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Cold nuclear matter effects on J/psi production: intrinsic and extrinsic transverse momentum effects Cold nuclear matter effects on J/psi production: intrinsic.

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Presentation on theme: "Cold nuclear matter effects on J/psi production: intrinsic and extrinsic transverse momentum effects Cold nuclear matter effects on J/psi production: intrinsic."— Presentation transcript:

1 Cold nuclear matter effects on J/psi production: intrinsic and extrinsic transverse momentum effects Cold nuclear matter effects on J/psi production: intrinsic and extrinsic transverse momentum effects XLIIIth Rencontres de Moriond: QCD and High Energy Interactions La Thuile, Italy March 2009 Elena G. Ferreiro Universidade de Santiago de Compostela, Spain Work done in collaboration with F. Fleuret, J-P. Lansberg and A. Rakotozafindrabe arXiv :

2 Introduction Too much work trying to understand A+A data (since J/  QGP signal) We do not understand p+A data (where no QGP is possible)!!! only cold nuclear matter (CNM) effects are in play here: shadowing and nuclear absorption In fact, the problem is even more fundamental: we do not know the specific J/  production kinematics even at a partonic level In other words, the partonic process producing the cc and then the J/  Our goal: Investigate the impact of the specific J/  -production kinematics on the [gluon] shadowing effects E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 See talk by Z. Conesa del Valle

3 On the kinematics of J/  production: two approaches Investigating two production mechanisms (including p T for the J/  : g+g → J/  intrinsic scheme: the p T of the J/  comes from initial partons g+g → J/  +g extrinsic scheme: the p T of the J/  is balanced by the outgoing gluon E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 CNM -shadowing- effects depends completly on J/  kinematics (x,Q 2 ) J/  kinematics depends on the production mechanism =>

4 Intrinsic J/  production kinematics Intrinsic scheme: 2 → 1 process LO g+g → J/  y, p T can be determined using PHENIX p+p data Phys. Rev. Lett. 98, (2007) Easy to handle : y J/  and p T J/   directly give x 1,2 E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Straightforward evaluation of the gluon PDF shadowed in the nucleus at x 2 (and x 1 in AA) Q 2 =(2m c ) 2 +(p T ) 2 =m T

5 We deal with a 2 → 2 partonic process with collinear initial gluons g+g → J/  +g The quadri-momentum conservation results in a complex expression of x 2 as a function of (x 1, y, p T ) Information from the data alone – the y and p T spectra– is not sufficient to determine x 1 and x 2 : the presence of a final-state gluon authorizes much more freedom to choose (x 1, x 2 ) for a given set (y, P T ) Models are mandatory to compute the proper weighting of each kinematically allowed (x 1, x 2 ) We use s—channel cut mechanism Extension of CSM Haberzettl and Lansberg, Phys.Rev.Lett.100, (2008) Extrinsic J/  production kinematics E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Good results at low p T

6 Extrinsic vs intrinsic kinematics Intrinsic schemeExtrinsic scheme E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 both implemented in a Monte Carlo codeWe expect different shadowing effects in both cases For a given set (y, p T ): more freedom for x x larger in the extrinsic scheme

7 Nuclear shadowing is an initial-state effect on the partons distributions Gluon distribution functions are modified by the nuclear environment PDFs in nuclei different from the superposition of PDFs of their nucleons Shadowing: a cold nuclear matter effect E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

8 Results for d+Au: rapidity dependence I We need to include nuclear absorption to mach the data E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Different shadowing effects in the 2 approaches Antishadowing peak shifted to less negative y in the extrinsic case Shadowing alone not able to reproduce data Let us add a break-up cross section:  abs intrisic <  abs extrinsic R dAu y E.G.F, F. Fleuret, A. Rakotozandrabe. arXiv :

9 Results for d+Au: rapidity dependence II First choice: Intrinsic scheme  abs =2.8 mb following PHENIX PRC 77, (2008) Extrinsic scheme  abs =4.2 mb following NA50 measurements at SPS E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

10 Results for d+Au: centrality dependence E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Note: PHENIX fit uses different  abs Extrinsic scheme seems to be favorized

11 Results for Au+Au: centrality dependence Intrinsic scheme: Same CNM suppression at forward and central rapidity Extrinsic scheme: More CNM suppression at forward than central rapidity E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Extrinsic scheme : R forward y < R mid y Hot Nuclear matter effects still needed, but… Less need for recombination effects

12 Work in progress: Consider other parametrisations for the shadowing: EPS, nDS(g)… Determination of  abs using a fit to data that take into account all the experimental errors and their correlations E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

13 Work in progress: shadowing rapidity dependence E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Extrinsic sheme Intrinsic sheme EKS98EPS08nDSg EKS98EPS08nDSg

14 E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 EKS98: compatible with intrinsic & extrinsic EPS08: extrinsic scheme is favorized nDSg: neither extrinsic nor intrinsic… Work in progress: fit of  abs with EKS, EPS and nDS(g) Best fit: EPS08+extrinsic

15 Conclusions… E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 For the first time: pT ≠ 0 for J/  shadowing exact J/  kinematics have been taken into account calculation in s-channel cut model We have studied the influence of J/  kinematics on shadowing effect: within 2 schemes: intrinsic (2→ 1) and extrinsic (2→2) p T for different shadowings: EKS98, EPS08, nDGg using s-channel cut model as the production model for p+p in 2→ 2 in the framework of a Glauber MC code Work is progressing: other shadowing parametrisations other production model in pp : NLO, NRQCD,... If they are able calculations for LHC in the extrinsic scheme reproduce low pT data More plots in:

16 Backup slides E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 On the kinematics of J/  production: detail equations s-chanel cut model The Glauber Monte Carlo code Shadowing models Nuclear absorption Work in progress: comparation with Vogt’s results LO without p T ) Fit procedure J/  production mechanisms Some other results Work in progress: RdAu vs Ncoll and RdAu vs pT for EKS98,EPS08, nDSg

17 Extrinsic vs intrinsic kinematics II For a given couple (y, p T ), x 2 is larger in the extrinsic scheme We expect different shadowing effects in both cases E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Much more freedom to choose (x 1, x 2 ) for a given set (y, P T )

18 Results for d+Au: transverse momentum dependence E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Data not conclusive Work to do: Determine best  abs using  2 minimization Try other shadowing parameterisations But before… let’s see what happens for Au+Au

19 Results for Au+Au: rapidity dependence E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Intrinsic: flat behaviour Extrinsic: maximun at y=0 Again, this indicates that less recombination would be required in the extrinsic case

20 Results for Au+Au: transverse momentum dependence Intrinsic scheme:Extrinsic scheme: E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Data not conclusive

21 Work in progress: really progressing!!! E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Merci Andry & Fred!

22 Work in progress: EKS98 centrality dependence E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Extrinsic sheme Intrinsic sheme EKS9 8

23 Work in progress: EPS08 centrality dependence E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Extrinsic sheme Intrinsic sheme EPS08

24 Work in progress: nDSg centrality dependence E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Extrinsic sheme Intrinsic sheme nDGg nDSg

25 Work in progress: EKS98 p T dependence E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Extrinsic sheme Intrinsic sheme EKS98

26 Work in progress: EPS08 p T dependence E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Extrinsic sheme Intrinsic sheme EPS08

27 Work in progress: nDSg p T dependence E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Extrinsic sheme Intrinsic sheme nDSg

28 EKSEPSnDS(g) LO  abs 22 22 22 intrinsic extrinsic Work in progress: fit of  abs with EKS, EPS and nDS(g) intrinsicextrinsic  abs 22 Best fit: extrinsic + EPS08 E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 EPS

29 E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Palaiseau 5 March 09 On the kinematics of J/  production: equations I shadowing nuclear absorption partonic cross section fit to datas-channel cut model kinematic variables

30 On the kinematics of J/  production: equations II Concerning it can be factorized in the nuclear density distribution, the shadowing modification factor and the usual gluon PDFs: where we have included the centrality dependence of the shadowing: E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Palaiseau 5 March 09

31 On the kinematics of J/  production: equations III E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

32 s-channel cut model: motivation a suitable production model for low pT J/  E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

33 s-channel cut contributions E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

34 s-channel cut contributions E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 s-channel cut contributions to the basic CSM: take into account the dynamics of the ccbar in the bound state need for 4-point coupling ccbar-J  -g new degrees of freedom constrained by fits so far the best description of low-p T data

35 s-channel cut contributions: first evaluations E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

36 s-channel cut model vs. other models in the market E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 Various models for the y spectra in p+p [NRQCD calculation] Cooper, Liu & Nayak, Phys. Rev. Lett. 93, (2004) [g(gg)s + Feed-down] Khoze, Martin, Ryskin Stirling, Eur. Phys. J. C39, 163 (2005)

37 The Glauber Monte Carlo code E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 E.G. Ferreiro, F. Fleuret, A. Rakotozandrabe. arXiv : [hep-ph]

38 EKS and EPS shadowing model Introduce an initial parameterisation for nuclear parton distributions R A (x,Q 2 0 ) based on a fit to DIS data at Q 2 0 = 2.25 GeV 2 The further evolution in Q 2 is predicted by the DGLAP equations at LO RHIC high-pT forward-rapidity hadron data suggest a stronger gluon shadowing than obtained in previous global analyses f i A (x,Q 2 )  R i A (x,Q 2 ) f i (x,Q 2 ) GRV-LO, CTEQ4L GRV-LO, CTEQ6L1 high pT RHIC data at Q 2 0 = 1.69 GeV 2 E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Palaiseau 5 March 09

39 EKS shadowing model 1. Introduce an initial parameterisation for nuclear parton distributions R A (x,Q 2 0 ) based on the DIS data at Q 2 0 = 2.25 GeV 2 2. Once the nuclear parton distributions are given at an initial scale Q 2 0 >>Λ 2 QCD the further evolution in Q 2 is predicted by the DGLAP eqs: DGLAP eqs: relation between the logarithmic Q 2 -evolution of the structure functions and the gluon distribution, giving the possibility to calculate the value of ratios at any Q 2 if an initial value is known It is assume that at Q 2 >Q 2 0 the scale evolution of the nuclear parton densities is purely perturbative the initial conditions at Q 2 0 contain the nonperturbative input the evolution is made at leading order (LO) 3. The slope of the nuclear parton distributions in Q 2 is obtained in this way No centrality dependence is included in the model E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 GRV-LO, CTEQ4L

40 EPS shadowing model Global fit to DIS, DY and high pT RHIC data E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 LO, Q 2 0 = 1.69 GeV 2 RHIC high-pT forward-rapidity hadron data suggest a stronger gluon shadowing than obtained in previous global analyses

41 nDSg shadowing model Define nPDF using a convolution approach: the free nucleon parton densities are convoluted with very simple weight functions that parameterize nuclear effects Instead of: LO LO and NLO evolution Differences with other parameterizations: ESK98: less small x shadowing and very little antishadowing at intermediate x in gluon densities HKM: low x shadowing in the valence distribution (none in HKM), ratios for sea and gluon densities approach 1 as x grows while they strongly rise within HKM they use: E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

42 Approach based on multiple collisions It takes into account triple pomeron interactions -equivalente to interaction among gluon- It leads to a shadowing due to coherence effects Shadowing increases with s (~1/x) and decreases with pT (~ mT) Pomeron shadowing model Shadowing corrections: integral of the triple P cross section over the single P one Reduction of multiplicity from shadowing corrections E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

43 The primordial spectrum of particles is altered by interactions with the nuclear matter they traverse on the way out to the detector Rapidity dependence of the nuclear absorption:  abs at mid y <  abs at forward y Usual parameterisation: Nuclear absorption: a cold nuclear matter effect Nuclear absorption: interaction of the preresonant c-cbar pair with spectator nucleons S abs = exp(-  abs L ) nuclear matter densitypath lengthbreak-up cross section Note: some authors consider At high energy: the coherence length is large and the projectile interacts with the nucleus as a whole => Smaller nuclear absorption with growing energies E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Palaiseau 5 March 09

44 EKS shadowing model: intrinsic vs. Vogt’s E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

45 EKS shadowing model: intrinsic & extrinsic vs. Vogt’s E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

46 EPS shadowing model: intrinsic vs. Vogt’s E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

47 EPS shadowing model: intrinsic & extrinsic vs. Vogt’s E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

48 nDSg shadowing model: intrinsic vs. Vogt’s NLO LO E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

49 nDSg shadowing model: intrinsic & extrinsic vs. Vogt’s NLO LO Vogt’s: LO Ours: NLO E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

50 Fit procedure E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

51 Abigail Bickley, August 9, Color Singlet Model: –perturbative creation of the ccbar pair in color singlet state with subsequent binding to J/  with same quantum numbers –hard gluon emission –underpredicts J/  production cross section, predicts no polarization J/  production mechanisms E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09 NRQCD Color Octet Model: –uses NRQCD formalism to describe the non-perturbative hadronization of the ccbar color octet to the color singlet state via soft gluon emission –factorizes the charmonium production into a short distance hard part and a long distance matrix element which is claimed to be universal –Predicts large transverse polarization at high p T (not seen by data) Color Evaporation Model: –phenomenological approach –perturbative creation of the ccbar pair in the color octet state with subsequent non-perturbative hadronization to color singlet via unsuppressed soft gluon emission –predicts no polarization p p J/  soft g c c p p J/  hard g c c

52 Abigail Bickley, August 9, Color Singlet Model: – Color singlet cc pair created in same quantum state as J/  – Underpredicts J/  production cross section by a x10 – Predicts no polarization p p J/  hard g c c Lansberg, Int. J. Mod. Phys. A21 (2006) J/  production mechanisms: CSM E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

53 Abigail Bickley, August 9, NRQCD Color Octet Model: – Includes octet state cc pairs that radiate soft gluons during hadronization – Color octet matrix elements derived from experimental data were expected to be universal, but are not – Predicts large transverse polarization (  >0) at high p T that is not seen in experimental data p p J/  soft g c c Reisert, Beauty 2006 J/  production mechanisms: COM E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

54 Abigail Bickley, August 9, Color Evaporation Model: – Phenomenological approach – Charmonium states formed in proportions determined by experimental data for any cc pair that has a mass below the DD threshold – Uses emission of soft gluons to form J/  – Predicts no polarization Reisert, Beauty 2006 J/  production mechanisms: CEM E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

55 Abigail Bickley, August 9, pQCD involving 3-gluons: – Hadronization mechanism includes channel involving the fusion of a symmetric color octet state with an additional gluon – Successfully reproduces experimental cross section and polarization measurements – Fails to reproduce experimental rapidity distribution => New result! Khoze et al Eur.Phys.J. C39 (2005) J/  production mechanisms: pQCD involving 3-gluons E. G. Ferreiro USC CNM effects on J/  production: intrinsic and extrinsic Moriond 20 March 09

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