arXiv subjects

Tanmoy Modak

Publications and source records attributed to Tanmoy Modak.

At least 19 recordsLinked to original sources

arXiv2026

Gravitational Dark Matter Production from Spectator Field in $R^2$-Higgs Inflation

We investigate the cosmological gravitational dark matter production of spectator field $χ$ in the multifield $R^2$-Higgs inflation. The spectator field $χ$ couples to gravity only through a non-minimal coupling $ξ_χχ^2R$ and serves as a dark matter (DM) candidate. Working consistently in the Einstein frame, we derive the equation of motion of the background fields and fluctuations at linear order using the doubly covariant formalism. We show the dark matter production and the subsequent comoving relic abundance heavily depend on this effective mass of the field $χ$. Specifically, we find that there exists cancellation regions in the effective mass-squared of $χ$, which ensures the correct relic abundance is achieved. Further, we show that the preheating from Higgs and Goldstone may play critical role in accounting the observed relic density.

astro-ph.CO↗

arXiv2026

Nonminimal couplings and preheating effects in $R^2$-Higgs inflation after ACT and SPT data

We study the effects of dimension-four and dimension-six nonminimal Higgs couplings to the Ricci scalar $R$ in the $R^2$-Higgs inflation model in light of the recent ACT and SPT observations. We show that the dimension-six operators $|Φ|^2 R^2$ and $|Φ|^4 R$ can accommodate the enhanced scalar spectral index $n_s$ preferred by the combined CMB+BAO analyses. Using a doubly covariant formalism, we find that the same region of parameter space that explains the observed value of $n_s$ can also induce rapid preheating through the production of the Goldstone modes. If thermalization proceeds efficiently through this preheating mechanism, it may help match the inflationary scale with the CMB reference scale.

astro-ph.CO↗

arXiv2026

A Global Overview of Starobinsky Inflation beyond slow-roll with CMB-BAO data

We perform a global analysis of the Starobinsky inflation using most recent CMB data from ACT and SPT together with DESI BAO measurements. By directly solving the equations of motion, we find relatively stronger constraints on the model parameters than those obtained under the slow-roll approximation from the baseline $Λ$CDM parameters $A_s$ and $n_s$. We translate these constraints into limits on the reheating temperature. We also discuss the dependence of the prior choices of the model parameters. Further, the correlation of the model parameters with the BAO parameter $r_d h$ is also studied. We further investigate the impact of the global analysis on the dimension-six $R^3$ modified Starobinsky model, deriving constraints on its additional parameters. Finally, we also provide parameter limits on the effective inflationary Hubble slow-roll (HSR) and potential slow-roll (PSR) parametrization.

astro-ph.CO↗

arXiv2026

Echoes of $R^3$ modification and Goldstone preheating in the CMB-BAO landscape

The $R^2$ and the single-field-like regime of $R^2$-Higgs inflation are disfavored by the observed high spectral index $n_s$ from the combined cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) measurements at the $\sim2σ$ level. The addition of a dimension-six $R^3$ term in the action helps alleviate this tension. We show that the parameter space accounting for the observed high $n_s$ also induces rapid Goldstone and Higgs preheating. The preheating, especially from Goldstone modes, helps match the CMB and inflationary scales, which in turn supports the observed $n_s$.

hep-ph↗

arXiv2025

The $R^2$-Higgs inflation: $R^3$ contribution and preheating after ACT and SPT data

The $R^2$-Higgs inflation is one of the simplest yet best-fit models consistent with Planck data. The higher spectral index $n_s$ recently reported by the combined cosmic microwave background (CMB) data from the Atacama Cosmology Telescope (ACT), South Pole Telescope (SPT), and Planck, along with baryonic acoustic oscillation data from the Dark Energy Spectroscopic Instrument (DESI), disfavors the single-field-like regime of $R^2$-Higgs inflation at approximately $2σ$. Following a doubly covariant formalism, we show that the $R^2$-Higgs inflation, when modified by a dimension-six $R^3$ term, can account for the high $n_s$ reported by CMB+BAO. In this regard, we find that preheating may play a pivotal role. We also show that if the nonminimal coupling between the Ricci scalar $R$ and the Higgs field is $\mathcal{O}(10)$, then preheating via the production of Higgs quanta may help explain the reported observations.

hep-ph↗

arXiv2025

A Global View of the EDM Landscape

Permanent electric dipole moments (EDMs) are sensitive probes of the symmetry structure of elementary particles, which in turn is closely tied to the baryon asymmetry in the universe. A meaningful interpretation framework for EDM measurements has to be based on effective quantum field theory. We interpret the measurements performed to date in terms of a hadronic-scale Lagrangian, using the SFitter global analysis framework. We find that part of this Lagrangian is constrained very well, while some of the parameters suffer from too few high-precision measurements. Theory uncertainties lead to weaker model constraints, but can be controlled within the global analysis.

hep-ph↗

arXiv2025

Semi-visible jets, energy-based models, and self-supervision

We present DarkCLR, a novel framework for detecting semi-visible jets at the LHC. DarkCLR uses a self-supervised contrastive-learning approach to create observables that are approximately invariant under relevant transformations. We use background-enhanced data to create a sensitive representation and evaluate the representations using a CLR-inspired anomaly score and a normalized autoencoder as density estimators. Our results show a remarkable sensitivity for a wide range of semi-visible jets and are more robust than a supervised classifier trained on a specific signal.

hep-ph↗

arXiv2024

Implication of preheating on gravity assisted baryogenesis in $R^2$-Higgs inflation

We investigate the impact of preheating on baryogenesis in $R^2$-Higgs inflation. In this scenario, the inclusion of a dimension-six operator ${(R/ Λ^2)} B_{μν} \widetilde{B}^{μν} $ abundantly generates helical hypermagnetic fields during inflation, leading to a baryon asymmetric Universe at the electroweak crossover. Focusing on the $R^2$-like regime, we first derive the relevant dynamics of preheating using a doubly-covariant formalism. We find that preheating can happen for the Higgs, transverse gauge and Goldstone bosons, however, it is dependent on the value of the non-minimal coupling $ξ_H$ between the Standard Model Higgs field and the Ricci scalar. We identify the preheating temperature to determine the appropriate scale $Λ$ for driving baryogenesis, which is around $Λ\sim 2.2 \, (2.6) \times 10^{-5}\, M_{\rm P}$ for $ξ_H \sim 1 \, (10)$. Our results represent the most accurate estimation of the scale of gravity induced baryogenesis in $R^2$-Higgs inflation to date. Areas for further improvement are identified.

hep-ph↗

arXiv2024

Anomalies, Representations, and Self-Supervision

We develop a self-supervised method for density-based anomaly detection using contrastive learning, and test it using event-level anomaly data from CMS ADC2021. The AnomalyCLR technique is data-driven and uses augmentations of the background data to mimic non-Standard-Model events in a model-agnostic way. It uses a permutation-invariant Transformer Encoder architecture to map the objects measured in a collider event to the representation space, where the data augmentations define a representation space which is sensitive to potential anomalous features. An AutoEncoder trained on background representations then computes anomaly scores for a variety of signals in the representation space. With AnomalyCLR we find significant improvements on performance metrics for all signals when compared to the raw data baseline.

hep-ph↗

arXiv2024

Baryogenesis in $R^2$-Higgs Inflation: the Gravitational Connection

$R^2$-Higgs inflation stands out as one of the best-fit models of Planck data. Using a covariant formalism for the inflationary dynamics and the production of helical gauge fields, we show that the observed baryon asymmetry of the Universe (BAU) can be obtained when this model is supplemented by a dimension-six CP-violating term $\sim (R/Λ^2)\, B_{μν} \widetilde{B}^{μν}$ in the hypercharge sector. At linear order, values of $Λ\simeq 2.5\times10^{-5}\ M_{\rm P}$ produce, in the $R^2$-like regime, sufficient helical hypermagnetic fields to create the observed matter-antimatter asymmetry during the electroweak crossover. However, the Schwinger effect of fermion pair production can play a critical role in this context, and that scale is significantly lowered when the backreaction of the fermion fields on the gauge field production is included. In all cases, the helical field configurations can remain robust against washout after the end of inflation.

astro-ph.CO↗

arXiv2023

Probing Baryogenesis with Radiative Beauty Decay and Electron EDM

With the Large Hadron Collider (LHC) running, we should probe electroweak baryogenesis (EWBG) while probing $CP$ violation (CPV) with electron electric dipole moment (eEDM). Rooted in the flavor structure of the Standard Model (SM), the general two Higgs doublet model (g2HDM) with a second set of Yukawa couplings can deliver EWBG while surviving eEDM. We point out a chiral-enhanced top-bottom interference effect that makes $b \to sγ$ decay an exquisite window on EWBG and eEDM, and illustrate the importance of the $ΔA_{CP}$ observable at Belle II.

hep-ph↗

arXiv2023

Ultraviolet Sensitivity in Higgs-Starobinsky Inflation

The general scalar-tensor theory that includes all the dimension-four terms has parameter regions that can produce successful inflation consistent with cosmological observations. This theory is in fact the same as the Higgs-Starobinsky inflation, when the scalar is identified with the Standard Model Higgs boson. We consider possible dimension-six operators constructed from non-derivative terms of the scalar field and the Ricci scalar as perturbations. We investigate how much suppression is required for these operators to avoid disrupting the successful inflationary predictions. To ensure viable cosmological predictions, the suppression scale for the sixth power of the scalar should be as high as the Planck scale. For the other terms, much smaller scales are sufficient.

hep-ph↗

arXiv2023

Cornering Extended Starobinsky Inflation with CMB and SKA

Starobinsky inflation is an attractive, fundamental model to explain the Planck measurements, and its higher-order extension may allow us to probe quantum gravity effects. We show that future CMB data combined with the 21cm intensity map from SKA will meaningfully probe such an extended Starobinsky model. A combined analysis will provide a precise measurement and intriguing insight into inflationary dynamics, even accounting for correlations with astrophysical parameters.

astro-ph.CO↗

arXiv2022

Implications of the heavy Higgs induced single-top, same-sign top and triple-top productions at the LHC

In this brief review we study the discovery potential of heavy Higgs induced single-top, same-sign top and triple-top quark productions at the Large Hadron Collider (LHC). The context is general two Higgs doublet model where such processes can be induced by additional Yukawa couplings and sub-Tev Higgs bosons. We show that these processes can be discovered at the ongoing or future high luminosity LHC run. Discovery of these multi-top productions may shed light on the mechanism behind baryogenesis or cosmic inflation.

hep-ph↗

arXiv2022

Probing the Inflaton Potential with SKA

SKA will be a major step forward not only in astrophysics, but also in precision cosmology. We show how the neutral hydrogen intensity map can be combined with the Planck measurements of the CMB power spectrum, to provide a precision test of the inflaton potential. For a conservative range of redshifts we find that SKA can significantly improve current constraints on the Hubble slow-roll parameters.

astro-ph.CO↗

arXiv2022

Searching for Charged Higgs Bosons via $e^+ e^- \to H^+ H^- \to c\bar{b} \bar{c}b $ at Linear Colliders

We study a search for the charged Higgs boson via $e^+e^- \to H^+H^- \to c\bar{b}\bar{c}b$ at the 500 GeV ILC. In a general two Higgs doublet model without $Z_2$ symmetry, extra Yukawa couplings $ρ_{tt}$ and $ρ_{tc}$ can drive baryogenesis, but searches at the HL-LHC may still go empty-handed if the couplings are relatively weak. Taking $m_{H^+ } \simeq m_H \simeq m_A \simeq 200$ GeV, with $ρ_{tt}$, $ρ_{tc}\sim 0.1$ and no $h(125)$-$H$ mixing, $H^+ \to c\bar b$ decay is dominant, and the $c\bar{b}\bar{c}b$ final state is likely overwhelmed by QCD background at the LHC. We show that the electroweak production of $H^+ H^-$ at the ILC is discoverable with integrated luminosity of 1 ab$^{-1}$. Furthermore, we show that $m_{H^+}$ can be extracted by requiring the two pairs of $b$ and light jets be roughly equal in mass, without assuming the mass value. Thus, ILC can probe low mass Higgs bosons in multijet final states to complement HL-LHC in the future

hep-ph↗

arXiv2022

The $R^2$-Higgs inflation with two Higgs doublets

We study $R^2$-Higgs inflation in a model with two Higgs doublets in which the Higgs sector of the Standard Model is extended by an additional Higgs doublet, thereby four scalar fields are involved in the inflationary evolutions. We first derive the set of equations required to follow the inflationary dynamics in this two Higgs doublet model, allowing a nonminimal coupling between the Higgs-squared and the Ricci scalar $R$, as well as the $R^2$ term in the covariant formalism. By numerically solving the system of equations, we find that, in parameter space where a successful $R^2$-Higgs inflation are realized and consistent with low energy constraints, the inflationary dynamics can be effectively described by a single slow-roll formalism even though four fields are involved in the model. We also argue that the parameter space favored by $R^2$-Higgs inflation requires nearly degenerate masses for $m_\mathsf{H}$, $m_A$ and $m_{\mathsf{H}^\pm}$, where $\mathsf{H}$, $A$, and $\mathsf{H}^\pm$ are the extra CP even, CP odd, and charged Higgs bosons in the general two Higgs doublet model taking renormalization group evolutions of the parameters into account. Discovery of such heavy scalars at the Large Hadron Collider (LHC) are possible if they are in the sub-TeV mass range. Indirect evidences may also emerge at the LHCb and Belle-II experiments, however, to probe the quasi degenerate mass spectra one would likely require high luminosity LHC or future lepton colliders such as the International Linear Collider and the Future Circular Collider.

hep-ph↗

arXiv2021

Collider Prospects for Muon $g-2$ in General Two Higgs Doublet Model

Recent progress on muon $g-2$ measurement prompts one to take it even more seriously. In the general two Higgs doublet model that allows extra Yukawa couplings, we take a simplified approach of single enhanced coupling. We fix the charged lepton flavor violating coupling, $ρ_{τμ} = ρ_{μτ}$, via the one-loop mechanism, for illustrative masses of the heavy scalar $H$ and pseudoscalar $A$, where we assume $m_A = m_{H^+}$. Since extra top Yukawa couplings are plausibly the largest, we turn on $ρ_{tt}$ and find that LHC search for $gg \to H,\,A \to τμ$ gives more stringent bound than from $τ\to μγ$ with two-loop mechanism. Turning on a second extra top Yukawa coupling, $ρ_{tc}$, can loosen the bound on $ρ_{tt}$, but LHC constraints can again be more stringent than from $B \to Dμν$ vs $Deν$ universality. This means that evidence for $H,\,A \to τμ$ may yet emerge with full LHC Run 2 data, while direct search for $τ^\pmμ^\mp bW^+$ or $t\bar cbW^+$ (plus conjugate) may also bear fruit.

hep-ph↗