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1.
  • Abdallah, Waleed, et al. (author)
  • FIMP dark matter candidate(s) in a B - L model with inverse seesaw mechanism
  • 2019
  • In: Journal of High Energy Physics (JHEP). - : SPRINGER. - 1126-6708 .- 1029-8479. ; :6
  • Journal article (peer-reviewed)abstract
    • The non-thermal dark matter (DM) production via the so-called freeze-in mechanism provides a simple alternative to the standard thermal WIMP scenario. In this work, we consider a popular U(1)(B-L) extension of the standard model (SM) in the context of inverse seesaw mechanism which has at least one (fermionic) FIMP DM candidate. Due to the added Z(2) symmetry, a SM gauge singlet fermion, with mass of order keV, is stable and can be a warm DM candidate. Also, the same Z(2) symmetry helps the lightest right-handed neutrino, with mass of order GeV, to be a stable or long-lived particle by making a corresponding Yukawa coupling very small. This provides a possibility of a two component DM scenario as well. Firstly, in the absence of a GeV DM component (i.e., without tuning its corresponding Yukawa coupling to be very small), we consider only a keV DM as a single component DM, which is produced by the freeze-in mechanism via the decay of the extra Z gauge boson associated to U(1)(B-L) and can consistently explain the DM relic density measurements. In contrast with most of the existing literature, we have found a reasonable DM production from the annihilation processes. After numerically studying the DM production, we show the dependence of the DM relic density as a function of its relevant free parameters. We use these results to obtain the parameter space regions that are compatible with the DM relic density bound. Secondly, we study a two component DM scenario and emphasize that the current DM relic density bound can be satisfied for a wide range of parameter space.
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2.
  • Abe, K., et al. (author)
  • Supernova Model Discrimination with Hyper-Kamiokande
  • 2021
  • In: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 916:1
  • Journal article (peer-reviewed)abstract
    • Core-collapse supernovae are among the most magnificent events in the observable universe. They produce many of the chemical elements necessary for life to exist and their remnants-neutron stars and black holes-are interesting astrophysical objects in their own right. However, despite millennia of observations and almost a century of astrophysical study, the explosion mechanism of core-collapse supernovae is not yet well understood. Hyper-Kamiokande is a next-generation neutrino detector that will be able to observe the neutrino flux from the next galactic core-collapse supernova in unprecedented detail. We focus on the first 500 ms of the neutrino burst, corresponding to the accretion phase, and use a newly-developed, high-precision supernova event generator to simulate Hyper-Kamiokande's response to five different supernova models. We show that Hyper-Kamiokande will be able to distinguish between these models with high accuracy for a supernova at a distance of up to 100 kpc. Once the next galactic supernova happens, this ability will be a powerful tool for guiding simulations toward a precise reproduction of the explosion mechanism observed in nature.
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3.
  • Abi, B., et al. (author)
  • First results on ProtoDUNE-SP liquid argon time projection chamber performance from a beam test at the CERN Neutrino Platform
  • 2020
  • In: Journal of Instrumentation. - : IOP Publishing. - 1748-0221. ; 15:12
  • Journal article (peer-reviewed)abstract
    • The ProtoDUNE-SP detector is a single-phase liquid argon time projection chamber with an active volume of 7.2 x 6.1 x 7.0 m(3). It is installed at the CERN Neutrino Platform in a specially-constructed beam that delivers charged pions, kaons, protons, muons and electrons with momenta in the range 0.3 GeV/c to 7 GeV/c. Beam line instrumentation provides accurate momentum measurements and particle identification. The ProtoDUNE-SP detector is a prototype for the first far detector module of the Deep Underground Neutrino Experiment, and it incorporates full-size components as designed for that module. This paper describes the beam line, the time projection chamber, the photon detectors, the cosmic-ray tagger, the signal processing and particle reconstruction. It presents the first results on ProtoDUNE-SP's performance, including noise and gain measurements, dE/dx calibration for muons, protons, pions and electrons, drift electron lifetime measurements, and photon detector noise, signal sensitivity and time resolution measurements. The measured values meet or exceed the specifications for the DUNE far detector, in several cases by large margins. ProtoDUNE-SP's successful operation starting in 2018 and its production of large samples of high-quality data demonstrate the effectiveness of the single-phase far detector design.
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4.
  • Abi, B., et al. (author)
  • Long-baseline neutrino oscillation physics potential of the DUNE experiment : DUNE Collaboration
  • 2020
  • In: European Physical Journal C. - : Springer Nature. - 1434-6044 .- 1434-6052. ; 80:10
  • Journal article (peer-reviewed)abstract
    • The sensitivity of the Deep Underground Neutrino Experiment (DUNE) to neutrino oscillation is determined, based on a full simulation, reconstruction, and event selection of the far detector and a full simulation and parameterized analysis of the near detector. Detailed uncertainties due to the flux prediction, neutrino interaction model, and detector effects are included. DUNE will resolve the neutrino mass ordering to a precision of 5 sigma, for all delta CP values, after 2 years of running with the nominal detector design and beam configuration. It has the potential to observe charge-parity violation in the neutrino sector to a precision of 3 sigma (5 sigma) after an exposure of 5 (10) years, for 50% of all delta CP values. It will also make precise measurements of other parameters governing long-baseline neutrino oscillation, and after an exposure of 15 years will achieve a similar sensitivity to sin22 theta 13 to current reactor experiments.
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5.
  • Abi, B., et al. (author)
  • Neutrino interaction classification with a convolutional neural network in the DUNE far detector
  • 2020
  • In: Physical Review D. - : American Physical Society (APS). - 2470-0010 .- 2470-0029. ; 102:9
  • Journal article (peer-reviewed)abstract
    • The Deep Underground Neutrino Experiment is a next-generation neutrino oscillation experiment that aims to measure CP-violation in the neutrino sector as part of a wider physics program. A deep learning approach based on a convolutional neural network has been developed to provide highly efficient and pure selections of electron neutrino and muon neutrino charged-current interactions. The electron neutrino (antineutrino) selection efficiency peaks at 90% (94%) and exceeds 85% (90%) for reconstructed neutrino energies between 2-5 GeV. The muon neutrino (antineutrino) event selection is found to have a maximum efficiency of 96% (97%) and exceeds 90% (95%) efficiency for reconstructed neutrino energies above 2 GeV. When considering all electron neutrino and antineutrino interactions as signal, a selection purity of 90% is achieved. These event selections are critical to maximize the sensitivity of the experiment to CP-violating effects.
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6.
  • Abi, B., et al. (author)
  • Prospects for beyond the Standard Model physics searches at the Deep Underground Neutrino Experiment DUNE Collaboration
  • 2021
  • In: European Physical Journal C. - : Springer Nature. - 1434-6044 .- 1434-6052. ; 81:4
  • Journal article (peer-reviewed)abstract
    • The Deep Underground Neutrino Experiment (DUNE) will be a powerful tool for a variety of physics topics. The high-intensity proton beams provide a large neutrino flux, sampled by a near detector system consisting of a combination of capable precision detectors, and by the massive far detector system located deep underground. This configuration sets up DUNE as a machine for discovery, as it enables opportunities not only to perform precision neutrino measurements that may uncover deviations from the present three-flavor mixing paradigm, but also to discover new particles and unveil new interactions and symmetries beyond those predicted in the Standard Model (SM). Of the many potential beyond the Standard Model (BSM) topics DUNE will probe, this paper presents a selection of studies quantifying DUNE's sensitivities to sterile neutrino mixing, heavy neutral leptons, non-standard interactions, CPT symmetry violation, Lorentz invariance violation, neutrino trident production, dark matter from both beam induced and cosmogenic sources, baryon number violation, and other new physics topics that complement those at high-energy colliders and significantly extend the present reach.
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7.
  • Abud, A. Abed, et al. (author)
  • Deep Underground Neutrino Experiment (DUNE) Near Detector Conceptual Design Report
  • 2021
  • In: Instruments. - : MDPI AG. - 2410-390X. ; 5:4, s. 31-31
  • Journal article (peer-reviewed)abstract
    • The Deep Underground Neutrino Experiment (DUNE) will be a powerful tool for a variety of physics topics. The high-intensity proton beams provide a large neutrino flux, sampled by a near detector system consisting of a combination of capable precision detectors, and by the massive far detector system located deep underground. This configuration sets up DUNE as a machine for discovery, as it enables opportunities not only to perform precision neutrino measurements that may uncover deviations from the present three-flavor mixing paradigm, but also to discover new particles and unveil new interactions and symmetries beyond those predicted in the Standard Model (SM). Of the many potential beyond the Standard Model (BSM) topics DUNE will probe, this paper presents a selection of studies quantifying DUNE’s sensitivities to sterile neutrino mixing, heavy neutral leptons, non-standard interactions, CPT symmetry violation, Lorentz invariance violation, neutrino trident production, dark matter from both beam induced and cosmogenic sources, baryon number violation, and other new physics topics that complement those at high-energy colliders and significantly extend the present reach.
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8.
  • Agarwalla, Sanjib Kumar, et al. (author)
  • Probing neutrino oscillation parameters using high power superbeam from ESS
  • 2014
  • In: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :12, s. 020-
  • Journal article (peer-reviewed)abstract
    • A high-power neutrino superbeam experiment at the ESS facility has been proposed such that the source-detector distance falls at the second oscillation maximum, giving very good sensitivity towards establishing CP violation. In this work, we explore the comparative physics reach of the experiment in terms of leptonic CP-violation, precision on atmospheric parameters, non-maximal theta(23), and its octant for a variety of choices for the baselines. We also vary the neutrino vs. the anti-neutrino running time for the beam, and study its impact on the physics goals of the experiment. We find that for the determination of CP violation, 540 km baseline with 7 years of nu and 3 years of (v) over bar (7v + 3 (v) over bar) run-plan performs the best and one expects a 5 sigma sensitivity to CP violation for 48% of true values of delta (CP). The projected reach for the 200 km baseline with 7v + 3 (v) over bar run-plan is somewhat worse with 5 sigma sensitivity for 34% of true values of delta(CP). On the other hand, for the discovery of a non-maximal theta(23) and its octant, the 200 km baseline option with run-plan performs significantly better than the other baselines. A 5 sigma determination of a non-maximal theta(23) can be made if the true value of sin(2) theta(23) less than or similar to 0.45 or sin(2) theta(23) greater than or similar to 0.57. The octant of theta(23) could be resolved at 5 sigma if the true value of sin(2) theta(23) less than or similar to 0.43 or greater than or similar to 0.59, irrespective of delta(CP).
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9.
  • Aguilar, J., et al. (author)
  • Study of nonstandard interactions mediated by a scalar field at the ESSnuSB experiment
  • 2024
  • In: Physical Review D. - : American Physical Society (APS). - 2470-0010 .- 2470-0029. ; 109:11
  • Journal article (peer-reviewed)abstract
    • In this paper, we study scalar mediator induced nonstandard interactions (SNSIs) in the context of the ESSnuSB experiment. In particular, we study the capability of ESSnuSB to put bounds on the SNSI parameters and also study the impact of SNSIs in the measurement of the leptonic ?⁢? phase ??⁢?. Existence of SNSIs modifies the neutrino mass matrix and this modification can be expressed in terms of three diagonal real parameters (??⁢?, ??⁢?, and ??⁢?) and three off-diagonal complex parameters (??⁢?, ??⁢?, and ??⁢?). Our study shows that the upper bounds on the parameters ??⁢? and ??⁢? depend upon how Δ⁢?231 is minimized in the theory. However, this is not the case when one tries to measure the impact of SNSIs on ??⁢?. Further, we show that the ?⁢? sensitivity of ESSnuSB can be completely lost for certain values of ??⁢? and ??⁢? for which the appearance channel probability becomes independent of ??⁢?.
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10.
  • Belanger, Genevieve, et al. (author)
  • WIMP and FIMP dark matter in singlet-triplet fermionic model
  • 2022
  • In: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; :11
  • Journal article (peer-reviewed)abstract
    • We present an extension of the SM involving three triplet fermions, one triplet scalar and one singlet fermion, which can explain both neutrino masses and dark matter. One triplet of fermions and the singlet are odd under a Z(2) symmetry, thus the model features two possible dark matter candidates. The two remaining Z(2)-even triplet fermions can reproduce the neutrino masses and oscillation parameters consistent with observations. We consider the case where the singlet has feeble couplings while the triplet is weakly interacting and investigate the different possibilities for reproducing the observed dark matter relic density. This includes production of the triplet WIMP from freeze-out and from decay of the singlet as well as freeze-in production of the singlet from decay of particles that belong to the thermal bath or are thermally decoupled. While freeze-in production is usually dominated by decay processes, we also show cases where the annihilation of bath particles give substantial contribution to the final relic density. This occurs when the new scalars are below the TeV scale, thus in the reach of the LHC. The next-to-lightest odd particle can be long-lived and can alter the successful BBN predictions for the abundance of light elements, these constraints are relevant in both the scenarios where the singlet or the triplet are the long-lived particle. In the case where the triplet is the DM, the model is subject to constraints from ongoing direct, indirect and collider experiments. When the singlet is the DM, the triplet which is the next-to-lightest odd particle can be long-lived and can be probed at the proposed MATHUSLA detector. Finally we also address the detection prospects of triplet fermions and scalars at the LHC.
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11.
  • Bélanger, Geneviève, et al. (author)
  • WIMP and FIMP dark matter in singlet-triplet fermionic model
  • 2022
  • In: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; 2022:11
  • Journal article (peer-reviewed)abstract
    • We present an extension of the SM involving three triplet fermions, one triplet scalar and one singlet fermion, which can explain both neutrino masses and dark matter. One triplet of fermions and the singlet are odd under a Z2 symmetry, thus the model features two possible dark matter candidates. The two remaining Z2-even triplet fermions can reproduce the neutrino masses and oscillation parameters consistent with observations. We consider the case where the singlet has feeble couplings while the triplet is weakly interacting and investigate the different possibilities for reproducing the observed dark matter relic density. This includes production of the triplet WIMP from freeze-out and from decay of the singlet as well as freeze-in production of the singlet from decay of particles that belong to the thermal bath or are thermally decoupled. While freeze-in production is usually dominated by decay processes, we also show cases where the annihilation of bath particles give substantial contribution to the final relic density. This occurs when the new scalars are below the TeV scale, thus in the reach of the LHC. The next-to-lightest odd particle can be long-lived and can alter the successful BBN predictions for the abundance of light elements, these constraints are relevant in both the scenarios where the singlet or the triplet are the long-lived particle. In the case where the triplet is the DM, the model is subject to constraints from ongoing direct, indirect and collider experiments. When the singlet is the DM, the triplet which is the next-to-lightest odd particle can be long-lived and can be probed at the proposed MATHUSLA detector. Finally we also address the detection prospects of triplet fermions and scalars at the LHC.
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12.
  • Biswas, A., et al. (author)
  • Dark Matter, Neutrino Mass and Muon (g-2) in a U(1)Lu LTModel
  • 2018
  • In: Springer Proceedings in Physics. - Cham : Springer Science+Business Media B.V.. - 9783319731704 ; , s. 919-921
  • Conference paper (peer-reviewed)abstract
    • Existence of dark matter (DM) and neutrino masses are the two beyond standard model (BSM) problems. In this work, we have extended the standard model (SM) gauge group by a local ymmetry. We have extended the SM particle list by adding three right handed (RH) neutrinos to generate neutrino masses by Type I seesaw mechanism. We have also added two SM singlet scalars, one of them can serve as the DM candidate while other one takes VEV and gives masses to RH neutrinos and additional gauge boson. Beside explaining the neutrino masses and peculiar mixing angles of the neutrinos, we have also explained DM phenomenology and the muon (anomaly by the one loop contribution of the additional gauge boson.
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13.
  • Biswas, Anirban, et al. (author)
  • Explaining the 3.5 keV X-ray line in a L mu - L-tau extension of the inert doublet model
  • 2018
  • In: Journal of Cosmology and Astroparticle Physics. - : Institute of Physics Publishing (IOPP). - 1475-7516. ; :2
  • Journal article (peer-reviewed)abstract
    • We explain the existence of neutrino masses and their flavour structure, dark matter relic abundance and the observed 3.5 keV X-ray line within the framework of a gauged U(1) L-mu-L-tau extension of the "scotogenic" model. In the U(1) L-mu-L-tau symmetric limit, two of the RH neutrinos are degenerate in mass, while the third is heavier. The U(1) L-mu-L-tau symmetry is broken spontaneously. Firstly, this breaks the mu-tau symmetry in the light neutrino sector. Secondly, this results in mild splitting of the two degenerate RH neutrinos, with their mass difference given in terms of the U(1) L-mu-L-tau breaking parameter. Finally, we get a massive Z(mu tau) gauge boson. Due to the added Z(2) symmetry under which the RH neutrinos and the inert doublet are odd, the canonical Type-I seesaw is forbidden and the tiny neutrino masses are generated radiatively at one loop. The same Z(2) symmetry also ensures that the lightest RH neutrino is stable and the other two can only decay into the lightest one. This makes the two nearly-degenerate lighter neutrinos a two-component dark matter, which in our model are produced by the freeze-in mechanism via the decay of the Z(mu tau) gauge boson in the early universe. We show that the next-to-lightest RH neutrino has a very long lifetime and decays into the lightest one at the present epoch explaining the observed 3.5 keV line.
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14.
  • Biswas, A., et al. (author)
  • FIMP and muon (g − 2) in a U(1)Lμ−Lτ model
  • 2017
  • In: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; 2017:2
  • Journal article (peer-reviewed)abstract
    • The tightening of the constraints on the standard thermal WIMP scenario has forced physicists to propose alternative dark matter (DM) models. One of the most popular alternate explanations of the origin of DM is the non-thermal production of DM via freeze-in. In this scenario the DM never attains thermal equilibrium with the thermal soup because of its feeble coupling strength (∼10−12) with the other particles in the thermal bath and is generally called the Feebly Interacting Massive Particle (FIMP). In this work, we present a gauged U(1)Lμ−Lτ extension of the Standard Model (SM) which has a scalar FIMP DM candidate and can consistently explain the DM relic density bound. In addition, the spontaneous breaking of the U(1)Lμ−Lτ gauge symmetry gives an extra massive neutral gauge boson Zμτ which can explain the muon (g − 2) data through its additional one-loop contribution to the process. Lastly, presence of three right-handed neutrinos enable the model to successfully explain the small neutrino masses via the Type-I seesaw mechanism. The presence of the spontaneously broken U(1)Lμ−Lτ gives a particular structure to the light neutrino mass matrix which can explain the peculiar mixing pattern of the light neutrinos.
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15.
  • Biswas, Anirban, et al. (author)
  • Inverse seesaw and dark matter in a gauged B - L extension with flavour symmetry
  • 2018
  • In: Journal of High Energy Physics (JHEP). - : Springer Berlin/Heidelberg. - 1126-6708 .- 1029-8479. ; :8
  • Journal article (peer-reviewed)abstract
    • We propose a model which generates neutrino masses by the inverse seesaw mechanism, provides a viable dark matter candidate and explains the muon (g - 2) anomaly. The Standard Model (SM) gauge group is extended with a gauged U(1)(B-L) as well as a gauged U(1)(L mu-L tau). While U(1)(L mu-L tau) is anomaly free, the anomaly introduced by U(1)(B-L) is cancelled between the six SM singlet fermions introduced for the inverse seesaw mechanism and four additional chiral fermions introduced in this model. After spontaneous symmetry breaking the four chiral fermionic degrees of freedom combine to give two Dirac states. The lightest Dirac fermion becomes stable and hence the dark matter candidate. We focus on the region of the parameter space where the dark matter annihilates to the right-handed neutrinos, relating the dark matter sector with the neutrino sector. The U(1)(L mu-L tau), gauge symmetry provides a flavour structure to the inverse seesaw framework, successfully explaining the observed neutrino masses and mixings. We study the model parameters in the light of neutrino oscillation data and find correlation between them. Values of some of the model parameters are shown to be mutually exclusive between normal and inverted ordering of the neutrino mass eigenstates. Moreover, the muon (g - 2) anomaly can be explained by the additional contribution arising from U(1)(L mu-L tau) gauge boson.
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16.
  • Biswas, Anirban, et al. (author)
  • Neutrino mass, dark matter and anomalous magnetic moment of muon in a U(1)(L mu-LT) model
  • 2016
  • In: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :9
  • Journal article (peer-reviewed)abstract
    • The observation of neutrino masses, mixing and the existence of dark matter are amongst the most important signatures of physics beyond the Standard Model (SM). In this paper, we propose to extend the SM by a local L-mu-L-T gauge symmetry, two additional complex scalars and three right-handed neutrinos. The L-mu-L-T gauge symmetry is broken spontaneously when one of the scalars acquires a vacuum expectation value. The L-mu-L-T gauge symmetry is known to be anomaly free and can explain the beyond SM measurement of the anomalous muon (g - 2) through additional contribution arising from the extra Z(mu T) mediated diagram. Small neutrino masses are explained naturally through the Type-I seesaw mechanism, while the mixing angles are predicted to be in their observed ranges due to the broken L-mu-L-T symmetry. The second complex scalar is shown to be stable and becomes the dark matter candidate in our model. We show that while the Z(mu T) portal is ineffective for the parameters needed to explain the anomalous muon (g 2) data, the correct dark matter relic abundance can easily be obtained from annihilation through the Higgs portal. Annihilation of the scalar dark matter in our model can also explain the Galactic Centre gamma ray excess observed by Fermi-LAT. We show the predictions of our model for future direct detection experiments and neutrino oscillation experiments.
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17.
  • Biswas, Anirban, et al. (author)
  • Neutrino mass, leptogenesis and FIMP dark matter in a U(1)(B-L) model
  • 2017
  • In: European Physical Journal C. - : Springer. - 1434-6044 .- 1434-6052. ; 77:12
  • Journal article (peer-reviewed)abstract
    • The Standard Model (SM) is inadequate to explain the origin of tiny neutrino masses, the dark matter (DM) relic abundance and the baryon asymmetry of the Universe. In this work, to address all three puzzles, we extend the SM by a local U(1)(B-L) gauge symmetry, three right-handed (RH) neutrinos for the cancellation of gauge anomalies and two complex scalars having non-zero U(1)(B-L) charges. All the newly added particles become massive after the breaking of the U(1)(B-L) symmetry by the vacuum expectation value (VEV) of one of the scalar fields phi(H). The other scalar field, phi(DM), which does not have any VEV, becomes automatically stable and can be a viable DM candidate. Neutrino masses are generated using the Type-I seesaw mechanism, while the required lepton asymmetry to reproduce the observed baryon asymmetry can be attained from the CP violating out of equilibrium decays of the RH neutrinos in TeV scale. More importantly within this framework, we study in detail the production of DM via the freeze-in mechanism considering all possible annihilation and decay processes. Finally, we find a situation when DM is dominantly produced from the annihilation of the RH neutrinos, which are at the same time also responsible for neutrino mass generation and leptogenesis.
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18.
  • Blennow, Mattias, 1980-, et al. (author)
  • A combined study of source, detector and matter non-standard neutrino interactions at DUNE
  • 2016
  • In: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; 2016:8
  • Journal article (peer-reviewed)abstract
    • We simultaneously investigate source, detector and matter non-standard neutrino interactions at the proposed DUNE experiment. Our analysis is performed using a Markov Chain Monte Carlo exploring the full parameter space. We find that the sensitivity of DUNE to the standard oscillation parameters is worsened due to the presence of non-standard neutrino interactions. In particular, there are degenerate solutions in the leptonic mixing angle θ23 and the Dirac CP-violating phase δ. We also compute the expected sensitivities at DUNE to the non-standard interaction parameters. We find that the sensitivities to the matter non-standard interaction parameters are substantially stronger than the current bounds (up to a factor of about 15). Furthermore, we discuss correlations between the source/detector and matter non-standard interaction parameters and find a degenerate solution in θ23. Finally, we explore the effect of statistics on our results.
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19.
  • Blennow, Mattias, et al. (author)
  • Exploring source and detector non-standard neutrino interactions at ESS nu SB
  • 2015
  • In: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :9
  • Journal article (peer-reviewed)abstract
    • We investigate source and detector non-standard neutrino interactions at the proposed ESS nu SB experiment. We analyze the effect of non-standard physics at the probability level, the event-rate level and by a full computation of the ESS nu SB setup. We find that the precision measurement of the leptonic mixing angle theta(23) at ESS nu SB is robust in the presence of non-standard interactions, whereas that of the leptonic CP-violating phase delta is worsened at most by a factor of two. We compute sensitivities to all the relevant source and decector non-standard interaction parameters and find that the sensitivities to the parameters epsilon(s)(mu e) and epsilon(d)(mu e) are comparable to the existing limits in a realistic scenario, while they improve by a factor of two in an optimistic scenario. Finally, we show that the absence of a near detector compromises the sensitivity of ESS nu SB to non-standard interactions.
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20.
  • Burgman, A., et al. (author)
  • The ESSnuSB Design Study: Overview and Future Prospects
  • 2023
  • In: Universe. - : MDPI. - 2218-1997. ; 9:8
  • Research review (peer-reviewed)abstract
    • ESSnuSB is a design study for an experiment to measure the CP violation in the leptonic sector at the second neutrino oscillation maximum using a neutrino beam driven by the uniquely powerful ESS linear accelerator. The reduced impact of systematic errors on sensitivity at the second maximum allows for a very precise measurement of the CP violating parameter. This review describes the fundamental advantages of measurement at the second maximum, the necessary upgrades to the ESS linac in order to produce a neutrino beam, the near and far detector complexes, and the expected physics reach of the proposed ESSnuSB experiment, concluding with the near future developments aimed at the project realization.
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21.
  • Choubey, Sandhya, et al. (author)
  • A study of invisible neutrino decay at DUNE and its effects on theta(23) measurement
  • 2018
  • In: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; 2018:2
  • Journal article (peer-reviewed)abstract
    • We study the consequences of invisible decay of neutrinos in the context of the DUNE experiment. We assume that the third mass eigenstate is unstable and decays to a light sterile neutrino and a scalar or a pseudo-scalar. We consider DUNE running in 5 years neutrino and 5 years antineutrino mode and a detector volume of 40 kt. We obtain the expected sensitivity on the rest-frame life-time tau(3) normalized to the mass m(3) as tau(3)/m(3) > 4.50 x 10(-11) s/eV at 90% C.L. for a normal hierarchical mass spectrum. We also find that DUNE can discover neutrino decay for tau(3)/m(3) > 4.27 x 10(-11) s/eV at 90% C.L. In addition, for an unstable tau(3) with an illustrative value of tau(3)/m(3) = 1.2 x 10(-11) s/eV, the no decay case could get disfavoured at the 3 sigma C.L. At 90% C.L. the expected precision range for this true value is obtained as 1.71 x 10(-11 >) tau(3)/m(3) > 9.29 x 10(-12) in units of s/eV. We also study the correlation between a non-zero tau(3)/m(3) and standard oscillation parameters and find an interesting correlation in the appearance and disappearance channels with the mixing angle theta(23). This alters the octant sensitivity of DUNE, favorably (unfavorably) for true theta(23) in the lower (higher) octant. The effect of a decaying neutrino does not alter the hierarchy or CP violation discovery sensitivity of DUNE in a discernible way.
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22.
  • Choubey, Sandhya (author)
  • Atmospheric neutrinos : Status and prospects
  • 2016
  • In: Nuclear Physics B. - : Elsevier. - 0550-3213 .- 1873-1562.
  • Journal article (peer-reviewed)abstract
    • We present an overview of the current status of neutrino oscillation studies at atmospheric neutrino experiments. While the current data gives some tantalising hints regarding the neutrino mass hierarchy, octant of θ23 and δCP, the hints are not statistically significant. We summarise the sensitivity to these sub-dominant three-generation effects from the next-generation proposed atmospheric neutrino experiments. We next present the prospects of new physics searches such as non-standard interactions, sterile neutrinos and CPT violation studies at these experiments.
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23.
  • Choubey, Sandhya, et al. (author)
  • Bounds on non-standard neutrino interactions using PINGU
  • 2014
  • In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 739, s. 357-364
  • Journal article (peer-reviewed)abstract
    • We investigate the impact of non-standard neutrino interactions (NSIs) on atmospheric neutrinos using the proposed PINGU experiment. In particular, we focus on the matter NSI parameters epsilon(mu tau) and vertical bar epsilon(tau tau)-epsilon(mu mu)vertical bar that have previously been constrained by the Super-Kamiokande experiment. First, we present approximate analytical formulas for the difference of the muon neutrino survival probability with and without the above-mentioned NSI parameters. Second, we calculate the atmospheric neutrino events at PINGU in the energy range (2-100) GeV, which follow the trend outlined on probability level. Finally, we perform a statistical analysis of PINGU. Using three years of data, we obtain bounds from PINGU given by -0.0043 (-0.0048) < epsilon(mu tau) < 0.0047 (0.0046) and -0.03 (-0.016) < epsilon(tau tau) < 0.017 (0.032) at 90% confidence level for normal (inverted) neutrino mass hierarchy, which improve the Super-Kamiokande bounds by one order of magnitude. In addition, we show the expected allowed contour region in the epsilon-ettplane if NSIs exist in Nature and the result suggests that there is basically no correlation between epsilon(mu tau) and epsilon(tau tau).
  •  
24.
  • Choubey, Sandhya, et al. (author)
  • Exploring fake solutions in the sterile neutrino sector at long-baseline experiments
  • 2019
  • In: European Physical Journal C. - : SPRINGER. - 1434-6044 .- 1434-6052. ; 79:11
  • Journal article (peer-reviewed)abstract
    • Active-sterile neutrino mixing is known to affect the neutrino oscillation probabilities at both short as well as long-baselines. In particular, constraints on active-sterile neutrino oscillation parameters can be obtained from long-baseline experiments such as T2HK and DUNE. We present here existence of fake solution in the appearance channel for the 3 + 1 scenario at long-baseline experiments. We show that the appearance probability is same for values of Delta m(41)(2) for which the fast oscillations are averaged out and for Delta m(41)(2) = (1/2) Delta m(31)(2). The fake solution does not appear for the disappearance channel.
  •  
25.
  • Choubey, Sandhya, et al. (author)
  • Exploring invisible neutrino decay at ESSnuSB
  • 2021
  • In: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; 2021:5
  • Journal article (peer-reviewed)abstract
    • We explore invisible neutrino decay in which a heavy active neutrino state decays into a light sterile neutrino state and present a comparative analysis of two baseline options, 540 km and 360 km, for the ESSnuSB experimental setup. Our analysis shows that ESSnuSB can put a bound on the decay parameter tau (3)/m(3) = 2.64 (1.68) x 10(-11) s/eV for the baseline option of 360 (540) km at 3 sigma. The expected bound obtained for 360 km is slightly better than the corresponding one of DUNE for a charged current (CC) analysis. Furthermore, we show that the capability of ESSnuSB to discover decay, and to measure the decay parameter precisely, is better for the baseline option of 540 km than that of 360 km. Regarding effects of decay in delta (CP) measurements, we find that in general the CP violation discovery potential is better in the presence of decay. The change in CP precision is significant if one assumes decay in data but no decay in theory.
  •  
26.
  • Choubey, Sandhya, et al. (author)
  • Exploring invisible neutrino decay at ESSnuSB
  • 2021
  • In: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; 2021:5
  • Journal article (peer-reviewed)abstract
    • We explore invisible neutrino decay in which a heavy active neutrino state decays into a light sterile neutrino state and present a comparative analysis of two baseline options, 540 km and 360 km, for the ESSnuSB experimental setup. Our analysis shows that ESSnuSB can put a bound on the decay parameter τ3/m3 = 2.64 (1.68) × 10−11 s/eV for the baseline option of 360 (540) km at 3σ. The expected bound obtained for 360 km is slightly better than the corresponding one of DUNE for a charged current (CC) analysis. Furthermore, we show that the capability of ESSnuSB to discover decay, and to measure the decay parameter precisely, is better for the baseline option of 540 km than that of 360 km. Regarding effects of decay in δCP measurements, we find that in general the CP violation discovery potential is better in the presence of decay. The change in CP precision is significant if one assumes decay in data but no decay in theory.
  •  
27.
  • Choubey, Sandhya (author)
  • Future prospects in neutrino physics
  • 2021
  • In: International Journal of Modern Physics E. - : World Scientific Pub Co Pte Ltd. - 0218-3013. ; 30:09
  • Journal article (peer-reviewed)abstract
    • Neutrino physics has come a long way and made great strides in the past decades. We discuss the prospects of what more can be learned in this field in the forthcoming neutrino oscillation facilities. We will mostly focus on the potential of the long-baseline experiments and the atmospheric neutrino experiments. Sensitivity of these experiments to standard neutrino oscillation parameters will be presented. We will also discuss the prospects of new physics searches at these facilities.
  •  
28.
  • Choubey, Sandhya, et al. (author)
  • Imprints of a light sterile neutrino at DUNE, T2HK, and T2HKK
  • 2017
  • In: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 96:5
  • Journal article (peer-reviewed)abstract
    • We evaluate the impact of sterile neutrino oscillations in the so-called 3 + 1 scenario on the proposed long baseline experiment in USA and Japan. There are two proposals for the Japan experiment which are called T2HK and T2HKK. We show the impact of sterile neutrino oscillation parameters on the expected sensitivity of T2HK and T2HKK to mass hierarchy, CP violation and octant of theta(23) and compare it against that expected in the case of standard oscillations. We add the expected ten years data from DUNE and present the combined expected sensitivity of T2HKK + DUNE to the oscillation parameters. We do a full marginalization over the relevant parameter space and show the effect of the magnitude of the true sterile mixing angles on the physics reach of these experiments. We show that if one assumes that the source of CP violation is the standard CP phase alone in the test case, then it appears that the expected CP violation sensitivity decreases due to sterile neutrinos. However, if we give up this assumption, then the CP sensitivity could go in either direction. The impact on expected octant of theta(23) and mass hierarchy sensitivity is shown to depend on the magnitude of the sterile mixing angles in a nontrivial way.
  •  
29.
  • Choubey, Sandhya, et al. (author)
  • Indirect searches for dark matter signatures at ino
  • 2020
  • In: Journal of Physics. - : IOP Publishing.
  • Conference paper (peer-reviewed)abstract
    • Neutrino fluxes could arise due to annihilation of Weakly Interactive Massive Particles (WIMPs) in the center of the sun. We study the prospects of search for muon events due to such neutrinos at the upcoming Iron CALorimeter (ICAL) detector to be housed at India-based Neutrino Observatory (INO). Although the atmospheric neutrinos will pose a serious background to the signal neutrinos produced through WIMP annihilation, the former could be supressed significantly by using the directional property of signal neutrinos. For 50kt×10 years of ICAL running and WIMP masses (mχ ) between 3-100 GeV, we perform a χ2 analysis and present expected exclusion regions in the σβ-mx and σβι-mx plane, where σβ and σβι are the WIMP-nucleon Spin-Dependent (SD) and Spin-Independent (SI) scattering cross-sections, respectively. For mx = 25 GeV, the expected 90 % C.L. exclusion limit on σβ are σβ < 7.82 x 10-41 cm2 for τ+τ- channel and σβ < 1.23 10-39 cm2 for 66 channel. For same m×, the expected 90 % C.L. exclusion limits on σβι are σβι < 8.97 × 10-43 cm2 for τ +τ - channel and σβι < 1.43×10-41 cm2 for 66 channel.
  •  
30.
  • Choubey, Sandhya, et al. (author)
  • Inflation and dark matter in the inert doublet model
  • 2017
  • In: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :11
  • Journal article (peer-reviewed)abstract
    • We discuss inflation and dark matter in the inert doublet model coupled non-minimally to gravity where the inert doublet is the inflaton and the neutral scalar part of the doublet is the dark matter candidate. We calculate the various inflationary parameters like n(s), r and P-s and then proceed to the reheating phase where the inflaton decays into the Higgs and other gauge bosons which are non-relativistic owing to high effective masses. These bosons further decay or annihilate to give relativistic fermions which are finally responsible for reheating the universe. At the end of the reheating phase, the inert doublet which was the inflaton enters into thermal equilibrium with the rest of the plasma and its neutral component later freezes out as cold dark matter with a mass of about 2TeV.
  •  
31.
  • Choubey, Sandhya, et al. (author)
  • Invisible neutrino decay in the light of NOvA and T2K data
  • 2018
  • In: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :8
  • Journal article (peer-reviewed)abstract
    • We probe for evidence of invisible neutrino decay in the latest NOvA and T2K data. It is seen that both NOvA and T2K data sets are better fitted when one allows for invisible neutrino decay. We consider a scenario where only the third neutrino mass eigenstate nu(3) is unstable and decays into invisible components. The best-fit value for the nu(3) lifetime is obtained as tau(3)/m(3) = 3.16 x 10(-12) s/eV from the analysis of the NOvA neutrino data and tau(3)/m(3) = 1.0x10(-11) s/eV from the analysis of the T2K neutrino and anti-neutrino data. The combined analysis of NOvA and T2K gives tau(3)/m(3) = 5.01 x 10(-12) s/eV as the best-fit lifetime. However, the statistical significance for this preference is weak with the no-decay hypothesis still allowed at close to 1.5 sigma C.L. from the combined data sets, while the two experiment individually are consistent with no-decay even at the 1 sigma C.L. At 3 sigma C.L., the NOvA and T2K data give a lower limit on the neutrino lifetime of tau(3)/m(3) is tau(3)/m(3) >= 7.22 x 10(-13) s/eV and tau(3)/m(3) >= 1.41 x 10(-12) s/eV, respectively, while NOvA and T2K combined constrain tau(3)/m(3) >= 1.50 x 10(-12) s/eV. We also show that in presence of decay the best-fit value in the sin(2) theta(23) vs. Delta m(32)(2) plane changes significantly and the allowed regions increase significantly towards higher sin(2) theta(23).
  •  
32.
  • Choubey, Sandhya, et al. (author)
  • Measuring the sterile neutrino CP phase at DUNE and T2HK
  • 2018
  • In: European Physical Journal C. - : SPRINGER. - 1434-6044 .- 1434-6052. ; 78:4
  • Journal article (peer-reviewed)abstract
    • The CP phases associated with the sterile neutrino cannot be measured in the dedicated short-baseline experiments being built to test the sterile neutrino hypothesis. On the other hand, these phases can be measured in long-baseline experiments, even though the main goal of these experiments is not to test or measure sterile neutrino parameters. In particular, the sterile neutrino phase delta(24) affects the charged-current electron appearance data in long-baseline experiment. In this paper we show how well the sterile neutrino phase delta(24) can be measured by the next-generation long-baseline experiments DUNE, T2HK (and T2HKK). We also show the expected precision with which this sterile phase can be measured by combining the DUNE data with data from T2HK or T2HKK. The T2HK experiment is seen to be able to measure the sterile phase delta(24) to a reasonable precision. We also present the sensitivity of these experiments to the sterile mixing angles, both by themselves, as well as when DUNE is combined with T2HK or T2HKK.
  •  
33.
  • Choubey, Sandhya, et al. (author)
  • Neutrino mass ordering : Circumventing the challenges using synergy between T2HK and JUNO
  • 2022
  • In: Physical Review D. - : American Physical Society (APS). - 2470-0010 .- 2470-0029. ; 106:11
  • Journal article (peer-reviewed)abstract
    • One of the major open problems of neutrino physics is mass ordering (MO). We discuss the prospects of measuring MO with two under-construction experiments T2HK and JUNO. JUNO alone is expected to measure MO with greater than 3σ significance as long as certain experimental challenges are met. In particular, JUNO needs better than 3% energy resolution for MO measurement. On the other hand, T2HK has rather poor prospects at measuring the MO, especially for certain ranges of the CP violating parameter δCP, posing a major drawback for T2HK. In this article we show that the synergy between JUNO and T2HK will bring twofold advantage. First, the synergy between the two experiments helps us determine the MO at a very high significance. With the baseline setup of the two experiments, we have a greater than 9σ determination of the MO for all values of δCP. Second, the synergy also allows us to relax the constraints on the two experiments. We show that JUNO could perform extremely well even for an energy resolution of 5%, while for T2HK the MO problem with "bad"values of δCP goes away. The MO sensitivity for the combined analysis is expected to be greater than 6σ for all values of δCP and with just 5% energy resolution for JUNO.
  •  
34.
  • Choubey, Sandhya, et al. (author)
  • Neutrino mass ordering : Circumventing the challenges using synergy between T2HK and JUNO
  • 2022
  • In: Physical Review D. - 2470-0010 .- 2470-0029. ; 106:11
  • Journal article (peer-reviewed)abstract
    • One of the major open problems of neutrino physics is mass ordering (MO). We discuss the prospects of measuring MO with two under-construction experiments T2HK and JUNO. JUNO alone is expected to measure MO with greater than 3 sigma significance as long as certain experimental challenges are met. In particular, JUNO needs better than 3% energy resolution for MO measurement. On the other hand, T2HK has rather poor prospects at measuring the MO, especially for certain ranges of the CP violating parameter delta(CP), posing a major drawback for T2HK. In this article we show that the synergy between JUNO and T2HK will bring twofold advantage. First, the synergy between the two experiments helps us determine the MO at a very high significance. With the baseline setup of the two experiments, we have a greater than 9 sigma determination of the MO for all values of delta(CP). Second, the synergy also allows us to relax the constraints on the two experiments. We show that JUNO could perform extremely well even for an energy resolution of 5%, while for T2HK the MO problem with bad values of delta(CP) goes away. The MO sensitivity for the combined analysis is expected to be greater than 6 sigma for all values of delta(CP) and with just 5% energy resolution for JUNO.
  •  
35.
  • Choubey, Sandhya (author)
  • Neutrino oscillations
  • 2017
  • In: Current Science. - : Indian National Science Academy. - 0011-3891. ; 112:7, s. 1381-1384
  • Journal article (peer-reviewed)abstract
    • Neutrinos are massless as proposed in the Standard Model of particle physics. However, neutrino experiments in the last few decades have revealed that neutrinos flavour oscillate, a scenario possible only if they have mass and mixing. Existence of neutrino mass was the first conclusive evidence of physics beyond the Standard Model, and explaining the smallness of the neutrino masses and peculiar mixing angles still remains a challenge for model-builders proposing beyond Standard Model scenarios. We give a brief introduction to the phenomenon of neutrino oscillations and showcase some recent work where we look for physics beyond the three-generation neutrino oscillation paradigm and its impact on future experiments.
  •  
36.
  • Choubey, Sandhya, et al. (author)
  • Neutrino physics with non-standard interactions at INO
  • 2015
  • In: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; 2015:12, s. 1-22
  • Journal article (peer-reviewed)abstract
    • Abstract: Non-standard neutrino interactions (NSI) involved in neutrino propagation inside Earth matter could potentially alter atmospheric neutrino fluxes. In this work, we look at the impact of these NSI on the signal at the ICAL detector to be built at the India-based Neutrino Observatory (INO). We show how the sensitivity to the neutrino mass hierarchy of ICAL changes in the presence of NSI. The mass hierarchy sensitivity is shown to be rather sensitive to the NSI parameters ϵeμ and ϵeτ , while the dependence on ϵμτ and ϵτ τ is seen to be very mild, once the χ2 is marginalised over oscillation and NSI parameters. If the NSI are large enough, the event spectrum at ICAL is expected to be altered and this can be used to discover new physics. We calculate the lower limit on NSI parameters above which ICAL could discover NSI at a given C.L. from 10 years of data. If NSI were too small, the null signal at ICAL can constrain the NSI parameters. We give upper limits on the NSI parameters at any given C.L. that one is expected to put from 10 years of running of ICAL. Finally, we give C.L. contours in the NSI parameter space that is expected to be still allowed from 10 years of running of the experiment.
  •  
37.
  • Choubey, Sandhya, et al. (author)
  • On resolving the dark LMA solution at neutrino oscillation experiments
  • 2020
  • In: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; :12
  • Journal article (peer-reviewed)abstract
    • In presence of non standard interactions (NSI), the solar neutrino data is consistent with two solutions, one close to the standard LMA solution with sin(2)theta (12)similar or equal to 0.31 and another with sin2 theta 12Dsimilar or equal to 0.69=1-sin2theta 12. The latter has been called the Dark LMA (DLMA) solution in the literature and essentially brings an octant degeneracy in the measurement of the mixing angle theta (12). This theta (12) octant degeneracy is hard to resolve via oscillations because of the existence of the so-called "generalised mass hierarchy degeneracy" of the neutrino mass matrix in presence of NSI. One might think that if the mass hierarchy is independently determined in a non-oscillation experiment such as neutrino-less double beta decay, one might be able to break the theta (12) octant degeneracy. In this paper we study this in detail in the context of long-baseline experiments (P-mu mu channel) as well as reactor experiments (P-ee channel) and show that if we combine information from both long-baseline and reactor experiments we can find the correct octant and hence value of theta (12). We elaborate the reasons for it and study the prospects of determining the theta (12) octant using T2HK, DUNE and JUNO experiments. Of course, one would need information on the neutrino mass hierarchy as well.
  •  
38.
  • Choubey, Sandhya, et al. (author)
  • Prospects of indirect searches for dark matter at INO
  • 2018
  • In: Journal of Cosmology and Astroparticle Physics. - : IOP PUBLISHING LTD. - 1475-7516. ; :5
  • Journal article (peer-reviewed)abstract
    • The annihilation of Weakly Interactive Massive Particles (WIMP) in the centre of the sun could give rise to neutrino fluxes. We study the prospects of searching for these neutrinos at the upcoming Iron CALorimeter (ICAL) detector to be housed at the India-based Neutrino Observatory (INO). We perform ICAL simulations to obtain the detector efficiencies and resolutions in order to simulate muon events in ICAL due to neutrinos coming from annihilation of WIMP in the mass range m(chi) = (3 - 100) GeV. The atmospheric neutrinos pose a major background for these indirect detection studies and can be reduced using the fact that the signal comes only from the direction of the sun. For a given WIMP mass, we find the opening angle theta(90) such that 90 % of the signal events are contained within this angle and use this cone-cut criteria to reduce the atmospheric neutrino background. The reduced background is then weighted by the solar exposure function at INO to obtain the final background spectrum for a given WIMP mass. We perform a chi(2) analysis and present expected exclusion regions in the sigma(SD) - m(chi) and sigma(SI) - m(chi), where sigma(SD) and sigma(SI) are the WIMP-nucleon Spin-Dependent (SD) and Spin-Independent (SI) scattering cross-section, respectively. For a 10 years exposure and m(chi) = 25 GeV, the expected 90 % C. L. exclusion limit is found to be sigma(SD) < 6.87 x 10(-41) cm(2) and sigma(SI) < 7.75 x 10(-43) cm(2) for the tau(+) tau(-) annihilation channel and sigma(SD) < 1.14 x 10(-39) cm(2) and sigma(SI) < 1.30 x 10(-41) cm(2) for the b (b) over bar channel, assuming 100 % branching ratio for each of the WIMP annihilation channel.
  •  
39.
  • Choubey, Sandhya (author)
  • Prospects to determine the neutrino mass hierarchy
  • 2015
  • In: 50th Rencontres de Moriond on Electroweak Interactions and Unified Theories, EW 2015. - : ARISF. - 9782954640082 ; , s. 255-260
  • Conference paper (peer-reviewed)abstract
    • We will discuss the prospects of determining the neutrino mass hierarchy in the next generation proposed experiments. In particular, we will look at the expected sensitivity in atmospheric neutrino experiments, near future long baseline experiments and intermediate baseline reactor experiments. 
  •  
40.
  •  
41.
  • Choubey, Sandhya, et al. (author)
  • Sensitivity to neutrino decay with atmospheric neutrinos at the INO-ICAL detector
  • 2018
  • In: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 97:3
  • Journal article (peer-reviewed)abstract
    • Sensitivity of the magnetized Iron Calorimeter (ICAL) detector at the proposed India-based Neutrino Observatory (INO) to invisible decay of the mass eigenstate nu(3) using atmospheric neutrinos is explored. A full three-generation analysis including Earth matter effects is performed in a framework with both decay and oscillations. The wide energy range and baselines offered by atmospheric neutrinos are shown to be excellent for constraining the nu(3) lifetime. We find that with an exposure of 500 kton - yr the ICAL atmospheric experiment could constrain the. 3 lifetime to tau(3)/m(3) > 1.51 x 10(-10) s/eV at the 90% C.L. This is 2 orders of magnitude tighter than the bound from MINOS. The effect of invisible decay on the precision measurement of theta(23) and vertical bar Delta m(32)(2)vertical bar is also studied.
  •  
42.
  • Choubey, Sandhya, et al. (author)
  • Singlet-triplet fermionic dark matter and LHC phenomenology
  • 2018
  • In: European Physical Journal C. - : Springer New York LLC. - 1434-6044 .- 1434-6052. ; 78:4
  • Journal article (peer-reviewed)abstract
    • It is well known that for the pure standard model triplet fermionic WIMP-type dark matter (DM), the relic density is satisfied around 2 TeV. For such a heavy mass particle, the production cross-section at 13 TeV run of LHC will be very small. Extending the model further with a singlet fermion and a triplet scalar, DM relic density can be satisfied for even much lower masses. The lower mass DM can be copiously produced at LHC and hence the model can be tested at collider. For the present model we have studied the multi jet (≥2j) + missing energy ([InlineEquation not available: see fulltext.]) signal and show that this can be detected in the near future of the LHC 13 TeV run. We also predict that the present model is testable by the earth based DM direct detection experiments like Xenon-1T and in future by Darwin. 
  •  
43.
  • Choubey, Sandhya, et al. (author)
  • Study of invisible neutrino decay and oscillation in the presence of matter with a 50 kton magnetised iron detector
  • 2017
  • In: Proceedings of Science. - : Sissa Medialab Srl.
  • Conference paper (peer-reviewed)abstract
    • The sensitivity to the invisible decay of the mass eigenstate ν3 in the presence of Earth matter effects is studied. Only the charged current interactions of atmospheric νµ and νµ for 500 kTon year exposure of a future magnetised iron detector at INO are analysed. The analysis with observed muon energy in the range would give a constraint of τ3/m3 > 1.51×10−10 s/eV at 90% CL with this exposure. Here τ3 is the lifetime and m3 is the mass of ν3, when it is the heaviest. The effect of decay on the precision measurement of sin2 θ23 and |∆m232| and neutrino mass hierarchy are also studied. Since the presence of decay affects the oscillation amplitude rather than its phase, it is seen that the precision on sin2 θ23 worsens whereas that on |∆m232| is not much affected. Sensitivity to hierarchy also worsens slightly in the presence of the invisible decay of ν3
  •  
44.
  • Choudhury, Shouvik Roy, et al. (author)
  • Updated bounds on sum of neutrino masses in various cosmological scenarios
  • 2018
  • In: Journal of Cosmology and Astroparticle Physics. - : Institute of Physics Publishing (IOPP). - 1475-7516. ; :9
  • Journal article (peer-reviewed)abstract
    • We present strong bounds on the sum of three active neutrino masses ( Sigma m(v)) using selected cosmological datasets and priors in various cosmological models. We use the following baseline datasets: Cosmic Microwave Background (CMB) temperature data from Planck 2015, Baryon Acoustic Oscillations measurements from SDSS-III BOSS DR12, the newly released Type Ia supernovae (SNe Ia) dataset from Pantheon Sample, and a prior on the optical depth to reionization from 2016 Planck Intermediate results. We constrain cosmological parameters with these datasets with a Bayesian analysis in the background of Lambda CDM model with 3 massive active neutrinos. For this minimal Lambda CDM + Sigma m(v) model we find a upper bound of Sigma m(v) < 0.152 eV at 95% C.L. Adding the high-l polarization data from Planck strengthens this bound to Sigma m(v) < 0.118 eV, which is very close to the minimum required mass of Sigma m(v) similar or equal to 0.1 eV for inverted hierarchy. This bound is reduced to Sigma m(v) < 0.110 eV when we also vary r, the tensor to scalar ratio (Lambda CDM + r + Sigma m(v) model), and add an additional dataset, BK14, the latest data released from the Bicep-Keck collaboration (which we add only when r is varied). This bound is further reduced to Sigma m(v) < 0.101 eV in a cosmology with non-phantom dynamical dark energy (w(0)w(a)CDM + Sigma m(v) model with w(z) >= -1 for all z). Considering the w0waCDM + r + Sigma m(v) model and adding the BK14 data again, the bound can be even further reduced to Sigma m(v) < 0.093 eV. For the w0waCDM + Sigma m(v) model P without any constraint on w(z), the bounds however relax to Sigma m(v) < 0.276 eV. Adding a prior on the Hubble constant (H-0 = 73.24 +/- 1.74 km/sec/Mpc) from Hubble Space Telescope (HST), the above mentioned bounds further improve to Sigma m(v) < 0.117 eV, 0.091 eV, 0.085 eV, 0.082 eV, 0.078 eV and 0.247 eV respectively. This substantial improvement is mostly driven by a more than 3 sigma tension between Planck 2015 and HST measurements of H-0 and should be taken cautiously.
  •  
45.
  • Itow, Yoshitaka, et al. (author)
  • Construction status and prospects of the Hyper-Kamiokande project
  • 2022
  • In: 37th International Cosmic Ray Conference, ICRC 2021. - : Sissa Medialab Srl.
  • Conference paper (peer-reviewed)abstract
    • The Hyper-Kamiokande project is a 258-kton Water Cherenkov together with a 1.3-MW high-intensity neutrino beam from the Japan Proton Accelerator Research Complex (J-PARC). The inner detector with 186-kton fiducial volume is viewed by 20-inch photomultiplier tubes (PMTs) and multi-PMT modules, and thereby provides state-of-the-art of Cherenkov ring reconstruction with thresholds in the range of few MeVs. The project is expected to lead to precision neutrino oscillation studies, especially neutrino CP violation, nucleon decay searches, and low energy neutrino astronomy. In 2020, the project was officially approved and construction of the far detector was started at Kamioka. In 2021, the excavation of the access tunnel and initial mass production of the newly developed 20-inch PMTs was also started. In this paper, we present a basic overview of the project and the latest updates on the construction status of the project, which is expected to commence operation in 2027.
  •  
46.
  •  
47.
  • Lakshmi, S. M., et al. (author)
  • Sensitivity of INO ICAL to Neutrino Mass Hierarchy and θ23 Octant in Presence of Invisible Neutrino Decay in Matter
  • 2021
  • In: Springer Proceedings in Physics. - Singapore : Springer Nature. ; , s. 981-986
  • Conference paper (peer-reviewed)abstract
    • A study of the effect of invisible decay of the third neutrino mass eigen state ν3 on the determination of neutrino mass hierarchy and the octant of the mixing angle θ23 has been done. The decay is characterized by α3= m3/ τ3, where m3 is the mass of ν3 and τ3 its rest–frame lifetime. The effect of matter oscillations and decay have been taken into account. The studies are done with simulated charged current νμ and ν¯μ events in the proposed 50 kt INO ICAL detector. It is found that the mass hierarchy sensitivity is not much affected if the values of α3 are smaller than 2.35 × 10- 4 eV2 (which is the 90% C.L. limit on α3 from the analysis of MINOS data). A significant reduction in hierarchy sensitivity is observed for values of α3 as large as 2.35 × 10- 4 eV2. The dependence of sensitivity to mass ordering on θ23 is also studied. Octant sensitivity is found to increase (worsen) with increase in α3 if θ23 is in the first (second) octant, for non-zero values of α3&lt; 2.35 × 10- 4 eV2, as compared to the no decay case. For α3= 2.35 × 10- 4 eV2, the octant sensitivity is found to increase for both octants of θ23.
  •  
48.
  • Raikwal, Deepak, et al. (author)
  • Comprehensive study of Lorentz invariance violation in atmospheric and long-baseline experiments
  • 2023
  • In: Physical Review D. - : American Physical Society (APS). - 2470-0010 .- 2470-0029. ; 107:11
  • Journal article (peer-reviewed)abstract
    • In this paper, we have presented a comprehensive study of Lorentz invariance violation (LIV) in the context of the atmospheric neutrino experiment ICAL and the long-baseline experiments T2HK and DUNE. Our study consists of the full parameter space of the LIV parameters, i.e., six CPT-violating LIV parameters (aαβ) and six CPT-conserving LIV parameters (cαβ). In this study, our objective is to calculate the upper bound on all the LIV parameters with respect to the individual experiments as well as their combination. Our results show that DUNE gives the best sensitivity for the parameters aee, aeμ, aeτ, and aμτ in its 7 years of running, whereas ICAL gives the best sensitivity on aμμ, aμτ, cee, cμμ, cττ, and cμτ in its 10 years of running. For aττ, the sensitivities of DUNE and ICAL are almost same. The combination of T2HK, DUNE, and ICAL gives the best sensitivity for aeμ and aee with respect to all the existing bounds in the literature. For the CPT-even diagonal parameters cee and cμμ, our work provides the first-ever bounds.
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49.
  • Raikwal, Deepak, et al. (author)
  • Determining neutrino mass ordering with ICAL, JUNO and T2HK
  • 2023
  • In: The European Physical Journal Plus. - : Springer Nature. - 2190-5444. ; 138:2
  • Journal article (peer-reviewed)abstract
    • In this paper, we study the synergy among the future accelerator (T2HK), future atmospheric (ICAL) and future reactor (JUNO) neutrino experiments to determine the neutrino mass ordering. T2HK can measure the mass ordering only for favorable values of δCP, whereas the mass ordering sensitivity of JUNO is dependent on the energy resolution. Our results show that with a combination of T2HK, ICAL and JUNO one can have a mass ordering sensitivity of 7.2 σ even for the unfavorable value of δCP= 0 ∘ for T2HK and most conservative value of JUNO energy resolution of 5%/E(MeV). The synergy mainly comes because different oscillation channels prefer different values of |Δm312| in the fit when the mass-ordering χ2 is minimized. In this context, we also study: (i) effect of varying energy resolution of JUNO, (ii) the effect of longer run-time of ICAL, (iii) effect of different true values of θ23 and (iv) effect of octant degeneracy in the determination of neutrino mass ordering.
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50.
  • Raikwal, Deepak, et al. (author)
  • Earth tomography with the ICAL detector at INO
  • 2024
  • In: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 109:7
  • Journal article (peer-reviewed)abstract
    • Observing matter effects in atmospheric neutrinos traveling through the entire mantle and core of the Earth is a promising way of enhancing our understanding of Earth's density structure. In that context we study the prospects of Earth tomography with the ICAL detector at the India-based Neutrino Observatory. While this experiment is smaller in size in comparison to some of the other larger detectors being proposed, it is the only planned neutrino experiment with charge-identification sensitivity. In particular, ICAL can see matter effects separately in neutrinos and antineutrinos. This has been seen to enhance ICAL's sensitivity to earth matter effects and hence the mass ordering sensitivity for both normal and inverted mass orderings. It is therefore pertinent to see if the ICAL sensitivity to earth tomography is competitive or better with respect to other experiments, especially for the inverted mass ordering, where other experiments suffer reduced sensitivity. We present the sensitivity of ICAL to earth tomography by taking into consideration both the Earth's mass constraint as well as the hydrostatic equilibrium constraints.
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