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Title: Electric dipole and magnetic quadrupole moments of the W boson via a CP-violating HWW vertex in effective Lagrangians

Abstract

The possibility of nonnegligible W electric dipole ({mu}-tilde{sub W}) and magnetic quadrupole (Q-tilde{sub W}) moments induced by the most general HWW vertex is examined via the effective Lagrangian technique. It is assumed that new heavy fermions induce an anomalous CP-odd component of the HWW vertex, which can be parametrized by an SU{sub L}(2)xU{sub Y}(1)-invariant dimension-six operator. This anomalous contribution, when combined with the standard model CP-even contribution, leads to CP-odd electromagnetic properties of the W boson, which are characterized by the form factors {delta}{kappa}-tilde and {delta}Q-tilde. It is found that {delta}{kappa}-tilde is divergent, whereas {delta}Q-tilde is finite, which reflects the fact that the latter cannot be generated at the one-loop level in any renormalizable theory. Assuming reasonable values for the unknown parameters, we found that {mu}-tilde{sub W}{approx}3-6x10{sup -21} e{center_dot}cm, which is 8 orders of magnitude larger than the SM prediction and close to the upper bound derived from the neutron electric dipole moment. The estimated size of the somewhat less-studied Q-tilde{sub W} moment is of the order of -10{sup -36} e{center_dot}cm{sup 2}, which is 15 orders of magnitude above the SM contribution.

Authors:
; ; ;  [1];  [2];  [2]
  1. Departamento de Matematicas y Fisica, Universidad Autonoma de Aguascalientes, Avenida Universidad 940, C.P. 20100, Aguascalientes, Aguascalientes (Mexico)
  2. (Mexico)
Publication Date:
OSTI Identifier:
20774463
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 72; Journal Issue: 11; Other Information: DOI: 10.1103/PhysRevD.72.115009; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; CP INVARIANCE; ELECTRIC DIPOLE MOMENTS; ELECTRIC DIPOLES; ELECTROMAGNETIC FORM FACTORS; LAGRANGIAN FIELD THEORY; LAGRANGIAN FUNCTION; MAGNETIC MOMENTS; NEUTRONS; QUADRUPOLE MOMENTS; QUADRUPOLES; RENORMALIZATION; STANDARD MODEL; SU-2 GROUPS; U-1 GROUPS; UNITARY SYMMETRY; W MINUS BOSONS; W PLUS BOSONS

Citation Formats

Montano, J., Ramirez-Zavaleta, F., Tavares-Velasco, G., Toscano, J.J., Departamento de Fisica, CINVESTAV, Apartado Postal 14-740, 07000, Mexico, D.F., and Facultad de Ciencias Fisico Matematicas, Benemerita Universidad Autonoma de Puebla, Apartado Postal 1152, Puebla, Puebla. Electric dipole and magnetic quadrupole moments of the W boson via a CP-violating HWW vertex in effective Lagrangians. United States: N. p., 2005. Web. doi:10.1103/PhysRevD.72.115009.
Montano, J., Ramirez-Zavaleta, F., Tavares-Velasco, G., Toscano, J.J., Departamento de Fisica, CINVESTAV, Apartado Postal 14-740, 07000, Mexico, D.F., & Facultad de Ciencias Fisico Matematicas, Benemerita Universidad Autonoma de Puebla, Apartado Postal 1152, Puebla, Puebla. Electric dipole and magnetic quadrupole moments of the W boson via a CP-violating HWW vertex in effective Lagrangians. United States. doi:10.1103/PhysRevD.72.115009.
Montano, J., Ramirez-Zavaleta, F., Tavares-Velasco, G., Toscano, J.J., Departamento de Fisica, CINVESTAV, Apartado Postal 14-740, 07000, Mexico, D.F., and Facultad de Ciencias Fisico Matematicas, Benemerita Universidad Autonoma de Puebla, Apartado Postal 1152, Puebla, Puebla. Thu . "Electric dipole and magnetic quadrupole moments of the W boson via a CP-violating HWW vertex in effective Lagrangians". United States. doi:10.1103/PhysRevD.72.115009.
@article{osti_20774463,
title = {Electric dipole and magnetic quadrupole moments of the W boson via a CP-violating HWW vertex in effective Lagrangians},
author = {Montano, J. and Ramirez-Zavaleta, F. and Tavares-Velasco, G. and Toscano, J.J. and Departamento de Fisica, CINVESTAV, Apartado Postal 14-740, 07000, Mexico, D.F. and Facultad de Ciencias Fisico Matematicas, Benemerita Universidad Autonoma de Puebla, Apartado Postal 1152, Puebla, Puebla},
abstractNote = {The possibility of nonnegligible W electric dipole ({mu}-tilde{sub W}) and magnetic quadrupole (Q-tilde{sub W}) moments induced by the most general HWW vertex is examined via the effective Lagrangian technique. It is assumed that new heavy fermions induce an anomalous CP-odd component of the HWW vertex, which can be parametrized by an SU{sub L}(2)xU{sub Y}(1)-invariant dimension-six operator. This anomalous contribution, when combined with the standard model CP-even contribution, leads to CP-odd electromagnetic properties of the W boson, which are characterized by the form factors {delta}{kappa}-tilde and {delta}Q-tilde. It is found that {delta}{kappa}-tilde is divergent, whereas {delta}Q-tilde is finite, which reflects the fact that the latter cannot be generated at the one-loop level in any renormalizable theory. Assuming reasonable values for the unknown parameters, we found that {mu}-tilde{sub W}{approx}3-6x10{sup -21} e{center_dot}cm, which is 8 orders of magnitude larger than the SM prediction and close to the upper bound derived from the neutron electric dipole moment. The estimated size of the somewhat less-studied Q-tilde{sub W} moment is of the order of -10{sup -36} e{center_dot}cm{sup 2}, which is 15 orders of magnitude above the SM contribution.},
doi = {10.1103/PhysRevD.72.115009},
journal = {Physical Review. D, Particles Fields},
number = 11,
volume = 72,
place = {United States},
year = {Thu Dec 01 00:00:00 EST 2005},
month = {Thu Dec 01 00:00:00 EST 2005}
}
  • The one-loop contribution of the two CP-violating components of the WW{gamma} vertex, {kappa}-tilde{sub {gamma}}W{sub {mu}}{sup +}W{sub {nu}}{sup -}F-tilde{sup {mu}}{sup {nu}} and ({lambda}-tilde{sub {gamma}}/m{sub W}{sup 2})W{sub {mu}}{sub {nu}}{sup +}W{sub {rho}}{sup -{nu}}F-tilde{sup {rho}}{sup {mu}}, on the electric dipole moment (EDM) of fermions is calculated using dimensional regularization and its impact at low energies reexamined in the light of the decoupling theorem. The Ward identities satisfied by these couplings are derived by adopting a SU{sub L}(2)xU{sub Y}(1)-invariant approach and their implications in radiative corrections discussed. Previous results on {kappa}-tilde{sub {gamma}}, whose bound is updated to |{kappa}-tilde{sub {gamma}}|<5.2x10{sup -5}, are reproduced, but disagreement withmore » those existing for {lambda}-tilde{sub {gamma}} is found. In particular, the upper bound |{lambda}-tilde{sub {gamma}}|<1.9x10{sup -2} is found from the limit on the neutron EDM, which is more than 2 orders of magnitude less stringent than that of previous results. It is argued that this difference between the {kappa}-tilde{sub {gamma}} and {lambda}-tilde{sub {gamma}} bounds is the one that might be expected in accordance with the decoupling theorem. This argument is reinforced by analyzing carefully the low-energy behavior of the loop functions. The upper bounds on the W EDM, |d{sub W}|<6.2x10{sup -21} e{center_dot}cm, and the magnetic quadrupole moment, |Q-tilde{sub W}|<3x10{sup -36} e{center_dot}cm{sup 2}, are derived. The EDM of the second and third families of quarks and charged leptons are estimated. In particular, EDM as large as 10{sup -20} e{center_dot}cm and 10{sup -21} e{center_dot}cm are found for the t and b quarks, respectively.« less
  • W{sup {plus_minus}}H{sup {minus_plus}}Z{sub i} (i=1,2) vertices available exclusively in the extra U(1) superstring-inspired model have been utilized to evaluate the W-W-{gamma} vertex contribution at the one loop level. The expressions so obtained have been used to estimate the anomalous magnetic dipole moment ({Delta}k{sub WZ{sub i}H}) and electric quadrupole moment ({Delta}Q{sub WZ{sub i}H}) of the W{sup +} boson. The contribution of the Z{sub 2}WW vertex is also added to these values. The resulting values in the unit of ({minus}{alpha}/{pi}) when the Z{sub 2} mass varies from 555 to 620 GeV have the following ranges: for m{sub t(CDF)}=175.6GeV, {Delta}k{sub [U(1)]}, from 25.402more » to 41.559, {Delta}Q{sub [U(1)]}, from 6.886 to 10.858; for m{sub t(D0)}=169GeV, {Delta}k{sub [U(1)]}, from 20.821 to 34.121, {Delta}Q{sub [U(1)]}, from 5.738 to 9.033. These are larger than the standard model radiative correction contributions but an order of magnitude smaller than those predicted by the composite model of Abbott and Farhi.« less
  • The magnetic dipole moment of the {ital W} boson is given by {mu}={ital e}(1+{kappa}+{lambda})/2{ital M}{sub {ital W}} and its electric quadrupole moment is given by {ital Q}={minus}{ital e}({kappa}{minus}{lambda})/{ital M}{sub {ital W}}{sup 2}. A nonstandard magnetic dipole moment and a nonstandard electric quadrupole moment lead to different differential decay distributions in the radiative decays of {ital W}{sup {plus minus}}, {ital W}{sup {minus}}{r arrow}{ital e}{bar {nu}}{gamma} and {ital W}{sup {minus}}{r arrow}{ital d{bar u}}{gamma}. While hard photons are characteristic signatures of {kappa}{ne}1 there is no such explicit signal for {lambda}{ne}0. We present a technique for the determination of the values of {kappa} andmore » {lambda} by measuring the total number of events in two regions of phase space. This experiment could be done at the CERN {ital e}{sup +}{ital e{minus}} collider LEP II, where a clean source of {ital W} bosons will be available.« less
  • The magnetic dipole moment and the electric dipole moment of leptons are calculated under the assumption of lepton flavor violation (LFV) induced by spin-1 unparticles with both vector and axial-vector couplings to leptons, including a CP-violating phase. The experimental limits on the muon magnetic dipole moment and LFV process, such as the decay l{sub i}{sup -}{yields}l{sub j}{sup -}l{sub k}{sup -}l{sub k}{sup +}, are then used to constrain the LFV couplings for particular values of the unparticle operator dimension d{sub U} and the unparticle scale {Lambda}{sub U}, assuming that LFV transitions between the tau and muon leptons are dominant. It ismore » found that the current experimental constraints favor a scenario with dominance of the vector couplings over the axial-vector couplings. We also obtain estimates for the electric dipole moments of the electron and the muon, which are well below the experimental values.« less