13561911
Addendum to the test of CP violation in Tau decay
We discuss the test of CP and CPT violation in τ decay without using the polarized electron beam by comparing partial fractions of τ− and τ+ decay into channels with strong final state interactions. For example, Γ(τ−→π−+π0+ν)≠Γ(τ+→π++π0+ν) signifies violation of CP. The optimum energy to investigate CP violation in τ decay is discussed. We conclude that this energy is a few MeV below ψ(2s) in order to avoid the charm contribution and over abundance of hadrons at the ψ(2s) peak.
17739913
Production of polarized tau pairs and tests of CP violation using polarized e+/- colliders near threshold.
We consider the production of [tau] pairs by electron-positron colliding beams at the maximum cross section near the threshold. At this energy [tau] pairs are produced mostly in the [ital s] wave which implies that the spin of the [tau] pairs is almost always pointing in the beam direction independent of the production angle. When both electrons and positrons are longitudinally polarized in the same direction, for example, 90%, one can obtain [tau] pairs with 99% polarization in the direction of the polarization vectors of the incident beams. Tests of [ital CP] violation and study of the structure of weak interactions using such polarized [tau] pairs is discussed.
9460084
Production of neutral bosons by an electron beam.
We investigate the possible existence of neutral bosons which are coupled to leptons. The cross section for the process /ital e/+/ital p//r arrow//ital e/+/ital X/+anything, where /ital X/ is a neutral boson of spin-parity 0/sup /plus minus// of 1/sup /plus minus// emitted by the electron, is calculated and its energy-angle distribution discussed. Assuming /ital X/ to decay predominantly into a lepton pair we investigate the characteristics of the background. It is pointed out that the signal-to-background ratio can be greatly enhanced if one selects high /ital x/=/ital E//sub /ital X///E/sub 1/ and also uses the outgoing electron as a tag at a slightly nonforward angle with the /ital X/ particle arranged in such a way that the momentum transfer to the target particle is near its minimum. This happens when the outgoing electron momentum /bold P//sub 2/ is parallel to /bold P//sub 1//minus//bold k/, where /bold P//sub 1/ and /bold k/ are the momenta of the incident electron and the /ital X/ particle, respectively.
122447425
MUONS AND ELECTROMAGNETIC INTERACTION AT NAL: A THEORIST'S VIEW.
126593847
TRIP TO PEOPLE'S REPUBLIC OF CHINA AND JAPAN: AUGUST 1 TOSEPTEMBER 4, 1978
11506221
Axion bremsstrahlung by an electron beam.
Compact expressions for energy-angle distribution and energy distribution for axion from electron scattering on an atomic target are derived using the generalized Weizsacker-Williams method. The axion flux from an electron beam dump is estimated. It is also shown that even in a proton beam dump, the mechanism of producing axions is still predominantly due to electrons in the dump.
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.
59134775
A generic method to constrain the dark matter model parameters from Fermi observations of dwarf spheroids
Observation of gamma-rays from dwarf galaxies is an effective way to search for particle dark matter. Using 4-year data of Fermi-LAT observations on a series of Milky Way satellites, we develop a general way to search for the signals from dark matter annihilation in such objects. Instead of giving prior information about the energy spectrum of dark matter annihilation, we bin the Fermi-LAT data into several energy bins and build a likelihood map in the "energy bin - flux" plane. The final likelihood of any spectrum can be easily derived through combining the likelihood of all the energy bins. It gives consistent result with that directly calculated using the Fermi Scientific Tool. This method is very efficient for the study of any specific dark matter models with gamma-rays. We use the new likelihood map with Fermi-LAT 4 year data to fit the parameter space in three representative dark matter models: i) toy dark matter model, ii) effective dark matter operators, and iii) supersymmetric neutralino dark matter.
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
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.
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.