2015/09/30 by Philip Ilten, Jesse Thaler, Mike Williams +1 · 1 citation
Physics and Astronomy · #hep-ph #hep-ex
paper · pdf · doi:10.1103/physrevd.92.115017
published as Phys. Rev. D 92, 115017 (2015) · 19 pages, 11 figures, 1 table; v2: references added
arxiv created 2015/10/08 · arxiv updated 2015/12/30
We propose a search for dark photons A′ at the LHCb experiment using the charm meson decay D^*(2007)0 → D0 A′. At nominal luminosity, D*0 → D0 γ decays will be produced at about 700kHz within the LHCb acceptance, yielding over 5 trillion such decays during Run 3 of the LHC. Replacing the photon with a kinetically-mixed dark photon, LHCb is then sensitive to dark photons that decay as A′ → e+e-. We pursue two search strategies in this paper. The displaced strategy takes advantage of the large Lorentz boost of the dark photon and the excellent vertex resolution of LHCb, yielding a nearly background-free search when the A′ decay vertex is significantly displaced from the proton-proton primary vertex. The resonant strategy takes advantage of the large event rate for D*0 → D0 A′ and the excellent invariant mass resolution of LHCb, yielding a background-limited search that nevertheless covers a significant portion of the A′ parameter space. Both search strategies rely on the planned upgrade to a triggerless-readout system at LHCb in Run 3, which will permit identification of low-momentum electron-positron pairs online during data taking. For dark photon masses below about 100MeV, LHCb can explore nearly all of the dark photon parameter space between existing prompt-A′ and beam-dump limits.