Upload
waite
View
31
Download
0
Embed Size (px)
DESCRIPTION
Charmonia production at the SPS energies. Marie-Pierre COMETS IPN Orsay, FRANCE SQM2006, UCLA, Los Angeles, USA, March 26-31, 2006. Goal: study anomalous J/ ψ suppression in AA collisions as predicted by Matsui and Satz in case of QGP formation - PowerPoint PPT Presentation
Citation preview
Charmonia production at the SPS energies
Marie-Pierre COMETS IPN Orsay, FRANCE SQM2006, UCLA, Los Angeles, USA, March 26-31, 2006
Goal: study anomalous J/ψ suppressionin AA collisions as predicted by Matsui and Satz in case of QGP formation
Need of a reference: normal absorption in pA
Outline: J/ψ and ψ’ production• pA results at SPS - Comparison with E866 and Hera b experiments
• AA results pT resultsConclusion and open questions
',/ ψψσ JpA
αψψψψ σσ AJpp
JpA ×= ',/',/
J/ψ and ψ’ normal nuclear absorption
NA50 pA at 450 GeV
Glauber fit to J/ψ and ψ’ absolutecross-sections lead to:
ψ’ presents a larger absorption than J/ψ.
018.0888.0015.0928.0 '/ ±=±= ψψ αα andJ
mbandmb absJabs 1.17.78.06.4 '/ ±=±= ψψ σσ
009.0041.0 ±−=Δα
NA50 pA (450 GeV)
In our kinematical domain, charmonium formation time small enough to distinguish the 2 states.
J/ψ and ψ’ normal nuclear absorption
xF = x1 – x2
(p) (A)
J/ψ and ψ’ normal nuclear absorption
Drell-Yan cross section per nucleon-nucleon collision for 2.9 < M < 4.5 GeVFit σ(Drell-Yan) with a power law σ = σ0 · Aα
-> αDrell-Yan = 0.986 0.020Compatible with 1.
In α and σabs :Shadowing (antishadowing)Nuclear absorptionAbsorption by comovers -> negligible ……
DY scales with the number of NN collisions -> reference for J/ψ and ψ’
NA50 pA at 400 GeV
A=208
Q2 = 2.25, 5.39,14.7,39.9,108, and 10000 GeV2
For DY: At SPS xF≈0, MDY≈3 GeV -> x2≈0.11
shadowing valence quark ≈ antishadowing antiquark no nuclear absorption
=>αDY≈1
J/ψ and ψ’ normal nuclear absorption: discussion on α
42 GeV38 GeV29 GeV
J/ψ and ψ’ normal nuclear absorption:discussion on α
J/ψ and ψ’ normal nuclear absorption:
discussion on α If ONLY shadowing in α:σpA = Aα σpp = A RA σpp
Open charm: no nuclear absorption antishadowing ~18% -> αopen charm≈ 1.03
E866Δα due ONLY to shadowing variationbetween xF≈0 (RA≈1.2 x2≈0.09)and xF≈1 (RA≈0.85 x2≈0.007) ≈ 0.06 << 0.25 (measured)Lack of x2 scaling not surprising.
-> other explanations: F. Arléo et al.: scenario with octet state-nucleon collisions at large xF
(Phys. Rev. C61(2000)054906)D. Kharzeev and K. Tuchin:in the CGC framework, J/ψ production is suppressed at large xF due to saturation of gluons in the nuclear wave function.At smaller xF, nuclear absorption plays a significant role; because of formation time effects, it suppresses the J/ψ prod. at SPS stronger than at Fermilab. (hep-ph/0510358)
J/ψ and ψ’ normal nuclear absorption:discussion on α
J/ψ - NA50Glauber fit of all pA data at 450 and 400 GeV, and pp and pd NA51 -> σJ/ψ
abs =4.18 ± 0.35 mb
J/ψ and ψ’ normal nuclear absorption
J/ψ/DY: from pp to PbPb
Average path length L traversed by the cc pair in nuclear matter:appropriate to visualize nuclear absorption in different systems. Peripheral PbPb data points, AND all SU data pointscompatible with normal nuclear absorption. PbPb: departure from normal nuclear absorption at mid-
centrality
J/ψ suppression versus pT
• Ratio to the mostperipheral bin (1)• J/ψ suppression ismainly at low pT and
increases with centrality
• For pT>3.5 GeV/c,
weak centrality dependence
of J/ψ suppression
Ri = Nψ,i(pT)/NDY,i / Nψ,1(pT)/NDY,1
PbPb 158 GeV/c NA50
<p2T> of J/ψ versus centrality
• <p2T> increases linearly with
L• Attributed to parton multiple scattering in the initial state,
even in PbPb?• Phenomenological description <p2
T>(L) = <p2T>pp +αgNL
with <p2T>pp varying with
energy and a common slope αgN = 0.081 ± 0.002 GeV2/c2/fm
<p2T> of J/ψ versus centrality
NA50
Saturation of <p2T> versus ET observed
for central PbPb collisions. S. Gavin and R. Vogt: if broadeningdue only to parton rescattering -> saturation J.P. Blaizot and J.Y. Ollitrault: ina plasma model (scenario in which ALLthe J/ψ are suppressed whatever theirpT over a certain energy density) -> saturation D. kharzeev et al. predict anincrease followed by a decrease withina plasma model
Is pT a « good » variable?
Ψ’/DY: from pp to pPb
Ψ’ - NA50Fit of all pA data at 450 and
400 GeV -> σψ’abs = 7.6 ±1.1 mb 2 regimes: one for proton
and one different for ion-induced reactions Similar centralitydependence for SU and PbPb
J/ψ suppression in InIn collisions
• Anomalous suppression present in lighter nuclear systems?• Variable driving the suppression? NA60 experiment: InIn collisions at 158 GeV/c
Anomalous suppression present in InIn. Onset in the range80 < Npart < 100. Saturation at large Npart.
J/ψ suppression in InIn collisions
The SU, PbPb and InIn data points do not overlap in theL variable, while the suppression patterns are in fairagreement in the Npartvariable.
J/ψ suppression in InIn collisions
None of the models seems to properlyreproduce the observed pattern.
J/ψ absorption by comovers – Capella andFerreiro (Eur. Phys. J. C42(2005)419)
J/ψ dissociation and regeneration in QGP and hadronic phases – Grandchamp,Rapp,Brown(J. Phys. G30(2004)S1355)
c suppression in a percolation modelDigal, Fortunato, Satz (Eur. Phys. J. C32(2004)547)
Conclusions and open questions
AT SPS energies:• J/ψ normal nuclear absorption -> NA60 - pA at 158 GeV nuclear absorption at 158 GeV c nuclear dependence
• (First upsilon results in pA – NA50)• ANOMALOUS J/ψ suppression in PbPb and InIn at √s = 17.8 GeV
Pt ? What at higher energies? -> RHIC (√s = 200 GeV): next talk
-> LHC (√s = 5.5 TeV): to come
Upsilon production in pA collisions
NA50 pA at 450 GeV