François Arleo

Heavy-quarkonium suppression in p-A collisions from parton energy loss in cold QCD matter

A bstractThe effects of parton energy loss in cold nuclear matter on heavy-quarkonium suppression in p-A collisions are studied. It is shown from first principles that at large quarkonium energy E and small production angle in the nucleus rest frame, the medium-induced energy loss scales as E. Using this result, a phenomenological model depending on a single free parameter is able to reproduce J/ψ and Υ suppression data in a broad xF -range and at various center-of-mass energies. These results strongly support energy loss as the dominant effect in heavy-quarkonium suppression in p-A collisions. Predictions for J/ψ and Υ suppression in p-Pb collisions at the LHC are made. It is argued that parton energy loss scaling as E should generally apply to hadron production in p-A collisions, such as light hadron or open charm production.

Proton-nucleus collisions at the LHC: Scientific opportunities and requirements

Proton–nucleus (p+A) collisions have long been recognized as a crucial component of the physics program with nuclear beams at high energies, in particular for their reference role to interpret and understand nucleus–nucleus data as well as for their potential to elucidate the partonic structure of matter at low parton fractional momenta (small-x). Here, we summarize the main motivations that make a proton–nucleus run a decisive ingredient for a successful heavy-ion program at the Large Hadron Collider (LHC) and we present unique scientific opportunities arising from these collisions. We also review the status of ongoing discussions about operation plans for the p+A mode at the LHC.

Inclusive prompt photon production in nuclear collisions at RHIC and LHC

Nuclear modification factors of inclusive prompt photon production in d-Au collisions at RHIC and p-Pb collisions at the LHC are provided at different rapidities. The calculations are performed at NLO accuracy using the EPS09 NLO nuclear parton distribution functions (nPDFs) and their error sets. The results are compared to the ones obtained with the nDS and HKN07 NLO nPDFs, and to the corresponding nuclear modification factors of neutral pion production in these collisions. The sensitivity of these results to the scale choice is also investigated. Interestingly, the predictions using the different nPDF sets differ from each other to the extent that this observable can be expected to become very useful for probing nPDFs over a wide range of Bjorken-x. In order to obtain a perturbative QCD baseline in heavy-ion collisions, calculations are carried out for minimum bias Au-Au collisions at RHIC and Pb-Pb collisions at the LHC. We also estimate the maximal possible suppression which the produced QCD matter can be expected to have on inclusive prompt photon production due to the quenching of the fragmentation component. The nuclear modification factor for prompt photon production is thus suggested to be used for gauging both the cold and the hot nuclear matter effects on other hard processes which are expected to be affected by quark-gluon plasma formation, such as large-pT hadron and jet production.

Probing gluon and heavy-quark nuclear PDFs with γ + Q production in pA collisions

We present a detailed phenomenological study of direct photon production in association with a heavy-quark jet in pA collisions at the Relativistic Heavy Ion Collider (RHIC) and at the Large Hadron Collider (LHC) at next-to-leading order in QCD. The dominant contribution to the cross-section comes from the gluon-heavy-quark (gQ) initiated subprocess, making γ + Q production a process very sensitive to both the gluon and the heavy-quark parton distribution functions (PDFs). Additionally, the RHIC and LHC experiments are probing complementary kinematic regions in the momentum fraction x carried by the target partons. Thus, the nuclear production ratio

Single-inclusive production of large-pT charged particles in hadronic collisions at TeV energies and perturbative QCD predictions

R_{pA}^{\gamma + Q}

(Medium-modified) fragmentation functions

can provide strong constraints, over a broad x-range, on the poorly determined nuclear parton distribution functions which are extremely important for the interpretation of results in heavy-ion collisions.

Next-to-modified leading logarithmic approximation corrections to single inclusive k ⊥ distributions and two-particle correlations in a jet

The single inclusive spectrum of charged particles with transverse momenta pT = 3 – 150 GeV/c measured at midrapidity by the CDF experiment in proton-antiproton

Hadronic single inclusive k perpendicular distributions inside one jet beyond the modified-leading-log approximation.

\left( {p - \bar{p}} \right)

Constraints on nuclear gluon densities from J/ψ data

collisions at

Single inclusive pion p{sub T} spectra in proton-proton collisions at {radical}(s)=22.4 GeV: Data versus perturbative QCD calculations

\sqrt {s} = 1.96{\text{ TeV}}