engleski

Search for dark photons from neutral meson decays in p+p and d+Au collisions at sqrt(s_NN)=200 GeV

The standard model (SM) of particle physics is spectacularly successful, yet the measured value of the muon anomalous magnetic moment (g−2) μ deviates from SM calculations by 3.6σ. 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 π0, η→γe+e− decays and obtained upper limits of O(2×10−6) on U−γ mixing at 90% C.L. for the mass range 30<mU<90 MeV/c2. Combined with other experimental limits, the remaining region in the U−γ mixing parameter space that can explain the (g−2)μ deviation from its SM value is nearly completely excluded at the 90% confidence level, with only a small region of 29<mU<32 MeV/c2 remaining.

Dark photon ; PHENIX

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