NLO QCD procedure of the semi-inclusive deep inelastic scattering data analysis with respect to the light quark polarized sea

The semi-inclusive deep inelastic scattering (SIDIS) process is considered. A theoretical procedure is proposed allowing the direct extraction from the SIDIS data of the first moments of the polarized valence distributions and of the first moment difference of the light sea quark polarized distributions in the next to leading QCD order. The validity of the procedure is confirmed by the respective simulations

The non-Abelian feature of parton energy loss in energy dependence of jet quenching in high-energy heavy-ion collisions

One of the non-Abelian features of parton energy loss is the ratio $\Delta E_g/\Delta E_q=9/4$ between gluon and quark jets. Since jet production rate is dominated by quark jets at high $x_T=2p_T/\sqrt{s}$ and by gluon jets at low $x_T$, high $p_T$ hadron suppression in high-energy heavy-ion collisions should reflect such a non-Abelian feature. Within a leading order perturbative QCD parton model that incorporates transverse expansion and Woods-Saxon nuclear distribution, the energy dependence of large $p_T\sim 5-20$ GeV/$c$ hadron suppression is found to be sensitive to the non-Abelian feasture of parton energy loss and could be tested by data from low energy runs at RHIC or data from LHC.Comment: RevTex 4, 7 pages, 3 figure

Energy Dependence of Jet Quenching and Life-time of the Dense Matter in High-energy Heavy-ion Collisions

Suppression of high $p_T$ hadron spectra in high-energy heavy-ion collisions at different energies is studied within a pQCD parton model incorporating medium induced parton energy loss. The $p_T$ dependence of the nuclear modification factor $R_{AA}(p_T)$ is found to depend on both the energy dependence of the parton energy loss and the power-law behavior of the initial jet spectra. The high $p_T$ hadron suppression at $\sqrt{s}=62.4$ GeV and its centrality dependence are studied in detail. The overall values of the modification factor are found to provide strong constraints on the lifetime of the dense matter.Comment: 6 pages in RevTex with 3 postscript figure

Crystal structure of decachloro-bicyclo[5.5.1]heptaoxatridecasilane, Si6O7Cl10

CI10O7Si6, monoclinic, P121/ml (No. 11), a = 6.094(1) Å, b = 20.676(4) Å, c = 8.295(2) Å, ß = 99.47(3)°, V= 1030.9 Å3 , Ζ = 2, Rgt(F) = 0.039, wRobs(F2 ) = 0.114, Τ = 203 Κ

Hadron production from quark coalescence and jet fragmentation in intermediate energy collisions at RHIC

Transverse momentum spectra of pions, protons and antiprotons in Au+Au collisions at intermediate RHIC energy of $\sqrt{s_{NN}}=62$ GeV are studied in a model that includes both quark coalescence from the dense partonic matter and fragmentation of the quenched perturbative minijet partons. The resulting baryon to meson ratio at intermediate transverse momenta is predicted to be larger than that seen in experiments at higher center of mass energies.Comment: 6 pages, 2 figures. Figures replaced to differentially address the high-pT behavior of baryon versus antibaryon to meson ratio

Prompt Photon and Inclusive π0\pi^0 Production at RHIC and LHC

We present results for prompt photon and inclusive $\pi^0$ production in p-p and A-A collisions at RHIC and LHC energies. We include the full next-to-leading order radiative corrections and nuclear effects, such as nuclear shadowing and parton energy loss. We find the next-to-leading order corrections to be large and $p_T$ dependent. We show how measurements of $\pi^0$ production at RHIC and LHC, at large $p_T$, can provide valuable information about the nature of parton energy loss. We calculate the ratio of prompt photons to neutral pions and show that at RHIC energies this ratio increases with $p_T$ approaching one at $p_T \sim 10$ GeV, due to the large suppression of $\pi^0$ production. We show that at the LHC, this ratio has steep $p_T$ dependence and approaches 10% effect at $p_T \sim 20$ GeV.Comment: Talk presented by I. Sarcevic, to appear in the Proceedings of Quark Matter 2002; 4 pages including 4 color figure

Compatibility of various approaches to heavy-quark fragmentation

We find that the definition of the heavy-quark fragmentation function given by Jaffe and Randall differs by a factor of the longitudinal-momentum fraction z from the standard Collins-Soper definition. Once this factor is taken into account, the explicit calculation of Braaten et al. is found to be in agreement with the general analysis of Jaffe and Randall. We also examine the model of Peterson et al. for heavy-quark fragmentation and find that the quoted values of the width and of the value of $z$ at the maximum are in error. The corrected values are in agreement with the analysis of Jaffe and Randall.Comment: 4 pages late

Neutral-Kaon Production in e^+e^-, ep, and p\bar p Collisions at Next-to-Leading Order

We present new sets of fragmentation functions for neutral kaons, both at leading and next-to-leading order. They are fitted to data on inclusive K^0 production in e^+e^- annihilation taken by MARK II at PEP (\sqrt s = 29 GeV) and by ALEPH at LEP. Our fragmentation functions lead to a good description of other e^+e^- data on inclusive K^0 production at various energies. They also nicely agree with the K_S^0 transverse-momentum spectra measured by H1 at the DESY ep collider HERA, by UA5 at the CERN Sp\bar pS Collider, and by CDF at the Fermilab Tevatron.Comment: 15 pages, latex, 7 figures (uuencoded compressed tar postscript