Heavy quark(onium) at LHC: the statistical hadronization case

Transcription

1 Heavy quark(onium) at LHC: the statistical hadronization case A.Andronic GSI Darmstadt The statistical hadronization model: assumptions and inputs Charmonium: the LHC case in light of the SPS and RHIC data Complete charm chemistry and charm at FAIR Quarkonium in elementary (e + e, pp, pa) vs. AA collisions Summary and outlook AA, P. Braun-Munzinger, K. Redlich, J. Stachel: NPA 789 (27) 334, nucl-th/5171; PLB 659 (28) 149, arxiv: PLB 675 (29) 334, arxiv: ; PLB 678 (29) 35, arxiv: International Workshop XXXVIII on Gross Properties of Nuclei and Nuclear Excitations, Hirschegg, Austria, January 17-23, 2

2 Statistical hadronization: assumptions P.Braun-Munzinger, J.Stachel, PLB 49 (2) 196 all charm quarks are produced in primary hard collisions (t c c 1/2m c.1 fm/c) survive and thermalize in QGP (thermal, but not chemical equilibrium) charmed hadrons are formed at chemical freeze-out together with all hadrons statistical laws, quantum nr. conservation 225 stat. hadronization coalescence is freeze-out at(/the?) phase boundary? LQCD: T c = MeV (hep-lat/ ) no J/ψ surv. in QGP (full screening) can J/ψ survive above T c? (LQCD) Asakawa, Hatsuda, PRL 92 (24) 121 Mocsy, Petreczky, PRL 99 (27) T (MeV) QGP hadrons Data (fits) dn/dy LQCD 4π hadron gas n b =.12 fm -3 ε=4 MeV/fm 3 1 st order crossover critical point µ b (MeV)

3 Timescales for charm(onium) production Karsch & Petronzio, PLB 193 (1987) 5, Blaizot & Ollitrault, PRD 39 (1989) 232 QGP formation time, t QGP SPS (FAIR): t QGP 1 fm/c t J/ψ RHIC, LHC: t QGP.1 fm/c t c c survival of initially-produced J/ψ at SPS/FAIR energies? (T d T c ) collision time, t coll = 2R/γ cm SPS (FAIR): t coll t J/ψ RHIC: t coll < t J/ψ, LHC: t coll << t J/ψ cold nuclear suppression (breakup) important at SPS/FAIR energies? shadowing is yet another (cold nuclear) effect - important at LHC (RHIC?) NB: the only way to distinguish: measure σ c c in pa and AA

4 Statistical hadronization: method and inputs Thermal model calculation (grand canonical) T,µ B : n th X N dir c c = 1 2 g cv ( i nth D i + n th Λ i ) + g 2 cv ( i nth ψ i + n th χ i ) N c c << 1 Canonical (J.Cleymans, K.Redlich, E.Suhonen, Z. Phys. C51 (1991) 137): N dir c c = 1 2 g cn th oc) oc I 1(g c N th I (g c N th oc) + g2 cnc c th g c (charm fugacity) Inputs: T, µ B, Outcome: N D = g c V n th D I 1/I V y=1 (= (dn exp ch /dy)/nth ch ), N J/ψ = g 2 c V nth J/ψ Minimal volume for QGP: VQGP min =4 fm3 Ndir c c (pqcd or exp.)

5 T (MeV) Thermal parameters: from fits to data...well constrained PLB 673 (29) µ b (MeV) Andronic et al. dn/dy 4π Becattini et al. (4π) Letessier,Rafelski (4π) Dumitru et al. (4π) Cleymans et al. (4π) Kaneta,Xu (dn/dy) Volume (fm 3 ) dv/dy fit of yields (dn ch /dy) exp /n ch thermal (T param.) V HBT E895 CERES STAR 2 s NN (GeV) 1 2 s NN (GeV) LHC: (T,µ b )=(164,.8) MeV dv/dy=62 fm 3

6 N dir c c from pqcd calculations (pp) ( N coll ) /dy cc dn R.Vogt, IJMP E12 (23) 211 [hep-ph/111271] 1 NLO (CTEQ5M) extrapolated below 15 GeV (large uncertainty) -1 pqcd is not parameter-free! (PDF, m c, µ R, µ F )... 2 err dn c c /dy for central collisions (N part =35): 2 3 s NN (GeV) SPS:.5, RHIC: 1.6, LHC: 16

7 Canonical suppression and charm fugacity n C i,c = ngc i,c I 1(N c )/I (N c ), N c = i ngc i,c V ; N J/ψ = g2 cv n th J/ψ I 1 /I g c LHC RHIC SPS 2 15 LHC RHIC SPS N part N part

8 J/ψ at SPS 6 x (dn J/ψ /dy) / N coll s NN =17.3 GeV NA5 data 24 (norm.) 1998 data explained with charm enhancement (2 pqcd) see also: NPA 69 (21) 119c, PLB 571 (23)36 Grandchamp, Rapp, PLB 523 (21) 6, NPA 79 (22) 415 Gorenstein et al., PLB 59 (21) 277, PLB 524 (22) SHM, dσ cc /dy=5.7 µb (2x pqcd) N part NA5 data: 1998 ( unofficial ): J. Gosset et al., EPJ C 13 (2) (J/ψ/DY, normalized): EPJ C 39 (25) 335

9 Another powerful charmonium: ψ (SPS) x N ψ, / N J/ψ SHM no corona NA5 data Pb+Pb pp NA5 Data: PbPb: EPJ C49 (27) 559 pp: PLB 466 (1999) 48 good agreement (good agreement also for J/ψ) N ψ /N ψ! contradicts screening model (LQCD: ψ melted at T c ) strong indication of ψ prod. via statistical hadronization N part

10 J/ψ at RHIC: rapidity dependence, R AA R AA J/ψ.8.7 Au+Au -2% (N part =28) Au+Au 2-4% (N part =14) y Model: red: J/ψ pp ref. fit 1-gaussian (dotted: error on σ); pqcd σ c c evidence for statistical hadronization of charmonium (enhanced at y=)

11 J/ψ in dau (RHIC) PHENIX, PRC 77 (28) 24912, arxiv: R dau assume R dau of J/ψ as due only to shadowing of initial charm production cross section: σ c c AuAu = RJ/ψ shad AuAu σ c c pp PHENIX data interpolation y where R J/ψ shad AuAu (nuclear modification due to shadowing) is: R J/ψ shad AuAu ( y ) = R J/ψ (y) RJ/ψ dau ( y) dau

12 J/ψ at RHIC: effect of shadowing R AA J/ψ Au+Au -2% (N part =28) σ cc : pqcd FONLL σ cc : PHENIX +shadowing(dau) Au+Au 2-4% (N part =14) model describes data with PHENIX σ c c (lower error plotted) y

13 J/ψ production relative to charm x (dn J/ψ /dy) / (dn cc /dy) pp, PHENIX data...the most solid observable...with similar features as R AA similar values at RHIC and SPS...with differences in fine details...determined by canonical suppression of open charm.4.2 LHC (dσ cc /dy=639 µb) RHIC (dσ cc /dy=63.1 µb) SPS (dσ cc /dy=5.7 µb) enhancement-like at LHC can. suppr. lifted, quadratic term dominant N part

14 J/ψ at LHC x (dn J/ψ /dy) / (dn cc /dy) dσ cc /dy (mb) solid expectations for LHC...providing we know well (from measurements) the charm production cross section N part

15 Overall charm chemistry dn/dy J/ψ (x) ψ, (x) 2 3 D + D - D D D s + D s - Λ c + Ξ c + s NN (GeV) yields per initial charm pair Λ c prod. favored at large µ b...it s a must at FAIR (CBM) isospin is important ψ /ψ relative yield: 3% in QGP, 13% in pp decreases at low energies snn =7- GeV: T= MeV charmed hadrons can signal the onset of QGP

16 Overall charm chemistry yields per initial charm pair (dn/dy) / (dn cc /dy) -1 Ξ c D D ± D s Λ c J/ψ(x) Λ c prod. favored at large µ b...it s a must at FAIR (CBM) isospin is important ψ /ψ relative yield: 3% in QGP, 13% in pp decreases at low energies snn =7- GeV: -2 2 ψ, (x) s NN (GeV) T= MeV charmed hadrons can signal the onset of QGP

17 Ratios of charmed hadrons to pions Ratio no horn -type structues (at variance to strangeness) -4...due to strong canonical suppression (up to RHIC) -5-6 J/ψ/D xj/ψ/π - D /π - Λ + /π - c J/ψ/D : non-monotonic due to can. suppr. (of D) and energy dep. of σ c c 2 3 s NN (GeV)

18 Effect of modified masses yield with in-medium mases (for open charm hadrons) relative to vacuum masses open charm: very small increase...with large effect on charmonia σ c c = 1 2 (σ D + σ Λc + σ Ξc +...) + (σ ηc + σ J/ψ + σ χc +...) N((m vac + m)/n(m vac ) open charm J/ψ is not affected by medium.6.5 Consequence: the only freedom is in redistribution of the charm quarks.4 m=-5 MeV (Λ c,σ c : - MeV) m=- MeV (D), +5 MeV (D ) (Λ c,σ c : -2 MeV, Λ c,σ c : + MeV) m=-5 MeV (Λ c,σ c : -5 MeV) 2 s NN (GeV)

19 Heavy quarks in e + e collisions Multiplicities Data - e + e, s=91 GeV 3 Model, T=17 MeV, V=16 fm, γ =.66 s 5-flavor 15 no flavor, bottom: x + D D+ D s + D* + D s* ± D s1 ± D s2* J/ψ pr J/ψ ψ χ c1 + Λ c + B B B s B* Υ Λ b - Ξ b open flavor hadrons strongly underpredicted in a pure thermal model (no flavor) very different compared to u,d,s flavors agreement if BR(Z q q) are used in the model (5- flavor)! (T, γ s, V from fits of u,d,s flavors) see also Becattini et al, EPJ C 56 (28) 493 quarkonia strongly underpredicted (95% J/ψ is from B!)

20 Open charm in p(π)a collisions σ D ± /σ D Data pa πa Stat. model data average... appears thermalized (model as for AA)...in the sense of c distribution into hadrons 2 s NN (GeV)

21 Charmonium in pp(a) collisions σ ψ, /σ J/ψ.25.2 Data pa pp(p ) PbPb...is far from thermalized.15.1 data average...while a thermal value is reached in central PbPb (NA5, SPS).5 Statistical model ψ /J/ψ dep. only on T (model as for AA) s NN (GeV)

22 Charmonium in pp(a) collisions 2 R χc Data πa pa(p ) R χc = 2 J=1 σ(χ cj )Br(χ cj J/ψ γ) σ(j/ψ) data average Statistical model s NN (GeV) (fraction of J/ψ mesons from radiative decays of χ c )...is far from thermalized (model as for AA)

23 Bottomonium in pp collisions Relative cross section -1-2 Y, /Y Y,, /Y Statistical model Y, /Y...is very far from thermalized Y,, /Y s NN (GeV)

24 J/ψ: the big difference LHC makes R AA J/ψ 1.2 RHIC data very different centrality dep. - suppression at RHIC 1 determined by canonical suppression.8 (of open charm hadrons) - enhancement at LHC Model LHC RHIC N part ALICE needs 4 central events to measure J/ψ e + e Υ in line for scrutinity... model predicts a suppression pattern (RHIC-like)

25 Summary and outlook statistical hadronization of heavy quarks (produced exclusively in hard collisions, survive and thermalize in QGP)...explains J/ψ data at SPS and RHIC... further tests (incl. phase space distr.) to come soon, in particular at LHC Open questions main uncertainty from charm cross section: more theoretical (NNLO pqcd some time ahead) and experimental progress needed survival of J/ψ in QGP at SPS and RHIC? (LQCD? AdS/CFT?) LHC will provide a clear answer...and further FAIR will trace onset Have we lost J/ψ as a QGP probe? No, lost only as a thermometer...but we gained it as an ultimate probe of the phase boundary A. Andronic - Hirschegg 2