Analysis of Cumulant Moments in High Energy Hadron-Hadron Collisions by Truncated Multiplicity Distributions

Oscillatory behavior of cumulant moments obtained from the experimental data in $pp$ collisions and $\bar{p}p$ collisions are analyzed by the modified negative binomial distribution (MNBD) and the negative binomial distribution (NBD). Both distributions well describe the cumulant moments obtained from the data. This fact shows sharp contrast to the result in $e^+e^-$ collisions, which is described by the the MNBD much better than by the NBD.Comment: 7 pages, Latex type, 7 figure

Photon Production from a Quark--Gluon Plasma

In-medium interactions of a particle in a hot plasma are considered in the framework of thermal field theory. The formalism to calculate gauge invariant rates for photon and dilepton production from the medium is given. In the application to a QED plasma, astrophysical consequences are pointed out. The photon production rate from strongly interacting quarks in the quark--gluon plasma, which might be formed in ultrarelativistic heavy ion collisions, is calculated in the previously unaccessible regime of photon energies of the order of the plasma temperature. For temperatures below the chiral phase transition, an effective field theory incorporating dynamical chiral symmetry breaking is employed, and perturbative QCD at higher temperatures. A smooth transition between both regions is obtained. The relevance to the soft photon problem and to high energy heavy ion experiments is discussed.Comment: Paper in ReVTeX. Figures and complete paper available via anonymous ftp, ftp://tpri6c.gsi.de/pub/phenning/hq95ga

A Transient New Coherent Condition of Matter: The Signal for New Physics in Hadronic Diffractive Scattering

We demonstrate the existence of an anomalous structure in the data on the diffractive elastic scattering of hadrons at high energies and small momentum transfer. We analyze five sets of experimental data on $p(\overline{p})-p$ scattering from five different experiments with colliding beams, ranging from the first-- and second--generation experiments at $\sqrt{s} = 53$ GeV to the most recent experiments at 546 GeV and at 1800 GeV. All of the data sets exhibit a localized anomalous structure in momentum transfer. We represent the anomalous behavior by a phenomenological formula. This is based upon the idea that a transient coherent condition of matter occurs in some of the intermediate inelastic states which give rise, via unitarity, to diffractive elastic scattering. The Fourier--Bessel transform into momentum--transfer space of a spatial oscillatory behavior of matter in the impact--parameter plane results in a small piece of the diffractive amplitude which exhibits a localized anomalous behavior near a definite value of $-t$. In addition, we emphasize possible signals coming directly from such a new condition of matter that may be present in current experiments on inelastic processes.Comment: 25 pages, LaTeX (12 figures, not included). A complete postscript file (except figures 1 and 11, which are available upon request) is available via anonymous ftp at ttpux2.physik.uni-karlsruhe.de (129.13.102.139) as /ttp94-03 /ttp94-03.ps, Local preprint# TTP94-03 (March 1994

Mass Suppression in Octet Baryon Production

There is a striking suppression of the cross section for production of octet baryons in $e^+ e ^-$ annihilation, as the mass of the produced hadron increases. We present a simple parametrization for the fragmentation functions into octet baryons guided by two input models: the SU(3) flavor symmetry part is given by a quark-diquark model, and the baryon mass suppression part is inspired by the string model. We need only eight free parameters to describe the fragmentation functions for all octet baryons. These free parameters are determined by a fit to the experimental data of octet baryon production in $e^+ e ^-$ annihilation. Then we apply the obtained fragmentation functions to predict the cross section of the octet baryon production in charged lepton DIS and find consistency with the available experimental data. Furthermore, baryon production in $pp$ collisions is suggested to be an ideal domain to check the predicted mass suppression.Comment: 20 pages, 5 figure

Spin alignment of K∗(892)±K^*(892)^\pm mesons produced in neutron-carbon interactions

A new precise measurements of spin density matrix element $\rho_{00}$ of $K^*(892)^{\pm}$ mesons produced inclusively in neutron-carbon interactions at \~60 GeV have been carried out in the EXCHARM experiment at the Serpukhov accelerator. The values of $\rho_{00}$ obtained in the transversity frame are $0.424\pm0.011(stat)\pm0.018(sys)$ for $K^*(892)^+$ and $0.393\pm0.025(stat)\pm0.018(sys)$ for $K^*(892)^-$. Significant $P_T$ dependence of $\rho_{00}$ has been observed in $K^*(892)^+$ production.Comment: 8 pages, LaTeX, 3 eps figure

ρ(770)0\rho(770)^0, K∗(892)0^*(892)^0 and f0(980)_{0}(980) Production in Au-Au and pp Collisions at sNN\sqrt{s_{NN}} = 200 GeV

Preliminary results on $\rho(770)^0 \to \pi^{+}\pi^{-}$, K$^{*}(892)^{0} \to \pi$K and $f_{0}(980) \to \pi^{+}\pi^{-}$ production using the mixed-event technique are presented. The measurements are performed at mid-rapidity by the STAR detector in $\sqrt{s_{NN}}$= 200 GeV Au-Au and pp interactions at RHIC. The results are compared to different measurements at various energies.Comment: 4 pages, 6 figures. Talk presented at Quark Matter 2002, Nantes, France, July 18-24, 2002. To appear in the proceedings (Nucl. Phys. A

Leading particle effect, inelasticity and the connection between average multiplicities in {\bf e+e−e^+e^-} and {\bf pppp} processes

The Regge-Mueller formalism is used to describe the inclusive spectrum of the proton in $p p$ collisions. From such a description the energy dependences of both average inelasticity and leading proton multiplicity are calculated. These quantities are then used to establish the connection between the average charged particle multiplicities measured in {\bf $e^+e^-$} and {\bf $pp/{\bar p}p$} processes. The description obtained for the leading proton cross section implies that Feynman scaling is strongly violated only at the extreme values of $x_F$, that is at the central region ($x_F \approx 0$) and at the diffraction region ($x_F \approx 1$), while it is approximately observed in the intermediate region of the spectrum.Comment: 20 pages, 10 figures, to be published in Physical Review

Charged rho meson production in neutrino-induced reactions at E_nu = 10 GeV

The neutrinoproduction of charged $\rho$ mesons on nuclei and nucleons is investigated for the first time at moderate energies ($\approx$ 10 GeV), using the date obtained with SKAT bubble chamber. No strong nuclear effects are observed in $\rho^+$ and $\rho^-$ production. The fractions of charged and neutral pions originating from $\rho$ decays are obtained and compared with higher energy data. From analysis of the obtained and available data on $\rho^+$ and $K^{*+}$(892) neutrinoproduction, the strangeness suppression factor in the quark string fragmentation is extracted: $\lambda_s = 0.18\pm0.03$. Estimations are obtained for cross sections of quasiexclusive single $\rho^+$ and coherent $\rho^+$ neutrinoproduction on nuclei. The estimated coherent cross section $\sigma_{\rho^+}^{coh}$ = (0.29$\pm0.16)\cdot 10^{-38}$ cm$^2$ is compatible with theoretical predictions.Comment: 7 pages, 6 figure

Theoretical Aspects of Particle Production

These lectures describe some of the latest data on particle production in high-energy collisions and compare them with theoretical calculations and models based on QCD. The main topics covered are: fragmentation functions and factorization, small-x fragmentation, hadronization models, differences between quark and gluon fragmentation, current and target fragmentation in deep inelastic scattering, and heavy quark fragmentation.Comment: 26 pages, 27 figures. Lectures at International Summer School on Particle Production Spanning MeV and TeV Energies, Nijmegen, The Netherlands, August 199