arXiv subjects
Publications and source records attributed to V. L. Eletsky.
It is shown, that the correlators of vector and axial-vector currents at finite temperature T in order T^2 reduce to mixing of vacuum VV and AA correlators with universal mixing coefficient given by the parameter ε= T^2/6 F^2_π, unlike the claim in the recent paper by Mallik and Sarkar [1].
The mass shift, width broadening, and spectral density for the $ρ$ and $ω$ mesons in a heat bath of nucleons and pions are calculated using a general formula which relates the self-energy to the real and imaginary parts of the forward scattering amplitude. We use experimental data to saturate the scattering amplitude at low energies with resonances and include a background Pomeron term, while at high energies a Regge parameterization is used. The real part obtained directly is compared with the result of a dispersion integral over the imaginary part. The peaks of the spectral densities are little shifted from their vacuum positions, but the widths are considerably increased due to collisional broadening. Where possible we compare with the UrQMD model and find quite good agreement. At normal nuclear matter density and a temperature of 150 MeV the spectral density of the $ρ$ meson has a width of 345 MeV, while that for the $ω$ is in the range 90--150 MeV.
Our recent work on modifications of rho-mesons formed at the last stage of evolution of hadronic matter produced in heavy ion collisions is summarized. It is found that while the mass shift is on the order of a few tens of MeV, the width and spectral density become so broad that rho may lose its identity as a well defined resonance.
The mass shift and width broadening of $ρ$-mesons produced in heavy ion collisions is estimated. It is found that the mass increases by some tens of MeV but the width becomes large, increasing by 200 MeV at beam energies of a few GeV$\cdot$A and by twice that amount at beam energies of about a hundred GeV$\cdot$A.
The rho-meson mass shift, width broadening, and spectral density at finite temperature and nucleon density are estimated using a general formula which relates the self-energy to the real and imaginary parts of the forward scattering amplitude on the constituents of the medium. We saturate the scattering amplitude at low energies with resonances, while at high energies a Regge approach is taken in combination with vector meson dominance; experimental data is used wherever possible. The main result is that the rho-meson becomes increasingly broad with increasing nucleon density. The spectral density is suppressed in the resonance region 600 < M < 900 MeV and enhanced in the subresonance region M < 600 MeV.
The mass shift and width broadening of rho-mesons produced in heavy ion collisions is estimated using general formulae which relate the in-medium mass shift of a particle to the real part of the forward scattering amplitude of this particle on constituents of the medium and the width broadening to the corresponding cross section. It is found that the mass increases by some tens of MeV but, more importantly, the width becomes large, increasing by several hundred MeV at beam energies of a few GeV per nucleon and by twice that amount at beam energies of about a hundred GeV per nucleon.
The mass shift $Δm_ρ$ and width broadening $ΔΓ_ρ$ of $ρ$ mesons produced in heavy ion collisions is estimated using a general formula which relates the in-medium mass shift of a particle to the real part of the forward scattering amplitude ${\rm Re} f(E)$ of this particle on constituents of the medium and $ΔΓ$ to the corresponding cross section. It is found that in high energy ($E/A \ga 100~$GeV) heavy ion collisions the $ρ$ width broadening is large and $ρ$ (or $ω$) peak could hardly be observed in $e^+e^-(μ^+μ^-)$ effective mass distributions. In low energy collisions ($E/A \sim$ a few GeV) a broad (a few hundred MeV) enhancement is expected at the position of the $ρ$ peak.
The mass shift $Δm_N$ of a nucleon in the finite temperature pion gas is calculated in the case of an arbitrary nucleon momentum. A general formula is used which relates the in-medium mass shift $Δm(E)$ of a particle to the real part of the forward scattering amplitude $Re f(E)$ of this particle on constituents of the medium and its applicability domain is formulated. The mass shift of the nucleon in thermal equilibrium with pion gas is also calculated.
SU(2) Yang-Mills theory at finite extension or, equivalently, at finite temperature is probed by a homogeneous chromomagnetic field. We use a recent modified axial gauge formulation which has the novel feature of respecting the center symmetry in perturbation theory. The characteristic properties of the Z_2-symmetric phase, an extension-dependent mass term and antiperiodic boundary conditions, provide stabilization against magnetic field formation for sufficiently small extension or high temperature. In an extension of this investigation to the deconfined phase with broken center symmetry, the combined constraints of thermodynamic and magnetic stability are shown to yield many of the high temperature properties of lattice SU(2) gauge theory.
We reply to the Comment by Hatsuda and Lee on our recent paper "Meson Masses in Nuclear Matter" (Phys.Rev.Lett. 78, 1010, (1997)). We argue that, contrary to the claim in the Comment, the short distance operator product expansion is not applicable for calculation of meson mass shifts in nuclear matter, since they are determined by long distance physics. We also remark that the suggestion made in the Comment that we overlooked in our paper the mean field description of the mass shifts of low-q mesons is perhaps due to a misunderstanding.
Mass shifts $Δm$ of particles in nuclear matter relative to their vacuum values are considered. A general formula relating $Δm(E)$ ($E$ is the particle energy) to the real part of the forward particle-nucleon scattering amplitude ${\rm Re} f(E)$ is presented and its applicability domain is formulated. The $ρ$-meson mass shift in nuclear matter is calculated at $2\la E_ρ\la 7$ GeV for transversally and longitudinally polarized $ρ$-mesons with the results: $Δm_ρ^T \sim 50$ MeV and $Δm_ρ^L \sim 10$ MeV at normal nuclear density.
Mass splitting between axial and vector $\bar{Q}q$ mesons is considered within the standard QCD sum rules. In agreement with the first experimental data on the $B_1$ meson ($J^P =1^{+}$) we find that the splitting for B is about the same as for D and show that $1/m_Q$ corrections to the meson masses are small.
Correlation functions of QCD currents with quantum numbers of nucleon and $Δ$-isobar are considered at finite temperatures. Corrections of order $T^4$ to the correlators are calculated and interpreted in terms of thermal mass shifts using a QCD sum rules type of argument. In both cases the masses decrease with $T$.
Corrections of order $T^4$ to vector and axial current correlators in QCD at a finite temperature $T<T_c$ are obtained using dispersion relations for the amplitudes of deep inelastic scattering on pions. Their relation with the operator product expansion is presented. An interpretation of the results in terms of $T$-dependent meson masses is given: masses of $ρ$ and $a_1$ start to move with temperature in order $T^4$.
The Goldberger-Treiman relation is shown to persist in the chiral limit at finite temperatures to order $O(T^2)$. The $T$ dependence of $g_A$ turns out to be the same as for $F_π$, $g_{A}(T)=g_{A}(0)(1-T^2/12F^2)$, while $g_{πNN}$ is temperature independent to this order. The baryon octet ${\cal D}$ and ${\cal F}$ couplings also behave as $F_π$ if only pions are massless in the pseudoscalar meson octet.
We calculate the electric screening mass in hot hadronic matter using two different approaches, chiral perturbation theory and the relativistic virial expansion with empirical phase shifts, and compare the results to each other and to a gas of free pions and $ρ$ mesons. We also compute the electric screening mass for noninteracting, charged bosons with mass $m$ on a lattice to study likely finite size effects in lattice gauge theory simulations of continuum QCD. For a lattice of given size, the continuum can be properly represented only for a window in the ratio $T/m$.
Current correlators in QCD at a finite temperature $T$ are considered from the viewpoint of operator product expansion. It is stressed that at low $T$ the heat bath must be represented by hadronic, and not quark-gluon states. A possibility to express the results in terms of $T$-dependent resonance masses is discussed. It is demonstrated that in order $T^2$ the masses do not move and the only phenomenon which occurs is a parity and isospin mixing.
The recent experimental data on $D^{+}-D^{0}$ and $D^{\ast\, +}-D^{\ast\,0}$ mass differences are used as inputs in the QCD sum rules to obtain new estimates on the mass difference of light quarks and on the difference of their condensates: $m_d -m_u =3\pm 1\, MeV$, $\langle\bar{d}d\rangle -\langle\bar{u}u\rangle = -(2.5\pm 1)\cdot 10^{-3}\langle\bar{u}u\rangle$ (at a standard normalization point, $μ= 0.5\, GeV$).