Testing WWγ vertex in radiative muon decay

Karan, Anirban (The Institute of Mathematical Sciences, Taramani, Chennai 600113, India and Homi Bhabha National Institute, BARC Training School Complex, Anushaktinagar, Mumbai 400094, India) ; Sinha, Rahul (The Institute of Mathematical Sciences, Taramani, Chennai 600113, India and Homi Bhabha National Institute, BARC Training School Complex, Anushaktinagar, Mumbai 400094, India) ; Mandal, Rusa (IFIC, Universitat de València-CSIC, Apartat de Correus 22085, E-46071 València, Spain)

12 February 2019

Abstract: Large numbers of muons will be produced at facilities developed to probe the lepton-flavor-violating process μeγ. We show that by constructing a suitable asymmetry, radiative muon decay μeγνμν¯e can also be used to test the WWγ vertex at such facilities. The process has two missing neutrinos in the final state, and upon integrating their momenta the partial differential decay rate shows no radiation-amplitude zero. However, we establish that an easily separable part of the normalized differential decay rate that is odd under the exchange of photon and electron energies does have a zero in the case of the standard model (SM). This new type of zero has hitherto not been studied in the literature. A suitably constructed asymmetry using this fact enables a sensitive probe for the WWγ vertex beyond the SM. With a simplistic analysis, we find that the C- and P-conserving dimension-four WWγ vertex can be probed at O(102) with a satisfactory significance level.


Published in: Physical Review D 99 (2019)
Published by: APS
DOI: 10.1103/PhysRevD.99.033006
arXiv: 1810.07992
License: CC-BY-4.0



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