Hadron Production Properties Research Articles

Overview of the Results from the BRAHMS Experiment

An overview of the most important experimental results obtained in the first three running years with the BRAHMS experiment from Brookhaven National Laboratory(USA) is presented. The design of the experiment permits to measure the interesting physical quantities in a large ranges of rapidity and transverse momentum. Therefore, properties of hadron production vs rapidity and transverse momenta are presented.

Thermodynamic interpretation of statistical semi-inclusive model

A simple picture of high-energy hadron-hadron scattering, consisting of a slight deceleration of the incoming particles followed by thermalization, allows to account for the general features of multihadron production and to derive the main parameters of the empirically developed semi-inclusive statistical model. The dependence exp[-p2T/>p2T<] is expected forpT pion distribution. The picture agrees with the universal properties of hadron production in p-p, deep inelastic and electron-positron scattering.

Scaling properties of hadron production in the Ising model for quark-hadron phase transition

Earlier study of quark-hadron phase transition in the Ginzberg-Landau theory is reexamined in the Ising model, so that spatial fluctuations during the transition can be taken into account. Although the dimension of the physical system is 2, as will be argued, bothd=2 andd=4 Ising systems are studied, the latter being theoretically closer to the Ginzberg-Landau theory. The normalized factorial momentsF q are used to quantify multiplicity fluctuations, and the scaling exponentν is used to characterize the scaling properties. It is found by simulation on the Ising lattice thatν becomes a function of the temperatureT nearT c . The average value ofν over a range ofT<T c agrees with the value of 1.3 derived analytically from the Ginzberg-Landau theory. Thus the implications of the mean-field theory are not invalidated by either the introduction of spatial fluctuations or the restriction to a 2D system.

Scaling properties of hadron production in the Ising model for quark-hadron phase transition

Earlier study of quark-hadron phase transition in the Ginzberg-Landau theory is reexamined in the Ising model, so that spatial fluctuations during the transition can be taken into account. Although the dimension of the physical system is 2, as will be argued, both d=2 and d=4 Ising systems are studied, the latter being theoretically closer to the Ginzberg-Landau theory. The normalized factorial moments F_q are used to quantify multiplicity fluctuations, and the scaling exponent \nu is used to characterize the scaling properties. It is found by simulation on the Ising lattice that \nu becomes a function of the temperature T near T_c. The average value of \nu over a range of T<T_c agrees with the value of 1.3 derived analytically from the Ginzberg-Landau theory. Thus the implications of the mean-field theory are not invalidated by either the introduction of spatial fluctuations or the restriction to a 2D system.

Measurement of hadron production and three-jet event properties at petra

We have performed a high statistics measurement of the production rate and the energy flow pattern of hadron events between √ s=33 and 36.7 GeV. The data show no evidence for the production of a new quark with charge 2 3 e . Planar events in e +e −→hadrons are shown to have three well separated jets. The production rate and the shape of three-jet events are compared with many models and we find that only the QCD model can explain the data.

High pT hadron production in photon-photon collisions

We have studied the properties of hadron production in photon-photon scattering with tagged photons at the e +e − storage ring PETRA. A tail in the p T distribution of particles consistent with p T −4 has been observed. We show that this tail cannot be due to the hadronic part of the photon. Selected events with high p T particles are found to be consistent with a two-jet structure as expected from a point-like coupling of the photons to quarks. The lowest-order cross section predicted for γγ → q q , σ = 3 Σ e q 4 · σ γγ → μμ , is approached from above by the data at large transverse momenta.

The fractional momentum distribution in p-p collisions compared with e+e− annihilation

The fractional momentum distribution for hadrons produced in p-p interactions at √s=62 GeV has been studied in terms of the effective energy available for particle production,Ehad, once the leading baryon energy has been subtracted. This has been done comparing the experimental data with a Monte Carlo prediction based on i) the inclusivexF distributions of the protons produced in p-p collisions integrated overpT, ii) the inclusive fractional momentum distribution of the hadrons produced in e+e−, iii) the average charged multiplicity 〈nch〉 as obtained in e+e−. The results show that our analysis in terms of the effective energy available for particle production in p-p interactions,Ehad, can be extended to all ranges of available energies and can account for the inclusive fractional momentum particle production in p-p interactions without any special model, but in terms of the known properties of hadron production in e+e− annihilation.