arXiv subjects

Subrata Samanta

Publications and source records attributed to Subrata Samanta.

4 recordsLinked to original sources

arXiv2026

Fate of Metastable Vacua in the Type-II Two-Higgs Doublet Model

The scalar potential of the Two-Higgs-Doublet Model (2HDM) can admit multiple non-degenerate vacua due to the presence of the two Higgs doublets unlike the Standard Model (SM). For a physically viable parameter point, one of these vacua must correspond to the physical electroweak (EW) symmetry breaking vacuum with the vacuum expectation value of about $246$ GeV. Given the complex structure of the scalar potential, the physical EW vacuum may be metastable in nature rather than the global minimum of the potential. In this work, we delineate regions of the parameter space in the Type-II 2HDM accommodating multiple extrema of the scalar potential and analyze, in a gauge-independent manner, the stability of the EW vacuum there at the tree level and beyond. A Bayesian global fit of the Type-II 2HDM, including next-to-leading-order unitarity constraints and the latest experimental measurements, indicates that parameter space regions leading to metastable EW vacua are excluded at both the tree and one-loop levels.

hep-ph↗

arXiv2026

One-loop renormalization and $\boldsymbol{\rho}$ parameter in the Georgi-Machacek model

We study the one-loop renormalization of the Georgi-Machacek model. At one loop, the renormalization of the model is phenomenologically important when triggered by operators that are absent at the tree level due to the global $SU(2)_R$ symmetry. By computing all the tree-level parameters from the standard input parameters $\alpha_e$, $G_\mu$, and $m_Z$, we show the ultraviolet divergent nature of the electroweak $\rho$ parameter when one-loop corrections are incorporated. In this model, four input parameters are required to completely parametrize the electroweak precision observables at one loop. We study the quantitative impact of the model parameters on the one-loop corrections to the $\rho$ parameter. At one loop, the $\rho$ parameter shows a mild dependence on the mass differences between the custodial fiveplet and the heavy custodial singlet, and mainly depends on the ratio of the doublet and triplet vacuum expectation values, and on the mixing angle between the custodial singlet CP-even scalars.

hep-ph↗

arXiv2025

Light Scalars in the Extended Georgi-Machacek Model

We perform global fits of the CP-conserving Georgi-Machacek (GM) and extended Georgi-Machacek (eGM) models, incorporating a light CP-even beyond the Standard Model (BSM) scalar within the mass range of $90$ GeV to $100$ GeV. These fits combine the Higgs signal strengths and direct search limits from ATLAS and CMS at $\sqrt{s} = 8$ and $13$ TeV, $B$-physics observables, and theoretical constraints arising from next-to-leading order (NLO) unitarity and BFB constraints. From the global fit, we show that the LHC diphoton and LEP $b\bar{b}$ excesses around $95$ GeV are well compatible with the $125$ GeV Higgs data. Whereas the CMS ditau excess is incompatible with the $125$ GeV Higgs signal strength data in both the CP-conserving GM and eGM models. We present the results from the combined fit, including the $95$ GeV Higgs signal strength data. In the eGM model, the triplet VEV cannot exceed $12$ GeV for additional BSM scalar masses below $160$ GeV and approximately $20$ GeV for additional BSM scalar masses above $160$ GeV. The masses of additional BSM scalars cannot exceed $600$ GeV. The maximum mass splitting is of around $120$ GeV within the members of each custodial multiplet, and up to $250$ GeV between the members of different multiplets. In the GM model, these constraints become more stringent: the triplet VEV is limited to below $15$ GeV, which tightens to $4$ GeV once the BSM scalar masses are below $160$ GeV. Masses of the quintet $m_5$ and the triplet $m_3$ are restricted to be below $530$ GeV and $320$ GeV, respectively. A mass hierarchy, $m_5 > m_3$, is favoured in the high-mass region, with the mass splitting constrained to be less than $210$ GeV.

hep-ph↗

arXiv2024

Next-to-Leading Order Unitarity Fits in the Extended Georgi-Machacek Model

We compute one-loop corrections to all $2\to2$ bosonic scattering amplitudes in the generalized two-triplet scalar extension of the Standard Model and place next-to-leading order unitarity bounds on the scalar quartic couplings of the Georgi-Machacek (GM) and the extended Georgi-Machacek (eGM) models. Further, we derive the bounded-from-below (BFB) conditions on the scalar quartic couplings demanding the stability of the scalar potential in the field subspaces. We find that, in the GM and eGM models, the BFB conditions with all combinations of three non-zero scalar fields provide a very good approximation of the all field BFB conditions while being computationally more efficient. With these improved theoretical constraints, we present results for the GM and eGM models from global fits to the latest Higgs signal strength measurements at the $13$ TeV Large Hadron Collider. We observe that the global fit disfavors the regions where $\kappa_V > 1.05$, $\kappa_V < 0.95$, and $\kappa_f > 1.05$, $\kappa_f< 0.92$ at a $95.4\%$ probability for both models. We obtain an upper limit on the absolute values of the scalar quartic couplings to be $1.91\:(3.0)$ in the GM (eGM) model. We find that the absolute mass differences between the heavy Higgs bosons are less than $410$ GeV and $520$ GeV in the GM and eGM models, respectively, if their individual masses are restricted to be below $1.1$ TeV.

hep-ph↗