124505729
NLO merging in $t\bar{t}$+jets
53540874
Dark matter induced nucleon decay: model and signatures
A bstractIf dark matter (DM) carries anti-baryon number, a DM particle may annihilate with a nucleon by flipping to anti-DM. Inspired by Hylogenesis models, we introduce a single component DM model where DM is asymmetric and carries B and L as -1/2. It can annihilate with a nucleon to an anti-lepton and an anti-DM at leading order or with an additional meson at sub-leading order. Such signals may be observed in proton decay experiments. If DM is captured in the Sun, the DM induced nucleon decay can generate a large flux of anti-neutrinos, which could be observed in neutrino experiments. Furthermore, the anti-DM particle in the final state obtains a relatively large momentum (few hundred MeV), and escapes the Sun. These fast-moving anti-DM particles could also induce interesting signals in various underground experiments.
117991499
Zero and one jet combined next-to-leading order analysis of the top quark forward-backward asymmetry
We present an analysis of the forward{backward asymmetry in the production of top quark pairs at the Tevatron collider. We use novel Monte Carlo methods for merging matrix elements and parton showers to combine NLO QCD predictions fort t andt t+jet production. Theoretical uncertainties are quantied in detail. We nd agreement with experimental data on the transverse momentum dependence of the asymmetry. t t events with large invariant mass, mt t 450 GeV. The inclusive parton-level asymmetry was measured as 0:164 0:047 considering all pair masses, and 0:295 0:067 for mt t 450 GeV. This needs to be compared to theoretical predictions from various event generators in the unrestricted and high t t mass region: 0:067 0:020 and 0:089 0:027 from MC@NLO (6, 7), 0:066 0:020 and 0:100 0:030 from POWHEG (8, 9), and 0:073 0:022 and 0:110 0:033 from MCFM (4, 10). In all cases, electroweak corrections had been applied. The linear behavior of AFB with increasing y and mt t persists,
119211995
A Monte Carlo study to check the hadronic interaction models by a new EAS hybrid experiment in Tibet
A new EAS hybrid experiment has been designed by constructing a YAC (Yangbajing Air shower Core) detector array inside the existing Tibet- III air shower array. The first step of YAC, called "YAC-I", consists of 16 plastic scintillator units (4 rows times 4 columns) each with an area of 40 cm◊50 cm which is used to check hadronic interaction models used in AS simulations. A Monte Carlo study shows that YAC-I can record high energy electromagnetic component in the core region of air showers induced by primary particles of several tens TeV energies where the primary composition is directly measured by space experiments. It may provide a direct check of the hadronic interaction models currently used in the air shower simulations in the corresponding energy region. In present paper, the method of the observation and the sensitivity of the characteristics of the observed events to the different interaction models are discussed.
121902881
Unified SL(8,C) model of spin-2 gluons and gravitons
A unified version of $f\ensuremath{-}g$ gravity models with Higgs field has been constructed using the SL(8, $C$) group. Leptons and quarks are represented in a four-color scheme using the SU(4) group. When the Higgs fields exhibit a spontaneous breakdown of symmetry in the tree approximation, the spin-2 gluons ($f$) and fermions acquire mass while the graviton ($g$) remains massless. The Higgs-fermion interaction is renormalizable in contrast to the $\mathrm{SL}(2,C)\ensuremath{\bigotimes}\mathrm{SL}(6,C)$ gravity models. The spin-2 gluons include the three-color gluon, an exotic gluon which mixes leptons with hadrons, and a weak gluon which mediates only between leptons.
118161983
GL(20,C) MODEL FOR SPIN-1 AND SPIN-2 FIELDS
An effective model for spin-1 and spin-2 fields with internal symmetries is constructed by folding in the SL(2,C) space-time invariance group with the SO(10) internal symmetry groups to form a GL(20,C) unifying gauge group. The symmetry is spontaneously broken via the introduction of Higgs fields with nonvanishing vacuum expectation values. This is performed in such a way that the SL(2,C) subgroup remains invariant to manifest a Lorentz-invariant vacuum. The Lagrangian density consist of the lowest-order Einstein-like term and a higher order R/sup 2/-like term. If the higher-order term is omitted, the theory can serve as a phenomenological model for f-g gravity and includes massless and massive spin-2 fields and massive spin-1 fields. Including the R/sup 2/-like term, we have, at energies much below the Planck mass, a possible phenomenological model containing massless and massive spin-2 fields and massless and massive spin-1 fields. However, at higher energies, ghost states arising from the R/sup 2/-like term will appear.
16490365
Effects of dark-matter density profiles on bulge formation in very late-type galaxies
The dynamical evolution of super star clusters has been investigated in dark matter halos depicted with a cuspy- or soft-core density profile. The simulations show that (1) exponential bulges with central cusps form in both cases;(2) distinctive bulge formation rates are derived for cuspy- and soft-core profile; (3) masses of bulges and nuclear clusters are more heavier in case of cuspy-core profile; (4) massive, nuclear star clusters possibly form with no discernible bulges at different ages in cuspy- or soft-core cases.
122140676
SPIN-1 AND SPIN-2 GAUGE FIELDS IN UNIFIED SL(2N,C) MODELS