Browsing by Author "Wijewardhana, L. C. R."

Now showing 1 - 9 of 9
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    ACD estimation of the S-parameter revisited
    Ignjatovic, S. R.; Takeuchi, Tatsu; Wijewardhana, L. C. R. (Elsevier, 1997-05-29)
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    An evaluation of the analytic continuation by duality technique
    Takeuchi, Tatsu; Goonetileke, L. C.; Ignjatovic, S. R.; Wijewardhana, L. C. R. (1997)
    In Nucl. Phys. B391 (1993) 127, the value of the oblique correction parameter S for walking technicolor theories was estimated using a technique called Analytic Continuation by Duality (ACD). We apply the ACD technique to the perturbative vacuum polarization function and find that it fails to reproduce the well known result S=1/6\pi. This brings into question the reliability of the ACD technique and the ACD estimate of S.
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    NuTeV anomaly, lepton universality, and nonuniversal neutrino-gauge couplings
    Loinaz, William; Okamura, Naotoshi; Rayyan, S.; Takeuchi, Tatsu; Wijewardhana, L. C. R. (American Physical Society, 2004-12)
    In previous studies we found that models with flavor-universal suppression of the neutrino-gauge couplings are compatible with NuTeV and Z-pole data. In this paper we expand our analysis to obtain constraints on flavor-dependent coupling suppression by including lepton universality data from W, tau, pi and K decays in fits to model parameters. We find that the data are consistent with a variety of patterns of coupling suppression. In particular, in scenarios in which the suppression arises from the mixing of light neutrinos with heavy gauge singlet states (neutrissimos), we find patterns of flavor-dependent coupling suppression which are also consistent with constraints from mu-->egamma.
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    NuTeV anomaly, lepton universality, and nonuniversal neutrino-gauge couplings
    Loinaz, William; Okamura, Naotoshi; Rayyan, S.; Takeuchi, Tatsu; Wijewardhana, L. C. R. (American Physical Society, 2004-12-01)
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    NuTeV anomaly, neutrino mixing, and a heavy Higgs boson
    Loinaz, William; Okamura, Naotoshi; Takeuchi, Tatsu; Wijewardhana, L. C. R. (American Physical Society, 2003-04-01)
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    NuTeV anomaly, neutrino mixing, and a heavy Higgs boson
    Loinaz, William; Okamura, Naotoshi; Takeuchi, Tatsu; Wijewardhana, L. C. R. (American Physical Society, 2003-04)
    Recent results from the NuTeV experiment at Fermilab and the deviation of the Z invisible width, measured at CERN LEP and the SLAC Linear Collider, from its standard model (SM) prediction suggest the suppression of neutrino-Z couplings. Such suppressions occur naturally in models which mix the neutrinos with heavy gauge singlet states. We postulate a universal suppression of the Znunu couplings by a factor of (1-epsilon) and perform a fit to the Z-pole and NuTeV observables with epsilon and the oblique correction parameters S and T. Compared to a fit with S and T only, the inclusion of epsilon leads to a dramatic improvement in the quality of the fit. The values of S and T preferred by the fit can be obtained within the SM by a simple increase in the Higgs boson mass. However, if the W mass is also included in the fit, a non-zero U parameter becomes necessary which cannot be supplied within the SM. The preferred value of epsilon suggests that the seesaw mechanism may not be the reason why neutrinos are so light.
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    Quark-lepton unification and lepton flavor nonconservation from a TeV-scale seesaw neutrino mass texture
    Loinaz, William; Okamura, Naotoshi; Rayyan, S.; Takeuchi, Tatsu; Wijewardhana, L. C. R. (American Physical Society, 2003-10-01)
    In a recent paper we pointed out that the mixing of the light neutrinos with heavy gauge singlet states could reconcile the Z-pole data from e(+)e(-) colliders and the nu(mu) ((nu) over bar (mu)) scattering data from the NuTeV experiment at Fermilab. We further noted that the mixing angle required to fit the data is much larger than what would be expected from the conventional seesaw mechanism. In this paper, we show how such mixings can be arranged by a judicious choice of the neutrino mass texture. We also argue that by invoking the unification of the Dirac mass matrix for the up-type quarks and the neutrinos, the mass of the heavy states can naturally be expected to lie in the few TeV range. The model is strongly constrained by the lepton flavor changing process mu-->egamma which requires lepton universality to be violated in the charged channel.
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    Quark-lepton unification and lepton flavor nonconservation from a TeV-scale seesaw neutrino mass texture
    Loinaz, William; Okamura, Naotoshi; Rayyan, S.; Takeuchi, Tatsu; Wijewardhana, L. C. R. (American Physical Society, 2003-10-01)
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    The W mass and the U parameter
    Takeuchi, Tatsu; Loinaz, William; Okamura, Naotoshi; Wijewardhana, L. C. R. (2003)