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Nuclear Theory·nucl-th

Wednesday·October 11, 2017

8 papers—4 primary·4 cross-listed

All8Primary4Cross-lists4
  1. 01

    Evolution of the Mean Jet Shape and Dijet Asymmetry Distribution of an Ensemble of Holographic Jets in Strongly Coupled Plasma

    Jasmine Brewer🇺🇸 · Krishna Rajagopal🇺🇸 · Andrey Sadofyev🇺🇸 · Wilke van der Schee🇺🇸

    Some of the most important probes of the quark-gluon plasma (QGP) produced in heavy ion collisions come from the analysis of how the shape and energy of jets are modified by passage through QGP. We model an ensemble of back-to-back dijets to gain a qualitative understanding of how the shapes of the individual jets and the asymmetry in the energy of the pairs of jets are modified by passage through an expanding droplet of strongly coupled plasma, as modeled in a holographic gauge theory. We do so by constructing an ensemble of strings in the gravitational description of the gauge theory. We model QCD jets in vacuum using strings whose endpoints move "downward" into the gravitational bulk spacetime with some fixed small angle that represents the opening angle (ratio of jet mass to jet energy) that the QCD jet would have in vacuum. Such strings must be moving through the gravitational bulk at (close to) the speed of light; they must be (close to) null. This condition does not specify the energy distribution along the string, meaning that it does not specify the shape of the jet being modeled. We study the dynamics of strings that are initially not null and show that strings with a wide range of initial conditions rapidly accelerate and become null and, as they do, develop a similar distribution of their energy density. We use this distribution of the energy density along the string, choose an ensemble of strings whose opening angles and energies are distributed as in perturbative QCD, and show that we can then fix one model parameter such that the mean jet shape in our ensemble matches that measured in p-p collisions reasonably well. We send our strings through the plasma, choosing the second model parameter to get a reasonable suppression in the number of jets, and study how the mean jet shape and the dijet asymmetry are modified, comparing both to data from LHC heavy ion collisions.

    nucl-thhep-phhep-thJHEP(2018)·50 citations
  2. 02

    Causal Electric Charge Diffusion and Balance Functions in Relativistic Heavy Ion Collisions

    Joseph I. Kapusta🇺🇸 · Christopher Plumberg🇺🇸

    We study the propogation and diffusion of electric charge fluctuations in high energy heavy ion collisions using the Cattaneo form for the dissipative part of the electric current. As opposed to the ordinary diffusion equation this form limits the speed at which charge can propagate. Including the noise term in the current, which arises uniquely from the fluctuation-dissipation theorem, we calculate the balance functions for charged hadrons in a simple 1+1 dimensional Bjorken hydrodynamical model. Limiting the speed of propagation of charge fluctuations increases the height and reduces the width of these balance functions when plotted versus rapidity. We also estimate the numerical value of the associated diffusion time constant from AdS/CFT theory.

    nucl-thnucl-exPRC(2018)·35 citations
  3. 03

    Nuclear clustering and the electron screening puzzle

    C.A. Bertulani · C. Spitaleri

    Electron screening changes appreciably the magnitude of astrophysical nuclear reactions within stars. This effect is also observed in laboratory experiments on Earth, where atomic electrons are present in the nuclear targets. Theoretical models were developed over the past 30 years and experimental measurements have been carried out to study electron screening in thermonuclear reactions. None of the theoretical models were able to explain the high values of the experimentally determined screening potentials. We explore the possibility that the "electron screening puzzle" is due to nuclear clusterization and polarization effects in the fusion reactions. We will discuss the supporting arguments for this scenario.

    nucl-thnucl-exEPJ Web Conf.(2017)·3 citations
  4. 04

    Simultaneous Production of Lepton Pairs at Ultra-peripheral Relativistic Heavy Ion Collisions

    Erkan Kurban🇹🇷 · Mehmet Cem Guclu🇹🇷

    We calculate the total cross sections and probabilities of electromagnetic productions of electron, muon and tauon pair productions simultaneously. At the Large Hadron Collider (LHC), the available electromagnetic energy is sufficient to produce all kind of leptons coherently. The masses of muon and tauon are large, so their Compton wavelengths are small enough to interact with the colliding nuclei. Therefore, the realistic nuclear form factors are included in the calculations of electromagnetic pair productions. The cross section calculations show that, at the LHC energies, the probabilities of simultaneous productions of all kind of leptons are increased significantly compare to the RHIC energies. Experimentally, observing this simultaneous production can give us important informations about the strong QED.

    nucl-thhep-phPRC(2017)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE