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,hbox {fb}^{-1}, 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 mathrm{{GeV}}/c^2 and lifetimes from 5 to 100{,mathrm{{ps}}} 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/c^2 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.

Highlights

  • Supersymmetry (SUSY) is one of the most popular extensions of the Standard Model, which solves the hierarchy problem, can unify the gauge couplings and could provide dark matter candidates

  • The present study focuses on a subset of models featuring massive long-lived particles (LLP)

  • The muon isolation value and the reconstructed mass of the long-lived particles are not used in the multi-layer perceptron (MLP) classifier; the discrimination power of these two variables is subsequently exploited for the signal determination

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Summary

Introduction

Supersymmetry (SUSY) is one of the most popular extensions of the Standard Model, which solves the hierarchy problem, can unify the gauge couplings and could provide dark matter candidates. The minimal supersymmetric standard model (MSSM) is the simplest phenomenologically viable realization of SUSY [1,2]. The present study focuses on a subset of models featuring massive long-lived particles (LLP). LLP searches have been performed by Tevatron and LHC experiments [5,6,7,8,9,10,11], often using the Hidden Valley framework [4] as a benchmark model The LHCb detector probes the forward rapidity region which is only partially covered by the other LHC experiments, and triggers on particles with low transverse momenta, which allows the experiment to explore relatively small LLP masses

Detector description
Event generation and detector simulation
Event selection
Determination of the signal yield
Detection efficiency and systematic uncertainties
Results
TeV dataset Expected Observed
Conclusion
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