А.Б.Курепин – ИЯИ РАН, Москва
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Transcript of А.Б.Курепин – ИЯИ РАН, Москва
А.Б.Курепин – ИЯИ РАН, Москва
Столкновение релятивистских тяжелых ядер и загадка
чармония
VI Марковские чтения15 Мая 2008 г.ОИЯИ, Дубна
Charmonium● 33 years ago: discovery of J/ψ, 21 years ago: Matsui & Satz
- colour screening in deconfined matter → J/ψ suppression
- → possible signature of QGP formation● Experimental and theoretical progress since then
→ situation is much more complicated– cold nuclear matter / initial state effects
● “normal” absorption in cold matter● (anti)shadowing● saturation, color glass condensate
– suppression via comovers – feed down from c, ’– sequential screening (first: c, ’, J/ only well above Tc)– regeneration via statistical hadronization or charm coalescence
● important for “large” charm yield, i.e. RHIC and LHC
NA50 experimental setup
The J/ is detected via its decay into muon pairs
Dimuon spectrometer: Centrality detectors: EM calorimeter (1.1< lab
<2.3)
2.92 < ylab
< 3.92 ZDC calorimeter (lab
> 6.3)
cos CS
0.5 Multiplicity detector (1.9<lab
<4.2)
Pb-Pb 158 GeV/c p – A 400 GeV/c 2000 year Data period Subtargets Number of J/ Target Number of J/ 1995 7 50000 Be 38000 1996 7 190000 Al 48000 1998 1 49000 Cu 45000 2000 1 in vacuum 129000 Ag 41000 W 49000 Pb 69000
J/suppression is generally considered as one of the most direct signatures of QGP formation (Matsui-Satz 1986)
Fit to the mass spectrumFit to the mass spectrum
J/ψ suppression from p-A to Pb-Pb collisions
Projectile
Target
J/
J/ψ production has been extensively studied in p-A, S-U and Pb-Pb collisions by the NA38 and NA50 experiments at the CERN SPS
J/ normal nuclear
absorption curve
• Light systems and peripheral Pb-Pb collisions: J/ψ is absorpted by nuclear matter . The scaling variable - L (length of nuclear matter crossed by the J/ψ) (J/ψ) ~ exp( -abs L)
• Central Pb-Pb collisions: the L scaling is broken - anomalous suppression
4.18 0.35mbJabs
NA60 : is anomalous suppression present also in lighter In-In nuclear systems ? Scaling variable- L, Npart, ε ?
NA60 experimental setup
MUON FILTER
BEAMTRACKER
TARGETBOX
VERTEX TELESCOPE
Dipole field2.5 T
BEAM
IC
not to scale
• Origin of muons can be accurately determined• Improved dimuon mass resolution
Matching in coordinate and in momentum space
ZDC allows studies vs. collision centrality
beam
~ 1m Muon Spectrometer
MWPC’s
Trigger Hodoscopes
Toroidal Magnet
IronwallHadron absorber
ZDC
Target area
High granularity and radiation-hard silicon tracking telescope in the vertex region before the absorber
The normal absorption curve is based on NA50 results. Its uncertainty (~ 8%) at 158 GeV is dominated by the (model dependent) extrapolation from the 400 and 450 GeV p-A data. need p-A measurements at 158 GeV
Comparison of NA50 and NA60 results
An “anomalous suppression” is presented already in In-In
Сomparison J/ results versus Npart
NA50: Npart ftom Et (left) and from Ezdc (right, as in NA60)
J/ suppression in In-In is in agreement with Pb-Pb S-U has different behaviour
’ suppression (NA38, NA50, NA60)
Small statistics in NA60 In-In for ’ (~300) The most peripheral point (Npart~60) – normal nuclear absorption
Preliminary!
abs=8±1 mb
abs~20 mb
Suppression by produced hadrons (“comovers”)
In-In 158 GeV
The model takes into account nuclear absorption and comovers interaction
with σco = 0.65 mb (Capella-Ferreiro) EPJ C42(2005) 419
J/
NC
oll
nuclear absorption
comover + nuclear absorption
Pb-Pb 158 GeV
(E. Ferreiro, private communication)
NA60 In-In 158 GeV
QGP + hadrons + regeneration + in-medium effects
Pb-Pb 158 GeV
B
J/
/D
Y
Nuclear Absorption
Regeneration
QGP+hadronic suppression
Suppression + Regeneration
In-In 158 GeV
Number of participants
fixed thermalization timecentrality dependent thermalization time
The model simultaneously takes into account dissociation and regeneration processes in
both QGP and hadron gas (Grandchamp, Rapp, Brown EPJ C43 (2005) 91)
centrality dependent thermalization time
fixed thermalization time
NA60 In-In 158 GeV
The dashed line includes the smearing due to the resolution
Suppression due to a percolation phase transition
Prediction: sharp onset (due to the disappearance of the c meson) at Npart ~ 125 for Pb-Pb and
~ 140 for In-In
Model based on percolation (Digal-Fortunato-Satz)
Eur.Phys.J.C32 (2004) 547.
Pb-Pb 158 GeV
NA60 In-In 158 GeV
J/transverse momentum distribution J/transverse momentum distribution
Study <pT2> and T
dependence on centrality
NA60 In-In
J/ transverse momentum distributionJ/ transverse momentum distribution
<pT
2> versus L
Fitting : <pT
2>(L) = <pT2>pp + αgN L
<pT2>pp= 1.08 ± 0.02 GeV2/c2
χ2= 0.85 αgN = 0.083 ± 0.002 GeV2/c2fm-1
The observed dependence could simply result from parton initial state multiple scattering
NA50 and NA38 Teff recalculated to 158 GeV vs energy density
In NA38 and NA50 TJ/ ψ
grows linearly with the energy density and with L.
Model dependent recalculation 400 and 200 GeV data to 158 GeV- scaling. For the most central Pb-Pb collisions more flat behaviour could be seen.
T(=0) =( 182)2 MeV Tslope = ( 20.16 1.04) 10-3 fm3
Tslope(cent Pb-Pb)=(8.87 2.07) 10-3 fm3
R(slopes)=2.27 +/- 0.54
J/ψ suppression versus pT.
F=(J/DY>4.2
acc vs p
T in 5 E
T bins
NA50 Pb-Pb 2000
Et bins in GeV
1. 5 - 202. 20 - 403. 40 - 704. 70 - 1005. >100
F
pT
F
Suppression vs pT for p-A, S-U and Pb-Pb
S-U
Pb-Pb 2000
Et bins GeV
5 - 40 40 - 80 80 – 125
p-A
Cronin effect- enhancement at p
T>2 GeV/c
Rcp
Rcp
~Aα
pT (GeV/c)
RC
P
0-1.5% 1.5-5% 5-10% 10-16%
16-23% 23-33% 33-47%
NA60 In-In
The ratios to the peripheral i=1 (47-57%) bin.
Large suppression at low pT, growing with centrality- as in RAA NA60and in Rcp NA50.
Rcp vs pT.
Rcp = (J/ψi(pT)/Ncoll i)/(J/ψ1(pT)/Ncoll1)
J/ in PHENIXJ/ e+e–
identified in RICH and EMCal– |y| < 0.35 – Pe > 0.2 GeV/c– =
J/μ+μ– identified in 2 fwd
spectrometersSouth :
• -2.2 < y < -1.2North :
• 1.2 < y < 2.4– P > 2 GeV/c– = 2
Event centrality and vertex given by
BBC in 3<||<3.9 (+ZDC)
Centrality is calculated to Npart (Ncoll) using Glauber model
Satz
Rapp
Capella
J/,’,c
All models for y=0
nucl-ex/0611020
nucl-ex/0611020
Yan, Zhuang, Xunucl-th/0608010
PHENIX Au-Au data
Without regeneration With regeneration
Models for mid-rapidity Au-Au data
Suppression RAA vs Npart at RHIC.
J/ψ suppression (SPS and RHIC)
J/ψ yield vs Npart, normalized on Ncoll.
Unexpected good scaling. Coherent interpretation-problem for theory.
Work start - : Karsch, Kharzeev and Satz., PRL637(2006)75
For low pT suppression grows with centrality.
J/ψ suppression RAA vs pT at PHENIX.
nucl-ex/0611020
Au-AuarXiv:0801.0220 [nucl-ex]
Cu-Cu
Comparison SPS (NA60) and RHIC (PHENIX) data
The same suppression atlow pT.
Larger values of <pT2> at
RHIC
P
Suppression RAA in Au-Au (PHENIX) vs pT.
J/ψ up to only 5 GeV
Central events
The same RAA for 0, at all pT
and J/ (up to 4 GeV/c).
RAA for is higher.
RAA for direct <1 for high pT.
PHENIX and STAR Cu-Cu data
J/ψ suppression RAA at RHIC.
• Data consistent with no suppression at high pT: RAA(pT > 5 GeV/c) = 0.9 ± 0.2
• At low-pT RAA: 0.5—0.6 (PHENIX)
• RAA increase from low pT to high pT
• Most models expect a decrease RAA at high pT: X. Zhao and R. Rapp, hep-ph/07122407 H. Liu, K. Rajagopal and U.A. Wiedemann, PRL 98, 182301(2007) and hep-ph/0607062 But some models predict an increase RAA
at high pT: K.Karch and R.Petronzio, 193(1987105; J.P.Blaizot and J.Y.Ollitrault, PRL (1987)499
• At SPS energies the J/ shows an anomalous suppression discovered in Pb-Pb and existing already in In-In
• None of the available models properly describes the observed suppression pattern simultaneously in Pb-Pb and In-In
•The shows an anomalous suppression for S-U, In-In and Pb-Pb
•At RHIC energies the J/ suppression is of the same order as at SPS
•None of the theoretical model could describe all the data
•The transverse momentum dependence of J/ψ suppression shows suppression mainly ay low pT, growing with centrality Need information at high pT.
ConclusionsConclusions