Latest Charmonium Results from the PHENIX Experiment at RHIC

Alexandre Lebedev (Iowa State University)For the PHENIX Collaboration

Lake Louise Winter Institute - February 23, 2013

02/23/2013 Alexandre Lebedev (ISU) 2

Outline

J/y in Au+Au collisions at = 39 and 62 GeV J/y in Cu+Au collisions at = 200 GeV

J/y in d+Au collisions vs pT, rapidity, and centrality

y’ and cC in d+Au collisions

02/23/2013 Alexandre Lebedev (ISU) 3

Introduction…color screening will prevent ccbinding in the deconfined region. - Matsui and Satz, 1986

Charmonium is an excellent tool for measuringscreening length and temperature in QGP…

… but only if we know all our references.

Many competing processes in AA collisions:color screening, initial state effects, regeneration,cold nuclear matter effects, feed-down…

… need measurements for different energies, colliding species, quarkonium states, pT and rapiditydependence…

02/23/2013 Alexandre Lebedev (ISU) 4

Nuclear Modification Factor RAA

Yield in nucleus-nucleus collisions divided by p+p yields and scaled by the appropriate number of binary collisions NCOLL, which is calculated using Glauber model.

Centrality of collision is described by number of participant nucleonsNPART

Impact parameter [fm]

02/23/2013 Alexandre Lebedev (ISU) 5

The PHENIX Experiment

Central Arms (electrons)|h| < 0.35 Df = 2 × p/2P > 0.2 GeV

Muon Arms1.2 < |h| < 2.2 Df = 2pP > 2 GeV

Charmonium states are measured via di-lepton decays

02/23/2013 Alexandre Lebedev (ISU) 6

J/y at Low(er) Energies

Surprisingly, similar suppression is observed at 200, 62 and 39 GeVNo PHENIX baseline in p+pat 39 and 62GeV, use extrapolations from CERN and Fermilab experiments.

A.Adare et. al., Phys. Rev. C 86, 064901 (2012)

02/23/2013 Alexandre Lebedev (ISU) 7

One Possible ExplanationRegeneration compensates for suppression in QGP.Calculations by X. Zhao and R. Rapp, Phys. Rev. C 82, 064905 (2010)

But cold nuclearmatter effectsshould be different!

02/23/2013 Alexandre Lebedev (ISU) 8

Asymmetric Collisions (Cu+Au)

Suppression in Au-going direction same as in AuAu and CuCu,But stronger in Cu-going direction.Partially explained by CNM (shadowing and nuclear breakup).

02/23/2013 Alexandre Lebedev (ISU) 9

Lots of New Results in d+Au Collisions

J/y as a function of centrality, rapidity and pT (new)

y’ at mid-rapidity as a function of centrality (new)

cC at mid-rapidity (new)

02/23/2013 Alexandre Lebedev (ISU) 10

J/y RdAu vs pT

Phys. Rev. D 86, 092006 (2012)Minimum bias results.

Similar suppression at mid-rapidityand forward (d-going) rapidity.Suppression below ≈ 4 GeV.RdAu ≈ 1 above 4 GeV.

Different RdAu pT dependence atforward (Au-going) rapidity.Enhancement above ≈ 1 GeV.

No clear explanation from theory for the forward result.

02/23/2013 Alexandre Lebedev (ISU) 11

J/y RdAu Centrality DependenceIntegrated over pT J/y are suppressedat all centralities and rapidities.

Shadowing plus nuclear breakupreproduces well minimum biasresults (not shown), but not rapidity and centrality dependence together.

Centrality dependence at forward rapidity (Au-going direction)implies non-linear dependence on nuclear thickness.

Forward rapidity described well by CGC

Impact parameter is poorly definedin d+Au

Phys. Rev. Lett. 107 (2011) 142301

02/23/2013 Alexandre Lebedev (ISU) 12

y’ in d+AuStronger suppression for y’ than for J/y in most central collisions.

02/23/2013 Alexandre Lebedev (ISU) 13

cC in d+Au

Charmonium RdAu seems to depend on binding energy.Better cC measurementis needed though.

02/23/2013 Alexandre Lebedev (ISU) 14

ConclusionsJ/y RAA is similar at 200, 62, and 39 GeV.

In Cu+Au J/y suppression is stronger in Cu-going direction.

PT dependence of J/y RdAu at negative (Au-going) rapidityis different from mid and positive rapidity.

J/y RdAu centrality dependence is “non-linear” at positive(d-going) rapidity.

Large suppression of y’ in central d+Au collisions.

02/23/2013 Alexandre Lebedev (ISU) 15

Backup Slides

02/23/2013 Alexandre Lebedev (ISU) 16

CNM in Cu+Au

02/23/2013 Alexandre Lebedev (ISU) 17

J/y RdAu Minimum Bias

02/23/2013 Alexandre Lebedev (ISU) 18

y’ RdAu Comparison to Lower EnergiesIf charmonium formation time is shorter than the time spent Traversing the nucleus, larger suppression will be observed.Does not hold at RHIC energy!

02/23/2013 Alexandre Lebedev (ISU) 19

J/y Flow

02/23/2013 Alexandre Lebedev (ISU) 20

J/y Transverse Single Spin Asymmetry