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

2. 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?

3. 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= 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

4. 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

5. 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)

6. 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:

7. 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

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

9. Pion and nucleon rapidity spectra, Au-Au collisions

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

11. Pion and nucleon transverse momentum spectra, Au-Au collisions

12. 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.

13. 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 ?

14. 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.

15. 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

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

17. 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

18. 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