Formalism for dilepton production via virtual photon bremsstrahlung in hadronic reactions.

We derive a set of new formulas for various distributions in dilepton production via virtual photon bremsstrahlung from pseudoscalar mesons and unpolarized spin-one-half fermions. These formulas correspond to the leading and sub-leading terms in the Low–Burnett–Kroll expansion for real photon bremsstrahlung. The relation of our leading-term formulas to previous works is also shown. Existing formulas are examined in the light of Lorentz covariance and gauge invariance. Numerical comparison is made in a simple example, where an “exact” formula and real photon data exist. The results reveal large discrepancies among different bremsstrahlung formulas. Of all the leading-term bremsstrahlung formulas, the one derived in this work agrees best with the exact formula. The issues of MT -scaling and event generators are also addressed. PACS number(s): 13.40.-f, 12.20.Ds Typeset using REVTEX ∗On leave of absence from the Department of Theoretical Physics, Faculty of Mathematics and Physics, Comenius University, SK 842-15 Bratislava, Slovakia.