arXiv subjects

P. -B. Gossiaux

Publications and source records attributed to P. -B. Gossiaux.

10 recordsLinked to original sources

arXiv2017

Heavy-flavor production and medium properties in high-energy nuclear collisions - What next?

Open and hidden heavy-flavor physics in high-energy nuclear collisions are entering a new and exciting stage towards reaching a clearer understanding of the new experimental results with the possibility to link them directly to the advancement in lattice Quantum Chromo-dynamics (QCD). Recent results from experiments and theoretical developments regarding open and hidden heavy-flavor dynamics have been debated at the Lorentz Workshop "Tomography of the quark-gluon plasma with heavy quarks}, which was held in October 2016 in Leiden, the Netherlands. In this contribution, we summarize identified common understandings and developed strategies for the upcoming five years, which aim at achieving a profound knowledge of the dynamical properties of the quark-gluon plasma.

nucl-th↗

arXiv2007

Energy Loss of a Heavy Quark Produced in a Finite Size Medium

We study the medium-induced energy loss $-ΔE_0(L_p)$ suffered by a heavy quark produced at initial time in a quark-gluon plasma, and escaping the plasma after travelling the distance $L_p$. The heavy quark is treated classically, and within the same framework $-ΔE_0(L_p)$ consistently includes: the loss from standard collisional processes, initial bremsstrahlung due to the sudden acceleration of the quark, and transition radiation. The radiative loss {\it induced by rescatterings} $-ΔE_{rad}(L_p)$ is not included in our study. For a ultrarelativistic heavy quark with momentum $p \gsim 10 {\rm GeV}$, and for a finite plasma with $L_p \lsim 5 {\rm fm}$, the loss $-ΔE_0(L_p)$ is strongly suppressed compared to the stationary collisional contribution $-ΔE_{coll}(L_p) \propto L_p$. Our results support that $-ΔE_{rad}$ is the dominant contribution to the heavy quark energy loss (at least for $L_p \lsim 5 {\rm fm}$), as indeed assumed in most of jet-quenching analyses. However they might raise some question concerning the RHIC data on large $p_{\perp}$ electron spectra.

hep-ph↗

arXiv2006

Retardation Effect for Collisional Energy Loss of Hard Partons Produced in a QGP

We study the collisional energy loss suffered by an energetic parton travelling the distance L in a high temperature quark-gluon plasma and initially produced in the medium. We find that the medium-induced collisional loss -Delta E(L) is strongly suppressed compared to previous estimates which assumed the collisional energy loss rate -dE/dx to be constant. The large L linear asymptotic behaviour of -Delta E(L) sets in only after a quite large retardation time. The suppression of -Delta E(L) is partly due to the fact that gluon bremsstrahlung arising from the initial acceleration of the energetic parton is reduced in the medium compared to vacuum. The latter radiation spectrum is sensitive to the plasmon modes of the quark-gluon plasma and has a rich angular structure.

hep-ph↗

arXiv2005

Non-universality of transverse Coulomb exchange at small x

Within an explicit scalar QED model we compare, at fixed x << 1, the leading-twist K_T-dependent `quark' distribution f_q(x, K_T) probed in deep inelastic scattering and Drell-Yan production, and show that the model is consistent with the universality of f_q(x, K_T). The extension of the model from the aligned-jet to the 'symmetric' kinematical regime reveals interesting properties of the physics of Coulomb rescatterings when comparing DIS and DY processes. At small x the transverse momentum induced by multiple scattering on a single centre is process dependent, as well as the transverse momentum broadening occurring in collisions on a finite size nuclear target.

hep-ph↗

arXiv2001

Heavy-quarkonium hadron cross section in QCD at leading twist

We compute the total cross section of a heavy quarkonium on a hadron target in leading twist QCD, including target mass corrections. Our method relies on the analytical continuation of the operator product expansion of the scattering amplitude, obtained long ago by Bhanot and Peskin. The cross section has a simple partonic form, which allows us to investigate the phenomenology of J/psi and Upsilon dissociation by both pions and protons.

hep-ph↗

arXiv2000

Energy loss and $x_2$ scaling breakdown in $J/ψ$ nuclear production

In addition to the final-state interactions, $J/ψ$ nuclear production might also be affected by parton energy loss. Using the upper limits from Drell-Yan data at SPS and Fermilab energies, we estimated energy loss contribution to $J/ψ$ production in p-A collisions. The results indicated that the effects might be sizeable at 200 GeV while remaining small at higher energies.

hep-ph↗

arXiv2000

Charmonium suppression in p-A collisions

The new high precision data on charmonium production in proton-nucleus collisions by the E866/NuSea collaboration at Fermilab allow - together with older data at lower energies - to fix a unique set of parameters for the standard production and absorption scenario of charmonium in a proton-nucleus reaction. In this scenario the c-cbar pair is formed in an octet state, emits a gluon and continues its radial expansion in a singlet state until it has reached the charmonium radius. In all three phases it can interact with the nuclear environment. We find that the lifetime of the octet state is much shorter than acceptable on physical grounds. This challenges the physical reality of the first phase in the standard scenario.

hep-ph↗

arXiv1998

Hadronic Transport Model with a Phase Transition

We specify a tractable transport model with thermodynamic properties close to those expected for the strongly interacting matter. In particular, at high temperatures, the matter undergoes a phase transition, such as to the quark-gluon plasma, with a drop in masses of elementary excitations and a rapid increase in the number of degrees of freedom. We show that a softening of the equation of state such as associated with the transition to quark-gluon plasma should be observable in the elliptic-flow excitation function from heavy-ion reactions.

nucl-th↗

arXiv1998

Magnetoconductance Autocorrelation Function for Few--Channel Chaotic Microstructures

Using the Landauer formula and a random matrix model, we investigate the autocorrelation function of the conductance versus magnetic field strength for ballistic electron transport through few-channel microstructures with the shape of a classically chaotic billiard coupled to ideal leads. This function depends on the total number M of channels and the parameter t which measures the difference in magnetic field strengths. Using the supersymmetry technique, we calculate for any value of M the leading terms of the asymptotic expansion for small t. We pay particular attention to the evaluation of the boundary terms. For small values of M, we supplement this analytical study by a numerical simulation. We compare our results with the squared Lorentzian suggested by semiclassical theory and valid for large M. For small M, we present evidence for non--analytic behavior of the autocorrelation function at t = 0.

cond-mat.dis-nn↗

arXiv1998

Disappearance of Elliptic Flow: A New Probe for the Nuclear Equation of State

Using a relativistic hadron transport model, we investigate the utility of the elliptic flow excitation function as a probe for the stiffness of nuclear matter and for the onset of a possible quark-gluon-plasma (QGP) phase-transition at AGS energies 1 < E_Beam < 11 AGeV. The excitation function shows a strong dependence on the nuclear equation of state, and exhibits characteristic signatures which could signal the onset of a phase transition to the QGP.

nucl-th↗