1 the cms heavy ion program michael murray kansas
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The CMS Heavy Ion Program
Michael Murray Kansas
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CMS is a running experiment
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Overview
The detector Soft Physics
Multiplicity ,k,p at low pt Flow
Hard Physics Jets Photons Quarkonia Photon nucleus
Z Jet Event
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Rapidity Range
A new telescope for new probes
Hig
h R
ate
, Tri
gg
er
Y=4
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LHC
RHIC
SPS
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Hard probes are rare
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The Central Detector
Pixels
Strips
EM Cal
HCal
Coil
Muons
Iron
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A transverse slice through CMS
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HCAL
ECAL
Tracker
Coil
A slice along Z
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Castor 5.2<<6.6
ZDC >8.3
Forward Detectors
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HIJING default settings
Pixels hits count
Multiplicity/event
Pseudo rapidity
Find hits in pixels, using an energy cut. We also have a tracklet analysis.
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||<1
Low pT hadrons
Find tracks in pixels and use energy loss vs momentum for particle ID
pT (GeV/c)pT (GeV/c)
pT (GeV/c)
pT
Effi
cie
ncy
dNdpT
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1. Find the reaction plane calorimeters and tracker 2. Use 2, 4 particle correlations or Lee Yang Zeros
Ecal 0.37
V2 with tracker
Elliptic Flow Reaction plane
x
z
y
rad pT (GeV/c)
V2
d dE
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Triggering
L /cm2
/s
Bunch cross
Interaction rate
Level 1 Event size
HLT rate
offline
pp 1034 25ns 40MHz 1/400 1MB 100 KHz
150Hz
PbPb 1027 125ns 8KHz 1/1 2.5-10MB
8 Khz
10-100 Hz
Trigger increases pT range by > 2 for many probes
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dNch/d = 5000
Iterative cone (R>=0.5) with background
subtraction: calculate average energy and dispersion in
tower (in eta rings) for each event subtract average energy and dispersion
from each tower find jets with a jet finder algorithm (any)
using the new tower energies recalculate average energy and dispersion
using towers free of jets recalculate jet energies
Done, but can do more iterations
Space resolution is less then the tower size
Finding Jets
MC Jet ET (GeV)
Rec ET
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1.0
Efficiency ~ 70 %, fake rate ~ 1%
pT (GeV/c)
<0.5
Single stripsDouble stripsPixels
Z (m)
Y (m)
Effi
cie
ncy %
Fakes %
1.00.5
0.5
pT %
z cm
2.0<<2.5
<0.5Pointing useful for heavy quarks
pT (GeV/c)
Tracking
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jet trigger
data
High Pt Assume luminosity = 0.5 nb-1
10% Central
Energy loss from HYDJET
No trigger
RAA
RAA
pT (GeV/c)
Charged particles ||<2.5
pT (GeV/c)
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Efficiency = 60%Fake = 3.5%S/B=4.5
Photons
Photon ID based only on cluster shape and isolation cuts using a multi-variate analysis. We reconstruct photon energy with Island algorithm
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I =0..5 nb-1
Jet fragmention from jet events
Require photon ET > 70GeV
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c
Suppression: RHIC similar to SPS
Regeneration compensate screening
J/ not screened at RHIC (TD~2Tc)
LHC: recombination or suppression
Suppression of B’onium states
Large Cross-section: 20 x RHIC
melts only at LHC: TD~4 TC
Fewer of bb pairs: less regeneration
Much cleaner probe than J/
'
J/
Quarkonia
Branching ration is 5.9% for J/ , 2.5%Y (BR:2.5%)
Background is from decays from /K, b-,c-mesons
Suppression of charmonion
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J/ +-
dNch
/d = 5000
dNch
/d = 2500
For 0.5 nb-1 we reconstruct 180K J/
Signal/Background:
~5 for ||<0.8, 1 for ||<2.4
= 35 MeV
||<2.4
Produced
Reconstructed 2500
Reconstructed 5000
pT (GeV/c) M (GeV)
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||<2.4, = 90MeV
mass resolution, 90 MeV
||<2.4
Y ~ 25 000,
Y' ~ 7 000,
Y'' ~ 4 000Signal/Background: 1 ||<0.8, 0.1 for ||<2.4)
Y +-
M (GeV)
Produced
Reconstructed 2500
Reconstructed 5000
pT (GeV/c)
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Photon nucleus
Max photon energy ~ 80 GeVPb: S ≈ 1. TeV/n S ≈ 160 GeV
M (GeV)
Mee (GeV)
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Summary
CMS has an excellent opportunity to study partonic matter at both soft and hard scales, via
• Multiplicity
• Soft spectra
• Flow
• Forward Physics
• Quarkonia
• Hard spectra
• Photons
• Jets
• Z
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Backup slides
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CMS acceptance
ECAL, PbWO40.0174x0.0174
Inner detector
HCAL (sampling)0.087x0.087 (HB)0.087->0.17 (HE)
HFHF
Muon Spectrometer
Castor
Castor
CMS:
Inner detector (||<2.5)ECAL (||<3)HCAL (||<3)HF (3<||<5)Muon (||<2.4)Castor (5<||<6.7)ZDC (||>8)