Impact of Nucleon Mass Shift on the Freeze Out Process

The freeze out of a massive nucleon gas through a finite layer with time-like normal is studied. The impact of in-medium nucleon mass shift on the freeze out process is investigated. A considerable modification of the thermodynamical variables temperature, flow-velocity, energy density and particle density has been found. Due to the nucleon mass shift the freeze out particle distribution functions are changed noticeably in comparison with evaluations, which use vacuum nucleon mass.Comment: submitted to Physical Review

Direction of light propagation to order G^2 in static, spherically symmetric spacetimes: a new derivation

A procedure avoiding any integration of the null geodesic equations is used to derive the direction of light propagation in a three-parameter family of static, spherically symmetric spacetimes within the post-post-Minkowskian approximation. Quasi-Cartesian isotropic coordinates adapted to the symmetries of spacetime are systematically used. It is found that the expression of the angle formed by two light rays as measured by a static observer staying at a given point is remarkably simple in these coordinates. The attention is mainly focused on the null geodesic paths that we call the "quasi-Minkowskian light rays". The vector-like functions characterizing the direction of propagation of such light rays at their points of emission and reception are firstly obtained in the generic case where these points are both located at a finite distance from the centre of symmetry. The direction of propagation of the quasi-Minkowskian light rays emitted at infinity is then straightforwardly deduced. An intrinsic definition of the gravitational deflection angle relative to a static observer located at a finite distance is proposed for these rays. The expression inferred from this definition extends the formula currently used in VLBI astrometry up to the second order in the gravitational constant G.Comment: 19 pages; revised introduction; added references for introduction; corrected typos; published in Class. Quantum Gra

Evaluating chiral symmetry restoration through the use of sum rules

We pursue the idea of assessing chiral restoration via in-medium modifications of hadronic spectral functions of chiral partners. The usefulness of sum rules in this endeavor is illustrated, focusing on the vector and axial-vector channels. We first present an update on constructing quantitative results for pertinent vacuum spectral functions. These spectral functions serve as a basis upon which the in-medium spectral functions can be constructed. A striking feature of our analysis of the vacuum spectral functions is the need to include excited resonances, dictated by satisfying the Weinberg-type sum rules. This includes excited states in both the vector and axial-vector channels. Preliminary results for the finite temperature vector spectral function are presented. Based on a rho spectral function tested in dilepton data which develops a shoulder at low energies, we find that the rho' peak flattens off. The flattening may be a sign of chiral restoration, though a study of the finite temperature axial-vector spectral function remains to be carried out.Comment: 9 pages, conference proceedings from Resonance Workshop at UT Austin, March 5-7 201

Evidence for the absence of regularization corrections to the partial-wave renormalization procedure in one-loop self energy calculations in external fields

The equivalence of the covariant renormalization and the partial-wave renormaliz ation (PWR) approach is proven explicitly for the one-loop self-energy correction (SE) of a bound electron state in the presence of external perturbation potentials. No spurious correctio n terms to the noncovariant PWR scheme are generated for Coulomb-type screening potentia ls and for external magnetic fields. It is shown that in numerical calculations of the SE with Coulombic perturbation potential spurious terms result from an improper treatment of the unphysical high-energy contribution. A method for performing the PWR utilizing the relativistic B-spline approach for the construction of the Dirac spectrum in external magnetic fields is proposed. This method is applied for calculating QED corrections to the bound-electron $g$-factor in H-like ions. Within the level of accuracy of about 0.1% no spurious terms are generated in numerical calculations of the SE in magnetic fields.Comment: 22 pages, LaTeX, 1 figur

In-medium Properties of Hadrons -- Observables

We first briefly review the theoretical basis for calculations of changes of hadronic properties in dense nuclear matter. These changes have usually been investigated by means of relativistic heavy-ion reactions. Here we discuss that observable consequences of such changes can also be seen in more elementary reactions on nuclei. Particular emphasis is put on a discussion of actual observables in photonuclear reactions; we discuss in detail $\eta$- and vector-meson production. We show that photoproduction of $\eta$'s can yield essential information on in-medium properties of the $S_{11}(1535)$ resonance while the $\phi$ meson properties will probably not be accessible through the $K^+K^-$ decay channel. However, for $\omega$ mesons the $\pi^0\gamma$ decay channel, due to its reduced final state interaction, looks more promising in this respect. Completely free of final state interactions is dilepton production in the few GeV range. We show that the sensitivity of this decay channel to changes of hadronic properties in medium in photonuclear reactions on nuclei is as large as in ultrarelativistic heavy ion collisions. Finally we discuss that hadron production in nuclei at 10 -- 20 GeV photon energies can give important information on the hadronization process.Comment: Invited Lecture by U. Mosel at Erice International School on Nuclear Physics 200

Study of in-medium ω\omega meson properties in Ap, pA and AA collisions

We propose to investigate the in-medium properties of vector $\omega$ mesons at the normal nuclear density in Ap(pA) collisions and at higher density in AA collisions at the ITEP accelerator facility TWAC. Using of the inverse Ap kinematics will permit us to study the $\omega$ meson production in a wide momentum interval included the not yet explored range of small meson momenta relative to the projectile nuclei where the mass modification effect in nuclear matter is expected to be the strongest. Momentum dependence of the in-medium $\omega$ meson width will be studied in the traditional pA kinematics. We intend to use the electromagnetic calorimeter for reconstruction of the $\omega$ meson invariant mass by detecting photons from the $\omega \to \pi^{0}\gamma \to 3\gamma$ decay. The model calculations and simulations with RQMD generator show feasibility of the proposed experiment. Available now intensity of the ion beams provides a possibility to collect large statistics and make decisive conclusion about the $\omega$ meson properties at density of normal nuclei. At the second stage of the investigation the $\omega$ meson properties will be studied in AA collisions at higher density. Interpretation of these measurements will be based on the results obtained in Ap(pA) interactions. Further investigation of the in-medium properties of light unflavored and charmed mesons can be performed at ITEP and at GSI(FAIR) where higher ion energies will be accessible in near future.Comment: 26 pages, 10 figures, 2 table

Absorption of phi mesons in near-threshold proton-nucleus reactions

In the framework of the nuclear spectral function approach for incoherent primary proton--nucleon and secondary pion--nucleon production processes we study the inclusive $\phi$ meson production in the interaction of 2.83 GeV protons with nuclei. In particular, the A-dependences of the absolute and relative $\phi$ meson yields are investigated within the different scenarios for its in-medium width as well as for the cross section ratio $\sigma_{pn \to pn{\phi}}/{\sigma_{pp \to pp{\phi}}}$. Our model calculations take into account the acceptance window of the ANKE facility used in a recent experiment performed at COSY. They show that the pion--nucleon production channel contributes distinctly to the $\phi$ creation in heavy nuclei in the chosen kinematics and, hence, has to be taken into consideration on close examination of the dependences of the phi meson yields on the target mass number with the aim to get information on its width in the medium. They also demonstrate that the experimentally unknown ratio $\sigma_{pn \to pn{\phi}}/{\sigma_{pp \to pp{\phi}}}$ has a weak effect on the A-dependence of the relative $\phi$ meson production cross section at incident energy of present interest, whereas it is found to be appreciably sensitive to the phi in-medium width, which means that this relative observable can indeed be useful to help determine the above width from the direct comparison the results of our calculations with the future data from the respective ANKE-at-COSY experiment.Comment: 16 pages, 9 figure

Analysis of the doubly heavy baryons in the nuclear matter with the QCD sum rules

In this article, we study the doubly heavy baryon states $\Xi_{cc}$, $\Omega_{cc}$, $\Xi_{bb}$ and $\Omega_{bb}$ in the nuclear matter using the QCD sum rules, and derive three coupled QCD sum rules for the masses, vector self-energies and pole residues. The predictions for the mass-shifts in the nuclear matter $\Delta M_{\Xi_{cc}}=-1.11\,\rm{GeV}$, $\Delta M_{\Omega_{cc}}=-0.33\,\rm{GeV}$, $\Delta M_{\Xi_{bb}}=-3.37\,\rm{GeV}$ and $\Delta M_{\Omega_{bb}}=-1.05\,\rm{GeV}$ can be confronted with the experimental data in the future.Comment: 10 pages, 4 figure