Theory and phenomenology of two-Higgs-doublet models

A golden age for heavy-quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the B-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations at BESIII, the LHC, RHIC, FAIR, the Super Flavor and/or Tau-Charm factories, JLab, the ILC, and beyond. The list of newly found conventional states expanded to include h(c)(1P), chi(c2)(2P), B-c(+), and eta(b)(1S). In addition, the unexpected and still-fascinating X(3872) has been joined by more than a dozen other charmonium- and bottomonium-like "XYZ" states that appear to lie outside the quark model. Many of these still need experimental confirmation. The plethora of new states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c (c) over bar, b (b) over bar, and b (c) over bar bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. Lattice QCD has grown from a tool with computational possibilities to an industrial-strength effort now dependent more on insight and innovation than pure computational power. New effective field theories for the description of quarkonium in different regimes have been developed and brought to a high degree of sophistication, thus enabling precise and solid theoretical predictions. Many expected decays and transitions have either been measured with precision or for the first time, but the confusing patterns of decays, both above and below open-flavor thresholds, endure and have deepened. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.

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Heavy quarkonium: progress, puzzles, and opportunities

The Next-to-Minimal Supersymmetric Standard Model

We investigate the potential for the eLISA space-based interferometer to detect the stochastic gravitational wave background produced by strong first-order cosmological phase transitions. We discuss the resulting contributions from bubble collisions, magnetohydrodynamic turbulence, and sound waves to the stochastic background, and estimate the total corresponding signal predicted in gravitational waves. The projected sensitivity of eLISA to cosmological phase transitions is computed in a model-independent way for various detector designs and configurations. By applying these results to several specific models, we demonstrate that eLISA is able to probe many well-motivated scenarios beyond the Standard Model of particle physics predicting strong first-order cosmological phase transitions in the early Universe.

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Science with the space-based interferometer eLISA. II: Gravitational waves from cosmological phase transitions

micrOMEGAs 2.0.7: a program to calculate the relic density of dark matter in a generic model

We examine the possibility of electroweak baryogenesis and dark matter in the nMSSM, a minimal extension of the MSSM with a singlet field. This extension avoids the usual domain wall problem of the NMSSM, and also appears as the low energy theory in models of dynamical electroweak symmetry breaking with a so-called fat-Higgs boson. We demonstrate that a strong, first order electroweak phase transition, necessary for electroweak baryogenesis, may arise in regions of parameter space where the lightest neutralino provides an acceptable dark matter candidate. We investigate the parameter space in which these two properties are fulfilled and discuss the resulting phenomenology. In particular, we show that there are always two light CP-even and one light CP-odd Higgs bosons with masses smaller than about 250 GeV. Moreover, in order to obtain a realistic relic density, the lightest neutralino mass tends to be smaller than ${M}_{Z}/2,$ in which case the lightest Higgs boson decays predominantly into neutralinos.

Electroweak baryogenesis and dark matter in a minimal extension of the MSSM

The minimal supersymmetric extension of the standard model (MSSM) can provide the correct neutralino relic abundance and baryon number asymmetry of the universe. Both may be efficiently generated in the presence of $CP$ violating phases, light charginos and neutralinos, and a light top squark. Because of the coannihilation of the neutralino with the light stop, we find a large region of parameter space in which the neutralino relic density is consistent with WMAP and SDSS data. We perform a detailed study of the additional constraints induced when $CP$ violating phases, consistent with the ones required for baryogenesis, are included. We explore the possible tests of this scenario from present and future electron electric dipole moment (EDM) measurements, direct neutralino detection experiments, collider searches and the $b\ensuremath{\rightarrow}s\ensuremath{\gamma}$ decay rate. We find that the EDM constraints are quite severe and that electron EDM experiments, together with stop searches at the Tevatron and Higgs searches at the LHC, will provide a definite test of our scenario of electroweak baryogenesis in the next few years.

Supersymmetric Origin of Matter

We study the implications of minimal flavor violating low energy supersymmetry scenarios for the search of new physics in the $B$ and Higgs sectors at the Tevatron collider and the LHC. We show that the already stringent Tevatron bound on the decay rate ${B}_{s}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ sets strong constraints on the possibility of generating large corrections to the mass difference $\ensuremath{\Delta}{M}_{s}$ of the ${B}_{s}$ eigenstates. We also show that the ${B}_{s}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ bound together with the constraint on the branching ratio of the rare decay $b\ensuremath{\rightarrow}s\ensuremath{\gamma}$ has strong implications for the search of light, nonstandard Higgs bosons at hadron colliders. In doing this, we demonstrate that the former expressions derived for the analysis of the double penguin contributions in the Kaon sector need to be corrected by additional terms for a realistic analysis of these effects. We also study a specific nonminimal flavor violating scenario, where there are flavor changing gluino-squark-quark interactions, governed by the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements, and show that the $B$ and Higgs physics constraints are similar to the ones in the minimal flavor violating case. Finally we show that, in scenarios like electroweak baryogenesis which have light stops and charginos, there may be enhanced effects on the $B$ and $K$ mixing parameters, without any significant effect on the rate of ${B}_{s}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$.

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Constraints on B and Higgs physics in minimal low energy supersymmetric models

Electroweak baryogenesis in the minimal supersymmetric standard model can account for the cosmological baryon asymmetry, but only within a restricted region of the parameter space. In particular, minimal supersymmetric standard model electroweak baryogenesis requires a mostly right-handed stop that is lighter than the top quark and a standard model-like light Higgs boson. In the present work we investigate the effects of the light stop on Higgs boson production and decay. Relative to the standard model Higgs boson, we find a large enhancement of the Higgs production rate through gluon fusion and a suppression of the Higgs branching fraction into photon pairs. These modifications in the properties of the Higgs boson are directly related to the effect of the light stop on the electroweak phase transition, and are large enough that they can potentially be tested at the Tevatron and the LHC.

Higgs Boson Signatures of MSSM Electroweak Baryogenesis

We explore extensions of inelastic Dark Matter and Magnetic inelastic Dark Matter where the WIMP can scatter to a tower of heavier states. We assume a WIMP mass m
 χ ~ $ \mathcal{O} $
 (1-100) GeV and a constant splitting between successive states δ ~ $ \mathcal{O} $
 (1-100) keV. For the spin-independent scattering scenario we find that the direct experiments CDMS and XENON strongly constrain most of the DAMA/LIBRA preferred parameter space, while for WIMPs that interact with nuclei via their magnetic moment a region of parameter space corresponding to m
 χ ~ 11 GeV and δ < 15 keV is allowed by all the present direct detection constraints.

Arjun Menon

Papers

Electroweak baryogenesis and dark matter in a minimal extension of the MSSM

Supersymmetric Origin of Matter

Constraints on B and Higgs physics in minimal low energy supersymmetric models

Higgs Boson Signatures of MSSM Electroweak Baryogenesis

Magnetic fluffy dark matter