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Cyrille Marquet

Publications and source records attributed to Cyrille Marquet.

At least 55 records · Page 3Linked to original sources
arXiv2013

Universality of multi-particle production in QCD at high energies

By studying the color structure of multi-particle production processes in p+A-type (dilute-dense) collisions, we find that higher-point functions beyond typical dipoles and quadrupoles, e.g., sextupoles, octupoles, etc., naturally appear in the cross sections, but are explicitly suppressed in the large-N_c limit. We evaluate the sextupole in the McLerran-Venugopalan model and find that, in general, its analytical form cannot be written as combination of dipoles and quadrupoles. Within the Color Glass Condensate framework, we present a proof that in the large-N_c limit, all multi-particle production processes in the collision of a dilute system off a dense can, up to all orders in α_s, be described in terms of only dipoles and quadrupoles.

hep-ph↗
arXiv2013

The initial state of heavy-ion collisions

We present a brief review of recent theoretical developments and related phenomenological approaches for understanding the initial state of heavy-ion collisions, with emphasis on the Color Glass Condensate formalism.

hep-ph↗
arXiv2012

Open questions in QCD at high parton density

I present the state of our understanding of the QCD dynamics at play in the parton saturation regime of nuclear wave functions. I explain what are the biggest open questions in the field, their intrinsic interest, but also why is it important to answer them from the quark-gluon-plasma physicists' perspective. Focusing on those aspects that proton-nucleus collisions cannot investigate to a satisfactory degree, I show that future high-energy electron-ion colliders have the potential to address these questions, providing thorough answers in most cases, and exploratory measurements otherwise.

hep-ph↗
arXiv2011

Universality of Unintegrated Gluon Distributions at small x

We systematically study dijet production in various processes in the small-$x$ limit and establish an effective $k_t$-factorization for hard processes in a system with dilute probes scattering on a dense target. We find that the well-known Weizsäcker-Williams gluon distribution can be directly probed in the quark-antiquark jet correlation in deep inelastic scattering and the dipole gluon distribution can be directly measured in the direct photon-jet correlation in $pA$ collisions. In the large-$N_c$ limit, the unintegrated gluon distributions involved in other different dijet channels in pA collisions are shown to be related to two widely proposed ones: the Weizsäcker-Williams gluon distribution and the dipole gluon distribution.

hep-ph↗
arXiv2011

Azimuthal correlations of forward di-hadrons in d+Au collisions suppressed by saturation

RHIC experiments have recently measured the azimuthal correlation function of forward di-hadrons. The data show a disappearance of the away-side peak in central d+Au collisions, compared to p+p collisions, as was predicted by saturation physics. Indeed, we argue that this effect, absent at mid-rapidity, is a consequence of the small-x evolution into the saturation regime of the Gold nucleus wave function. We show that the data are well described in the Color Glass Condensate framework.

hep-ph↗
arXiv2011

Azimuthal angle and rapidity dependence of di-hadron correlations in QCD

I discuss novel QCD phenomena recently observed in p+p, p+A and A+A collisions, that result from the non-linear dynamics of small-x gluons. I focus on di-hadron correlation measurements, as opposed to single-hadron observables often too inclusive to distinguish possible new effects from established mechanisms. Specifically, I discuss angular correlations of forward di-hadrons in d+Au collisions and long-range rapidity correlations in high-multiplicity p+p and Au+Au collisions.

hep-ph↗
arXiv2010

Azimuthal correlations of forward di-hadrons in d+Au collisions at RHIC in the Color Glass Condensate

We present a good description of recent experimental data on forward di-hadron azimuthal correlations measured in deuteron-gold collisions at RHIC, where monojet production has been observed. Our approach is based on the Color Glass Condensate effective theory for the small-x degrees of freedom of the nuclear wave function, including the use of non-linear evolution equations with running QCD coupling. Our analysis provides further evidence for the presence of saturation effects in RHIC data.

hep-ph↗
arXiv2010

Virtual Compton Scattering off a Spinless Target in AdS/QCD

We study the doubly virtual Compton scattering off a spinless target $γ^*P\toγ^*P'$ within the Anti-de Sitter(AdS)/QCD formalism. We find that the general structure allowed by the Lorentz invariance and gauge invariance of the Compton amplitude is not easily reproduced with the standard recipes of the AdS/QCD correspondence. In the soft-photon regime, where the semi-classical approximation is supposed to apply best, we show that the measurements of the electric and magnetic polarizabilities of a target like the charged pion in real Compton scattering, can already serve as stringent tests.

hep-ph↗
arXiv2010

New observables to test the Color Glass Condensate beyond the large-N_c limit

The JIMWLK framework offers a powerful tool to calculate the energy dependence of QCD observables at high energies. Despite a growing number of observables considered for phenomenological analysis, few features of JIMWLK evolution beyond its evolution speed are yet well constrained by experiment. We argue that meson production cross-sections have the potential to provide qualitatively new insights and allow to address issues both beyond the large-N_c limit and at higher twist. These cross-sections generically contain four point functions whose evolution is shown to follow from the JIMWLK framework. The Gaussian truncation is used to provide an efficient and practical means of calculating the evolution of four point correlators beyond the large-N_c limit.

hep-ph↗
arXiv2010

Single Inclusive Hadron Production at RHIC and the LHC from the Color Glass Condensate

Using the unintegrated gluon distribution obtained from numerical simulations of the Balitsky-Kovchegov equation with running coupling, we obtain a very good description of RHIC data on single inclusive hadron production at forward rapidities in both p+p and d+Au collisions. No K-factors are needed for charged hadrons, whereas for pion production a rapidity independent K-factor of order 1/3 is needed. Extrapolating to LHC energies, we calculate nuclear modification factors for light hadrons in p+Pb collision, as well as the contribution of initial state effects to the suppression of the nuclear modification factor in Pb+Pb collisions.

hep-ph↗
arXiv2009

Semi-inclusive Deep Inelastic Scattering at small x

We study the semi-inclusive hadron production in deep inelastic scattering at small $x$. A transverse momentum dependent factorization is found consistent with the results calculated in the small-$x$ approaches, such as the color-dipole framework and the color glass condensate, in the appropriate kinematic region at the lowest order. The transverse momentum dependent quark distribution can be studied in this process as a probe for the small-$x$ saturation physics. Especially, the ratio of quark distributions as a function of transverse momentum at different $x$ demonstrates strong dependence on the saturation scale. The $Q^2$ dependence of the same ratio is also studied by applying the Collins-Soper-Sterman resummation method.

hep-ph↗
arXiv2009

Large parton densities and high-pT physics in heavy-ion collisions

I discuss the role played by large parton densities in the QCD description of high-pT observables in relativistic heavy-ion collisions. In pA collisions, high-pT particles probe large parton densities in the nucleus and provide tests of the Color Glass Condensate (CGC) picture of the small-x part of the nuclear wave function. In AA collisions, high-pT particles carry information on both the Quark-Gluon-Plasma phase, and the Glasma phase created at early times by the collision of two CGCs.

hep-ph↗
arXiv2009

Multiple partonic interactions in heavy-ion collisions

I discuss the role played by multiple partonic interactions (MPI) in the early stages of relativistic heavy-ion collisions, for which a weak-coupling QCD description is possible. From the Color Glass Condensate, through the Glasma and into the Quark-Gluon-Plasma phase, MPI are at the origin of interesting novel QCD phenomena.

hep-ph↗
arXiv2009

On multiple scatterings of mesons in hot and cold QCD matter

We study the propagation of a color singlet q\bar{q} pair undergoing multiple scatterings in hot and cold QCD matter. The interaction of the dipole with the nucleus or plasma is described with the McLerran-Venugopalan and Gyulassy-Wang models respectively. We find identical results when expressed in terms of the saturation momentum of either the nucleus or the plasma. We compare two kinds of multiple scatterings, elastic and inelastic with respect to the target. When allowing the target to scatter inelastically, the difference with the elastic case is suppressed by a 1/N^2_c factor. We also discuss some implications of our results in the following situations: the survival probability of quarkonia in a hot medium, the production of high-p_T heavy mesons in nucleus-nucleus collisions, and the production of vector mesons in deep inelastic scattering off nuclei.

nucl-th↗
arXiv2008

Particle production and saturation at RHIC and LHC

The Color Glass Condensate picture of the nuclear wave function at small-x successfully predicted the suppressed production of high-pT particles at forward rapidities in deuteron-gold collisions at RHIC. This triggered more efforts which resulted in theoretical improvements and predictions for different observables which will provide further phenomenological tests. I review recent theoretical developments and discuss the resulting predictions.

hep-ph↗
arXiv2008

Heavy-quark energy loss and thermalization in a strongly coupled SYM plasma

Using the AdS/CFT correspondence, we compute the radiative energy loss of a slowly decelerating heavy quark with mass M moving through a supersymmetric Yang Mills (SYM) plasma at temperature T at large t'Hooft coupling λ. The calculation is carried out in terms of perturbation in \sqrtλT/M, and the rate of the energy loss is computed up to second order. We explain the physical meaning of each correction and estimate the thermalization time of a heavy quark moving in a strongly-coupled plasma.

hep-ph↗
arXiv2008

Heavy-quark energy loss in pQCD and SYM plasmas

We consider heavy-quark energy loss and pT-broadening in a strongly-coupled N=4 Super Yang Mills (SYM) plasma, and the problem of finite-extend matter is addressed. When expressed in terms of the appropriate saturation momentum, one finds identical parametric forms for the energy loss in pQCD and SYM theory, while pT-broadening is radiation dominated in SYM theory and multiple scattering dominated in pQCD.

hep-ph↗