2,559 research outputs found
Impact of the Nuclear Modification of the Gluon Densities on J/Psi production in pPb collisions at sqrt(s_NN) = 5 TeV
We update our previous studies of nuclear-matter effects on J/Psi production
in proton-nucleus for the recent LHC pPb runs at sqrt(s_NN)=5 TeV. We have
analysed the effects of the modification of the gluon PDFs in nucleus, using an
exact kinematics for a 2->2 process, namely g+g->J/Psi+g as expected from LO
pQCD. This allows to constrain the transverse-momentum while computing the
nuclear modification factor for different rapidities, unlike with the usual
simplified kinematics. Owing to the absence of measurement in pp collisions at
the same sqrt(s_NN) and owing to the expected significant uncertainties in
yield interpolations which would hinder definite interpretations of nuclear
modification factor --R_pPb--, we have derived forward-to-backward and
central-to-peripheral yield ratios in which the unknown proton-proton yield
cancel. These have been computed without and with a transverse-momentum cut,
e.g. to comply with the ATLAS and CMS constraints in the central-rapidity
region.Comment: 5 pages, 16 figures, LaTeX. v2: predictions on R_CP and 3 references
added; introduction slightly extende
J/\psi\ and \psi' production in proton(deuteron)-nucleus collisions: lessons from RHIC for the proton-lead LHC run
We study the impact of different cold nuclear matter effects both on J/\psi\
and \psi' production, among them the modification of the gluon distribution in
bound nucleons, commonly known as gluon shadowing, and the survival probability
for a bound state to escape the nucleus --the nuclear absorption. Less
conventional effects such as saturation and fractional energy loss are also
discussed. We pay a particular attention to the recent PHENIX preliminary data
on \psi' production in dAu collisions at sqrt{s}=200 GeV, which show a strong
suppression for central collisions, 5 times larger than the one obtained for
J/\psi\ production at the same energy. We conclude that none of the
abovementioned mechanisms can explain this experimental result.Comment: 4 pages, 2 tables, 2 figures, contribution to Rencontres du Vietnam,
'Heavy Ion Collisions in the LHC Era', 15-21 July 2012, Quy Nhon, Vietna
Open-beauty production in Pb collisions at =5 TeV: effect of the gluon nuclear densities
We present our results on open beauty production in proton-nucleus collisions
for the recent LHC Pb run at =5 TeV. We have analysed the
effect of the modification of the gluon PDFs in nucleus at the level of the
nuclear modification factor. Because of the absence of measurement in
collisions at the same energy, we also propose the study of the
forward-to-backward yield ratio in which the unknown proton-proton yield
cancel. Our results are compared with the data obtained by LHCb collaboration
and show a good agreement.Comment: 6 pages, 3 figures, Proceedings IS2013 submitted to Nuclear Physics
Feasibility studies for quarkonium production at a fixed-target experiment using the LHC proton and lead beams (AFTER@LHC)
Used in the fixed-target mode, the multi-TeV LHC proton and lead beams allow
for studies of heavy-flavour hadroproduction with unprecedented precision at
backward rapidities - far negative Feyman-x - using conventional detection
techniques. At the nominal LHC energies, quarkonia can be studies in detail in
p+p, p+d and p+A collisions at sqrt(s_NN) ~ 115 GeV as well as in Pb+p and Pb+A
collisions at sqrt(s_NN) ~ 72 GeV with luminosities roughly equivalent to that
of the collider mode, i.e. up to 20 fb-1 yr-1 in p+p and p+d collisions, up to
0.6 fb-1 yr-1 in p+A collisions and up to 10 nb-1 yr-1 in Pb+A collisions. In
this paper, we assess the feasibility of such studies by performing fast
simulations using the performance of a LHCb-like detector.Comment: 12 pages, 14 figure
On the theoretical and experimental uncertainties in the extraction of the J/psi absorption cross section in cold nuclear matter
We investigate the cold nuclear matter effects on production, whose
understanding is fundamental to study the quark-gluon plasma. Two of these
effects are of particular relevance: the shadowing of the parton distributions
and the nuclear absorption of the pair. If 's are not
produced {\it via} a process as suggested by recent theoretical
works, one has to modify accordingly the way to compute the nuclear shadowing.
This naturally induces differences in the absorption cross-section fit to the
data. A careful analysis of these differences however requires taking into
account the experimental uncertainties and their correlations, as done in this
work for Au collisions at \sqrtsNN=200\mathrm{GeV}, using several
shadowing parametrisations.Comment: 6 pages, 1 table, 3 figures, Submitted to J. Phys. G, talk given at
the International Conference on Strangeness in Quark Matter (SQM2009),
Buzios, Brasil, Sep. 27 - Oct. 2, 200
A Fixed-Target ExpeRiment at the LHC (AFTER@LHC) : luminosities, target polarisation and a selection of physics studies
We report on a future multi-purpose fixed-target experiment with the proton
or lead ion LHC beams extracted by a bent crystal. The multi-TeV LHC beams
allow for the most energetic fixed-target experiments ever performed. Such an
experiment, tentatively named AFTER for "A Fixed-Target ExperRiment", gives
access to new domains of particle and nuclear physics complementing that of
collider experiments, in particular at RHIC and at the EIC projects. The
instantaneous luminosity at AFTER using typical targets surpasses that of RHIC
by more than 3 orders of magnitude. Beam extraction by a bent crystal offers an
ideal way to obtain a clean and very collimated high-energy beam, without
decreasing the performance of the LHC. The fixed-target mode also has the
advantage of allowing for spin measurements with a polarised target and for an
access over the full backward rapidity domain up to xF ~ - 1. Here, we
elaborate on the reachable luminosities, the target polarisation and a
selection of measurements with hydrogen and deuterium targets.Comment: 6 pages. Proceedings of the Sixth International Conference on Quarks
and Nuclear Physics QNP2012 (16-20 April 2012, Ecole Polytechnique,
Palaiseau,France
Spin physics at A Fixed-Target ExpeRiment at the LHC (AFTER@LHC)
We outline the opportunities for spin physics which are offered by a next
generation and multi-purpose fixed-target experiment exploiting the proton LHC
beam extracted by a bent crystal. In particular, we focus on the study of
single transverse spin asymetries with the polarisation of the target.Comment: Contributed to the 20th International Spin Physics Symposium,
SPIN2012, 17-22 September 2012, Dubna, Russia, 4 pages, LaTe
Prospectives for A Fixed-Target ExpeRiment at the LHC: AFTER@LHC
We argue that the concept of a multi-purpose fixed-target experiment with the
proton or lead-ion LHC beams extracted by a bent crystal would offer a number
of ground-breaking precision-physics opportunities. The multi-TeV LHC beams
will allow for the most energetic fixed-target experiments ever performed. The
fixed-target mode has the advantage of allowing for high luminosities, spin
measurements with a polarised target, and access over the full backward
rapidity domain --uncharted until now-- up to x_F ~ -1.Comment: 6 pages, 1 table, LaTeX. Proceedings of the 36th International
Conference on High Energy Physics (ICHEP2012), 4-11 July 2012, Melbourne,
Australi
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