Najimuddin Khan

We study a scotogenic model augmented with an additional U ( 1 ) gauge and a discrete Z 2 symmetry. The lightest Z 2 -odd particle in our model becomes the dark matter (DM) candidate while tiny neutrino masses are realized at one loop. We explore the parameter space of the model for which the DM relic density is satisfied, and the correct low-energy neutrino observables are reproduced. The extended gauge symmetry includes a beyond Standard Model (SM) particle spectrum consisting of vectorlike fermions and scalars. We also highlight possible collider signatures of these particles at the LHC.

We conduct a comprehensive investigation into the flavor phenomenology and collider signatures of flavon of Z N × Z M flavor symmetries for the soft symmetry-breaking scenario and a new symmetry-conserving mechanism at the high-luminosity LHC, high-energy LHC, and a 100 TeV hadron collider. The flavor physics of quark and leptonic observables places different bounds on the parameter space of flavons of Z N × Z M flavor symmetries. On the collider side, the decay t → c a can be probed by the high-luminosity LHC, high-energy LHC, and a 100 TeV hadron collider for the Z 8 × Z 22 flavor symmetry. The inclusive production signatures can be used to probe the flavon of all the Z N × Z M flavor symmetries for the soft symmetry-breaking scenario for a heavy flavon at a 100 TeV collider. Flavons of all the Z N × Z M flavor symmetries can be probed at high-energy LHC and a 100 TeV collider for a low mass in the case of soft symmetry breaking. The diflavon production is within reach of the high-luminosity LHC, high-energy LHC, and a 100 TeV collider only for a light flavon. The 14 TeV high-luminosity LHC can probe only the Z 2 × Z 5 and Z 8 × Z 22 flavor symmetries for a few specific inclusive signatures. The symmetry-conserving scenario remains beyond the detection capabilities of any collider. Published by the American Physical Society 2024

In the absence of any new physics signals at the Large Hadron Collider (LHC), anomalous results at low energy experiments have become the subject of increased attention. We focus on three such results from the LSND, MiniBooNE (MB), and ATOMKI experiments. A 17 MeV pseudoscalar mediator (a ^′) can account for two (⁸Be and ⁴He) out of the three cases in which excess events have been seen in pair creation transitions in ATOMKI. We incorporate this mediator in a gauge invariant extension of the Standard Model (SM) with a second Higgs doublet and three singlet (seesaw) neutrinos (N _i , i = 1, 2, 3). N _1,2 participate in an interaction in MB and LSND which, with a ^′ as mediator, leads to the production of e ⁺ e ⁻ pairs. The N _i also lead to mass-squared differences for SM neutrinos in agreement with global oscillation data. We first show that such a model offers a natural joint solution to the MB and LSND excesses, providing excellent fits to their data. Next, using the values of the couplings to the quarks and electrons which are required to explain pair creation nuclear transition data for ⁸Be and ⁴He in ATOMKI, we show that these values still lead to fits for MB and LSND data. However, once ATOMKI is incorporated, we find that strong constraints from the decays K ⁺ → π ⁺ a ^′ (a ^′ → e ⁺ e ⁻) and π ⁺ → e ⁺ ν _e e ⁺ e ⁻ come into play. While our solution is in conformity with the bounds on the former decay, it remains in tension with 90% CL bounds on the latter. We also discuss other constraints from both collider and non-collider experiments and from electroweak precision data, stability and unitarity. We compute the contributions to the electron and muon g – 2 up to two loops for our model. We discuss tests of the model in upcoming experiments.