Fri·Sep 14, 2018Friday·September 14, 2018

1. 01*

   Loosely-bound objects produced in nuclear collisions at the LHC

   Peter Braun-Munzinger🇩🇪 · Benjamin Dönigus🇩🇪

   Loosely-bound objects such as light nuclei are copiously produced in proton-proton and nuclear collisions at the Large Hadron Collider (LHC), despite the fact that typical energy scales in such collisions exceed the binding energy of the objects by orders of magnitude. In this review we summarise the experimental observations, put them into context of previous studies at lower energies, and discuss the underlying physics. Most of the data discussed here were taken by the ALICE Collaboration during LHC Run1, which started in 2009 and ended in 2013. Specifically we focus on the production of (anti-)nuclei and (anti-)hypernuclei. Also included are searches for exotic objects like the H-dibaryon, a possible $uuddss$ hexaquark state, or also a possible bound state of a $\Lambda$ hyperon and a neutron. Furthermore, the study of hyperon-nucleon and hyperon-hyperon interactions through measurements of correlations are briefly discussed, especially in connection with the possible existence of loosely-bound states composed of these baryons. In addition, some results in the strange and charmed hadron sector are presented, to show the capabilities for future measurements on loosely-bound objects in this direction. Finally, perspectives are given for measurements in the currently ongoing Run2 period of the LHC and in the future LHC Run3.

   nucl-exNPA(2019)·153 citations
2. 02*

   Hydrodynamic fluctuations of entropy in one-dimensionally expanding system

   Tetsufumi Hirano🇯🇵 · Ryuichi Kurita🇯🇵 · Koichi Murase🇯🇵

   The fluctuation-dissipation relation tells that dissipation always accompanies with thermal fluctuations. Relativistic fluctuating hydrodynamics is used to study the effects of the thermal fluctuations in the hydrodynamic expansion of the quark-gluon plasma created in the high-energy nuclear collisions. We show that the thermal noise obeys the steady-state fluctuation theorem when (i) the time scales of the evolution of thermodynamic quantities are sufficiently longer than the relaxation time, and (ii) the thermal fluctuations of temperature are sufficiently small. The steady-state fluctuation theorem describes the distribution of the entropy which can be related to the multiplicity observed in high-energy nuclear collisions. As a consequence, we propose an upper bound to the multiplicity fluctuations which is useful to test the initial state models. We also numerically investigate breaking of the steady-state fluctuation theorem due to the non-vanishing relaxation time in real nuclear collisions.

   ↳ nucl-thcond-mat.stat-mechhep-phnucl-exNPA(2019)·20 citations
3. 03*

   New Results on Hard Probes in Heavy-Ion Collisions with ALICE

   Christian Klein-Bösing (for the ALICE Collaboration)🇩🇪

   Hard probes - final state particles related to an interaction with large momentum transfer or mass scale - play a distinguished role in the discovery and the study of the Quark-Gluon Plasma (QGP), a phase of deconfined quarks and gluons reached at high temperatures in heavy ion collisions. In heavy ion collisions, parton scatterings with a large momentum transfer ($1/Q\ll 1$ fm/$c$) occur prior to QGP formation and thus provide a source of coloured probe particles for the QGP created in the later stage of the reaction. The hard scattered partons and the subsequent parton shower interact strongly with the QGP and its constituents via elastic and radiative processes before hadronization into jets of observable particles. Thus, the comparison to jet and high-$p_T$ observables in pp (vacuum) potentially probes their modification due to medium effects. One of the key observables in the discovery and investigation of these jet modifications has been the nuclear modification factor $R_{AA}$, for which new results on charged particle production in different colliding systems are presented and the question of apparant suppression in peripheral Pb-Pb collisions is addressed. Fore more differential studies of the jet sub-structure and hence the parton shower evolution in the medium, recent results on jet grooming in heavy ion colisions are presented.

   ↳ hep-exhep-phnucl-exPoS(2018)·1 citation
4. 04*

   On the eikonal approach to nuclear diffraction dissociation

   Angela Bonaccorso🇮🇹 · David M. Brink🇬🇧

   The study of nuclear breakup of halo and weakly bound particles has been one of the key ingredients in the understanding of exotic nuclei during the last thirty years. One of the most used methods to analyse data, in particular absolute breakup cross sections, has been the eikonal approximation. Here we revise critically the formalisms used for calculating the diffraction dissociation part of nuclear breakup and show that there is a formula that can be applied to breakup on any target, while a most commonly used formula must be restricted to light targets as it contains also the effect of Coulomb breakup calculated to first order in the sudden approximation which is well known for not being accurate.

   ↳ nucl-thnucl-exEPJA(2018)·3 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.