arXiv subjects

ShivaSankar K. A

Publications and source records attributed to ShivaSankar K. A.

3 recordsLinked to original sources

arXiv2025

Right handed neutrino production from $Z^\prime$ interactions in forward search experiments

We study two general $U(1)$ extensions of the Standard Model (SM) those generate tiny neutrino masses via the seesaw mechanism after general $U(1)$ breaking. These models predict a new neutral gauge boson ($Z'$) and right-handed neutrinos (RHNs), the latter introduced for anomaly cancellation and neutrino mass generation. In both scenarios, left- and right-handed fermions couple differently to the $Z'$, and RHNs mix with light neutrinos, enabling variety of decay modes. Focusing on the high-luminosity LHC (HL-LHC) and the future FASER2 experiment, we explore RHN pair production from $Z'$ decays in two cases: (i) long-lived $Z'$ decays to visible modes and long-lived RHNs, and (ii) short-lived $Z'$ decays to long-lived RHNs, which further decay visibly inside FASER2. We estimate projected limits on the general $U(1)$ gauge coupling, $Z'$ mass, RHN mass, and light-heavy neutrino mixing for various $U(1)$ charge assignments, and compare them with current experimental bounds.

hep-ph↗

arXiv2023

CDF-II $W$ Boson Mass Anomaly in the Canonical Scotogenic Neutrino-Dark Matter Model

The CDF-II collaboration's recent high-precision measurement of $W$ boson mass indicates new physics contribution(s) beyond the Standard Model. We investigate the possibility of the well-known canonical Scotogenic model to explain the CDF-II measurement. The Scotogenic model is a popular scenario beyond the Standard Model that induces neutrino masses at the 1-loop level and includes a viable dark matter candidate, either scalar or fermionic. For both scalar and fermionic dark matter possibilities, we simultaneously examine the constraints coming from (a) neutrino mass, oscillation, neutrinoless double beta decay and lepton flavour violation experiments, (b) from LEP and LHC (c) from dark matter relic density and direct detection experiments (d) from the oblique $S,T,U$ parameter values consistent with CDF-II $W$ boson measurement. We demonstrate that the new CDF-II measurement rules out the feasible parameter space of the scalar dark matter in the high mass regions ($m_{η_{R}} \gtrsim 500~\text{GeV}$), while still allowing the intermediate mass regions $54~\text{GeV} \lesssim m_{η_{R}} \lesssim 76~\text{GeV}$. We also showed that the fermionic dark matter candidate in the canonical Scotogenic model, in the range $M_{N_{1}} \lesssim 500~\text{GeV} $ , can simultaneously explain all the aforementioned issues. Furthermore, we investigated how the recent findings from ATLAS 2023 impact this study.

hep-ph↗

arXiv2022

W boson mass in Singlet-Triplet Scotogenic dark matter model

The recent high precision measurement of $W$ boson mass by CDF-II collaboration points to the contribution(s) of new physics beyond the Standard Model. One of the minimalistic ways to account for the anomalous $W$ boson mass is by introducing a hyperchargeless real $SU(2)_L$ triplet scalar whose vacuum expectation value explicitly contributes to the $W$ boson mass at the tree level while the $Z$ boson mass remains the same. Such a triplet can be naturally embedded in a singlet-triplet scotogenic model for one loop neutrino mass generated by dark sector particles running in the loop. We discuss the detailed phenomenology of the model, obtaining the parameter space consistent with the CDF-II $W$ boson mass measurements. The dark matter as well as the constraints comings from $S$, $T$, $U$ parameters are also analyzed.

hep-ph↗