# Quark Matter 2012

12-18 August 2012
US/Eastern timezone

## Prospective for A Fixed-Target ExpeRiment at the LHC: AFTER@LHC

17 Aug 2012, 17:30
20m

Oral Presentation Experiment upgrades, new facilities, and instrumentation

### Speaker

Andry Malala Rakotozafindrabe (CEA - Centre d'Etudes de Saclay (FR))

### Description

We outline the physics opportunities~\cite{Brodsky:2012vg} 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 the performance of the LHC~\cite{Uggerhoj:2005xz,Scandale:2011zz,LUA9}. The multi-TeV LHC beams grant the most energetic fixed-target experiment ever performed, to study \pp, \pd\ and \pA\ collisions at \mbox{$\sqrt{s_{NN}} \simeq 115\,\mathrm{GeV}$} and \PbA\ collisions at \mbox{$\sqrt{s_{NN}} \simeq 72\,\mathrm{GeV}$}. 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~\cite{Brodsky:2012vg} 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 and heavy-flavour observatory 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. The nuclear target-species versatility provides a unique opportunity to study cold nuclear matter versus the features of the hot and dense matter formed in heavy-ion collisions, including the formation of the quark-gluon plasma. During the one-month lead runs, \PbA\ collisions can be studied at a luminosity comparable to that of RHIC and the LHC over the full range of target-rapidity domain. Modern detection technology should allow for the study of quarkonium excited states, in particular the $\chi_c$ and $\chi_b$ resonances, even in the challenging high-multiplicity environment of \pA\ and \PbA\ collisions, magnified by the boost of the fixed-target mode. Precise data from \pp, \pA\ and \PbA\ should help to greatly improve our understanding of 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 \sqrtsNN\ 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. We will discuss a tentative design for AFTER, and report the projected detector performances from the first preliminary simulations. \begin{thebibliography}{4} \bibitem{Brodsky:2012vg} S.~J.~Brodsky, F.~Fleuret, C.~Hadjidakis and J.~P.~Lansberg, arXiv:1202.6585 [hep-ph]. %%CITATION = ARXIV:1202.6585;%% \bibitem{Uggerhoj:2005xz} E.~Uggerh\o j, U.~I.~Uggerh\o j, Nucl.\ Instrum.\ Meth.\ B {\bf 234} (2005) 31. %%CITATION = NUIMA,B234,31;% \bibitem{Scandale:2011zz} W.~Scandale, {\it et al.}, Phys.\ Lett.\ {\bf B703 } (2011) 547-551. \bibitem{LUA9} W.~Scandale, {\it et al.} [LUA9], CERN-LHCC-2011-007, 2011.

### Primary authors

Andry Malala Rakotozafindrabe (CEA - Centre d'Etudes de Saclay (FR)) Bernard Genolini (IN2P3 - CNRS - Université Paris Sud) Cynthia Hadjidakis (Universite de Paris-Sud 11 (FR)) Elena Gonzalez Ferreiro (Universidad de Santiago de Compostela) Enrico Scomparin (Universita e INFN (IT)) Frédéric Fleuret (LLR Ecole Polytechnique, IN2P3/CNRS) Mr J.P. Didelez (IPN Orsay) Jean-Philippe Lansberg (Ecole Polytechnique) Mr Philippe Rosier (IPN Orsay) Roberta Arnaldi (Universita degli Studi di Torino-Universita e INFN) Mr Stanley J. Brodsky (SLAC) Mr Ulrik Ingerslev Uggerhoej (University of Aarhus) Valerie Chambert (IPN Orsay)

### Presentation Materials

 AFTER-AndryR.key AFTER-AndryR.pdf