New exclusion limits on dark gauge forces from proton Bremsstrahlung in beam-dump data

We re-analyze published proton beam dump data taken at the U70 accelerator at IHEP Serpukhov with the nu-calorimeter I experiment in 1989 to set mass-coupling limits for dark gauge forces. The corresponding data have been used for axion and light Higgs particle searches in Refs. [1,2] before. More recently, limits on dark gauge forces have been derived from this data set, considering a dark photon production from pi(0) decay[3]. Here we determine extended mass and coupling exclusion bounds for dark gauge bosons ranging to masses m(gamma 1). 624 MeV at admixture parameters epsilon similar or equal to 10(-6) considering high-energy Bremsstrahlung of the gamma(1)-boson off the initial proton beam and different detection mechanisms. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license