Spencer Chang

Inelastic dark matter in light of DAMA/LIBRA

Inelastic dark matter, in which weakly interacting massive particle (WIMP)-nucleus scatterings occur through a transition to an excited WIMP state {approx}100 keV above the ground state, provides a compelling explanation of the DAMA annual modulation signal. We demonstrate that the relative sensitivities of various dark matter direct detection experiments are modified such that the DAMA annual modulation signal can be reconciled with the absence of a reported signal at CDMS-Soudan, XENON10, ZEPLIN, CRESST, and KIMS for inelastic WIMPs with masses O(100 GeV). We review the status of these experiments, and make predictions for upcoming ones. In particular, we note that inelastic dark matter leads to highly suppressed signals at low energy, with most events typically occurring between 20 and 45 keV (unquenched) at xenon and iodine experiments, and generally no events at low ({approx}10 keV) energies. Suppressing the background in this high-energy region is essential to testing this scenario. The recent CRESST data suggest seven observed tungsten events, which is consistent with expectations from this model. If the tungsten signal persists at future CRESST runs, it would provide compelling evidence for inelastic dark matter, while its absence should exclude it.

Nonstandard Higgs Boson Decays

This review summarizes the motivations for and the phenomenological consequences of nonstandard Higgs boson decays, with an emphasis on final states containing a pair of non–standard model particles that subsequently decay to standard model particles. Typically these non–standard model particles form part of a “hidden” sector, for example a pair of neutral Higgs bosons or a pair of unstable neutralinos. We emphasize that such decays allow for a Higgs substantially below the standard model Higgs Large Electron-Positron Collider limit of 114 GeV. A Higgs with standard model WW, ZZ, and top couplings and a mass near 100 GeV eliminates the fine-tuning problems of many beyond the standard model theories, in particular supersymmetric models, and leads to excellent consistency with precision electroweak data.

Naturalness and Higgs decays in the MSSM with a singlet

Preprint typeset in JHEP style - HYPER VERSION April 20, 2006 Naturalness and Higgs Decays in the MSSM with a Singlet Spencer Chang a , Patrick J. Fox b and Neal Weiner a a Center for Cosmology and Particle Physics, Dept. of Physics, New York University, New York, NY 10003 b Theoretical Physics Group, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 sc123@cosmo.nyu.edu, PJFox@lbl.gov, nw32@nyu.edu Abstract: The simplest extension of the supersymmetric standard model - the addition of one singlet superfield - can have a profound impact on the Higgs and its decays. We perform a general operator analysis of this scenario, focusing on the phenomenologically distinct scenarios that can arise, and not restricting the scope to the narrow framework of the NMSSM. We reexamine decays to four b quarks and four τ ’s, finding that they are still generally viable, but at the edge of LEP limits. We find a broad set of Higgs decay modes, some new, including those with four gluon final states, as well as more general six and eight parton final states. We find the phenomenology of these scenarios is dramatically impacted by operators typically ignored, specifically those arising from D-terms in the hidden sector, and those arising from weak-scale colored fields. In addition to sensitivity of m Z , there are potential tunings of other aspects of the spectrum. In spite of this, these models can be very natural, with light stops and a Higgs as light as 82 GeV. These scenarios motivate further analyses of LEP data as well as studies of the detection capabilities of future colliders to the new decay channels presented. Keywords: Higgs Physics, Supersymmetry Phenomenology.

Momentum dependent dark matter scattering

It is usually assumed that WIMPs interact through spin-independent and spin-dependent interactions. Interactions which carry additional powers of the momentum transfer, q2, are assumed to be too small to be relevant. In theories with new particles at the ~ GeV scale, however, these q2-dependent interactions can be large, and, in some cases dominate over the standard interactions. This leads to new phenomenology in direct detection experiments. Recoil spectra peak at non-zero energies, and the relative strengths of different experiments can be significantly altered. We present a simple parameterization for models of this type which captures much of the interesting phenomenology and allows a comparison between experiments. As an application, we find that dark matter with momentum dependent interactions coupling to the spin of the proton can reconcile the DAMA annual modulation result with other experiments.

New fat Higgs: Increasing the MSSM Higgs mass with natural gauge unification

In this paper we increase the MSSM tree level higgs mass bound to a value that is naturally larger than the LEP-II search constraint by adding to the superpotential a λSH u H d term, as in the NMSSM, and UV completing with new strong dynamics before λ becomes non-perturbative. Unlike other models of this type the higgs fields remain elementary, alleviating the supersym-metric fine-tuning problem while maintaining unification in a natural way.

Magnetic Inelastic Dark Matter

Iodine is distinguished from other elements used in dark matter direct detection experiments both by its large mass as well as its large magnetic moment. Inelastic dark matter utilizes the large mass of iodine to allay tensions between the dark matter (DAMA) annual modulation signature and the null results from other experiments. We explore models of inelastic dark matter that also take advantage of the second distinct property of iodine, namely, its large magnetic moment. In such models the couplings are augmented by magnetic, rather than merely electric, interactions. These models provide simple examples where the DAMA signal is compatible with all existing limits. We consider dipole moments for the WIMP, through conventional magnetism as well as dark magnetism, including both magnetic-magnetic and magnetic-electric scattering. We find XENON100 and Cryogenic Rare Event Search with Superconducting Thermometers (CRESST) should generically see a signal although suppressed compared with electric inelastic dark matter models, while Korea Invisible Mass Search (KIMS) should see a modulated signal comparable to or larger than that of DAMA. In a large portion of parameter space, deexcitation occurs promptly, producing a ~100 keV photon inside large xenon experiments alongside the nuclear recoil. This effect could be searched for, but if not properly considered may cause nuclear recoil events to fail standard cuts.

Supersymmetric twin Higgs mechanism

We present a supersymmetric realization of the twin Higgs mechanism, which cancels off all contributions to the Higgs mass generated above a scale f. Radiative corrections induced by the top quark sector lead to a breaking of the twin sector electroweak symmetry at a scale f ∼ TeV. In our sector, below the scale f , these radiative corrections from the top quark are present but greatly weakened, naturally allowing a Z boson mass an order of magnitude below f , even with a top squark mass of order 1 TeV and a messenger scale near the Planck mass. A sufficient quartic interaction for our Higgs boson arises from the usual gauge contribution together with a radiative contribution from a heavy top squark. The mechanism requires the presence of an SU (2)-adjoint superfield, and can be simply unified. Naturalness in these theories is usually associated with light winos and sleptons, and is largely independent of the scale of the colored particles. The assumption of unification naturally predicts the existence of many exotic fields. The theory often has particles which may be stable on collider timescales, including an additional color octet superfield. In the limit that m SU SY ≫ f , the mechanism yields a UV completion of the non-supersymmetric twin Higgs, and with the notable improvement of a tree-level quartic for the standard model Higgs. In this framework, a successful UV completion requires the existence of new charged fields well below the scale f .

Simple U ( 1 ) gauge theory explanation of the diphoton excess

The recent ATLAS and CMS diphoton resonance excesses are explored in a simple

Using the energy spectrum measured by DAMA/LIBRA to probe light dark matter

U(1)

Visible Cascade Higgs Decays to Four Photons at Hadron Colliders

gauge theory extension of the Standard Model where the resonance is the Higgs boson of the