arXiv subjects
Publications and source records attributed to W. Florkowski.
We present a calculation of the pi+ pi- invariant-mass correlations and the pion balance functions in the single-freeze-out model. A satisfactory agreement with the data for Au+Au collisions is found.
A calculation of the pion balance functions in a thermal model is presented. The total result consists of resonance and non-resonance parts. A satisfactory agreement with the data on Au+Au collisions at 130 GeV is found.
The pi+ pi- balance function in rapidity is computed in a thermal model with resonances. It is found that the correlations from the neutral-resonance decays are important, yielding about a half of the total contribution, which in general consist of resonance and non-resonance parts. The model yields the pionic balance function a few per cent wider that what follows from the recent data for the Au+Au collisions at 130GeV.
The single-freeze-out model of hadron production is used to describe the particle ratios and the transverse-momentum spectra from RHIC. The emphasis is put on the new measurements done at the highest beam energy of 200 GeV. An overall very good agreement is found between the data and the model predictions. The data for different centrality windows are analyzed separately. A simple scaling of the two expansion parameters of the model with the centrality is found. Interestingly, this scaling turns out to be equivalent to the scaling of hadron production with the number of wounded nucleons.
We show, under general assumptions which are well satisfied in relativistic heavy-ion collisions, that the geometric relation of centrality c to the impact parameter b, namely c ~ pi b^2/sigma_inel, holds to a very high accuracy for all but most peripheral collisions. More precisely, if c(N) is the centrality of events with the multiplicity higer than N, then b is the value of the impact parameter for which the average multiplicity is equal to N. The corrections to this geometric formula are of the order (Delta n(b)/ )^2, where Delta n(b) is the width of the multiplicity distribution at a given value of b, hence are very small. In other words, the centrality effectively measures the impact parameter.
We analyze the spectra of kaonic atoms using optical potentials withnon-local (gradient) terms. The magnitude of the non-local termsfollows from a self consistent many-body calculation of the kaon selfenergy in nuclear matter, which is based on s-wave kaon nucleoninteractions. The optical potentials exhibit strong non-linearitiesin the nucleon density and sizeable non-local terms. We find that thenon-local terms are quantitatively important in the analysis of thespectra and that a phenomenologically successful description can be obtained for p-wave like optical potentials. It is suggested that themicroscopic form of the non-local interaction terms is obtainedsystematically by means of a semi-classical expansion of the nucleusstructure. The resulting optical potential leads to less pronounced non-local effects.
Two examples of ``exotic'' phenomena which become possible and important in the presence of nuclear matter are discussed: omega -> pi pi decay, and rho-omega mixing. Significance of these processes for the low-mass dilepton production in relativistic heavy-ion collisions is indicated.
We confront the hypothesis of chemical freeze-out in ultra-relativistic heavy-ion collisions with the hypothesis of large modifications of hadron masses in nuclear medium. We find that the thermal-model predictions for the ratios of particle multiplicities are sensitive to the values of in-medium hadronic masses. In particular, the $π^+/p$ ratio decreases by 35% when the masses of all hadrons (except for pseudo-Goldstone bosons) are scaled down by 30%.
We analyze subtracted dispersion relations for meson correlators at finite baryon density and temperature. Such relations are needed for QCD sum rules. We point out the importance of scattering terms, as well as finite, well-defined subtraction constants. Both are necessary for consistency, in particular for the equality of the longitudinal and transverse correlators in the limit of the vanishing three-momentum of mesons relative to the medium. We present detailed calculations in various mesonic channels for the case of the Fermi gas of nucleons.
We calculate the width for the omega -> pi pi decay in nuclear medium. Chiral dynamics and low-density approximation are used. At densities around twice the nuclear saturation density we estimate the partial width for the decay of the longitudinal mode to be of the order of a few tens of MeV, and for the transverse mode a few times less.
In the framework of the dipole picture of the BFKL pomeron we discuss a few possibilities of calculating the total $γ^{\star}γ^{\star}$ cross section of the virtual photons. We argue that the existing successful fits of the dipole picture formulae to the measured structure functions $F_2(Q^2,x)$ favor one of the possible extensions of the dipole picture of the BFKL pomeron formulated recently by one of us.
The spatial dependence of static meson correlation functions at finite baryon density is studied in the Nambu -- Jona - Lasinio model. In contrast to the finite temperature case, we find that the correlation functions at finite density are not screened but exhibit long-range oscillations. The observed phenomenon is analogous to the Friedel oscillations in a degenerate electron gas.
Transport equations for quark matter are derived in the mean field approximation for the Nambu -- Jona-Lasinio Lagrangian. Emphasis is put on the chiral limit (zero current quark masses) and the consequences of the chiral symmetry are investigated in detail. Our approach is based on the spinor decomposition of the Wigner function. Kinetic equations for the quark densities and for the spin are derived. We find that the latter is constrained by the requirement of the axial current conservation.
Using a simple kinetic model we study whether a pion condensate can be formed during the hadronization of the quark-gluon plasma in ultrarelativistic heavy-ion collisions. If hadronization proceeds fast and the pion effective mass is close to zero, some pions condense into the zero momentum state. On the other hand, for the pion effective mass equal to the vacuum one or larger no onset of the Bose-Einstein condensation is observed. The constraints on the condensation process coming from the requirement of the entropy increase are discussed in detail.