Search for Dark Photons Produced in 13 TeV pp Collisions

Abstract

Searches are performed for both promptlike and long-lived dark photons, A^{'}, produced in proton-proton collisions at a center-of-mass energy of 13 TeV, using A^{'}→μ^{+}μ^{-} decays and a data sample corresponding to an integrated luminosity of 1.6 fb^{-1} collected with the LHCb detector. The promptlike A^{'} search covers the mass range from near the dimuon threshold up to 70 GeV, while the long-lived A^{'} search is restricted to the low-mass region 214<m(A^{'})<350 MeV. No evidence for a signal is found, and 90% confidence level exclusion limits are placed on the γ-A^{'} kinetic-mixing strength. The constraints placed on promptlike dark photons are the most stringent to date for the mass range 10.6<m(A^{'})<70 GeV, and are comparable to the best existing limits for m(A^{'})<0.5 GeV. The search for long-lived dark photons is the first to achieve sensitivity using a displaced-vertex signature.

Exclusive displaced hadronic signatures in the LHC forward region

“…Along this work we ignore systematic uncertainties on the background or efficiencies, thus estimating our significance as simply N sig / N sig + N bg . The expected systematic uncertainties, following other similar experimental searches [13,20,21], should not significantly distort our estimated sensitivity. Fig.…”

“…LHCb advantages for LLPs include the ability to trigger on soft objects and excellent vertexing. Using Run 1 and 2 data, LHCb has performed searches looking for different types of decays of LLPs, such as muons [20], jets [13], or combinations of these [21].…”

“…The leading background in our search originates from the QCD production of bb pairs [13,20,21]. B meson decays can produce multiple charged kaons, and the invariant mass and location measurements of these kaons can fake the S signal.…”

Hunting all the hidden photons

“…Searches have been performed by ATLAS and CMS at the LHC [51], by LHCb [54,55,58], at the e + e − colliders BaBar [46,53], Belle [47,56] and KLOE [48,49,57,103].…”

Exposing the dark sector with future Z factories

“…For low mass mÃ0 ∼ OðGeVÞ, the limits from the B factory are the leading ones from measuring visible decay products of the dark photon, such as BABAR 2014 [104] having the limits of ϵ ≲ 10 −3 . Recently, the LHCb [105] performed a dark photon search using the inclusive dimuon data. This will give the leading constraints in the mass window of (10 GeV, 50 GeV).…”