Rare particle production
1. strangeness
2. open charm
3. quarkonia
Strangeness: Two historic QGP predictions


restoration of c symmetry -> increased production of s
 mass of strange quark in QGP
expected to go back to current
value (mS ~ 150 MeV ~ Tc)
 copious production of ss pairs,
mostly by gg fusion
[Rafelski: Phys. Rep. 88 (1982) 331]
[Rafelski-Müller: P. R. Lett. 48 (1982) 1066]
deconfinement  stronger effect for multi-strange
q  s 
s
 can be built using uncorrelated s qquarks
produced
independent
Ethresin 2m
s  300 MeV
 g  scopious
s
microscopic reactions, faster andgmore
than in hadronic
phase
 NK
Ethres  530 MeV
 strangeness enhancement increasing
content
Ethres  1420
MeV
K  with
 strangeness
N
[Koch, Müller & Rafelski: Phys. Rep. 142 (1986) 167]
Strangeness production depends strongly on baryon density
(i.e. stopping vs. transparency, finite baryo-chemical potential)
Strangeness yields from pp to AA




A strong increase of strange baryon production relative to a
scaled yield as measured in pp was considered a main
signature for the QGP (Rafelski, Mueller (1982))
The main reason is that in particular multi-strange baryon
production in a hadronic medium is a multi-step (and
therefore) slow process, i.e. it is suppressed.
The problem with the simple QGP explanation for an
enhanced cross section arises from a statistical
consideration called ‘canonical suppression in pp
collisions’.
It simply means that strange baryon production in pp
collisions could be suppressed on the basis of the rarity of
strange quarks in the correlation volume that has to be
considered in pp collisions, i.e. the strange quarks have to
be sufficiently abundant in the proper volume in order to
form a strange baryon. So strange baryon production might
simple seem enhanced in AA collisions, because more
strange quarks are produced in the same volume.
Plots of canonical suppression
equilibration volume ?
Tounsi et al.
Strangeness yields from pp to AA
Canonical suppression
increases with increasing
strangeness
 and Xare not flat
Production not well modeled by Npart (correlation volume)
Canonical suppression as function of incident energy
K. Redlich – private communication
Correlation volume:
V= AaNN·V0
ANN = Npart/2
V0 = 4/3·R03
R0 = 1.1 fm
proton radius/
strong interactions
T= 170-177 MeV
a= 1
Particle ratios indicate
T= 165 MeV
a = 2/3 - area drives yields
a = 1/2 - best fit
a
1
2/3
1/2
Solid – STAR
Open – NA57
Strangeness enhancement:
Wroblewski factor evolution
Wroblewski factor
Lines of constant lS
PBM et al., hep-ph/0106066
total
mesons
baryons
hidden strangeness mesons
<E>/<N> = 1 GeV
dependent on T and mB
dominated by Kaons
I. Increase in
strange/non-strange
particle ratios
II. Maximum is
reached
III. Ratios decrease
(Strange baryons
affected more strongly
than strange mesons)
Peaks at 30 A GeV in AA collisions due to strong mB dependence
Strangeness enhancement
K/ – the benchmark for abundant strangeness production:
K+/K-
K/

[GeV]
New machines to explore the high
density regime
A new European heavy-ion
machine (FAIR) to be ready
in 2012.
Low energy running at RHIC
(2009-2012)
new European
‘can-do-all’ facility
(FAIR @ GSI)
Heavy flavor production
Flavor dependence of yield scaling
up, down
strange
charm
PHENIX D-mesons
• participant scaling for light quark hadrons (soft production)
• binary scaling for heavy flavor quark hadrons (hard production)
• strangeness is not well understood (canonical suppression in pp)
Charm cross-section measurements in
pp collisions in STAR
Charm quarks are believed to be produced at
early stage by initial gluon fusions
 Charm cross-section should follow number of
binary collisions (Nbin) scaling

Measurements
direct D0
(event mixing)
c→m+X
(dE/dx, ToF)
c→e+X
(ToF)
c→e+X
(EMC)
pT (GeV/c)
0.1-3.0
0.17-0.25
0.9-4.0
 1.5
constraint
s, ds/dpT
s
s, ds/dpT
ds/dpT
LO / NLO / FONLL?
A LO
calculation gives you a rough estimate of the cross section
A NLO calculation gives you a better estimate of the cross section and a rough
estimate of the uncertainty
Fixed-Order plus Next-to-Leading-Log (FONLL)



LO:
Designed to cure large logs in NLO for pT >> mc where mass is not
relevant
Calculations depend on quark mass mc, factorization scale mF (typically
mF = mc or 2 mc), renormalization scale mR (typically mR = mF), parton
density functions (PDF)
Hard to obtain large s with mR = mF (which is used in PDF fits)
FONLL RHIC (from hep-ph/0502203 ):
400
NLO
381
s cFONLL

256
m
b
;
s

244
c
-146
cc
-134 mb
99
s bbFONLL 1.87-00..67
mb
NLO:
CDF Run II c to D data (PRL 91,241804 (2003):
 The non-perturbative charm fragmentation
needed to be tweaked in FONLL to describe
charm. FFFONLL is much harder than used
before in ‘plain’ NLO  FFFONLL ≠ FFNLO
RHIC: FONLL versus Data
s cc (STAR from D 0  eTOF  m )
s cc ( FONLL)
Matteo Cacciari
(FONLL):
 factor 2 is not a
problem
hep-ex/0609010
 factor 5 is !!!

nucl-ex/0607012



Spectra in pp seem to require a bottom contribution
High precision heavy quark measurements are tough at RHIC energies.
Need direct reconstruction instead of semi-leptonic decays. Easy at LHC.
Reach up to 14 GeV/c D-mesons (reconstructed) in pp in first ALICE year.
Heavy Flavor in AA collisions
Theory: there are two types of e-loss: radiative and collisional,
plus dead-cone effect for heavy quarks
Flavor dependencies map out the process of in-medium modification
A.) charm flows like light quarks
strong elliptic flow of electrons from D meson
decays → v2D > 0
 v2c of charm quarks?
 recombination Ansatz: (Lin & Molnar,
PRC 68 (2003) 044901)
m
m
v2D ( pT )  av2q ( u pT )  bv2q ( c pT )  v2e
mD
mD



universal v2(pT) for all quarks
simultaneous fit to , K, e v2(pT)
2σ
1σ
4σ
a=1
b = 0.96
c2/ndf: 22/27
χ2 minimum result
D->e
B.) charm quenches like light quarks
submitted to PRL (nucl-ex/0607012)
charged hadrons
Describing the suppression is difficult for models
How difficult ?

RAA of electrons from heavy flavor decay



radiative energy loss with typical gluon
densities is not enough
(Djordjevic et al., PLB 632(2006)81)
models involving a very opaque medium
agree better (qhat very high !!)
(Armesto et al., PLB 637(2006)362)
collisional energy loss / resonant elastic
scattering
(Wicks et al., nucl-th/0512076,
van Hees & Rapp, PRC 73(2006)034913)
heavy quark fragmentation and dissociation
in the medium
→ strong suppression
for charm and bottom
(Adil & Vitev, hep-ph/0611109)
Useful to constrain medium viscosity h/s….




Simultaneous description of
STAR & PHENIX R(AA)
and PHENIX v2 for charm.
(Rapp & Van Hees, PRC 71, 2005)
Ads/CFT == h/s ~ 1/4 ~ 0.08
Perturbative calculation of D (2t) ~6
(Teaney & Moore, PRC 71, 2005)
== h/s~1
transport models require
 small heavy quark
relaxation time
 small diffusion coefficient
DHQ x (2T) ~ 4-6
 this value constrains the
ratio viscosity/entropy
h/s ~ (1.3 – 2) / 4
 within a factor 2 of
conjectured lower
quantum bound
 consistent with light hadron
v2 analysis
 electron RAA ~ 0 RAA at high pT - is bottom suppressed as well?

c-cbar suppression
Lattice QCD calculation
c
Color Screening
rs
cc
Cold Matter Path = L
c
PHENIX signals in pp
Proton-Proton Data
Proton-Proton Data
PHENIX signals in AuAu central
J/y  ee
AuAu 10% Central
S/B ~ 0.25
J/y  mm
AuAu 20% Central
S/B ~ 0.1
Detailed event mixing background subtraction, modified log
likelihood fitting, and careful systematic error determination.
The Unadulterated Data!
nucl-ex/0611020 submitted to PRL
Ratio Blue / Red
Nuclear Suppression Factor
Still Just the Data!
Collision Centrality ( More Central)
Simple Theory
Assume J/y is at rest and a static medium (no time evolution).
If local density (dET/dy or dN/dy) > threshold then no J/y.
J/y
Note it does include a Woods-Saxon Density Profile !
Predictions:
(1) Much larger J/y suppression at RHIC compared with SPS.
(2) Larger J/y suppression at mid-rapidity where local density
is highest.
Statistical and Systematic Comparison
PHENIX data at 200 GeV is quite
surprisingly compatible with
NA50 data at 17.2 GeV !
PHENIX data at forward
rapidity shows a
significantly stronger
suppression.
Similar Trends (?)
Cancelling Effects ?
Original J/y suppressed.
Grandchamp, Rapp, Brown
PRL 92, 212301 (2004)
nucl-ex/0611020
R. Rapp et al. (for y=0) PRL 92, 212301 (2004)
R. Thews (for y=0) Eur. Phys. J C43, 97 (2005)
N. Xu et al. (for y=0) nucl-th/0608010
Bratkovskaya et al. (for y=0) PRC 69, 054903 (2004)
A. Andronic et al. (for y=0) nucl-th/0611023
And many other calculations….
Compensated for by
recombination of
originally uncorrelated c
and c.
Open Charm Input
Any recombination model must also match the charm
distribution.
nucl-ex/0611018 submitted to PRL
J/y
Note that J/y get contributions
from charm at ½ J/y pT.
And charm yields electrons
with ~ 0.7 x D meson pT.
Non-photonic electrons
(from heavy flavor decay)
Heavy Outlook
Exciting new results on heavy quarkonia at RHIC are of
major import and potentially profound, though not easily
digested.
On the experiment side, we must have measurements of
multiple states (J/y, y’, cC, U(1s,2s,3s)) !
state
Mass [GeV}
B.E. [GeV]
Td/Tc
J/y
3.096
0.64
---
cc
3.415
0.2
0.74
y'
U(1s)
3.686
0.05
0.15
9.46
1.1
---
cb
9.859
0.67
---
U(2s)
10.023
0.54
0.93
cb'
10.232
0.31
0.83
U(3s)
10.355
0.2
0.74
Theory needs full dynamical evolution matching both open
and closed charm in a consistent picture (good progress
here). Less drawing lines through points.
Exciting future with more results from SPS, RHIC, and LHC!