Next-to-leading order QCD predictions for associated production of top squarks and charginos at the CERN LHC

We present the calculations of the complete next-to-leading order (NLO) inclusive total cross sections for the associated production processes $pp\to \tilde{t}_i\tilde{\chi}_k^-+X$ in the Minimal Supersymmetric Standard Model at the CERN Large Hadron Collider. Our calculations show that the total cross sections for the $\tilde{t}_1\tilde{\chi}_1^-$ production for the lighter top squark masses in the region 100 GeV $< m_{\tilde{t}_1}<$ 160 GeV can reach 1 pb in the favorable parameter space allowed by the current precise experiments, and in other cases the total cross sections generally vary from 10 fb to several hundred fb except both $m_{\tilde{t}_1}>$ 500 GeV and the $\tilde{t}_2\tilde{\chi}_2^-$ production channel. Moreover, we find that the NLO QCD corrections in general enhance the leading order total cross sections significantly, and vastly reduce the dependence of the total cross sections on the renormalization/factorization scale, which leads to increased confidence in predictions based on these results.Comment: 42 pages, 13 figures, RevTex4. Journal-ref adde

Covariant Hamiltonian boundary term: Reference and quasi-local quantities

The Hamiltonian for dynamic geometry generates the evolution of a spatial region along a vector field. It includes a boundary term which determines both the value of the Hamiltonian and the boundary conditions. The value gives the quasi-local quantities: energy-momentum, angular-momentum and center-of-mass. The boundary term depends not only on the dynamical variables but also on their reference values; the latter determine the ground state (having vanishing quasi-local quantities). For our preferred boundary term for Einstein's GR we propose 4D isometric matching and extremizing the energy to determine the reference metric and connection values.Comment: 6 pages, contribution to the Proceedings of the Second LeCosPA Symposium "Everything about Gravity", Taipei, 14-18 Dec., 201

Spin Correlations in top quark pair production near threshold at the e−e+ e^- e^+ Linear Collider

We investigate the spin correlations in top quark pair production near threshold at the $e^- e^+$ linear collider. Comparing with the results above the threshold region, we find that near the threshold region the off-diagonal basis, the optimized decomposition of the top quark spins above the threshold region, does not exist, and the beamline basis is the optimal basis, in which there are the dominant spin components: the up-down (UD) component for $e_L^- e^+$ scattering and the down-up (DU) component for $e_R^- e^+$ scattering can make up more than 50% of the total cross section, respectively.Comment: 12 pages, 3 figures, minor modification

t→cVt\to cV via SUSY FCNC couplings in the unconstrained MSSM

We recalculate the branching ratios for $t\to cV$ ($V=g,\gamma,Z$) induced by SUSY FCNC couplings within the general unconstrained MSSM framework using mass eigenstate approach. Our results show that the branching ratios for these decays are larger than ones reported in previous literatures in the MSSM with R-parity conservation, and they can reach $\sim 10^{-4}$, $\sim 10^{-6}$, and $\sim 10^{-6}$, respectively, for favorable parameter values allowed by current precise experiments. Thus, the branching ratios for $t\to cg$ and $t\to c\gamma$ may be measurable at the LHC.Comment: 15 pages, 3 figures, minor changs in the Table