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Seesaw Neutrino mass and extra U(1) symmetry

Seesaw Neutrino mass and extra U(1) symmetry. Rathin Adhikari Centre for Theoretical Physics Jamia Millia Islamia Central University New Delhi-110025. Based on : Phys. Lett. B672:136-140,2009 e-Print : arXiv:0810.5547 [hep-ph] R. Adhikari, J. Erler and E. Ma. NuGoa09.

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Seesaw Neutrino mass and extra U(1) symmetry

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  1. Seesaw Neutrino mass and extra U(1) symmetry Rathin Adhikari Centre for Theoretical Physics Jamia Millia Islamia Central University New Delhi-110025 Based on : Phys. Lett. B672:136-140,2009 e-Print: arXiv:0810.5547 [hep-ph] R. Adhikari, J. Erler and E. Ma NuGoa09

  2. Effective Dimension five operator which generates neutrino mass : S. Weinberg, Phys. Rev. Lett, 43, 1566 (1979) There are three tree level realization :E. Ma, Phys. Rev. Lett, 81, 1171 (1998) Type I Type II Type III Replacing in (Type I) by heavy Majorana fermion triplet

  3. Extra U(1) gauge symmetry Consider fermion of Standard Model plus and under new gauge symmetry are required to generate masses to leptons and quarks. However some of them may be same depending on anomaly-free solutions Ref: E. Ma, Mod Phys Lett A17, 535 (2002); E. Ma & D. P. Roy, Nucl. Phys B644,290 (2002); S.M. Barr & I. Dorsner, Phys. Rev.D 72,015011 (2005)

  4. (Considering three families of quarks and leptons and ) Conditions for absence of axial vector anomaly : (1) (2) (3) (4) (5) Ref: Adler, Phys. Rev 177, 2426 (1969); Bell & Jackiw, Nuovo Cemento, A60, 47 (1969); Bardeen, Phys Rev, 184,1848 (1969) Condition for absence of mixed gravitational-gauge anomaly : (6) Ref: Delbourgo & Salam, PLB 40, 381 (1972); Eguchi & Freund, PRL, 37, 1251 (1976); Alvarez-Gaume & Witten NPB, 234,269 (1984)

  5. From (1) , (3) & (4) (which are independent of )two solutions: Solution(I): For , (2) implies No new gauge symmetry From (5) & (6) Gauge symmetry and are possible. Here Type I Seesaw Solution (II) : From (5) & (6) one solution is (a) Type III Seesaw

  6. Another solution (b) Type I & III Seesaw However, in this case to cancel anomalies additional singlets are to be considered. Four possible models in this case:

  7. Radiative neutrino masses are possible here

  8. Model B Model C

  9. X gauge boson mixes with Z boson For zero mass mixing which requires for

  10. If X gauge boson is observed at LHC , then r may be determined from its decay branching fraction :

  11. One loop radiative contribution to neutrino mass In Model C the 3X3 Majorana neutrino mass matrix receives tree level contribution from the coupling of to a linear combination of through as well as radiative contribution from and . This is a natural hierarchical scenario.

  12. Lightest particle of odd is dark matter candidate. It may be a scalar boson - the lighter of and Conclusion : (1) In the context of U(1) extension of the Standard Model we have discussed consequences of having one or more Majorana fermion triplets generating neutrino mass through Seesaw mechanism. (2) Associated neutral gauge boson has prescribed couplings to the usual quarks and leptons in terms of and The exclusion limit of from low energy data has been obtained showing that may be accessible to LHC if is of the order of

  13. (3) In case of one triplet (Model B) one Higgs doublet couples to quark and the other to leptons; in case of two triplet (Model C) there is third scalar doublet which allows natural implementation of radiative neutrino mass and dark matter. Thank You

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