Transcript "The CMS Heavy-Ion Program"

The CMS Heavy Ion Program
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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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High Rate, Trigger
A new
telescope
for new
probes
Y=4
Rapidity Range
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Hard
probes are
rare
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LHC
RHIC
SPS
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The Central Detector
Pixels
Strips
Coil
EM Cal
Muons
HCal
Iron
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A transverse slice through
CMS
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A slice along Z
Coil
HCAL
ECAL
Tracker
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Forward Detectors
ZDC >8.3
Castor 5.2<<6.6
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Multiplicity/event
Find hits in pixels, using an
energy cut. We also have a
tracklet analysis.
HIJING
default settings
Pixels hits count
Pseudo rapidity
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Low pT hadrons
Efficiency
Find tracks in pixels and use energy
loss vs momentum for particle ID
dN
dpT
pT (GeV/c)
||<1
 pT
pT (GeV/c)
pT (GeV/c)
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Elliptic Flow
Reaction
plane
z
1. Find the reaction plane calorimeters and tracker
2. Use 2, 4 particle correlations or Lee Yang Zeros
Ecal
 0.37
d
dE
y
x
V2 with tracker
V2
 rad
pT (GeV/c)
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Triggering
Trigger increases pT range
by > 2 for many probes
L
Bunch
cross
Interaction Level 1
rate
Event
size
HLT
rate
offline
pp
1034
25ns
40MHz
1/400
1MB
100
KHz
150Hz
PbPb
1027
125ns
8KHz
1/1
2.510MB
8 Khz 10-100
Hz
/cm2
/s
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Finding Jets
Iterative cone (R>=0.5) with background
subtraction:

Rec ET
calculate average energy and dispersion in
tower (in eta rings) for each event
 subtract average energy and dispersion
dNch/d = 5000
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
MC Jet ET (GeV)
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Tracking
Y (m)
pT
 %
0.5
1.0
2.0<<2.5
0.5
<0.5
z


cm
Pointing useful for
heavy quarks
Efficiency ~ 70 %,
fake rate ~ 1%
pT (GeV/c)
Efficiency %

Z (m)
1.0
Fakes %
Single strips
Double strips
Pixels
<0.5
pT (GeV/c)
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High Pt
Charged particles ||<2.5
Assume luminosity = 0.5 nb-1
jet trigger
data
Energy loss from HYDJET
RAA
No
trigger
RAA
10% Central
pT (GeV/c)
pT (GeV/c)
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Photons
Efficiency = 60%
Fake = 3.5%
S/B=4.5
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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Jet fragmention from  jet events
Require photon ET > 70GeV
I =0..5 nb-1
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Quarkonia
Suppression: RHIC similar to SPS
 Large Cross-section: 20 x RHIC
Regeneration compensate screening
 melts only at LHC: TD~4 TC
J/ not screened at RHIC (TD~2Tc)
Fewer of bb pairs: less regeneration
LHC: recombination or suppression
Suppression of charmonion
Much cleaner probe than J/
Suppression of B’onium states
y'
c
J/
Branching ration is 5.9% for J/y , 2.5%Y (BR:2.5%)
Background is from decays from /K, b-,c-mesons
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J/y 
+
 
For 0.5 nb-1 we reconstruct 180K J/y
Signal/Background:
~5 for ||<0.8, 1 for ||<2.4
||<2.4
 = 35 MeV
dNch/d = 2500
Produced
Reconstructed 2500
Reconstructed 5000
dNch/d = 5000
pT (GeV/c)
M (GeV)
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Y
+
 
Y ~ 25 000,
Y' ~ 7 000,
Y'' ~ 4 000
Signal/Background:
1 ||<0.8, 0.1 for ||<2.4)
Produced
Reconstructed 2500
||<2.4
||<2.4,  = 90MeV
Reconstructed 5000
mass resolution, 90 MeV
M (GeV)
pT (GeV/c)
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Photon nucleus
Max photon energy ~ 80 GeV
Pb: S ≈ 1. TeV/n
 S ≈ 160 GeV
Mee (GeV)
M (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
CMS:
Inner detector
ECAL, PbWO4
Cast
or
0.0174x0.0174
HF
HCAL (sampling)
0.087x0.087 (HB)
0.087->0.17 (HE)
HF
Cast
or
Inner detector (||<2.5)
ECAL (||<3)
HCAL (||<3)
HF (3<||<5)
Muon (||<2.4)
Castor (5<||<6.7)
ZDC (||>8)
Muon Spectrometer
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