Nucl.Phys.A764:338-370,2006 Invariant mass spectra of di-electrons stemming from bremsstrahlung processes
are calculated in a covariant diagrammatical approach for the exclusive
reaction D p \to ...p_{\rm sp} n p e^+ e^- with detection of a forward spectator
proton, p_{sp}. We employ an effective nucleon-meson theory for parameterizing
the sub-reaction n p \to n p e^+ e^- and, within the Bethe-Salpeter formalism,
derive a factorization of the cross section in the form {d\sigma_{D p \to
p_{\rm sp} n p e^+ e^-}}/{dM}= {d\sigma_{n p \to n p e^+ e^-}}/{dM} \times
kinematical factor related solely to the deuteron (M is the e^+ e^- invariant
mass). The effective nucleon-meson interactions, including the exchange mesons
\pi, \sigma, \omega and \rho as well as excitation and radiative decay of
\Delta(1232), have been adjusted to the process pp \to pp e^+ e^- at energies
below the vector meson production threshold. At higher energies, contributions
from \omega and \rho meson excitations are analyzed in both, NN and Dp
collisions. A relation to two-step models is discussed. Subthreshold
di-electron production in Dp collisions at low spectator momenta is
investigated as well. Calculations have been performed for kinematical
conditions envisaged for forthcoming experiments at HADES.
The in-medium behavior of the nucleon spectral density including self-energies is revisited within the framework of QCD sum rules. Special emphasis is given to the density dependence of four-quark ...condensates. A complete catalog of four-quark condensates is presented and relations among them are derived. Generic differences of such four-quark condensates occurring in QCD sum rules for light baryons and light vector mesons are discussed.
We present a family of equations of state within a quasiparticle model adjusted to lattice QCD and study the impact on azimuthal flow anisotropies and transverse momentum spectra within hydrodynamic ...simulations for heavy-ion collisions at energies relevant for LHC.
The production of pseudo scalar, Eeta, Eta-prime, and vector, Omega, Rho, Phi, mesons in NN collisions at threshold-near energies is analyzed within a covariant effective meson-nucleon theory. It is ...shown that a good description of cross sections and angular distributions, for vector meson production, can be accomplished by considering meson and nucleon currents only, while for pseudo scalar production an inclusion of nucleon resonances is needed. The di-electron production from subsequent Dalitz decay of the produced mesons, \(\eta'\to \gamma \gamma^* \to\gamma e^+e^-\) and \(\omega\to \pi\gamma^*\to \pi e^+e^-\) is also considered and numerical results are presented for intermediate energies and kinematics of possible experiments with HADES, CLAS and KEK-PS. We argue that the transition form factor \(\omega\to \gamma^*\pi\) as well as \(\eta'\to \gamma^*\gamma\) can be defined in a fairly model independent way and the feasibility of an experimental access to transition form factors is discussed.
Our quasi-particle model is compared with recent lattice QCD data at finite temperature and baryon number density with emphasis on the coefficients in the Taylor series expansion of thermodynamic ...observables. The inclusion of static critical end point effects into the equation of state is discussed.
Eur.Phys.J.A23:291-304,2005 Vector meson ($V = \omega, \phi$) production in near-threshold elementary
nucleon-nucleon collisions $pp\to ppV$, $pn\to pnV$ and $pn\to dV$ is studied
within an effective ...meson-nucleon theory. It is shown that a set of effective
parameters can be established to describe fairly well the available
experimental data of angular distributions and the energy dependence of the
total cross sections without explicit implementation of the Okubo-Zweig-Iisuka
rule violation. Isospin effects are considered in detail and compared with
experimental data whenever available.
We analyze two types of spin observables in the reaction \(\pi \vec D\to\vec\Sigma\Theta^+\) near the threshold. One concerns the spin-transfer coefficients \(K_x^x\) and \(K_z^z\). The second one is ...the deuteron spin anisotropy. These observables are sensitive to the \(\Theta^+\) parity and can be used as a tool for the \(\Theta^+\) parity determination.
The contribution of the low-lying nucleon resonances \(P_{33}(1232)\), \(P_{11}(1440)\) \(D_{13}(1520)\) and \(S_{11}(1535)\) to the invariant mass spectra of di-electrons stemming from the exclusive ...processes \(pp\to pp e^+e^-\) and \(pn\to pn e^+e^-\) is investigated within a fully covariant and gauge invariant diagrammatical approach. We employ, within the one-boson exchange approximation, effective nucleon-meson interactions including the exchange mesons \(\pi\), \(\eta\), \(\sigma\), \(\omega\) and \(\rho\) as well as excitations and radiative decays of the above low-lying nucleon resonances. The total contribution of these resonances is dominant, however, bremsstrahlung processes in \(pp\) and, in particular, \(pn\) collisions at beam energies of 1 - 2 GeV are still significant in certain phase space regions.
Within a phenomenological quasiparticle model, the quark mass and temperature dependence of the QCD equation of state is discussed and compared with lattice QCD results. Different approximations for ...the quasiparticle dispersion relations are employed, scaling properties of the equation of state with quark mass and deconfinement temperature are investigated and a continuation to asymptotically large temperatures is presented.
The ground-based microwave radiometer MIAWARA-C recorded the upper stratospheric and lower mesospheric water vapour distribution continuously from June 2011 to March 2013 above the Arctic station of ...Sodankylae, Finland (67.4 degree N, 26.6 degree E) without major interruptions and offers water vapour profiles with temporal resolution of 1 h for average conditions. The water vapour time series of MIAWARA-C shows strong periodic variations in both summer and winter related to the quasi-2-day wave. Above 0.1 hPa the amplitudes are strongest in summer. The stratospheric wintertime 2-day wave is pronounced for both winters on altitudes below 0.1 hPa and reaches a maximum amplitude of 0.8 ppmv in November 2011. Over the measurement period, the instrument monitored the changes in water vapour linked to two sudden stratospheric warmings in early 2012 and 2013. Based on the water vapour measurements, the descent rate in the vortex after the warmings is 364 m d-1 for 2012 and 315 m d-1 for 2013.
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