluon radiation via the Sudakov form factor.     

Gluon tagging in hard proton-proton interactions at the ISR

Events obtained by triggering on a single particle with high transverse momentump _T show a four-jet structure. The two transverse jets are due to the fragmentation of point-like scattered partons. Experimental evidence is presented that highp _T K ^? mesons and their associated jets are produced by hard scattering and subsequent fragmentation of flavour neutral partons with a rather soft structure function. Hence, gluons are a natural source of highp _T K ^? mesons which do not share any valence quark with the incoming protons. The analysis is based upon measurements of short-range quantum number correlations within the trigger jet and of long-range correlations between different jets. The data were obtained at \(\sqrt s\) =62 GeV GeV with the Split Field Magnet Detector (SFM) at the CERN ISR.     

Analysis of Spectral Temperature of Participant Protons in p + 12C Interactions at 4.2 GeV/c Using UrQMD Model

The transverse momentum spectra of protons participated in the collision processes calculated using UrQMD model simulations have been compared with the p_T spectra of participant protons, obtained experimentally in interactions of protons beam with carbon nuclei at momenta of 4.2 GeV/c. Spectral temperatures of participant protons obtained in the experimental and UrQMD model simulated interactions of protons beam with carbon nuclei have been calculated by fitting both spectra with four different fitting functions i.e. Hagedorn Thermodynamic, Boltzmann distribution, Gaussian and exponential functions. These functions are used commonly for describing the hadrons spectra and their spectral temperatures. The most suitable fitting functions among these four functions have also been recommended.

     

Backward emitted protons in interactions of neutrinos with nuclei in photoemulsion

Backward emitted protons with momentump>0.3 GeV/c in interactions of neutrino in the energy range 10–200 GeV with photoemulsion nuclei were investigated. Energy spectrum slope parameter of backward protons was measured to beT ₀=48.9±7.9 MeV. TheA-dependence power index of relative mean yield of backward protons was found to bea=0.68±0.12. A drop in the mean yield of backward protons at the four momentum squared over ～15 (GeV/c)² (the neutrino energy over ～50 GeV) was observed.     

High transverse momentumη production in π− p, π+ p,andpp interactions at 280 GeV/c

The inclusive cross sections for η production by the interactions of 280 GeV/c momentum π^?, π⁺, and proton beams in hydrogen have been measured. The kinematical range covered is ?0.45<x _F <0.45, and 4.0<P _T <7.0 GeV/c for Feynmanx _F and transverse momentum respectively. The η to π⁰ cross section ratios are given for the three reactions. The ratio of π^? p to π⁺ p cross sections for η production in the above kinematic ranges is 1.22±0.08±0.11.     

Direct photon production in proton-antiproton interactions at √s = 24.3 GeV

Direct photons have been studied in pp̄ interactions at √s = 24.3 GeV and in the transverse momentum (p_T) range 3–7 GeV/c(0.25 < x_T < 0.58). The experiment was performed using an internal H₂ cluster the target in the CERN pp̄ Collider. The measured invariant cross section is compared with recent theoretical predictions.     

The transverse energy distribution in hadron-lead collisions

The transverse energy cross-sectiondσ/dE _T has been measured in the pseudorapidity region 0.6<η<2.4 for hadron-lead collisions at 200 GeV/c incident hadron momentum. TheE _T distribution extends to 40 GeV, which is twice the kinematic limit forp-p collisions at the same incident beam momentum. The distribution ofE _T is found to shift towards low pseudorapidities with increasing total transverse energy.     

Influence of the collision centrality upon negative particle production indC, αC and CC interactions at 4.2 GeV/c per nucleon

The influence of collision centrality upon spectra of negative particles produced indC, αC and CC interactions at 4.2 GeV/c per nucleon is studied. The netcharge of secondary particles is used as a measure of collision centrality. Comparison with the nucleon-nucleon collisions and with Dubna intranuclear cascade model is presented. The main features of the momentum, rapidity and angular spectra are compatible with the independent, nucleon-nucleon collision picture. Only in thep _T spectra, the observed particle excess, for low and highp _T , is inconsistent with this approach. In contrast to the pions, the spectra of protons are more sensitive to the collision centrality.     

Inclusive proton and antiproton production in π± hydrogen and π± nucleus interactions at 30 GeV/c

Data on fast protons and antiprotons produced byπ ^± incident on hydrogen and nuclear targets at 30 GeV/c are presented. The results covering the kinematic range 0.32 F <0.54 andp _T >0.2 GeV/c, complete our previous paper. We give results on inclusive cross-sections as a function ofx _F , ofp _T ² and on cross-section ratios. A search for effects of nuclear matter on the production of protons and antiprotons has yielded no major effects beyond final state absorption.