We discuss the analytical expression of the oscillation probabilities at low energy long baseline experiments, such as T2HK and T2HKK in the presence of nonstandard interactions (NSIs). We show that these experiments are advantageous to explore the NSI parameters ($ε_D$, $ε_N$), which were suggested to be nonvanishing to account for the discrepancy between the solar neutrino and KamLAND data. We also show that, when the NSI parameters are small, parameter degeneracy in the CP phase $δ$, $ε_D$ and $ε_N$ can be resolved by combining data of the T2HK and T2HKK experiments.
We investigate the prospects for probing the strength of the possible matter nonstandard neutrino interactions (mNSI) in long baseline neutrino oscillation experiments and the interference of the leptonic CP angle $δ_{CP}$ with the constraining of the mNSI couplings. The interference is found to be strong in the case of the $ν_e \leftrightarrow ν_μ$ and $ν_e \leftrightarrow ν_τ$ transitions but not significant in the other cases. We use SPS and DUNE setups as benchmarks.
New effect in neutrino spin oscillations in transversal matter currents with nonstandard interactions
Department of Physics, Branch of Lomonosov Moscow State University in Sarov（萨罗夫莫斯科国立大学物理系分校）；Department of Theoretical Physics & Department of Particle Physics and Extreme States of Matter, Faculty of Physics, Moscow State University（莫斯科国立大学物理学院理论物理系与粒子物理及极端物质状态系）
We study parameter degeneracies that can occur in long-baseline neutrino appearance experiments due to nonstandard interactions (NSI) in neutrino propagation. For a single off-diagonal NSI parameter, and neutrino and antineutrino measurements at a single L/E, there exists a continuous four-fold degeneracy (related to the mass hierarchy and $θ_{23}$ octant) that renders the mass hierarchy, octant, and CP phase unknowable. Even with a combination of NO$ν$A and T2K data, which in principle can resolve the degeneracy, both NSI and the CP phase remain unconstrained because of experimental uncertain…
Resolving CP Violation by Standard and Nonstandard Interactions and Parameter Degeneracy in Neutrino Oscillations
In neutrino oscillation with non-standard interactions (NSI) the system is enriched with CP violation caused by phases due to NSI in addition to the standard lepton Kobayashi-Maskawa phase δ. In this paper we show that it is possible to disentangle the two CP violating effects by measurement of muon neutrino appearance by a near-far two detector setting in neutrino factory experiments. Prior to the quantitative analysis we investigate in detail the various features of the neutrino oscillations with NSI, but under the assumption that only one of the NSI elements, ε_{e μ} or ε_{e τ}, is present.…
We discuss lepton number violating processes in the context of long-baseline neutrino oscillations. We summarise and compare neutrino flavour oscillations in quantum mechanics and quantum field theory, both for standard oscillations and for those that violate lepton number. When the active neutrinos are Majorana in nature, the required helicity reversal gives a strong suppression by the neutrino mass over the energy, $(m_ν/E_ν)^{2}$. Instead, the presence of non-standard lepton number violating interactions incorporating right-handed lepton currents at production or detection alleviate the mas…
Measurements of the solar neutrino mass-squared difference from KamLAND and solar neutrino data are somewhat discrepant, perhaps due to nonstandard neutrino interactions in matter. We show that the zenith angle distribution of solar neutrinos at Hyper-Kamiokande and the energy spectrum of reactor antineutrinos at JUNO can conclusively confirm the discrepancy and detect new neutrino interactions.
We study the effect of non-standard interactions (NSIs) on the propagation of neutrinos through the Earth matter and how it affects the hierarchy sensitivity of the DUNE experiment. We emphasize on the special case when the diagonal NSI parameter $ε_{ee} = -1$, nullifying the standard matter effect. We show that, if in addition, CP violation is maximal then this gives rise to an exact intrinsic hierarchy degeneracy in the appearance channel, irrespective of the baseline and energy. Introduction of off-diagonal NSI parameter, $ε_{e τ}$, shifts the position of this degeneracy to a different $ε_{…
In this work we present a scenario in which a nonstandard interaction in neutrino propagation can explain the three major tensions in the neutrino oscillation data at present. These tensions are: (i) a non-zero best-fit value of the non-standard oscillation parameters in the the global analysis of the solar and KamLAND data which rules out the standard oscillation scenario at $90\%$ C.L, (ii) the measurement of the non-maximal value of $θ_{23}$ by NO$ν$A which excludes the maximal mixing at $2.5 σ$ C.L. and (iii) a discrepancy in the $θ_{13}$ measurement by T2K which has a tension with the rea…
CP violating signal at DUNE in presence of nonstandard interactions and the role of second oscillation maxima
Indian Institute of Technology Bhilai（印度理工学院比莱分校）；Shree Ram College（Shree Ram学院）；Institute of Physics, Bhubaneswar（布巴内斯瓦尔物理研究所）；Jawaharlal Nehru University（贾瓦哈拉尔·尼赫鲁大学）
We derive the effective Hamiltonian describing collective oscillations of Majorana neutrinos with a transition magnetic moment, allowing for the presence of scalar and pseudoscalar nonstandard neutrino self-interactions (NSSIs). Using this Hamiltonian, we analyze new flavor instability channels of collective oscillations in a core-collapse supernova environment that open up in the presence of a small but nonzero neutrino magnetic moment. It turns out that, contrary to certain claims in the literature, within the minimally extended Standard Model (i.e., without NSSIs), no new instabilities aris…
Neutrino flavour oscillation is one of the primary indication of the existence of new physics beyond standard model. The presence of small neutrino mass is indispensable to explicate the oscillation among different flavours of neutrino. By the addition of a right handed neutral lepton with the standard model fermions, it is possible to generate tiny neutrino mass. Such additional fermion may induce non-unitarity to the $3\times 3$ PMNS mixing matrix which influences the propagation of neutrino in space-time. In this work the effect of non-unitary mixing matrix is analyzed in neutrino oscillati…
The presence of nonstandard neutrino interactions (NSI) has a large effect on the precision measurements at next generation neutrino oscillation experiments. Other type of experiments are needed to constrain the NSI parameter space. We study the constraints on NSI with electrons from current and future $e^+e^-$ collider experiments including Belle II, STCF and CEPC. We find that Belle II and STCF will provide competitive and complementary bounds on electron-type NSI parameters compared to the current global analysis, and strong improvements for the constraints on tau-type NSI. In addition, CEP…
Nonstandard interactions (NSIs), possible subleading effects originating from new physics beyond the Standard Model, may affect the propagation of neutrinos and eventually contribute to measurements of neutrino oscillations. Besides this, $ μ-τ$ reflection symmetry, naturally predicted by non-Abelian discrete flavor symmetries, has been very successful in explaining the observed leptonic mixing patterns. In this work, we study the combined effect of both. We present an $S_4$ flavor model with $μ-τ$ reflection symmetry realized in both neutrino masses and NSIs. Under this formalism, we perform …
We explore the effects of nonstandard neutrino interactions in the lower components of the solar neutrino spectrum which are predominant by the vacuum oscillations. The recent measurements of Borexino experiment between 2011 and 2015 provide a clean test to study the nonstandard neutrino interactions at the source (sun) and the at solar detector. In this work, first the possible standard model parameters are estimated from the combined data of the low energy regime and then the nonstandard effects at the source, at the detector, and from the interplay between source and detector parameters are…
Effects of physics beyond the standard model in the neutrino sector are conveniently incorporated through non-standard interaction parameters. Assuming new physics in the form of dimension-6 vector operators, a recent global analysis of neutrino oscillation data including results from COHERENT experiment suggests two favorable new physics scenarios. These are LMA-Light (with normal mass ordering) \& LMA-Dark (with inverted mass ordering) sectors of parameters. In this work, we study the effects of new physics solutions on Leggett-Garg-type (LGtI) inequality which quantifies temporal correlatio…
Quantum speed limit time for bipartite entanglement in neutrino oscillations in matter with nonstandard interactions
Indian Institute of Science, Bangalore（印度科学学院）；SVKM’s Narsee Monjee Institute of Management Studies (NMIMS) Deemed-to-be-University（SVKM纳尔西·蒙吉管理研究所（NMIMS））；Indian Institute of Technology Jodhpur（焦特普尔印度理工学院）；University of Hyderabad（海德拉巴大学）
We consider the impact of neutral-current (NC) non-standard neutrino interactions (NSI) on the determination of the neutrino mass ordering. We show that in presence of NSI there is an exact degeneracy which makes it impossible to determine the neutrino mass ordering and the octant of the solar mixing angle $θ_{12}$ at oscillation experiments. The degeneracy holds at the probability level and for arbitrary matter density profiles, and hence, solar, atmospheric, reactor, and accelerator neutrino experiments are affected simultaneously. The degeneracy requires order-one corrections from NSI to th…
We study the matter effect caused by nonstandard neutrino interactions (NSI) in the next generation long-baseline neutrino experiments, DUNE, T2HK and T2HKK. If multiple NSI parameters are nonzero, the potential of these experiments to detect CP violation, determine the mass hierarchy and constrain NSI is severely impaired by degeneracies between the NSI parameters and by the generalized mass hierarchy degeneracy. In particular, a cancellation between leading order terms in the appearance channels when $ε_{eτ} = \cotθ_{23} ε_{eμ}$, strongly affects the sensitivities to these two NSI parameters…
We discuss the impact of matter density profile shape on the determination of nonstandard neutrino matter interactions (NSI) in the context of the long baseline accelerator experiments such as Deep Underground Neutrino Experiment (DUNE). The primary scientific goals of DUNE are to determine the neutrino mass hierarchy, the leptonic CP violation phase, and the existence of new physics beyond the standard model of particles. Here we study the role of different earth matter density profiles on the question of observing standard oscillation as wells as NSI at DUNE. We consider two different earth …
We analyze the energy and zenith angle distributions of the latest 2-year IceCube dataset of upward going atmospheric neutrinos to constrain sterile neutrinos at the eV scale in the 3+1 scenario. We find that the parameters favored by a combination of LSND and MiniBooNE data are excluded at more than the 99% C.L. We explore the impact of nonstandard matter interactions on this exclusion, and find that the exclusion holds for nonstandard interactions (NSI) that are within the stringent model-dependent bounds set by collider and neutrino scattering experiments. However, for large NSI parameters …
Neutrino interactions with an external environment can in influence the neutrino oscillation pattern and the oscillations can be damped as a result of the neutrino quantum decoherence. In particular, the quantum decoherence of neutrino states engendered by the neutrino radiative decay accounting for the nonstandard interactions (NSI) leads to the suppression of flavor neutrino oscillations in the solar neutrino fluxes.
The muon decay-at-rest ($μ$-DAR) facility provides us with an ideal platform to probe purely muonic charged-current nonstandard neutrino interactions (NSIs). We propose to probe this class of NSI effects using antineutrinos from a $μ$-DAR source in conjunction with neutrinos from the future Tokai to Kamioka superbeam experiment with megaton Hyper Kamiokande detector (T2HK). Even though muonic NSIs are absent in neutrino production at T2HK, we show that our proposed hybrid setup comprising $μ$-DAR and T2HK helps in alleviating the parameter degeneracies that can arise in data. Analytic consider…
We study how nonstandard neutrino interactions (NSI) may be probed by a combination of coherent elastic neutrino-nucleus scattering, neutrino oscillation and collider data, from COHERENT, DUNE, T2HK and the high-luminosity (HL) LHC. We focus on NSI induced by a new flavored gauge boson $Z'$ in a generic anomaly-free ultraviolet-complete model. For $Z'$ masses above 10 GeV, the HL-LHC has the best sensitivity regardless of the flavor structure of the model. For masses between 0.01 GeV-10 GeV, current LHCb data and future COHERENT data have the best sensitivity unless the $Z'$ couplings to the f…
We explore the possibility of probing the nonstandard interactions between the neutrino and a hypothetical massive scalar or pseudoscalar via neutrino flavor transformation in supernovae. We find that in the ultrarelativistic limit, the effective interaction between the neutrinos vanishes if neutrinos are Dirac fermions but not if they are Majorana fermions. The impact of the new neutrino interaction upon the flavor transformation above the neutrinosphere is calculated in the context of the multi-angle "neutrino bulb model". We find that the addition of the nonstandard neutrino self-interactio…
Non-unitary neutrino mixing implies an extra CP violating phase that can fake the leptonic Dirac CP phase $δ_{CP}$ of the simplest three-neutrino mixing benchmark scheme. This would hinder the possibility of probing for CP violation in accelerator-type experiments. We take T2K and T2HK as examples to demonstrate the degeneracy between the "standard" (or "unitary") and "non-unitary" CP phases. We find, under the assumption of non-unitary mixing, that their CP sensitivities severely deteriorate. Fortunately, the TNT2K proposal of supplementing T2(H)K with a $μ$DAR source for better measurement o…
Nonstandard interactions (NSI) of neutrinos with matter can significantly alter neutrino flavor evolution in supernovae with the potential to impact explosion dynamics, nucleosynthesis, and the neutrinos signal. In this paper, we explore, both numerically and analytically, the landscape of neutrino flavor transformation effects in supernovae due to NSI and find a new, heretofore unseen transformation processes can occur. These new transformations can take place with NSI strengths well below current experimental limits. Within a broad swath of NSI parameter space, we observe symmetric and stand…
