ALICE general results and upgrades. Massimo Masera on behalf of the ALICE Collaboration University of Torino and I.N.F.N. - Italy [email protected]. LISHEP 2011 - Workshop on LHC – Present and Future 4,10 July 2011. Outline. The ALICE experiment Present detector performance - PowerPoint PPT Presentation
First measurements of charged particle multiplicity in p-p
collisions at the LHC with the ALICE experiment
Massimo Masera on behalf of the ALICE CollaborationUniversity of
Torino and I.N.F.N. - Italy [email protected] general results
and upgrades
LISHEP 2011 - Workshop on LHC Present and Future 4,10 July
2011Outline09/07/2011The ALICE experimentPresent detector
performance Results from 2010 Pb-Pb run: Global event features Two
particle correlation and flow Hard processes: heavy flavours and
J/yThe future: plans for an upgrade of the ALICE
detectorsConclusions
2LISHEP 2011I had to make choices: Pb-Pb results: pp only as a
baseline Justa a (personal) selection of the available results
Heavy Ions at the LHC09/07/201132010Targets / nucleon
pairTeV2.765.5Initial luminositycm-2 s-1310251027Number of
colliding bunches137592Bunch spacingns50099.8*m3.50.5Transverse
normalized emittancem31.5Ions per bunch1.21087107
LISHEP 2011ALICE: A Large Ion Collider Experiment Indeed ALICE
has been designed to be the general purpose Heavy Ion experiment at
the LHCALICE has also a physics programme for pp collisions, that
are used as a reference for Pb-PbPbPb run: from Nov, 7 2010 30
daysCollected statistics: 3.75 b-1 (30 M hadronic m.b.
interactions)09/07/20114
ALICE numbets: 1200 members100 institues30 CountriesLISHEP
201109/07/2011PLC 20J. Schukraft
Complete since 2008: ITS, TPC, TOF, HMPID,FMD, T0, V0, ZDC, Muon
arm, Acorde PMD , DAQ
Partial installation (2010): 4/10 EMCAL* (approved 2009)7/18
TRD* (approved 2002)3/5 PHOS ~ 60% HLT (High Level Trigger)
2011 10/10 EMCAL10/18 TRD
*upgrade to the original setupITSTPCTRDTOFEMCALPHOSHMPIDL3
MagnetDetector statusLISHEP 20115Detector
PerformanceTrackingVertexingPID09/07/20116LISHEP 2011
Tracking09/07/2011LISHEP 20117Tracking capabilities in the
central barrel are crucial for most of the physics topics addressed
in Pb-Pb collisionsTracking detectors: Inner Tracking System (ITS),
Time Projection Chamber (TPC) and Transition Radiation Detector
(TRD)Algorithm based on Kalman filter, with seeding in the TPC. ITS
is used as a standalone tracker with leftover pointsHermetic
detectors: very high efficiency for |h|5 GeV/cCharm RAA: comparison
with p09/07/2011LISHEP 201131
Suppression for charm not too different w.r.t. that for pionsD
mesons seem to be less suppressed for pT RAA pions: Energy loss for
gluon > energy loss for quarks (Casimir factor) Energy loss of
massless partons > energy loss of heavy quarks (dead cone
effect)Heavy Flavours from m and e09/07/2011LISHEP 201132
Semileptonic decays of HF contribute to the electron and muon
yields(Inclusive electron spectra) (cocktail of known sources) is
dominated by HF for pT>3-4 GeV/cMuon yield is suppressed by a
factor of ~3 for pT>6 GeV/c, where is dominated by Beauty RAA
for muons and electrons are compatible within the large electron
signal systematic uncertainties09/07/2011LISHEP 201133
Comparison with modelsLittle shadowing at medium-high pT (as
predicted by EPS09 for cold nuclear matter) suppression is a hot
matter effectLow pT rise: pPb data needed to understand itRadiative
Eloss (BDMPS-ASW) D & muon lie on the same
curveRadiative+collisional (WHDG @ 2.76 TeV)Fair
descriptionLight-cone wave function approach with dissociation
(Vitev)OK for muons (beauty)
J/ RAA: pp reference09/07/2011LISHEP 201134 3 days of data
taking @ 2.76 TeVSample: 20.2 nb-1 (13.3 nb-1 used for the present
analysis @ 7 TeV )J/y yield extracted from a fit to the invariant
mass spectrum (crystal ball shape for the signal + double
exponential for the background)Good agreement of differential cross
sections with pQCD
J/ RAA: results09/07/2011LISHEP 201135
Contribution from B feed-down:~ 10% from p-p measurement (LHCb
Coll., arXiv:1103.0423)Rough estimation assuming simple scaling
with Ncoll: ~ 11% reduction of RAA0-80%
Inclusive J/ RAA0-80% = 0.49 0.03 (stat.) 0.11 (sys.) Bars:
statistical errorsOpen rectangles: systematic errors dependent on
centrality Filled rectangle: common systematics Suppression of ~0.5
Cold Nuclear Matter Effects not measured pPb data needed for thisJ/
RAA: comparison with RHIC09/07/2011LISHEP 201136ALICE data plotted
as a function of J/y less suppressed at LHC (2.5
