February 10, 2011WWND: Winter Park, Colorado1 Upsilon Production and Upsilon + Hadron Correlations Matthew Cervantes for the STAR Collaboration Texas A&M University, Cyclotron Institute

February 10, 2011WWND: Winter Park, Colorado2 Physics Motivation * Study quarkonium suppression as a signature of QGP * Study the prompt production mechanism of heavy quarkonium Experiment * Accelerator: Relativistic Heavy Ion Collider (RHIC) * Detector: Solenoidal Tracker at RHIC (STAR) * STAR Upsilon trigger Upsilon * STAR Upsilon results * Upsilon + Hadron correlation Summary and Outlook Outline

February 10, 2011WWND: Winter Park, Colorado3 QGP and Heavy Quarkonia In a QGP the high energy density of the medium “deconfines” the J/  and  bound states. Deconfinement could lead to suppression of measured J/  and  yields in data. At RHIC, J/  may be regenerated (i.e. “regeneration” of cc) At RHIC, the collision energy is NOT high enough to allow copious production of bottom anti-bottom quarks.  is not expected to undergo regeneration (  bb <<  cc ). Measurements of J/  and  at STAR will help us understand the properties of the QGP. Establish base line measurements in p+p collisions ( e.g. base line for the melting of the  (1S, 2S, 3S) states in a QGP). Collisions in p+p can also be used to study the prompt production mechanism of heavy quarkonium. - -

February 10, 2011WWND: Winter Park, Colorado4 STAR data (Cu+Cu) of J/  at high-p T shows a lack of suppression. May indicate that J/  cannot exist in a colored state on a long enough timescale to be affected by the medium. (STAR Collaboration, Phys. Rev. C 80, (R) (2009)) Historically, not fully described by models, the Color Singlet Model (CSM) and the Color Octet Model (COM). Prompt production of Heavy Quarkonium CSM: Historically the calculations under-predicted the production cross section, but recent development with higher-order corrections (Lansberg J.P., arXiv: v1) can describe data better. COM: Success in explaining the p T spectra of quarkonia. Polarization prediction disagrees with experimental data. (e.g CDF Collaboration, Phys. Rev. Lett. 99 (2007) ) J/   (2S) Looking for new ways to study the prompt production mechanism of heavy quarkonium at STAR experiment. J/  is the only hadron that does not exibit high-pT suppression at RHIC. Lack of J/  suppression at high-pT suggests production is not dominated via a color channel.

February 10, 2011WWND: Winter Park, Colorado5 STAR Circumference (3.834 km) Species (pp, dAu, CuCu, AuAu) Energy (200, 500) GeV

February 10, 2011WWND: Winter Park, Colorado6 Large geometrical acceptance (-1 <  < 1 and  = 2  increased ability to study heavier (larger opening angle) vector mesons such as   e + e - STAR Detector for  measurement Time Projection Chamber (TPC) Acceptance: |  | < 1.4, 0 <  < 2  Tracking => momentum e ID: ionization energy loss dE/dx Barrel Electromagnetic Calorimeter (BEMC) Acceptance: |  | < 1, 0 <  < 2  e ID : p/E High-energy tower trigger Good efficiency => essential for luminosity limited measurement

February 10, 2011WWND: Winter Park, Colorado7 charged tracks STAR  trigger: BEMC L0+L2 L0 (hardware) – High energy tower E T > 4.3 GeV L2 (software) – High energy tower cluster pair E 1 > 4.5 and E 2 > 3.0 GeV – Loose cut on cos( θ) θ is the 3D opening angle – Cut on M ee = √[ 2E 1 E 2 (1-cos( θ)) ] Large acceptance BEMC L0+L2 trigger: Great di-electron trigger for luminosity limited measurements e+e+ e-e- Event Display: One d+Au 200 GeV  event as seen by the TPC in STAR

February 10, 2011WWND: Winter Park, Colorado8 Upsilon invariant mass: p+p (2006) PhysRevD

February 10, 2011WWND: Winter Park, Colorado9 STAR  p+p cross section theory/world data * STAR data point agrees with CEM at NLO (Phys. Rept. 462, 125 (2008)) * CSM underestimates STAR data by 2  (PRD 81, (2010)) * STAR data consistent with world data trend

February 10, 2011WWND: Winter Park, Colorado10 Upsilon invariant mass: d+Au (2008) Signal + Background  unlike-sign electron pairs Background  like-sign electron pairs  (1S+2S+3S) total yield: integrated from 7 to 11 GeV from background-subtracted m ee distribution – Raw Yield: 172 +/- 20 (stat.) – Strong signal (8 σ significance) Nucl.Phys. A830: 235c-238c (2009) H. Liu, QM 2009 No inner silicon detectors (SVT + SSD), reduced material in 2008 Integrated luminosity of 32 nb -1 ~ 12.5 pb -1 (p+p equivalent)

February 10, 2011WWND: Winter Park, Colorado11 Nuclear modification factor

February 10, 2011WWND: Winter Park, Colorado12  signal region: Mass window of 8.0 to 10.5 (11.5) GeV used in making the association of Upsilon candidates to hadrons. Upsilon invariant mass : p+p (2009) p+p 2009  (2S+3S)  (1S) ~ 9.46 GeV/c 2  (2S) ~ GeV/c 2  (3S) ~ GeV/c 2 Relative to 2006 p+p: * Less material budget * Integrated luminosity ~ 3x higher Relative to 2006 p+p: * Increased luminosity provides smaller error in the baseline S/B region higher than the 2006 p+p measurement: (S/B) ~ 5.76

February 10, 2011WWND: Winter Park, Colorado13 - The prompt quarkonium production mechanism in hadronic collisions include direct production via gluon fusion and CSM and COM transitions. - Multiple soft gluon emission expected with an  during the prompt production in COM. CSMCOM Associated Hadronic Activity Possible indication of prompt production via COM: an increase in the hadronic activity found in the vicinity of a promptly produced .

February 10, 2011WWND: Winter Park, Colorado14 Hadronic activity directly around the heavy quarkonium has been suggested as an experimental observable to measure the radiation emitted off the colored heavy quark pair during production. (Kraan, A. C., arXiv: v1 [hep-ex] 19 Jul 2008) Upsilon + Hadron Correlations * Sum of the hadronic p T within defined radius (R) of the  was previous method by A.C. Kraan: R = sqrt [(  ) 2 + (  ) 2 ] * Observation of this effect in simulation (PYTHIA). * We search for the increase in hadronic activity coming from the radiated gluons using the similar but alternative method of “azimuthal correlations”.  – correlation measurement LHC-like energies

February 10, 2011WWND: Winter Park, Colorado15 Physics Goal: Investigate prompt production mechanism by looking for an increase in the hadronic activity on the  near- side peak. * Gluon emission on near-side indicative of COM? STAR detector configuration for d+Au (2008) and p+p (2009) provides an almost background-free Upsilon. High S/B provides a clean opportunity to perform the Azimuthal correlation. Analysis: Run 8 d+Au 200 GeV collisions (~ 32 nb -1 integ. lum.) Analysis: Run 9 p+p 200 GeV collisions (~ 20 pb -1 integ. lum.)  + h correlation: physics goal

February 10, 2011WWND: Winter Park, Colorado16 Run 8 d+Au data (left) Run 9 p+p data (right) In d+Au data, correlation is not significant relative to the underlying-event. In p+p data, PYTHIA has a similar underlying-event. *RAW:  - correlation is not corrected for efficiency and acceptance.  - correlation (*RAW): Data vs. PYTHIA

February 10, 2011WWND: Winter Park, Colorado17 STAR Upsilon results: p+p at √ s=200 GeV: d+Au at √ s=200 GeV: p+p at √ s=200 GeV (2009 integrated luminosity ~20 pb -1 ): Heavy Quarkonium prompt production mechanism: *  + h correlation being studied as a way to investigate heavy prompt production *  spin-alignment studies also being studied in parallel with the  + h correlation Summary and Outlook B ee ×(dσ/dy) ϒ + ϒ ’+ ϒ ” y=0 = 114± pb (σ DY +σ bb ) |y|<0.5,8<m<7 GeV/c2 = 38±24 pb B ee ×(dσ/dy) ϒ + ϒ ’+ ϒ ” y=0 = 35±4(stat)±5(syst)nb R dAu = 0.78±0.28(stat)±0.20(syst) ** Reduced material ** Reduced uncertainty for R dAu ** Possible separation of ϒ states

February 10, 2011WWND: Winter Park, Colorado18 Summary and Outlook (cont.) A large area of muon telescope detector (MTD) at mid-rapidity, allows for the detection of: 1) di-muon pairs from QGP thermal radiation, quarkonia, light vector mesons, possible correlations of quarks and gluons as resonances in QGP, and Drell-Yan production 2) single muons from the semi- leptonic decays of heavy flavor hadrons 3) advantages over electrons: no  conversion, much less Dalitz decay contribution, less affected by radiative losses in the detector materials, trigger capability in Au+Au 4) trigger capability for low to high-p T J/  in central Au+Au collsions, excellent mass resolution, separate different upsilon states e-muon correlation to distinguish heavy flavor production from initial lepton pair production STAR-MTD Physics Motivation The prototype of MTD works at STAR from Run 7 to Run 10: The results published are at L. Ruan et al., Journal of Physics G: Nucl. Part. Phys. 36 (2009)095001; ; Y. Sun et al., NIMA 593 (2008) 430.

February 10, 2011WWND: Winter Park, Colorado19 Backup…

February 10, 2011WWND: Winter Park, Colorado20  is the angle between the direction of the e + momentum, measured in the  ’s rest frame with respect to the  ’s direction of motion, i.e. the polarization axis. Upsilon Spin-Alignment i.e. boost the  to its rest frame, then boost e + and e - into the  rest frame, and then measure  (e + direction w.r.t.  direction of motion)  = (  T - 2  L )/(  T + 2  L ) ‏ e    e   = -1, 0, +1 reflects longitudinal, zero, or transverse polarization.  = 1  = 0  =  cos 2  Parameterize the measurement to quantify the polarization.

February 10, 2011WWND: Winter Park, Colorado21 - Spin-alignment (“polarization”) of the  during the prompt production for CSM vs. COM. CSM: COM: Prompt production: Observable II Octet quarkonia inherits the transverse polarization of the gluon. No strong correlation between the initial gluon polarization and final state. J/   (2S) ‏ J/   (2S) ‏

February 10, 2011WWND: Winter Park, Colorado22 Upsilon Spin-Alignment (p T > 0 GeV/c) Corrections from embedding needed before the fit can be performed and anything about the polarization value can be stated. p+p 2009  = 1  = 0  =  cos 2 