[email protected] 1 Logo et image Alice.
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Transcript of [email protected] 1 Logo et image Alice.
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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)
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p+p @ √snn = 0.9 TeV
Accepted by EPJC for publication on 1 Dec. 2009
last time measured at the ISR for pp
Le 23 novembre 20009 : 43 minutes de collisions, 234 bons evenements enregistres Nombre moyen de particules chargees a rapidite centrale :
dN/d = 3.10 ± 0.13 (stat) ± 0.22 (syst)
last time measured at the ISR for pp
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)
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• gs
Le spectrometre a muon
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 ») !
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Collision p+p @ √snn = 900 GeV
p+p @ √snn=900 GeV, les premiers di-muons sont observes
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Historique
Le premier cluster
• 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
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Historique
• Decembre 2009 : la premiere trace d’un muon dans un collision p+p observee dans le spectrometre
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Number of events
• ALICE :– 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)
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p+p @ √snn = 0.9 TeVALICE 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 ofsilicon pixel, drift and stripdetectors, 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 )
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p+p @ √snn = 0.9 TeVALICE first paper
Accepted by EPJC for publication on 1 Dec. 2009
last time measured at the ISR for pp
The average number of charged particlescreated perpendicular to the beam
in pp collisions at 900 GeV is:dN/d = 3.10 ± 0.13 (stat) ± 0.22 (syst)
last time measured at the ISR for pp
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 ….
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J/ψ in p+p at √snn = 900 GeV
Run 104892; Ev650Inter. and Muon trigminv = 0.79 GeV/c2
Run 104867; Ev170Inter. and Muon trigminv = 1.8 GeV/c2
Run 104852; Ev650Inter. and Muon trigminv = 0.81 GeV/c2
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/ψµ-µ+ =6% , Acc. x Eff. spectro ~ 0.1 x 0.9
Expected nof of J/ψ = 0.1 Let’s try in 2010 !
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“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
