Antiproton annihilation as a deconfinement process

N¯N annihilation into mesons through the deconfinement stage is analysed. Behaviour of deconfined quark-gluon plasma describes an equation of state, with first order quark and gluon interactions. The effects of pion structure and threshold irregularities are considered.Invited talk to the symposium Mesons and Light Nuclei IV, Bechyn, Czechoslovakia, September 5–10, 1988.     

Fluctuations and correlations as a signal of deconfinement

Event-by-event fluctuations of the K/??, K/p, and p/?? ratio in central AA collisions have been studied for SPS and RHIC energies. The Hadron-String-Dynamical transport approach (HSD) can qualitatively reproduce the measured excitation function for the K/?? ratio fluctuations. The di-jet azimuthal correlations also have been investigated within the HSD model. We found that the suppression of the away-side jet in the hadronic mediumis not enough to explain the experimental data from RHIC. The additional suppression should be attributed to a quark-gluon plasma produced in heavy-ion collisions.     

Holographic prediction for the deconfinement temperature

We argue that deconfinement in anti-de Sitter space models of quantum chromodynamics (AdS/QCD models) occurs via a first order Hawking-Page type phase transition between low temperature thermal AdS and a high temperature black hole. Such a result is consistent with the expected temperature independence, to leading order in 1/Nc, of the meson spectrum and spatial Wilson loops below the deconfinement temperature. As a by-product, we obtain model dependent deconfinement temperatures Tc in the hard- and soft-wall models of AdS/QCD. Our result for Tc in the soft-wall model is close to a recent lattice prediction.     

Quark deconfinement in a semiclassical string-bag model

We describe the effective static quark-(anti)quark colour potential inside hadronic bags in terms of linear strings and semiclassical corrections of order?/r. According to (chromo-) electrostatics we generalize this potential to colour non-neutral configurations making use of the mirror charge method. A thermodynamical study of quark-antiquark pairs and many-quark systems shows a virtually higher order phase transition from the hadronic phase to colour deconfinement. The free plasma stage, furthermore, is achieved only at temperatures much higher thanT _c≈200 MeV. Hadrons increase in size by a factor of 1.5 fromT=0 toT=T _c.     

SU(2) gluodynamics above the deconfinement temperature

A physical model for describing SU(2) gluodynamics above the deconfinement temperature is developed on the basis of the operator-product-expansion method. The properties of the nonperturbative vacuum are parametrized in terms of gauge-invariant gluomagnetic correlation functions. The free energy of the system is calculated for T>T _c. The results obtained within the proposed model for the thermal properties of gluons (energy density, nonideality) are shown to agree with data coming from lattice calculations.     

Measurement-noise maximum as a signature of a phase transition

We propose that a maximum in measurement noise can be used as a signature of a phase transition. As an example, we study the energy and magnetization noise spectra associated with first- and second-order phase transitions by using Monte Carlo simulations of the Ising model and 5-state Potts model in two dimensions. For a finite size system, the total noise power and the low frequency white noise S(f0 and the total noise power vanishes. f(-1)(knee) is approximately the equilibration time.     

Possible evidence for deconfinement in hadron collisions

The collision of hadrons at very high energies produces an entity whose energy density is extremely large resulting in the emission of a large number of hadrons. Though the entity may not have transited into the deconfined parton phase, the very high energy density may cause more than one charged hadron to be emitted at any instant. This yields a new multiplicity distribution, termed the GS distribution which fits the data as well as the popular negative binomial distribution. Neither the GS nor the NB distribution alone agrees with the data beyond 200 GeV, but a weighted sum of GS and NB distributions fits the experimental results exceedingly well. Since the negative binomial distribution arises from the branching of partons, we interpret the increase with energy of the negative binomial component in the weighted sum as the onset of a deconfined phase. The rising cross section for the negative binomial component parallels very closely the inclusive cross section for hadron jets which also is considered a consequence of parton branching.     

Temperature deconfinement in QCD in a magnetic field

Physics of Atomic Nuclei - The quark-hadron QCD phase transition is investigated in a magnetic field. It is shown that the temperature of the phase transition decreases in relation to the case of...     

Same-sign dileptons as a signature for heavy Majorana neutrinos in hadron-hadron collisions

We discuss the possibility of same-sign dileptons as a signature for Majorana neutrinos. The production mechanism is given by a single heavy neutrino production and decay pp → l^±NX → l^±l^±X′. Cross section and distributions are presented for the LHC energies.