We study several aspects of electroweak vacuum metastability when an extra gauge singlet scalar, a viable candidate for a dark matter particle, is added to the standard model of particle physics, which is assumed to be valid up to the Planck scale. Phase diagrams are drawn for different parameter spaces, and based on that, we graphically demonstrate how the confidence level, at which stability of electroweak vacuum is excluded, depends on such new physics parameters.
The inert scalar doublet model of dark matter can be valid up to the Planck scale. We briefly review the bounds on the model in such a scenario and identify parameter spaces that lead to absolute stability and metastability of the electroweak vacuum. * phd11125102@iiti.ac.in † rakshit@iiti.ac.in 1 arXiv:1503.03085v2 [hep-ph] 2 Sep 2015
We revisit the multilepton (ml) + E / T + X signatures of the Inert Doublet Model (IDM) of dark matter in future LHC experiments for m = 3, 4 and simulate, for the first time, the m = 5 case. Here X stands for any number of jets. We illustrate these signals with benchmark points consistent with the usual constraints like unitarity, perturbativity, the precision electroweak data, the observed dark matter relic density of the Universe and, most importantly, the stringent LHC constraints from the post Higgs (h) discovery era like the measured M h and the upper bound on the invisible width of h decay which were not included in earlier analyses of multilepton signatures. We find that if the IDM model is embedded in a grand dessert scenario so that the unitarity constraint holds up to a very high scale, the whole of the highly restricted parameter space allowed by the above constraints can be probed at the LHC via the 3l signal for an integrated luminosity ∼ 3000 fb −1 . On the other hand, if any new physics shows up at a scale ∼ 10 TeV, only a part of the enlarged allowed parameter space can be probed. The 4l and 5l signals can help to discriminate among different IDM scenarios as and when sufficient integrated luminosity accumulates.
We promote the idea of multi-component Dark Matter (DM) to explain results from both direct and indirect detection experiments. In these models as contribution of each DM candidate to relic abundance is summed up to meet WMAP/Planck measurements of Ω DM , these candidates have larger annihilation cross-sections compared to the single-component DM models. This results in larger γ-ray flux in indirect detection experiments of DM. We illustrate this fact by introducing an extra scalar to the popular single real scalar DM model. We also present detailed calculations for the vacuum stability bounds, perturbative unitarity and triviality constraints on this model. As direct detection experimental results still show some conflict, we kept our options open, discussing different scenarios with different DM mass zones. In the framework of our model we make an interesting observation: The existing direct detection experiments like CDMS II, CoGeNT, CRESST II, XENON 100 or LUX together with the observation of excess low energy γ-ray from Galactic Centre and Fermi Bubble by FGST already have the capability to distinguish between different DM halo profiles. 1 kamakshya.modak@saha.ac.in 2 debasish.majumdar@saha.ac.in 3 rakshit@iiti.ac.in 1 arXiv:1312.7488v2 [hep-ph]
We explore the possibility that high energy astrophysical neutrinos can interact with the dark matter on their way to Earth. Keeping in mind that new physics might leave its signature at such energies, we have considered all possible topologies for effective interactions between neutrino and dark matter. Building models, that give rise to a significant flux suppression of astrophysical neutrinos at Earth, is rather difficult. We present a Z -mediated model in this context. Encompassing a large variety of models, a wide range of dark matter masses from 10 −21 eV up to a TeV, this study aims at highlighting the challenges one encounters in such a model building endeavour after satisfying various cosmological constraints, collider search limits and electroweak precision measurements. *
We study the CP even trilinear neutral gauge boson vertices at one-loop in the context of the Standard Model and the Minimal Supersymmetric Standard Model, assuming two of the vector bosons are on-shell. We also study the changes in the form-factors when these two bosons are off-shell.
We present a complete (non-redundant) basis of CP- and flavour-conserving
six-dimensional operators in a two Higgs doublet model (2HDM). We include
Z_2-violating operators as well. In such a 2HDM effective field theory
(2HDMEFT), we estimate how constraining the 2HDM parameter space from
experiments can get disturbed due to these operators. Our basis is motivated by
the strongly interacting light Higgs (SILH) basis used in the standard model
effective field theory (SMEFT). We find out bounds on combinations of Wilson
coefficients of such operators from precision observables, signal strengths of
Higgs decaying into vector bosons etc. In 2HDMEFT, the 2HDM parameter space can
play a significant role while deriving such constraints, by leading to reduced
or even enhanced effects compared to SMEFT in certain processes. We also
comment on the implications of the SILH suppressions in such considerations.Comment: 34 pages, 6 figures; to appear in JHE
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