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-standar
d 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.
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 $delta_{rm{CP}}$ 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 $varepsilon^{mu e}_{mu e}=0.01$.
In this paper, we perform a comparative analysis between the future proposed long-baseline experiments ESSnuSB and T2HK in measuring the leptonic CP phase $delta_{rm CP}$. In particular, we study the effect of the neutrino mass ordering degeneracy an
d 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 $delta_{rm CP}$, 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 $delta_{rm CP}$.
The first hint of neutrino mass hierarchy is expected to come from the NO$ u$A experiment in Fermilab as the present best-fit parameter space i.e., normal hierarchy and $delta_{CP}=-90^circ$ is the favourable parameter space for NO$ u$A where there i
s no degeneracy. But this situation may change if the standard three flavour framework is not complete and there is existence of new physics. In this work we consider the presence of an extra light sterile neutrino at the eV scale and study the new degeneracies which are absent in the standard three flavour framework. We also study the effect of these new degeneracies on the hierarchy measurement of NO$ u$A.
In this work we study the the sensitivity of the T2HKK experiment to probe non-standard interaction in neutrino propagation. As this experiment will be statistically dominated due to its large detector volume and high beam-power, it is expected that
the sensitivity will be affected by systematics. This motivates us to study the effect of systematics in probing the non-standard interaction. We also compare our results with the other future proposed experiments i.e., T2HK, HK and DUNE.
It was shown that the tension between the mass-squared differences obtained from solar neutrinos and those acquired through KamLAND experiments may be solved by the introduction of a non-standard flavor-dependent interaction (NSI) in neutrino propaga
tion. In this study, we discuss the possibility of testing such a hypothesis using the future long-baseline neutrino experiments T2HKK and DUNE. Assuming that the NSI does not exist, we provide the excluded region within the ($epsilon_D$, $epsilon_N$) plane, where $epsilon_D$ and $epsilon_N$ 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 10$sigma$ (3$sigma$) by these two experiments for most of the parameter space.
T2HK and T2HKK are the proposed extensions of the of T2K experiments in Japan and DUNE is the future long-baseline program of Fermilab. All these three experiments will use extremely high beam power and large detector volumes to observe neutrino osci
llation. Because of the large statistics, these experiments will be highly sensitive to systematics. Thus a small change in the systematics can cause a significant change in their sensitivities. To understand this, we do a comparative study of T2HK, T2HKK and DUNE with respect to their systematic errors. Specifically we study the effect of the systematics in the determination of neutrino mass hierarchy, octant of the mixing angle $theta_{23}$ and $delta_{CP}$ in the standard three flavor scenario and also analyze the role of systematic uncertainties in constraining the parameters of the nonstandard interactions in neutrino propagation. Taking the overall systematics for signal and background normalization, we quantify how the sensitivities of these experiments change if the systematics are varied from $1%$ to $7%$.
If the flavor dependent non-standard interactions (NSI) in neutrino propagation exist, then the matter effect is modified and the modification is parametrized by the dimensionless parameter $epsilon_{alphabeta}~(alpha,beta=e, mu, tau)$. In this paper
we discuss the sensitivity of the T2HKK experiment, whose possibility is now seriously discussed as a future extension of the T2K experiment, to such NSI. On the assumption that $epsilon_{alphamu}=0~(alpha=e, mutau)$ and $epsilon_{tautau}=|epsilon_{etau}|/(1+epsilon_{ee})$, which are satisfied by other experiments to a good approximation, we find that, among the possible off-axis flux configurations of $1.3^circ$, $1.5^circ$, $2.0^circ$ and $2.5^circ$, the case of the off-axis angle $1.3^circ$ gives the highest sensitivity to $epsilon_{ee}$ and $|epsilon_{etau}|$. Our results show that the $1.3^circ$ off-axis configuration can exclude NSI for $|epsilon_{ee}|gtrsim 1$ or $|epsilon_{etau}|gtrsim 0.2$ at 3$sigma$. We also find that in the presence of NSI, T2HKK (for the off-axis angle $1.3^circ$) has better sensitivity to the two CP phases ($delta_{CP}$ and arg($epsilon_{e tau}$)) than DUNE. This is because of the synergy between the two detectors i.e., one at Kamioka and one at Korea. T2HKK has better sensitivity to the CP phases than the atmospheric neutrino experiment at Hyperkamiokande in inverted hierarchy, but in normal hierarchy the atmospheric neutrino experiment has the best sensitivity to the CP phases.
In this talk we present our results on the sensitivity to the neutrino mass hierarchy, the octant of the mixing angle and the CP phase in the future long baseline experiments T2HK and DUNE as well as in the atmospheric neutrino observation at Hyperkamiokande (HK).
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 osci
llation 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 $theta_{23}$ by NO$ u$A which excludes the maximal mixing at $2.5 sigma$ C.L. and (iii) a discrepancy in the $theta_{13}$ measurement by T2K which has a tension with the reactor best-fit value of $sin^2theta_{13}=0.021$ at $90%$ C.L. Our results show that all these three above mentioned anomalies can be explained if one assumes the existence of the non-standard interactions in neutrino propagation with $theta_{23}=45^circ$ and $sin^2theta_{13}=0.021$ in the case of normal hierarchy. In our scenario the phase of $epsilon_{etau}$ is zero and the most favorable value of the Dirac CP phase is approximately $255^circ$.
