Search for massive long-lived particles decaying semileptonically in the LHCb detector

Abstract

A search is presented for massive long-lived particles decaying into a muon and two quarks. The dataset consists of proton-proton interactions at centre-of-mass energies of 7 and 8 TeV, corresponding to integrated luminosities of 1 and 2, respectively. The analysis is performed assuming a set of production mechanisms with simple topologies, including the production of a Higgs-like particle decaying into two long-lived particles. The mass range from 20 to 80 and lifetimes from 5 to 100 are explored. Results are also interpreted in terms of neutralino production in different R-Parity violating supersymmetric models, with masses in the 23–198 GeV/ range. No excess above the background expectation is observed and upper limits are set on the production cross-section for various points in the parameter space of theoretical models.

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.…”

“…LHCb has currently an excellent material map, produced using secondary hadronic interactions [37] that allows to keep this background under superb control. Furthermore, as mentioned below, we will conservatively veto the vertices in the region of VELO with transverse distance to the beam-line ρ between 10 − 14 mm following [21], since this is the region where material interactions are more abundant. It should be remarked that this corresponds to a very simplified description of the LHCb VELO material, and excellent discrimination can be obtained by simply using the map described above.…”

Updated search for long-lived particles decaying to jet pairs

“…Compared to these analyses, this search is sensitive to π v particles with relatively low mass and lifetime. The LHCb collaboration has also performed a search for events with two displaced high-multiplicity vertices [16] and a search for events with a lepton from a highmultiplicity displaced vertex [17] in the context of SUSY models, and several searches for so far unknown long-lived particles in B-meson decays [18][19][20][21].…”