1,473 research outputs found

    Forward antiproton-deuteron elastic scattering and total spin-dependent antiproton-deuteron cross sections at intermediate energies

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    Spin-dependent total pbar-d cross sections are considered using the optical theorem. For this aim the full spin dependence of the forward pbar-d elastic scattering amplitude is considered in a model independent way. The single-scattering approximation is used to relate this amplitude to the elementary amplitudes of pbar-p and pbar-n scattering and the deuteron form factor. A formalism allowing to take into account Coulomb-nuclear interference effects in polarized pbar-d cross sections is developed. Numerical calculations for the polarized total pbar-d cross sections are performed at beam energies 20-300 MeV using the Nbar-N interaction models developed by the Julich group. Double-scattering effects are estimated within the Glauber approach and found to be in the order of 10-20%. Existing experimental data on differential pbar-d cross sections are in good agreement with the performed Glauber calculations. It is found that for the used Nbar-N models the total longitudinal and transversal pbar-d cross sections are comparable in absolute value to those for pbar-p scattering.Comment: 19 pages, 8 figures; typos in appendix removed, Section about Coulomb-nuclear interference re-structured, figures improved; accepted for publication in Phys. Rev.

    Antiproton scattering off 3He^3 He and 4He^4 He nuclei at low and intermediate energies

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    Antiproton scattering off ^3\He and ^4\He targets is considered at beam energies below 300 MeV within the Glauber-Sitenko approach, utilizing the NˉN\bar N N amplitudes of the J\"ulich model as input. A good agreement with available data on differential \bar p ^4\He cross sections and on \bar p ^3\He and \pbar ^4\He reaction cross sections is obtained. Predictions for polarized total pˉ3\bar p ^3He cross sections are presented, calculated within the single-scattering approximation and including Coulomb-nuclear interference effects. The kinetics of the polarization buildup is discussed.Comment: 11 pages, 6 figure

    Density resummation of perturbation series in a pion gas to leading order in chiral perturbation theory

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    The mean field (MF) approximation for the pion matter, being equivalent to the leading ChPT order, involves no dynamical loops and, if self-consistent, produces finite renormalizations only. The weight factor of the Haar measure of the pion fields, entering the path integral, generates an effective Lagrangian δLH\delta \mathcal{L}_{H} which is generally singular in the continuum limit. There exists one parameterization of the pion fields only, for which the weight factor is equal to unity and δLH=0\delta \mathcal{L}_{H}=0, respectively. This unique parameterization ensures selfconsistency of the MF approximation. We use it to calculate thermal Green functions of the pion gas in the MF approximation as a power series over the temperature. The Borel transforms of thermal averages of a function J(χαχα)\mathcal{J}(\chi ^{\alpha}\chi ^{\alpha}) of the pion fields χα\chi ^{\alpha} with respect to the scalar pion density are found to be 2πJ(4t)\frac{2}{\sqrt{\pi}}\mathcal{J}(4t). The perturbation series over the scalar pion density for basic characteristics of the pion matter such as the pion propagator, the pion optical potential, the scalar quark condensate , the in-medium pion decay constant F~{\tilde{F}}, and the equation of state of pion matter appear to be asymptotic ones. These series are summed up using the contour-improved Borel resummation method. The quark scalar condensate decreases smoothly until Tmax310T_{max}\simeq 310 MeV. The temperature TmaxT_{max} is the maximum temperature admissible for thermalized non-linear sigma model at zero pion chemical potentials. The estimate of TmaxT_{max} is above the chemical freeze-out temperature T170T\simeq 170 MeV at RHIC and above the phase transition to two-flavor quark matter Tc175T_{c} \simeq 175 MeV, predicted by lattice gauge theories.Comment: Replaced with revised and extended version. Results are compared to lattice gauge theories. 16 pages REVTeX, 13 eps figure

    On the possibility of f0f_0 observation in low energy pppp collisions

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    Within the meson-exchange model we calculate f0f_0-meson production cross section in \piN and NNNN reactions and investigate the possibility for f0f_0 observation via the KKˉK\bar{K} decay mode in pppp collisions. Our studies indicate that an extraction of the f0f_0 signal is unlikely due to the large background from other reaction channels.Comment: 6 pages, LaTeX, including 10 postscript figures, to appear in Eur. Phys. J.

    Probing the interactions of charmed mesons with nuclei in pˉ\bar p induced reactions

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    We study the perspectives of resonant and nonresonant charmed meson production in pˉ+A\bar{p} + A reactions within the Multiple Scattering Monte Carlo (MSMC) approach. We calculate the production of the resonances Ψ(3770),Ψ(4040)\Psi(3770), \Psi(4040) and Ψ(4160)\Psi(4160) on various nuclei, their propagation and decay to D,Dˉ,D,Dˉ,Ds,DˉsD, \bar{D}, D^*, \bar{D}^*, D_s, \bar{D}_s in the medium and vacuum, respectively. The modifications of the open charm vector mesons in the nuclear medium are found to be rather moderate or even small such that dilepton spectroscopy will require an invariant mass resolution of a few MeV. Furthermore, the elastic and inelastic interactions of the open charm mesons in the medium are taken into account, which can be related to (u,d)(u,d)-, ss- or cc-quark exchange with nucleons. It is found that by studying the D/DˉD/\bar{D} ratio for low momenta in the laboratory (22.2\leq 2-2.2 GeV/c) as a function of target mass AA stringent constraints on the cc-quark exchange cross section can be obtained. On the other hand, the ratios Ds/Ds+D^-_s/D^+_s as well as D/DsD/D^-_s and D/Ds+D/D^+_s at low momenta as a function of AA will permit to fix independently the strength of the ss-quark exchange reaction in DsND^-_s N scattering.Comment: 9 pages, LaTeX, including 9 postscript figures, submitted to Eur. Phys. J.

    Near-threshold production of a0(980) mesons in the reaction pp -> d K^+ \bar{K}^0

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    Using an effective Lagrangian approach as well as the Quark-Gluon Strings Model we analyze near-threshold production of a0(980)-mesons in the reaction NN -> d K \bar{K} as well as the background of non-resonant K\bar{K}-pair production. We argue that the reaction pp -> d K^+ \bar{K}^0 at an energy release Q<=100 MeV is dominated by the intermediate production of the a0(980)-resonance. At larger energies the non-resonant K^+\bar{K}^0-pair production - where the kaons are produced in a relative P-wave - becomes important. Then effects of final-state interactions are evaluated in a unitarized scattering-length approach and found to be in the order of a 20% suppression close to threshold. Thus in present experiments at the Cooler Synchrotron COSY-J\"ulich for Q<=107 MeV the a_0^+ signal can reliably be separated from the non-resonant K^+\bar{K^0} background.Comment: 14 pages, 12 figures, submitted to EPJ

    Tetramixing of vector and pseudoscalar mesons: A source of intrinsic quarks

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    The tetramixing of pseudoscalar mesons π\pi-η\eta-η\eta'-ηc\eta_c and vector mesons ω\omega-ρ\rho-ϕ\phi-J/ψJ/\psi are studied in the light-cone constituent quark model, and such mixing of four mesons provides a natural source for the intrinsic charm ccˉc\bar{c} components of light mesons. By mixing with the light mesons, the charmonium states J/ψJ/\psi and ηc\eta_c could decay into light mesons more naturally, without introducing gluons or a virtual photon as intermediate states. Thus, the introduction of light quark components into J/ψJ/\psi is helpful to reproduce the new experimental data of J/ψJ/\psi decays. The mixing matrices and the Q2Q^2 behaviors of the transition form factors are also calculated and compared with experimental data.Comment: 20 pages, 10 figures. Version for publication in PR
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