Near-threshold Z-pair production in the semi-phenomenological model of unstable particles

Near-threshold production of neutral boson pairs is considered within the framework of the model of unstable particles with smeared mass. The results of calculations are in good agreement with LEP II data and Monte-Carlo simulations.Comment: 7 pages, 2 figure

Nonperturbative and spin effects in the central exclusive production of tensor χc(2+)\chi_c(2^+) meson

We discuss central exclusive production (CEP) of the tensor $\chi_c(2^{+})$ meson in proton-(anti)proton collisions at Tevatron, RHIC and LHC energies. The amplitude for the process is derived within the $k_t$-factorisation approach. Differential and total cross sections are calculated for several unintegrated gluon distributions (UGDFs). We compare exclusive production of all charmonium states $\chi_c(0^+),\,\chi_c(1^+)$ and $\chi_c(2^+)$. Equally good description of the recent Tevatron data is achieved both with Martin-Ryskin phenomenological UGDF and UGDF based on unified BFKL-DGLAP approach. Unlike for Higgs production, the main contribution to the diffractive amplitude of heavy quarkonia comes from nonperturbative region of gluon transverse momenta Q_{\perp}<1\,\GeV. At $y \approx$ 0, depending on UGDF we predict the contribution of $\chi_c(1^+,2^+)$ to the $J/\Psi + \gamma$ channel to be comparable or larger than that of the $\chi_c(0^+)$ one. This is partially due to a significant contribution from lower polarization states $\lambda=0$ for $\chi_c(1^+)$ and $\lambda=0,\,\pm 1$ for $\chi_c(2^+)$ meson. Corresponding theoretical uncertainties are discussed.Comment: 18 pages, 12 figures, discrepancies with Durham group results clarified, numerics corrected, basic conclusions unchanged, acknowledgements adde

On Semidefinite Programming Relaxations of the Travelling Salesman Problem (Replaced by DP 2008-96)

AMS classification: 90C22, 20Cxx, 70-08traveling salesman problem;semidefinite programming;quadratic as- signment problem

Evidence of Odderon-exchange from scaling properties of elastic scattering at TeV energies

We study the scaling properties of the differential cross section of elastic proton-proton ($pp$) and proton-antiproton ($p\bar p$) collisions at high energies. We introduce a new scaling function, that scales -- within the experimental errors -- all the ISR data on elastic $pp$ scattering from $\sqrt{s} = 23.5$ to $62.5$ GeV to the same universal curve. We explore the scaling properties of the differential cross-sections of the elastic $pp$ and $p\bar p$ collisions in a limited TeV energy range. Rescaling the TOTEM $pp$ data from $\sqrt{s} = 7$ TeV to $2.76$ and $1.96$ TeV, and comparing it to D0 $p\bar p$ data at $1.96$ TeV, our results provide an evidence for a $t$-channel Odderon exchange at TeV energies, with a significance of at least 6.26$\sigma$. We complete this work with a model-dependent evaluation of the domain of validity of the new scaling and its violations. We find that the $H(x)$ scaling is valid, model dependently, within $200$ GeV $\leq \sqrt{s} \leq$ $8$ TeV, with a $-t$ range gradually narrowing with decreasing colliding energies.Comment: Accepted in EPJ C, with typos fixed, reorganized institutions updated, Appendix A, B, C, D, E added, 60 pages, 29 figures, 13 tables, Odderon significance: 6.26 sigma, conclusions unchange

On the Lovasz O-number of Almost Regular Graphs With Application to Erdos-Renyi Graphs

AMS classifications: 05C69; 90C35; 90C22;Erdos-Renyi graph;stability number;Lovasz O-number;Schrijver O-number;C*-algebra;semidefinite programming

Exploiting Group Symmetry in Truss Topology Optimization

AMS classification: 90C22, 20Cxx, 70-08truss topology optimization;semidefinite programming;group symmetry