Upsilon Production in Heavy Ions with STAR and CMS

Upsilon Production inHeavy Ions with STAR

and CMS

Manuel Calderón de la Barca Sánchez

HIT SeminarBerkeley LabSeptember 18, 2012.

Manuel Calderón de la Barca Sánchez 2

Outline

• Bottomonium in heavy ion collisions• Upsilon measurements in:

– STAR– CMS

• Upsilon cross sections in p+p• Upsilon nuclear modification factors• Conclusions

9/18/12 HIT Seminar, Berkeley Lab


Quarkonium in the QGP• Heavy quarkonia:

– Heavy quark bound state are probes of the hot QCD medium

– Debye screening • Matsui & Satz, PLB 178 416 (1986)

– Sequential Suppression• Digal et al., PRD 64 2001 094015

– Landau damping: Im V. • (e.g. Laine et al., JHEP 03 2007

054)


TC<T0<T<TCT=0

ϒ


High T: the interaction between the heavy quarks is modified.

• Charmonium suppression: longstanding QGP signature– Original idea: High T leads to

screening– Screening prevents heavy

quark bound states from forming.

– J/ysuppression: • Matsui and Satz, Phys. Lett. B 178

(1986) 416

– lattice calculations, indications of screening

• Nucl.Phys.Proc.Suppl.129:560-562,2004

– Note: Calculations of internal energy or internal energy

O. Kaczmarek, et al.,Nucl.Phys.Proc.Suppl.129:560-562,2004



The heavy quark potential in QCD• Recent news: Heavy quark potential from (quenched) Lattice QCD

– A.Rothkopf, et al. PRL 108 (2012) 162001

– Broadening due to collisions with medium (Im V) possibly more important than screening (Re V).



Measuring the Temperature

hep-ph/0110406

Dissociation temperatures of quarkonia statesLattice QCD Calculations: Quarkonia’s suppression

pattern QGP thermometer

• For production at RHIC and LHC– A cleaner probe compared to J/y

• co-mover absorption → negligible• recombination → negligible

– d-Au: Cold Nuclear Matter Effects• Shadowing / Anti-shadowing at y~0

• Challenge: low rate, rare probe– Large acceptance detector– Efficient trigger

• Expectation:– (1S) no melting– (2S) likely to melt– (3S) melts

A .Mocsy, 417th WE-Heraeus-Seminar,2008



J/y Puzzles from SPS and RHIC• Similar J/y suppression at the

SPS and RHIC!– despite 10× higher √sNN

• Suppression does not increase with local energy density– RAA(forward)<RAA(mid)

• Possible ingredients– cold nuclear matter effects– sequential melting– regeneration

• What happens for bottomonium?



Charmonium vs Bottomonium• J/y suppression

– Hot nuclear matter effects: Suppression? Regeneration? Co-mover absorption? Energy loss? Flow?

• Bottomonium Expectations– Cleaner probe of screening, deconfinement.– Regeneration?

• Not a big role for bottomonium• Open bottom: sbb ~ 1.34 – 1.84 mb.• Open charm: scc ~ 551 – 1400 mb.

– Co-mover absorption?• Expected to be small for bottomonium• Charmonium sabs ~ 3 – 4 mb.

• Bottmonium sabs ~ 1 mb. – Lin & Ko, PLB 503 104 (2001)



Upsilons in STAR

• Upsilons via Triggering, Calorimetry, Tracking, and matching of tracks to calorimeter towers.


Manuel Calderón de la Barca Sánchez10

The CMS Detector


• ϒ event in CMS.


in p+p 200 GeV in STAR


∫L dt = 7.9 ± 0.6 pb-1

N(total)= 67±22(stat.)

Phys. Rev. D

82 (2010) 12004

∫L dt = 19.7 pb-1

N(total)= 145±26(stat.)

2006 2009

STAR Preliminary


Comparison to NLO pQCD

• Comparison to NLO• STAR √s=200 GeV p+p ++→e+e- cross

section consistent with pQCD Color Evaporation Model (CEM)


CEM

: R. V

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Phys

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125,

200

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SM: J

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RD

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502,

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• Excellent resolution at midrapidity.

• Separation of 3 states.


in p+p 7 TeV in CMS

PRD 83, 112004 (2011)


vs √s, World Data


STAR √s=200 GeV and CMS √s=7 TeV p+p ++→e+e- cross section consistent with pQCD and world data trend

STAR Preliminary


in d+Au 200 GeV


∫L dt = 32.6 nb-1

N+DY+bb(total)= 172 ± 20(stat.)Signal has ~8σ significancepT reaches ~ 5 GeV/c

STAR Preliminary

Final results on RdAu coming soon. LHC pPb run in January/February.


in Au+Au 200 GeV


Raw yield of e+e- with |y|<0.5 = 197 ± 36

∫L dt ≈ 1400 µb-1


in Au+Au 200 GeV, Centrality


Peripheral Central

STAR Preliminary

STAR Preliminary

STAR Preliminary


Bottomonia at 2.76 TeV: 2010 datapp PbPbPRL 107 (2011) 052302



Bottomonia: 2011 datapp PbPb

Ratios not corrected for acceptance and efficiency



in Au+Au 200 GeV, RAA

9/18/12 HIT Seminar, Berkeley Lab M

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•Indications of Suppression of Upsilon(1S+2S+3S) getting stronger with centrality.•Reduced pp statistical uncertainties, increased statistics from 2009 data vs 2006 data.


(2S)/(1S) Double Ratio, CMS• Separated (2S) and (3S)

• Measured (2S) double ratio vs. centrality– no strong centrality dependence



(1S) Nuclear Modification Factor: RAA

• CMS PbPb at 2.76 TeV• In 2010: 7.28 µb−1

– (1S) RAA, 3 centrality bins– JHEP 1205 (2012) 063

• In 2011: 150 µb−1

– (1S) RAA, 7 centrality bins

– First results on (2S) RAA

• Clear suppression of (2S)– (1S) suppression

• Consistent with excited state suppression only

• ~50% feed down


CMS Preliminary,arXiv:1208.2826

http://arXiv.org/abs/1208.2826




Comparison: RHIC and LHC• STAR measured RAA of

(1S+2S+3S) combined– arXiv:1109.3891– min. bias value:

• CMS: separate RAA for(1S) and (2S)– can calculate min. bias RAA

of (1S+2S+3S):


CMS Preliminary,arXiv:1208.2826





ϒ RAA Comparison to models I• Incorporating lattice-based potentials,

including real and imaginary parts– A: Free energy

• Disfavored, not shown. – B: Internal energy

• Consistent with data vs. Npart

• Includes sequential melting and feed-down contributions– ~50% feed-down from cb.

• Dynamical expansion, variations in initial conditions (T0, η/S)– Data indicate:

• 428 < T0 < 442 MeV at RHIC• 552 < T0 < 580 MeV at LHC • for 3 > 4pη/S > 1 •M

. Stri

ckla

nd, P

RL

107,

132

301

(201

1).



ϒ RAA Comparison to models II

• Weak vs. Strong Binding– Narrower spectral functions for “Strong”

case– Ratios of correlators compared to Lattice:

favor “Strong” binding case• Kinetic Theory Model

– Rate Equation: dissociation + regeneration– Fireball model: T evolution. T ~ 300 MeV


StrongBindingWeakBinding


ϒ RAA Comparison to models II

• Comparison to data for “Strong” binding:– Mostly consistent with data– Little regeneration: Final result ~ Primordial suppression– Large uncertainty in nuclear absorption. Need dAu, pPb.


Eur. Phys. J. A (2012) 48: 72


ϒ RAA pT and y dependence

• Indications that suppression is largest at low pT. and mid rapidity. – Need more statistics for firmer conclusions.



The bottom line...• STAR and CMS:

– suppression vs. Npart.– RAA consistent with suppression of feed

down from excited states only (~50%)• CMS: First measurement of

(2S) suppression– RAA((3S)) < 0.09 (95% C.L.)

• (1S) RAA consistent with suppression of feed down from excited states only (~50%)– Need more pp statistics to pin down

lower-pT double ratio– Pinning down the medium properties.

• Cold nuclear matter:– coming soon!


Upsilon Production in Heavy Ions with STAR and CMS

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