High-scale validity of a two Higgs doublet scenario: metastability included

We make an attempt to identify regions in a Type II Two-Higgs Doublet Model, which correspond to a metastable electroweak vacuum with lifetime larger than the age of the universe. We analyse scenarios which retain perturbative unitarity up to Grand unification and Planck scales. Each point in the parameter space is restricted using Data from the Large Hadron Collider (LHC) as well as flavor and precision electroweak constraints. We find that substantial regions of the parameter space are thus identified as corresponding to metastability, which compliment the allowed regions for absolute stability, for top quark mass at the high as well as low end of its currently allowed range. Thus, a two-Higgs doublet scenario with the electroweak vacuum, either stable or metastable, can sail through all the way up to the Planck scale without facing any contradictions

Same-sign trileptons as a signal of sneutrino lightest supersymmetric partlcle

Contrary to common expectation, a left-sneutrinos can occasionally be the lightest supersymmet- ric particle. This has important implications in both collider and dark matter studies. We show that same-sign tri-lepton (SS3L) events at the Large Hadron Collider, with any lepton having opposite sign vetoed, distinguish such scenarios, up to gluino masses exceeding 2 TeV. The jets + M ET signal rate is somewhat suppressed in this case, thus enhancing the scope of leptonic signals.Comment: Version published in Phys.Lett.

High-scale validity of a two-Higgs doublet scenario: a study including LHC data

We consider the conditions for the validity of a two-Higgs doublet model at high energy scales, together with all other low- and high-energy constraints. The constraints on the parameter space at low energy, including the measured value of the Higgs mass and the signal strengths in channels are juxtaposed with the conditions of vacuum stability, perturbativity and unitarity at various scales. We find that a scenario with an exact $\mathbb{Z}_2$ symmetry in the potential cannot be valid beyond about 10 TeV without the intervention of additional physics. On the other hand, when the $\mathbb{Z}_2$ symmetry is broken, the theory can be valid even up to the Planck scale without any new physics coming in. The interesting feature we point out is that such high-scale validity is irrespective of the uncertainty in the top quark mass as well as $\alpha_{s}(M_Z)$, in contrast with the standard model with a single Higgs doublet. It is also shown that the presence of a CP-violating phase is allowed when the $\mathbb{Z}_2$ symmetry is relaxed. The allowed regions in the parameter space are presented for each case. The results are illustrated in the context of a Type-II scenario.Comment: 38 pages, 12 figures. Major changes in the presentation of some of the plots, minor changes in the text, references added, typos corrected, matches with published versio

Radiative Return for Heavy Higgs Boson at a Muon Collider

Higgs boson properties could be studied with a high accuracy at a muon collider via the s-channel resonant production. We consider the situation where the center-of-mass energy of the muon collider is off the resonance above the Higgs mass. We discuss the discovery potential for a generic heavy Higgs boson ($H$) and compare different production mechanisms, including the "radiative return" ($\gamma H$), $Z$-boson associated production ($ZH$) and heavy Higgs pair production ($HA$). These production mechanisms do not sensitively rely on a priori knowledge of the heavy Higgs boson mass. We include various types of Two Higgs Doublet Models for the comparison. We conclude that the radiative return process could provide an important option for both the heavy Higgs discovery and direct measurement of invisible decays at a high energy muon collider.Comment: 9 pages, 7 figure