Strangeness production in HICStrangeness production in HICStrangeness production in HICStrangeness production in HIC

Evgeni E. Kolomeitsev

Matej Bel UniversityBanska Bystrica

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1. Why do we love strangeness? Strangeness’ Hall of Fame

2. Temporal aspects of the strangeness production: Where does the strangeness comes from?

3. OZI rule, phi catalysis

Strangeness in HIC: Hall of Fame

most popular pictures (personal choice)

2006

1998

Antikaon production

KaoS CollaborationKaoS Collaboration

in-medium modifications of kaon properties

Kaon production

NA49 CollaborationNA49 CollaborationThe Horn

Difficult to reproduce: transport generators (RQMD, HSD) hydro calculations statistical model

Successful interpretation within the Statistical model of the early stage [Gazdzicki & Gorenstein]

Evidence for a QGP phase transition?

Phi meson puzzle

Difference of phi yields in Pb+Pb@158 AGeVNA49 (K+ K-) and NA50 ()experiments

1997-1999

rescattering of decay products

2006-2008

CERES ’06 in Pb+Au@158AGeVPhi yield via e+e- agrees with NA49 data

NA60 ’08 in In+In@158 AGeV; Phi yield is higher than in NA49

NA49/NA50 CollaborationsNA49/NA50 Collaborations

[STAR Au+Au@ 200 AGeV: R. Witt JPG 34 (2007) S921]

stable particles resonances

Resonance production at RICH

Thermal model THERMUS [Wheaton & Cleymans ’04] STAR vs. Thermal modelSTAR vs. Thermal model

decay-product rescattering

rescattering+regeneration

!

Continuous freeze-out [Grassi, Kadama, Knoll ..]

Why do we like strange particles?

- particles with a “tag” (new quantum number)- mass gap- associated particle production

The strangeness production in a HIC is controlled by

- available energy (energy density) and mass gap (in medium)

- temporal evolution of a HIC (fireball lifetime)

open strangeness

We try hadronic scenario; intrinsically assume non-equilibrium of strangeness.

[B.Tomasik,E.E.K, nucl-th/0512088; EPJC 49 (2007)]

energy vs. time

parameterize the space-time evolution

flavour kinetic calculation with an ansatz for the fireball expansion

a data/experience (HBT, spectra) driven ansatz for expansion

We want to explore various ansatzes and their impact on result

K+ and K0 evolution calculated from

expansion rate

production rate

annihilation rate

calculate from known cross-sections and evolved densities

• explicit kinetic calculation: K+, K0, K*+, K*0 (vacuum properties)• kaons in thermal equilibrium (until decoupling)• chemical equilibrium: non-strange species (, N, , , N*,…)• relative chemical equilibrium: S<0 sector ( K-, , , , )• no antibaryons assumed at these energies

in red: well-defined cross sections

• explore a range of values for the model parameters

• at the end power-law scaling suggested by HBT

acceleration + power-law expansion

initial K+ content estimated from pp (pn, nn) collisionsinitial S<0 species balance strangeness and are relatively equilibrated

fix the final state FO, B,FO, I,FO

obtained from FO analysis [Becattini et al., PRC 69 (2004) 024905]

we choose the initial 0 and the lifetime T

we certainly end up with correct FO, B,FO, I,FO but temperature depends on strangeness production

correct T and

correct K+ abundance correct complete chemical composition

the power-law prescription is realized only towards the end

[FO analysis]

fixed

for a given run

fixed

matching point

some variation

fixed for a given run

exp.data

final temperatures

is close to that of Becattini et al.

the whole final chemical composition is correct!

The K+ horn can be interpreted as a rise and fall of the fireball lifetime

The time needed for a strangeness production is about 15-20 fm/c. In hydro the typical expansion time is <10 fm/c.

hidden strangeness

Okubo-Zweig-Iizuka suppression rule

the interactions of a pure (ss) vector state with non-strange hadrons are suppressed

1/Nc counting

Experiment:3 times smaller than expected frompure octet-singlet mixing: coupling due to the anomaly

need 3 gluons to form a white hadron state

catalytic phi meson productioncatalytic phi meson production

Phi production in reactions involving strange particles is not OZI suppressed!

a new type of the production mechanism

strangeness content does not change

strangeness hides into

YN

traditional catalytic

dominant source of phi considered so far

[Andronic, PBM, Stachel, NPA 772, 167] typical hadronic cross sections

Cross section of catalytic reactions isospin averaged cross sections

Cross sections ~ 1 mb much larger than N-> N

Simple model for strangeness production

follow

Diff.eq. for K^+ production

annihilation neglected, K<<B

follow

thermal weights

scales with t0 !

Phi production

catalytic reactionsN -> N

Catalytic reactions can be competitive if T>110 MeV and t_0>10 fm

Red lines scale with t0 !!!

Centrality dependence

Consider a collision at some fixed energy

reaction rate)

catalytic reactions

# of phis

[Russkikh, Ivanov, NPA 543 (1992)]units of length and time

the mean number of projectile participants fireball volume

# of non-strange particles # of kaons # of strange particle

Centrality dependence

Au+Au@11.7 AGeV

[E917 Collaboration, PRC 69 (2004) 054901]fit coefficients to data point

The catalytic reaction contribution can be about 30%-40% for Npp=A.

Phi rapidity distribution

The distributions can be fitted with a sum of two Gaussian functions placed symmetrically around mid-rapidity

[NA49 Collaboration, PRC 78 (2008) 044907]

the root mean square of the distribution

If are produced in

Assume: the rapidity distributions of particles do not change after some initial stage.The absence or weakness of acceleration and diffusion processes. The collision kinematics is restricted mainly to the exchange of transverse momenta . The rapidity distribution of s produced in the reaction 1+2 -> +X is roughly proportional to the product of rapidity distributions of colliding particle species 1 and 2.

(old)

(new)

Catalytic phi production

can be competitive if T>110 MeV and t_0>10 fm

can be seen in centrality dependence of the phi yield

determine the width of the phi rapidity distribution

What to measure?

just K+ mesons – deadly boring

K+ and K-- mesons – boring

kaons and – check for strangeness conservation

kaons mesons and and – check for strangeness conservation isospin

kaons mesons and hyperonsand – interesting

kaons mesons and hyperons and and – very interesting strangeness dynamics

kaons mesons and S=1,2 hyperons and and hyperon resonances –

exciting