Nucleon Isobar Production in Proton-Nucleon Collision at 6 GeV/c Incident Proton Momentum

Angular and momentum distributions as well as grain densities of charged secondaries emitted in inelastic proton-nucleon interactions are measured. The cross-section of the Δ (1236) isobar production in the events of the type pp →pnπ⁺ is calculated. The theoretical predictions of both the isobar and the O.P.E. model are compared with the experimental data. The transverse momentum distribution of both pions and protons is presented and explained by various theoretical models.     

Structure of final states with a high transverse momentum π0 in proton-proton collisions

We present a study of the final state structure in proton-proton collisions (√s = 53 GeV) where a large transverse momentum π⁰ (p_t > 2 GeV/c) is produced at an angle of 90°. Charged secondaries have been detected and momentum analysed in the split field magnet detector at the CERN Intersecting Storage Rings. The large angular coverage of this detector extends over ±2.5 units of rapidity and ±30° of azimuth with respect to the trigger π⁰, both towards and away from it. In each of these directions, where we observe similar strong correlations, we present charged particle distributions, in rapidity and momentum. In the hemisphere containing the trigger π⁰ we have measured the cross section for inclusive production of large transverse momentum ?^± mesons. In the opposite hemisphere the data exhibit several features predicted by hard scattering quark-parton models: coplanarity and short-range rapidity correlation for the large transverse momentum secondaries as well as a transverse momentum sharing distribution similar to that observed in deep inelastic electro-production and in e⁺e^? collisions.     

An analysis of energetic cosmic ray interactions in graphite

Fifty two high energy cosmic ray interactions in graphite have been analysed. The analysis strongly suggests that some of the characteristics of high energy interactions are dependent on the total transverse momentum,Σp _t, of allγ-rays in an interaction. Out of the 52 events analysed, 29 haveΣp _t⩽2.5 GeV/c and the rest haveΣp _t>2.5 GeV/c; the former are called smallp _t events while the latter are designated as largep _t events. For these two types of events, the characteristics investigated are: (a) fractional energy distribution ofγ-rays, (b) the invariant mass ofγ-rays and (c) the energy distribution ofγ-rays in the emission system.     

Photoproduction of K 0 and Λ at HERA and a comparison with deep inelastic scattering

Inclusive K ⁰ and Λ 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 〈Q ²〉 = 23 GeV². 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.     

Multiparticle emission in the interactions of hadrons with complex nuclei at incident momenta from 2 to 4 GeV/c

The charged secondary particles emitted in inelastic reactions of 4 GeV/cπ⁺ and π^? with the nuclei Be, Cu and Ta are thoroughly studied in their multiplicities, particle correlations and the distributions of kinematical variables, with the 1 m hydrogen bubble chamber into which the three nuclear target plates were installed. The numbers of charged secondaries emitted in the π^?(2.3 GeV/c), π⁺(2 GeV/c) and p(4 GeV/c) reactions are also investigated. From these data, characteristic features of the multiplication process of secondaries in nuclear matter are clarified. The experimental results are compared with the calculation of an intra-nuclear cascade model which takes into account the process of pion absorption by two-nucleon clusters in the nucleus. It is found that the experimental results on the properties of charged secondaries are consistently explained by the model. The model can also give an account of the experimental finding that fairly high momentum protons are emitted from the heavier nuclei into the backward hemisphere in the lab system.     

Inclusive single-particle distributions and transverse momenta of forward produced charged hadrons in μp scattering at 470 GeV

Using data from the Fermilab fixed target experiment E665, general properties of forward produced charged hadrons in μp interactions at a primary muon energy of 470 GeV are investigated. The normalized inclusive singleparticle distributions for Feynman-x D(xF ) and for the transverse momentum D(p ² _t , xF ) are measured as a function of W and Q ². The dependence of the average transverse momentum squared 〈p ² _t〉 on xF , W and Q ² is studied. The increasing contribution from diffractive production as Q ² decreases leads to a reduction of the average charged hadron multiplicities at low (positive) xF and an enhancement at large xF , for Q ² ? 10 GeV². It also reduces 〈p ² _t〉 for Q2 ? 5 GeV2 and 0.4 ? xF < 1.0.     

Impulse approximation in QCD,Parton's pT-distribution and application to deep inelastic process

The recently formulated theory of the impulse approximation in QCD is developed further. The integro-differential equation describing the evolution of the parton's distribution function is solved. The formalism is applied to compute R = σ_L/σ_T in deep inelastic electron scattering and the average transverse momentum 〈k_T〉 of the Drell-Yan pairs. The cross section formula for the latter process is significantly different from the one recently conjectured. Agreement with recent data is good in both cases.     

宇宙线高能粒子与液体闪烁体的核相互作用

利用放置在海拔3185米处的多板云室,以液体闪烁体作靶,研究宇宙线高能粒子产生的核相互作用。本文分析了18个由荷电粒子引起的核作用事例,用Castagnoli公式求得初能平均值E₀=(41±8)Bev,荷电粒子平均多重性n_s=4.9±0.3,以x=lgγ_ctgθ_l为变量作次级粒子的角分布,发现dN/dx分布可能存在着两个峯,文中试用二心模型对此角分布进行了讨论。 关键词：     

Transverse momenta of high-η charged particles emitted in Au+Au collisions

This work demonstrates that the mean transverse momentum of charged particles at large pseudo-rapidities can be reliably derived from measurements of the complete charged-particle multiplicity distributions and using information from measurements of p _T spectra at mid-rapidity by applying energy conservation requirements. As an example, the mean p _T of charged particles emitted at η=4.6 is found to be 〈p _T 〉=0.305 GeV/c for the 0–3% most central Au+Au collisions at $\sqrt {s_{NN} } = 130$ GeV.     

Multiplicity of charged particles in interactions of neutrons with protons,carbon and neon nuclei in the momentum range (1–200) GeV/c

The data on the multiplicity of charged secondaries produced in inelastic np, n¹²C and n²⁰Ne interactions in the primary momentum range (1–200) GeV/c are presented.     

A constituent quark model for particle production in collisions between hadrons

It is shown that a constituent picture of hadrons, with no other fundamental assumption than that only one constituent in each hadron interacts with one constituent in the other hadron, explains several features of particle production in high-energy collisions. We obtain KNO scaling of the particle multiplicity, a neutral for multiplicity for fixed charged multiplicity which is independent of the energy, and a rapidity distribution of the central fireball which depends on n/〈n〉 only. Numerical applications show that the quark momentum distribution which reproduces the experimental data in strong interactions is very similar to the valence quark momentum distribution derived from deep inelastic scattering experiments.     

Transverse momentum spectrum of mesons produced in high energy nucleus-nucleus collisions

The momentum of all charged mesons produced in 19 high energy, high multiplicity nucleus-nucleus collisions of cosmic rays in emulsion have been measured. The transverse momentum distribution differs qualitatively from proton-proton collisions at comparable energies. One possible interpretation is in terms of a transverse explosion with effective temperature T=78 MeV and transverse flow velocity υ=0.61c.     

Collective dynamics at RHIC

We discuss the strong collective flow effects, 〈v ₂〉 and 〈β _t 〉, observed at RHIC (√ ^s NN=130 GeV). We argue that part of the collectivity could have already developed at partonic stage. To ‘see’ the partonic effects directly, measurements of multi-strange baryons like Ξ, Ω and charmed particles like J/ψ transverse momentum distributions are important. They provide one of the possible keys to the discovery of collective modes with the partonic (quarks and gluons) degrees of freedom.     

Modified Hagedorn formula including temperature fluctuation: Estimation of temperatures at RHIC experiments

We have systematically estimated the possible temperatures obtained from an analysis of recent data on p_t distributions observed at RHIC experiments. Using the fact that the observed p_t distributions cannot be described by the original Hagedorn formula in the whole range of transverse momenta (in particular above 6 GeV/c), we propose a modified Hagedorn formula including temperature fluctuation. We show that by using it we can fit p_t distributions in the whole range and can estimate consistently the relevant temperatures, including their fluctuations. PACS 25.75.-q; 12.40.Ee; 02.50.Ey     

The magnitude of the parton intrinsic transverse momentum

We analyze data on the transverse momentum distribution of dimuons produced by 22 GeV and 16 GeV π^? incident on a Cu target. We evaluate the quantum chromodynamic lowest order perturbation contributions and also introduce an intrinsic transverse momentum k_T on the partons relative to their parent hadrons. The analysis of our data leads to 〈k_T〉=0.30?0.35 GeV. We discuss our result in comparison with analyses of data at higher energies.     

Study of data on the associated momentum on the trigger side in highP T hadron production

The British-French-Scandinavian collaboration has recently studied the non trigger charged mean momentum in different rapidity regions on the trigger hemisphere, 〈p _x〉, in the collision of two hadrons at the CERN Intersecting Storing Rings (ISR). In particular, they give for the rapidity regions |y|<0.5 and |y|<1 the values of the slope, α, of 〈p _x〉 with the trigger momentum,p _T ^t . Several authors have analysed those values of α in the framework of hard scattering models which predict values independent ofp _T ^t for 〈z _c〉, the longitudinal momentum fraction of the outgoing hard scattered system taken by the trigger. From this analysis they give estimates of 〈z _c〉 of very difficult reconcilliation with those calculated in the Feynman, Field and Fox hard scattering model or in the QCD treatment of highp _T hadron production. The authors of the present paper have looked for, and found, other data whose model independent analysis is more feasible than that of the data mentioned above. More specifically, we analyse in the framework of the hard scattering models, but otherwise model independently, data on 〈p _x〉 in two other rapidity regions (|y|<3, 2<|y|<3) and find that consistence of the average slopes, α, in these two regions is only achieved with mean values of 〈z _c〉 significantly, increasing withp _T ^t and close in value to those obtained by Feynman et al. [6, 7].     

Structures and angular distributions of slow and relativistic charged particles produced in 7Li-emulsion interactions at 3 GeV/c per projectile nucleon

Experimental results on the multiplicity distributions of various particles produced in the interactions of ⁷Li with emulsion nuclei at a momentum of 3 GeV/c per projectile nucleon are reported. A comparison with data on collisions induced by other nuclei at a nearly identical momentum per nucleon is presented in order to reveal the dependence on the projectile mass. The internal structure of ⁷Li is explored by studying the projectile fragment. The mean multiplicity of shower particles, 〈n _s〉, induced by ⁷Li is found to be less than that in the case of ⁶Li projectiles. The angular distributions of target fragments and relativistic charged secondaries are investigated. No shock-wave phenomena are observed. Forward-to-backward ratios are calculated for each case. The probability distributions for relativistic secondaries produced per unit rapidity are studied in detail, along with the rapidity densities and their dependence on the projectile and the target mass. A comparison of the angular spectra of shower particles produced in central and peripheral collisions supports the limiting-fragmentation hypothesis. The collisions in question seem to become more central with increasing shower-particle multiplicity.     

Evidence for azimuthal correlations in inelastic interactions of56Fe nuclei in emulsion at 2.5A GeV/c

Azimuthal correlations in angles between various types of charged secondary particles from inelastic interactions of relativistic⁵⁶Fe nuclei with the nuclei of nuclear emulsions have been investigated. It is observed that all types of charged secondaries produced are emitted asymmetrically in the azimuthal plane. The degree of azimuthal asymmetry increases with the decrease of impact parameter. We have also observed that particles belonging to different kinematical regions of the nucleus-nucleus interaction (intergroup correlation) have a tendency to be emitted to the opposite sides in the azimuthal plane.     

The missing mass squared dependence of the average charged particle multiplicity in the reaction K+p → KoX++ from 5–16 GeV/c

The average charged particle multiplicity, 〈n_ch(M_X²)〉, in the reaction K⁺p→K^oX⁺⁺ is studied as a function of the mass squared, M_X², of the recoil system X and also as a function of the K^o transverse momentum, p_T, at incident momenta of 5.0, 8.2 and 16.0 GeV/c. The complete data samples yield distributions which are not independent of c.m. energy squared, s, They exhibit a linear dependence on log (M_X²_X/M_o²)[M_o²=1 GeV²] with a change in slope occurring for M_X²≈s/2, and do not agree with the corresponding distributions of 〈n_ch〉 as a function of s for K⁺ p inelastic scattering. Sub-samples of the data for which K^o production via beam fragmentation, central production and target fragmentation are expected to be the dominant mechanisms show that, within error, the distribution of 〈n_ch(M_X²)〉 versus M_X² is independent of incident momentum for each sub-sample separately. In particular in the beam fragmentation region the 〈n_ch(M_X²)〉 versus M_X² distribution agrees rather well with that of 〈n_ch〉 versus s for inelastic K⁺p interactions. The latter result agrees with recent results on the reactions pp → pX and π^?p → pX in the NAL energy range. Evidence is presented for the presence of different production mechanisms in these separate regions.