  A low-energy model is built to study systems such as Dirac/Weyl semimetals,
according to statistical quantum electrodynamics formalism. We report that the
introduction of a pseudoscalar, associated to longitudinal photons propagating
along a magnetic field B, could transforms a Dirac semimetal into a Weyl
semimetal with a pair of Weyl nodes for each point of Dirac. The nodes are
separated by a pseudovector electric field induced dynamically along B
associated to a chiral effect on the Fermi surface. A topological quantum
transition is produced between a chiral-and non chiral symmetry phase. A
general expression to the longitudinal magnetoconductivity is found. It
provides the possibility of generalizing the usual expressions of the
magnetoconductivity reported in the literature. This has a quadratic dependence
on B, which is associated with a positive contribution to the
magnetoconductivity. This is a prominent signature of the chiral magnetic
effect in Dirac/Weyl systems in parallel electric and magnetic fields. We
report a chiral effect induced by longitudinal photons associated to a negative
longitudinal magnetoresistance in Dirac systems via an axial anomaly relation.
We show some numerical results, and reproduced with a high level of accuracy
some of the experimental results, in the low temperature region, obtained to
the magnetoresistance of ZrTe5 and Na3Bi. We believe that a wide variety of
these semimetals can be studied by using our general expression to the negative
longitudinal magnetoresistance.
