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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 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 :

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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

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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 =>

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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

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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

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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

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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

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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 :

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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

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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

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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

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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

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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

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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

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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:

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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

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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 )

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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

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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

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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

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

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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

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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

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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

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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

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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

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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

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EKSEPSnDS(g) LO abs 22 22 22 intrinsic extrinsic Work in progress: fit of abs with EKS, EPS and nDS(g) intrinsicextrinsic abs 22 Best fit: extrinsic + EPS08 E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09 EPS

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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

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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

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

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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

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

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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

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

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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)

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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]

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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

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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

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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

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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

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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

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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

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

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

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

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

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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

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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

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

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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

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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

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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

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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

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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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