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.
118689661
Dark matter and collider signatures of the MSSM
We explore the MSSM with 9 free parameters (p9MSSM) that have been selected as a minimum set that allows an investigation of neutralino dark matter and collider signatures while maintaining consistency with several constraints. These include measurement of the dark matter relic density from PLANCK, main properties of the discovered Higgs boson, LHC direct SUSY searches, recent evidence for a Standard Model-like BR(Bs -> \mu+ \mu-), and the measurement of \delta(g-2), plus a number of other electroweak and flavor physics constraints. We perform a simulation of two LHC direct SUSY searches at sqrt(s)=8 TeV: the CMS inclusive \alpha_T search for squarks and gluinos and the CMS electroweak production search with 3l+E_T^miss in the final state. We use the latter to identify the regions of the parameter space, consistent at 2\sigma\ with \delta(g-2), that are not excluded by the direct limits from the electroweak production. We find that they correspond to a neutralino mass in the window 200 GeV<m_\chi<500 GeV. We also implement the likelihood for the XENON100 exclusion bound, in which we consider for the first time the impact of a recent determination of the \Sigma_{\pi N} term from CHAOS data, \Sigma_{\pi N}=43\pm12 MeV. We show that in light of this measurement, the present statistical impact of the XENON100 bound is greatly reduced, although future sensitivities of the LUX and XENON1T experiments will have decisive impact on the mixed bino/higgsino composition of the neutralino. We point out some tension between the constraints from \delta(g-2) and XENON100. Finally, we present prospects for various indirect searches of dark matter, namely \gamma-ray fluxes from dSphs and the Galactic Center at Fermi-LAT, and the positron flux at AMS02. We also show the 5-year sensitivity on the spin-dependent neutralino-proton cross section due to neutrino fluxes from the Sun at IceCube.
119110843
Bayesian implications of current LHC supersymmetry and dark matter detection searches for the constrained MSSM
We investigate the impact of recent limits from LHC searches for supersymmetry and from direct and indirect searches for dark matter on global Bayesian inferences of the parameter space of the Constrained Minimal Supersymmetric Standard Model (CMSSM). In particular we apply recent exclusion limits from the CMS \alpha_T analysis of 1.1/fb of integrated luminosity, the current direct detection dark matter limit from XENON100, as well as recent experimental constraints on \gamma-ray fluxes from dwarf spheroidal satellite galaxies of the Milky Way from the FermiLAT telescope, in addition to updating values for other non-LHC experimental constraints. We extend the range of scanned parameters to include a significant fraction of the focus point/hyperbolic branch region. While we confirm earlier conclusions that at present LHC limits provide the strongest constraints on the model's parameters, we also find that when the uncertainties are not treated in an excessively conservative way, the new bounds from dwarf spheroidal have the power to significantly constrain the focus point/hyperbolic branch region. Their effect is then comparable, if not stronger, to that from XENON100. We further analyze the effects of one-year projected sensitivities on the neutrino flux from the Sun in the 86-string IceCube+DeepCore configuration at the South Pole. We show that data on neutrinos from the Sun, expected for the next few months at IceCube and DeepCore, have the potential to further constrain the same region of parameter space independently of the LHC and can yield additional investigating power for the model.
199669313
The CMSSM Favoring New Territories: The Impact of New LHC Limits and a 125 GeV Higgs
18956502
Global fits of the Non-Universal Higgs Model
We examine the Non-Universal Higgs Model (NUHM) with the help of a Markov Chain Monte Carlo scanning technique and Bayesian statistics. The method allows us to reveal more fully the remarkably rich and complex structure of the model and also some new interesting features. In particular we find that, for large ranges of parameters, the neutralino dark matter in the model is higgsino-like with mass close to 1 TeV. This feature does depend to some extent on the prior but generically results from a mild focussing effect in the running of one of the Higgs masses that we also point out. On the other hand, the usual bino-like neutralino is also present, and in some sense is favored by a more robust prior and a better average chi–square. In spite of experimental constraints often favoring different regions of parameter space than in the Constrained MSSM, most observational consequences appear fairly similar, which will make it challenging to experimentally distinguish the two models.
118612935
The impact of propagation uncertainties on the potential Dark Matter contribution to the Fermi LAT mid-latitude gamma-ray data
We investigate the extent to which the uncertainties associated with the propagation of Galactic cosmic rays impact upon estimates for the {gamma}-ray flux from the mid-latitude region. We consider contributions from both standard astrophysical background (SAB) processes as well as resolved point sources. We have found that the uncertainties in the total {gamma}-ray flux from the mid-latitude region relating to propagation parameter values consistent with local B/C and {sup 10}Be/{sup 9}Be data dominate by 1-2 orders of magnitude. These uncertainties are reduced to less than an order of magnitude when the normalizations of the SAB spectral components are fitted to the corresponding Fermi LAT data. We have found that for many propagation parameter configurations (PPCs) our fits improve when an extragalactic background (EGB) component is simultaneously fitted to the data. We also investigate the improvement in our fits when a flux contribution from neutralino dark matter (DM), described by the minimal supersymmetric standard model, was simultaneously fitted to the data. We consider three representative cases of neutralino DM for both Burkert and Einasto DM density profiles, in each case simultaneously fitting a boost factor of the DM contribution together with the SAB and EGB components. We have found that formore » several PPCs there are significant improvements in our fits, yielding both substantial EGB and DM components, where for a few of these PPCs the best-fit EGB component is consistent with recent estimates by the Fermi Collaboration.« less
123425178
The signature of sequential charged leptons
I am honored to be invited to give a talk on this occasion to celebrate Martin Perl`s 65th birthday. John Jaros, the organizer of this occasion, wanted me to recollect several things, especially: what motivated me to write my 1971 Physical Review paper on the heavy lepton entitled ``Decay Correlations of Heavy Lepton in e{sup minus} + e{sup +} = {ell}{sup -} + {ell}+;`` why did I think of muon-electron coincidence; and what were the contributions of Thacker and Sakurai. In this paper I answer his requests and add something else later.
51428350
Soft RPV through the baryon portal
A bstractSupersymmetric (SUSY) models with R-parity generically predict sparticle decays with invisible neutralinos, which yield distinctive missing energy events at colliders. Since most LHC searches are designed with this expectation, the putative bounds on sparticle masses become considerably weaker if R-parity is violated so that squarks and gluinos decay to jets with large QCD backgrounds. Here we introduce a scenario in which baryonic R-parity violation (RPV) arises effectively from soft SUSY breaking interactions, but leptonic RPV remains accidentally forbidden to evade constraints from proton decay and FCNCs. The model features a global R-symmetry that initially forbids RPV interactions, a hidden R-breaking sector, and a heavy mediator that communicates this breaking to the visible sector. After R-symmetry breaking, the mediator is integrated out and an effective RPV A-term arises at tree level; RPV couplings between quarks and squarks arise only at loop level and receive additional suppression. Although this mediator must be heavy compared to soft masses, the model introduces no new hierarchy since viable RPV can arise when the mediator mass is near the SUSY breaking scale. In generic regions of parameter space, a light thermally-produced gravitino is stable and can be a viable dark matter candidate.
8001359
My recollections as a physicist
This presentation is a talk presented by the author at a Physics Symposium of the 50th anniversary of the Taiwan University, in December 1996. The author describes how he became a physicist, and then presents a brief outline of his professional career, most of which has centered at Stanford Linear Accelerator Center. He was involved in the discovery of the {tau} lepton, and in studies of CP violation through decay of the {tau}, in addition to studies of semileptonic decay of t, B, D, K, and {pi}.
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.