ALICE results on quarkonia

1. ALICE results on quarkonia • Introduction • Selected pp highlights • Results from the 2011 PbPb run • J/ nuclear modification factor(s), v2, pT, (2S) • Prospects and conclusions E. Scomparin (INFN Torino) for the ALICE Collaboration Washington D.C., August 16 2012 LHC: a new dawn for quarkonia studies…..

2. Introduction (1) Quarkonia suppression via colour screening  probe of deconfinement (Matsui and Satz, PLB 178 (1986) 416) Sequential suppression of the quarkonium states (Digal, Petreczky, Satz, PRD 64 (2001) 0940150) Enhancement via (re)generation of quarkonia at the phase boundary, due to the large heavy-quark multiplicity (Andronic, Braun-Munzinger,Redlich, Stachel, PLB 571(2003) 36)

3. Introduction (2) Studies performed at SPS/RHIC energies showed a significant J/ suppression in heavy-ion collisions (even after taking into account cold nuclear matter effects) (Brambilla et al., EPJ C71(2011) 1534) First results from ALICE (QM2011) have shown a smaller suppression with respect to RHIC, compatible with J/ (re)generation (ALICE coll., arXiv:1202.1383) Today  deeper understanding thanks to the high-lumi 2011 Pb run

4. Experiment and data taking Quarkonia detection In the forward muon spectrometer (2.5<y<4) via +-decays In the central barrel (|y|<0.9) via e+e-decays Integrated luminosity for quarkonia analysis MB trigger based on Forward scintillator arrays (VZERO) Silicon pixel (SPD) In addition, trigger on muon (pairs) in the forward spectrometer (pT ~ 1 GeV/c threshold for Pb2011) (up to) ~100 nb-1 for pp ~ 70 b-1 for PbPb

5. Charmoniadetection (PbPb) in ALICE |y|<0.9 Electron analysis: background subtracted with event mixing  Signal extraction by event counting Muon analysis: fit to the invariant mass spectra  signal extraction by integrating the Crystal Ball line shape

6. pp: selected results Data taking at s=2.76 TeVessential to build the RAA reference, result based on Linte=1.1 nb-1 and Lint=19.9 nb-1 pT-integrated cross sections ALICE Coll., arXiv:1203.3641 Results in agreement with NLO NRQCD calculations

7. Multiplicity dependence in pp

8. Pb-Pb collisions: RAA Centrality dependence of the nuclear modification factor studied at both central and forward rapidities To be updated At forward y, RAAflattens for Npart 100 At midrapidity hint for an increase of RAA for central collisions

9. Comparison with RHIC and models Produce corresponding plot for midrapidity Forward rapidity RAA larger than the corresponding PHENIX result (1.2<y<2.2) for Npart 100 Models which include a (re)generation component are in Fair agreement with the data

10. Comparison with models at y=0

11. RAAvs centrality: differential study in pTbins Shaded box: uncorrelated syst. uncertainties Open box: (partially) correlated syst. uncertainties Larger suppression in the higher pT bins for central events, in qualitative agreement with expectations for a (re)generation scenario  Compare with models and with PHENIX results

12. Comparison with models Fair agreement with models also when looking at RAAvsNpart in pTbins

13. pTdependence of RAA Smaller suppression at low pT observed for the first time! PHENIX observed a completely different behaviour Plus comparison with PHENIX Compatible with (re)generation At small transverse momenta

14. J/ pT spectra Relative shapes of spectra strictly related to RAA Finer binning than in RAA studies possible (not limited by pp statistics) Peripheral events: remove low pTregion (possible contribution of coherent J/ photoproduction, now under study)

15. pT, pT2 vs centrality Opposite behaviour with respect to lower energy machines: confirms that a new regime is reached at the LHC

16. Rapidity dependence of RAA

17. J/ elliptic flow J/ from (re)combination should lead to a significant elliptic flow signal at LHC energy Analysis performed using the EP approach (from VZERO-A ) Checks with alternative methods performed (gapped correlations)

18. Non-zero J/ elliptic flow at the LHC STAR: v2 compatible with zero everywhere ALICE: hint for non-zero v2 (2.2 ) in semi-central events for 2<pT<4 GeV/c ALICE: non-zero v2 in central And semi-central collisions (3.5 ) Qualitative agreement with transport models including (re)generation Complaments indications already obtained from RAA studies

19. A first look at the (2S) Study of excited charmonium states expected to yield complementary information Limited integrated luminosity and S/B make such a study difficult with the present set of data Compare (2S) yield (normalized to J/) in Pb-Pb and p-p

20. Double ratio [(2S)/J/]PbPb/ [(2S)/J/]pp Extend CMS studies towards low pT Compare with CMS in A similar pT range (although slightly larger y) Large uncertainties prevent firm conclusion on (2S) suppression Large enhancement seen by CMS for central events seems disfavoured by our result

21. Conclusions

22. ALICE: specific features • ALICE peculiarities among the LHC experiments • Focus on PID investigate chemical composition of the hot matter • Push acceptance down to pT=0 (low material budget, low B) •  many QGP-related features become more evident at low pT • Sustain very high hadronic multiplicities (up to dNch/d~8103)

23. PID performance: selected plots ITS Silicon Drift/Strip dE/dx TPC dE/dx Ω ΛΚ TOF

24. Analyzed data samples 2010 2011 • Triggers • MB: based on VZERO • (A and C) and SPD • SINGLE MUON: forward muon in coincidence with MB trigger

25. Focus on Pb-Pb • Analysis of 2010 PbPb data well advanced. Results on: • Global event features • Collective expansion • Strangeness and chemical composition • Parton energy loss in the medium • Light flavours • Heavy flavours • Quarkonia dissociation/regeneration • in the medium See ALICE talks by: C. Perez Lara (Tue pm) S. Beole (Thu pm) A. Mischke (Thu pm) PRL106 (2011) 032301 • Centrality estimate: • standard approach • Glauber model fits • Define classes corresponding • to fractions of the inelastic • Pb-Pbcross section

26. Charged multiplicity – Energy density PRL106 (2011) 032301 PRL105 (2010) 252301 • dNch/d = 1584  76 • (dNch/d)/(Npart/2) = 8.3  0.4 • ≈ 2.1 x central AuAuat √sNN=0.2 TeV • ≈ 1.9 x pp (NSD) at √s=2.36 TeV • Stronger rise with √s in AA w.r.t. pp • Stronger rise with √s in AA w.r.t. log extrapolation from lower energies • Very similar centrality dependence at LHC & RHIC, after scaling RHIC results (x 2.1) to the multiplicity of central collisions at the LHC

27. System size • Spatial extent of the particle emitting source extracted from interferometry of identical bosons • Two-particle momentum correlations in 3 orthogonal directions -> HBT radii (Rlong, Rside, Rout) • Size: twice w.r.t. RHIC • Lifetime: 40% higher w.r.t. RHIC ALICE: PLB696 (2011) 328 ALICE: PLB696 (2011) 328

28. Identified hadron spectra • Combined analysis (ITS, TPC and TOF) • Lines = blast-wave fits, extract • Integrated yields • Average pT • Parameters of the system at the thermal freeze-out, Tfoand  (radial flow)

29. Radial expansion of the system Centrality STAR pp √s=200 GeV Blast-wave fit parameters • Common blast-wave fit to , K and p • Strong radial flow: b≈0.66 for most central collisions, 10% higher than at RHIC • Freeze-out temperature below 100 MeV • Significant change in mean pT between √sNN=200 GeV and 2.76 TeV harder spectra • For the same dN/dhhigher mean pT than at RHIC

30. Hadrochemistry • Relative abundances of hadron species can be described by statistical distributions (Tch, B) A.Andronic et al., Nucl.Phys.A772(2006) • Description still not satisfactory • at LHC energy • Low Tch suggested by p spectra, but • excluded by  and  • If p excluded, Tch =164 MeV •  Tch (LHC) ~ Tch(RHIC) ~ Tc J.Cleymans et al., Phys.Rev.C73(2006)034905

31. Elliptic flow • v2 (LHC) ~ 1.3 v2 (RHIC) (pTintegrated) • Increase consistent with increased radial expansion (higher pT) • System at LHC energy still behaves as a near-perfect fluid, not gas!

32. Identified particle v2 • Elliptic flow mass dependence due to large radial flow • Magnitude and mass splitting predicted by viscous hydro • in all centrality bins •  and K v2(pT) well described, disagreement for p in central data • Radial flow too small from hydro, hadronicrescatteringsplay an • important role in flow development

33. Charged hadron RAA Related to parton energy loss, in the BDMPS approach • RAA(pT) for charged particles : larger suppression wrt RHIC • Suppression increases with increasing centrality • Minimum for pT~ 6-7 GeV/c in all centrality classes • RAAincreases in the region pT>10 GeV/c • Hint of flattening above 30 GeV/c

34. Identified particle RAA • Mesons vs baryons: different RAA at intermediate pT • Related to baryon enhancement, observed e.g. in /K ratio • At high pT(>8-10 GeV/c)RAA universality for light hadrons • For hadrons containing heavy quarks, smaller suppression expected: • dead cone effect, gluon radiation • suppressed for <mq/Eq

35. Open charm in ALICE • Analysis strategy • Invariant mass analysis of fully reconstructed decay topologies displaced from the primary vertex • Feed down from B (10-15 % after cuts) subtracted using FONLL • Plus in PbPb hypothesis on RAA of D from B K p D+K-p+p+

36. D-meson RAA • pp reference from measured D0, D+ and D* pT differential cross-sections at 7 TeV scaled to 2.76 TeV with FONLL • Suppression of prompt D mesons in central (0-20%) PbPb collisions by a factor 4-5 for pT>5 GeV/c • Little shadowing at high pT suppression comes from hot matter • Similar suppression for D mesons and pions • Maybe a hint of RAAD > RAAπ at low pT

37. Electrons from heavy-flavour decays e • Cocktail method • Inclusive electron pT spectrum • Electron PID from TOF+TPC • TRD used in pp • Subtract cocktail of known background sources • Impact parameter method (only ppfor now) • Track impact parameter cut to • select electrons from beauty

38. RAA of cocktail-subtracted electrons • pp reference from measured heavy flavour electrons pT differential cross-sections at 7 TeV scaled to 2.76 TeV with FONLL • Analysis of pp data at 2.76 TeV ongoing (direct reference) • Suppression of cocktail-subtracted electrons • Factor 1.5 - 4 for pT>3.5 GeV/c in the most central (0-10%) events • Suppression increases with increasing centrality

39. Heavy-flavor decay muons m • Single muonsat forward rapidity (-4<<-2.5) • Background from primary /K decay not subtracted • estimated with HIJING to be 9% in the most central class (0-10%) for pT>6 GeV/c • RCP for inclusive muonsin 6<pT<10 GeV/c • suppression increases with increasing centrality

40. J/ suppression peripheral central • Inclusive J/y RAA • pp reference from pp data set at 2.76 TeV • Contribution from B feed-down not subtracted (very small effect) • J/y are suppressed with respect to pp collisions • J/y RAAalmost independent of centrality

41. J/: comparison with RHIC ALICE, LHC, forward rapidity PHENIX, RHIC, mid-rapidity PHENIX, RHIC, forward rapidity • Less suppression than at RHIC at forward rapidity: • RAA(ALICE) > RAA(PHENIX, 1.2<y<2.2) • Similar suppression as at RHIC at midrapidity (not for central!) • RAA(ALICE) ≈ RAA(PHENIX, |y|<0.35) • Caveat:cold nuclear matter effects different at RHIC and LHC needs pPb running

42. J/: comparison to models A.Andronic et al., arXiv:1106.6321 P.Braun-Munzinger et al.,PLB490(2000) 196 R.Rapp, X.Zhao, NPA859(2011)114 • Parton transport model • J/ dissociation in QGP • J/ regeneration by charm • quark pair recombination • Feed-down from B-decays • Shadowing • Statistical hadronizationmodel • Screening by QGP of all J/ • Charmonium production at • phase boundary by statistical • combination of uncorrelated • c-quarks

43. A pp new result: J/ polarization • ALICE focusses on pp results mainly as reference for PbPb • On hard probes usually no competition with other LHC • experiments due to smaller luminosity in ALICE • Some notable exceptions, too  J/ polarization • (first LHC results from ALICE, arXiv:1111.1630) • Important measurement to discriminate among the different • theoretical models of J/ production • Long-standing puzzle with CDF results • J/ polarization measured via anisotropies in the angular • distributionsof J/ decay products • (polarization parameters    ) >0  transverse polarization, <0  longitudinal polarization

44. J/ polarization results ALICE Coll., arXiv:1111.1630, accepted by PRL M.Butenschoen, A.Kniehl, arXiv:1201.3862 • First result: almost no polarization for the J/ • First theoretical calculation (NLO NRQCD) compared to data: • promising result, reasonable agreement with theory

45. Prospects, 2011 Pb-Pb data • 2011 Pb-Pb data quite successful • Smooth running, much higher luminosity  ~10 times more • statistics (centrality and rare triggers) compared to 2010 • New, exciting results expected soon! A couple of performance plots Triggering on EMCAL Total 2011 statistics  40000 J/

46. Conclusions • 2011 has been (another) memorable year for ALICE ! • After an already excellent start in 2010, with plenty of pp results, • focus in 2011 on the analysis of the first Pb-Pb run • First results • Medium with >3 times higher energy density than at RHIC • Abundance of hard probes • Soft observables • Smooth evolution of global event characteristics from RHIC to • LHC energies  better constraints for existing models • Move now towards precision differential measurements • Hard probes: novelties, surprises, challenges for theory • Strong suppression of high pT hadrons (factor 7 at pT=7 GeV/c) • Light and heavy quarks RAAsimilar • J/ is less suppressed than at RHIC • Pb-Pb 2011 running: success ! • Work on experiment upgrades is starting

47. Backup

48. 2010 data taking: detector configuration • ITS, TPC, TOF, HMPID, MUON, V0, To, FMD, PMD, ZDC (100%) • TRD (7/18) • EMCAL (4/10) • PHOS (3/5) • HLT (60%)

49. Identified particle spectra Open symbols: ppbar Close symbols: pp

50. More on strangeness Inverse slope increases with mass s do not follow this trend (limited statistics?) <pT> has almost no increase over a factor 36 in √s (ISRLHC)