New scaling of charged particle pseudorapidity distributions at collider energies

A new scaling form is proposed for charged particle pseudorapidity (η) distributions on the basis of scaling in the mean hypothesis. Our new scaling accounts well the recent UA5 data of η distributions in various intervals of charged multiplicity for non single-diffractive events at energies \(\sqrt s = 200\) and 900 GeV. Similar scaling of inclusive η distributions is theoretically derived, and the validity of this scaling is assured in comparison with the data of ISR and collider energies.     

A combined model for pseudorapidity distributions in p-p collisions at center-of-mass energies from 23.6 to 7000 GeV

In p-p collisions, the charged particles produced consist of two leading particles and those frozen out from the hot and dense matter created in the collisions. The two leading particles are in the projectile and target fragmentation regions, respectively, which, in this paper, are conventionally supposed to have Gaussian rapidity distributions. The hot and dense matter is assumed to expand according to unified hydrodynamics, a hydrodynamic model which unifies the features of the Landau and Hwa-Bjorken models, and freeze out into charged particles from a space-like hypersurface with a fixed proper time of τFO. The rapidity distribution of these charged particles can be derived analytically. The combined contribution from both leading particles and unified hydrodynamics is then compared against experimental data from a now available center-of-mass energy region from 23.6 to 7000 GeV. The model predictions are consistent with experimental measurements.     

Centrality dependences of the pseudorapidity distributions of charged particles in Au+Au collisions at RHIC energies

By employing the Glauber model, we give the centrality dependences of the numbers of participants and binary nucleon-nucleon collisions in nucleus-nucleus collisions. By taking into account the energy loss of the participants in their multiple collisions, we then present the pseudorapidity distributions of charged particles in nucleus-nucleus collisions as a function of beam energy and impact parameter. Finally, we analyze the centrality dependence of the pseudorapidity of the charged particles in Au＋Au collisions at energies from √SNN=19.6 to 200 GeV. The theoretical results are in good agreement with the experimental observations of the RHIC-PHOBOS collaboration.     

Centrality dependences of the pseudorapidity distributions of charged particles in Au+Au collisions at RHIC energies

By employing the Glauber model, we give the centrality dependences of the numbers of participants and binary nucleon-nucleon collisions in nucleus-nucleus collisions. By taking into account the energy loss of the participants in their multiple collisions, we then present the pseudorapidity distributions of charged particles in nucleus-nucleus collisions as a function of beam energy and impact parameter. Finally, we analyze the centrality dependence of the pseudorapidity of the charged particles in Au+Au collisions at energies from √sNN=19.6 to 200 GeV.The theoretical results are in good agreement with the experimental observations of the RHIC-PHOBOS collaboration.     

Expectations of jet characteristics at TeV energies

We investigate the properties to be expected of jets produced in future accelerators in the TeV energy domain. Current state-of-the-art models for perturbative jet evolution and non-perturbative fragmentation are used together with experimentally realistic methods for jet reconstruction based on the energy flow pattern in a calorimeter.     

Photon production at c.m. energies of 200 and 900 GeV

We present data on photon production in non single-diffractivep \(\bar p\) -collisions at c.m. energies of 200 and 900 GeV. Besides the general properties of photon production, i.e. pseudorapidity distribution and average multiplicity, we also investigate photon-charged two-particle pseudorapidity and multiplicity correlations. We find for the average number of photons in non single-diffractivep \(\bar p\) -collisions 22.2±1.4±2.0 at 200 GeV and 41.4±2.1±3.5 at 900 GeV, where the first error is statistical and the second systematic. The analysis of photon-charged particle multiplicity correlations reveals strong positive correlations between the average number of photons and the number of simultaneously produced charged particles, as expected from FNAL and ISR studies and from our result at 546 GeV. We obtain for the correlation slope 0.95±0.08±0.11 at 200 GeV and 1.09±0.09±0.13 at 900 GeV (first error is statistical and the second systematic). The investigation of photon-charged two-particle pseudorapidity correlations shows that these correlations are of short range and compatible with the observed charged two-particle pseudorapidity correlations. These correlations and the results for the average number of photons as a function of the produced number of charged particles favour the conclusion that photon sources other than π⁰ s contribute significantly to the observed photon yield in non single-diffractivep \(\bar p\) -collisions. For example, if all photons are assumed to come from π⁰ s and η mesons, a η/π⁰ ratio of about 20% is inferred.     

Charged-particle pseudorapidity distributions in Au+Au collisions at RHIC

Using the Glauber model, we present the formulas for calculating the numbers of participants,spectators and binary nucleon-nucleon collisions. Based on this work, we get the pseudorapidity distributions of charged particles as the function of the impact parameter in nucleus-nucleus collisions. The theoretical results agree well with the experimental observations made by the BRAHMS Collaboration in Au+Au collisions at √SNN=200 GeV in different centrality bins over the whole pseudorapidity range.     

Charged-particle pseudorapidity distributions in Au+Au collisions at RHIC

Using the Glauber model, we present the formulas for calculating the numbers of participants, spectators and binary nucleon-nucleon collisions. Based on this work, we get the pseudorapidity distributions of charged particles as the function of the impact parameter in nucleus-nucleus collisions. The theoretical results agree well with the experimental observations made by the BRAHMS Collaboration in Au＋Au collisions at √^SNN=200 GeV in different centrality bins over the whole pseudorapidity range.     

Kaon production in\bar pp interactions at c.m. energies from 200 to 900 GeV

A detailed analysis ofK _s ⁰ production in \(\bar pp\) |<2.5 the average transverse momentum is found to be 0.53±0.07 GeV/c at 200 GeV and 0.62±0.08 GeV/c at 900 GeV, which is an increase with respect to data at c.m. energies below 60 GeV. TheK _s ⁰ production cross sections in inelastic collisions are 29±4 mb at 200 GeV and 63±6 mb at 900 GeV, showing an increase compared to lower energy data. The central kaon density is found to increase as a logarithmic function of energy. At 900 GeV, where statistics are sufficient to allow one to draw conclusions, the average transverse momentum is higher in events with large charged multiplicity than in events with low multiplicity.     

Charged particle multiplicity distributions at 200 and 900 GeV c.m. energy

Multiplicity distributions of charged particles produced in non single-diffractive collisions between protons and antiprotons at centre of mass energies of 200 and 900 GeV are presented. The data were recorded in the UA5 streamer chambers at the CERN Collider, which was operated in a pulsed mode between the two energies. A new method to correct for acceptance limitations and inefficiencies based on the principle of maximum entropy has been used. Multiplicity distributions in full phase space and in intervals of pseudorapidity are presented in tabular form. The violation of KNO scaling in full phase space found by the UA5 group at an energy of 546 GeV is confirmed also at 200 and 900 GeV. The shape of the 900 GeV distribution in full phase space is narrower in the peak region than at 200 GeV but exhibits a pronounced high multiplicity tail. The negative binomial distribution fits data at 200 GeV in all pseudorapidity intervals and in small intervals at 900 GeV. In large intervals at 900 GeV, however, the negative binomial distribution. Fits to the partially coherent laser distribution are also presented as well as comparisons with predictions of the Dual Parton, the Fritiof and the Pythia models.     

Correlations in quasi-elastic proton-proton scattering at total c.m. energies of 23 and 31 GeV

Data are reported on angular and rapidity (η) distributions of a charged particle c produced in quasi-elastic proton-proton scattering (p+p→p+c+anything) at the CERN ISR.     

TeV strings and the neutrino-nucleon cross section at ultrahigh energies

In scenarios with the fundamental unification scale at the TeV one expects string excitations of the standard model fields at accessible energies. We study the neutrino-nucleon cross section in these models. We show that duality of the scattering amplitude forces the existence of a tower of massive leptoquarks that mediate the process in the s channel. Using the narrow-width approximation we find a sum rule for the production rate of resonances with different spin at each mass level. We show that these contributions can increase substantially the standard model neutrino-nucleon cross section, although they seem insufficient to explain the cosmic ray events above the Greisen-Zatsepin-Kuz'min cutoff energy.     

Centrality dependence of pseudorapidity distributions of baryons in heavy ion collisions at RHIC

The energy and centrality independence of the limiting fragmentation for produced mesons have been used to extract the reduced pseudorapidity (η′ = η − η _beam ) distributions of charged baryons at forward rapidity. The distribution crosses at η′ ≈ = −1 suggesting the prominence of beam protons above that rapidity. The loss of beam rapidity has been extracted which has been found to increase with centrality.     

Advanced GAMMA-400 γ-ray telescope for recording cosmic γ rays with energies up to 3 TeV

The results of calculation and measurements performed on prototypes of the calorimeter, time-of-flight, and coordinate systems of the advanced GAMMA-400 γ-ray telescope, designed for studying diffuse cosmic γ rays and search for γ-ray lines arising after annihilation of neutralinos (dark matter particles), are reported.     

A description of pseudorapidity distributions in p-p collisions at center-of-mass energy from 23.6 to 900 GeV

In the context of the combined model of evolution-dominated hydrodynamics + leading particles, we discuss the pseudorapidity distributions of charged particles produced in p-p collisions. A comparison is made between the theoretical predictions and experimental measurements. The combined model works well in p-p collisions in the whole available energy region from √s=23.6 to 900 GeV.     

Scaling predictions for multiplicity distributions at LEP

This paper presents a study of the charged particle multiplicity distributions for thee ⁺ e ^? annihilation. It is shown that the KNO-G scaling, the concept which turned out to be very successful in thepp collisions, is also valid for thee ⁺ e ^?, data. Using this concept the predictions for the multiplicity distributions at LEP are given. The possible explanation of the scaling origin is postulated. It seems that the proposed mechanism, namely the Polyakov scale invariant branching, is responsible for the scaling observed in the data. It is worth to emphasize that the same mechanism was proposed to explain the intermittent behaviour of a multiparticle final state.     

Conditional charge distributions at very high energies

It is shown that the conditional charge distributions in hadronic collisions approach a zero limiting value in the central region at asymptotic energies, provided the average total multiplicities are unbounded. A limiting charge sum rule, which shows how these distributions follow the initial charges, is established and discussed.