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Register a new userThe emergent black ring: a note on increasing ratio $sigma_{el}(s)/sigma_{tot}(s)$ at the LHC
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We discuss thw relations between the elastic and inelastic cross-sections valid for the shadow and reflective modes of the elastic scattering. Considerations are based on the unitarity arguments. It is shown that the redistribution of the total interaction probability between the elastic and inelastic interactions can lead to increasing ratio of $sigma_{el}(s)/sigma_{tot}(s)$ at the LHC energies in presence of the reflective scattering mode. The form of the inelastic overlap function becomes peripheral due to the negative feedback. In the absorptive scattering mode, the mechanism of this increase is a different one since the impact parameter dependence of the inelastic interactions probability is central in this case. A short notice is also given on the slope parameter and the leading contributions to its energy dependence in the both modes.
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Though the neutron mass is larger than the proton mass and obviously one expects in $e^+e^-$ annihilation a creation of more $p bar p$ pairs in comparison with $n bar n$ at the same energy, just the opposite inequality for the corresponding total cross sections $sigma_{tot}(e^+e^- to n bar n) > sigma_{tot}(e^+e^- to p bar p)$ has been revealed in the analysis of only the present time existing proton electromagnetic form factors data by the unitary and analytic approach.
We study the transport properties of strongly interacting matter in the context of ultrarelativistic heavy ion collision experiments. We calculate the transport coefficients viz. shear viscosity ($eta$) and electrical conductivity ($sigma_{rm{el}}$) of the quark-gluon plasma phase in the presence of momentum anisotropy arising from different expansion rates of the medium in longitudinal and transverse direction. We solve the relativistic Boltzmann kinetic equation in relaxation time approximation to calculate the shear viscosity and electrical conductivity. The calculations are performed within the quasiparticle model to estimate these transport coefficients and discuss the connection between them. We also compare the electrical conductivity results calculated from the quasiparticle model with the ideal case. We compare our results with the corresponding results obtained in the different lattice as well as model calculations.
he excess of data on the total cross section of $bar{b}b$ production in $gammagamma$ collisions over QCD predictions, observed by L3, OPAL and DELPHI Collaborations at LEP2, has so far defied explanation. The recent final analysis of L3 data has brought important new information concerning the dependence of the observed excess on the $gammagamma$ collisions energy $W_{gammagamma}$. The implications of this dependence are discussed.
We propose a new method of the determination of $R^{D}=sigma_{L}^{D}/sigma_{T}^{D}$ from the dependence of the diffractive cross section on the azimuthal angle between the electron scattering and proton scattering planes. The method is based on our finding of the model independence of the ratio of the $LT$ interference and transverse diffractive structure functions. The predicted azimuthal asymmetry is substantial and can be measured at HERA. We show that the accuracy of our reconstruction of $R^{D}$ is adequate for a reliable test of an important pQCD prediction of $R^{D}gsim 1$ for large $beta$.
The exclusive deep inelastic electroproduction of $psi(2S)$ and $J/psi(1S)$ at an $ep$ centre-of-mass energy of 317 GeV has been studied with the ZEUS detector at HERA in the kinematic range $2 < Q^2 < 80$ GeV$^2$, $30 < W < 210$ GeV and $|t| < 1$ GeV$^2$, where $Q^2$ is the photon virtuality, $W$ is the photon-proton centre-of-mass energy and $t$ is the squared four-momentum transfer at the proton vertex. The data for $2 < Q^2 < 5$ GeV$^2$ were taken in the HERA I running period and correspond to an integrated luminosity of 114 pb$^{-1}$. The data for $5 < Q^2 < 80$ GeV$^2$ are from both HERA I and HERA II periods and correspond to an integrated luminosity of 468 pb$^{-1}$. The decay modes analysed were $mu^+mu^-$ and $J/psi(1S) ,pi^+pi^-$ for the $psi(2S)$ and $mu^+mu^-$ for the $J/psi(1S)$. The cross-section ratio $sigma_{psi(2S)}/sigma_{J/psi(1S)}$ has been measured as a function of $Q^2, W$ and $t$. The results are compared to predictions of QCD-inspired models of exclusive vector-meson production.
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