In this work, 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 unfavourable 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) the effect of varying energy resolution of JUNO, (ii) the effect of longer run-time of ICAL, (iii) the effect of different true values of θ23 and (iv) the effect of octant degeneracy in the determination of neutrino mass ordering.

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.

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.

In this work we have re-investigated two different kinds of texture zero ansatz of the low energy neutrino mass matrix in view of the Dark-Large-Mixing-Angle (DLMA) solution of the solar neutrino problem which can arise in the presence of non-standard interactions. In particular we revisit the cases of (i) one zero mass matrices when the lowest neutrino mass is zero and (ii) one zero texture with a vanishing minor. In our study we find that for most of the cases, the texture zero conditions which are allowed for the LMA solution, are also allowed for the DLMA solution. However, we found two textures belonging to the case of one zero texture with a vanishing minor where LMA solution does not give a viable solution whereas DLMA solution does. We analyze all the possible texture zero cases belonging to these two kinds of texture zero structures in detail and present correlations between different parameters. We also present the predictions for the effective neutrino mass governing neutrino-less double beta decay for the allowed textures.

In this paper, we perform a comparative analysis between the future proposed longbaseline experiments ESSnuSB and T2HK in measuring the leptonic CP phase delta(CP). In particular, we study the effect of the neutrino mass ordering degeneracy and the leptonic mixing angle theta(23) octant degeneracy in the measurement of leptonic CP violation and precision for both experiments. Since the ESSnuSB (T2HK) experiment probes the second (first) oscillation maximum to study neutrino oscillations, the effect of these degeneracies are significantly different in both experiments. Our main conclusion is that for the ESSnuSB experiment, the information on the neutrino mass ordering does not play a major role in the determination of delta(CP), which is not the case for the T2HK experiment. However, the information on the true octant compromises the CP sensitivity of the ESSnuSB experiment as compared to T2HK if theta(23) lies in the lower octant. These conclusions are true for both the 540 km and 360 km baseline options for the ESSnuSB experiment. In addition, we investigate the effect of different running times in neutrino and antineutrino modes and the effect of theta(23) precision in measuring delta(CP).

Non-Abelian discrete symmetries provide an interesting opportunity to address the flavor puzzle in the lepton sector. However, the number of currently viable models based on such symmetries is rather large. High-precision measurements of the leptonic mixing parameters by future neutrino experiments, including ESSnuSB, T2HK, DUNE, and JUNO, will be crucial to test such models. We show that the complementarity among these experiments offers a powerful tool for narrowing down this broad class of lepton flavor models.

The muon decay-at-rest (mu-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 mu-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 mu-DAR and T2HK helps in alleviating the parameter degeneracies that can arise in data. Analytic considerations reveal that the oscillation probability is most sensitive to the NSI parameter in the mu-e sector. For this parameter, we show that the mu-DAR setup can improve on the existing bounds down to around 0.01, especially when the data are combined with neutrino data from T2HK experiment due to the lifting of parameter degeneracies. The high precision with which mu-DAR can measure delta(CP) is shown to be robust even in the presence of the considered NSIs. Finally, we show that the combination of mu-DAR along with T2HK can also be used to put mild constraints on the NSI phase in the vicinity of the maximal CP-violating value, for the chosen benchmark value of epsilon(mu e)(mu e) = 0.01.

We present a comprehensive analysis in the 3+1 active-sterile neutrino oscillation scenario for the sensitivity of the ESSnuSB experiment in the presence of light sterile neutrinos assuming both a far (FD) and a near (ND) detector. Our analysis show that when the ND is included, the results are significantly different compared to the ones obtained with the FD only. We find that the capability of ESSnuSB to constrain the sterile mixing parameters is sin(2) 2 theta(mu e)similar to 10(-4) for m(2) = 1 eV(2) if the ND is included and it becomes sin(2) 2 theta(mu e)similar to 10(-2) without the ND. Furthermore, we show that the sensitivity can go down to sin(2) 2 theta(mu e)similar to 10(-3) for the most conservative choice of the systematics on the ND. Comparing the sensitivity with T2HK, T2HKK, and DUNE by considering the FD only, we find that the sensitivity of ESSnuSB is smaller for most of the parameter space. Studying the CP violation sensitivity, we find that if the ND is included, it can be larger in the 3+1 scenario than in the standard one. However, if the ND is not included, the sensitivity is smaller compared to the one in the standard scenario. We also find that the CP violation sensitivity due to delta(13) is larger compared to the one induced by delta(24). The sensitivities are slightly better for the dominant neutrino running ratio of ESSnuSB.

We review and investigate lepton flavor models, stemming from discrete non- Abelian flavor symmetries, described by one or two free model parameters. First, we confront eleven one- and seven two-parameter models with current results on leptonic mixing angles from global fits to neutrino oscillation data. We find that five of the one- and five of the two-parameter models survive the confrontation test at 3 sigma. Second, we investigate how these ten one- and two-parameter lepton flavor models may be discriminated at the proposed ESSnuSB experiment in Sweden. We show that the three one-parameter models that predict sin delta(CP) = 0 can be distinguished from those two that predict vertical bar sin delta(CP)vertical bar = 1 by at least 7 sigma. Finally, we find that three of the five one-parameter models can be excluded by at least 5 sigma and two of the one-parameter as well as at most two of the five two-parameter models can be excluded by at least 3 sigma with ESSnuSB if the true values of the leptonic mixing parameters remain close to the present best-fit values.

It was shown that the tension between the mass-squared differences obtained from solar neutrinos and those acquired through KamLAND experiments may be solved by the introduction of a non-standard flavor-dependent interaction (NSI) in neutrino propagation. In this study, we discuss the possibility of testing such a hypothesis using the future long-baseline neutrino experiments T2HKK and DUNE. Assuming that the NSI does not exist, we provide the excluded region within the (D, N) plane, where D and N are the parameters appearing in the solar neutrino analysis conducted with the NSI. We find that the best fit value from the solar neutrino and KamLAND data (global analysis of a particular coupling to quarks) can be tested at more than 10σ(3σ) by these two experiments for most of the parameter space.