Jet Reconstruction in d+AuCollisions at RHIC-PHENIX

Nathan GrauColumbia University, Nevis Laboratoriesfor the PHENIX Collaboration

10/17/2009Joint APS/JPS DNP

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Outline

Multitude of measurements with jets in d+Au Focus first on Di-jet correlations

Measuring jets in d+Au collisions withPHENIX

Di-jet Δφ correlations Future outlook

10/17/2009Joint APS/JPS DNP

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Physics With Jets in d+Au: Cronin

Anti-shadowing of nPDF ==> multiplescattering

Multiple scattering would tend to broaden theback-to-back di-jet correlations

Important constraint on jet quenching in A+Asince any multiple scattering energy lossmodel must describe both the cold nuclearand hot nuclear matter effects.

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Physics With Jets in d+Au: Cronin No conclusive

evidence of di-jet broadeningat RHIC fromtwo-particlecorrelations

Di-jet resultsfrom STARmay indicateotherwise.Circle - π+/--h

Cross - π0-h

PHENIX PRC 73 (2006) 054903

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Jets in PHENIX Combine

DC-PC tracks with pT> 450 MeV

EMCal clusters withpT > 400 MeV

Reject electronconversions

Remove clustersassociated withtracks

Consider jets with Raw pT > 5 GeV # constituents > 2

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Anti-kT Jet Algorithm

Anti-kT recombination algorithm Collinear and infrared safe algorithm Combines nearest, hardest particles first and

works outwards from that jet Opposite approach to kT algorithm combination

makes jets essentially conical with radius R. Use FastJet package anti-kT algorithm with

R=0.3

Cacciari, Salam, and Soyez

10/17/2009Joint APS/JPS DNP

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Anti-kT Jet Algorithm

Same event run with kT and anti-kT algorithms They find the same jets, but the shapes are different

p+p eventG. Soyez RHIC-AGS Users’ Meeting

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Jets in PHENIX

η

φ

Raw pT: 13.5 GeV3 clusters2 tracks

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Di-jets in PHENIX

η

φ

Raw pT: 7.47 GeV2 clusters2 tracks

Raw pT: 9.63 GeV2 clusters2 tracks

Δφ = 3.36 rad

10/17/2009Joint APS/JPS DNP

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Δφ Di-jet Correlations Correlate the

highest pT jetsin the event

Define leadingjet withhighest rawreconstructedpT

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Δφ Di-jet Correlations

Back-to-back correlations

Correlate thehighest pT jetsin the event

Define leadingjet withhighest rawreconstructedpT

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Δφ Di-jet Correlations

Split jetsBack-to-back correlations

Correlate thehighest pT jetsin the event

Define leadingjet withhighest rawreconstructedpT

10/17/2009Joint APS/JPS DNP

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Centrality Dependence

0-20% 20-40%

40-88%

Access tolength-dependence ofmultiplescattering

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Looking Forward

First measurements of fully reconstructed jets ind+Au using the PHENIX detector. Δφ correlations of di-jet signal is seen

A wealth of physics awaits Dijet broadening Data to constrain nPDFs Fragmentation photons Heavy flavor jets Correlations between forward/backward particles and mid-

rapidity jets Etc.

10/17/2009Joint APS/JPS DNP

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Backup

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Physics With Jets in d+Au: nPDFs Jets can reach to higher x and Q2 than single particle observables? Jets possibly allow constraint of EMC region at RHIC

Constrain high-x == constrain low-x because of momentumconservation

JHEP04(2009)065

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Physics With Jets in d+Au: nPDFs Centrality-dependence == measure of impact parameter-

dependence of nPDFs. These are critical inputs not only at RHIC but at the LHC.

JHEP04(2009)065

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Higher Leading Jet pT Correlations

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Higher Leading Jet pT Correlations