some critical phenomena in aa and pp collisions and percolation string model
DESCRIPTION
Some critical phenomena in AA and pp collisions and percolation string model. G.A. Feofilov, O.A. Kochebina Reporter O.A. Kochebina. St. Petersburg State University. The 5th International Nordic "LHC and Beyond" Workshop "The First LHC Physics and Major Spin-Offs", 9 June 2010. Outline. - PowerPoint PPT PresentationTRANSCRIPT
G.A. Feofilov, O.A. Kochebina
Reporter O.A. Kochebina
The 5th International Nordic "LHC and Beyond" Workshop "The First LHC Physics and Major Spin-Offs", 9 June 2010
St. Petersburg State University
2
3
Phase transitions See NA61. Physics goals. https://na61.web.cern.ch Phases of strongly
interacting matter in AA collisionsPhases of water
The phase diagram of water is well established
butthe properties of the
transition between hadrongas and quark-gluon plasma
still have to be uncovered
1st order phase transitioncritical point
Shape changes little from peripheral to the transition
83-94% 55-65%
ηΔ width
STAR PreliminarySTAR Preliminary
Smaller change from transition to most central
Low-pT manifestation of the “ridge”
0-5%
STAR Preliminary
Variation of low-pT “ridge” with centrality (Npart).(pt> 0.15 GeV/c )
[1]Anomalous centrality variation of minijet angular correlations in Au-Au collisions at 62 and 200 GeV from STAR. M. Daugherity. QM2008.
4
Large change within ~10%
centrality
46-55%
STAR Preliminary
The data showed a sharp transition at some definite energy-dependent centrality:growing of peak amplitude and pseudorapidity stretching of width.
Example New threshold (?) phenomena in AA collisions observed by STAR [1]
5
Peak Amplitude
Npart Npart
NpartPeak η Width
STAR PreliminarySTAR Preliminary200 GeV62 GeV
refρ
Δρ
Peak η Width
200 GeV “Critical value” Npart≈40
62 GeV“Critical value” Npart≈90
Sd
dNch /2
3~
Transverse Particle Density
~
STAR Preliminary
STAR Preliminary
200 GeV62 GeV
~
A sudden increase of the peak amplitude and η width of the near-side low p_t ridge were found at an energy-dependent centrality point at definite number of participating nucleons Npart.
Same-side gaussian peak amplitude, width. Points show eleven centrality bins for each energy (84-93%, 74-84%, 65-74%, 55-65%, 46-55%, 37-46%, 28-37%, 19-28%, 9-19%, 5-9%, and 0-5%) transformed to tranvserse density.
22,06,2~ fmcrit
Anomalous centrality variation of minijet angular correlations in Au-Au collisions at 62 and 200 GeV from STAR. M. Daugherity. QM2008.
Variation of low-pT “ridge” with centrality (Npart).
S
Motivation(theory) Application of string model. Investigations of the charged particles long-range multiplicity correlations, measured for well separated
rapidity intervals, can give us information on the number of emitting centers and hence on the fusion of colour strings[2,3].
6
[2] M.A.Braun, C.Pajares and V.V.Vechernin, Low pT Distributions in the Central Region and the Fusion of Colour Strings, Internal Note/FMD ALICE-INT-2001-16 [3] А. Абрамовский, О.В. Канчели// Письма в ЖЭТФ, т.31, 566, 1980
Fig.1. Quark-gluon strings and schematics for studies of Long-Range Correlations[2]
String model. Estimate of string percolation parameter.
With growing energy and/or atomicnumber of colliding particles, the number of strings grows and they start to overlap, forming clusters, new type of particle emitting source. At a critical density a macroscopic cluster appears that marks the percolation phase transition.[3]
- number of strings, πr02 string transverse area, S overlap area of two nucleons.
r0=0,2-0,3 fm – change of string radius value results in different percolation parameter
NStr
[4] J.Dias de Deus and A. Rodrigues// Phys. Rev. C 67, 064903 (2003)[3] C. Pajares // arXiv:hep-ph/0501125v1 14 Jan 2005
)(
)()(
20
bS
rbNb str
7
ηс= 1,15([4])
)(/)()( 20 partpartstrpart NSrNNN
Percolation parameter:
S
?strN
8
]8[)1()(partcoll
ppstrstr NxNxNN
Number of strings
x – parameterNstr(pp) - the number of strings in pp collisionNcoll – number of nucleon - nucleon collisionsNpart – number of nucleon participants
Npart, Ncoll - from MC calculation [9]Nstr(pp) – theoretical estimates [8]x - ?
ValentSeastr NNN
[8]V.V. Vechernin, R.S. Kolevatov, 2007, published in Yadernaya Fizika, 2007, Vol. 70, No. 10, pp. 1858–1867.[9]G.Feofilov,A.Ivanov //Journal of Physics: Conference Series 5 (2005) 230–237
9
New! Our calculation
S-?SrN str /2
0
Percolation parameter
Sd
dNch /2
3~
Transverse particle density
22062 fmcrit ,,~15,1crit
crit
crit
~
Percolation model parameters at the “critical“ point
xr
dydN
N
ch
crit
critcritstr
2
0
23
~
Percolation parameter Percolation parameter η vs. number of participants: vs. number of participants:
[7] G.Feofilov,A.Ivanov, “Number of nucleon‐nucleon collisions vs. energy in modified Glauber calculations”,Journal of Physics: Conference Series 5 (2005) 230–237]
)(/)()( 20 partpartstrpart NSrNNN
10
GMNstr ≈ 275Ns ≈ 220
Ncoll ≈ 150
x=0,39±0,07
MGM (momentum loss)Nstr ≈275Ns ≈ 216
Ncoll ≈ 168
x=0,34±0,06
√s= 62 GeV, Au+Au
______ - GM - - - - - - - MGM[7]
“Critical value” Npart ≈ 90ηсrit = 1,15
ρсrit = 2,6 GeV/fm-2
r0=0,28 fm
Example of calculation
partcollpp
strstr NxNxNN )1()(
11
Extrapolation of percolation model parameters for energy Extrapolation of percolation model parameters for energy 17,3 GeV and 3500 GeV 17,3 GeV and 3500 GeV
tsecba /
Parameter Value Error
d 1,00 0,08
c -0,8 0,1
t 293 107
Parameter Value Error
d 0,80 0,05
c -0,61 0,07
t 296 91
partcollpp
strstr NxNxNN )1()(
GM
MGM
√s= 17,3 GeV => x=0,18±0,02√s= 3500 GeV => x=1,0±0,3
√s= 17,3 GeV => x=0,19±0,02√s= 3500 GeV => x=0,8±0,4
62 GeV 200 GeV
12
Percolation parameter vs. number of participants:
It is possible to try to search for the onset of the near-side low p_t “ridge” in the very central Pb+Pb at 17,3 GeV(SPS) or AuAu collisions 19,6 GeV (RHIC) andin very peripheral collisions or maybe even in pp collisions at LHC energies.
13
Sd
dNch /2
3~
SrN str /20
14
ρ = 0,60+ 1,75 η
From experimental data [11] for dNch/dy
√s, GeV ρ, GeV/fm-2 η Nstr
7000 6,2±0,2 3,2±0,3 18±22360 4,8±0,2 2,4±0,2 14±1900 3,9±0,2 1,9±0,2 11±1
Sd
dNch /2
3~
SrN str /20
Obtained Nstr was checked and has agreement at theoretical predictions for Nstr[12] (for energy 17,3 GeV, 200 GeV, 900GeV)
ValentSeastr NNN
[11] ALICE Collaboration: arXiv:1004.3034[hep-ex], arXiv: 1004.3514[hep-ex][12]N. Armesto, D. Derkach and G. A. Feofilov, Phys. At. Nucl. 71 (2008) 2122–2131
• The hypothesis of percolation transition looks reasonable in the description of the onset of the near side low-pt ridge phenomenon at RHIC energies.
• it is possible to try to search for the onset of the “near-side low p_t “ridge” phenomenon” in the very central Pb+Pb at 17,3 GeV(SPS) or in Au+Au at 19.6 GeV (RHIC).
•At the LHC energy one may expect the observation of the low p_t ridge phenomenon in ALL centrality classes and the onset in peripheral PbPb or pp collisions.
•The method for obtaining the number of sea strings following the concept of valent and sea strings is checked on the data of the ridge onset in Au+Au collisions at RHIC.
• The method for finding the total number of strings for pp collisions at LHC energies is proposed.
• The hypothesis of percolation transition looks reasonable in the description of the onset of the near side low-pt ridge phenomenon at RHIC energies.
• it is possible to try to search for the onset of the “near-side low p_t “ridge” phenomenon” in the very central Pb+Pb at 17,3 GeV(SPS) or in Au+Au at 19.6 GeV (RHIC).
•At the LHC energy one may expect the observation of the low p_t ridge phenomenon in ALL centrality classes and the onset in peripheral PbPb or pp collisions.
•The method for obtaining the number of sea strings following the concept of valent and sea strings is checked on the data of the ridge onset in Au+Au collisions at RHIC.
• The method for finding the total number of strings for pp collisions at LHC energies is proposed.
15
16
17
18
Ncoll depends on the model:1.Classical Glauber model (GM)2.Modified Glauber model (MGM) (takes into account moment losses)[7]
Systematic uncertainties:1. String radius (r0=0,2-0,25 fm)2. Estimate of overlap area S 3. Estimate of Ncoll (Classical or Modified Glauber )
[7] G.Feofilov,A.Ivanov //Journal of Physics: Conference Series 5 (2005) 230–237
19
ηсrit= 1,15r0=0,2 fm
20/)()()( rNSNNN partpartpartstr
“Critical value” Nstr
New!
b, fm
Npart
S(bcrit)
∙ - sphere nuclear shape∙ - WS nuclear shape
ηсrit /πr0 = Nstr/S(bcrit)
Our calculation
Percolation parameter vs. number of participants:Percolation parameter vs. number of participants:
[7] G.Feofilov,A.Ivanov, “Number of nucleon‐nucleon collisions vs. energy in modified Glauber calculations”, Journal of Physics: Conference Series 5 (2005) 230–237]
20
“Critical value” Npart ≈ 40ηсrit= 1,15r0=0,2 fm
√s= 200 GeV, Au+Au
GMNstr ≈ 300Ns ≈ 460
Ncoll ≈ 50
a=5,0±2,2
MGMNstr ≈ 360Ns ≈ 260
Ncoll ≈ 40
a=6,7±2,9
)(/)()( 20 partpartstrpart NSrNNN collpartstr aNNN
______ - r0=0,2 fm (GM)
- - - - - - - r0=0,25 fm (GM)
..-..-..- - line r0=0,2 fm (MGM)[7]
21
collpartstr aNNN
62 GeV a = 2,9±0,8
200 GeV a = 5,0±2,2
Preliminary
tsecba /Extrapolation of percolation model parameters to lower Extrapolation of percolation model parameters to lower
energy.energy.
SVstr NNN
17,3 GeV a=1,2±0,1
17,3
Parameter Value Error
d 5,44 0,25
c -5,38 0,24
t 81 1017,3
Parameter Value Error
d 7,40 0,27
c -7,35 0,26
t 86 8
62 GeV a = 3,8±0,8
200 GeV a = 6,7±2,9
Preliminary
17,3 GeV a=1,4±0,1
Classical Glauber model Modified Glauber model
22
[8]Terence J. Tarnowsky*, Brijesh K. Srivastava, Rolf P. Scharenberg (for the STAR Collaboration)/ arXiv:nucl-ex/0606019v2 10 Apr 2007
Au+Au, 200 GeV
Au+Au, 62 GeV
Percolation parameter vs. number of participants:Percolation parameter vs. number of participants:
Au+Au62 GeV Npart ≈ 90
200 GeV Npart ≈ 40ηсrit= 1,15
Au+Au62 GeV Npart ≈ 75
200 GeV Npart ≈ 20ηсrit= 1,175
______ - r0=0,2 fm (GM)
- - - - - - - r0=0,25 fm (GM)
..-..-..- - line r0=0,2 fm (MGM)[7]
[7] G.Feofilov,A.Ivanov,”,Journal of Physics: Conference Series 5 (2005) 230–237
Our estimates based on RHIC experimental data
Theoretical estimates made by Tarnowsky (2007)
23
Near-side low p_t “ridge” in dihadron correlations that were studied recently in Au+Au collisions at the collision energies √s= 62 and 200 GeV, demonstrate a number of interesting features as a function of collision centrality, transverse momentum and particle composition
New threshold (?) phenomena in AA collisions
Ridge: see J. Putschke et al. [STAR], J. Phys. G 34, S679 (2007). Low-p_t near side ridge: see Daugherity report at QM2008
Onset of manifestation of the near-side low p_t “ridge” (pt> 0.15 GeV/c )
refρ
Δρ
refρ
Δρ Pair densities : Δρ ≡ ρsib−ρref, where ρsib is sibling pair densities, ρref - the uncorrelated reference from different events measures
),( 21 pp
Ref.:[1] M. Daugherity for the STAR Collaboration//arXiv:0806.2121v2 [nucl-ex] 13 Jun 2008; M. Daugherity// Report on QM2008.[2] J. Putschke et al. [STAR], J. Phys. G 34, S679 (2007). [3] Adams J et al (STAR Collaboration) 2006 Phys. Rev. C 73 064907[4] Adams J et al (STAR Collaboration) 2007 J. Phys. G: Nucl. Part. Phys. 34 799[5] Jana Bielcikova, Acta Physica Polonica B Vol. 1 Proceedings Supplement No 3, (2008) 611-614
~
24
]1[2,06,2~ 2 fmcrit
r0 =0.2 fm
Modified Glauber model
~Preliminary
17,3 GeV a= 1,4±0,162 GeV a= 3,8±0,8200 GeV a= 6,7±2,9
623~ 2 forfmcrit
Percolation parameter vs. Transverse Particle Density
~ ~
Sd
dNch /~
2
3
PHOBOS Collaboration, B. B. Back et al., Phys. Rev. C65, 061901 (2002); 70, 021902 (2004).PRL 94(2005) 022002
d
dNch
obtained in our calculations
PbPbGeVs ,3,17
r0=0,2 fm
We obtain a=3,0±0,5
)(/)()( 20 partpartstrpart NSrNNN
Percolation parameter vs. number of participant (J/psi).
collpartstr aNNN
[7] CERN–2005–005 arXiv:hep-ph/0412158v2 26 Jul 2005, p. 428
“Critical value” Npart≈110[7]
25
G.Feofilov, O. Kochebina. J/psi suppression, percolation model and the critical energy density in AA collisions at SPS and RHIC energies with the account of centrality.//Baldin ISHEPP XIX. Dubna, Oct 2, 2008
AuAuGeVs ,200
Percolation parameter vs. number of participant:Systematic uncertainties
Uncertainties r0 (0.25 fm)Upper estimate
Modified Glauber[11] estimateUncertainties Nstr
Systematic uncertainties:1. Nstr2. String radius3. S – overlap area
[11] G.Feofilov,A.Ivanov, “Number of nucleon nucleon collisions vs. energy in modified Glauber calculations”, Journal of ‐Physics: Conference Series 5 (2005) 230–237]
Experimental data for J/Psi suppression
“Critical value” Npart ≈ 50
All parameters is the same
)(/)()( 20 partpartstrpart NSrNNN
collpartstr aNNN
r0=0,2 fma= 4,2±0,5
26
crit~