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.
119226535
LEP shines light on dark matter
Dark matter pair production at high energy colliders may leave observable signatures in the energy and momentum spectra of the objects recoiling against the dark matter. We use LEP data on mono-photon events with large missing energy to constrain the coupling of dark matter to electrons. Within a large class of models, our limits are complementary to and competitive with limits on dark matter annihilation and on WIMP-nucleon scattering from indirect and direct searches. Our limits, however, do not suer from systematic and astrophysical uncertainties associated with direct and indirect limits. For example, we are able to rule out light (. 10 GeV) thermal relic dark matter with universal couplings exclusively to charged leptons. In addition, for dark matter mass below about 80 GeV, LEP limits are stronger than Fermi constraints on annihilation into charged leptons in dwarf spheroidal galaxies. Within its kinematic reach, LEP also provides the strongest constraints on the spin-dependent direct detection cross section in models with universal couplings to both quarks and leptons. In such models the strongest limit is also set on spin independent scattering for dark matter masses below 4 GeV. Throughout our discussion, we consider both low energy eective theories of dark matter, as well as several motivated renormalizable scenarios involving light mediators.
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.
119216213
Electroweak baryogenesis in R -symmetric supersymmetry
We demonstrate that electroweak baryogenesis can occur in a supersymmetric model with an exact R-symmetry. The minimal R-symmetric supersymmetric model contains chiral superfields in the adjoint representation, giving Dirac gaugino masses, and an additional set of "R-partner" Higgs superfields, giving R-symmetric \mu-terms. New superpotential couplings between the adjoints and the Higgs fields can simultaneously increase the strength of the electroweak phase transition and provide additional tree-level contributions to the lightest Higgs mass. Notably, no light stop is present in this framework, and in fact, we require both stops to be above a few TeV to provide sufficient radiative corrections to the lightest Higgs mass to bring it up to 125 GeV. Large CP-violating phases in the gaugino/higgsino sector allow us to match the baryon asymmetry of the Universe with no constraints from electric dipole moments due to R-symmetry. We briefly discuss some of the more interesting phenomenology, particularly of the of the lightest CP-odd scalar.
28833775
Leptonic decay of heavy leptons
The energy angle distribution of a light charged lepton R from the decay of an arbitrary polarized heavy charged lepton L, L-+ v L + ;i, + R-, is derived assuming that: 1) the mass of vL is not zero; 2) the coupling of WLVL can be arbitrary combinations of V and A. The case when v and 3 R are identical is also discussed. L * Work supported by the Department of Energy under Contract No. EY-76-C-03-0515.
12584737
Improved Weizsaecker--Williams method and its application to lepton and W- boson pair production
A Weishcker-Williams method is derived which handles the elastic and inelastic target form factors properly. The method is applied to calculate energy-angle distributions of photoproduced lepton pairs: electrons, muons, and heavy leptons, using target form factors appropriate to each case. The agreement with the exact result is found to be excellent. Simple formulas for pair production of spin-0 and spin-1 particles are also given. (auth)
117289375
PHENOMENOLOGICAL ANALYSIS OF THE gamma N N* FORM-FACTORS
The data on electroexcitation of ${N}^{*}$ in the momentum-transfer range $\ensuremath{-}{q}^{2}=0.1\ensuremath{-}2.33$ Ge${\mathrm{V}}^{2}$ have been analyzed phenomenologically, using an isobar model. Assuming only the $M1$ transition, we obtained a phenomenological form factor for the $\ensuremath{\gamma}N{N}^{*}$ vertex. This form factor is found to decrease much faster than the elastic nucleon form factors. This implies that the ${N}^{*}$ has a larger spatial extension than the $N$.
16481276
Search for new mechanism of CP violation through decay of leptons and semileptonic decay of hadrons
If CP is violated in any decay process involving leptons it will signify the existence of a new scalar boson (called the X boson) responsible for CP violation that may be the key to understanding matter-antimatter asymmetry in the universe. The authors discuss the signatures of CP violation in (1) the decay of tau and mu leptons, and (2) the semileptonic decay of {pi}, K, D, B and t particles by measuring the polarization of the charged lepton in the decay. The authors discuss how the coupling constants and their phases of the coupling of the X boson to 9 quark vertices and 3 lepton vertices can be obtained through 12 decay processes.
121243747
Intermediate Boson Pair Production as a Means for Determining its Magnetic Moment
It is shown that, under the assumption of zero anomalous quadrupole moment, the photproduction of intermediate boson pairs on protons has a cross section that is very sensitive to the magnetic moment. The photoproduction cross section for intermediate boson pairs on iron is also calculated. (C.E.S.)