Heavy Ion Physics with the CMS detector

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Heavy Ion Physics with the CMS detector
Olga Kodolova, INP MSU
for
Collaboration
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Quark-Gluon Plasma (QGP)

• The temperature and energy density in A-A
  interactions may be high enough to get the
  super-dense QCD state in the quasi-macroscopic
  volumes - QGP (in comparing with hadrons scale)

Freeze-out and hadronic state
Heating and density increaseQGP formation
Initial state
Pre-equilibrium state
hadronization

• Hard tests (pT, Mgtgt?QCD200 ???)
• High-pt particle spactra and its angular
• correlations
• Jets
• Onia
• Heavy quarks flow

• Soft tests (pT?QCD200 ???)
• Low pt particle spectra and particles
• correlations
• Flow effects
• Thermal photons and dileptons
• Strangeness flow

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(No Transcript)
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Overview

• From RHIC to LHC
• CMS detector
• QCD matter in the soft sector
• dNch/dh
• low pT p/K/p spectra
• Eliptic flow
• QCD matter in the hard sector
• high-pT hadrons, jets, photon-jet
• Qqbar suppression
• Y-ll- photoproduction

• High and low pt tracking
• Muon reconstruction
• Jet reconstruction
• Photon reconstruction
• Event plane
• Event centrality

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Some evidences from RHIC
Deflection from Hydro Viscosity?
Calor Glass Condensate?
Local equilibrium in Freeze-out stage?
Same J/y suppression at SPS and RHIC More
suppression in forward
Strong interaction of Dense matter with High pt
hadrons sQGP at RHIC? LHC-?
LHC--? Suppression vs regeneration?
And many other questions to LHC
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From RHIC (200 GeV/n-n) to LHC (5500 GeV/n-n)

• Initial state fully in the saturated CGC regime
• Initial energy density 5 times higher
• Lifetime of a quark-gluon plasma much longer
• Large rates of hard probes over a broad
  kinematical range
• Plenty of heavy quarks (b,c)
• Weakly interacting probes become available (Z0,
  W?)

High pT
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CMS detector
TOTEM
CASTOR
ZDC
Large Range of Hermetic Coverage Tracker, muons
????????? ECAL HCAL
??????? Forward HCAL ??????????? CASTOR
??????????????? ZDC
8.3lt????
8.3 lt????
5.2 lt?????lt 6.6
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CMS detector for heavy ion physics

• Strongest magnetic field
• 4 T, 2 T (return yoke)
• Silicon tracker
• Momentum resolution is
• 2 for tracks with
• pT lt100 GeV
• Good efficiency and low
• fake rate for pTgt1 GeV/c
• low occupancy of pixel
• detectors 1-2 with PbPb
• central events
• Good separation of
• Onia families

Coil
HCAL
ECAL
Tracker

• Fine grained high resolution calorimeter with
• hermetic coverage up to hlt5
• (hlt7 proposed with CASTOR)
• ZDC accepted hgt8.3
• Jet finder coverage up to h lt5 and
• photons coverage up to h lt3
• Muon stations with
• precise measurement of position
  (momentum)
• fast response at LVL1 trigger

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Bulk (hydro) measurements in AA collisions
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Charged particle multiplicity gluon density
Pixels hits count
HIJING default settings
CGC prediction
First measurement at LHC
Simple measurements via hits count in pixels
accomplished with dE/dx cut or tracklets with
vertex constraints
11 cm
Endcap pixels
Barrel pixels
Beam
Final AA multiplicity gluon density
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Soft hadron spectra (CMS) medium equation of
state
Single hadron (p-, K-, p ) pT spectra in
pT0.2-2 GeV/c PID via dE/dx (Gaussian unfolding)
hlt1
Collective radial flow, hadron ratios, thermalizat
ion time, medium equation of state constraints
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Eliptic flow medium viscosity
Initial spatial anisotropy
y
?
x
- defines ?R, (direction of the impact parameter)
Final momentum anisotropy
py
px
dN/d(? - ?R ) N0 (1 2v1cos (?- ?R)
2v2cos (2(?- ?R)) ... )
LHC
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Eliptic flow
Two methods 1. Using reaction plane
determination with Calorimeters and tracker 2.
Cumulant analysis using two and multi particle
correlations cos(2(f1-f2)) v22

Event plane resolution with ECAL 0.37 radian
V2 with tracker
Azimuthal ET distribution in different
calorimeter layers
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Hard probes of QCD matter Qaurkonia and heavy
quarks Jets and high-pT hadrons
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Hard probes triggering for HI in CMS
CMS trigger system is designed for 1034 (pp
events) with 40 MHz bunch crossing rate. Two
levels system Level 1 and High Level Trigger
pp 40 MHz
DAQ/HLT 100 KHz
Offline 150 Hz
Level 1 1/400
DAQ/HLT 1/600
150 Hz, 1.5 MB
100 KHz, 1MB
PbPb Luminosity(cm-2s-1) 1027 Event rate
(KHz) 8 Event size after L1(MB)
2.5 (Minbias)
10 (Central)
Pb-Pb 8 KHz
DAQ/HLT 8 KHz
Offline 10100 Hz
1/1
1/80-1/800
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Jet finder in CMS for HI

• Iterative cone (Rgt0.5) with background
  subtraction
• mean value is determined on an
• event-by-event basis
• 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
  

CMS Iterative cone (Rgt0.5) with background
subtraction
ETrec vs ETgen

dNch/dh 5000
Space resolution is less then the size of
calorimeter tower
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High-pt tracking
3 pixel layers in barrel, 2 pixel layers in
endcap Silicon layers 10 in barrel
11 in endcap
Resolution barrel 1 endcap 2-2.5
Efficiency 70 , fake rate 1
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High-pt hadron spectra
different centrality bins for 0.5 nb-1
jet trigger data
Jet energy loss model in HYDJET
Nuclear modification function reach for 0.5 nb-1
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Photon reconstruction
Efficiency 60 Fake 3.5 S/B4.5
Photon reconstruction with Island
Algorithm Photon ID using Multi-Variate Analysis
with 21 variables grouped into 3 sets ECAL
cluster shape and ECAL/HCAL/Tracker isolation cuts
Performance
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Fragmentation function measurements
FF(x)
FF(z)
gjet events are used UE background subtracted
using R0.5 cone transverse to jet
direction Functions are relative to photon energy
RFF(x)
Integrated luminosity 0.5 nb-1
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Dissociation of quarkonia hot QCD thermometer
Suppression of C'onium states
Suppression of B'onium states
y'
J/?

• Quarkonia J/y (BR5.9), Y (BR2.5)
• Background combinatorial due- to decays from
  p/K, b-,c- production

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J/y measurements
Excellent mass resolution ?J/? 35 MeV/c2,
both muons with ?lt2.4
CMS
Signal/Background 5(1) for J/y in ?lt0.8
(?lt2.4) Expected rate (per month, 106s, 0.5
nb-1) J/y 180 kevents
Expected rate (per month,106s, 0.5 nb-1)
J/y 180 kevents
both muons with ?lt2.4
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Upsilon measurements
Excellent mass resolution ?Y 54 MeV/c2
?lt0.8, ?Y 90 MeV/c2 ?lt2.4
CMS
mass resolution, 54 MeV
Signal/Background 1 (0.1) for Y in ?lt0.8
(?lt2.4)
?lt2.4
CMS
mass resolution, 90 MeV
CMS
?lt2.4
Y 25 kevents, Y' 7 kevents, Y'' 4 kevents
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Ultra-peripheral collisions

• At LHC the accelerated Pb nucleus can produce
  strong electromagnetic field
• due to the coherent action of the Z 82 proton
  charges
• Equivalent photon flux E?max 80 GeV
• ??Pb cm Emax 1. TeV/n (3ep HERA)
• ??? cm Emax 160 GeV (LEP)
• Measure the gluon distribution function in the
  nucleus (?Pb)
• low background
• simpler initial state
• ?Pb?? photo-production in CMS
• Unexplored (x,Q2) regime
• Pin down amount of low-x suppression in the Pb
  nuclear PDF (compared to the proton PDF)

dAu
eA
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Summary
The excellent capabilities of CMS give the unique
possibility of measuring both soft and hard
probes of the dense medium state
Multiplicity soft and hard spectra of
charged particles photons Jets
Quarkonia some other probes
that are not covered by presentation
Dihadron and dijet correlations HBT
Heavy Ion Physics program at LHC starts with the
FIRST pp data Post-Summary next Slide
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Post-Summary
Heavy ion physics starts with pp runs ! Taking
into account the first AA run first pp data are
extremely important for success in first AA run
200 pb-1
Take pp measurements as reference to AA run
B-PAG
Crucial quarkonia measurements
pt-eta spectra primary and
secondary J/y production

• Multiplicity, charged particle spectra (low and
• high), important input for MC heavy ion models.
• Jet fragmentation, jet shape, jet spectra as
  input for
• RAA measurements.

QCD-PAG
EWK-PAG
Z-production important input for MC heavy ion
models
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First Pb-Pb data NEXT YEAR!
First AA run next year
-gt2
Note from Chamonix meeting Early Pb Beam will
have lower energy. 10TeV pp corresponds to 4 TeV
in PbPb

• First Heavy Ion run is scheduled for 2010
• Running at nominal PbPb conditions expected in
  2012
• Main tasks for the next half an year is to
  prepare HLT/DAQ
• and to identify the first AA run papers.

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First A-A run

• The low interaction rate in year-1 should allow
  us to write all min bias events to mass storage
• Deploy full HI HLT to tag events and to test
  efficiencies and functionality
• Fully functional HLT needed at nominal luminosity
• We need to estimate carefully what analyses can
  be done with statistics of
• 8-80 mlns of events 1-10 µb1
• Note nominal run is 0.5 nb-1

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Backup slides
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CMS detector for heavy ions

• Silicon Tracker (Pixels and Strip)
• Electromagnetic Calorimeter (PbWO4)
• Central hadron Calorimeter
• (plastic brass absorber)
• Forward calorimeter (Quartz-fiber and ferum)
• Muon Chambers (Drift tubes in barrel,
• Cathod strip chambers in endcap,
  RPC)
• CASTOR
• Zero-degree calorimeter
• TOTEM
• 4 T magnetic field (solenoid), 2 T return yoke
• momentum resolution lt 2 for pTlt100 GeV
• Fast DAQ allows to take almost all events
• to HLT farm

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CMS acceptance
CMS
Inner detector (hlt2.5) ECAL (hlt3) HCAL
(hlt3) HF (3lthlt5) Muon (hlt2.4) Castor
(5lthlt6.7) ZDC (hgt8)
Inner detector
ECAL, PbWO4 0.0174x0.0174
HF
HF
Castor
Castor
HCAL (sampling) 0.087x0.087 (HB) 0.087-gt0.17 (HE)
Muon Spectrometer