Hadronization%20by%20Coalescence

1
V. Greco, Texas AM University, Cyclotron
Institute (INFN fellow) C. M. Ko and P. Levai
(KFKI)

• Hadronization by Coalescence

• Hadron spectra (solving proton puzzle)
• Elliptic flow (solving baryon/meson systematic,
• 
  opacity puzzle)

25-28 June, Montreal 2003
2
pions
protons
PHENIX,nucl-ex/0212014

• Fragmentation p/p 0.1
• Jet quenching should affect both

PHENIX, nucl-ex/0304022
Fragmentation is not the dominant mechanism of
hadronization at pT 1-5 GeV !?
p0 suppression evidence of jet quenching
before fragmentation
3
A
p, K, p ...
a
c
B
b
d
ph z pc , z lt1 energy needed to create quarks
from vacuum
A,B p, n (e, e-)
a,b,c,d g,u,d,s.
Parton distribution after pp collision
p/p lt 0.2
B.A. Kniehl et al., NPB 582 (00) 514
( phenomenological kT smearing due to vacuum
radiation)
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Large radiative energy loss in a QGP medium
GLV model, PLB538 (02)282
L/l opacity
P. Levai et al., NPA698(02)631
Non abelian energy loss
weak pT dependence of quenching
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Fragmentation

• Leading parton pT ph z pT
• according to a probability Dh(z)
• z lt 1, energy needed to create quarks
• from vacuum

Coalescence

• partons are already there
• ph n pT ,, n 2 , 3
• to be close in phase space

Even if eventually Fragm. takes over
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fq invariant parton distribution function thermal
(mq0.3 GeV, ms0.47 GeV) quenched minijets
(L/l3.5)
P. Levai et al., NPA698(02)631
fH hadron Wigner function
Dx , Dp coalescence radii
In the rest frame
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Montecarlo Method
We introduce a large number of test partons with
uniform momentum distribution, but with an
associated probability
Same statistics even if dN/d2pT go down by 10-8
T170 MeV
V 900 fm-3 T 170 MeV b(r) 0.5 r/R
L/l3.5
ET 600 MeV
P. Levai et al., NPA698(02)631
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AuAu _at_200AGeV (central)
V. Greco et al., PRL90 (03)202302
nucl-th/0305024 R. Fries et al.,
PRL90(03)202303
nucl-th/0306027
R. C. Hwa et al., PRC66(02)025205
9
L, X from fragm. not included!
X/L ratio larger than STAR data Need of fugacity
gS 0.8 ?! (R. Fries et al., nucl-th/0306027)
r decay
10
AuAu _at_200AGeV (central)
For f, L, X, W fragmentation not included!
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Elliptic flow at RHIC
nucl-ex/0305001
nucl-ex/0210012
Baryons
than Mesons
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Possible solution to the opacity problem
D. Molnar and S.A. Voloshin, nucl-th/0302014
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Elliptic Flow
V. G. et al., nucl-th/0305024
Light quarks v2,q from a fit to p exp. data
v2,p prediction
Strange quarks v2,s 0.7 v2,q (fit to K0 exp.
data)
including r decay effect
14

• Evidence for coalescence as dominant
  hadronization
• mechanism at intermediate pT

• Good description of spectra
• Explanation of p/p , K/L ratio
• (coalescence hide proton quenching up to 5 GeV)
• Elliptic flow of baryons mesons

• Dynamical Description

• QGP minijets partons produced at different
  time
• Coalescence during expansion
• Entropy Energy Conservation (at low pT)
• Radial Elliptic flow self-consistently
  generated
• Hadronic Rescattering (weak !?)