Heavy flavor measurements at RHIC energies … present and future … Alexandre Suaide University of São Paulo – Brazil

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Overview Motivation  What keeps us going Current measurements  We are only in the beginning of our journey… The future  Wishes, dreams and perspectives…

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Motivation – the original thoughts  Heavy quarks are ideal probes for medium created at RHIC  Two ways of doing that Quarkonium investigation  Deconfinement  Medium thermometer Open heavy flavor  Production mechanisms  thermalization  Interaction with the medium  tomography B. Mueller, nucl-th/ D mesons,  ’, 

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Production mechanisms Charm quarks are believed to be produced at early stage by initial gluon fusions.  (M. Gyulassy & Z. Lin, PRC 51 (1995) 2177)  Sensitive to initial gluon distribution  Nuclear and medium effects in the initial state

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Baseline – production in p+p collisions M. Cacciari et al., PRL 95:122001,2005 Heavy Quark production is a “hard” process pQCD Calculations on NLO  (e.g. R. Vogt et al. hep- ph/ )  depend on: Quark mass m c, m b Factorization scale  F (typically  F = m T or 2m T ) Renormalization scale  R (typically  R =  F ) Parton density functions (PDF) Fragmentation functions (FF) – plays important role Fixed-Order plus Next-to- Leading-Log (FONLL)  designed to cure large logs for p T >> m q where mass is not relevant

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Melting quarkonia states Charmonia: J/ ,  ’,  c Bottomonia:  (1S),  (2S),  (3S) Original idea by Matsui and Satz  Color screening  Suppression depends on T/T c and binding energy T diss (  ’) < T diss (  (3S)) < T diss (J/  )  T diss (  (2S)) < T diss (  (1S)) But life is not that simple  Need to understand many different aspects E binding (GeV) J/  0.64 ’’ 0.05 cc 0.2  (1S) 1.1  (2S) 0.54  (3S) 0.31

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Quarkonia in p+p and p+A  Baseline p + p  production baseline d + A  cold matter effects (absorption, shadowing)  p + p Color Evaporation Model (CEM)  Quarkonium production treated as fraction of all  QQ pairs below  HH threshold CEM taken to NLO (Gavai et al., G. Schuler and R.Vogt) Parameters adjusted to existing data Direct production ratio J/  0.62 ’’ 0.14  c  c  (1S) 0.52  (2S) 0.33  (3S) 0.20 J/  +  ’+  ’’ hep-ph/

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL,  Nuclear Absorption Breakup of quarkonia in the final state Depends if produced as color singlet or octet  Shadowing Modification of PDFs in the nucleus w.r.t. free nucleon y distributions are more sensitive R. Vogt, RHIC-II Science Workshop Quarkonia in p+A

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Quarkonia – Effects in A + A  Feed down: Large from  c states (30-40% ?) Not well measured in hadronic collisions Unknown at RHIC energies  Other sources of quarkonia production Statistical coalescense (thermal production)  too small at RHIC – larger at LHC ? Dynamic coalescence  coalescence:  c+c  J/   recombination: J/  c+c  J/    narrower y and softer p T distributions Quenching at high-p T Comover absorption  J/  +  (  )  DD (negligible for  )

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, What about open heavy flavors? Useful tool to probe the medium  Yield, spectra, correlations, jets… How do we do it?  Hadronic reconstruction Clean probe but difficult in high multiplicity environments  Semi-leptonic decays Easier but depends on ‘magic’ to disentangle flavors  These limitations are strong concerns when defining detectors upgrades

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Open Heavy Flavor – Energy Loss in Medium  In vacuum, gluon radiation suppressed at  < m Q /E Q “dead cone” effect implies lower energy loss (Dokshitzer- Kharzeev, ‘01) energy distribution  d  /d  of radiated gluons suppressed by angle-dependent factor  Collisional E-loss: Qg  Qg, Qq  Qq dE/dx  ln p - small?  Various models in the market light (M.Djordjevic PRL 94 (2004))

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Open Heavy Flavor – Elliptic Flow Van Hees & Rapp, PRC 71, : resonant heavy-light quark scattering via scalar, pseudoscalar, vector, and axial vector D-like-mesons  Observed large elliptic flow of light/s quark mesons at RHIC Strong evidence for thermalization  What about charm? Naïve kinematical argument: need m q /T ~ 7 times more collisions to thermalize v 2 of charm closely related to R AA V.Greco, C.M. Ko nucl-th/

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, RHIC results – charm cross section Use all possible signals  D mesons  Electrons  Muons Charm cross section is well constrained  A factor of 5 higher than FONLL calculations  Follow a N bin scale from p+p to A+A collisions Produced in the initial stages No room for thermal production  

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Heavy flavor energy loss at RHIC Use of non-photonic electron spectra as proxy for energy loss study  Shapes at high-p T agree with FONLL but need to scale up RAA plots show increasing suppression from peripheral to central Au+Au  First evidence of heavy quark EL  Seems to suggest elastic EL  Do not favor the relative charm and bottom from FONLL calculations

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, The RAA puzzle. NPE are highly suppressed in central Au+Au collisions  Charm alone seems to explain Where is bottom?  Need direct measurement of D’s via hadronic decays and B’s via J/  or displaced vertex!

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Do heavy quarks flow? Study of non-photonic single electrons (from semileptonic D decays) First hint of strong charm elliptic flow for p T <2 GeV/c Seems to decrease at higher-p T  Does the suppression of charm makes bottom evident in this region in Au+Au? Many issues  Statistics limited  Uncertainties due to photonic background  Large sys errors  Cannot deconvolute contributions from charm and bottom Need direct measurement of D mesons (via K  ) v 2 ? ?

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, RHIC Results – J/  Suppression  Study of J/   ee and  in Au+Au and Cu+Cu Yield is suppressed compared to that in p+p collisions Suppression is larger for more central collisions. Suppression beyond that of cold nuclear matter for most central collisions even if  abs ~ 3 mb. Cold matter effects under predict the suppression  Issues: Lack of statistics Only J/  measurement so far  Need more statistics and data on  ’,  c, and  states V. Ciancolo, PANIC’05

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, RHIC Results – J/  Suppression Recombination predicts narrow p T and rapidity distribution:   p T 2  vs. N collisions Predictions of recombination model match better.  R AA vs. Rapidity No significant change in rapidity shape compared to p+p result. Recombination compensates suppression? Issues:  Charm rapidity distributions at RHIC are open questions  Require more data on √s, A dependence Need more statistics, J/  A. Bickley, HP’06

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, RHIC results other quarkonia states J/  is not the only state but may be the easiest one PHENIX Upsilon signal PHENIX  ’ Hungry for statistics!

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, The show must go on… First RHIC results are interesting and challenging  Why x-section is too high, compared to FONLL?  Charm and bottom relative production. Where bottom starts dominating?  Why so much suppression at high-pT?  Do heavy flavors flow?  Quarkonia is in the first steps Suppression vs. recombination? Feed down issues…

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Quarkonia – Goals and Requirements Physics MotivationProbesStudiesRequirements Baseline J/ ,  ’,  (1S),  (2S),  (3S) through  and ee decay channels Rapidity y(x F ) and p T spectra in AA, pA, pp as a function of A, √s High luminosity and acceptance. High resolution to resolve  states Deconfinement & Initial Temperature J/ ,  ’,  (1S),  (2S),  (3S) Melting patterns of quarkonia states Extract suppression mechanism taking into account: feed down, nuclear absorption, and recombination Properties of the medium High-p T J/  R AA : Dissociation  Quenching High luminosity Thermalization &Transport properties of the Medium J/  J/  flow (v 2 ) as a function of A, √s Recombination: y and  p T 2  High luminosity to obtain good statistics in short time (A, √s scans)

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Quarkonia – Goals and Requirements TopicStudiesRequirements Nuclear effects shadowing absorption Quarkonia in pp, pA: x 2, x F dependence A dependence rapidity distributions over wide range Large y coverage Forward coverage to high x F Suppression vs. Recombination charm production d  /dp T dy v 2 of J/  p T dependence of suppression High resolution vertex detectors Contribution from feed down Measure  c at least in pp and pA Photon detection at mid and forward rapidity, high luminosity, good energy & momentum resolution to minimize background Quarkonium production pA:  c / J/  A-dependence J/  polarization (?) As above Large acceptance for cos  *

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Open Heavy Flavor – Goals and Requirements Physics MotivationProbesStudiesRequirements BaselineD/B mesons, non- photonic electrons Rapidity y(x F ) and p T spectra in AA, pA as a function of A, √s High Luminosity High resolution vertex detectors (c  (D) ~  m) High-p T PID (D  K  ) Thermalization, Transport properties of the medium D mesons, B? non-photonic electrons (D+B) Elliptic flow v 2 p T spectra as above Properties of the medium Initial conditions D, B (B  J/  + X) mesons, non- photonic electrons R AA (p T ), R CP of D, B as a function of p T for various √s as above Properties of the medium Heavy Flavor Production D mesons, non- photonic electrons Correlations: charm-charm charm-hadron J/  -hadron HIGH luminosity (eff 2 !) Large coverage Trigger ?

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, How to do it? RHIC-II: increased luminosity (RHIC-II ≈ 40 × RHIC)  collision diamond s = 20 cm at RHIC and s = 10 cm at RHIC II gain in usable luminosity is larger than “nominal” increase PHENIX & STAR: more powerful upgraded detectors crucial to the Heavy Flavor physics program - completed in mid/near term ~5 years.  STAR: DAQ upgrade increases rate to 1 KHz, triggered data has ~ 0 dead time. Silicon tracking upgrade for heavy flavor, jet physics, spin physics. Barrel TOF for hadron PID, heavy flavor decay electron PID. EMCAL + TOF J/y trigger useful in Au+Au collisions. Forward Meson Detector  PHENIX: Silicon tracker for heavy flavor, jet physics, spin physics. Forward muon trigger for high rate pp + improved pattern recognition. Nose cone calorimeter for heavy flavor measurements. Aerogel + new MRP TOF detectors for hadron PID. Hadron-blind detector for light vector meson e+e- measurements.

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, What can we do with these upgrades? Can STAR and PHENIX handle them all? Supposing a 12 weeks of RHIC II running with upgrades. L sampled ~ 238 pb -1

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Acceptance is a big thing. STAR and PHENIX have limited reco power

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Acceptance is a big thing. Look at CDF, for example. Even with high-acceptance, some measurements are very difficult  Zillions of J/  but almost no  c

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, What can we do with these upgrades? Can STAR and PHENIX handle them all? NO! What if we have a large acceptance detector? Lets say, |  |<3 Supposing a 12 weeks of RHIC II running with upgrades. L sampled ~ 238 pb -1

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, Final comments… Heavy flavor physics is an important tool to understand HI physics at RHIC  Deconfinement  Thermalization  Transport properties of the medium Heavy Flavor Physics at RHIC is just at the beginning  New physics? Need accelerator and detector improvements to deeper investigate  RHIC-II luminosity and higher detector acceptance/event rates  Need a new detector, with high acceptance and high event rate capability, whatever that detector is…  Still challenging. Need very large datasets and low background measurements

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, EXTRAS …

Alexandre Suaide University of São Paulo, Brazil Wokshop on Future Prospects in QCD at High Eenergy, BNL, How LHC fits in this picture?