Axially asymmetric fermion scattering off electroweak phase transition bubble walls with hypermagnetic fields

We show that in the presence of large scale primordial hypermagnetic fields it is possible to generate an axial asymmetry for a first order electroweak phase transition. This happens during the reflection and transmission of fermions off the true vacuum bubbles, due to the chiral nature of the fermion coupling with the background field in the symmetric phase. We derive and solve the Dirac equation for such fermions and compute the reflection and transmission coefficients for the case when these fermions move from the symmetric to the symmetry broken phase. We also comment on the possible implications of such axial charge segregation processes for baryon number generation.