richard hollis university of illinois at chicago heavy-ions in cms 24 th winter workshop on nuclear...
Post on 15-Jan-2016
217 views
TRANSCRIPT
Richard HollisUniversity of Illinois at Chicago
Heavy-Ions
in CMS
24th Winter Workshop on Nuclear Dynamics
25th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S
Expected energy densityat the LHC
CMS Heavy-Ion program
Study of QCD matter under extreme conditions
Pb+Pb @ √sNN=5.5 TeV Bulk observables
(soft physics) Hard probes Ultra peripheral
collisions
p+p @ √s=14 TeV First measurements of
bulk observables Analysis exercise
“…presents the capabilities of the CMS experiment to explore the rich heavy-ion physics programme offered by
the CERN Large Hadron Collider (LHC) .”
dET/d → ϵBj J.D.Bjorken, Phys.Rev.D27(1983) 140
J. Phys. G: Nucl. Part. Phys. 34 (2007) 2307-2455
35th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S The CMS detector
Under construction
Data!
Basic layout: Tracker E/M Cal.E/M Cal. Hadronic Cal.Hadronic Cal. Magnet Iron Return yoke Muon Chambers
Transverse SliceCosmic muon in CMSat full magnetic field
45th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S The CMS detectorC
MS
co
vera
ge
Silicon tracker: ||<2.5 Momentum resolution <2% for
pT<100GeV and ||<0.5.
Calorimetry: ECal ||<3, HB,HE,HF ||<5, Castor 5<||<7, ZDC ||>8
Wide energy-space range measure of jets Muon Chambers: ||<2.5
Position/momentum along with a fast L1 response
Casto
r
Casto
r
Jet
0
2
2
-8 -6 -4 -2 0 8642
Pixel+Strips
Ecal
Hcal
Muons
ZDCZDC
Calorimetry
Tracker
Soft Physicsin CMS
centrality
dNch/didentified low-pT spectra
65th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S
Soft physics:
Global Event Characterization
Centrality: Forward ET measurements
(CASTOR and Had. Cal.)
Multiplicity: via single-pixel layers
(PHOBOS-Style)• Possible as the pixel layer
occupancy is <2% for dN/d~3500
via integrated Spectra
(next slides)
75th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S
Soft physics:
Global Event Characterization
Good efficiency and resolution pT resolution ~1-2% (barrel)
K p
Low-momentum tracking
dE/dx measurement using the inner silicon layers
PID for ±, K± (p<0.8 GeV/c) and protons (p<1.5 GeV/c)
p-p @ 14 TeV (Pythia)
85th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S
Soft physics:
Global Event Characterization
Further PID: Neutral hadrons from decay
topology (, K0, , , …)
Comprehensive Low-pT physics program to study Freeze-out parameters:
• Chemical potential (B) and temperature
• Kinetic freeze-out temperature and radial flow
Baryon transport and strangeness production
Hard Probesin CMS
charged hadron spectrafull jet reconstruction-Jet
105th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S
PbPb background[HYDJET 010 dN/d~2400]
190 GeV photon [PYTHIA]
quenched jet [PYQUEN]
Full CMS sim reco
Large acceptance calorimetry (ECal+HCal) Fully reconstruct jets in
heavy ion collisions Photon reconstruction in
ECal
4T magnetic field Momentum resolution
<2% Low fake rates
High-Level Triggering Online inspection of all
events extends pT reach to 250 GeV/c (1 year)
minimum bias HLTriggeredPbPb dNch/d|y=0=3500
Hard probes:
CMS Capabilities
115th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S
Jet reconstruction utilizes Hcal and Ecal
Iterative cone (R=0.5) + Background subtraction High efficiency and purity for
ET>50 GeV jets Good energy resolution for
ET>100 GeV Jets reconstructed up to ET~ 0.5
TeV• Estimated for one “year” of
running PbPb 0.5 nb-1
(or 3.9x109 events,106 sec)
Hard probes:
Reconstructing Jets
125th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S
Hard probes:
-Jet
Direct probe for in-medium energy loss
Reconstruction Photon ID: combine
Ecal/Hcal/tracker to form isolation cuts
135th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S
Hard probes:
-Jet
Direct probe for in-medium energy loss
Reconstruction Photon ID: combine
Ecal/Hcal/tracker to form isolation cuts
Use of Multivariate analysis For = 60%, fake = 3.5%
selectedworking point
145th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S
Hard probes:
-Jet
Direct probe for in-medium energy loss
Reconstruction Photon ID: combine
Ecal/Hcal/tracker to form isolation cuts
Use of Multivariate analysis For = 60%, fake = 3.5%,
S/B=4.5
155th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S
Hard probes:
-Jet
Direct probe for in-medium energy loss
Reconstruction Photon ID: combine
Ecal/Hcal/tracker to form isolation cuts
Use of Multivariate analysis For = 60%, fake = 3.5%,
S/B=4.5 Away-side jet selection
ET > 30 GeV, ||< 2, ,jet > 1720
Calculate dN/dξ Charged tracks in R=0.5 cone
around jet axis
PbPb background[HYDJET 010 dN/d~2400]
190 GeV photon [PYTHIA]
quenched jet [PYQUEN]
Full CMS sim reco
Defining Fragmentation Functions:
ξ = log(ET/pT)
ET usually defined from parton ET of the jet. Here, the ET is used as we are trying to quantify partonic jet quenching.
165th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S
Hard probes:
-Jet Direct probe for in-medium
energy loss
Final Measurement Reconstruction using non-
quenched and quenched MC Fragmentation functions differ
Medium modification of fragmentation functions can be discriminated with high significance
Significant difference between
Non-quenched and QuenchedAnalysis method has discriminatory power
Low-pT
High-pT
suppressed
Heavy Flavorin CMS
J/ and ’
family
185th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S
Heavy Flavor:
family
Reconstructed
-
in CMS
PbPb underlying event:
dN/dy ~3500
CMS: precise measurements of muons: tracker + chambers
195th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S
Heavy Flavor:
family
PbPb=2500
Signal/Background~1Clear separation of states
Direct probe of QGP formation “Step suppression” of
charmonium/bottomonium resonances
• Sensitive to QGP temperature
Reconstruction performance Excellent dimuon mass resolution
~1% of the quarkonium mass for full
Best Signal/Background at LHC• Clean separation of the states
205th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S
Heavy Flavor:
family
N~2.5 104
1-yearstatistical
reach
Broad coveragep T
(G
eV/c
)
Direct probe of QGP formation “Step suppression” of
charmonium/bottomonium resonances
• Sensitive to QGP temperature
Reconstruction performance Excellent dimuon mass resolution
~1% of the quarkonium mass for full
Best Signal/Background at LHC• Clean separation of the states
Broad -coverage and high-pT reach Using HLT selection
215th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S
Heavy Flavor:
J/ and ’
Direct probe of QGP formation “Step suppression” of
charmonium/bottomonium resonances
• Sensitive to QGP temperature
Reconstruction performance Excellent dimuon mass resolution
~1% of the quarkonium mass for full
Best Signal/Background at LHC• Clean separation of the states
Broad -coverage and high-pT reach Using HLT selection
NJ/~1.8×105
Di-m
uon
mas
s re
cons
truc
tion
1-ye
arst
atis
tical
rea
ch
Broad coverage
PbPb=2500
J/y=35MeV/c2
||<2.4
S/B~1.2
J/ acceptance
p T (
GeV
/c)
Ultra Peripheral
in CMS
235th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S
Ultra peripheral collisions:
photo-production
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 Emax ~ 80 GeVPb: cm Emax ≈ 1. TeV/n (~3×e+p 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
245th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S Summary
CMS has a broad and exciting heavy ion program, including: Bulk observables (soft physics)
255th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S Summary
CMS has a broad and exciting heavy ion program, including: Jet physics Quarkonia and heavy-quarks Ultra peripheral collisions
265th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S Vintage Years Ahead
CMS DATA 2008GENEVE, SWITZERLAND
2000 PHYSICISTS, (INCL) 50 HEAVY-IONS
Produced by CERN, distributed via your local T1 center.
GOVERNMENT WARNING: (1) ACCORDING TO THE SURGEON GENERAL, ANALYZING CMS DATA MAY CAUSE SEVERE EUPHORIA. (2) ANALYZING CMS DATA MAY IMPAIR YOUR ABILITY TO DRIVE, PLEASE DON’T ANALYZE DATA WHILST YOU DRIVE
$12 CHF 452m(1995 budget)
“Physics World” 1st May 2000
275th-12th April 2008
Richard HollisUniversity of Illinois at Chicago
24th Winter Workshopon Nuclear Dynamics
C M S The CMS detectorce
ntra
l det
ecto
rstr
ansv
erse
slic
e
Global Event Characterization: Silicon tracker: (±, K±, p), , K0 (via
displaced vertices) Infer energy density, freeze-out
temperatures and chemical potential...
Specific Probes: Calorimetry: e± , and hadronic jets
probe of early times and jet-medium interactions, energy loss…
Muon Chambers: μ± (from J/ψ, ) (heavy) quark energy loss and
sensitivity to QGP temperature…