ICHEP'06 ICHEP'06 Moscow 26. Moscow 26. 07 - 02.08.2006 07 - 02.08.2006 1 Heavy Ion Physics Heavy Ion Physics with the CMS Detector with the CMS Detector Lyudmila Sarycheva Scobeltsyn Institute of Nuclear Physics Moscow State University For CMS Collaboration 1. 1. CMS detector and Heavy Ion program CMS detector and Heavy Ion program 2. 2. Quarkonia and heavy quarks Quarkonia and heavy quarks 3. 3. Jets and jet quenching Jets and jet quenching 4. 4. Global event characterization Global event characterization 5. 5. Monte-Carlo simulation tools Monte-Carlo simulation tools 6. 6. Summary Summary 7. 7. Appendix Appendix CMS Heavy-Ion Groups: Adana, Athens, Basel, Budapest, CERN, Demokritos, Dubna, Ioannina, Kiev, Krakow, Los Alamos, Lyon, Minnesota, MIT, Moscow, Mumbai, N.Zealand, Protvino, PSI, Rice, Sofia, Strasbourg, U Kansas, Tbilisi,
Heavy Ion Physics with the CMS Detector. Lyudmila Sarycheva Scobeltsyn Institute of Nuclear Physics Moscow State University For CMS Collaboration. CMS detector and Heavy Ion program Quarkonia and heavy quarks Jets and jet quenching Global event characterization - PowerPoint PPT Presentation
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Heavy Ion Physics Heavy Ion Physics with the CMS Detectorwith the CMS Detector
Lyudmila Sarycheva
Scobeltsyn Institute of Nuclear Physics Moscow State University
For CMS Collaboration
1.1. CMS detector and Heavy Ion program CMS detector and Heavy Ion program 2.2. Quarkonia and heavy quarks Quarkonia and heavy quarks 3.3. Jets and jet quenchingJets and jet quenching4.4. Global event characterization Global event characterization 5.5. Monte-Carlo simulation tools Monte-Carlo simulation tools 6.6. Summary Summary 7.7. Appendix Appendix
CMS Heavy-Ion Groups: Adana, Athens, Basel, Budapest,
CERN, Demokritos, Dubna, Ioannina, Kiev, Krakow, Los Alamos, Lyon,
Excellent detector for high pExcellent detector for high pTT probes of quark-gluon plasma: probes of quark-gluon plasma: - High rates and large cross sections- High rates and large cross sections - Quarkonia (J/- Quarkonia (J/,,), heavy quarks ( ) and Z), heavy quarks ( ) and Z00
- High acceptance for calorimeters and muon system - High acceptance for calorimeters and muon system - High p- High pTT jets jets - High energy photons- High energy photons
- multijets- multijets Global event characterizationGlobal event characterization
- Centrality- Centrality - Energy flow to very forward region- Energy flow to very forward region - Charged particle multiplicity- Charged particle multiplicity - Azimuthal anisotropy- Azimuthal anisotropy
Forward physics and ultraperipheral interactionsForward physics and ultraperipheral interactions - Limiting Fragmentation, Saturation, Color Glass CondensateLimiting Fragmentation, Saturation, Color Glass Condensate - Exotica- Exotica
2.5 Heavy quarks b, c 2.5 Heavy quarks b, c / J/ / J/ +X. +X. Secondary vertex finding and correlated background rejectionSecondary vertex finding and correlated background rejection
r is transverse distance between the intersection points with the beam line belonging two different muon tracks
b-quark energy loss affects B-jet fragmentation and modification dimuon spectra depending on mechanism of heavy-quark production (for BB → + ) and intensity of jet quenching
Space-time evolution of dense matter, created in region of initial overlaping of colliding nuclei, is described by Lorenz-invariant Bjorken's hydrodynamics
J.D. Bjorken, PRD 27 (1983) 140
One of the important tools to study QGP properties in ultrarelativistic heavy ion collisions is a QCD jet production: medium-induced energy loss of energetic partons (jet quenching) is very different in cold nuclear matter and in QGP, resulting in many observable phenomena.
3.4 Jet quenching in heavy ion collisions3.4 Jet quenching in heavy ion collisions
Nuclear geometry and QGP evolutionimpact parameter b ≡ |O
3.73.7 Jet fragmentation function can be reconstructed Jet fragmentation function can be reconstructed with CMS tracking systemwith CMS tracking system
Longitudinal momentum fraction z along the thrust jet axis
4.2 Correlation between energy flow and centrality4.2 Correlation between energy flow and centrality
We use energy response of the HF-calorimeter (3 < | We use energy response of the HF-calorimeter (3 < | < 5.2) < 5.2)
where the bulk of reaction energy is deposited for Ar+Ar collisions.where the bulk of reaction energy is deposited for Ar+Ar collisions.
transverse (b) energy responses transverse (b) energy responses
in HF-calorimeter and comparison in HF-calorimeter and comparison with HIJING predictions.with HIJING predictions.
1. E/E1. E/ET T b correlation b correlation
Average resolution of impact Average resolution of impact parameter determination for parameter determination for Ar-Ar collisions is from 0.5 fm Ar-Ar collisions is from 0.5 fm (most central events) up to 1 fm (most central events) up to 1 fm (peripheral events).(peripheral events).
2. 2. Impact parameter resolution Impact parameter resolution σσb using E/ET, b using E/ET, total (a) andtotal (a) and
Determination of the primary charged-particle multiplicity is based on the Determination of the primary charged-particle multiplicity is based on the relation between the pseudorapidity distribution of reconstructed clusters in the relation between the pseudorapidity distribution of reconstructed clusters in the innermost layer of the CMS pixel tracker and that of charged-particle tracks innermost layer of the CMS pixel tracker and that of charged-particle tracks originating from the primary vertex.originating from the primary vertex.
On an event-by-event basis, On an event-by-event basis, the reconstructed multiplicity the reconstructed multiplicity is within 1-2% of the true value is within 1-2% of the true value in the | in the | ηη | < 2 region. | < 2 region.
Single layer hit counting in innermost pixel barrel layer
High granularity pixel detectorsHigh granularity pixel detectors
Pulse height in individual Pulse height in individual pixels to reduce backgroundpixels to reduce background
Very low pVery low pTT reach, p reach, pT T > 26 MeV > 26 MeV (counting hits!)(counting hits!)
5.2 Fast Monte-Carlo tools to simulate jet 5.2 Fast Monte-Carlo tools to simulate jet quenching and flow effectsquenching and flow effects
PYQUENPYQUEN - fast code to simulate jet quenching - fast code to simulate jet quenching (modify PYTHIA6.4 jet event)(modify PYTHIA6.4 jet event) http://cern.ch/lokhtin/pyquenhttp://cern.ch/lokhtin/pyquen
HYDROHYDRO - fast code to simulate transverse and elliptic flow in central- fast code to simulate transverse and elliptic flow in central and semi-central AA collisions at LHC,and semi-central AA collisions at LHC, http://cern.ch/lokhtin/hydro http://cern.ch/lokhtin/hydro
Significant progress in development of Monte-Carlo models for Significant progress in development of Monte-Carlo models for simulation of jet quenching is achieved (PYQUEN, HIDJET). simulation of jet quenching is achieved (PYQUEN, HIDJET).
It describes RHIC data adequately. It describes RHIC data adequately.
See talk of Igor Lokhtin for details.See talk of Igor Lokhtin for details.
At LHC a new regime of heavy ion physics will be reached where hard particleAt LHC a new regime of heavy ion physics will be reached where hard particle production can dominate over soft events, while the initial gluon densities are production can dominate over soft events, while the initial gluon densities are much higher than at RHIC, implying stronger partonic energy loss observable much higher than at RHIC, implying stronger partonic energy loss observable in new channels. in new channels.
CMS is an excellent device for the study of quark-gluon plasma by hard probes:CMS is an excellent device for the study of quark-gluon plasma by hard probes: - - Quarkonia Quarkonia and heavy quarks and heavy quarks - Jets, - Jets, ''jet quenching'' in various physics channels ''jet quenching'' in various physics channels CMS will also study global event characteristics:CMS will also study global event characteristics: - - Centrality, Multiplicity Centrality, Multiplicity
- - Correlation and Correlation and Energy Flow reaching very low pEnergy Flow reaching very low pT T
CMS CMS is preparing to take advantage of its capabilitiesis preparing to take advantage of its capabilities - - Excellent rapidity and azimuthal coverage, high resolutionExcellent rapidity and azimuthal coverage, high resolution
- Large acceptance, nearly hermetic fine granularity hadronic and - Large acceptance, nearly hermetic fine granularity hadronic and electromagnetic calorimetry electromagnetic calorimetry - Excellent muon and tracking systems - Excellent muon and tracking systems - - New High Level Trigger algorithms specific for A+ANew High Level Trigger algorithms specific for A+A
- - Zero Degree Calorimeter, CASTOR and TOTEM will be important Zero Degree Calorimeter, CASTOR and TOTEM will be important additions extending to forward physics additions extending to forward physics
kHz comparable to kHz comparable to collision ratecollision rate
Online Farm
switchswitch
High level trigger High level trigger Full event information available Full event information available Every event accepted by L1 sent to an Every event accepted by L1 sent to an
online farm of 2000 PCsonline farm of 2000 PCs Output rate (Pb+Pb): Output rate (Pb+Pb): ~ 40 Hz~ 40 Hz Trigger algorithm same or similar to Trigger algorithm same or similar to
7.7 Energy-energy correlation function (definition)7.7 Energy-energy correlation function (definition)
d
dE
d
dEd
ENd
d TT
T
T
2
02visevent
event )(
11
ET() – transverse energy flow in , – azimuthal size of a calorimeter sector – azimuthal angle of a calorimeter sector – relative azimuthal angle between two azimuthal sectors
The transverse energy-energy correlator dT/d as a function of relative azimuthal angle without (blue histogram) and with partonic energy loss for the “small-angular” (red histogram) and the “broad-angular” (magenta histogram) parameterizations of emitted gluon spectrum in central Pb-Pb collisions. (Histograms calculated without effects of installation.)
7.8 Energy-energy correlation function 7.8 Energy-energy correlation function ddTT/d/d
For non-central collisions with a clearly visible elliptic flow of the transverse energy
Correlator dT/d is independent of the reaction plane angle R and is calculated explicitly: