Theory and phenomenology of two-Higgs-doublet models

The Next-to-Minimal Supersymmetric Standard Model

Motivated by the recent LHC hints of a Higgs boson around 125 GeV, we assume a SM-like Higgs with the mass 123-127 GeV and study its implication in low energy SUSY by comparing the MSSM and NMSSM. We consider various experimental constraints at 2 sigma level (including the muon g - 2 and the dark matter relic density) and perform a comprehensive scan over the parameter space of each model. Then in the parameter space which is allowed by current experimental constraints and also predicts a SM-like Higgs in 123-127 GeV, we examine the properties of the sensitive parameters (like the top squark mass and the trilinear coupling A(t)) and calculate the rates of the di-photon signal and the VV* (V = W, Z) signals at the LHC. Our typical findings are: (i) In the MSSM the top squark and A(t) must be large and thus incur some fine-tuning, which can be much ameliorated in the NMSSM; (ii) In the MSSM a light stau is needed to enhance the di-photon rate of the SM-like Higgs to exceed its SM prediction, while in the NMSSM the di-photon rate can be readily enhanced in several ways; (iii) In the MSSM the signal rates of pp -> h -> VV* at the LHC are never enhanced compared with their SM predictions, while in the NMSSM they may get enhanced significantly; (iv) A large part of the parameter space so far survived will be soon covered by the expected XENON100(2012) sensitivity (especially for the NMSSM).

A SM-like Higgs near 125 GeV in low energy SUSY: a comparative study for MSSM and NMSSM

Taking into account spins, we classify all two-body non-relativistic Dark Matter annihilation channels to the allowed polarization states of Standard Model particles, computing the energy spectra of the stable nal-state particles relevant for indirect DM detection. We study the DM masses, annihilation channels and cross sections that can reproduce the PAMELA indications of an e + excess consistently with the PAMELA p data and the ATIC/PPB-BETS e + +e data. From the PAMELA data alone, two solutions emerge: (i) either the DM particles that annihilate into W;Z;h must be heavier than about 10 TeV or (ii) the DM must annihilate only into leptons. Thus in both cases a DM particle compatible with the PAMELA excess seems to have quite unexpected properties. The solution (ii) implies a peak in the e + +e

Model-independent implications of the e , p cosmic ray spectra on properties of Dark Matter (updated including AMS 2013 data)

Neutrinos are the only particles in the Standard Model (SM) of particle physics that have only been observed with left handed chirality to date. If right handed (RH) neutrinos exist, they could be responsible for several phenomena that have no explanation within the SM, including neutrino oscillations, the baryon asymmetry of the universe, dark matter (DM) and dark radiation (DR). After a pedagogical introduction, we review recent progress in the phenomenology of RH neutrinos. We in particular discuss the mass ranges suggested by hints for neutrino oscillation anomalies and DR (eV), sterile neutrino DM scenarios (keV) and experimentally testable theories of baryogenesis (GeV to TeV). We summarize constraints from theoretical considerations, laboratory experiments, astrophysics and cosmology for each of these.

http://inspirehep.net/record/1225646/files/arXiv:1303.6912.pdf

The Phenomenology of Right Handed Neutrinos

Light dark matter in NMSSM and implication on Higgs phenomenology

We split the two-Higgs-doublet model by assuming very different vevs for the two doublets: the vev is at weak scale (174 GeV) for the doublet Phi(1) and at neutrino-mass scale (10(-2) - 10(-3) eV) for the doublet Phi(2). Phi(1) is responsible for giving masses to all fermions except neutrinos; while Phi(2) is responsible for giving neutrino masses through its tiny vev without introducing the see-saw mechanism. Among the predicted five physical scalars H, h, A(0) and H-+/-, the CP-even scalar h is as light as 10(-2) - 10(-3) eV while the others are at weak scale. We identify h as the cosmic-dark-energy field and the other CP-even scalar H as the Standard Model Higgs boson; while the CP-odd A(0) and the charged H-+/- are the exotic scalars to be discovered at future colliders. Also we demonstrate a possible dynamical origin for the doublet Phi(2) from neutrino condensation caused by some unknown dynamics.

Split two-Higgs-doublet model and neutrino condensation

Very recently, the XENON1T Collaboration has reported an intriguing electron recoil excess, which may imply light dark matter. To interpret this anomaly, we propose the atmospheric dark matter (ADM) from the inelastic collision of cosmic rays (CRs) with the atmosphere. Because of the boost effect of high-energy CRs, we show that the light ADM can be fast moving and successfully fit the observed electron recoil spectrum through the ADM-electron scattering process. Meanwhile, our ADM predicts the scattering cross section ${\ensuremath{\sigma}}_{e}\ensuremath{\sim}\mathcal{O}({10}^{\ensuremath{-}38}\ensuremath{-}{10}^{\ensuremath{-}39}\text{ }\text{ }{\mathrm{cm}}^{2}$) and thus can evade other direct detection constraints. The search for light meson rare decays, such as $\ensuremath{\eta}\ensuremath{\rightarrow}\ensuremath{\pi}+{\overline{)E}}_{T}$, would provide a complementary probe of our ADM in the future.

Atmospheric dark matter and XENON1T excess

The Higgs-pair production process at the CERN Large Hadron Collider, which will provide a way to test the Higgs boson self-coupling, may be sensitive to new physics. In the framework of the littlest Higgs model with T parity, such Higgs-pair production can proceed through additional loop diagrams, and thus the production rate can be quite different from the standard model prediction. Our calculations show that, due to the loop contributions of both T-even and T-odd quarks predicted in this model, the production rate can be significantly enhanced relative to the standard model prediction and also can be larger than the production rate in the minimal supersymmetric model. Also, we find that the T-odd quark contributions, which were not included in a previous study, are equally important compared with the T-even quark contributions.

Higgs-pair production in littlest Higgs model with T parity

In this work, we explain the recent observed 750 GeV diphoton resonance in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) by introducing vector-like chiral superfields. Such an extension is well motivated from the top-down view since some grand unified theories usually predict the existence of singlet scalars and vector-like particles at weak scale. In our model, the 750 GeV resonance can be interpreted as two nearly degenerate singlet-like Higgs bosons (mh2 ≈ ma1 ≈ 750 GeV). The decays of h2/a1 → are dominated by the vector-like squarks with large mixing, which can also enhance the production cross section of gg → h2/a1. Under the constraints from the Higgs data and dark matter detection, we scan the parameter space and find that such a model can successfully accounts for the diphoton excess.

Wenyu Wang

Papers

Light dark matter in NMSSM and implication on Higgs phenomenology

Split two-Higgs-doublet model and neutrino condensation

Atmospheric dark matter and XENON1T excess

Higgs-pair production in littlest Higgs model with T parity

Interpreting 750 GeV Diphoton Resonance in the NMSSM with Vector-like Particles