Quarkonium Quarkonium progress in progress in

STARSTAR

Manuel Calderón de la Barca SánchezUC DavisHeavy Flavor Working Group, STAR;

XXII Winter Workshop on Nuclear DynamicsLa Jolla, CA 15/March/2006

15/March/2006 Manuel Calderón de la Barca2

OutlineOutline

MotivationMotivation STAR capabilitiesSTAR capabilities

TriggerTrigger ee++ee--

Triggered samples so farTriggered samples so far Run IV Au+Au: Run IV Au+Au: Run V p+p: J/Run V p+p: J/

Prospects for Run VI and beyond. Prospects for Run VI and beyond.

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Why are we interested in Why are we interested in quarkonia?quarkonia?

Charmonium Charmonium suppression: suppression: longstanding QGP longstanding QGP signaturesignature Original idea: Original idea:

screening.screening. lattice lattice

calculations calculations confirm screening confirm screening effectseffectsNucl.Phys.Proc.SupNucl.Phys.Proc.Sup

pl.129:560-pl.129:560-562,2004562,2004

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

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Quarkonium at SPSQuarkonium at SPS

NA50 data: NA50 data: “Anomalous” “Anomalous” suppression.suppression.

NA60 data: NA60 data: Confirmation (with Confirmation (with smaller errors)smaller errors)

PHENIX at RHIC, PHENIX at RHIC, see Wei Xie next…see Wei Xie next…

Theory challengeTheory challenge Description of SPS Description of SPS

and RHIC dataand RHIC data

Satz, Digal, Fortunato (percolation)Rapp, Grandchamp, Brown (diss. and recomb.)Capella, Ferreiro (comovers)

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Binding Energy & TBinding Energy & TDD

StateState (2s)(2s) cc(1p)(1p) J/J/(1s)(1s)

EEbb (GeV) (GeV) 0.050.05 0.230.23 0.640.64

TTDD/T/TCC 0.1-0.20.1-0.2 0.740.74 1.11.1

StateState (3s)(3s) bb(2p)(2p) (2s)(2s) bb(2p)(2p) (1s)(1s)

EEbb (GeV) (GeV) 0.20.2 0.30.3 0.540.54 0.670.67 1.11.1

TTDD/T/TCC 0.750.75 0.830.83 1.11.1 1.131.13 2.312.31Digal, Petreczky, Satz; Phys.Rev.D64:094015,2001Using lattice free energy as potential.

Binding Energy & Sequential Suppression.

The premise: A full quarkonium spectroscopyfull quarkonium spectroscopy can help address the questionof deconfinement; ~ direct connection to first principles LQCD.Reality Check: Uncertainties in the calculations (~factor 2), free energy vs. internal energypotential models vs. spectral functionsGluons breaking up J/, recombination contribution?,

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Lessons learned the hard Lessons learned the hard wayway

To connect with theory, we need a To connect with theory, we need a good systematic programme:good systematic programme: p+p, Au+Au, vs. cent. vs. p+p, Au+Au, vs. cent. vs. √√s s Measure not just J/Measure not just J/..

Excited states are needed for feeddown.Excited states are needed for feeddown.Y states are a key, but Y states are a key, but

Small cross sectionSmall cross section Mass resolution?Mass resolution?

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What can STAR contribute? What can STAR contribute? STAR was not built for di-leptons, but…STAR was not built for di-leptons, but… Large acceptance at mid-rapidityLarge acceptance at mid-rapidity

|||<1 , 0<|<1 , 0<<2<2 Pair acceptance ~ single acceptancePair acceptance ~ single acceptance22

Electron ID-capabilities Electron ID-capabilities TPC dE/dxTPC dE/dx EMC E>1-2 GeV (full barrel in 2006)EMC E>1-2 GeV (full barrel in 2006) TOF p<2-3 GeV/c (only patch, full barrel in the future)TOF p<2-3 GeV/c (only patch, full barrel in the future)

Triggering capabilities on Barrel EMCTriggering capabilities on Barrel EMC Suitable for single electrons (proxy for open charm) Suitable for single electrons (proxy for open charm)

(see J. Harris’s talk tomorrow afternoon)(see J. Harris’s talk tomorrow afternoon) Suitable for di-electrons?Suitable for di-electrons?

J/J/ are rare, are rare, triggering where possibletriggering where possible

J/J/ in pp in pp in all systems (no signal without a trigger)in all systems (no signal without a trigger)

large dataset if triggering not possible: J/large dataset if triggering not possible: J/ in Au+Au in Au+Au

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Electron IDElectron ID

Combine Combine detectorsdetectors TPC dE/dx in a TPC dE/dx in a

limited regionlimited region Barrel EMC for Barrel EMC for

p>1 GeV/cp>1 GeV/c TPC+BEMCTPC+BEMC

1.5<p< 5 GeV, |p/E-1|<1

P.Djawotho

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Electron Efficiency and Electron Efficiency and PurityPurity

P. Djawotho

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J/J/ “Topology” Trigger: Level- “Topology” Trigger: Level-00

Fast, T Fast, T ≤≤11ss Divide Divide into 6 into 6

sectionssections Find a tower Find a tower

above a above a thresholdthreshold

Look in the 3 Look in the 3 opposite sections opposite sections in in

If another tower If another tower above threshold, above threshold, issue trigger.issue trigger.

Real Data, p

+p Run V

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J/J/ Software Trigger: Software Trigger: Level-2Level-2

Looking for eLooking for e++ee-- pair pair Approximate electron Approximate electron

daughters with tower daughters with tower clustercluster Use L0 tower cluster, Use L0 tower cluster,

combine with L2 clusterscombine with L2 clusters Energy, Position Energy, Position cos( cos())

Vertex from trigger Vertex from trigger detectors timingdetectors timing BBC Resolution ~ 6 cm in BBC Resolution ~ 6 cm in

Au+Au, but 30 cm in p+p.Au+Au, but 30 cm in p+p. Otherwise assume vtx at Otherwise assume vtx at

(0,0,0).(0,0,0). Make tower cluster pairs, Make tower cluster pairs,

neglecting mneglecting mee:: mm22

invinv 2E 2E11EE22(1-cos((1-cos(1212)))) Issue decision in T<500 Issue decision in T<500 s.s.

Real Data, p+p Run V

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Can it be used in Au+Au?Can it be used in Au+Au? High rejection only High rejection only

for for peripheralperipheral events.events.

Most signal in Most signal in centralcentral events. events.

98% of the yield is 98% of the yield is in top 60% central.in top 60% central.

There is no free There is no free lunch…lunch…

p+p: environment p+p: environment well matched for well matched for triggertrigger

Au+Au: must rely Au+Au: must rely on a large dataset.on a large dataset.

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Trigger: L0 + L2Trigger: L0 + L2 Advantage: Advantage: mass is large mass is large

Can use a simpler L0 triggerCan use a simpler L0 trigger Require one BEMC Require one BEMC

towerwith Etowerwith ETT>3.5 GeV>3.5 GeV Use similar L2 algorithmUse similar L2 algorithm Can trigger in p+p and also Can trigger in p+p and also

in central Au+Au!in central Au+Au! Rare triggers can go to Rare triggers can go to

“express stream” “express stream” processing.processing. Very quick turnaround time.Very quick turnaround time.

Disadvantage: production Disadvantage: production rate is tiny!rate is tiny! Expected less than 100 in Expected less than 100 in

the full Run IV Au+Au the full Run IV Au+Au dataset.dataset.

Reality, got only a few Reality, got only a few counts due to many counts due to many compounded effectscompounded effects

Smaller acceptanceSmaller acceptance Less running timeLess running time BEMC miscalibrationBEMC miscalibration Some detectors not ready Some detectors not ready

for L2 in Run IVfor L2 in Run IV

T. Kollegger

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J/J/ in Au+Au Run IV in Au+Au Run IV

No triggering is No triggering is possible, too much possible, too much background.background.

Search in the Au+Au Search in the Au+Au dataset of Run IVdataset of Run IV

Signal? Hints so far…Signal? Hints so far… Analysis using TPC Analysis using TPC

alonealoneEMC had smaller EMC had smaller

acceptanceacceptancep ~ 1.5 GeV/c, p ~ 1.5 GeV/c,

borderline for EMC PIDborderline for EMC PID

Dielectron Invariant Mass (GeV/c2)

STAR PreliminaryJ. González

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Trigger in Au+Au Run IVTrigger in Au+Au Run IV

L0: events with EL0: events with Etowertower > 3.5 GeV. > 3.5 GeV. L2: events with cluster pair masses m>7 GeV/cL2: events with cluster pair masses m>7 GeV/c22..

Trigger works!Trigger works!

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Trigger performance in Trigger performance in Au+Au Au+Au

Events sampled Events sampled per dayper day 4-20 M per day4-20 M per day

Variations due to Variations due to need to meet other need to meet other STAR goalsSTAR goals Half-field runningHalf-field running

Part of heavy-flavor Part of heavy-flavor progam: D* -> D+progam: D* -> D+

Additional triggers Additional triggers reducing reducing trigger trigger livetime. livetime.

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Analysis in Au+Au run IVAnalysis in Au+Au run IV

Sampled 34.2 Sampled 34.2 bb-1-1

More than 200 M More than 200 M minimum bias events minimum bias events scanned with Upsilon scanned with Upsilon trigger.trigger.

Comparison w/ offlineComparison w/ offline~50 M minimum bias ~50 M minimum bias

events.events. Small dataset processed Small dataset processed

Only 3 signal counts Only 3 signal counts (with no background (with no background counts) were observed.counts) were observed.

11stst STAR measurement STAR measurement where we are where we are Luminosity-limited in a Luminosity-limited in a big way.big way.

Half field running, no BEMC-basedtriggers.

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Analysis in Au+AuAnalysis in Au+Au Upper limit estimation:Upper limit estimation:

90% C.L. : signal < 4.9190% C.L. : signal < 4.91 B*dB*d/dy C.L. < 7.6 /dy C.L. < 7.6 bb

Acceptance increase Acceptance increase will helpwill help Factor ~ 4.Factor ~ 4.

T. Kollegger

+-+- ++++ ----

NNpairspairs 8.4<m< 10.7 8.4<m< 10.7 GeVGeV

22 00 00

NNpairspairs 10.7<m< 13.0 10.7<m< 13.0 GeVGeV

11 00 00

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Trigger performance in Trigger performance in Run VRun V

Online monitoring of trigger information.Online monitoring of trigger information. Extremely fast turnaround.Extremely fast turnaround. No need to wait for offline production to find if No need to wait for offline production to find if

trigger is behaving as expected.trigger is behaving as expected.

Energy (MeV) Invariant mass (MeV/c2)

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Sample from Run V, p+pSample from Run V, p+p

Collected 1.7 M Collected 1.7 M triggerstriggers

Simulation:Simulation: expected a sample of expected a sample of

60-70 J/60-70 J/’s in this test ’s in this test data set.data set.

Data:Data: Yield small, but Yield small, but

consistent with consistent with simulations.simulations.

Ready for Run VI!Ready for Run VI!

P. Djawotho

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Data and simulation Data and simulation comparisoncomparison

Width is consistent with our detector Width is consistent with our detector resolution.resolution.

Mass is slightly lower than expected Mass is slightly lower than expected (2(2))

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FutureFuture Run VI p+p:Run VI p+p:

Barrell EMC now fully installedBarrell EMC now fully installed |||<1, full azimuth|<1, full azimuth Increase by factor 4 over Run Increase by factor 4 over Run

IV di-electron acceptance.IV di-electron acceptance. L2 trigger has proved to workL2 trigger has proved to work

Will be heavily used in Run VI Will be heavily used in Run VI (jets, dijets)(jets, dijets)

Longer term upgradesLonger term upgrades Improve vertex knowledge at Improve vertex knowledge at

L0L0~1 cm resolution using ~1 cm resolution using

upgrade to pVPD used in TOFupgrade to pVPD used in TOF Additional PID capabilities by Additional PID capabilities by

full barrel TOF (2009)full barrel TOF (2009) TOF also allows a better TOF also allows a better

background rejection.background rejection. R&D on possible muon trigger R&D on possible muon trigger

in |h|<1, 60% azimuth in |h|<1, 60% azimuth