Helmut Oeschler

1

Strange Particle Production from SIS up to
LHC

• Helmut Oeschler
• Darmstadt University of Technology

Catania, Sept. 27th, 2006
2
Chemical Freeze Out
J. Cleymans and K. Redlich, PRL 81 (1998) 5284
3

• Production of strange particles from SIS to RHIC
  can rather well be described by SM
• What dynamics behind chemical freeze out?
• Towards LHC
• Where does it fail?
  Sharp maximum in K/p around 30
  AGeV
  Unique Freeze out?
  Centrality dependence!
  
  
  
• What did we learn so far?

4
Freeze-out criteria
J. Cleymans, HO, K. Redlich, S. Wheaton, Phys.
Rev. C73 (2006)
5
Towards LHC
T a b µB2 c µB4 µB d/(1e vs) PRC 73
(2006) At LHC T 170 MeV µB 1 MeV
6
Do we see a trace of the QGP?
7
Or do we just see hadronic ashes?
8
And what to expect at LHC?
Justified by long life time 10 fm/c
I. Kraus, et al., TU Darmstadt, PRC 74 (2006)
and hep-ph/0604237
9
How to get T and µB at LHC?
BUT !
I. Kraus, et al., TU Darmstadt, PRC 74 (2006)
10
At LHC we have the chance to see traces! E.g.
jets, !?
11
Strange-to-non-strange particles as a fct of vs
?S 2 ss/(uu dd)
12
P. Braun-Munzinger, J. Cleymans, HO, K. Redlich,
NPA 697(2002) 902
13
Strangeness Content in a QGP
A. Schmah et al., TU Darmstadt
14
Why do we observe the strangeness content of a
Hadron Gas and not of a Quark Gluon Plasma?
15
R.V. Gavai and S. Gupta, PRD 65 (2002) 094515
?s ?S / ?u
16
Maximum around 30 A GeV
17
Maximum Strangeness around 30 AGeV
?S 2 ss/(uu dd)
P. Braun-Munzinger, J. Cleymans, HO, K. Redlich,
NPA 697(2002) 902
18
Transition from baryonic to mesonic freeze out
J. Cleymans, H.O., K. Redlich, S. Wheaton, Phys.
Lett. B615 (2005)
entropy prop to T3
Meson dominated
Baryon dominated
19
(No Transcript)
20
S. Wheaton et al., to appear
21
Freeze-Out Volume from HBTD. Adamova et al.,
CERES, PRL 90 (2003)
v
v
Argument why freeze out at vs 5 GeV might be
different.
22
Statistical Model for SIS
NiNi
Canonical formulation
J. Cleymans, HO, K. Redlich, PR C59 (1999) 1663
23
K-/K Ratio from SIS up to RHIC
Dynamics understood! K- via strangeness exchange
24
T(K) gt T(K-)

• KaoS Collaboration
• A. Förster et al.,
• PRL 91 (2003)
• AuAu 1.5 A GeV

25
Different freeze out at low inc. energy
KaoS PRC submitted Phys. Rep. in prep. C.
Hartnack, HO, J. Aichelin
26
Expected Centrality Dependence (SM)
Pion density n(p) exp(-Ep/T) Strangeness is
conserved! Kaon density NN N ? K n(K)
exp(-EK/T) g V ? exp-(E?-µB)/T J.
Cleymans, HO, K. Redlich, PRC 60 (1999)
27
Qualitative agreement!
28
AGS AuAu 6 A GeV P. Chung et al., E895
Coll. PRL 91(2003) Updated M (Apart ) a
29
NA49 Data - 158 AGeV PRL
Ingrid Kraus (TU Darmstadt) Talk later this
morning
Corr. vol. NOT prop to Apart
30
Rich information from SIS to RHIC Data rather
well described by SM Needed Understanding
hadronisation Sharp maximum around 30 A GeV in
K/p ratio OPEN Centrality dependence/system
size OPEN Freeze out and phase transition? Tfo
close to the critical temperature Tc ? (Lattice
now well above 175 MeV?)
31
Grazie!
32
(No Transcript)
33
(No Transcript)
34
(No Transcript)
35
(No Transcript)
36
Resonances and Stat. Model
200 GeV pp
200 GeV AuAu

• In pp particle ratios are well described
• In AuAu only stable particle ratios are well
  described

From O. Barannikova, Purdue U., RHIC-AGS meeting,
mai 2004
37
KN Potentials
repulsive KN
attractive K-N
38
K- and K are linked
AuAu and NiNi 1.5 AGeV A. Förster, F.
Uhlig et al., KaoS PRL 91 (2003)
152301 dashed line stat. Model K- and K are
linked via strangeness exchange Law of mass
action J. Cleymans, et al. PLB603(2004)

39
Two Effects!
repulsive KN
attractive K-N
40
Strangeness Exchange at AGS?
AGS L. Ahle et al., PLB 490 J. Klay et al.,
PRC68
PLB603
41
All these observation agree with a hadron gas at
chemical equilibrium What did we learn? Many
arguments that QGP has been formed. 1.What
dynamics causes freeze out? 2. Where do we
observe quark degrees?
42
Charge fluctuations

• proposed by Jeon, Koch, Mueller, Asakawa (2000)
• E.g.

43
Charge fluctuations
PHENIX PRL 89 (2002)
HG 1 QGP 0.2
Bleicher, Jeon, Koch, PRC (2000)
44
And why it doesnt work

• Hadronization (quark recombination) destroys the
  fluctuation

qMD calculation by S. Scherrer
Very recent work from M. Bleicher, et al. Univ.
Frankfurt
time (fm/c)
45
Strangeness Enhancementidea Rafelski Müller 1981
Data WA97 New NA57 Theory S. Hamieh, K.
Redlich A. Tounsi, PL B486 (2000) 61
46
SIS Different chemical freeze out A.
Förster et al.,(KaoS Coll.) PRL 91 (2003) SIS
and AGS Strangeness exchange important J.
Cleymans et al., PLB 603 (2004) Transition from
Baryonic to Mesonic Freeze Out J. Cleymans et
al., Phys. Lett. B 615 (2005) RHIC Statistical
model works very well And beyond!
47
Modification of the Stat. Model

• Instead of strangeness undersaturation factor gS
  Fit parameter
• Alternative small clusters (RC) in fireball (R)
• Chemical equilibrium in subvolumes canonical
  suppression
• RC free parameter

R
RC
48
Model setting with RC

• RHIC clusters still much smaller than
  fireball

49
Above RC 2 fm, nearly grand-canonical !
50

• Observed mainly hadronic properties!
• The old idea of a weakly interacting QGP is
  dead.
• E.g. Lattice calculations show that
• quarks feel hadronic properties well above TC.
• The high strangeness content of a pure QGP
  disappears!
• Cluster formation! The phase space of clusters
• of size 2-3 fm appears as grand-canonique!

51
At LHC particle production will be dominated by
hard processes! Jets! Will this destroy
the simple picture (SM)? More strangeness due to
faster decay from the QGP? Less strangeness due
to fragmentation? Will one observe a hadronic
composition in jets as expected from the two
parameters T and µB ? Interesting already in pp
collisions v2, jet quenching, heavy flavor,
52
Trends reasonably well described by
SM, Especially maxima of K/p, ?-/p, O/ p at
different vs! Above 30 AGeV chemical freeze out
dominated by pions ? unique chemical freeze out ?
possibly separation of chemical and thermal
freeze out Below 30 AGeV interaction dominated
by baryons. individual cross sections might
lead to different chemical freeze-out
conditions. Example K and K- at SIS.
53
Pion Multiplicity
54
(No Transcript)
55
(No Transcript)
56
Mean free path of Kaons and Antikaons
mean free path at ?0 ?(p) 0.3 fm ?(K) 5
fm ?(K-) 0.8 fm
K- absorption by strangeness exchange
reactions K- p ? Y po
K nearly undisturbed messengers
57
Statistical Model for low T
KaoS Data M. Mang et al. Pions/Apart constant
grand-canonical! Kaons/Apart rising
canonical! J. Cleymans, HO, K.
Redlich, PRC 60 (1999)
58
Do the slopes make a consistent picture?
NiNi 1.93 AGeV F. Uhlig, TU DA Diss.
Protons, K and pions cross
K- differ!
T(stat. Model) 74 MeV PRC 59 (1999)
59
Test of the Law of Mass Action J. Cleymans
et al., PLB
? (p Y)/(K- N)
60
Transition
61
v
62
Strangeness Exchange

• If equilibrium, then K- yield just proportional
  to the density of K and the density of pions!
• K proportional to ?! (associate production!)
• Hence K-/K pion density!

63
A. Mischke, Ph.D. thesis
64
(No Transcript)
65
Statistical Model
P. Braun-Munzinger, D. Magestro, K. Redlich, J.
Stachel, PL B518 (2001) updated
66
Statistical Model

67
K and K- at SIS Energies
J. Cleymans,H. O., K. Redlich, PLB 485 (2000)
68
What strangeness content is seen by the f?
69
Statistical Model for SIS
J. Cleymans, H. O., K. Redlich, PRC 59 (1999)
70
Dynamics of K and K-

• K yield established early by the high-density
  phase,
• not changed due to s-conservation (K from the
  interior)
• K slopes (and angular distributions) dominated
  by rescattering
• K- yield established late by ? and p
  concentration
• (K- from the surface)
• Even if K- from a thermal source of ? and p,
  T(K-) is smaller than T(source). Only those K-
  are observed which did NOT had an interaction
• Stat. Model describes the ratios, but does not
  describe T(K- ).

71
(No Transcript)
72
K/K at RHIC
73
Final conclusion
Problems worthy of attack, prove their worth by
hitting back!