Heavy quark and quarkonium evolutions in heavy ion collisions

Transcription

1 Heavy quark and quarkonium evolutions in heavy ion collisions Baoyi Chen Tianjin University & Goethe Univeristy Main Collaborators: Pengfei Zhuang, Ralf Rapp, Yunpeng Liu, Xiaojian Du, Wangmei Zha, Carsten Greiner 1

2 Topics ψ(2s) 1) Heavy quarkonium production mechanisms in the Quark Gluon Plasma primordial production, regeneration, photoproduction, transitions, 2) Charm diffusions in the QGP Langevin + Wigner function for single charm evolutions and recombination large v 2 puzzle of J ψ, v 2 between J ψ and ψ(2s), 3) Quantum effects inside ccbar dipole by color screening QGP screened heavy quark potential transitions between different bound states, wave function evolutions (depend on T) 4) Charmonium photoproduction from EB fields, even at b < 2R A important at extremely low p T <0.1 GeV/c 5) pa collisions ( still QGP existence?) Phys.Lett. B 765, 323(2017) J ψ, ψ(2s) 6) Ds/D0 enhancement: strange enhancement and charm conservation 2

3 V = U C. Shen Satz, et al J ψ c c Sequential dissociation c + c J ψ + g 3

4 V = U C. Shen Satz, et al J ψ c c c + c J ψ + g Sequential dissociation Heavy Ion: light hadron spectra; Jet energy loss; heavy quark thermalize; quarkonium dissociation thermal photons; B induced chiral effect 4

5 Heavy quarkonium as a probe of QGP J/ψ as a probe of QGP: J/ψ suffer color screening end inelastic collisions of partons in QGP R J ψ AA J/psi production in AA collisions (with cold and hot matter effects) N N J ψ AA J ψ pp Ncoll J/psi production in pp collisions (without CNM and HM) From Lattice BC, Du, Rapp, arxiv:

6 1. Charmonium production mechanisms in HIC 6

7 Heavy quarkonium as a probe of QGP Transport model f ψ t α ψ p t, x t, τ, b = 1 2E t β ψ p t, x t, τ, b = Quark number + p ψ E xf ψ = -α ψ f ψ +β ψ d 3 k 2π 3 2E g σ gψ p, k, T 4F gψ p, k f g (k, T) 1 d 3 k d 3 q c 2 4 (2π) 9 E t E g E c d 3 q c ψg W E c c ( qc, q c) f c ( q c, T) f c q c, T c 2π 4 δ 4 (p + k q c q c) J/ψ + g c + c c+ c J/ψ + g N c c J ψ ~ (N c Dynamical evolution Higher temperature,larger α ψ, less initial production Larger N c c, larger β ψ, more regeneration c ) 2 Initially produced ψ:from parton hard scatterings, carry large p T Regenerated: charm interact with QGP, loss energy, carry QGP collective flow 7

8 Charmonium in QGP Init. + rege. Initial production Charm Cross-section B. Chen, PRC 93, (2016) Summary: Regeneration dominates at low p T, and total yield Initial production dominates at high p T 8

9 2. Charm diffusion in the expanding QGP 9

10 Charm diffusion D mesons obtain the similar collective flows like light hadrons indicate the momentum thermalization of charm quarks at the QGP hadronization. PRL, 111, (2013) However, how and when charm quarks reach thermalization? Depending on: QGP temperature, coupling strength, Charm momentum, etc How does charm diffusion suppress the Ψ regeneration process? 10

11 Charm diffusion First, Let s assume an instant charm thermalization 1) Local momentum distribution f c p = Nnorm e pμ uμ T +1 2) Charm distribution in coordinate space in local fliud cell u μ : velocity of QGP cell μ ρ c r u μ = 0 Conservation of charm quark number; Strong diffusion (controlled by u μ ) Large mass of charm quark: Not chemical equilibrium Full distribution in phase space f c (r, p) = ρ c r f c p 3) Charm initial distribution from hard scatterings, ρ c τ 0, x T, η = T A x T T B x T b coshη τ 0 dσc c pp Usually with uncertainties ~ 50% dη 11

12 Charm diffusion and kinetic equilibrium Remember that N J ψ dv N c V QGP N c W V combine (N c c) 2 QGP V QGP Charm expands outside with QGP coalescence model dn J ψ d 2 P T dη = C Pμ dσ μ R 2π 3 J. Zhao, B. Chen, arxiv: d 4 rd 4 p 2π 3 c + c J/ψ +g W r, p f c(r 1, p 1, t)f c(r 2, p 2, t) C=1/12 for vector meson (J/psi) Wigner function describes the recombination probability of one c and c: W r, p = d 3 ye i p y ψ( r + y 2 )ψ ( r y 2 ) ψ r : wavefunction of charmonium eigenstate. (from time-independent Schrodinger equation) 12

13 Charm diffusion and kinetic equilibrium Remember that N J ψ dv N c V QGP N c W V combine (N c c) 2 QGP V QGP Charm expands outside with QGP 2.76 TeV V.S TeV (Pb-Pb collisions): larger initial T 0 QGP, larger QGP volume at hadronization charm number enhanced by more than 50% Accelerating expansion makes V QGP (T = T c, 5.02) larger N J ψ(5.02) does not become times, (see exp. Data later) R AA = N c+ c J/ψ+g AA Experimental data gives: 13 J N ψ pp N coll

14 J/ψ R AA at 2.76 and 5.02 TeV dσc c pp dy 2 ψ dσ pp dy arxiv: Cross section: dσc c pp dy = 0. 33mb (0. 57mb) for 2.76 (5.02) TeV Upper limit: dσ pp enhanced by 20% dy The ratio of charm quark number at 5.02 and 2.76 TeV is around 1.7 with large uncertainty, (1) with the same QGP, we expect R AA ratio charm ratio 1.7 (2) with different QGP, R AA ratio 1.1 Strong diffusion of charm suppress J/ψ regeneration. c c 14

15 J/ψ R AA at 2.76 and 5.02 TeV 1). Charm collective flow also change the regenerated J/ψ p T distribution 2). At 5.02 TeV, QGP expansion stronger, push charm quark to larger p T bin arxiv: ). Underestimation at high p T is due to the lack of initial production, which dominate the high p T region. 15

16 J/ψ R AA at 2.76 and 5.02 TeV 1). Charm collective flow also change the regenerated J/ψ p T distribution 2). At 5.02 TeV, QGP expansion stronger, push charm quark to larger p T bin arxiv: ). Underestimation at high p T is due to the lack of initial production, which dominate the high p T region. Can we define an observable to measure the charm diffusion effect? independent of charm cross section, shadowing effect, etc 16

17 N J/ψ N D 2 Hot Medium Effect N J ψ (N D ) 2 dv f c norm f c norm W combine arxiv: This ratio in AA collisions: 1 eliminate the shadowing effect. 2 3 c c Does NOT depend on dσ pp dη Contains hot medium effects on charm (collective flows of QGP change f c norm ) 17

18 N J/ψ N D 2 Hot Medium Effect N J ψ (N D ) 2 dv f c norm f c norm W combine arxiv: This ratio in AA collisions: 1 eliminate the shadowing effect. 2 3 c c Does NOT depend on dσ pp dη Contains hot medium effects on charm (collective flows of QGP change f c norm ) Centrality dependence from semi-central to central collisions: larger T 0 QGP, stronger QGP expansion, recombination probability of ONE c and c decreases. s NN Dependence: higher s NN, QGP expansion also stronger. 18

19 ψ(2s) v.s. J/ψ dp dt = η D p p + ξ η D = T DE c D: spatial diffusion coeff. ψ(2s) will be regenerated in the later stage of QGP expansion, ψ(2s) Carry relatively larger collective flows independent of c coupling strength B. Chen, PRC 95 (2017)

20 ψ(2s) v.s. J/ψ dp dt = η D p p + ξ η D = T DE c D: spatial diffusion coeff. non-thermal charm + coalescence can explain J/ψ v 2 at 5.02 TeV? Shape of v 2 is important! Preliminary (transport model) B. Chen, PRC 95 (2017)

21 ψ(2s) production 3. Internal evolutions of c c dipole wave function 21

22 τ c c < 0.1 fm Time-dependent Schrodinger equation τ ψ < τ 0 (~0.6 fm) pp data c c dipole J/ψ and ψ(2s) measurements in experiments PRL109(2012) S.Digal, et al, EPJ, 05 c c >= c 1S (t) J ψ > +c 2S t ψ(2s) > + Exp. measure the eigenstates of Cornell potential (in vacuum); by dilepton decay. c c dipole potential in QGP is COLOR SCREENED. transitions 22

23 τ c c < 0.1 fm Time-dependent Schrodinger equation τ ψ < τ 0 (~0.6 fm) pp data c c dipole r c c ~ 1 (2m c ) ~0. 07 fm Radii of J/ψ and ψ(2s) : 0.5 fm and 0.9 fm It takes some time to evolve into a charmonium, Shorter for ground state, longer for 2S Color screening change ccbar dipole wave function evolutions, Change fractions of 1S and 2S in the dipole. 23

24 τ c c < 0.1 fm Time-dependent Schrodinger equation τ ψ < τ 0 (~0.6 fm) pp data c c dipole R. Katz, P. B. Gossiaux, 16 B.Z. Kopeliovich, et al, PRC, 15 Taesoo Song, et al, PRC, 15 r: relative distance between c and c m μ = 2: scaling mass m c Numerical form: Wavefunction of eigenstates: Ψ klm r = R kl (r)y lm (θ, φ) Matrix elements: a = i Δt (2m μ (Δr) 2 ) b= iδt 24

25 Heavy quark potential at finite temperature ms eigenstate components in one dipole: Heavy quark potential : BC, Du, Rapp, arxiv: S.Digal, et al, EPJ, 05 At ~2Tc, Strong color screenin for 1S and 2S At ~1Tc, potential recover at <r(1s)> 25

26 Initialization of c c wavefunction Evolutions of one c c with different potential V c c r = 0 Testing codes V c c r = Cornell Potential With weak potential, the c c dipole becomes a loosely bound dipole, its wavefunction expands outside. the overlap between ψ c c (r, t) and Ψ(2S) increase at first, then decrease 26

27 Heavy quark dipole in Static Medium With real part of heavy quark potential (color screening) arxiv: At high T, Large density of partons, c c wavefunction expand outside, correspond transitions of 1S -> 2S At low T, recovering of potential at mean radius of 1S: 1S well constrainted, mainly transitions of 2S->1S Additional parton inelastic scatterings may change the game. 27

28 4. Photoproduction from electromagnetic fields at b < 2R A 28

29 Equivalent Photon Approximation Prog.Part.Nucl.Phys. 39, , 1997 eb m π G charges moves at nearly speed of light produce E-B fields Strong Lorentz-contracted Electromagnetic field (transverse) approximated as longitudinally moving photons Equivalent-Photon-Approximation Fermi,

30 Equivalent Photon Approximation Prog.Part.Nucl.Phys. 39, , 1997 eb m π G Ultra-peripheral collisions charges moves at nearly speed of light produce E-B fields Strong Lorentz-contracted Electromagnetic field (transverse) approximated as longitudinally moving photons Equivalent-Photon-Approximation Fermi, 1924 γ + A J ψ + A γγ c c(l l) 30

31 p T and b dependence Compare the p T and b dependence of coherent photoproduction and hadroproduction Charmonium hadro-production (initial distributions) in Pb-Pb collisions, can be extracted from the scaling with pp collisions. Normalized distribution J ψ dσ pp = 2πp T dp T 2(n 1) 2π n 2 < p 2 J ψ T > [1 + pp 2 p T n 2 < p 2 J ψ T > ] n pp Works well for RHIC and LHC 2.76 TeV forward rapidity 2.5<y<4, inclusive J ψ < 2 J ψ pt > pp = 7. 8( GeV c) 2 n = 4 At p T 0, dσ J ψ pp p dp T T Hadronic cross section drops to zero at p T 0 J. Zhao, B. Chen, arxiv: Physics Letters B

32 p T and b dependence Fractions of hadronic cross sections in different pt region p T range (GeV/c) σ pt1 p T2 σ total % % % Rapidity differential cross section at 2.76 TeV 2.5<y<4 J ψ dσ pp dy d 2 J ψ σ pp 2πp T dp T dy = = 2. 3 μb dσ J ψ pp J ψ dσ pp 2πp T dp T dy Coherent photoproduction: Photons interact with entire nucleus, p T 1 R A GeV/c Ultra-peripheral collisions (photoproduction) Exp. < p T >= GeV/c PRL 116,, (2016) 32

33 pt and b dependence Hadonic initial yield b=10.2 fm 0 < p T < 0.04 GeV/c J ψ J ψ N AA = σpp Hadroproduction 2. 5 < y < d 2 x T T A x T T B x T b photoproduction < p T < < p T < ~ < p T < < p T < = 30 fm 2 (b = 10. 2) 33

34 pt and b dependence Hadonic initial yield J ψ J ψ N AA = σpp d 2 x T T A x T T B x T b = 30 fm 2 (b = 10. 2) Overlap area between two colliding nuclei, ~ the hadronic yields. b 34

35 Photoproduction contribution p T < 0. 3 LHC RHIC Significant enhancement of J ψ yield in low p T < 0. 1 GeV/c, and peripheral and semi-central collisions At Np=100, T 0 QGP = 2Tc Similar with maximum T at RHIC Au-Au QGP effect important! Photoproduction important! 35

36 J ψ from hadro-production and EB field b < 2R A Heavy quarks (and quarkonium) + light partons (QGP) Produced in the overlap area. gg(q q) J ψ + g c + c Transport model (heavy quarkonium) f ψ + p ψ t E xf ψ = -α ψ f ψ + β ψ Hydrodynamics (light partons) μ T μν = 0 b < 2R A or b 2R A Produced in the entire nucleus surface γa J ψ A γa dn γ N ψ dw dw σ decay γa J ψa Γ QGP R AA = NγA + N hadro N hadro 36

37 J ψ from electromagnetic field Mainly three ingredients: γa dn γ N ψ dw dw σ decay γa J ψa Γ QGP Already Given before Photon density dn γ dw emitted by one nucleus Poynting vector Energy flux of the fields Energy flux of equivalent photons Photon density Nuclear charge form factor is the Fourier transform of Woods-Saxon distribution 37

38 J ψ from electromagnetic field Photon-nucleus cross section σ γa J ψa Start from photon-proton σ γp gamma dsigma/dt Widely studied in UPC S.R.Klein, J. Nystrand, PRC, 1999 Physics Roports, G.Baur, et al, 2002 With the optical theorem, above cross section can be written as J ψ A total cross section. With Geometry scale, Using optical theorem again, and finally Measured by HERA data. (main input of photo-production) Center of mass energy of photon and proton 38

39 J ψ from EB field + QGP Our formula for J ψ photo-production with QGP effect Photo- J/ψ Hadroproduction V.S. Photoproduction (without QGP Effect) pt<0.3 GeV/c 2.76 TeV Pb-Pb 2.5<y<4 QGP Hadro- J/ψ hadroproduction show strong dependence on impact parameter (overlap between nucleus A and B). 39

40 Total J ψ from EB field + QGP QGP suppression W. Shi, W. Zha, B. Chen, arxiv: Also significant enhancement at N p 100, where T 0 QGP = 2Tc, similar with RHIC 200 GeV Au-Au (most central) When N part 0 (b > 2R A ), hadroproduction 0, photoproduction nonzero, R AA infinity 40

41 Total J ψ from EB field + QGP LHC pt<0.05, γa J ψ A important 0.1<pT<2-4, c + c J ψ + g pt>4 primordial production W. Shi, W. Zha, B. Chen, arxiv: R AA decreases, then increases with pt photoproduction rege. init. RHIC 41

42 Photoproduced 2S/1S Photoproduction is usually studied in Ultra-peripheral Collisions, absent of hadronic collisions and QGP Can photoproduction and QGP be BOTH important? 42

43 Photoproduced 2S/1S Photoproduction is usually studied in Ultra-peripheral Collisions, absent of hadronic collisions and QGP Can photoproduction and QGP be BOTH important? Enhancement: additional photoproduction on both 1S and 2S Suppression: QGP effect. Independent of initial nuclear effects B.Chen, et al, in preparation 43

44 Photoproduced 2S/1S Spatial distribution of hadroproduction and coherent photoproductio Hadroproduction: in the overlap area of two nuclei, where QGP are also produced. Spatial distribution of QGP initial Temperature Photoproduction: over the entire nucleare surface photons interact with entire nucleus 2S/1S shape needs 3 factors: 1) QGP existence, 2) abundant photoproduction, 3) different spatial distributions 44

45 Photoproduction at RHIC At RHIC, photoproduction from γ + A ρ + A, γγ e + e? 45

46 Summary We study the charmonium production in the heavy ion collisions with QGP. When most of final charmonia are from c and c combination, charmonia behavior is closely connected with charm diffusions in the expanding QGP. ψ(2s) production is an interesting topic, and internal evolutions (transitions between 1S and 2S) should be crucial for 2S/1S obvervables In the extremely low p T regions, even at b < 2R A, photoproduction from strong electromagnetic fields can be larger than the hadroproduction in certain centralities. We also propose the strong enhancement at p T <0.1 GeV/c and suppression at high p T of 2S/1S, to be an probe for both photoproduction and QGP effects Future interests: electromagnetic fields induced particle production, EB-QGP, particle correlations, etc 46