status of heavy ion
DESCRIPTION
Status of Heavy Ion. Sasha Milov. LHC run2010 with Pb+Pb. At the end of 2010 LHC took a very successful data with Pb+Pb @ √ s NN = 2.75 TeV Both LHC and ATLAS performances were beyond expectations. Chronologically Nov 2: end of p+p +2days: injecting Pb +2days: first collisions - PowerPoint PPT PresentationTRANSCRIPT
1Sasha Milov ATLAS IL meeting Jan 03, 2011
Status of Heavy Ion
Sasha Milov
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
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The HI event.
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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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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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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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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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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
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Krakow
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Flow
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17 Nov: arXiv:1011.3914, acc. PRL
STAR at RHIC
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Spectra. dNAA/dpT
σpp<TAB> dNpp/dpT RAA=
Phys. Rev. Lett. 91, 072301 (2003)
~2008 -- 2010
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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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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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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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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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Hit statistics in centrality
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Vertex pointing in pT
Selecting primary particles using the p+p cuts gives good resultspT dependent
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Further optimization.
Need to look at centrality and (may be) in charge.
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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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Tri
gg
er a
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tral
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WIS
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Tri
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Two particle correlations
SUNYSB (chem)