122379517
Infrared Constraints On Ultraviolet Theories
118736479
Direct detection with dark mediators
We introduce dark mediator Dark matter (dmDM) where the dark and visible sectors are connected by at least one light mediator carrying the same dark charge that stabilizes DM. is coupled to the Standard Model via an operator qq =, and to dark matter via a Yukawa coupling y c . Direct detection is
55446956
Missing energy signatures of dark matter at the LHC
We use ATLAS and CMS searches in the mono-jet + missing energy and mono-photon + missing energy final state to set limits on the couplings of dark matter to quarks and gluons. Working in an effective field theory framework we compare several existing mono-jet analyses and find that searches with high p_T cuts are more sensitive to dark matter. We constrain the suppression scale of the effective dark matter-Standard Model interactions, and convert these limits into bounds on the cross sections relevant to direct and indirect detection. We find that, for certain types of operators, in particular spin-independent dark matter-gluon couplings and spin-dependent dark matter-quark couplings, LHC constraints from the mono-jet channel are competitive with, or superior to, limits from direct searches up to dark matter masses of order 1 TeV. Comparing to indirect searches, we exclude, at 90% C.L., dark matter annihilating to quarks with the annihilation cross section of a thermal relic for masses below ~ 15-70 GeV, depending on the Lorentz structure of the effective couplings. Mono-photon limits are somewhat weaker than mono-jet bounds, but still provide an important cross check in the case of a discovery in mono-jets. We also discuss the possibility that dark matter--Standard Model interactions at LHC energies cannot be described by effective operators, in which case we find that constraints can become either significantly stronger, or considerably weaker, depending on the mass and width of the intermediate particle. We also discuss the special case of dark matter coupling to the Higgs boson, and we show that searches for invisible Higgs decays would provide superior sensitivity, particularly for a light Higgs mass and light dark matter.
118502677
Spontaneous R-symmetry Breaking with Multiple Pseudomoduli
We examine generalized O’Raifeartaigh models that feature multiple tree-level flat directions and only contain fields with R-charges 0 or 2. We show that spontaneous R-breaking at up to one-loop order is impossible in such theories. Specifically, we prove that the R-symmetric origin of field space is always a local minimum of the one-loop Coleman-Weinberg potential, generalizing an earlier result for the case of a single flat direction. This result has consequences for phenomenology and helps elucidate the behavior of various models of dynamical SUSY breaking.
15753083
Singlet-Stabilized Minimal Gauge Mediation
We propose Singlet Stabilized Minimal Gauge Mediation as a simple ISS-based model of Direct Gauge Mediation which avoids both light gauginos and Landau poles. The hidden sector is a massive s-conning SQCD that is distinguished by a minimal SU(5) avor group. The uplifted vacuum is stabilized by coupling the meson to an additional singlet sector with its own U(1) gauge symmetry via non-renormalizable interactions suppressed by a higher scale UV in the electric theory. This generates a nonzero VEV for the singlet meson via the inverted hierarchy mechanism, but requires tuning to a precision ( = UV ) 2 , which is 10 4 . In the course of this analysis we also outline some simple model-building rules for stabilizing uplifted ISS models, which lead us to conclude that meson deformations are required (or at least heavily favored) to stabilize the adjoint component of the magnetic meson.
119194513
Neutralino Oscillations at the LHC
We study a supersymmetric phenomenon that can give spectacular signals at the LHC: oscillations of neutralinos. Such oscillations can be naturally realised in Rsymmetric models, where additional elds are introduced as Dirac mass partners of gauginos and Higgsinos. Majorana masses for gauginos, necessarily generated from anomaly mediation, can create tiny mass splittings between degenerate mass eigenstates, causing states produced at the LHC to oscillate between neutralinos and their Dirac partner elds. Scenarios where such states decay with displaced vertices can lead to striking signatures at the LHC, where the oscillation can be visible directly in the distribution of displaced vertex lengths. We elaborate on the theory and LHC phenomenology of this feature within a specic scenario of a Higgsino decaying with a displaced vertex into a gravitino and a Z boson.
122236287
High-Energy Electron-Electron Scattering
The radiative corrections to the electron-electron scattering of the order alpha /sup 3/ were calculated for the colliding beam experiment and the experiment in which the target electron is at rest initially. The contributions from high-energy real photons were included. The two-photon exchange diagrams were found to give only negligible contributions to the cross sections after infrared cancellation. The effect due to the possible breakdown of quantum electrodynamics is discussed. A preliminary study on the electron-positron colliding beam experiment involving various interactions was made. The vacuum polarizations involving heavier particles than an electron pair in the closed loop were investigated. (auth)
119232432
Sensitivities of the IceCube DeepCore detector to signatures of low-mass dark matter in the Galactic halo
We discuss the event rate in the DeepCore array due to neutrino flux produced by annihilations and decays of Galactic dark matter. This event rate is calculated with a 10 GeV threshold energy, which is smaller than the threshold energy taken in previous works. Taking into account the background event rate due to the atmospheric neutrino flux, we evaluate the sensitivity of the DeepCore array for probing the dark matter annihilation cross section and decay time. The sensitivity studies include the annihilation modes chi chi -> b (b) over bar, tau(+)tau(-), mu(+)mu(-), and nu(nu) over bar, and decay modes chi -> b (b) over bar, tau(+)tau(-), mu(+)mu(-), and nu(nu) over bar. We compare our results with corresponding constraints derived from observations of WMAP, ACT, and Fermi-LAT. DOI: 10.1103/PhysRevD.87.025003
12248039
An improved Weizsacker Williams method and photoproduction of lepton pairs
Abstract An improved Weizsacker Williams method which properly handles the atomic and nuclear form factors is given. The method is applied to calculate the energy-angle distributionsof photoproduced lepton pairs: 1) An electron pair from an atom with screening effects; 2) a muon pair from a nucleus with an elastic form factor. The numerical results are compared with the exact calculation using the Born approximation, and the agreements are found to be better than a few percents. The numerical results of production of heavy leptons of masses m = 0.5, 1, 2, 4 and 6 GeV from photons of energies 20, 40, 100 and 200 GeV are also given.
119194201
Global Study of the Simplest Scalar Phantom Dark Matter Model
We present a global study of the simplest scalar phantom dark matter model. The best fit parameters of the model are determined by simultaneously imposing (i) relic density constraint from WMAP, (ii) 225 live days data from direct experiment XENON100, (iii) upper limit of gamma-ray flux from Fermi-LAT indirect detection based on dwarf spheroidal satellite galaxies, and (iv) the Higgs boson candidate with a mass about 125 GeV and its invisible branching ratio no larger than 40% if the decay of the Higgs boson into a pair of dark matter is kinematically allowed. The allowed parameter space is then used to predict annihilation cross sections for gamma-ray lines, event rates for three processes mono-b jet, single charged lepton and two charged leptons plus missing energies at the Large Hadron Collider, as well as to evaluate the muon anomalous magnetic dipole moment for the model.
17688151
OLD FASHIONED PERTURBATION THEORY AND VECTOR MESON DOMINANCE
It is pointed out that the notion of vector meson dominance is best formulated in terms of old fashioned perturbation theory diagrams viewed in the Lorentz frame where the energy of the virtual photon q. is infinity, A more convincing way to derive Sakurai's result on ep inelastic scattering is presented. We give a simple way to understand why vector meson dominance does not give a correct transition form factor for the electro-excitation of V(1238).