Search for dark photons from neutral meson decays in $p$$+$$p$ and $d$$+$Au collisions at $\sqrt{s_{{}_{NN}}}$=200 GeV

Abstract

The standard model (SM) of particle physics is spectacularly successful, yet the measured value of the muon anomalous magnetic moment $(g-2{)}_{\hat{I}}¼$ deviates from SM calculations by 3.6$\ddot{I}ƒ$. Several theoretical models attribute this to the existence of a "dark photon," an additional U(1) gauge boson, which is weakly coupled to ordinary photons. The PHENIX experiment at the Relativistic Heavy Ion Collider has searched for a dark photon, $U$, in $\ddot{I}{€}^0,\hat{I}\cdot \to {\hat{I}}^3{e}^{+}{e}^{-}$ decays and obtained upper limits of $\mathcal{O}(2\times 10^{-6})$ on $U$-${\hat{I}}^3$ mixing at 90% CL for the mass range $30<m_U<90$ MeV/$c^2$. Combined with other experimental limits, the remaining region in the $U$-${\hat{I}}^3$ mixing parameter space that can explain the $(g-2{)}_{\hat{I}}¼$ deviation from its SM value is nearly completely excluded at the 90% confidence level, with only a small region of $29<m_U<32$ MeV/$c^2$ remaining.

580 authors, 9 pages, 5 figures. v2 includes recent BABAR results w/changed title and formatted for Phys. Rev. C. v3 is version accepted for PRC Rapid Communications. Published version will be at http://www.phenix.bnl.gov/phenix/WWW/info/pp1/165 Plain text data tables will be at http://www.phenix.bnl.gov/papers.html