Thu·Oct 6, 2011Thursday·October 6, 2011

1. 01*

   Hydrodynamic Flow in PbPb Collisions Observed via Azimuthal Angle Correlations of Charged Hadrons

   Eric Appelt (for the CMS Collaboration)🇺🇸

   Azimuthal angle correlations of charged hadrons were measured in ${\sqrt{s}}_{NN}$ = 2.76 TeV PbPb collisions by the CMS experiment. The distributions exhibit anisotropies that are correlated with the event-by-event orientation of the reaction plane. Several methods were employed to extract the strength of the signal: the event-plane, cumulant and Lee-Yang Zeros methods. These methods have different sensitivity to correlations that are not caused by the collective motion in the system (non-flow correlations due to jets, resonance decays, and quantum correlations). The second Fourier coefficient of the charged hadron azimuthal distributions was measured as a function of transverse momentum, pseudorapidity and centrality in a broad kinematic range: $0.3<p_T<12.0$ GeV/c, $|\eta |<2.4$, as a function of collision centrality. In addition, the third through sixth Fourier components were measured at midrapidity using selected methods.

   nucl-exAIP Conf.Proc.(2012)·3 citations
2. 02*

   J/psi production in pp and Pb-Pb with ALICE at the LHC

   Pereira Da Costa Hugo (for the ALICE collaboration)🇫🇷

   ALICE is the Large Hadron Collider (LHC) experiment dedicated to the study of heavy ion collisions. The main purpose of ALICE is to investigate the properties of a new state of deconfined nuclear matter, the Quark Gluon Plasma (QGP). Quarkonium measurements will play a crucial role in this investigation due to the interplay of several competing mechanisms that are predicted to modify its production in the presence of a QGP. During the 2010 and 2011 LHC campaigns, ALICE took pp data at sqrt(s)=2.76 and 7 TeV and Pb-Pb data at sqrt(s_nn)=2.76 TeV. We present the latest results of J/psi production under these conditions, measured by the ALICE experiment at both mid- and forward-rapidities.

   nucl-exAIP Conf.Proc.(2012)·4 citations
3. 03*

   Are present reaction theories for studying rare isotopes good enough?

   F. M. Nunes🇺🇸 · P. Capel🇺🇸 · R.J. Charity🇺🇸 · A. Deltuva🇵🇹 · W.Dickhoff🇺🇸 · H. Esbensen🇺🇸 · R.C. Johnson🇬🇧 · N.B. Nguyen🇺🇸 · N.J. Upadhyay🇺🇸 · S.J. Waldecker🇺🇸

   Rare isotopes are most often studied through nuclear reactions. Nuclear reactions can be used to obtain detailed structure information but also in connection to astrophysics to determine specific capture rates. In order to extract the desired information it is crucial to have a reliable framework that describes the reaction process accurately. A few recent developments for transfer and breakup reactions will be presented. These include recent studies on the reliability of existing theories as well as effort to reduce the ambiguities in the predicted observables.

   ↳ nucl-thnucl-ex0 citations
4. 04*

   Boosted saturation bound in colliding nuclei

   B. Z. Kopeliovich🇨🇱

   Interaction with a nucleus in pA collisions enhances the higher Fock components in the projectile proton. Effectively, this corresponds to an increase of the hard scale of the process by the saturation momentum Q^2 -> Q^2+Q_{sA}^2, which leads to an increased gluon distribution function at small x (but suppressed at x -> 1) compared to that in pp collisions. In the case of AA collisions the gluon distributions of bound nucleons in both nuclei turn out to be enhanced, i.e. to be boosted to higher saturation scales compared to pA collisions. A set of bootstrap equations relating the saturation scales in the colliding nuclei is derived and solved. The boosting effect has a moderate magnitude at the energies of RHIC, but becomes significant at LHC.

   ↳ hep-phnucl-exnucl-thProg.Theor.Phys.Suppl.(2012)·0 citations
5. 05*

   Low-energy dipole strength and the critical case of 48Ca

   P. Papakonstantinou🇩🇪 · H. Hergert🇺🇸 · V.Yu. Ponomarev🇩🇪 · R. Roth🇩🇪

   Recent theoretical work has not led to a consensus regarding the nature of the low-energy E1 strength in the 40,44,48Ca isotopes, for which high-resolution (gamma,gamma') data exist. Here we revisit this problem using the first-order quasi-particle random-phase approximation (QRPA) and different interactions. First we examine all even Ca isotopes with N=14-40. All isotopes are predicted to undergo dipole transitions at low energy, of large and comparable isoscalar strength but of varying E1 strength. Provided a moderate and uniform energetic shift is introduced to the results, QRPA with the Gogny D1S interaction is able to account for the (gamma,gamma') data, because, up to N=28, it yields a rather pure isoscalar oscillation. A neutron-skin oscillation is anticipated for N larger or equal to 30. This contradicts existing predictions that 44,48Ca develop a neutron-skin mode. Which theoretical result is correct cannot be resolved conclusively using the available data. We propose that alpha-scattering, possibly followed by an electroexcitation experiment, could resolve the situation and thereby help to improve the different models aspiring to describe reliably the low-energy dipole strength of nuclei.

   ↳ nucl-thnucl-exPLB(2012)·22 citations
6. 06*

   Nuclear physics with a medium-energy Electron-Ion Collider

   A. Accardi🇺🇸 · V. Guzey🇺🇸 · A. Prokudin🇺🇸 · C. Weiss🇺🇸

   A polarized ep/eA collider (Electron-Ion Collider, or EIC) with variable center-of-mass energy sqrt(s) ~ 20-70 GeV and a luminosity ~ 10^{34} cm^{-2} s^{-1} would be uniquely suited to address several outstanding questions of Quantum Chromodynamics (QCD) and the microscopic structure of hadrons and nuclei: (i) the three-dimensional structure of the nucleon in QCD (sea quark and gluon spatial distributions, orbital motion, polarization, correlations); (ii) the fundamental color fields in nuclei (nuclear parton densities, shadowing, coherence effects, color transparency); (iii) the conversion of color charge to hadrons (fragmentation, parton propagation through matter, in-medium jets). We briefly review the conceptual aspects of these questions and the measurements that would address them, emphasizing the qualitatively new information that could be obtained with the collider. Such a medium-energy EIC could be realized at Jefferson Lab after the 12 GeV Upgrade (MEIC), or at Brookhaven National Lab as the low-energy stage of eRHIC.

   ↳ nucl-thhep-phnucl-exEPJA(2012)·38 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.