B. Guiot

Evidence for Flow from Hydrodynamic Simulations of

One of the strongest signals of collective flow in heavy ion collisions is the fact that the transverse momentum dependence of the elliptical flow coefficient v2 (measuring the azimuthal asymmetry) depends in a very characteristic way on the mass of the observed hadrons. This has been predicted [1] and impressively confirmed experimentally later [2, 3]. Can we also “prove” the existence of flow in small systems like proton-lead collisions, where such a collective behavior has not been expected?

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Abstract There is little doubt that in heavy ion collisions at the LHC and RHIC, we observe a hydrodynamically expanding system, providing strong evidence for the formation of a Quark Gluon Plasma (QGP) in the early stage of such collisions. These observations are mainly based on results on azimuthal anisotropies, but also on particle spectra of identified particles, perfectly compatible with a hydrodynamic evolution. Surprisingly, in p–Pb collisions one observes a very similar behavior, and to some extent even in p–p. We take these experimental observations as a strong support for a unified approach to describe proton–proton (p–p), proton–nucleus (p–A), and nucleus–nucleus (A–A) collisions, with a plasma formation even in tiny systems as in p–p scatterings.

-Pb Collisions at 5.02 TeV from

Recent experimental studies of the multiplicity dependence of heavy quark (HQ) production in proton-proton collisions at 7 TeV showed a strong non-linear increase of the HQ multiplicity as a function of the charged particle multiplicity. We try to understand this behavior using the EPOS3 approach. Two issues play an important role: multiple scattering, in particular its impact on multiplicity fluctuations, and the collective hydrodynamic expansion. The results are very robust with respect to many details of the modeling, which means that these data contain valuable information about very basic features of the reaction mechanism in proton-proton collisions.

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We discuss latest developments in EPOS concerning parton saturation and its relation with energy conservation in the multiple scattering framework.

Mass Splitting

The reaction 48Ca+64Ni has been studied in the deep inelastic regime at approximately 6 MeV/A, by the CLARA‐PRISMA setup. Angular distributions of the reaction cross sections have been obtained for the most intense reaction products, taking into account the response function of the magnetic spectrometer. The response of PRISMA has been calculated making use of a MonteCarlo simulation of the transport of the ions in the spectrometer, starting from known events distributions. For the one‐nucleon transfer channels, the experimental data are in good agreement with predictions from a semiclassical multi‐nucleon transfer model.

A unified description of the reaction dynamics from pp to pA to AA collisions

The low-lying yrast states in the 51 Ca and 52 Sc nuclei were investigated to obtain information on the evolution of the P1/2 and f 5 / 2 neutron single-particle orbitals in neutron-rich nuclei near proton number Z = 20. Level structures associated with neutron excitations into these two orbitals and with proton excitations across the Z = 20 shell gap were identified. Shell-model calculations with the recently proposed GXPF1A interaction account reasonably well for the fp-shell states. The energy separation between the vp1/2 and vf5/2 orbitals in the Ca isotopes appears to be overestimated by the GXPF1A Hamiltonian.

Charm production in high multiplicity pp events

The aim of this paper is to understand particle production for different collision systems, namely proton-proton (pp), proton-nucleus (pA), and nucleus-nucleus (AA) scattering at the LHC. We will investigate in particular particle yields and ratios versus multiplicity, using the same multiplicity definition for the three different systems, in order to analyse in a compact way the evolution of particle production with the system size and the origin of a very different system size dependence of the different particles.

New developments in EPOS: Parton saturation

The aim of this paper is to understand resonance production (and more generally particle production) for different collision systems, namely proton-proton (pp), proton-nucleus (pA), and nucleus-nucleus (AA) scattering at the LHC. We will investigate in particular particle yields and ratios versus multiplicity, using the same multiplicity definition for the three different systems, in order to analyse in a compact way the evolution of particle production with the system size and the origin of a very different system size dependence of the different particles.

Population Of Neutron Rich Nuclei Around 48Ca With Deep Inelastic Collisions

The implementation of heavy quarks and prompt photons in EPOS is presented. One of the interests of event generators is their capability to reproduce exclusive observables. Our results for charms and prompt photons, in p-p collisions at √ s = 7 TeV, are compared with experiments and FONLL calculations [1].

Yrast structure of the neutron-rich N=31 isotones Ca51 and Sc52

There is little doubt that hydrodynamic flow has been observed in heavy ion collisions at the LHC and RHIC, mainly based on results on azimuthal anisotropies, but also on particle spectra of identified particles, perfectly compatible with hydrodynamic expansions. Surprisingly, in p-Pb collisions one observes a very similar behavior. So do we see flow even in p-Pb? We will try to answer this question.