551 research outputs found

    Hadron yields in Au+Au/Pb+Pb at RHIC and LHC from thermalized minijets

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    We calculate the yields of a variety of hadrons for RHIC and LHC energies assuming thermodynamical equilibration of the produced minijets, and using as input results from pQCD for the energy densities at midrapidity. In the calculation of the production of partons and of transverse energy one has to account for nuclear shadowing. By using two parametrizations for the gluon shadowing one derives energy densities differing strongly in magnitude. In this publication we link those perturbatively calculated energy densities of partons via entropy conservation in an ideal fluid to the hadron multiplicities at chemical freeze-out.Comment: 11 pages, 2 .eps figure

    Non-equilibrium initial conditions from pQCD for RHIC and LHC

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    We calculate the initial non-equilibrium conditions from perturbative QCD (pQCD) within Glauber multiple scattering theory for s=200\sqrt s =200 AGeV and s=5.5\sqrt s =5.5 ATeV. At the soon available collider energies one will particularly test the small xx region of the parton distributions entering the cross sections. Therefore shadowing effects, previously more or less unimportant, will lead to new effects on variables such as particle multiplicities dN/dydN/dy, transverse energy production dEˉT/dyd\bar{E}_T/dy, and the initial temperature TiT_i. In this paper we will have a closer look on the effects of shadowing by employing different parametrizations for the shadowing effect for valence quarks, sea quarks and gluons. Since the cross sections at midrapidity are dominated by processes involving gluons the amount of their depletion is particularly important. We will therefore have a closer look on the results for dN/dydN/dy, dEˉT/dyd\bar{E}_T/dy, and TiT_i by using two different gluon shadowing ratios, differing strongly in size. As a matter of fact, the calculated quantities differ significantly.Comment: typo in ref's removed, ack's added, no change in result

    Charmonium suppression from purely geometrical effects

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    The extend to which geometrical effects contribute to the production and suppression of the J/ψJ/\psi and qqˉq\bar{q} minijet pairs in general is investigated for high energy heavy ion collisions at SPS, RHIC and LHC energies. For the energy range under investigation, the geometrical effects referred to are shadowing and anti-shadowing, respectively. Due to those effects, the parton distributions in nuclei deviate from the naive extrapolation from the free nucleon result; fAAfNf_{A}\neq A f_{N}. The strength of the shadowing/anti-shadowing effect increases with the mass number. The consequences of gluonic shadowing effects for the xFx_F distribution of J/ψJ/\psi's at s=20\sqrt s =20 GeV, s=200\sqrt s =200 GeV and s=6\sqrt s =6 TeV are calculated for some relevant combinations of nuclei, as well as the pTp_T distribution of minijets at midrapidity for Nf=4N_f=4 in the final state.Comment: corrected some typos, improved shadowing ratio

    Prompt photons at RHIC

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    We calculate the inclusive cross section for prompt photon production in heavy-ion collisions at RHIC energies (s=130\sqrt{s}=130 GeV and s=200\sqrt{s}=200 GeV) in the central rapidity region including next-to-leading order, O(αemαs2)O(\alpha_{em}\alpha_s^2), radiative corrections, initial state nuclear shadowing and parton energy loss effects. We show that there is a significant suppression of the nuclear cross section, up to 30\sim 30% at s=200\sqrt{s}=200 GeV, due to shadowing and medium induced parton energy loss effects. We find that the next-to-leading order contributions are large and have a strong ptp_t dependence.Comment: 9 pages, 5 figures, expanded discussion of the K facto

    Two-hadron interference fragmentation functions. Part I: general framework

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    We investigate the properties of interference fragmentation functions measurable from the distribution of two hadrons produced in the same jet in the current fragmentation region of a hard process. We discuss the azimuthal angular dependences in the leading order cross section of two-hadron inclusive lepton-nucleon scattering as an example how these interference fragmentation functions can be addressed separately.Comment: RevTeX, 7 figures, first part of a work split in two, second part forthcoming in few day

    Hard Parton Rescatterings and Minijets in Nuclear Collisions at LHC

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    The average number of minijets and the corresponding transverse energy produced in heavy ion collisions are evaluated by including explicitly semi-hard parton rescatterings in the dynamics of the interaction. At the LHC semi-hard rescatterings have a sizable effect on global characteristics of the typical inelastic event. An interesting feature is that the dependence on the cutoff which separates soft and hard parton interactions becomes less critical after taking rescatterings into account.Comment: 14 pages, 3 figures. Enlarged discussion in sect.1 and 4; 1 figure added. To be published in Phys.Rev.

    Identifying and accommodating education/research barriers of rural nursing staff in the Mississippi River Delta

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    Session presented on Sunday, September 18, 2016: The purpose of this study was to identify by survey, what education and research barriers exist for operating room and post anesthesia care nursing staff in the rural hospitals of the Mississippi River Delta

    Bounds on transverse momentum dependent distribution and fragmentation functions

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    We give bounds on the distribution and fragmentation functions that appear at leading order in deep inelastic 1-particle inclusive leptoproduction or in Drell-Yan processes. These bounds simply follow from positivity of the defining matrix elements and are an important guidance in estimating the magnitude of the azimuthal and spin asymmetries in these processes.Comment: 5 pages, Revtex, 3 Postscript figures, version with minor changes, to be published in Physical Review Letter

    Covenants as Quasi Contracts

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    It is the scope of this article to discuss briefly certain forms of covenant with a view to determining whether in their nature they are contractual or quasi contractual. Quasi contract may be defined as an obligation whereby one person becomes bound to another, without regard to his consent, by a legal tie similar to that arising from contract. It may exist either by statute or by common law, and, if by the latter, it may be enforced either on principle or by reason of custom. As to the cause of the obligation, it may be imposed upon a man because he occupies a peculiar relation, public or private, or because of his acts or omissions. And since agreement or the semblance of one is not an element of the obligation, it may arise where the person bound was unconscious or undesirous of assuming any liability whatever,-or where he was desirous of assuming a different liability from that imposed
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