Enhanced long-lived dark photon signals at the LHC

Abstract

We construct a model in which the standard model is extended by a hidden sector with two gauge U(1) bosons. A Dirac fermion ψ charged under both U(1) fields is introduced in the hidden sector which can be a subcomponent of the dark matter in the Universe. Stueckelberg mass terms between the two new gauge U(1) fields and the hypercharge gauge boson mediate the interactions between the standard model sector and the hidden sector. A remarkable collider signature of this model is the enhanced long-lived dark photon events at the LHC than the conventional dark photon models; the long-lived dark photons in the model can be discriminated from the background by measuring the time delay signal in the precision timing detectors which are proposed to be installed in the LHC upgrades and have an O(10) pico-second detection efficiency. Searches with current LHCb data are also investigated. Various experimental constraints on the model including collider constraints and cosmological constraints are also discussed.

Unleashing the full power of LHCb to probe Stealth New Physics

“…However, LHC searches for such LLDPs suffer from the fact that the same coupling that makes the dark photon long-lived suppresses the production rate. Here we present a model where the LHC production rate can be decoupled from the decay process, with interesting prospects at LHCb [238].…”

“…The standard model is extended by a hidden sector that contains two abelian gauge bosons X µ and C µ , with gauge groups U (1) F and U (1) W respectively, and one Dirac fermion ψ charged under both groups with gauge couplings g F and g W . The interactions between the hidden sector and the standard model are mediated by the Stueckelberg mass terms [238]; the relevant Lagrangian is given by…”

“…Furthermore, if the produced LLDP is moving non-relativistically and has a long lifetime, a significant time delay ∆t [243] can be measured by the precision timing detectors proposed to be installed at LHCb [21], CMS [242] and ATLAS [244,245]. A time delay signal from the LLDPs model [238] has been investigated using the future timing detector at CMS (MTD CMS) which has a ∼30 ps timing resolution [242]. The major background due to pile-up can be suppressed to be negligible if a significant time delay is required, ∆t > 1.2 ns.…”

Time-delayed electrons from neutral currents at the LHC

“…We follow closely refs. [29,34,35] for pinning down the search strategy, which consists of a few event selections. We start with a requirement on the transverse momentum and pseudorapidity of the leading electron in the event: p e T > 20 GeV and |η e | < 2.5.…”

“…Following that, refs. [34,35] investigated respectively long-lived dark photons in a model with two extra U(1) gauge bosons, and HNLs from the SM Higgs decays in an effective model. In particular, the results from the latter can be re-interpreted in terms of the U(1) B−L model which is considered here.…”