arXiv subjects

Gulsheen Ahuja

Publications and source records attributed to Gulsheen Ahuja.

31 records · Page 2Linked to original sources

arXiv2012

Possible textures of the fermion mass matrices

Texture specific fermion mass matrices have played an important role in understanding several features of fermion masses and mixings. In the present work, we have given an overview of all possible cases of Fritzsch-like as well as non Fritzsch-like texture 6 and 5 zero fermion mass matrices. Further, for the case of texture 4 zero Fritzsch-like quark mass matrices, the issue of the hierarchy of the elements of the mass matrices and the role of their phases have been discussed. Furthermore, the case of texture 4 zero Fritzsch-like lepton mass matrices has also been discussed with an emphasis on the hierarchy of neutrino masses for both Majorana and Dirac neutrinos.

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arXiv2012

Exploring the likelihood of CP violation in neutrino oscillations

In view of the latest T2K and MINOS observations regarding the mixing angle s_{13}, we have explored the possibility of existence of CP violation in the leptonic sector. Using hints from the construction of the 'db' unitarity triangle in the quark sector, we have made an attempt to construct the 'ν_1.ν_3' leptonic unitarity triangle, suggesting a good possibility of having non zero CP violation.

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arXiv2010

Exploring the parameter space of texture 4 zero quark mass matrices

We have attempted to extend the parameter space of the elements of the texture 4 zero Hermitian quark mass matrices, to include the case of `weak hierarchy' amongst them along with the usually considered `strong hierarchy' case. This has been carried out by giving wide variation to the hierarchy defining parameters D_U and D_D, having implications for the structural features of the mass matrices. We find that not only the weakly hierarchical mass matrices are able to reproduce the strongly hierarchical mixing angles but also both the phases having their origin in the mass matrices have to be non zero to achieve compatibility of these matrices with recent quark mixing data. Further noting the difference between the exclusive and inclusive values of V_ub, we have carried out separate analyses corresponding to these.

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arXiv2009

Implications of precision measurements on texture specific fermion mass matrices

Implications of texture specific mass matrices have been investigated for both quarks and neutrinos. Interestingly, for the case of quarks Fritzsch-like texture 4 zero mass matrices have been found to be compatible with the present precisely known sin2βas well as other precise CKM matrix elements. In the case of leptonic mass matrices, for both Majorana and Dirac neutrinos we find that for texture 4, 5, 6 zero mass matrices the inverted hierarchy and degenerate scenarios of neutrino masses are ruled out by the present data.

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arXiv2009

Implications of CP asymmetry parameter sin2beta on structural features of texture specific mass matrices

In the context of Fritzsch-like texture 4 zero Hermitian quark mass matrices, we have attempted to find an `exact' formula for sin2βwherein the dependence of βon the quark masses and the elements of the quark mass matrices is visible in a simple and clear manner. This has been achieved keeping in mind the strong hierarchy of the quark masses and assuming the weak hierarchy amongst the elements of the mass matrices. This `exact' formula represents a vast improvement over the leading order formula based on strong hierarchy of the elements of the mass matrices. Apart from showing the compatibility of texture 4 zero mass matrices with the present value of sin2βand other CKM parameters, we find interesting conclusions regarding the structural features of the mass matrices.

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arXiv2009

Texture specific mass matrices with Dirac neutrinos and their implications

Considering Dirac neutrinos and Fritzsch-like texture 6 zero and 5 zero mass matrices, detailed predictions for cases pertaining to normal/inverted hierarchy as well as degenerate scenario of neutrino masses have been carried out. All the cases considered here pertaining to inverted hierarchy and degenerate scenario of neutrino masses are ruled out by the existing data. For the normal hierarchy cases, the lower limit of m_nu_1 and of s_13 as well as the range of Dirac-like CP violating phase delta_l would have implications for the texture specific cases considered here.

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arXiv2008

Constructing the Leptonic Unitarity Triangle

Following analogy of the `db' triangle in the quark mixing case, we have explored the construction of the `ν_2.ν_3' leptonic unitarity triangle using the Maki-Nakagawa-Sakata matrix obtained by Bjorken {\it et al.} through generalization of the tribimaximal scenario. In particular, for the U_{e3} range 0.05-0.15, the existence of the leptonic unitarity triangle indicates a fairly good possibility of having non zero CP violation.

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arXiv2008

Texture 4 zero Fritzsch-like lepton mass matrices

For Majorana or Dirac neutrinos, using Fritzsch-like texture 4 zero mass matrices with parallel texture structures for the charged leptons and the Dirac neutrino mass matrix (M_{νD}), detailed predictions for cases pertaining to normal/inverted hierarchy as well as degenerate scenarios of neutrino masses have been carried out. The inverted hierarchy as well as degenerate scenarios seem to be ruled out at 3 σC.L. for both Majorana and Dirac neutrinos. For normal hierarchy, Jarlskog's rephasing invariant parameter J, the CP violating Dirac-like phase δand the effective neutrino mass m_{ee} have been calculated. For this case, lower limits of m_{ν_1} and θ_{13} would have implications for the nature of neutrinos.

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arXiv2006

Implications of unitarity and precision measurements on CKM matrix elements

Unitarity along with precision measurements of sin2β, V_{us} and V_{cb} allows one to find a lower bound V_{ub}\geq 0.0035 which, on using the recently measured angle αof the unitarity triangle, translates to V_{ub}= 0.0035\pm 0.0002. This precise value, stable for a good deal of changes in α, along with CP violating phase δfound from unitarity allows the construction of a `precise' CKM matrix. The above unitarity based value of V_{ub} is in agreement with the latest exclusive value used as input by UTfit, CKMfitter, HFAG, however underlines the so called `tension' faced by the latest inclusive V_{ub}=0.00449 \pm 0.00033. Further, using this inclusive value of V_{ub} along with the latest sin2β, one finds δ=23 ^{\rm o}- 39 ^{\rm o}, again in conflict with δmeasured in B-decays. The calculated ranges of the elements of the CKM matrix are in excellent agreement with those obtained recently by UTfit, CKMfitter and HFAG. Also, the ratio \frac{V_{ts}}{V_{td}} is in agreement with its latest measured value, whereas there is some disagreement between the `measured' and the calculated V_{td} values.

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arXiv2006

Constructing the CKM and PMNS matrices from mixing data

The CKM and PMNS matrices have been constructed based on the latest measurements, largely free from theoretical inputs as well as likely NP effects in the case of the former. To facilitate the construction of the CKM matrix in the PDG representation as well as in view of the comparatively large error in the measured value of the CP violating phase δ, the possibility of its construction from the tree level measured CKM elements has also been explored using the unitarity triangle. In view of the persistent difference between the |V_{ub}| exclusive and inclusive values, we have carried out separate analyses corresponding to these. The PMNS matrix has been constructed by incorporating the constraints due to solar and atmospheric neutrinos as well as by giving full variation to the Dirac-like CP violating phase δand considering different values of s_{13} having implications for different models of lepton mass matrices. Taking clue from quark mixing phenomenology, an analogous analysis of the leptonic unitarity triangle allows an estimate of the likely presence of CP violation in the leptonic sector.

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arXiv2006

Implications of Fritzsch-like lepton mass matrices

Using seesaw mechanism and Fritzsch-like texture 6 zero and 5 zero lepton Dirac mass matrices, detailed predictions for cases pertaining to normal/inverted hierarchy as well as degenerate scenario of neutrino masses have been carried out. All the cases considered here pertaining to inverted hierarchy and degenerate scenario of neutrino masses are ruled out by the existing data. For the normal hierarchy cases, the lower limit of m_{ν1} and of s_{13} as well as the range of Dirac-like CP violating phase δwould have implications for the texture 6 zero and texture 5 zero cases considered here.

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arXiv2002

Implications of texture 4 zero lepton mass matrices for U_{e3}

Lepton mass matrices similar to texture 4 zero quark mass matrices, known to be quite successful in explaining the CKM phenomenology, have been considered for finding the mixing matrix element U_{e3} (\equiv s_{13}) respecting the CHOOZ constraint, with s_{12} and Δm_{12}^2 constrained by SNP and s_{23} and Δm_{23}^2 constrained by ANP. Taking charged lepton mass matrix M_l to be diagonal, we find that the ranges of s_{13} corresponding to different SNP solutions very well include the corresponding values of s_{13} found by Akhmedov et al. by considering neutrino mass matrix M_ν with no texture zeros. Considering M_l and M_ν both to be real and non-diagonal, s_{13} ranges for the four SNP solutions come out to be: \sim 0-0.19 (LMA), 0.038-0.093 (SMA), 0.042-0.095 (LOW), 0.038-0.096 (VO) which remain of the same order when M_l and M_ν are considered to be complex and non-diagonal.

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arXiv2001

Three flavor neutrino oscillations, LSND, SNP and ANP

The recently reanalysed LSND data is investigated in the context of three flavor oscillations, with an emphasis on mass hierarchies and $s_{13}$. The resultant mass hierarchies and oscillation angles are tested with regard to "key" features of solar neutrinos and atmospheric neutrinos, e.g., "average" survival probability in the case of solar neutrinos, and zenith angle dependence and up-down asymmetry in the case of high energy atmospheric neutrinos. We find there are three distinct mass hierarchies, e.g., $Δm << ΔM, Δm < ΔM$ and $Δm \simeq ΔM$. In the first and second case, the calculated range of $s_{13}$ is in agreement with the "LMA" solution of Akhmedov {\it et al.}, the lower limit on $s_{13}$ in these cases is also in agreement with the recent analysis of Garcia {\it et al.} based on the constraints of SNP, ANP and CHOOZ, therefore, strongly supporting the neutrino oscillations observed at LSND. Further, the solutions of $s_{13}$ found in the third case correspond to the value of $s_{13}$ found by Akhmedov {\it et al.} in the case of "SMA" and "LOW" solutions. A rough estimate of the possibility of the existence of CP violation in the leptonic sector is also carried out for different possible ranges of $s_{13}$, indicating that the CP asymmetries may be measureable even in the case of LSND.

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