arXiv subjects

Rukmani Mohanta

Publications and source records attributed to Rukmani Mohanta.

At least 55 records · Page 3Linked to original sources

arXiv2023

Unveiling neutrino phenomenology, $(g-2)_{e,μ}$ and leptogenesis through U(1) gauge symmetries in an inverse seesaw model

The proposed work is an extension of the Standard Model, where we have introduced two gauge symmetries, i.e., $U(1)_{B-L}$ and $U(1)_{L_e-L_μ}$ to study neutrino phenomenology, muon, and electron $(g-2)$ as well as leptogenesis using the inverse seesaw mechanism. For this purpose, we have included three right-handed neutrinos $N_{R_i}$, three neutral fermions $S_{L_i} (i =1,2,3)$ and two scalar singlet bosons ($χ_1$ and $χ_2$). We get a definite structure for the neutrino mass matrix due to the aforementioned gauge symmetries. Thus, our model is able to predict the neutrino oscillation results, which are in accordance with the experimental data and is inclined towards normal ordering. The outcomes comprise the active neutrino masses, mixing angles, mass squared differences, CP-violating phase, etc. Moreover, since the extended gauge symmetries are local, there are corresponding gauge bosons, denoted as $Z_{B-L}$ and $Z_{e μ}$. Of these, mass of $Z_{B-L}$ is $\mathcal{O}$(TeV) range to satisfy the collider constraint, while the mass of $Z_{e μ}$ is in the MeV range, making it feasible to account for current electron and muon $(g-2)$ results via neutral current interactions. Furthermore, our model is able to account for leptogenesis, which can demonstrate the matter-antimatter asymmetry of the universe. Additionally, we have carried out the prospect of probing our model in the context of upcoming long baseline experiments: DUNE, T2HK, and T2HKK, at a confidence level of $5σ$. From the result it is clear that, our model can be tested in its $3σ$ C.L. with $5σ$ allowed region of DUNE, T2HK and T2HKK.

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arXiv2023

Neutrino phenomenology, W mass anomaly & muon $(g-2)$ in minimal type-III seesaw using $T^\prime$ modular symmetry

In this study, we attempt to introduce a model to illustrate neutrino phenomenology by incorporating two right-handed fermion triplet superfields, i.e., $Σ_{R_j}$, in the presence of the modular symmetry $Γ_3^\prime \simeq A_4^\prime$, a double cover of the $A_4$ modular symmetry. The motivation in utilizing double cover is, so far only even modular forms were considered for constructing modular invariant models, but, in this case, it is possible to extend the modular invariance approach to general integral weight modular forms, i.e., the odd weight modular forms. Hence, this type of amalgamation between $T^\prime$ modular symmetry and minimally extending the seesaw can correctly explain the neutrino phenomenology. Additionally, we have made an attempt to accommodate the most recent measurement of the $W$ boson mass, published by the CDF-II collaboration and shed some light on the recent results of muon $(g-2)$. Finally, we have discussed lepton flavor violation in order to establish a constraint on the mass of right-handed fermion.

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arXiv2023

Distinguishing Non-Standard Interaction and Lorentz Invariance Violation at Protvino to Super-ORCA experiment

As the two phenomena, non-standard interaction (NSI) in neutrino propagation and Lorentz invariance violation (LIV) modify the Hamiltonian of neutrino oscillation in a similar fashion, it is very difficult to distinguish these two effects. The only difference between them lies in the fact that NSI depends on the matter density, whereas LIV is independent of the earth matter effect. Therefore for a fixed baseline experiment, where matter density is constant, the theories describing NSI and LIV are exactly equivalent. However, as the present and future bounds of the NSI and LIV parameters are not equivalent, one can distinguish these two scenarios in the long-baseline neutrino experiments depending on their statistics with respect to the present and future bounds of these parameters. In this paper, we attempt to differentiate between LIV and NSI in the context of DUNE and P2SO, as these two future experiments are believed to be sensitive to the strongest matter effect and will have very large statistics. Taking LIV in the data and NSI in theory, our results show that, indeed it is possible to have good discrimination between LIV and NSI. The best separation between LIV and NSI at $3 σ$ C.L. is achieved for the parameter $a_{μμ}$ with P2SO. In this case, the value of LIV parameter for which separation is possible, lies within its future bound, if one considers the value of NSI parameter to be constrained by the present experiments. Between DUNE and P2SO, the latter has better sensitivity for such discrimination.

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arXiv2023

Study of light sterile neutrino at the long-baseline experiment options at KM3NeT

In this paper, we study the capability of different long-baseline experiment options at the KM3NeT facility i.e., P2O, Upgraded P2O and P2SO to probe the light sterile neutrino and compare their sensitivities with DUNE. The P2O option will have neutrinos from a 90 KW beam at Protvino to be detected at the ORCA detector, the Upgraded P2O will have neutrinos from the upgraded 450 KW beam to be detected at the ORCA detector and the option P2SO will have neutrinos from a 450 KW beam to be detected at the upgraded Super-ORCA detector. All these options will have a baseline around 2595 km. Our results show that the experiments at the KM3NeT (DUNE) would be more sensitive if the value of $Δm^2_{41}$ is around 10 (1) eV$^2$. Our results also show that the role of near detector is very important for the study of sterile neutrinos and addition of near detector improves the sensitivity as compared to only far detector for 3+1 scenario. Among the three options at KM3NeT, the sensitivity of P2O and upgraded P2O is limited and sensitivity of P2SO is either comparable or better than DUNE.

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arXiv2022

Type III seesaw under $A_4$ modular symmetry with leptogenesis

We make an attempt to study neutrino phenomenology in the framework of type-III seesaw by considering $A_4$ modular symmetry in the super-symmetric context. In addition, we have included a local $U(1)_{B-L}$ symmetry which eventually helps us to avoid certain unwanted terms in the superpotential. Hitherto, the seesaw being type-III, it involves three fermion triplet superfields $Σ_R$, along with which, we have included a singlet weighton field $(ρ)$. In here, modular symmetry plays a crucial role by avoiding the usage of excess flavon (weighton) fields. Also, the Yukawa couplings acquire modular forms which are expressed in terms of Dedekind eta function $η(τ)$. However, for numerical analysis we use $q$ expansion expressions of these couplings. Therefore, the model discussed here is triumphant enough to accommodate the observed neutrino oscillation data and also successfully explains observed baryon asymmetry of the universe through leptogenesis.

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arXiv2022

Flavour anomalies and dark matter assisted unification in $SO(10)$ GUT

With the recent experimental hint of new physics from flavor physics anomalies, combined with the evidence from neutrino mass and dark matter, we consider a minimal extension of SM with a scalar leptoquark and a fermion triplet. The scalar leptoquark with couplings to leptons and quarks can explain lepton flavor non-universality observables $R_K$, $R_{K^{(*)}}$, $R_{D^{(*)}}$ and $R_{J/ψ}$. Neutral component of fermion triplet provides current abundance of dark matter in the Universe. The interesting feature of the proposal is that the minimal addition of these phenomenologically rich particles (scalar leptoquark and fermion triplet) assist in realizing the unification of the gauge couplings associated with the strong and electroweak forces of standard model when embedded in the non-supersymmetric $SO(10)$ grand unified theory. We discuss on unification mass scale and the corresponding proton decay constraints while taking into account the GUT threshold corrections.

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arXiv2022

Vector leptoquark $U_3$ and CP violation at T2K, NOvA experiments

In the current epoch of neutrino physics, many experiments are aiming for precision measurements of oscillation parameters. Thus, various new physics scenarios which alter the neutrino oscillation probabilities in matter deserve careful investigation. In this context, we study the effect of a vector leptoquark which induces non-standard neutrino interactions (NSI) that modify the oscillation probabilities of neutrinos in matter. We show that such interactions provide a relatively large value of NSI parameter $\varepsilon_{e μ}$. Considering this NSI parameter, we successfully explain the recent discrepancy between the observed $δ_{CP}$ results of T2K and NOvA.

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arXiv2022

Extracting the best physics sensitivity from T2HKK: A study on optimal detector volume

T2HK is an upcoming long-baseline experiment in Japan which will have two water Cherenkov detector tanks of 187 kt volume each at distance of 295 km from the source. An alternative project, T2HKK is also under consideration where one of the water tanks will be moved to Korea at a distance of 1100 km. The flux at 295 km will cover the first oscillation maximum and the flux at 1100 km will mainly cover the second oscillation maximum. As physics sensitivity at the dual baseline rely on variation in statistics, dependence of systematic uncertainty, effect of second oscillation maximum and matter density, 187 kt detector volume at 295 km and 187 kt detector volume at 1100 km may not be the optimal configuration of T2HKK. Therefore, we have tried to optimize the ratio of the detector volume at both the locations by studying the interplay between the above mentioned parameters. For the analysis of neutrino mass hierarchy, octant of $θ_{23}$ and CP precision, we have considered two values of $δ_{\rm{CP}}$ as 270$^\circ$ and $0^\circ$ and for CP violation we have considered the value of $δ_{\rm CP}= 270^\circ$. These values are motivated by the current best-fit values of this parameter as obtained from the experiments T2K and NO$ν$A. Interestingly we find that if the systematic uncertainty is negligible then the T2HK setup i.e., when both the detector tanks are placed at 295 km gives the best results in terms of hierarchy sensitivity at $δ_{\rm CP}= 270^\circ$, octant sensitivity, CP violation sensitivity and CP precision sensitivity at $δ_{\rm CP}= 0^\circ$. For current values of systematic errors, we find that neither T2HK, nor T2HKK setup is giving better results for hierarchy, CP violation and CP precision sensitivity. The optimal detector volume which is of the range between 255 kt to 345 kt at 1100 km gives better results in those above mentioned parameters.

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arXiv2022

Optimal configuration of Protvino to ORCA experiment for hierarchy and non-standard interactions

In this paper, we study the hierarchy sensitivity of Protvino to ORCA (P2O) experiment in three flavour scenario as well as its sensitivity to non-standard interactions (NSI) in neutrino propagation. Because of the largest possible baseline length of 2595 km, P2O is expected to have strong sensitivity towards neutrino mass hierarchy and NSI parameters. In our study, we show that even though the number of appearance channel events for the minimal configuration of P2O are higher compared to DUNE, still the hierarchy sensitivity of P2O is less than DUNE because of large background events. Our results show that for a background reduction factor of 0.46 and appearance channel background systematic normalization error of $4\%$, the hierarchy sensitivity of P2O becomes equivalent of DUNE for $δ_{\rm CP} = 195^\circ$. We call this configuration of P2O as optimized P2O. Regarding the study of NSI, we find that, for $ε_{eμ}$ ($ε_{eτ}$) sensitivity of DUNE is similar (better) as compared to optimized P2O when both $ε_{eμ}$ and $ε_{eτ}$ are included in the analysis. Our results show that in presence of NSI, the change of hierarchy sensitivity with respect to standard three flavor scenario, is higher in P2O as compared to DUNE. Further, hierarchy sensitivity in presence of NSI is lower (higher) than sensitivity in the standard three flavour scenario for $δ_{\rm CP} = 270^\circ (90^\circ)$. It is important to note that hierarchy sensitivity of optimized P2O does not get significantly better than DUNE for the current favourable values of $δ_{\rm CP}$ which is $180^\circ < δ_{\rm CP} < 360^\circ$ as obtained by the global analysis in both standard three flavour and in presence of NSI.

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arXiv2022

Implications of $A_4$ modular symmetry on Neutrino mass, Mixing and Leptogenesis with Linear Seesaw

The present work is inspired by the application of $A_4$ modular symmetry in the linear seesaw framework, which restricts the use of multiple flavon fields. Linear seesaw is realized with six heavy $SU(2)_L$ singlet fermion superfields and a weighton in a supersymmetric framework. The non-trivial transformation of Yukawa couplings under the $A_4$ modular symmetry helps to explore the neutrino phenomenology with a specific flavor structure of the mass matrix. We discuss the phenomena of neutrino mixing and show that the obtained mixing angles and CP violating phase in this framework are compatible with the observed $3σ$ range of the current oscillation data. In addition, we also investigate the non-zero CP asymmetry from the decay of lightest heavy fermion superfield to explain the preferred phenomena of baryogenesis through leptogenesis including flavor effects.

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arXiv2022

Linear seesaw in $A^\prime_5$ modular symmetry with Leptogenesis

In this paper, we investigate the implication of modular $Γ^{\prime}_5 \simeq A^{\prime}_5$ symmetry on neutrino oscillation phenomenology in the linear seesaw framework. In order to achieve the well defined mass structure for the light active neutrinos as dictated by the linear seesaw mechanism, we introduce six heavy fermion fields along with a pair of weightons to retain the holomorphic nature of the superpotential. The notable feature of modular symmetry is that, it reduces the usage of flavon fields significantly. In addition, the Yukawa couplings transform non-trivially under the flavor symmetry group and expressed in terms of the Dedekind eta functions, the $q$ expansion of which renders numerical simplicity in calculations. We demonstrate that the model framework diligently accommodates all the neutrino oscillation data. Alongside, we also investigate the effect of CP asymmetry generated from the decay of lightest heavy fermions to explain the observed baryon asymmetry through the phenomenon of leptogenesis.

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arXiv2022

Light dark matter, rare $B$ decays with missing energy in $L_μ-L_τ$ model with a scalar leptoquark

We investigate the phenomenology of light GeV-scale fermionic dark matter in $U(1)_{L_μ- L_τ}$ gauge extension of the Standard Model. Heavy neutral fermions alongside with a $S_1(\overline{3}$,$1$,$1/3$) scalar leptoquark and an inert scalar doublet are added to address the flavor anomalies and light neutrino mass respectively. The light gauge boson associated with $U(1)_{L_μ-L_τ}$ gauge group mediates dark to visible sector and helps to obtain the correct relic density. Aided with a colored scalar, we constrain the new model parameters by using the branching ratios of various $b \to sll$ and $b \to s γ$ decay processes as well as the lepton flavour non-universality observables $R_{K^{(*)}}$ and then show the implication on the branching ratios of some rare semileptonic $B \to (K^{(*)}, ϕ)+$ missing energy, processes.

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arXiv2021

Dark matter and flavor anomalies in the light of vector-like fermions and scalar leptoquark

We make a comprehensive study of vector-like fermionic dark matter and flavor anomalies in a simple extension of standard model. The model is added with doublet vector-like fermions of quark and lepton types, and also a $S_1(\bar{\textbf{3}},\textbf{1},1/3)$ scalar leptoquark. An additional lepton type singlet fermion is included, whose admixture with vector-like lepton doublet plays the role of dark matter and is examined in relic density and direct detection perspective. Electroweak precision observables are computed to put constraint on model parameter space. We constrain the new couplings from the branching ratios and angular observables associated with $b \to sll (ν_l \bar ν_l)$, $b \to s γ$ decays and also from the recent measurement on muon anomalous magnetic moment. We then estimate the branching ratios of the rare lepton flavor vioalting $B_{(s)}$ decay modes such as $B_{(s)} \to l_i^\mp l_j^\pm$, $B_{(s)} \to (K^{(*)}, ϕ) l_i^\mp l_j^\pm$.

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arXiv2021

Updated sensitivity of DUNE in 3+1 scenario with far and near detectors

In this paper we present the updated physics sensitivity of DUNE in presence of a light sterile neutrino with both far and near detectors. In the previous studies, the sensitivities were obtained using the configuration of DUNE as described in the conceptual design report (CDR). In this article, we consider the configuration of DUNE as given in the technical design report (TDR) and study the capability of this experiment to constrain the sterile mixing parameters as well as its capability to measure the standard oscillation parameters in 3+1 scenario. Our results show that in 3+1 scenario, the sensitivity of DUNE to measure the mass hierarchy, octant and CP violation deteriorates if we only consider the far detector. However, a combined analysis of far and near detector improves the sensitivity.

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arXiv2021

Exploring the role of new physics in $b \to u τ\bar ν$ decays

The recent measurements on $R_D$, $R_{D^*}$ and $R_{J/ψ}$ by three pioneering experiments, BaBar, Belle and LHCb, indicate that the notion of lepton flavour universality is violated in the weak charged-current processes, mediated through $b \to c \ell \bar ν_\ell$ transitions. These intriguing results, which delineate a tension with their standard model predictions at the level of $(2-3)σ$ have triggered many new physics propositions in recent times, and are generally attributed to the possible implication of new physics in $ b \to c τ\bar ν$ transition. This, in turn, opens up another avenue, i.e., $ b \to u τ\bar ν$ processes, to look for new physics. Since these processes are doubly Cabibbo suppressed, the impact of new physics could be significant enough, leading to sizeable effects in some of the observables. In this work, we investigate in detail the role of new physics in $B \to (π,ρ,ω)τ\bar ν$ and $B_s \to (K,K^*) τ\bar ν$ processes considering a model independent approach. In particular, we focus on the standard observables like branching fraction, lepton flavour non-universality (LNU) parameter, forward-backward asymmetry and polarization asymmetries. We find significant deviations in some of these observables, which can be explored by the currently running experiments LHCb and Belle-II. We also briefly comment on the impact of scalar leptoquark $R_2(3,2,7/6)$ and vector leptoquark $U_1(3,1,2/3)$ on these decay modes.

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arXiv2021

Implications of new physics in $B \to K_1 μ^+ μ^-$ decay processes

In recent times, several discrepancies at the level of $(2-3)σ$ have been observed in the decay processes mediated by flavour changing neutral current (FCNC) transitions $b \to s \ell^+ \ell^-$, which may be considered as the smoking-gun signal of New Physics (NP). These intriguing hints of NP have attracted a lot of attention and many attempts are made to look for the possible NP signature in other related processes, which are mediated through the same quark-level transitions. In this work, we perform a comprehensive analysis of the FCNC decays of $B$ meson to axial vector mesons $ K_1(1270)$ and $ K_1(1400)$, which are admixture of the $1^3P_1$ and $1^1P_1$ states $K_{1A}$ and $K_{1B}$, in a model independent framework. Using the $ B \to K_1$ form factors evaluated in the light cone sum rule approach, we investigate the rare exclusive semileptonic decays $ B \to K_1(1270) μ^+ μ^-$ and $ B \to K_1(1400) μ^+ μ^-$. Considering all the possible relevant operators for $b \to s \ell^+ \ell^-$ transitions, we study their effects on various observables such as branching fractions, lepton flavor universality violating ratio ($R_{K_1})$, forward-backward asymmetries, and lepton polarization asymmetries of these processes. These results will not only enhance the theoretical understanding of the mixing angle but also serve as a good tool for probing New Physics.

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arXiv2021

Inverse seesaw in $A_5^\prime$ modular symmetry

We make an investigation of modular $Γ^{\prime}_5 \simeq A^{\prime}_5$ group in inverse seesaw framework. Modular symmetry is advantageous because it reduces the usage of extra scalar fields significantly. Moreover, the Yukawa couplings are expressed in terms of Dedekind eta functions, which also have a $q$ expansion form, utilized to achieve numerical simplicity. Our proposed model includes six heavy fermion superfields i.e., $\mathcal{N}_{Ri}$, $\mathcal{S}_{Li}$ and a weighton. The study of neutrino phenomenology becomes simplified and effective by the usage of $A^\prime_5$ modular symmetry, which provides us a well defined mass structure for the lepton sector. Here, we observe that all the neutrino oscillation parameters, as well as the effective electron neutrino mass in neutrinoless double beta decay can be accommodated in this model. We also briefly discuss the lepton flavor violating decays $\ell_i \to \ell_j γ$ and comment on non-unitarity of lepton mixing matrix.

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arXiv2021

Constraining CPT violation with Hyper-Kamiokande and ESSnuSB

CPT invariance is one of the most fundamental symmetries in nature and it plays a major role in the formulation of Quantum Field Theory. Although no definitive signal of CPT violation has been observed so far, there are many reasons to carefully investigate various low-energy phenomena that can provide better probes to test CPT symmetry. In this context, neutrino experiments are expected to provide more stringent bounds on CPT invariance violation when compared to the existing bounds from the Kaon system. In this work, we investigate the sensitivity of the upcoming long-baseline experiments: Hyper Kamiokande (T2HK, T2HKK), ESSnuSB and DUNE to constrain the CPT violating parameters $Δ(δ_{CP})$, $Δ(m^2_{31})$ and $Δ(\sin^2 θ_{23})$, which characterize the difference between neutrino and antineutrino oscillation parameters. Further, we analyse neutrino and antineutrino data independently and constrain the oscillation parameters governing them by considering the combination of these experiments (DUNE+T2HKK and DUNE+ESSnuSB). In addition, assuming CPT symmetry is violated in nature, we study the individual ability of the aforementioned experiments to establish CPT violation. We found that the experiments Hyper-K (T2HK, T2HKK) and ESSnuSB, along with DUNE, will be able to establish CPT violation in their proposed run-times.

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