118615935
Supersymmetric dark matter sectors
We investigate the properties of a dark matter sector where supersymmetry is a good symmetry. In this context we find that the stability of the dark matter candidate is possible even when R-parity is broken in the visible sector. In order to illustrate the idea we investigate a simple scenario where the dark matter candidate is the lightest scalar field in the dark sector which annihilates mainly into two sfermions when these channels are available. We study the relic density constraints and the predictions for the dark matter detection experiments.
119194544
Prospects and constraints for vector-like MFV matter at LHC
We examine the prospects for LHC discovery of SU(2)L singlet vector-like quarks that obey Minimal Flavour Violation (MFV) and are consistent with lower energy phenomenology. We study models where the vector-like quarks have the same quantum numbers as uR or dR, allowing mixing, which generally leads to significant low energy constraints. We find that at leading order in the MFV expansion there are two naturally phenomenologically viable MFV models of this type when the Weyl spinor components of the vector-like quarks are flavour triplets. We examine direct production bounds, flavour and electroweak precision data constraints for these models and determine the cross section for allowed values of the model parameters at LHC. For the models we identify as naturally phenomenologically viable, large amounts of parameter space afford a significant early discovery reach at LHC while being consistent with lower energy phenomenology.
1772638
Color octet scalars and high p_T four-jet events at the LHC
We study the effect of color octet scalars on the high transverse momenta four-jet cross section at the LHC. We consider both weak singlet and doublet scalars, concentrating on the case of small couplings to quarks. We find that a relatively early discovery at the LHC is possible for a range of scalar masses.
13056052
Particle creation in a toroidal universe
We calculate the particle production rate in an expanding universe with a three-torus topology. We discuss also the complete evolution of the size of such a universe. The energy density of particles created through the nonzero modes is computed for selected masses. The unique contribution of the zero mode and its properties are also analyzed.
34406165
Standard model with compactified spatial dimensions
We analyze the structure of the standard model coupled to gravity with spatial dimensions compactified on a three-torus. We find that there are no stable one-dimensional vacua at zero temperature, although there does exist an unstable vacuum for a particular set of Dirac neutrino masses.
96468936
Collective oblate bands in Pb196
Evidence for collective oblate behavior in [sup 196]Pb is presented. One irregular and two regular bands of [ital M]1 transitions have been observed following the [sup 170]Er([sup 30]Si,4[ital n]) and [sup 176]Yb([sup 26]Mg,6[ital n]) reactions. Transitions linking the most intense regular band to the low-lying negative-parity yrast levels are observed, establishing excitation energies, spins, and probable parities of the band members. In contrast, no such transitions have been found for the irregular band and the weaker regular band. The bands are interpreted as corresponding to collective oblate rotation, arising mainly from deformation-aligned high-[ital j], shape-driving quasiproton excitations across the [ital Z]=82 shell gap, coupled to rotation-aligned quasineutrons.
38074697
Lowest excitations in 56Ti and the predicted N=34 shell closure.
Recent experimental characterization of the subshell closure at N=32 in the Ca, Ti, and Cr isotones has stimulated shell-model calculations that indicated the possibility that the N=34 isotones of these same elements could exhibit characteristics of a shell closure, namely, a high energy for the first excited 2(+) level. To that end, we have studied the decay of 56Sc produced in fragmentation reactions and identified new gamma rays in the daughter N=34 isotone 56Ti. The first 2(+) level is found at an energy of 1127 keV, well below the expected position that would indicate the presence of an N=34 shell closure in 56Ti.
121561220
Proton-hole states in the N=30 neutron-rich isotope K-49
Excited states in the N=30 neutron-rich isotope {sup 49}K have been studied using multinucleon transfer reactions with thin targets and the PRISMA-CLARA spectrometer combined with thick-target {gamma}-coincidence data from Gammasphere. The d{sub 3/2} proton-hole state is located 92 keV above the s{sub 1/2} ground state, and the proton-particle f{sub 7/2} state is suggested at 2104 keV. Three other levels are established as involving the coupling to 2{sup +} of two neutrons above the N=28 shell. The measured or estimated lifetimes served to reinforce the interpretation of the observed level structure, which is found to be in satisfactory agreement with shell-model calculations.
122764276
Excitations of two and three valence proton nuclei Te-134 and I-135
45984662
Reduced transition probabilities to the first 2 + state in 52,54,56Ti and development of shell closures at N = 32, 34
The even {sup 52-56}Ti isotopes have been studied with intermediate-energy Coulomb excitation and absolute B(E2;0{sup +}{yields}2{sub 1}{sup +}) transition rates have been obtained. These data confirm the presence of a subshell closure at neutron number N=32 in neutron-rich nuclei above the doubly magic nucleus {sup 48}Ca and provide no direct evidence for the predicted N=34 closure. Large-scale shell model calculations with the most recent effective interactions are unable to reproduce the magnitude of the measured strengths in the semimagic Ti nuclei and their strong variation with neutron number.