Surender Verma
@cuhimachal.ac.in
Associate Professor, Department of Physics and Astronomical Science
Central University Himachal Pradesh
EDUCATION
Ph. D.
RESEARCH INTERESTS
• Neutrino Mass Model Building and their low
energy phenomenology
• Dark Matter and its Collider Complementarity
• CP Violation in Leptonic sector and Leptogenesis
• Grand Unified Theories (GUTs)
• Aspects of Modular symmetries and canonical
seesaw models
Scopus Publications
Scopus Publications
Labh Singh, Devabrat Mahanta, and Surender Verma
IOP Publishing
Abstract The scotogenic model presents an elegant and succinct framework for elucidating the origin of tiny neutrino masses within the framework of the Standard Model, employing radiative corrections within the domain of the dark sector. We investigate the possibility of achieving low-scale leptogenesis in the singlet-triplet scotogenic model (STSM), where dark matter mediates neutrino mass generation. We initially considered a scenario involving two moderately hierarchical heavy fermions, N and Σ, wherein the lepton asymmetry is generated by the out-of-equilibrium decay of both particles. Our analysis indicates that the scale of leptogenesis in this scenario is similar to that of standard thermal leptogenesis and is approximately M N,Σ ∼ 109 GeV, which is comparable to the Type-I seesaw case. Further, we consider the case with three heavy fermions (N 2, N 2, and Σ) with the hierarchy M N 1 < M Σ ≪ MM N 2 , which yields the lower bound on heavy fermions up to 3.1 TeV, therefore significantly reduce the scale of the leptogenesis up to TeV scale. The only prerequisite is suppression in the N 1 and Σ Yukawa couplings, which causes suppressed washout effects and a small active neutrino mass of about 10-5 eV. This brings about the fascinating insight that experiments aiming to measure the absolute neutrino mass scale can test low-scale leptogenesis in the scotogenic model. Further, the hyperchargeless scalar triplet Ω provides an additional contribution to mass of the W-boson explaining CDF-II result.
Tapender, Sanjeev Kumar, and Surender Verma
American Physical Society (APS)
We investigate the consequences of generalized CP (GCP) symmetry within the context of the two Higgs doublet model (2HDM), specifically focusing on the lepton sector. Utilizing the Type-I seesaw framework, we study an intriguing connection between the Dirac Yukawa couplings originating from both Higgs fields, leading to a reduction in the number of independent Yukawa couplings and simplifying the scalar and Yukawa sectors when compared to the general 2HDM. The CP3 constraint results in two right-handed neutrinos having equal masses and leads to a diagonal right-handed Majorana neutrino mass matrix. Notably, CP symmetry experiences a soft break due to the phase associated with the vacuum expectation value of the second Higgs doublet. The model aligns well with observed charged lepton masses and neutrino oscillation data, explaining both masses and mixing angles, and yields distinct predictions for normal and inverted neutrino mass hierarchies. It features a novel interplay between atmospheric mixing angle $\\theta_{23}$ and neutrino mass hierarchy: the angle $\\theta_{23}$ is below maximal for the normal hierarchy and above maximal for inverted hierarchy. Another interesting feature of the model is inherent CP violation for the inverted hierarchy.
Monal Kashav and Surender Verma
Springer Science and Business Media LLC
S. Verma and A. Kumar
Pleiades Publishing Ltd
Monal Kashav and Surender Verma
IOP Publishing
Abstract The topological classification of one-loop Weinberg operator at dimension-5 leads to systematic categorization of one-loop neutrino mass models. All one-loop neutrino mass models must fall in one of these categories. Among these topological categories, loop extension of canonical seesaw scenarios is interesting in light of the current LHC run. Apart from one-loop contribution, these extensions result in dominant tree-level contribution to neutrino masses. The immediate remedy to obtain dominant one-loop contribution requires combination of flavor symmetries and enlarged field content. Alternatively, in this work, we propose a minimal way of realizing the topological structures with dominant one-loop contribution using modular variant of the permutation symmetries. In such a realization, no new fields are needed apart from those permitted by the topology itself. For the first time, we have realized one such topological Lorentz structure(T4-2-i) pertaining to one-loop extension of Type-II seesaw using modular A4 symmetry. Here, modular weights play an important role in suppressing tree-level terms and stabilizing the particles running in the loop(Ni , ρ and ϕ), thus, making them suitable dark matter candidates. In this work, we have explored the possibility of fermionic dark matter candidate where right-handed neutrino (N 1) is assumed to be lightest. We have, also, analyzed the compatibility of the model with neutrino oscillation data and obtained model predictions for effective Majorana mass Mee and CP violation. Furthermore, the predictions on relic density of dark matter and its direct detection considering bound on lepton flavor violating process, μ → eγ have, also, been investigated.
Simran Arora, Monal Kashav, Surender Verma, and B C Chauhan
IOP Publishing
Abstract The latest results of anomalous muon magnetic moment at Fermilab show a discrepancy of 4.2 σ between the Standard Model (SM) prediction and experimental value. In this work, we revisit U ( 1 ) L μ − L τ symmetry with in the paradigm of scotogenic model which explains muon (g − 2) and neutrino mass generation, simultaneously. The mass of new gauge boson M Z μ τ generated after the spontaneous symmetry breaking of U ( 1 ) L μ − L τ is constrained, solely, in light of the current neutrino oscillation data to explain muon (g − 2). In particular, we have obtained two regions I and II, around 150 MeV and 500 MeV, respectively, in M Z μ τ − g μ τ plane which explain the neutrino phenomenology. Region I is found to be consistent with muon neutrino trident (MNT) bound (g μ τ ≤ 10−3) to explain muon (g − 2), however, region II violates it for mass range M Z μ τ > 300 MeV . We, then, extend the minimal gauged scotogenic model by a vector like lepton (VLL) triplet ψ T . The mixing of ψ T with inert scalar doublet η leads to chirally enhanced positive contribution to muon anomalous magnetic moment independent of Z μ τ mass. Furthermore, we have, also, investigated the implication of the model for 0ν β β decay and CP violation. The non-observation of 0ν β β decay down to the sensitivity of 0.01 eV shall refute the model. The model, in general, is found to be consistent with both CP conserving and CP violating solutions.
Labh Singh, Tapender, Monal Kashav, and Surender Verma
IOP Publishing
Abstract The trimaximal mixing scheme results in “magic” neutrino mass matrix which is known to accommodate neutrino oscillation data. In this paper, we propose a phenomenological ansatz for by extending the magic symmetry that leads to further reduction in the number of free parameters, thereby increasing the predictability of the model. The neutrino mixing parameters, effective Majorana mass m ee and CP invariants (J CP , I 1, I 2) are found to exhibit strong correlations for mixing paradigm. One of the generic feature of the model is the requirement of non-maximal for possible CP violation measurable in neutrino oscillation experiments. The observables m ee and sum of neutrino masses have imperative implications for yet unknown neutrino mass hierarchy. For inverted hierarchy, the lower bound on , predicted by the model, is found to be within the sensitivity reach of the decay experiments. Also, cosmological bound of 0.12 eV on , at 95% CL, refutes inverted hierarchy implying with normal hierarchy as the only viable possibility in the model. We have, also, illustrated a scenario wherein such a construction of the neutrino mass matrix can be realized using symmetry in the framework of Type-I+II seesaw mechanism.
Simran Arora, Monal Kashav, Surender Verma, and B C Chauhan
Oxford University Press (OUP)
Abstract The latest results of the CDF-II Collaboration show a discrepancy of 7σ with standard model expectations. There is also a 4.2σ discrepancy in the measurement of the muon magnetic moment reported by Fermilab. We study the connection between neutrino masses, dark matter, the Muon (g − 2) experiment, and the W-boson mass anomaly within a single coherent framework based on a Z4 extension of the scotogenic model with a vector-like lepton (VLL). Neutrino masses are generated at the one-loop level. The inert doublet also provides a solution to the W-boson mass anomaly through correction in oblique parameters S, T, and U. The coupling of the VLL triplet ψT to the inert doublet η provides a positive contribution to the muon anomalous magnetic moment. In the model, the VLL triplet provides a lepton portal to dark matter, $\\eta _R^0$. The model predicts a lower bound mee &gt; 0.025 eV at 3σ, which is well within the sensitivity reach of the 0νββ decay experiments. The model explains the muon anomalous magnetic moment Δaμ for 1.3 &lt; yψ &lt; 2.8 and a DM candidate mass in the range $152\\text{ GeV}\\lt M_{\\eta _{R}^{0}}\\lt 195\\text{ GeV}$. The explanation of the W-boson mass anomaly further constrains the mass of the DM candidate, $M_{\\eta _{R}^{0}}$, in the range $154\\text{ GeV}\\lt M_{\\eta _{R}^{0}}\\lt 174\\text{ GeV}$.
Labh Singh, Monal Kashav, and Surender Verma
World Scientific Pub Co Pte Ltd
In the framework of anomaly free [Formula: see text] model, singlet scalar field with nonzero [Formula: see text] charge gives rise to massive gauge boson [Formula: see text] through spontaneous symmetry breaking. [Formula: see text] leads to one loop contribution to the muon anomalous magnetic moment. These scalar fields may, also, appear in the structure of right-handed neutrino mass matrix, thus, connecting the possible explanation of muon [Formula: see text] and low-energy neutrino phenomenology through vevs associated with the scalar fields. In this work, we consider textures of inverse neutrino mass matrix [Formula: see text] wherein any two elements of the mass matrix are zero. In this ansatz, with Dirac neutrino mass matrix diagonal, the zero(s) of right-handed Majorana neutrino mass matrix correspond to zero(s) in the low-energy effective neutrino mass matrix (within Type-I seesaw). We have realized two such textures of [Formula: see text] accommodating the muon [Formula: see text] and low-energy neutrino phenomenology. The requirement of successful explanation of muon [Formula: see text], further, constrains the allowed parameter space of the model and results in sharp correlations amongst neutrino mixing angles and CP invariants. The model explains muon [Formula: see text] for [Formula: see text] in the range (0.035–0.100 GeV) and [Formula: see text] which is found to be consistent with constraints coming from the current experiments CCFR, COHERENT, BABAR while being within sensitivities of future experiments such as NA62 and NA64.
Labh Singh, Monal Kashav, and Surender Verma
Springer Science and Business Media LLC
AbstractIn this work we have investigated the phenomenological consequences of two-zero textures of inverse neutrino mass matrix ($$M_{\\nu }^{-1}$$ M ν - 1 ) in light of the large mixing angle (LMA) and large mixing angle-dark (LMA-D) solutions, later of which originates if neutrinos exhibit non-standard interactions with matter. Out of fifteen possibilities, only seven two-zero textures of $$M_{\\nu }^{-1}$$ M ν - 1 are found to be phenomenologically allowed under LMA and/or LMA-D descriptions. In particular, five textures are in consonance with both LMA and LMA-D solutions and are necessarily CP violating while remaining two textures are found to be consistent with LMA solution only. The textures with vanishing (1, 1) element of $$M_{\\nu }^{-1}$$ M ν - 1 are, in general, disallowed. All the textures allowed under LMA and LMA-D solutions follow the same neutrino mass hierarchy. Furthermore, textures with vanishing (2, 3) element of $$M_{\\nu }^{-1}$$ M ν - 1 are found to be either disallowed or are consistent with LMA description only. We have, also, obtained the implication of the model for $$0\\nu \\beta \\beta $$ 0 ν β β decay amplitude $$|M_{ee}|$$ | M ee | . For most of the textures the calculated $$3\\sigma $$ 3 σ lower bound on $$|M_{ee}|$$ | M ee | is $$\\mathcal {O}(10^{-2})$$ O ( 10 - 2 ) , which is within the sensitivity reach of $$0\\nu \\beta \\beta $$ 0 ν β β decay experiments. We have, also, proposed a flavor model based on discrete non-Abelian flavor group $$A_4$$ A 4 wherein such textures of $$M_{\\nu }^{-1}$$ M ν - 1 can be realized within Type-I seesaw setting.
Ankush, Monal Kashav, Surender Verma, and B.C. Chauhan
Elsevier BV
Rishu Verma, Monal Kashav, Surender Verma, and B C Chauhan
Oxford University Press (OUP)
Abstract In this paper, we present a model based on A4 discrete flavor symmetry implementing inverse and type-II seesaw mechanisms to have LHC-accessible TeV-scale right-handed neutrino mass and texture one-zero in the resulting Majorana neutrino mass matrix, respectively. We investigate the neutrino and dark matter sectors of the model. Non-Abelian discrete A4 symmetry spontaneously breaks into the Z2 subgroup and hence provides a stable dark matter candidate. To constrain the Yukawa Lagrangian of our model, we impose $Z^{\\prime }_2$, Z3, and Z4 cyclic symmetries in addition to the A4 flavor symmetry. In this work we use the recently updated data on cosmological parameters from the Planck Collaboration [N. Aghanim et al. [Planck Collaboration], Astron. Astrophys. A6, 641 (2020)]. For the dark matter candidate mass around 45–55 GeV, we obtain a mediator particle mass (right-handed neutrinos) ranging from 138–155 GeV. The Yukawa couplings are found to be in the range 0.995–1 to have observed the relic abundance of dark matter. We further obtain inverse ($X\\equiv \\frac{F^2n}{z^2}$) and type-II ($X^{\\prime}\\equiv f_1 v_{\\Delta _{1}}$) seesaw contributions to the 0νββ decay amplitude |Mee|, with the model being consistent with low-energy experimental constraints. In particular, we emphasize that the type-II seesaw contribution to |Mee| is large compared to the inverse seesaw contribution for normally ordered (NO) neutrino masses.
Monal Kashav and Surender Verma
Springer Science and Business Media LLC
Abstract In this work, we have proposed a modular A4 symmetric model of neutrino mass which, simultaneously, explains observed baryon asymmetry of the Universe (BAU). In minimal extension of the standard model (SM) with two right-handed neutrinos we work in a supersymmetric framework. At Type-I seesaw level, the model predicts scaling in the neutrino mass matrix. In order to have correct low energy phenomenology, we propose two possible scenarios of scale-breaking in the neutrino mass matrix emanating from Type-I seesaw. Scenario-1 is based on the dimension-5 Weinberg operator whereas scenario-2 implements Type-II seesaw via scalar triplet Higgs superfields (∆,$$ \\overline{\\Delta } $$ ∆ ¯ ). Interestingly, the breaking patterns in both, otherwise dynamically different scenarios, are similar which can be attributed to the same charge assignments of superfields (∆,$$ \\overline{\\Delta } $$ ∆ ¯ ) and the Higgs superfield Hu under modular A4 symmetry. The breaking is found to be proportional to the Yukawa coupling of modular weight 10 ($$ {Y}_{1,1\\prime}^{10} $$ Y 1 , 1 ′ 10 ). We, further, investigates the predictions of the model under scenario-2 (Type-I+II) for neutrino mass, mixings and matter-antimatter asymmetry of the Universe. The model predicts normal hierarchical neutrino masses and provide a robust range (0.05 − 0.08)eV for sum of neutrino masses (Σmi). Lepton number violating 0νββ decay amplitude (Mee) is obtained to lie in the range (0.04 − 0.06)eV. Future 0νββ decay experiments such as NEXT and nEXO shall pose crucial test for the model. Both CP conserving and CP violating solutions are allowed in the model. Interesting correlations are obtained, specially, between Yukawa couplings of modular weight 2 and complex modulus τ. Contrary to $$ {Y}_2^2 $$ Y 2 2 and $$ {Y}_3^2 $$ Y 3 2 , the Yukawa coupling $$ {Y}_1^2 $$ Y 1 2 is found to be insensitive to τ and thus to CP violation because complex modulus τ is the only source of CP violation in the model. We, also, investigate the prediction of the model for BAU. The model exhibit consistent explanation of BAU for right-handed Majorana neutrino mass scale in the range ((1 − 5) × 1013) GeV.
Surender Verma, Shankita Bhardwaj, and Monal Kashav
Springer Nature Singapore
Surender Verma and Shankita Bhardwaj
Springer Nature Singapore
Gazal Sharma, B. C. Chauhan, and Surender Verma
Springer Nature Singapore
Surender Verma and Monal Kashav
IOP Publishing
We investigate baryogenesis via leptogenesis in $A_4$ flavor model within the paradigm of type-I and II seesaw mechanism resulting in magic neutrino mass matrix with broken $\\mu-\\tau$ symmetry in a minimal scenario with two right-handed neutrinos(2RHN). Additional $Z_3$ cyclic symmetry is employed to constrain the Yukawa structure of model. The type-II seesaw terms play crucial role in generating non-degenerate neutrino masses and non-zero $\\theta_{13}$ and contribute in baryogenesis. In particular, after the spontaneous symmetry breaking, the Yukawa couplings $y_{\\Delta_1}$ and $y_{\\Delta_3}$ are responsible for the breaking of $\\mu-\\tau$ symmetry. The effective Majorana neutrino mass $|M_{ee}|$ is found to be well within the sensitivity reach of the $0\\nu\\beta\\beta$ experiments, in particular, for inverted hierarchy. The model has imperative implication for inverted hierarchy, for example, the non-observation of this process at nEXO will rule out IH. The predicted baryon asymmetry is in good agreement with the observed baryon asymmetry for NH whereas IH is disallowed at 2.5$\\sigma$ C.L..
Surender Verma and Monal Kashav
World Scientific Pub Co Pte Lt
We have investigated the phenomenological implications of texture one-zero neutrino mass matrix under the lamp post of the latest data on neutrino mass and mixings. In particular, we have obtained the predictions of the model for, yet unknown observables like neutrino mass hierarchy, [Formula: see text]-octant and CP violation. Out of the six texture one-zero neutrino mass models, [Formula: see text], [Formula: see text] and [Formula: see text] are found to be necessarily CP violating. [Formula: see text] can be above or below maximality except for the texture [Formula: see text] (with NH), wherein [Formula: see text] at [Formula: see text]. Also, we have proposed a flavor model based on the non-Abelian group [Formula: see text] within the paradigm of type-I+II seesaw framework, wherein such textures can be realized.
Surender Verma, Monal Kashav, and Shankita Bhardwaj
Elsevier BV
Surender Verma and Shankita Bhardwaj
Hindawi Limited
The future long baseline experiments such as DUNE and T2HKK have promising prospects to determine the neutrino mass hierarchy and measuring standard CP phase δ. However, presence of possible nonstandard interactions of neutrinos with matter may intricate this picture and is the subject matter of the present work. We have studied the standard parameter degeneracies in presence of nonstandard interactions (NSI) with DUNE and T2HKK experiments. We examine the mass hierarchy degeneracy assuming (i) all NSI parameters to be nonzero and (ii) one NSI parameter (ϵeμ) and its corresponding CP phase (δeμ) to be nonzero. We find that the latter case is more appropriate to resolve mass hierarchy degeneracy with DUNE and T2HKK experiments due to relatively small uncertainties emanating from the NSI sector. We have, also, investigated the octant degeneracy with neutrino (νμ→νe) and antineutrino (ν¯μ→ν¯e) mode separately. We find that to resolve this degeneracy the long baseline experiment with combination of neutrino and antineutrino mode is essential. Furthermore, we have considered DUNE in conjunction with T2HKK experiment to study CP phase degeneracy due to standard (δ) and nonstandard (δeμ) CP phases. We find that DUNE and T2HKK, in conjunction, have more sensitivity for CP violation effects (10σ for true NH and 8.2σ for true IH).
Surender Verma and Shankita Bhardwaj
Springer Science and Business Media LLC
Surender Verma and Shankita Bhardwaj
American Physical Society (APS)
We have investigated a possible connection between the Majorana phases and geometric parameters of leptonic unitarity triangle(LUT) in two-texture zero neutrino mass matrix. Such analytical relations can, also, be obtained for other theoretical models viz. hybrid textures, neutrino mass matrix with vanishing minors and have profound implications for geometric description of $CP$ violation. As an example, we have considered two-texture zero neutrino mass model to obtain relation between Majorana phases and LUT parameters. In particular, we find that Majorana phases depend on only one of the three interior angles of LUT in each class of two-texture zero neutrino mass matrix. We have, also, constructed LUT for class $A$, $B$ and $C$ neutrino mass matrices. Non-vanishing areas and nontrivial orientations of these Majorana unitarity triangles indicate non-zero $CP$ violation as a generic feature of this class of mass models.
Surender Verma, Shankita Bhardwaj, B. C. Chauhan, and Gazal Sharma
Springer International Publishing
Ashish Sharma, Govind Singh, Gazal Sharma, Shankita Bhardwaj, Surender Verma, and B. C. Chauhan
Springer International Publishing
Gazal Sharma, Shankita Bhardwaj, B. C. Chauhan, and Surender Verma
Springer International Publishing