Quarkonia Measurements by the CMS Experiment in pp and PbPb Collisions
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Transcript of Quarkonia Measurements by the CMS Experiment in pp and PbPb Collisions
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Quark Matter 2011, Annecy, May 23-29 2011
Quarkonia Measurements by the CMS Experiment
in pp and PbPb Collisions
Catherine Silvestre Tello
for the CMS Collaboration
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Quarkonia in Heavy Ion Collisions• Good candidates to probe the QGP in HIC
– Large masses and (dominantly) produced at the early stage of the collision via hard-scattering of gluons
– Strongly bound resonances
[email protected] (LPSC) Quarkonia CMS - Quark Matter 2011 2
→decreasing binding energy
The start : quarkonia should melt in the QGPT. Matsui & H. Satz PLB178, 416 (1986)
Color Screening
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A Complex Production• Production mechanism not completely understood
• Many effects altering production in nuclear reactions – In pA, cold nuclear matter (CNM) effects
• Extensively studied at the SPS and RHIC• But different at the LHC ?
– In AA, hot medium effects
[email protected] (LPSC) Quarkonia CMS - Quark Matter 2011 3
The NNLO* is not a complete NNLO → possibility of (large) uncanceled logs !If NNLO* ≈ NLO, problem with polarization
J-P Lansberg (Tues)
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RHIC J/Suppression Puzzles
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• No increase of the suppression with local densityRAA (|y|<0.35) > RAA (1.2<|y|<2.2)
• Similar suppression at SPS and RHIC energiesRAA (RHIC, |y|<0.35) ≈ RAA (SPS)
• Possible ingredients–Suppression (gluon diss.)
–Sequential melting
–Gluon saturation / shadowing
–Regeneration
–Some combination of all
J/
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Compact Muon Solenoid
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MUON BARREL
Silicon Strips Pixels
Drift Tube (DT)
SOLENOID3.8 T B-field
TRACKER
MUON ENDCAPS
Resistive PlateChambers (RPC)
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Quarkonia in CMS
• Precision quarkonia physics– High statistics run pp √s=7 TeV Lint=40 pb-1
• Nuclear modification factor – PbPb √sNN=2.76 TeV Lint=7.28 b-1
– pp √s=2.76 TeV Lint=225 nb-1
•Similar hard probes statistics
•Good reference
•Same reconstruction algorithm
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PbPb
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Inclusive J/
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pp √s=7 TeV
|yJ/|<0.5=20 MeV/c2
N J/(120.5 ± 0.8) 10⋅ 3
J/ ’
Lint=40 pb-1
|y|<0.5
• b-quark physics
• Quarkonia physics
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B → J/
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• Reconstruct µ+µ− vertex• Simultaneous fit
– Invariant mass – Pseudo-proper decay length
pp √s=7 TeV
1.6<|y|<2.4
EPJC 71:1515 (2011)
Torsten Dahms (Tues. 15h)
Mihee Jo(poster 458)
FLASH TALK !
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J/ Cross Section
• Prompt J/ production not well reproduced• Models describe non-prompt J/ production better
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PROMPT
pp √s=7 TeV
NON PROMPT
EPJC 71:1515 (2011)
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States
• Very good dimuon mass resolution→ separation of the 3 states
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pp √s=7 TeV
|| < 2.4= 100 MeV/c2
|| < 1= 67 MeV/c2
1S
2S3S
1S
2S3S
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Cross Section
• Pythia (LO / CSM+COM)– Reasonable agreement in shape– But not in normalization
(overestimated by about a factor 2)[email protected] (LPSC) Quarkonia CMS - Quark Matter 2011 13
(1S)
pp √s=7 TeV
arXiv : 1012.5545accepted by PRD
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Quarkonia in pp
• Summary of the 7 TeV run– Differential charmonia and bottomonia
• Constrain production mechanisms
– In progress• c, ’, quarkonium polarization
• Heavy ion reference run √s=2.76 TeV
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= 36 MeV/c2
pTJ/
> 6.5 GeV/c
pT > 4 GeV/c
1026 ± 35 J/
101±12
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Di-muons by CMS in PbPb
[email protected] (LPSC) Quarkonia CMS - Quark Matter 2011
Torsten Dahms Tuesday 15h00
Zhen HuMonday 19h10
Jorge Robles Thursday 15h00
PAS CMS HIN-10-006
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Inclusive J/
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Torsten Dahms (Tues. 15h)
PbPb √sNN=2.76 TeV
734 ± 54 J/
Similar resolution as in pp
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First Non-Prompt J/
90 ± 13 B → J/
b-quark physics
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Torsten Dahms (Tues. 15h)
Mihee Jo(poster 458)
FLASH TALK !
pTJ/
> 6.5 GeV/c
PbPb √sNN=2.76 TeV
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Corrections
Acceptance from MC
Efficiency : centrality
dependence ~17%
• Efficiency from MC, checked with data :14% systematics
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Dongho Moon (poster 459, 66)
Hyunchul Kim (poster 460, 67)
PbPb √sNN=2.76 TeV
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Prompt J/ RAA vs. pT
Minimum bias RAA = 0.30 ± 0.02 ± 0.02
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PbPb √sNN=2.76 TeV
pTJ/
> 6.5 GeV/c
PAS CMS HIN-10-006
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J/ RAA vs. pT : Comparison
High pT J/’s tendency to survive at RHIC (and SPS) is not seen at the LHC
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CMSpT
J/ > 6.5 GeV/c
STAR pT
J/ < 8 GeV/c
PHENIX lower pT
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Prompt J/ RAA vs. y
• Less suppression at forward rapidity for high pT
• Anti-shadowing ?• CMS@pT=10 up to x2~0.02 (x1~5.10-4)
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PbPb √sNN=2.76 TeV
CMS
Q2=10 GeV2
EPS09 NLOnDSg NLO
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J/ RAA vs. y : Comparison
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CMSpT
J/ > 6.5 GeV/c
PHENIX lower pT
J/
• CMS : opposite trend than PHENIX but different pT
• Increasing RAA going towards ALICE y rangeCMS@pT=10 up to x2~0.02 (x1~5.10-4)ALICE@pT=0 up to x2~0.06 (x1~2.10-5)
ALICECMS
Q2=10 GeV2
EPS09 NLOnDSg NLO
CMS for pT>3 GeV/c1.6<y<2.4RAA= 0.39±0.06±0.03
ALICE Low pTJ/
RAA= 0.49±0.03±0.11
M. Wysocki (Poster)
P. Pillot (Tues.)
- Watch out for anti-shadowing :
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Prompt J/ RAA
Central 0-10% RAA= 0.20 ± 0.03 ± 0.01
Peripheral 50-100% RAA= 0.59 ± 0.12 ± 0.10
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Factor 5 suppression
PbPb √sNN=2.76 TeV
CMSpT
J/ > 6.5 GeV/c
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J/ RAA vs. Npart Comparison
[email protected] (LPSC) Quarkonia CMS - Quark Matter 2011
Phys.Lett.B697:294-312,2011
40-80%
Compatible with ATLASRcp= 0.5 ± 0.2
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STAR √s=200 GeV, J/ 5 < pT < 8 GeV/c
Stronger suppression seen in CMS than at STAR
Z. Tang (Mon.)
P. Steinberg (Mon.) R. Sandstrom (Thur.)
CMSpT
J/ > 6.5 GeV/c
STAR5<pT
J/<8 GeV/c
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(parenthesis from quarkonia : b-quark energy loss)
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First B → J/ RAA
Minimum bias RAA = 0.37 ± 0.07 ± 0.03
Central 0-20% RAA= 0.36 ± 0.08 ± 0.03
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b quark energy loss ?
20-100%
PbPb √sNN=2.76 TeV
pT J/> 6.5 GeV/c
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High pT Suppression
B→J/ at the pT of the J/
Same level of suppression as hadrons [email protected] (LPSC) Quarkonia CMS - Quark Matter 2011 28
PbPb √sNN=2.76 TeV
Yen-Jie Lee(Wed.
9h)
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States
[email protected] (LPSC) Quarkonia CMS - Quark Matter 2011 30
Zhen Hu(Mon. 19h10)
PbPb √sNN=2.76 TeV
86 ± 12 (1S)
pT > 4 GeV/c
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(1S) RAA
• Minimum bias RAA= 0.62 ± 0.11 ± 0.10
• High pT not as suppressed ?
– Need more [email protected] (LPSC) Quarkonia CMS - Quark Matter 2011 31
PbPb √sNN=2.76 TeV
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(1S) RAA
• Comparison with STAR– CMS (1S) RAA(0-100) = 0.62 ± 0.11 ± 0.10
– STAR (1+2+3S) RAA(0-60) = 0.56 ± 0.11 +0.02-0.10
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PbPb √sNN=2.76 TeV
R. Reed (poster)
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(2S+3S) Suppression
• (2S+3S) production relative to (1S) in pp and PbPb
• Compare pp and PbPb through a simultaneous fit
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PbPb √sNN=2.76 TeV
pp PbPb
pT > 4 GeV/carXiv : 1105.4894
Submitted to PRL
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(2S+3S) Suppression
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Hypothesis: no suppression ⇒ p-value 1% Significance of the suppression 2.4
PbPb √sNN=2.76 TeV
• Pros of a double ratio– Acceptance cancels– Efficiency cancels
• Potential differences – Remaining systematics 9%,
from line shapes
PbPb
arXiv : 1105.4894Submitted to PRL
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Suppression
• Large fraction of (1S) come from excited states– Feed down ~50% from χb for pT() >8 GeV/c
• 40% suppression of (1S)• Relative suppression of (2S+3S) vs. (1S)
– Observation consistent with melting of the excited states only ?
• What about cold nuclear matter effects ?– Smaller σabs than at lower energy and for J/ (smaller size)
– Shadowing cancelling in the (2S+3S)/(1S) ratio• pA run ?
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PbPb √sNN=2.76 TeV
CDF: PRL84 (2000) 2094
R. Vogt, hep-ph/1003.3497
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Quarkonia Production with CMS
• First non-prompt J/ in HI
– b-quark energy loss
• Prompt J/
significantly suppressed
• (2S)+(3S) excited states suppressed– Consistent with 40% 1S) suppression
[email protected] (LPSC) Quarkonia CMS - Quark Matter 2011 36
no pT cutpT
J/>6.5 GeV/c
Sequential melting accessible with CMS resolution
arXiv : 1105.4894Submitted to PRL
PAS CMS HIN-10-006
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→ e+e- @ RHIC
• PHENIX • Au+Au collisions • High mass correlated
di-electrons are suppressed
• STAR– Au+Au collisions 0-60% – 93 (1,2,3S)
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Nucl.Phys.A855:440-443,2011arXiv:0907.4787
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B → J/Fraction
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pp √s=7 TeV
EPJC 71:1515 (2011)
arxiv 1104.3038
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RAA J/ vs. pT Predictions
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• Range of predictions– Less suppression
• Zhao, Rapp: Due to finite J/ψ formation time, B feed down and Cronin effect
– Stronger suppression
• « Hot wind » model – cc pair in motion w.r.t. hot medium ⇒ decrease of screening length.
_
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pp Comparison
• pp 2.76 TeV • pp 7 TeV
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Same pp reconstruction, including low pT J/Agreement of the (2S+3S)/(1S) ratio
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p-value
• Generate pseudo-experiments following the null-hypothesis
(i.e. no suppression)• Fit pseudo-data samples with
nominal fit• Count fraction of occurrences for
which the ratio (taken as test statistic) is same or lower than observed:– p-value: 0.9%– 2.4σ (1-sided Gaussian test)
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Could background fluctuation produce a result as extreme as observed in data?
0.31
Zhen Hu (Purdue) Quark Matter 2011, Annecy, May 23-29 2011
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J/ RAA Comparison
[email protected] (LPSC) Quarkonia CMS - Quark Matter 2011
CMSpT
J/>6.5 GeV/c
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PbPb √sNN=2.76 TeV
• PHENIX √s=200 GeV, inclusive J/, pTJ/<5 GeV/c
• SPS, PHENIX, LHC: similar centrality dependence– But different pT, systems and energies