Low-energy lepton-proton bremsstrahlung via effective field theory

  • Pulak Talukdar
  • Fred Myhrer
  • Ghanashyam Meher
  • Udit RahaEmail author
Regular Article - Theoretical Physics


We present a systematic calculation of the cross section for the lepton-proton bremsstrahlung process \( l+p\rightarrow l^\prime +p+\gamma\) in chiral perturbation theory at next-to-leading order. This process corresponds to an undetected background signal for the proposed MUSE experiment at PSI. MUSE is designed to measure elastic scattering of low-energy electrons and muons off a proton target in order to extract a precise value of the proton’s r.m.s. radius. We show that the commonly used peaking approximation, which is used to evaluate the radiative tail for the elastic cross section, is not applicable for muon-proton scattering at the low-energy MUSE kinematics. Furthermore, we point out a certain pathology with the standard chiral power counting scheme associated with electron scattering, whereby the next-to-next-to-leading order contribution from the pion loop diagrams is kinematically enhanced and numerically of the same magnitude as the next-to-leading order corrections. We correct a misprint in a commonly cited review article.


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Copyright information

© SIF, Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  • Pulak Talukdar
    • 1
  • Fred Myhrer
    • 2
  • Ghanashyam Meher
    • 1
  • Udit Raha
    • 1
    Email author
  1. 1.Department of PhysicsIndian Institute of TechnologyGuwahatiIndia
  2. 2.Department of Physics and AstronomyUniversity of South CarolinaColumbiaUSA

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