Strangeness production in HIC Evgeni E. Kolomeitsev Matej Bel University Banska Bystrica hidden open

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)

Antikaon production KaoS Collaboration in-medium modifications of kaon properties

Kaon production NA49 Collaboration The 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 AGeV NA49 (   K + K - ) and NA50 (    ) experiments rescattering of decay products CERES ’06 in Phi yield via   e + e - agrees with NA49 data NA60 ’08 in AGeV;    Phi yield is higher than in NA49 NA49/NA50 Collaborations

[STAR 200 AGeV: R. Witt JPG 34 (2007) S921] stable particlesresonances Resonance production at RICH Thermal model THERMUS [Wheaton & Cleymans ’04] STAR 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/ ; 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 K 0 evolution calculated from expansion rate production rate annihilation rate calculate from known cross-sections and evolved densities

explicit kinetic calculation: K +, K 0, 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) collisions initial 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) ] 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 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/N c counting Experiment: 3 times smaller than expected from pure octet-singlet mixing:  coupling due to the anomaly need 3 gluons to form a white hadron state

catalytic 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   Y N

traditionalcatalytic 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 t 0 !

Phi production catalytic reactions  N ->  N Catalytic reactions can be competitive if T>110 MeV and t_0>10 fm Red lines scale with t 0 !!!

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

Centrality dependence AGeV [E917 Collaboration, PRC 69 (2004) ] fit coefficients to data point The catalytic reaction contribution can be about 30%-40% for N pp =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) ] 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 hyperons  and  – interesting kaons mesons and hyperons and  and  – very interesting strangeness dynamics kaons mesons and S=1,2 hyperons and  and hyperon resonances – exciting