M.Poghosyan1 The ALICE experiment at LHC Martin Poghosyan For the ALICE Collaboration SILAFAE 2010...
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M.Poghosyan1 The ALICE experiment at LHC Martin Poghosyan For the ALICE Collaboration SILAFAE 2010 Valparaíso, Chile Dec. 6 - 12, 2010 Pb-Pb (Nov. 2010)
M.Poghosyan1 The ALICE experiment at LHC Martin Poghosyan For
the ALICE Collaboration SILAFAE 2010 Valparaso, Chile Dec. 6 - 12,
2010 Pb-Pb (Nov. 2010) pp (Nov. 2009)
Slide 2
SILAFAE2010M.Poghosyan2 ~1000 members from ~30 countries
Slide 3
SILAFAE2010M.Poghosyan3 PUEBLA, Autonomous Univ. of Puebla
CULIACAN, Universidad Autonoma de Sinaloa MEXICO D.F., Universidad
Nacional Autonoma de Mexico; Inst. de Fisica MEXICO D.F.,
Universidad Nacional Autonoma de Mexico; Inst. de Ciencias
Nucleares MEXICO D.F., Merida, Centro de Investigacion y de
Estudios Avanzados del IPN CINVESTAV HABANA, Centre de Aplicaciones
Tecnologicas y Desarrollo Nuclear ~ 70 members from four Latin
American Countries LIMA, Pontificia Universidad Catolica del Peru
CAMPINAS, Universidade Estadual de Campinas UniCamp SAO PAULO,
Universidade de Sao Paulo, Instituto de Fisica CAMPINAS,
Universidade Estadual de Campinas UniCamp SAO PAULO, Universidade
de Sao Paulo, Instituto de Fisica Hardware V0 (MB trigger) ACORDE
(CR trigger) EMCAL UPGRADES: VHMIPD, AD Analysis Jets/ Event
Structure Cosmic Ray Physics Diffractive Physics Strangeness
Software Unfolding Event Display www Official web page Indico
Slide 4
ITS, TPC, TOF, HMPID, MUON, V0, T0, FMD, PMD, ZDC (100%) TRD
(7/18) EMCAL (4/12) PHOS (3/5) Detector configuration A Large Ion
Collider Experiment High granularity (dN/dy~8000) Minimized
material Good PlD Good acceptance for p t down to 100 MeV/c
SILAFAE2010M.Poghosyan4
Slide 5
ITS, TPC, TOF, HMPID, MUON, V0, T0, FMD, PMD, ZDC (100%) TRD
(7/18) EMCAL (4/12) PHOS (3/5) Detector configuration A Large Ion
Collider Experiment High granularity (dN/dy~8000) Minimized
material Good PlD Good acceptance for p t down to 100 MeV/c
SILAFAE2010M.Poghosyan5 BeamEnergy# of Events pp900 GeV~ 8 M MB
pp2.36 TeV~ 40 k MB pp7 TeV~ 800 M MB ~ 50 M muons ~ 20 M high N ch
PbPb2.76 TeV/Nfew 10 7 MB
Slide 6
SPD1 SPD2 Fiducial window = = 25mdar80 mrad Two innermost
layers of the ITS Radii of 3.9/7.6 cm (|| < 2.0/1.4) ~8 M
channels Trigger & Tracking ~80% active Fast aligned/calibrated
and used to estimate the o position of the interaction point o
number of primary tracks ( || 50 MeV/c) Charged particle
multiplicity measurement with Silicon Pixel Detector z y x
SILAFAE2010M.Poghosyan6
Slide 7
Multiplicity distribution SILAFAE2010M.Poghosyan7 K. Aamodt et
al., EPJ C68 (2010) 345
Slide 8
How to go from Inel>0 to Inel, NSD ? The Inel>0 sample is
an accurate measurement but One has to correct for diffractive
processes for going from Inel>0 to Inel or NSD. Mainly
normalization problem: densities of particles in diff. processes
are rather small at mid-rapidity, but their cross-sections are not
negligible. What is the definition of diffraction? Theory:
coherence, quantum numbers, . Pomeron exchange Experiment: rapidity
gap How much do we really rely on gap measurements with "Swiss
cheese detectors? no data at lower energies for comparison useless
for analytical models SILAFAE2010M.Poghosyan8
Slide 9
Inel. and NSD for ALICE at 0.9 and 2.36 TeV Data samples are
selected as follows: SPD or V0A or V0C for Inel at 900 GeV (at
least one charged particle in 8 units of pseudorapidity) V0A and
V0C for NSD at 900 GeV At 2.36 TeV V0 was not in. MC
(efficiency/process-type/): PYTHIA and PHOJET SD and NSD are mixed
using SD and Inel cross-sections from UA5 and E710 at 900 GeV 0.153
0.023 (UA5) at 1.8 TeV 0.159 0.024 (E710) practically no
extrapolation needed for 2.36 TeV SILAFAE2010M.Poghosyan9 K. Aamodt
et al., EPJ C68 (2010) 89
Slide 10
Measuring SD and DD with ALICE Strategy: Identify diffractive
process based on the kinematics of produced particles in 9 units of
pseudorapidity. ALICE Work in progress ALICE Work in progress ALICE
Work in progress ALICE Work in progress ALICE Work in progress
ALICE Work in progress SILAFAE201010M.Poghosyan Understanding of
diffraction dissociation of hadrons is important for understanding
hh, hA and AA collisions. Diffractive intermediate states have a
small influence on hA and AA total cross-section (at current
energies they are close to a black limit) but they have a strong
impact on hh interaction cross-section and on inclusive spectra in
hh, hA and AA collisions.
Slide 11
PLC 20J. Schukraft 11 p-Nucleus absorption cross section Full
tracking requires much more Alignment Proper transport through
detector Proper material budget description
SILAFAE2010M.Poghosyan11
Slide 12
Spectrum seems to get harder towards mid-rapidity (jets become
oriented in the tr. plane?) Transverse momentum distribution at 900
GeV ITS+TPC tracking SILAFAE2010M.Poghosyan12 K. Aamodt et al.,
Phys. Lett. B693 (2010) 53
Slide 13
Inclusive spectra as a function of s
SILAFAE2010M.Poghosyan13
Slide 14
Number of cut Pomerons ~ s p t 2 ~ Number of cut Pomerons
Number of charged particles ~ Number of cut Pomerons as a function
of N ch SILAFAE2010M.Poghosyan14
Slide 15
PLC 20J. Schukraft No vertex cut ! Particle Identification
SILAFAE2010M.Poghosyan15
Charm at 7 TeV SILAFAE2010 J/ , y = 2.5 - 4 1 J/ e + e - |y|
< 1 M.Poghosyan20
Slide 21
SILAFAE2010 Antiproton/proton ratio at mid-rapidity P = 1.2, =
0.44; C 5 = ln s C = 5.7 1.1 D = -0.15 0.45 Odd = 0.84 0.36 If one
requires D>0: D = 5*10 -9 3.8 M.Poghosyan21 K. Aamodt et al.,
Phys Rev Lett 105 (2010)
Slide 22
SILAFAE2010M.Poghosyan22 BoseEinstein correlations (HBT)
identical pions unlike-sign pions pair momentum multiplicity K.
Aamodt et al., Phys. Rev. D82 (2010) 052001
Slide 23
SILAFAE2010M.Poghosyan23 Source radius at s = 900 GeV Source
radius vs Multiplicity Using different baselines - Radius increases
with N ch, comparable to ISR, RHIC, Tevatron - rather constant vs
flat baseline results to k T dependent radius dependence usually
interpreted as sign of flow in heavy ions K. Aamodt et al., Phys.
Rev. D82 (2010) 052001
Slide 24
SILAFAE2010M.Poghosyan24 Charged particle multiplicity density
at mid-rapidity in central Pb-Pb collisions dN ch /d ~ 1600 76
(syst) at s NN = 2760 GeV Measured value is mainly on high side of
expectations growth with s stripper in AA than in pp K. Aamodt et
al., arXiv:1011.3916
Slide 25
SILAFAE2010M.Poghosyan25 Multiplicity vs centrality in Pb-Pb at
s NN = 2760 GeV submitted to arXive on 7 December
Slide 26
SILAFAE2010M.Poghosyan26 (after tuning) Multiplicity vs
centrality & models
Slide 27
SILAFAE2010M.Poghosyan27 Factor: 2.1 Factor: 4.1 Factor: 2.4
Comparison with the average from RHIC experiments (done by PHENIX)
What is the physics behind this?
Slide 28
SILAFAE2010M.Poghosyan28 dN/d depends on A 4/3 or A 1.1 ? A 4/3
- Gribov-Glauber without enhanced diagramsA 1.1 - Gribov-Glauber
with enhanced diagrams A. Capella, A. Kaidalov, J. Tran Thanh Van,
arXiv:hep-ph/9903244 (note, published before the RHIC era!)
Slide 29
SILAFAE2010M.Poghosyan29 dN/d depends on A 4/3 or A 1.1 ? A 4/3
- Gribov-Glauber without enhanced diagramsA 1.1 - Gribov-Glauber
with enhanced diagrams A. Capella, A. Kaidalov, J. Tran Thanh Van,
arXiv:hep-ph/9903244 (note, published before the RHIC era!) In
fact, this dependence is a consequence of having large- mass
diffractive intermediate states. Thermalisation and QGP formation
strongly depend on the strength of the interactions between
Pomerons. In fact, this dependence is a consequence of having
large- mass diffractive intermediate states. Thermalisation and QGP
formation strongly depend on the strength of the interactions
between Pomerons.
Slide 30
30 v 2 vs pt and centrality practically no change with energy
+30% RHIC ALICE 30% increase from RHIC for p t integrated v 2
(because of increase of ) v 2 as a function of p t v 2 as a
function of centrality SILAFAE2010M.Poghosyan K. Aamodt et al.,
arXiv:1011.3914
Slide 31
R AA = 1 for (very) hard QCD processes in absence of nuclear
modifications Suppression of charged particle production at large p
t SILAFAE201031M.Poghosyan K. Aamodt et al., arXiv:1012.1004
Slide 32
Suppression of charged particle production at large p t
Suppression of high p t particles ( ~ leading jet fragments)
Minimum R AA ~ 1.5 2 x smaller than at RHIC Rising with p t !
(ambiguous at RHIC !) accuracy limited by pp reference
SILAFAE201032M.Poghosyan R AA = 1 for (very) hard QCD processes in
absence of nuclear modifications K. Aamodt et al.,
arXiv:1012.1004
Slide 33
SILAFAE2010M.Poghosyan33 Strangeness in Pb-Pb
Slide 34
SILAFAE2010M.Poghosyan34 Charm in Pb-Pb
Slide 35
SILAFAE2010 ALICE is in a good shape Performance of track and
vertex reconstruction and particle identification close to design
value for both pp and PbPb Physics analysis well underway. Already
some important results during one year of data taking: Conclusions
M.Poghosyan EEEEEEEEEEEEEEEEEE 35 Published results pp N ch
multiplicity & distributions 900 GeV: EPJ C65 (2010) 111 900
GeV, 2.36 TeV: EPJ C68 (2010) 89 7 TeV: EPJ C68 (2010) 345 Momentum
distributions(900 GeV) Phys. Lett. B693 (2010) 53 Bose Einstein
correlations (900 GeV) Phys. Rev. D82 (2010) 052001 pbar/p ratio
(900 GeV & 7 TeV) Phys Rev Lett 105 (2010) Pb-Pb Multiplicity
in central collisions arXiv:1011.3916 v 2 arXiv:1011.3914 RAA
arXiv:1012.1004 Multiplicity vs centrality submitted to arXive on 7
december Many ongoing analysis