5,728 research outputs found

    Trends in multiparticle production and some "predictions" for pp and PbPb collisions at LHC

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    Based on trends seen at lower energies we "predict" the multiplicities and pseudorapidity distributions of particle density and elliptic flow that will be seen in PbPb and pp collisions at the LHC. We argue that, if these predictions turn out to be correct, either these quantities are insensitive to the state of matter created in high energy heavy ion collisions or the observed simplicity and universality of the data must be telling us something profound about the mechanism of particle production, which to this date is not well understood.Comment: Invited Talk at SQM2007 Conferenc

    Strangeness enhancement at LHC

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    We study production of strangeness in the hot QGP fireball in conditions achieved at LHC, and use these results to obtain soft (strange) hadron multiplicities. We compare the chemical equilibrium and non-equilibrium conditions and identify characteristic experimental observables.Comment: Presented at SQM07, to appear in JPG special issue. One table with prediction

    3D Jet Tomography of Twisted Strongly Coupled Quark Gluon Plasmas

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    The triangular enhancement of the rapidity distribution of hadrons produced in p+A reactions relative to p+p is a leading order in A^{1/3}/log(s) violation of longitudinal boost invariance at high energies. In A+A reactions this leads to a trapezoidal enhancement of the local rapidity density of produced gluons. The local rapidity gradient is proportional to the local participant number asymmetry, and leads to an effective rotation in the reaction plane. We propose that three dimensional jet tomography, correlating the long range rapidity and azimuthal dependences of the nuclear modification factor, R_{AA}(\eta,\phi,p_\perp; b>0), can be used to look for this intrinsic longitudinal boost violating structure of A+AA+A collisions to image the produced twisted strongly coupled quark gluon plasma (sQGP). In addition to dipole and elliptic azimuthal moments of R_{AA}, a significant high p_\perp octupole moment is predicted away from midrapidity. The azimuthal angles of maximal opacity and hence minima of R_{AA} are rotated away from the normal to the reaction plane by an `Octupole Twist' angle, \theta_3(\eta), at forward rapidities.Comment: 10 Pages, 16 Figures, RevTex, Replaced with Peer reviewed verion for PR

    Polarization probes of vorticity in heavy ion collisions

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    We discuss the information that can be deduced from a measurement of particle (hyperon or vector meson) polarization in ultrarelativistic nuclear collisions. We describe the sensitivity of polarization to initial conditions, hydrodynamic evolution and mean free path, and find that the polarization observable is sensitive to all details and stages of the system's evolution. We suggest that an experimental investigation covering production plane and reaction plane polarizations, as well as the polarization of jet-associated particles in the plane defined by the jet and particle direction, can help in disentangling the factors contributing to this observable. Scans of polarization in energy and rapidity might also point to a change in the system's properties.Comment: In press, Phys.Rev.C. One new figure, text streamlined and edited, physics conclusions and reasoning not change

    Bulk Viscosity driven clusterization of quark-gluon plasma and early freeze-out in relativistic heavy-ion collisions

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    We introduce a new scenario for heavy ion collisions that could solve the lingering problems associated with the so-called HBT puzzle. We postulate that the system starts expansion as the perfect quark-gluon fluid but close to freeze-out it splits into clusters, due to a sharp rise of bulk viscosity in the vicinity of the hadronization transition. We then argue that the characteristic cluster size is determined by the viscosity coefficient and the expansion rate. Typically it is much smaller and independent of the total system volume. These clusters maintain the pre-existing outward-going flow, as a spray of droplets, but develop no flow of their own, and hadronize by evaporation. We provide an ansatz for converting the hydrodynamic output into clusters.Comment: Accepted for publication, Phys. Rev. C. Arguments considerably expanded, refined and reworde

    Wounded quarks and diquarks in high energy collisions

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    Particle production in Au-Au, Cu-Cu, d-Au and p-p collisions at 200 GeV c.m. energy are analyzed in the wounded quark-diquark model. Existing data are well reproduced. Emission functions of wounded and unwounded constituents are determined. Implications for the collective evolution of the system are discussed.Comment: version to be published in Phys. Rev. C, minor changes, discussion extende

    Classical Hadrodynamics: A New Approach to Ultrarelativistic Heavy-Ion Collisions

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    We discuss a new approach to ultrarelativistic heavy-ion collisions based on classical hadrodynamics for extended nucleons, corresponding to nucleons of finite size interacting with massive meson fields. This new theory provides a natural covariant microscopic approach that includes automatically spacetime nonlocality and retardation, nonequilibrium phenomena, interactions among all nucleons and particle production. In the current version of our theory, we consider NN extended unexcited nucleons interacting with massive neutral scalar (σ\sigma) and neutral vector (ω\omega) meson fields. The resulting classical relativistic many-body equations of motion are solved numerically without further approximation for soft nucleon-nucleon collisions at plabp_{\rm lab} = 14.6, 30, 60, 100 and 200 GeV/cc to yield the transverse momentum imparted to the nucleons. For the future development of the theory, the isovector pseudoscalar (π+\pi^+, π\pi^-, π0\pi^0), isovector scalar (δ+\delta^+, δ\delta^-, δ0\delta^0), isovector vector (ρ+\rho^+, ρ\rho^-, ρ0\rho^0) and neutral pseudoscalar (η\eta) meson fields that are known to be important from nucleon-nucleon scattering experiments should be incorporated. In addition, the effects of quantum uncertainty on the equations of motion should be included by use of techniques analogous to those used by Moniz and Sharp for nonrelativistic quantum electrodynamics.Comment: 6 pages, LA-UR-94-217

    Exteneded Longitudinal Scaling and the Thermal Model

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    The property of extended longitudinal scaling of rapidity distributions was noticed recently over a broad range of beam energies. It is shown here that this property is consistent with predictions of the statistical thermal model up to the highest RHIC beam energies, however, we expect that at LHC energies the rapidity distribution of produced particles will violate extended longitudinal scaling.Comment: 3 pages, 4 figure

    Reply to Comment of Gazdzicki and Heinz on Strangeness Enhancement in p+Ap+A and S+AS+A

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    The Comment of Gazdzicki and Heinz is flawed because their assumed baryon stopping power in pApA is inconsistent with data and because they ignored half the analysis based on the VENUS model. The Comment continues the misleading presentation of strangeness enhancement by focusing on ratios of integrated yields. Those ratios discard essential experimental information on the rapidity dependence of produced Λ\Lambda and obscure discrepancies between different data sets. Our conclusion remains that the NA35 minimum bias data on p+SΛ+Xp+S\rightarrow\Lambda +X indicate an anomalous enhancement of central rapidity strangeness in few nucleon reactions that points to non-equilibrium dynamics as responsible for strangeness enhancement in nuclear reactions.Comment: revtex file, 6 pages, submitted to Phys. Rev.

    Glueball Production in Peripheral Heavy-Ion Collisions

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    The method of equivalent quanta is applied both to photon-photon and, by analogy, to double pomeron exchange in heavy-ion collisions. This Weizs\"acker-Williams approach is used to calculate production cross sections for the glueball candidate fJ(1710)f_J(1710) meson via photon-photon and pomeron-pomeron fusion in peripheral heavy-ion collisions at both RHIC and LHC energies. The impact-parameter dependence for total and elastic cross sections are presented, and are compared to results for proton-proton collisions.Comment: 15 pages, 6 figure
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