Updated search for long-lived particles decaying to jet pairs

Abstract

A search is presented for long-lived particles with a mass between 25 and 50 GeV/c 2 and a lifetime between 2 and 500 ps, using proton-proton collision data corresponding to an integrated luminosity of 2.0 fb −1 , collected by the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The particles are assumed to be pair-produced in the decay of a 125 GeV/c 2 Standard-Model-like Higgs boson. The experimental signature is a single long-lived particle, identified by a displaced vertex with two associated jets. No excess above background is observed and limits are set on the production cross-section as a function of the mass and lifetime of the long-lived particle.

The experimental status of direct searches for exotic physics beyond the standard model at the Large Hadron Collider

“…In these cases, the LSP will often be sufficiently long-lived to decay centimeters or meters away from the LHC collisions. The methodologies for detection can range from detection of particles that decay within the tracker volume, possibly with other distinguishing features like p T / [76,77,181], those that contain extensive ionizing radiation in the tracker [182], particles that decay into hadronizing particles far from the interaction region ("emerging" jets) [183], particles that get trapped in the nuclear material and subsequently decay [78], particles that decay to unobservable particles in flight ("disappearing" tracks") [184], and others not discussed here.…”

Freeze-in and freeze-out of dark matter with charged long-lived partners

“…Signatures typically include (i) Displaced Vertex, where the LLP decay within the detector, but away from the interaction point; (ii) Heavy Stable Charged Particle (HSCP) tracks, where charged LLP decaying outside the detector, leaving charged tracks similar to that of the muon, but with distinct features arising from slower speed and larger energy deposition along its flight through the materials of the detector or (iii) Disappearing Tracks, where an isolated track stopping before hitting the outer layers of the silicon tracker and without any associated energy deposition in the calorimeters or muon chamber. Experimental searches by CMS [48][49][50], ATLAS [54,[57][58][59] and LHCb [61][62][63] considered long-lived neutral scalar decaying in the calorimeter into pair of jets, looking for displaced vertex with negative results leading to constraints on the masses of the corresponding LLP. Considering a gauge-mediated supersymmetry breaking scenario, CMS [52] considered non-prompt jets arising from the decay of gluino to gluons and gravitinos, where the gluon jet emerges from a displaced vertex within the tracker.…”

Detector-size upper bounds on dark hadron lifetime from cosmology

“…With a low p T triggering requirement and excellent particle identification ability, the LHCb detector is good at looking for light and soft LLPs [19]. The tracking information from the VELO detector is essential to reconstruct the decay location and veto hadronic backgrounds, and this is why most LHCb LLP searches have their best sensitivity for a O(1) cm scale decay length [28,53,54]. Having inner detector information in ATLAS/CMS searches helps to reconstruct displaced decay signals [30,31,[55][56][57][58].…”

“…Existing searches from the LHCb, ATLAS, and CMS collaborations have already set useful constrains on dark hadron production, see e.g. [27] for a review of the previous searches, and [28][29][30][31] for some recent results.…”