Generalized Density Matrix Revisited: Microscopic Approach to Collective Dynamics in Soft Spherical Nuclei

The generalized density matrix (GDM) method is used to calculate microscopically the parameters of the collective Hamiltonian. Higher order anharmonicities are obtained consistently with the lowest order results, the mean field [Hartree-Fock-Bogoliubov (HFB) equation] and the harmonic potential [quasiparticle random phase approximation (QRPA)]. The method is applied to soft spherical nuclei, where the anharmonicities are essential for restoring the stability of the system, as the harmonic potential becomes small or negative. The approach is tested in three models of increasing complexity: the Lipkin model, model with factorizable forces, and the quadrupole plus pairing model.Comment: submitted to Physical Review C on 08 May, 201

Rigid supersymmetry with boundaries

We construct rigidly supersymmetric bulk-plus-boundary actions, both in $x$-space and in superspace. For each standard supersymmetric bulk action a minimal supersymmetric bulk-plus-boundary action follows from an extended $F$- or $D$-term formula. Additional separately supersymmetric boundary actions can be systematically constructed using co-dimension one multiplets (boundary superfields). We also discuss the orbit of boundary conditions which follow from the Euler-Lagrange variational principle.Comment: 28 pages, JHEP clas

Hexadecapole Interaction and the Delta I=4 Staggering Effect in Rotational Bands

A role of the multipole interaction in the description of the $\triangle I$=4 staggering phenomenon is investigated in a model consisting of a single-$j$ shell filled by identical nucleons. Exact diagonalization of the quadrupole-plus-hexadecapole Hamiltonian shows that the hexadecapole-hexadecapole interaction can produce a $\triangle I$=4 periodicity in the yrast sequence.Comment: revised version with technical changes only, to be published in Physica Scripta, latex, 4 pages, 3 PostScript figures available on request from [email protected], preprint No. IFT/18/9

Magnetic Moments of Heavy ΞQ\Xi_{Q} Baryons in Light Cone QCD Sum Rules

The magnetic moments of heavy $\Xi_{Q}$ baryons containing a single charm or bottom quark are calculated in the framework of light cone QCD sum rules method. A comparison of our results with the predictions of the quark models is presented.Comment: 26 Pages, 8 Figures and 1 Tabl

WHW_H-pair Production in the Littlest Higgs Model with T parity in next-to-leading order QCD at LHC

In the framework of the littlest Higgs model with $T$ parity, we study the $W_H$-pair production at the CERN Large Hadron Collider up to the QCD next-to-leading order (NLO). The kinematic distributions of final decay products and the theoretical dependence of the cross section on the factorization/renormalization scale are analyzed. We adopt the PROSPINO scheme in the QCD NLO calculations to avoid double counting and keep the convergence of the perturbative QCD description. Our numerical results show that the QCD NLO corrections significantly reduce the scale uncertainty, and enhance the leading order integrated cross section with a $K$-factor in the range of $1.10-1.22$ ($1.09-1.17$) with the symmetry breaking scale $f$ varying from $400 GeV$ ($400 GeV$) to $1.5 TeV$ ($1.0 TeV$) at the $14 TeV$ $(8 TeV)$ LHC. We find that it is possible to select the signal events of the $W_H$-pair production from the $pp\to W^+ W^- \to e^+ \mu^-\nu_{e}\bar{\nu}_{\mu}+X$ background with high ratio of signature over background by taking proper lower limits on transverse momenta, invariant mass of the final charged leptons and the missing transverse momentum.Comment: 34 pages, 14 figures, 4 table

Single top quarks at the Fermilab Tevatron

We present a calculation of the single top quark cross section for proton-antiproton interactions with sqrt(s) = 1.8 TeV at the Fermilab Tevatron collider. We examine the effects of top mass, parton distribution functions, QCD scale, and collision energy, on each of the component production mechanisms, and study the kinematic distributions for standard model electroweak production. At the upgraded Tevatron with sqrt(s) = 2.0 TeV and high luminosity, it will be possible to test the nature of the Wtb coupling using single top production. We estimate the sensitivity to measure the single top cross section, and thus to directly measure V_tb and the top quark partial width. We show what happens to the V_tb measurement when an anomalous (V+A) component is added to the Wtb coupling, and how the top quark polarization affects the kinematic distributions.Comment: 31 pages including 11 figure

E6SSM vs MSSM gluino phenomenology

The E6SSM is a promising model based on the group E6, assumed to be broken at the GUT scale, leading to the group SU(3)\times SU(2)\times U(1)\times U(1)' at the TeV scale. It gives a solution to the MSSM {\mu}-problem without introducing massless axions, gauge anomalies or cosmological domain walls. The model contains three families of complete 27s of E6, giving a richer phenomenology than the MSSM. The E6SSM generically predicts gluino cascade decay chains which are about 2 steps longer than the MSSM's due to the presence of several light neutralino states. This implies less missing (and more visible) transverse momentum in collider experiments and kinematical distributions such as M_eff are different. Scans of parameter space and MC analysis suggest that current SUSY search strategies and exclusion limits have to be reconsidered.Comment: Presented at the 2011 Hadron Collider Physics symposium (HCP-2011), Paris, France, November 14-18 2011, 3 pages, 7 figure