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XLIIIth Rencontres de Moriond : QCD and High Energy Interactions La Thuile , Italy . 14-21 March 2009. Cold nuclear matter effects on J/psi production: intrinsic and extrinsic transverse momentum effects. Elena G. Ferreiro Universidade de Santiago de Compostela, Spain. - PowerPoint PPT Presentation
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XLIIIth Rencontres de Moriond: QCD and High Energy InteractionsLa Thuile, Italy. 14-21 March 2009
Elena G. FerreiroUniversidade de Santiago de Compostela, Spain
Work done in collaboration with F. Fleuret, J-P. Lansberg and A. RakotozafindrabearXiv :0809.4684
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 byZ. Conesa del Valle
On the kinematics of J/ production: two approaches
Investigating two production mechanisms (including pT for the J/:
g+g → J/• intrinsic scheme: the pT of the J/comes from initial partons
g+g → J/+g• extrinsic scheme: the pT 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,Q2)
• J/ kinematics depends on the production mechanism =>
Intrinsic J/ production kinematics
• Intrinsic scheme: 2 → 1 process CEM @ LO g+g → J/
• y, pT can be determined using PHENIX p+p data Phys. Rev. Lett. 98, 232002 (2007)
• Easy to handle : yJ/ and pT
J/directly give x1,2
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 x2 (and x1 in AA)
Q2=(2mc)2+(pT)2=mT
• 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 x2 as a function of (x1, y, pT)
• Information from the data alone – the y and pT spectra– is not sufficient to determine x1 and x2: the presence of a final-state gluon authorizes much more freedom to choose (x1, x2) for a given set (y, PT)
• Models are mandatory to compute the proper weighting of each kinematically allowed (x1, x2)
•We use s—channel cut mechanism Extension of CSM Haberzettl and Lansberg, Phys.Rev.Lett.100,032006 (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 pT
Extrinsic vs intrinsic kinematicsIntrinsic scheme Extrinsic 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, pT): more freedom for xx larger in the extrinsic scheme
• 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
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 :0801.4949
Results for d+Au: rapidity dependence II
First choice:
Intrinsic schemeabs=2.8 mb following PHENIX PRC 77, 024912 (2008)
Extrinsic schemeabs=4.2 mb following NA50 measurements at SPS
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
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
Results for Au+Au: centrality dependenceIntrinsic scheme: Same CNM suppression atforward and central rapidity
Extrinsic scheme: More CNM suppression atforward than central rapidity
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
Extrinsic scheme : RAA @ forward y < RAA @ mid y Hot Nuclear matter effects still needed, but…
Less need for recombination effects
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
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
EKS98 EPS08 nDSg
EKS98 EPS08 nDSg
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
Conclusions…
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
• For the first time:
results @ 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) pT
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 : CEM @ NLO, NRQCD, . . . If they are able calculations for LHC in the extrinsic scheme reproduce low pT dataMore plots in: http://phenix-france.in2p3.fr/software/jin/index.html
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 (CEM @ LO without pT) Fit procedure
• J/ production mechanisms
• Some other results
• Work in progress: RdAu vs Ncoll and RdAu vs pT for EKS98,EPS08, nDSg
Extrinsic vs intrinsic kinematics II
For a given couple(y, pT), x2 is larger inthe extrinsic scheme
We expect different shadowing effectsin both cases
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
Much more freedom to choose (x1, x2) for a given set (y, PT)
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
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
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
Work in progress: really progressing!!!
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
Merci Andry & Fred!
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
EKS98
EKS98
EKS98
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
EPS08
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
Work in progress: EKS98 pT dependence
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
• Extrinsic sheme• Intrinsic sheme
EKS98 EKS98
Work in progress: EPS08 pT dependence
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
• Extrinsic sheme• Intrinsic sheme
EPS08 EPS08
Work in progress: nDSg pT dependence
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
• Extrinsic sheme• Intrinsic sheme
nDSg nDSg
EKS EPS nDS(g) LO
abs 2 abs 2 abs 2
intrinsic 3.20 0.88013 2.11 1.09615 2.21 1.5578extrinsic 3.90 1.09813 3.60 0.53092 3.00 1.3911
Work in progress: fit of abs with EKS, EPS and nDS(g)
intrinsicextrinsic
absabs
2Best fit: extrinsic + EPS08
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
EPS
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 data s-channel cut modelkinematic variables
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
On the kinematics of J/ production: equations III
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
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
s-channel cut contributions
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
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-pT data
s-channel cut contributions: first evaluations
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
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, 171801 (2004)[g(gg)s + Feed-down] Khoze, Martin, Ryskin Stirling, Eur. Phys. J. C39, 163 (2005)
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 :0801.4949 [hep-ph]
EKS and EPS shadowing model• Introduce an initial parameterisation for nuclear parton distributions RA(x,Q2
0) based on a fit to DIS data at Q2
0 = 2.25 GeV2
• The further evolution in Q2 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
fiA(x,Q2) Ri
A(x,Q2) fi(x,Q2) GRV-LO, CTEQ4L
GRV-LO, CTEQ6L1high pT RHIC data at Q20 = 1.69 GeV2
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Palaiseau 5 March 09
EKS shadowing model 1. Introduce an initial parameterisation for
nuclear parton distributions RA(x,Q20) based
on the DIS data at Q20 = 2.25 GeV2
2. Once the nuclear parton distributions are given at an initial scale Q2
0>>Λ2QCD the further
evolution in Q2 is predicted by the DGLAP eqs:
DGLAP eqs: relation between the logarithmic Q2-evolution of the structure functions and the gluon distribution, giving the possibility to calculate the value of ratios at any Q2 if an initial value is known•It is assume that
•at Q2 >Q20 the scale evolution of the nuclear parton densities is purely perturbative
•the initial conditions at Q20 contain the nonperturbative input
•the evolution is made at leading order (LO)
3. The slope of the nuclear parton distributions in Q2 is obtained in this way
No centrality dependence is included in the modelE. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
GRV-LO, CTEQ4L
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, Q20 = 1.69 GeV2
• RHIC high-pT forward-rapidity hadron data suggest a stronger gluon shadowing than obtained in previous global analyses
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
• 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
• 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
Sabs = exp(-abs L )
nuclear matter density path 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
EKS shadowing model: intrinsic vs. Vogt’s
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
EKS shadowing model: intrinsic & extrinsic vs. Vogt’s
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
EPS shadowing model: intrinsic vs. Vogt’s
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
EPS shadowing model: intrinsic & extrinsic vs. Vogt’s
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
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
nDSg shadowing model: intrinsic & extrinsic vs. Vogt’s
NLO
LO
Vogt’s: LOOurs: NLO
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
Fit procedure
E. G. Ferreiro USC CNM effects on J/ production: intrinsic and extrinsic Moriond 20 March 09
Abigail Bickley, August 9, 2007 51
• 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 pT (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 polarizationp
p
J/
soft g
cc
p
p
J/
hard g
cc
Abigail Bickley, August 9, 2007 52
• 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
Abigail Bickley, August 9, 2007 53
• 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 pT 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
Abigail Bickley, August 9, 2007 54
• 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
Abigail Bickley, August 9, 2007 55
• 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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