Mohan Narayan

Institute of Chemical Technology, Mumbai, Mumbai, State of Maharashtra, India

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Publications (23)35.57 Total impact

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    Mohan Narayan
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    ABSTRACT: We summarize the constraints on three flavor neutrino mixing coming from data. We first map out the allowed region in the three neutrino parameter space using solar and atmospheric neutrino data. We then incorporate the results of reactor and long baseline experiments in our analysis and show that the parameter space is drastically reduced. We conclude by pointing out that the results of Borexino and SNO will further help in constraining the parameter space.
    Pramana 04/2012; 54(1):155-172. · 0.56 Impact Factor
  • Bipin Singh Koranga, Mohan Narayan
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    ABSTRACT: We study the effects of neutrino mass hierarchy, above the GUT scale. We assume that the neutrino masses and mixing arise through physics at a scale intermediate between Planck scale and the electroweak breaking scale. We also assume that, just above the electroweak breaking scale, neutrino masses are nearly degenerate and their mixing is bi-maximal. Quantum gravity (Planck scale effects) lead to an effective SU(2) L ×U(1) invariant dimension-5 Lagrangian involving neutrino and Higgs fields. On symmetry breaking, this operator gives rise to correction to the above masses and mixing. The nature of gravitational interaction demands that the element of this perturbation matrix should be independent of flavor indices. In this paper, we study the quantum gravity effects on neutrino mass square difference for normal and invert neutrino mass hierarchy, namely modified dispersion relation for D31¢\Delta_{31}' above the GUT scale. KeywordsNeutrino mass hierarchy–Planck scale effects
    International Journal of Theoretical Physics 01/2011; 50(6):1868-1875. · 1.09 Impact Factor
  • Bipin Singh Koranga, Mohan Narayan
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    ABSTRACT: Quantum gravity (Planck scale effects) lead to an effective SU(2) L ×U(1) invariant dimension-5 Lagrangian involving neutrino and Higgs fields. On symmetry breaking, this operator gives rise to correction to the above masses and mixing. The gravitational interaction M X =M pl , we find that for degenerate neutrino mass spectrum, it is shown that the Majorana phase of the neutrino mixing matrix can effects in neutrino oscillation probability.
    International Journal of Theoretical Physics 01/2011; 50(6):1831-1836. · 1.09 Impact Factor
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    ABSTRACT: The neutrino parameters determined from the solar neutrino data and the anti-neutrino parameters determined from KamLAND reactor experiment are in good agreement with each other. However, the best fit points of the two sets differ from each other by about $10^{-5}$ eV$^2$ in mass-square differenc and by about $2^\circ$ in the mixing angle. Future solar neutrino and reactor anti-neutrino experiments are likely to reduce the uncertainties in these measurements. This, in turn, can lead to a signal for CPT violation in terms a non-zero difference between neutrino and anti-neutrino parameters. In this paper, we propose a CPT violating mass matrix which can give rise to the above differences in both mass-squared difference and mixing angle and study the constraints imposed by the data on the parameters of the mass matrix.
    International Journal of Theoretical Physics 12/2009; 50. · 1.09 Impact Factor
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    Veniamin Berezinsky, Mohan Narayan
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    ABSTRACT: We study the constraints on gravity scale $M_P$ in extra-dimension gravitational theory, obtained from gravity-induced processes. The obtained constraints are subdivided into strong (though not robust) and reliable (though less strong). The strong constraints can be in principle relaxed due to some broken gauge symmetries, e.g. family symmetry. The strongest constraint is given by neutrino oscillations. For different assumptions the lower bound on $M_P$ is $10^{15} - 10^{18}$ GeV. However, it can be, in principle, reduced by broken family symmetry. More reliable bounds are due to flavor-conserved operators or those which change the flavors within one family. These bounds, obtained using the electron mass and width of $\pi \to e\nu$ decay, are $1\times 10^5$ GeV and $5\times 10^5$ GeV, for these two cases, respectively.
    Physical review D: Particles and fields 06/2007;
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    ABSTRACT: We consider the effect of Planck scale operators on neutrino mixing. We assume that GUT scale operators give rise to degenerate neutrino masses with bimaximal mixing. Quantum gravity (Planck scale) effects lead to an effective SU(2)L*U(1) invariant dimension-5 Lagrangian involving neutrino and Higgs fields. This gives rise to additional terms in the neutrino mass matrix on electroweak symmetry breaking. These additional terms can be considered as a perturbation to the GUT scale bi-maximal neutrino mass matrix. We assume that the gravitational interaction is flavour blind and compute the deviations of the three neutrino mixing angles due to the Planck scale effects. We find that the changes in theta13, and theta23 are very small but the change in solar mixing angle theta12 can be as large as 3.5 degrees.
    Physics Letters B 12/2006; · 4.57 Impact Factor
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    ABSTRACT: At present there is good agreement between the neutrino mass-squared difference determined from the solar neutrino data and the anti-neutrino mass-squared difference determined from the KamLAND reactor anti-neutrino experiment. However, the central values of the two cases differ from each other by about $10^{-5}$ eV$^2$. An improvement in the accuracy of both the solar neutrino experiments and reactor anti-neutrino experiments can establish the existence of a non-zero difference between neutrino and anti-neutrino mass-squared differences and provide a signal for CPT violation. In this paper, we show how such a difference can arise through the CPT violating neutrino mass terms from Planck scale physics. Comment: 10 pages, 4 figures
    07/2006;
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    ABSTRACT: The recent measurement of Delta_{sol} by the KamLAND experiment with very small errors, makes definitive predictions for the energy dependence of the solar neutrino survival probability P_{ee}. We fix Delta_{sol} to be the KamLAND best fit value of 8*10^{-5} eV^2 and study the energy dependence of P_{ee} for solar neutrinos in the framework of two flavour oscillations and also of three flavour oscillations. For the case of two flavour oscillations, P_{ee} has a measurable slope in the 5-8 MeV range but the solar spectrum measurements in this range find P_{ee} to be flat. The predicted values of P_{ee}, even for the best fit value of theta_{sol}, differ by 2 to 3 sigma from the Super-K measured values in each of the three energy bins of the 5-8 MeV range. If future measurements of solar neutrinos by Super-K and SNO find a flat spectrum with reduced error bars (by a factor of 2), it will imply that two flavour oscillations can no longer explain both KamLAND data and the solar spectrum. However a flat solar neutrino spectrum and the Delta_{sol} measured by KamLAND can be reconciled in a three flavour oscillation framework with a moderate value of theta_{13} approx 13 degrees.
    International Journal of Theoretical Physics 03/2005; 50(5). · 1.09 Impact Factor
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    ABSTRACT: We address the question whether low-scale gravity alone can generate the neutrino mass matrix needed to accommodate the observed phenomenology. In low-scale gravity the neutrino mass matrix in the flavor basis is characterized by one parameter (the gravity scale M_X) and by an exact or approximate flavor blindness (namely, all elements of the mass matrix are of comparable size). Neutrino masses and mixings are consistent with the observational data for certain values of the matrix elements, but only when the spectrum of mass is inverted or degenerate. For the latter type of spectra the parameter M_{ee} probed in double beta experiments and the mass parameter probed by cosmology are close to existing upper limits. Comment: 10 pages, 1 figure
    Journal of High Energy Physics 01/2004; · 5.62 Impact Factor
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    ABSTRACT: We consider non-renormalizable 1/MX interaction terms as a perturbation of the conventional neutrino mass matrix. Particular attention is given to the gravitational interaction with MX=MPl. We find that for the degenerate neutrino mass spectrum, the considered perturbation generates a non-zero Ue3 which is within reach of the high performance neutrino factories and just on the borderline to be of interest for supernova physics. For the hierarchical mass spectrum this effect is small. For 1/MX interaction terms with MX about the GUT scale, a detectable Ue3 term is induced for the hierarchical mass spectra also. Numerical estimates are given for all the above mentioned cases and renormalization effects are considered.
    Physics Letters B 05/2003; · 4.57 Impact Factor
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    ABSTRACT: Sterile neutrinos are studied as subdominant contribution to solar neutrino physics. The mirror-matter neutrinos are considered as sterile neutrinos. We use the symmetric mirror model with gravitational communication between mirror and visible sectors. This communication term provides mixing between visible and mirror neutrinos with the basic scale μ=vEW2/MPl=2.5×10−6 eV, where vEW=174 GeV is the vacuum expectation value of the standard electroweak group and MPl is the Planckian mass. It is demonstrated that each mass eigenstate of active neutrinos splits into two states separated by small Δm2. Unsuppressed oscillations between active and sterile neutrinos (νa↔νs) occur only in transitions between each of these close pairs (“windows”). These oscillations are characterized by very small Δm2 and can suppress the flux and distort spectrum of pp-neutrinos in detectable way. The other observable effect is anomalous seasonal variation of neutrino flux, which appears in LMA solution. The considered subdominant neutrino oscillations νa↔νs can reveal itself as big effects in observations of supernova neutrinos and high-energy (HE) neutrinos. In the case of HE neutrinos they can provide a very large diffuse flux of active neutrinos unconstrained by the e–m cascade upper limit.
    Nuclear Physics B 01/2003; · 4.33 Impact Factor
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    ABSTRACT: Recently it was suggested that two very different mass-squared differences play a role in atmospheric neutrino oscillations. The larger of these also accounts for the LSND result and the smaller of these also drives the solar neutrino oscillations. We consider the predictions of this scheme for long-baseline experiments. We find that high statistics experiments, such as MINOS, can observe a clean signal for this scheme, which is clearly distinguishable from the usual scheme of atmospheric neutrino oscillations driven by a single mass-squared difference.
    10/2000;
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    Mohan Narayan, S. Uma Sankar
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    ABSTRACT: We study the effect of the matter term on the evolution of the solar neutrinos when the neutrino parameters are those of the `just-so' case. The extreme non-adiabatic effects at the edge of the sun reduce the expression for the survival probability in the just-so case to that of the vacuum case. This conclusion is independent of the width of the extreme non-adiabatic region, which is a function of the density profile of the sun beyond $r > 0.9 R_s$. However, in its propagation, neutrino encounters regions of moderate (non-extreme) non-adiabticity. Neutrino traversal through these regions give corrections to the survival probability which are profile dependent.
    05/2000;
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    Mohan Narayan, S. Uma Sankar
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    ABSTRACT: We consider νμ→νe oscillations in long baseline experiments within a three flavor oscillation framework. A non-zero measurement of this oscillation probability implies that the (13) mixing angle φ is non-zero. We consider the effect of neutrino propagation through the matter of Earth’s crust and show that, given the constraints from solar neutrino and CHOOZ data, matter effects enhance the mixing for neutrinos rather than for anti-neutrinos. We need data from two different experiments with different baseline lengths (such as K2K and MINOS) to discern the effect of the matter term.
    Physical review D: Particles and fields 12/1999; 61(1).
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    ABSTRACT: The solar neutrino counting rate in a real time detector like Super--Kamiokanda, SNO, or Borexino is enhanced due to neutrino oscillations in the Moon during a partial or total solar eclipse. The enhancement is calculated as a function of the neutrino parameters in the case of three flavor mixing. This enhancement, if seen, can further help to determine the neutrino parameters. Comment: 24 Pages Revtex, 8 figures as one ps file. To appear in Phys. Rev. D; Some typos corrected and a reference added
    Physical Review D 08/1999; · 4.69 Impact Factor
  • Mohan Narayan, G. Rajasekaran, S. Uma Sankar
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    ABSTRACT: We analyze the recent result of the CHOOZ Collaboration in the context of mixing and oscillations between all the three neutrino flavors. If one assumes the hierarchy among the vacuum mass eigenvalues δ21≪δ31 where δ21=μ22-μ12 and δ31=μ32-μ12, then the CHOOZ result puts a strong constraint on the allowed values of the (13) mixing angle φ. It is also shown that, in light of the CHOOZ result, the maximum contribution of the νμ↔νe oscillation channel to the atmospheric neutrino anomaly is less than 7 percent, thus demonstrating that the atmospheric neutrino anomaly is mainly due to νμ↔ντ oscillations. Most importantly the CHOOZ result now excludes a large part of the three flavor parameter space which was previously allowed as solutions to the solar and atmospheric neutrino problems.
    Physical Review D 01/1998; 58(3). · 4.69 Impact Factor
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    Mohan Narayan, G. Rajasekaran, S. Uma Sankar
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    ABSTRACT: We analyze the recent result of the CHOOZ collaboration in the context of mixing and oscillations between all the three neutrino flavors. If one assumes a hierarchy among the vacuum mass eigenvalues (\delta_{21} \ll \delta_{31}), then the CHOOZ result limits the (13) mixing angle \phi to quite small values. This in turn limits the contribution of the \nu_e <--> \nu_\mu oscillation channel to the atmospheric neutrino anomaly to less than 10 percent. It also implies that the solution to the solar neutrino problem is effectively \nu_e <--> \nu_\mu oscillation and that of the atmospheric neutrino problem is effectively \nu_\mu <--> \nu_\tau. Comment: 6 pages of text and 4 figures
    12/1997;
  • Mohan Narayan, G. Rajasekaran, Rahul Sinha
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    ABSTRACT: It is pointed out that the enhancement of the solar neutrino rate in a real time detector like Super-Kamioka, SNO or Borexino due to neutrino oscillations in the moon during a partial or total solar eclipse may be observable. The enhancement is calculated as a function of the neutrino parameters in the case of three flavor mixing. This enhancement if seen, can further help to determine the neutrino parameters.
    03/1997;
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    Mohan Narayan, G. Rajasekaran, Rahul Sinha
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    ABSTRACT: We investigate the time-of-night variation of solar neutrino rate which will be of relevance to Super-Kamioka and Sudbury neutrino detectors in the framework of oscillations among the three flavors. An analytical method of computing the regeneration in the earth is presented. If day-night effect is seen, we show how the study of the time-of-night variation will allow the determination of the neutrino parameters. Comment: 4 Pages Revtex with three embedded figures. In the revised version the earth-regeneration effect has been calculated in an analytical formulation that takes into account the variation (both smooth and discontinuous) of the density in the earth. More graphs and refrences are also added
    Modern Physics Letters A 02/1997; · 1.11 Impact Factor
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    Mohan Narayan, G. Rajasekaran, S. Uma Sankar
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    ABSTRACT: We analyze the atmospheric neutrino data in the context of three flavor neutrino oscillations taking account of the matter effects in the earth. With the hierarchy among the vacuum mass eigenvalues $\mu_3^2 \gg \mu_2^2 \geq \mu_1^2$, the solution of the atmospheric neutrino problem depends on $\delta_{31}=\mu_3^2 - \mu_1^2$ and the $13$ and $23$ mixing angles $\phi$ and $\psi$. Whereas the sub-GeV atmospheric neutrino data imposes only a lower limit on $\delta_{31} > 10^{-3} eV^2$, the zenith angle dependent suppression observed in the multi-GeV data limits $\delta_{31}$ from above also. The allowed regions of the parameter space are strongly constrained by the multi-GeV data. Combined with our earlier solution to the solar neutrino problem which depends on $\delta_{21}= \mu_2^2-\mu_1^2$ and the $12$ and $13$ mixing angles $\omega$ and $\phi$, we have obtained the ranges of values of the five neutrino parameters which solve both the solar and the atmospheric neutrino problems simultaneously. Comment: 21 pages Revtex, 7 figures as 7 ps files, Zenith angle binned multi-Gev analysis redone with the Kamiokande detector efficiencies included
    Physical review D: Particles and fields 07/1996;