Physics at NICA: the view from LPI RAS NICA round table III 06.11.08 Physics at NICA: the view from LPI RAS A.V. Leonidov

Big goals: Qualitative and quantitative description of deconfined matter and associated features of multiparticle production Description of the features of particle production related to dense strongly interacting medium present in nucleus-nucleus collisions and not present in proton-proton and proton-nucleus ones. Remarks on “elementary” particle source its generalization on high density case. Rescattering of “elementary” sources and transverse and longitudinal spectra in pA and AB collisions. Event-by-event fluctuations of transverse momenta Is the produced dense strongly interacting matter homogeneous on the event-by-event basis?

Gross features of multiparticle production at moderate energies such as transverse spectra and particle yields equivalent in and Transverse spectra are of “thermal” form with a “temperature” T=160-200 MeV. Same value as a coefficient in the Hagedorn spectrum Simplified description: hadronic string with hand-made rules for its breaking and creation of transverse momentum

Fundamental mechanism of particle production is Quantitative picture D. Kharzeev, K. Tuchin (2005) P. Castorina, D. Kharzeev, H. Satz (2007) Fundamental mechanism of particle production is a Hawking-Unruh radiation through the confinement horizon – an interface between open color and hidden phases. Based on close relations between Unruh radiation and Schwinger pair creation mechanism Particle production through quantum tunneling

A fundamental challenge for theory is a generalization of the PKS approach to dense deconfined sources and description of their coexistence with hidden color hadronic phase. At NICA energies: a quark-junction matter? Gluon strings in baryons structured as a junction (have a “Mercedes” form)

Particle spectrum of a fireball at rest: Rescattering and transverse and longitudinal spectra in pA and AB collisions A.L., M. Nardi, H. Satz (1997) Particle spectrum of a fireball at rest: Particle spectrum of a moving fireball:

Multiparticle production proceeds through creation of a string of “elementary” sources shifted in transverse direction due to rescattering : cluster distribution function in longitudinal and transverse rapidity

Longitudinal cluster distribution Works quite well for AB collisions at SPS energies for protons and pions

Pion and nucleon rapidity spectra, Au-Au collisions

Cluster distribution in transverse rapidity Distribution width controlled by : fixed by reproducing pA transverse spectra : number of rescatterings

Pion and nucleon transverse momentum spectra, Au-Au collisions

Reproduces pion and proton transverse spectra in pA and AB collisions at SPS energies very well with T=150 MeV. Problems with kaon transverse spectra Are the kaon spectra anomalous already at pA level? Aren’t we we putting in some flow by hand by using the random walk in transverse rapidity? Random walk in transverse momentum looks more natural from the point of view of Regge phenomenology.

Event-by-event fluctuations in transverse momentum A.L., M. Gazdzicki, G. Roland (1999) Measure of event-by event fluctuations: and Value of calculated in LNZ approach too large at SPS energies in nuclear collisions calcula Fluctuation patterns are much more sensitive to genuine nucleus-nucleus phenomena than spectra What is an event-by-event pattern in transverse momentum fluctuations in pA ?

Is the produced dense strongly interacting matter homogeneous on the event-by-event basis? Early stage of high energy nuclear collisions is inevitably inhomogeneous on the event-by-event basis due to “deconfined” degrees of freedom.

Such a hot-spot structure means that transverse energy density is M. Guylassy, D. Rischke, B. Zhang (1997) Such a hot-spot structure means that transverse energy density is random strongly correlated

Event-by-event versus averaging: Inclusive averaging can be dangerous!

Energy loss: spraying of WW proper field modes (e.g. of M. Kirakosyan, A.L. (2008) Energy loss: spraying of WW proper field modes (e.g. of a constituent quark) due to their interaction with the medium => medium-induced radiative loss

Main challenge: Realistic microscopic description of domains of deconfined dense strongly interacting matter as created in nuclear collision and its incorporation in the MC generators