LHC signatures for Z` models with continuously distributed mass

We discuss phenomenological consequences of renormalizable Z` models with continuously distributed mass. We point out that one of possible LHC signatures for such nodel is the existence of broad resonance in Drell-Yan reaction $pp \to Z^{`} \to l^+l^-$.Comment: 7 page

Using Higher Moments of Fluctuations and their Ratios in the Search for the QCD Critical Point

The QCD critical point can be found in heavy ion collision experiments via the non-monotonic behavior of many fluctuation observables as a function of the collision energy. The event-by-event fluctuations of various particle multiplicities are enhanced in those collisions that freeze out near the critical point. Higher, non-Gaussian, moments of the event-by-event distributions of such observables are particularly sensitive to critical fluctuations, since their magnitude depends on the critical correlation length to a high power. We present quantitative estimates of the contribution of critical fluctuations to the third and fourth moments of the pion, proton and net proton multiplicities, as well as estimates of various measures of pion-proton correlations, all as a function of the same five non-universal parameters, one of which is the correlation length that parametrizes proximity to the critical point. We show how to use nontrivial but parameter independent ratios among these more than a dozen fluctuation observables to discover the critical point. We also construct ratios that, if the critical point is found, can be used to overconstrain the values of the non-universal parameters.Comment: 16 pages, 5 figures. Version to appear in PRD. Footnote and reference adde

Chirally symmetric but confining dense and cold matter

The folklore tradition about the QCD phase diagram is that at the chiral restoration phase transition at finite density hadrons are deconfined and there appears the quark matter. We address this question within the only known exactly solvable confining and chirally symmetric model. It is postulated within this model that there exists linear Coulomb-like confining interaction. The chiral symmetry breaking and the quark Green function are obtained from the Schwinger-Dyson (gap) equation while the color-singlet meson spectrum results from the Bethe-Salpeter equation. We solve this model at T=0 and finite chemical potential $\mu$ and obtain a clear chiral restoration phase transition at the critical value \mu_{cr}. Below this value the spectrum is similar to the previously obtained one at \mu = 0. At \mu > \mu_{cr} the quarks are still confined and the physical spectrum consists of bound states which are arranged into a complete set of exact chiral multiplets. This explicitly demonstrates that a chirally symmetric matter consisting of confined but chirally symmetric hadrons at finite chemical potential is also possible in QCD. If so, there must be nontrivial implications for astrophysics.Comment: 7 pp; the paper has been expanded to make some technical details more clear; 3 new figures have been added. To appear in PR

Anomalous Multiplicity Fluctuations from Phase Transitions in Heavy Ion Collisions

Event-by-event fluctuations and correlations between particles produced in relativistic nuclear collisions are studied. The fluctuations in positive, negative, total and net charge are closely related through correlations. In the event of a phase transitions to a quark-gluon plasma, fluctuations in total and net charge can be enhanced and reduced respectively which, however, is very sensitive to the acceptance and centrality. If the colliding system experiences strong density fluctuations due, e.g., to droplet formation in a first-order phase transition, all fluctuations can be enhanced substantially. The importance of fluctuations and correlations is exemplified by event-by-event measurement of the multiplicities of $J/\Psi$'s and charged particles since these observables should anti-correlate in the presence of co-mover or anomalous absorption.Comment: revised version to appear in Phys. Rev. C, 5 page

Evolution of fluctuations near QCD critical point

We propose to describe the time evolution of quasi-stationary fluctuations near QCD critical point by a system of stochastic Boltzmann-Langevin-Vlasov-type equations. We derive the equations and study the system analytically in the linearized regime. Known results for equilibrium stationary fluctuations as well as the critical scaling of diffusion coefficient are reproduced. We apply the approach to the long-standing question of the fate of the critical point fluctuations during the hadronic rescattering stage of the heavy-ion collision after chemical freezeout. We find that if conserved particle number fluctuations survive the rescattering, so do, under a certain additional condition, the fluctuations of non-conserved quantities, such as mean transverse momentum. We derive a simple analytical formula for the magnitude of this "memory" effect.Comment: 13 pages, as published, typos corrected, some definitions made more explici

Multiplicity fluctuations in the string clustering approach

We present our results on multiplicity fluctuations in the framework of the string clustering approach. We compare our results --with and without clustering formation-- with CERN SPS NA49 data. We find a non-monotonic behaviour of these fluctuations as a function of the collision centrality, which has the same origin as the observed fluctuations of transverse momentum: the correlations between the produced particles due to the cluster formation.Comment: 16 pages, 4 figures, revte

Finite density QCD with heavy quarks

In the large fermion mass limit of QCD at finite density the structure of the partition function greatly simplifies and can be studied analytically. We show that, contrary to general wisdom, the phase of the Dirac determinant is relevant only at finite temperature and can be neglected for zero temperature fields.Comment: LATTICE98(hightemp), 3 pages, 3 figure

Axial anomaly and magnetism of nuclear and quark matter

We consider the response of the QCD ground state at finite baryon density to a strong magnetic field B. We point out the dominant role played by the coupling of neutral Goldstone bosons, such as pi^0, to the magnetic field via the axial triangle anomaly. We show that, in vacuum, above a value of B ~ m_pi^2/e, a metastable object appears - the pi^0 domain wall. Because of the axial anomaly, the wall carries a baryon number surface density proportional to B. As a result, for B ~ 10^{19} G a stack of parallel pi^0 domain walls is energetically more favorable than nuclear matter at the same density. Similarly, at higher densities, somewhat weaker magnetic fields of order B ~ 10^{17}-10^{18} G transform the color-superconducting ground state of QCD into new phases containing stacks of axial isoscalar (eta or eta') domain walls. We also show that a quark-matter state known as ``Goldstone current state,'' in which a gradient of a Goldstone field is spontaneously generated, is ferromagnetic due to the axial anomaly. We estimate the size of the fields created by such a state in a typical neutron star to be of order 10^{14}-10^{15} G.Comment: 18 pages, v2: added a discussion of the energy cost of neutralizing the domain wall charg

Fluctuations of particle ratios and the abundance of hadronic resonances

In this letter we will argue that the event-by-event fluctuations of the ratio of positively over negatively charged pions provides a measurements of the number of rho and omega mesons right after hadronization. This finding can be utilized to put the hypothesis of chemical equilibration in relativistic heavy ion collisions to a test.Comment: 4 pages. No figure. Uses revtex with prl, aps, and multicol style

Ising-like dynamical signatures and the end-point of the QCD transition line

An increase in the size of coherent domains in the one component $\Phi^4$ field theory under the influence of a uniformly changing external magnetic field near the critical end-point $T_{\Phi}=T_c, h_{\Phi}=0$ was proposed recently as an estimate also for the variation of the chiral correlation length of QCD near its respective hypothetical end point in the $T_{QCD}-\mu_{QCD}$ plane. The present detailed numerical investigation of the effective model suggests that passing by the critical QCD end point with realistic rate of temperature change will trigger large amplitude oscillations in the temporal variation of the chiral correlation length. A simple mechanism for producing this phenomenon is suggested.Comment: 10 pages, RevTeX, 5 figures. Version accepted for publication in PR