56 research outputs found
Cornering variants of Georgi-Machacek model using Higgs precision data
We show that in the absence of trilinear terms in the scalar potential of
Georgi-Machacek model, heavy charged scalars do not necessarily decouple from
the decay amplitude. In such scenarios, measurement of
the Higgs to diphoton signal strength can place stringent constraints in the
parameter space. Using the projected precisions at the High Luminosity LHC
(HL-LHC) and the ILC, we find that the upper bound on the triplet vacuum
expectation value can be as low as 10 GeV. We also found that when combined
with the theoretical constraints from perturbative unitarity and stability,
such variants may be ruled out altogether.Comment: 9 pages, 4 captioned figures. Accepted for publication in Phys. Rev.
Thermoelectric response in two-dimensional nodal-point semimetals
In this review, we discuss the computation of thermoelectric properties in
two-dimensional (2D) nodal-point semimetals with two bands, and show that the
expressions of the thermoelectric coefficients take different values depending
on the nature of the scattering mechanism responsible for transport. We
consider scatterings arising from short-ranged disorder potential and screened
charged impurities. In all the cases considered, an anisotropy in the band
spectrum invariably affects the thermopower quite significantly. We illustrate
this by comparing the results for a semi-Dirac semimetal with those for the
isotropic case (captured by the dispersion of a single valley of graphene). We
also consider the scenario when a magnetic field of magnitude is applied
perpendicular to the plane of the 2D semimetal. For a weak external magnetic
field, when we can ignore the formation of Landau levels, a complex dependence
of the thermopower on emerges for the anisotropic case. We also describe
the behaviour of the thermoelectric coefficients in the presence of a strong
quantizing magnetic field. Overall, the interplay of anisotropy and strengths
of the external fields provides a promising platform for achieving high
thermoelectric figure-of-merit.Comment: invited review article; includes the results reported in
arXiv:1811.0495
Thermopower in an anisotropic two-dimensional Weyl semimetal
We investigate the generation of an electric current from a temperature gradient in a two-dimensional Weyl semimetal with anisotropy in both the presence and absence of a quantizing magnetic field. We show that the anisotropy leads to doping dependences of thermopower and thermal conductivities which are different from those in isotropic Dirac materials. Additionally, we find that a quantizing magnetic field in such systems leads to an interesting magnetic field dependence of the longitudinal thermopower, resulting in unsaturated thermoelectric coefficients. Thus, the results presented here will serve as a guide to achieving high thermopower and a thermoelectric figure of merit in graphene-based materials, as well as organic conductors such as α-BEDT-TTF2I3.acceptedVersio
Little Higgs after the little one
At the LHC, the Littlest Higgs Model with -parity is characterised by
various production channels. If the -odd quarks are heavier than the exotic
partners of the and the , then associated production can be as important
as the pair-production of the former. Studying both, we look for final states
comprising at least one lepton, jets and missing transverse energy. We consider
all the SM processes that could conspire to contribute as background to our
signals, and perform a full detector level simulation of the signal and
background to estimate the discovery potential at the current run as well as at
the scheduled upgrade of the LHC. We also show that, for one of the channels,
the reconstruction of two tagged -jets at the Higgs mass provides us with an unambiguous hint for this model.Comment: 22 pages, 3 captioned figures, 8 Tables; minor modifications, version
published in JHE
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