Logo et image Alice

Infos 31 pays, 111 instituts, ~ 1000 collaborateurs Membres du groupe ALICE IPNO Bruno Espagnon (MC resp) Yves Le Bornec (DR) Cynthia Hajidakis (CR) Christophe Suire (CR) Bruno Boyer (These) Mercedes Lopez-Noriega (Post-doc) Daniel Tapia Takaki (Post-doc) Louis Bimbot (DR 50%) Nicole Willis (jeune retraitee) Marie-Pierre Comets (detachement ASN)

dN/dh = 3.10 ± 0.13 (stat) ± 0.22 (syst) p+p @ √snn = 0.9 TeV Accepted by EPJC for publication on 1 Dec. 2009 Le 23 novembre 20009 : 43 minutes de collisions, 234 bons evenements enregistres  Nombre moyen de particules chargees a rapidite centrale : dN/dh = 3.10 ± 0.13 (stat) ± 0.22 (syst) A partir du 6 decembre, le LHC offre des “faisceaux stables, 435890 evenements collectes a √snn = 0.9 TeV (tout ALICE) et des faisceaux “quiet” ~60000 evenements a √snn = 2.36 TeV (tracker silicium) dN/deta at 2.36 TeV, statistical error negligible final systematic error under evaluation (still 7% for the time being) last time measured at the ISR for pp last time measured at the ISR for pp

Le spectrometre a muon asg gs Distribution en moment tranverse des muons reconstruits sur un echantillon de 200 000 evenements « min-bias » : les premières comparaison données-simulations donnent un accord remarquable (sans « fine-tuning ») ! asg

Collision p+p @ √snn = 900 GeV p+p @ √snn=900 GeV, les premiers di-muons sont observes

Historique 2007 : installation et intégration Décembre 2007 : premier “cosmic run Full Alice” avec la station 1 (Orsay) du spectromètre a muons. 2008 : installation et intégration continuent Deux “cosmic run Full Alice” Incident LHC 2009 : intégration continue, plus de tests… Un muon “ cosmic run” (03/09) “cosmic run Full Alice” 23 Novembre 2009 : Les premières collisions p+p at √snn = 900 GeV Le premier cluster

LHC first beams and collisions http://www.lhcportal.com/Forum/viewtopic.php?f=4&t=219 http://en.wikipedia.org/wiki/Large_Hadron_Collider http://proj-lhc-software-analysis.web.cern.ch/proj-lhc-software-analysis/usecase/squeeze.htm

Historique Decembre 2009 : la premiere trace d’un muon dans un collision p+p observee dans le spectrometre

Number of events ALICE : ATLAS : CMS : LHCb 435890 good events at √snn = 0.9 TeV with all detectors ~60000 events at √snn = 2.36 TeV with ITS only ATLAS : ~540000 events at √snn = 0.9 TeV with all detectors (especially the Si-tracker) ~ 34000 events at √snn = 2.36 TeV (Si-tracker not always ?) CMS : number of events extracted from luminosity (30% error) but 10 (0.4) µb-1 @√snn = 0.9 TeV (2.36)  400000 (16000) events LHCb 342360 good events at √snn = 0.9 TeV with all detectors ~ 30000 events at √snn = 2.36 TeV (no Si-Tracker/VeLo)

p+p @ √snn = 0.9 TeV ALICE first paper November 23rd, around 16h40, the first pp collision appeared on the online display (ALIEVE) a) 284 good events recorded in 43 minutes b) Only ITS, 6 layers of silicon pixel, drift and strip detectors, is powered on. NB : ALICE is the only LHC experiment that switched on its internal tracker for the very first collisions. LHC beams were declared quiet not stable ! c) No B field d) Goal was clearly to get the first LHC paper : dn/dη with SPD tracklets (i.e. tracks made of SPD hits only )

p+p @ √snn = 0.9 TeV ALICE first paper Accepted by EPJC for publication on 1 Dec. 2009 The average number of charged particles created perpendicular to the beam in pp collisions at 900 GeV is: dN/dh = 3.10 ± 0.13 (stat) ± 0.22 (syst) Pas assez de statistique pour la physique du spectrometre a muon 435890 good events at √snn = 0.9 TeV with all detectors ~60000 events at √snn = 2.36 TeV with ITS only Cependant …. dN/deta at 2.36 TeV, statistical error negligible final systematic error under evaluation (still 7% for the time being) last time measured at the ISR for pp last time measured at the ISR for pp

Les premiers muons 9 runs selected (taken during 11-12 Dec. 2009).

J/ψ in p+p at √snn = 900 GeV 3 di-muons candidates seen in the Alice muon spectrometer… but Quite understandable : ~ 20 µb-1 of p+p @ √snn = 900 GeV If : σJ/ψ ~ 1 µb, BR J/ψµ-µ+ =6% , Acc. x Eff. spectro ~ 0.1 x 0.9 Expected nof of J/ψ = 0.1 Let’s try in 2010 ! Run 104852; Ev650 Inter. and Muon trig minv = 0.81 GeV/c2 Run 104867; Ev170 Inter. and Muon trig minv = 1.8 GeV/c2 Run 104892; Ev650 Inter. and Muon trig minv = 0.79 GeV/c2

“Demain”, p+p @√snn = 7 TeV Quelques dizaines (centaines ?) de pb-1 en collisions p+p  Physique QCD, statistique a peine suffisante pour la physique electro-faible Et surtout quelques centaines de millions de collisions Pb+Pb @√snn = 7 TeV