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RHIC and AGS Annual Users’ Meeting Heavy Flavor Workshop, June 2 nd 2009

Summary on SPS results on heavy quark measurements. Roberta Arnaldi - INFN Torino (Italy). Open charm measurement at SPS  NA50 and NA60 pA and AA results J/  production in pA collisions  new pA data @ 158 GeV (NA60)  definition of the new reference for AA collisions

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RHIC and AGS Annual Users’ Meeting Heavy Flavor Workshop, June 2 nd 2009

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  1. Summary on SPS results on heavy quark measurements Roberta Arnaldi - INFN Torino (Italy) Open charm measurement at SPS  NA50 and NA60 pA and AA results J/ production in pA collisions  new pA data @ 158 GeV (NA60)  definition of the new reference for AA collisions J/ suppression in AA collisions  update of the results based on the new reference curve RHIC and AGS Annual Users’ Meeting Heavy Flavor Workshop, June 2nd 2009

  2. Heavy Quarks at SPS LMR IMR HMR Heavy quark measurement at SPS energies: Intermediate Mass Region open charm production High Mass Region  charmonia production

  3. Open Charm at SPS Eur.Phys.C14(2000) 442 NA50Pb-Pb 158 A GeV/c<Npart> = 381 Data Prompt: 2.290.08 Charm: 1.160.16 Fit 2/NDF: 0.6 centralcollisions Fit range HELIOS3-NA38-NA50 p-A IMR described by DY and Open Charm Pb-Pb  yields exceed pA extrapolation NA60 In-In Mass spectrum similar to NA50 (DY+2*Charm extrapolated from pA) 1.120.17 Dimuon offsets wrt interaction vertex show that the excess is prompt  charm is not enhanced in A-A with respect to expectations Prompt

  4. Open Charm A dependence DD J/ EKS98 EPS08 Recent results from E866 seem to suggest strong nuclear effects on open charm M. Leitch – Trento Workshop, May 09 New NA60 pA results soon available. Open charm A-dependence may add further useful information also in the charmonium understanding E. Scomparin – Trento Workshop, May 09 E866/NuSea Preliminary  Preliminary studies point to an even stronger DD antishadowing with respect to J/  If DD has little final state interactions its  should be significantly larger than that of the J/ (initial state energy loss should be the same) xF

  5. Charmonia in pA and AA collisions Study of charmonium production/suppression in pA and AA collisions AA collisions • Color screening and charmonium suppression • > 20 year long history pA collisions • Production models (CSM, NRQCD, CEM, ....) • Initial/final state nuclear effects (shadowing, dissociation,...) • Reference for understanding dissociation in a hot medium

  6. Experimental landscape (Relatively) large amount of fixed-target data (SPS, FNAL, HERA) AA collisions NA38(M.C. Abreu et al., PLB449(1999)128) S-U 200 GeV/nucleon, 0<y<1 NA50(B. Alessandro et al., EPJC39 (2005)335) Pb-Pb 158 GeV/nucleon, 0<y<, pT<5 GeV NA60(R. Arnaldi et al., PRL99(2007) 132302) In-In 158 GeV/nucleon, 0<y<1, pT<5 GeV pA collisions HERAB (I. Abt et al., arXiv:0812.0734) p-Cu (Ti) 920 GeV,-0.34<xF<0.14,pT<5 GeV E866 (M. Leitch et al., PRL84(2000) 3256) p-Be,Fe,W 800 GeV,-0.10<xF<0.93,pT<4 GeV NA50 (B. Alessandro et al., EPJC48(2006) 329) p-Be,Al,Cu,Ag,W,Pb,400/450 GeV,-0.1<xF<0.1,pT<5 GeV NA3(J. Badier et al., ZPC20 (1983) 101) p-p p-Pt, 200 GeV, 0<xF<0.6, pT<5 GeV NA60 p-Be,Al,Cu,In,W,Pb,U 158/400 GeV,-0.1<xF<0.35,pT<3 GeV

  7. In-In Pb-Pb Experimental results before QM09 pA collisions Reference for the J/ suppression in AA (cold nuclear matter effects aka nuclear abs.) • tuned using pA at 400/450 GeV (NA50) absJ/ = 4.2±0.5mb, (J//DY)pp =57.5±0.8 (Glauber analysis) • extrapolated to AA assuming absJ/ (158 GeV) = absJ/ (400/450 GeV) AA collisions Observed suppression in AA exceeds nuclear absorption • Onset of the suppression at Npart 80 • Good overlap between Pb and In

  8. Cold nuclear matter effects I. Abt et al., arXiv:0812.0734 To understand the J/ dissociation in the hot matter created in AA collisions, cold nuclear matter effects have to be under control J/ production is studied in p-A collisions J/ absorption is parameterized through • E866 vs HERAB (similar √s)  agreement in the common xF range • E866/HERAB vs NA50   decreases when decreasing √s Strong xF dependence of   Satisfactory theoretical description still unavailable! (R. Vogt, Phys. Rev. C61(2000)035203, K.G.Boreskov A.B.Kaidalov JETP Lett. D77(2003)599)

  9. μ J/ μ p pA and AA collisions pA collisions Charmonium absorption in cold nuclear matter: difficult topic because many competing effects contribute • Final state: • cc dissociation in the medium, • final energy loss • Initial state: • shadowing, • parton energy loss, • intrinsic charm AA collisions Charmonium production in pA should provide the reference for AA data. Because of the  dependence onxF and energy the reference for the AA suppression must be obtained under the same kinematic/energy domain as the AA data NA60 has collected for the first time pA data at 158 GeV, i.e. the same energy as the AA collisions

  10. NA60 pA data NA60 has collected the following pA data: 158 GeV: no data available up to now 400 GeV: already investigated by NA50 (cross check)  3-day long data taking, largely motivated by the need of a reference sample taken in the same conditions of In-In (NA60) and Pb-Pb (NA50) data  useful to enlarge the  vs xF systematics 158 GeV •  bulk of the NA60 p-A data taking •  results released up to now • sub-sample with same exp. set-up used at 158 GeV • useful as a cross-check (same energy/kinematic domain • of the large statistics data sample collected by NA50) 400 GeV 0.28 < ycm < 0.78 (158 GeV) Kinematical window where acceptance is >0 for all targets • 3.2 < ylab < 3.7 -0.17 < ycm < 0.33 (400 GeV) • | cos CS | <0.5

  11. NJ/  2  103 DY J/, ’ DD New NA60 p-A results Comb.bck. p-Pb Not enough DY statistics to extract (as in NA50) B J//DY target by target Estimate of nuclear effects through relative cross sections: • all targets simultaneously on the beam • beam luminosity factors Niinc cancel out (apart from a small beam attenuation factor)  no systematic errors • each target sees the vertex spectrometer under a (slightly) different angle • acceptance and reconstruction efficiencies do not completely cancel out Efficiency map (4th plane, sensor 0) These quantities, and their time evolution, are computed for each target separately

  12. pA: new NA60 results 158 GeV 400 GeV A-dependence fitted using the Glauber model Shadowing neglected, as usual (but not correct!) at fixed target absJ/ (158 GeV) = 7.6 ± 0.7 ± 0.6 mb absJ/ (400 GeV) = 4.3 ± 0.8 ± 0.6 mb Very good agreement with the NA50 value • (158 GeV) = 0.882 ± 0.009 ± 0.008  (400 GeV) = 0.927 ± 0.013 ± 0.009 Using

  13. Comparison between experiments:  vs xF Recent results on  vs xF from HERA-B, together with older data from NA50, E866 In the region close to xF=0, increase of  with √s • NA60 400 GeV • very good agreement with NA50 NA60 158 GeV:  smaller , hints of a decrease towards high xF ? Systematic error on  for the new NA60 points ~0.01

  14. Comparison between experiments:  vs x1,2  pattern vs x1 at lower energies resembles HERA-B+E866 but systematically lower Shadowing effects scale with x2 clearly other effects are present

  15. Comparison between experiments: abs vs xF absJ/ calculated from cross section ratios for HERA-B, E866,NA3 Increase of absJ/ with √s, but NA3 shows values closer to the high energy experiments (E866/HERA-B) • Interpretation of results not easy • many competing effects affect J/ production/propagation in nuclei • (shadowing, final state absorption, energy loss,....) need to disentangle the different contributions (E. Scomparin, Trento workshop 2009) First attempts of a systematic study of abs dependencies: (most recent C. Lourenco, R. Vogt and H.Woehri, JHEP 0902:014,2009, see also F. Arleo and V.N. Tram, EPJC55(2008)449 )  Hermine’s talk

  16. 158 GeV free proton pdf EKS98 Antishadowing correction 158 GeV free proton pdf Size of shadowing-related effects may be large and should be taken into account when comparing results at different energies We have evaluated (and corrected for) the (anti)shadowing effect expected for our data points, within the EKS98 and EPS08 scheme without antishadowing: 7.6± 0.7± 0.6 mb absJ/ (158 GeV) with antishadowing (EKS) = 9.3± 0.7± 0.7 mb Significantly higher than the “effective” values

  17. Reference for AA data The cold nuclear matter reference used up to now by NA50/NA60 was based on the following assumptions: New pA results collected at 158 GeV, in the same kinematic and energy range as AA data • absis energy independent •  but this may not be the case • all cold nuclear matter effects can be described with an “effective” abs •  but, since these effects depend on energy/kinematic domain, it is difficult to compare results e.g. between SPS and RHIC First attempts to disentangle initial (antishadowing/energy loss) and final state effects (absorption in nuclear matter) Proj. and target antishadowing taken into account in the reference determination • pA nuclear effects can be extrapolated to AA •  but in AA collisions gluon antishadowing affects both projectile and target New pA analysis should provide a more appropriate reference

  18. In-In 158 GeV (NA60) Pb-Pb 158 GeV (NA50) Results with old and new reference published results B. Alessandro et al., EPJC39 (2005) 335 R. Arnaldi et al., PRL99 (2007) 132302 new reference absJ/ (158 GeV) > absJ/ (400 GeV) smaller anomalous suppression expected with respect to previous results Anomalous suppression in In-In is quite small ( 10%) Anomalous suppression in Pb-Pb up to 30% In-In analysis based on another centrality estimator (number of tracks) ongoing, to check the observed pattern

  19. Antishadowing contribution In AA collisions the initial state effects (shadowing) affect not only the target, but also the projectile  to be included in the extrapolation of the reference from pA to AA Even in absence of anomalous suppression, the use of the standard reference (no shadowing) induces a 5-10% suppression signal  sizeable effect Using the new reference (shadowing in the projectile and target) • Central Pb-Pb: still anomalously suppressed • In-In: almost no anomalous suppression?

  20. Comparison with new PHENIX results Measured/Expected SPS results are compared with AuAu RHIC RAA results normalized to RAA(CNM) Tony Frawley’s talk at Trento Heavy Quarkonia Workhop May 2009 • Both Pb-Pb and Au-Au seem to depart from the reference curve at NPart~200 • For central collisions more important suppression in Au-Au with respect to Pb-Pb Systematic errors on the CNM reference are shown for all points

  21. Comparison with new PHENIX results (2) Results are shown as a function of a the multiplicity of charged particles (~ energy density, assuming SPS~RHIC) The relation between the charged multiplicity and NPart is obtained AuAu using PHOBOS data (Phys.Rev.C65 061901 (2002) PbPb using NA50 data (Phys.Lett.B 530 1-4 (2002) 43-55) Good agreement between PbPb and AuAu

  22. Conclusions The determination of cold nuclear matter effects affecting the J/ is fundamental in order to understand J/ dissociation in a hot matter New 158 Gev pA results from NA60 have improved the understanding of this reference This new reference imply a smaller anomalous suppression with respect to previous estimates The PHENIX and SPS result seem to point to a scaling of the suppression as a function of the charged multiplicity Open charm A-dependence may add further useful information: first results from NA60 soon available

  23. Backup slides

  24. Differential distributions: d/dy, d/dxF 400 GeV 158 GeV 158 GeV • Gaussian fit gives y=0.05±0.05, y=0.51±0.02 400 GeV • y-distribution wider at 400 GeV, as expected • peak position not well constrained at 400 GeV • imposing y=-0.2 (NA50 at 400 GeV) y=0.81±0.03 (NA50 got 0.85)

  25. Comparison with previous experiments NA50 HERA-B (920 GeV) NA50 (400 GeV) strong, A-independent, backward shift (y=0.2, corresponding to xF= 0.045). Incompatible with HERA-B ? small displacement of the center of the xF distribution towards negative values, increasing with A (xF<0.01) HERA-B NA60 points (@400GeV) seem to confirm NA50 result, but data probably not precise enough to quantitatively investigate rapidity shift

  26. pT incident parton  A1/3 cc Differential distributions: dN/dpT pT broadening (Cronin effect) observed by all experiments NA60 158 GeV Fit pT2 for various nuclei as <pT2>= <pT2>pp+ gN  L <pT2>= <pT2>pp+  (A1/3-1) <pT2>pp  shows a roughly linear increase vs s • New NA60 results suggest a decrease at low √s • NA3 result similar to high √s values • Agreement NA60 vs NA50 at 400 GeV 

  27. y zHE zGJ J/ polarization zCS pprojectile ptarget y x Viewed from dimuonrest frame decay plane m+ ϕ  z axis pprojectile ptarget Viewed from dimuonrest frame reaction plane Important tool for the study of quarkonium production mechanisms Debated topic because of inconsistencies between theory and data J/ polarization measured from the angular distribution of the decay μ Recent studies have pointed out the importance of the choice of the polarization frame(P. Faccioli et al. arXiv:0902.4462, E. Braaten et al arXiv:0812.3727) • degree of polarization is frame dependent • results comparable only if the same frame is adopted

  28. CDF(p-p @ √s =1.8 TeV) Gottfried-Jackson Collins-Soper Helicity J/ polarization results * HERA-B (pA @ 920 GeV)  clear hierarchy in the values of the decay angular parameters measured in the different frames |λHE|< |λGJ|< |λCS| |νHE|> |νGJ|> |νCS|  polarization depends on the J/ pT no strong dependence on xF E866 (p-Cu @ 800GeV) PHENIX (pp √s =200GeV) Large transverse polarization at high pT predicted by NRQCD NOT seen

  29. NA60 pA J/ polarization results HE CS Helicity λ NA60, 158 GeV E866, 800 GeV NA3, 280 GeV NA60, 400 GeV HERA-B, 920 GeV Collins-Soper p-A 158 GeV p-A 400 GeV First measurement of the full angular distribution • Preliminary systematic error ~± 0.10 (increasing with pT) • Large errors for  in the CS frame (acc. large only at small |cosCS|) Comparison with other experiments: λCStends to be negative and larger in absolute value with respect to λHE Global understanding of measured pattern not yet available

  30. Helicity frame NA60 In-In J/ polarization results Npart Npart First full measurement of the J/ angular distribution in nuclear collisions Results vs. transverse momentum Results vs. centrality Polarization is rather small everywhere: no pT or centrality dependence Positive azimuthal coefficient at low pT? Quantitative predictions needed!

  31. Cold nuclear matter effects vs. √s Complicate interpretation of the  vs. xF pattern Many competing effects: • Shadowing • Initial state energy loss • Final state energy loss • Nuclear dissociation Can a suitable combination of these effects generate a √s dependence of  at fixed xF ? E. Scomparin, Trento worshop, May 2009 Try to calculate  vs xF for various √s • Use LO CEM formulas(from R. Vogt, PR310 (1999) 197) • Shadowing (EKS98, EPS08 & GRV98LO pdfs) Gavin-Milana (PRL68(1992)1834) • Initial state energy loss BDMPS (Arleo, JHEP11(2002)044) Constant Depending on √sN • Nuclear dissociation Get  from the ratio Pb / Be

  32. 158 GeV 400 GeV 800 GeV Cold nuclear matter effects vs. √s (2) EKS98 158 GeV 400 GeV 800 GeV absJ/=0 mb EKS98 Shadowing absJ/ = 0 assume no initial state energy loss • weak √s-dependence at fixed xF • almost negligible at midrapidity • at foward rapidity  decreases when increasing √s Initial state energy loss (GM) In each collision (prior to the one creating the cc) the parton looses a fixed fraction of its energy This model may explain the high xF behaviour, but cannot create a √s-dependence at fixed xF (x1 shift does not depend on proton momentum)

  33. 158 GeV 400 GeV 800 GeV Cold nuclear matter effects vs. √s (3) Initial state energy loss (BDMPS) This mechanism is able to produce an effect which depends on √s but • no  decrease at high xF • abnormally high qhat needed (estimate in cold nuclear matter  qhat~0.25 GeV/fm2) A simple combination of shadowing+initial state energy loss + constant nuclear dissociation cross section absJ/ cannot reproduce data on  vs xF • Is it possible to find, using the data sets collected at various • energies, a ”universal” absJ/ vs √sN ? • Initial energy loss should be studied in more detail • Drell-Yan data to constrain free parameters • inside models (see e.g. F.Arleo,PLB532(2002)231) • How to combine • Constant energy loss per unit length (squared) • Fixed fraction of energy loss per collision

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