Status of Heavy Ion
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1Sasha Milov ATLAS IL meeting Jan 03, 2011
Status of Heavy Ion
Sasha Milov
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Sasha Milov ATLAS IL meeting Jan 03, 2011 2
LHC run2010 with Pb+Pb
At the end of 2010 LHC took a very successful data with Pb+Pb @ √sNN = 2.75 TeV
Both LHC and ATLAS performances were beyond expectations. ChronologicallyNov 2: end of p+p+2days: injecting Pb+2days: first collisions+2days: stable beams+2days: 4x4 bunches+2-3days 64x64bunchesNov 24: first PRL. 9.2ub-1 (7.7b cross section)Dec 24: J/psi & Z paper
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A HI event
Sasha Milov ATLAS IL meeting Jan 03, 2011
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The HI event.
Sasha Milov ATLAS IL meeting Jan 03, 2011
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Sasha Milov ATLAS IL meeting Jan 03, 2011 5
A oicture needs to be expained
Find a high-pT particle
Look around it in p+p and find a jet
Look at 180o and find its back-to-back partner
The same in d+Au
Find the near-side jet in A+A
And no back-to-back partner
Partners of the hard-scattered probes are absorbed in the media.
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Pictures which do not...
Sasha Milov ATLAS IL meeting Jan 03, 2011
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The results
Sasha Milov ATLAS IL meeting Jan 03, 2011
p+p reference (open circles) the same in all plots.MC (yellow histogram) does not imply the media effectsSmall asymmetry di-jets reduce with centrality, large asymmetry di-jets increase with centrality.All jets peak at -π Possibly there is some broadening of the jets
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Sasha Milov ATLAS IL meeting Jan 03, 2011 8
MultiplicityarXiv:1012.1657v1
arXiv:1011.3916v2
ATLAS: analysis ongoingThe most central bin well agrees With ALICE paper
Better rapidity coverage
Several independent methods
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Sasha Milov ATLAS IL meeting Jan 03, 2011 9
MultiplicityUse Pixel detector only: low occupancy, low pT cut, wide coverage.Method 1: Combine all hits and confirm B-layer hit with layer 1 hit. Method 2: Combine all hits then flip the detector and subtract the combinatorialMethod 3: use standard pixel tracks with (in no field runs)
Columbia U.
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Sasha Milov ATLAS IL meeting Jan 03, 2011 10
MultiplicityUse Pixel detector only: low occupancy, low pT cut, wide coverage.Method 1: Combine all hits and confirm B-layer hit with layer 1 hit. Method 2: Combine all hits then flip the detector and subtract the combinatorialMethod 3: use standard pixel tracks with (in no field runs)
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Sasha Milov ATLAS IL meeting Jan 03, 2011 11
FlowThe Fourier transform of azimuthal distributionThere all odd coefficients especially important is v2Known to be large at RHIC
Px
Py PzRea
ctio
n pl
ane
X
Z
Y
f
Nc
h y
ield
Multiplicity
(sca
led
) F
low
Krakow
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Sasha Milov ATLAS IL meeting Jan 03, 2011 12
Flow
12
17 Nov: arXiv:1011.3914, acc. PRL
STAR at RHIC
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Sasha Milov ATLAS IL meeting Jan 03, 2011 13
Spectra. dNAA/dpT
σpp<TAB> dNpp/dpT RAA=
Phys. Rev. Lett. 91, 072301 (2003)
~2008 -- 2010
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Sasha Milov ATLAS IL meeting Jan 03, 2011 14
Spectra.ALICE 1012.1004v1
Approximately 20%of run statistics
Central (0-10%)
Peripheral(60-80)%
Figure is 2 weeks old. There is lot more statistics
BNL; WIS
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Sasha Milov IDTCP meeting Dec 07, 2010 15
Data vs. MC (HIJING)Data and MC look different:Total number of tracks above
pT=0.5 GeV is similar, but HIJING has lower pT (no flow).
As a result the tracks with pT<0.5 produce more hits per track above the threshold
Data MC
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Sasha Milov IDTCP meeting Dec 07, 2010 16
Hit statistics in MinBiasPer track hit statistics reflects
the detector occupancy Pixel<SCT<TRT
The effects are also consistent to what is expected from HIJING
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Sasha Milov IDTCP meeting Dec 07, 2010 17
Hit statistics in Data and MC look different:Total number of tracks above
pT=0.5 GeV is similar, but HIJING has lower pT (no flow).
As a result the tracks with pT<0.5 produce more hits per track above the threshold
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Sasha Milov IDTCP meeting Dec 07, 2010 18
Hit statistics in centrality
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Sasha Milov IDTCP meeting Dec 07, 2010 19
Vertex pointing in pT
Selecting primary particles using the p+p cuts gives good resultspT dependent
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Sasha Milov IDTCP meeting Dec 07, 2010 20
Further optimization.
Need to look at centrality and (may be) in charge.
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Sasha Milov IDTCP meeting Dec 07, 2010 21
Further optimization.And in rapidity?
Main questions:1. How to clean the secondaries?2. How far in pT can we go before being overwhelmed by feed-downs3. How to correct for efficiency?
neg posdifferent cuts
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Sasha Milov ATLAS IL meeting Jan 03, 2011 22
Tri
gg
er a
nd
cen
tral
ity
WIS
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Tri
gg
er a
nd
cen
tral
ity
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Two particle correlations
SUNYSB (chem)