Guiot, Benjamin Charles

We present a perturbative QCD based model for vacuum and in-medium hadronization. The effects of induced energy loss and nuclear absorption have been included. The main objective is the determination of the relative contribution of these mechanisms to the multiplicity ratio observable, measured in semi-inclusive deep-inelastic scattering off deuterium and nuclear targets. This is directly related to the determination of the production length, Lp, necessary for a quark to turn into a prehadron. We compare our results with HERMES data for multiplicity ratio and pt-broadening, and show that the description of the whole data set, keeping the model parameters fixed, puts strong constrains on Lp. Contrary to induced-energy-loss based models, we find an important contribution from nuclear absorption at HERMES energies. Finally, we discuss some consequences of our study for the LHC physics, and we present the model predictions for the future EIC experiment.

We discuss the different Kimber-Martin-Ryskin (KMR) prescriptions for unintegrated parton distribution functions (uPDFs). We show that the strong-ordering (SO) and the angular-ordering (AO) cutoffs lead to strong discrepancies between the obtained cross sections. While the result obtained with the AO cutoff overestimates the heavy-flavor cross section by about a factor of 3, the SO cutoff gives the correct answer. We also solve the issue of the KMR uPDF definitions mentioned by Golec-Biernat and Staśto [Phys. Lett. B 781, 633 (2018)] and show that, in the case of the AO cutoff, the KMR uPDFs are ill defined.

Lepton deep inelastic scattering off nuclei at medium energies gives the opportunity to study the space-time development of hadronization. Indeed, for these kinematics, the production length is comparable to the nuclear size. Based on the Berger model [1] and dipole phenomenology, we built a model for vacuum and in-medium hadronization. The model, which includes vacuum energy loss, induced energy loss and nuclear absorption in a parameter-free way successfully describes Hermes data [2, 3]. In a future publication, Fermi motion will be taken into account and the model will be applied to CLAS Eg2 data, at Jefferson laboratory.

We study the propagation of charm quarks in the quark-gluon plasma (QGP) created in ultrarelativistic heavy-ion collisions at LHC within EPOSHQ model. The interactions of heavy quarks with the light partons in ultrarelativistic heavy-ion collisions through the collisional and radiative processes lead to a large suppression of final D-meson spectra at high transverse momentum and a finite D-meson elliptic flow. Our results are in a good agreement with the available experimental data.

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.

We analyze two consequences of the relationship between collinear factorization and 𝑘𝑡-factorization. First, we show that the 𝑘𝑡-factorization gives a fundamental justification for the choice of the hard scale 𝑄2 done in the collinear factorization. Second, we show that in the collinear factorization there is an uncertainty on this choice which will not be reduced by higher orders. This uncertainty is absent within the 𝑘𝑡-factorization formalism.