120766753
Stability of the electron in the SU(5) and GWS models
Within the framework of the SU(5) model and by using non-zero vacuum expectation values for both charged and neutral Higgs fields, the lifetime of the electron ( tau e) can be expressed in terms of the photon mass (mgamma ). Using the upper limit of 10-24 GeV for mgamma given by studies of Jupiter's magnetic field, a lower limit of 1027 years is obtained for tau e, while the upper limit of 10-36 GeV for mgamma given by studies of galactic magnetic fields yielded a lower limit of 1051 years for tau e. The values for tau e can be obtained without giving rise to light Higgs particles. In contrast, the standard GWS model with two Higgs doublets gave rise to comparable values for tau e, but yielded a light Higgs particle with masses similar to mgamma .
122132298
On the Green's Functions for the Bethe‐Salpeter Equation
Considering the Bethe‐Salpeter equation as a relativistic equation, we have studied the free particle Green's functions for unequal mass scalar bosons, interacting via a translationally invariant potential. The scattering Green's function found by Huang and DeFacio (HD) is presented for all possible Ω‐plane contours for the unequal masses case. Only two k‐plane contours are found to be physically interesting. The causal, advanced, and retarded Green's functions are listed in an appendix for unequal masses for the physical contour. The timelike Green's functions again require severe restrictions on the interaction potential as found by HD, and possible Bethe‐Salpeter bound states are briefly discussed.
121477317
Neutrinos in a Robertson-Walker universe
A solution to the Einstein-Dirac system of equations in a Robertson-Walker spacetime is presented using the separation of variables method. With an axially symmetric and a non-axially symmetric boundary conditions, we find that there are no solutions for the massless fermions and only null or `ghost' solutions for the massive fermions. The `ghost' solutions carry a current but have a vanishing energy-momentum tensor and correspond to the special case when the Robertson-Walker spacetime reduces to flat spacetime.
122431079
Massive photons in General Relativity
In order to avoid a speed-of-light catastrophe in General Relativity with an electromagnetic source, gauge invariance with respect to the electric charge is broken with the photon acquiring mass. The general equations for the Einstein-Maxwell system are derived for the case with massive photons. Nonminimal couplings which might compete with the small minimal photon mass term are included.
120865732
Spontaneous Broken Symmetries, Loop Expansions and Magnon Fields
119923517
Effective f-g gravity theory and the cosmological constant
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,
118612347
Collisions of Jets of Particles from Active Galactic Nuclei with Neutralino Dark Matter
We examine the possibility that energetic Standard Model particles contained in the jets produced by active galactic nuclei (AGN) may scatter off of the dark matter halo which is expected to surround the AGN. In particular, if there are nearby states in the dark sector which can appear resonantly in the scattering, the cross section can be enhanced and a distinctive edge feature in the energy spectrum may appear. We examine bounds on supersymmetric models which may be obtained from the Fermi Gamma-ray Space Telescope observation of the nearby AGN Centaurus A.
119301023
Lifting slepton masses with a non-universal, non-anomalous U(1)NAF′ in Anomaly Mediated SUSY Breaking
Abstract We extend the Minimum Supersymmetry Standard Model by a non-anomalous family (NAF) U ( 1 ) NAF ′ gauge symmetry. All gauge anomalies are cancelled with no additional exotics other than the three right-handed neutrinos. The FI D-terms associated with the U ( 1 ) NAF ′ symmetry lead to additional positive contributions to slepton squared masses. In a RG invariant way, this thus solves the tachyonic slepton mass problem in Anomaly Mediated Supersymmetry Breaking. In addition, the U ( 1 ) NAF ′ symmetry naturally gives rise to the fermion mass hierarchy and mixing angles, and determines the mass spectrum of the sparticles.
1384985
HerMES: SPECTRAL ENERGY DISTRIBUTIONS OF SUBMILLIMETER GALAXIES AT z > 4*
We present a study of the infrared properties for a sample of seven spectroscopically confirmed submillimeter galaxies (SMGs) at z > 4.0. By combining ground-based near-infrared, Spitzer IRAC and MIPS, Herschel SPIRE, and ground-based submillimeter/millimeter photometry, we construct their spectral energy distributions (SEDs) and a composite model to fit the SEDs. The model includes a stellar emission component at λ_(rest) 50 μm. Six objects in the sample are detected at 250 and 350 μm. The dust temperatures for the sources in this sample are in the range of 40-80 K, and their L_(FIR) ~ 10^(13) L_☉ qualifies them as hyper-luminous infrared galaxies. The mean FIR-radio index for this sample is around 〈q〉 = 2.2 indicating no radio excess in their radio emission. Most sources in the sample have 24 μm detections corresponding to a rest-frame 4.5 μm luminosity of Log_(10)(L_(4.5)/L_☉) = 11 ~ 11.5. Their L_(4.5)/L_(FIR) ratios are very similar to those of starburst-dominated SMGs at z ~ 2. The L_(CO) – L_(FIR) relation for this sample is consistent with that determined for local ULIRGs and SMGs at z ~ 2. We conclude that SMGs at z > 4 are hotter and more luminous in the FIR but otherwise very similar to those at z ~ 2. None of these sources show any sign of the strong QSO phase being triggered.
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.