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IS STRANGENESS STILL STRANGE
AT THE LHC?
Gergely Gábor Barnaföldi
&
Péter Lévai,George Fai, Brian A. Cole, Gábor Papp
Strange Quark Conference 2007
Levoca - Slovakia
24-29. June 2007
Outline
• I. Past of 'strangeness'
– Why 'strange'?
– some historical highlights
• II. Present – recent data
– from SPS to RHIC
– Some theories
• III. Future – theory & experiments
– High-pT particle production
– Hadron ratios in pp and AA collisions at LHC
– Measuring hadron ratios in ALICE HMPID
I. Historical a strange signature
• Why strangeness?
(Wroblewski SQM'04)
– the strange quark mass is close to the critical
temperature Tc
– strange quarks are light enough to be
abundantly present at temperatures above Tc
• Suggested signature for QGP in HIC
– Rafelski & Müller (J. Zimányi & T. Bíró)
– Gazdzicki, Gyulassy, Hwa, Satz, Shuryak, ...
II. K/π ratios vs. √s and rapidity
LHC prediction
√s = 63 AGeV
√s = 200 AGeV
Flavor differences in RdAu and RAuAu
• Nuclear modification
RdAu and RAuAu is
different for K, π and p.
• But rapidity dependence
show a similar pattern
for K, π and p.
• Null effect?
GGB et. al
Eur. Phys.
Jour C, 2007
II. Modelling hadronization in FS
• Basics : NO strangeness in the initial state
– strangeness enhancement
• Low-pT : recombination
– non-perturbative regime
– coalescence model (see. P. Lévai & G. Hamar)
– calculating dN/dy
• High-pT : fragmentation (FF)
– perturbative QCD based parton model
– calculating pT spectra: dN/pTdpT
– hadron ratios in pp and AA collisions at LHC
The pQCD improved parton model
High-pT hadron spectra with AKK FF
K
K0S
p
Λ
Effect of jet quenching on ratios
• Quenching is stronger for
gluon contributions.
• Fragmentation may
evolve this difference.
• Charged K and π ratios
show different
suppression patters at
different L/λ opacities.
• Calculations are with
BKK FFs.
• P. Lévai et al.: Acta. Phys. Hung. & J.
Phys. G 28 (2002) 2`59
Suppression pattern at RHIC
• STAR Preliminary
data
• Strong enhancement at
around 2-4 GeV/c in
experimental data.
• Calculations are for
averaged p/π at L/λ=0
and 4 opacity values.
Suppression pattern at LHC
• Opacity prediction based
on dN/dy estimation in
different centralities
• K/π and p/π presented
with different L/λ values.
• Low and high-pT pattern
seems independent.
• In range 2 GeV/c and 100
GeV/c L/λ plays
significant role.
Hardon ratios at high-pT in ALICE
• High Momentum Particle ID
– HMPID is for extend the range for
ID of K/π, K/p on a track-by-track
basis up to 3 and 5 GeV/c
respectively.
• Very HMPID - VHMPID
– Higher momentum particle ID and
track-by-track is available up to 15
GeV/c (Bari, CERN, UNAM, RMKI )
Summary: at LHC still strange, but at a different level
• Strange quark behaves as 'light' quark at LHC
– Non strange matter (u,d) = strange matter
– Charm will play the 'strange' role
– Smooth K/π, Λ/p and Ξ/π ratios beyond RHIC
• Differences in suppression pattern
– Low-, and very high-pT curves similar
– Low-pT is non perturbative
– High-pT is driven by quark fragmentations
• Future: flavor dependent nuclear modification
and jet-jet correlation.