Physics opportunities at A Fixed Target ExpeRiment at the LHC (AFTER@LHC)
by
Jean-Philippe Lansgerg((IPN-Orsay))
→
UTC
LIP seminar room
LIP seminar room
Description
We outline the physics opportunities [1] which are offered by a next
generation and multi-purpose fixed-target experiment exploiting the LHC
beams extracted by a bent crystal. This mature extraction technique
offers an ideal way to obtain a clean and very collimated high-energy
beam, without altering at all the performance of the LHC [2,3,4]. The
multi-TeV LHC beams grant the most energetic fixed-target experiment
ever performed, to study pp, pd and pA collisions at sqrt(s_NN) ~ 115
GeV and PbA collisions at sqrt(s_NN) ~ 72 GeV. AFTER -- for A
Fixed-Target ExperRiment -- gives access to new domains of particle and
nuclear physics complementing that of collider experiments, in
particular RHIC and the projects of electron-ion colliders. The typical
instantaneous luminosity achievable with AFTER in pp and pA mode [1]
surpasses that of RHIC by more than 3 orders of magnitude and is
comparable to that of the LHC collider mode. This provides a quarkonium,
heavy-flavour and prompt photon observatory [5] in pp and pA collisions
where, by instrumenting the target-rapidity region, gluon and
heavy-quark distributions of the proton, the neutron and the nuclei can
be accessed at large x and even at x larger than unity in the nuclear
case. Precise data from pp, pA and PbA should help to understand better
heavy-quark and quarkonium production, to clear the way to use them for
gluon and heavy-quark PDF extraction in free and bound nucleons, to
unravel cold from hot nuclear effects and to restore the status of heavy
quarkonia as a golden test of lattice QCD in terms of dissociation
temperature predictions at a sqrt(s_NN) where the recombination process
is expected to have a small impact. The fixed-target mode also has the
advantage to allow for spin measurements with polarized targets. The
polarization of hydrogen and nuclear targets allows an ambitious spin
program, including measurements of the QCD lensing effects which
underlie the Sivers single-spin asymmetry.
[1] S. J. Brodsky, F. Fleuret, C. Hadjidakis and J. P. Lansberg, Phys.
Rept. 108 522 (2013) 239.
[2] E. Uggerhøj, U. I. Uggerhøj, Nucl. Instrum. Meth. B 234 (2005) 31.
[3] W. Scandale, et al., Phys. Lett. B 703 (2011) 547-551.
[4] W. Scandale, et al. [LUA9], CERN-LHCC-2011-007, 2011.
[5] J. P. Lansberg, S. J. Brodsky, F. Fleuret and C. Hadjidakis, Few
Body Syst. 53 (2012) 11ç