Abstract
A search is performed for long-lived massive neutral particles decaying to quark-antiquark pairs. The experimental signature is a distinctive topology of a pair of jets, originating at a secondary vertex. Events were collected with the CMS detector at the CERN LHC in proton-proton collisions at a centre-of-mass energy of 8 TeV. The data analyzed correspond to an integrated luminosity of 18.5 inverse femtobarns. No significant excess is observed above standard model expectations. Upper limits at 95% confidence level are set on the production cross section of a heavy neutral scalar particle, H, in the mass range of 200 to 1000 GeV, decaying promptly into a pair of long-lived neutral X particles in the mass range of 50 to 350 GeV, each in turn decaying into a quark-antiquark pair. For X with mean proper decay lengths of 0.4 to 200 cm, the upper limits are typically 0.5-200 fb. The results are also interpreted in the context of an R-parity-violating supersymmetric model with long-lived neutralinos decaying into a quark-antiquark pair and a muon. For pair production of squarks that promptly decay to neutralinos with mean proper decay lengths of 2-40 cm, the upper limits on the cross section are typically 0.5-3 fb. The above limits are the most stringent on these channels to date.
Highlights
This paper presents a search for massive, long-lived exotic particles, decaying into quark-antiquark pairs, using data collected with the CMS detector at the CERN LHC
A number of theories of new physics beyond the standard model predict the existence of massive, long-lived particles, which could manifest themselves through nonprompt decays to jets
For jets originating at a location that is significantly displaced from the event primary vertex, the reduced track reconstruction efficiency and an inclined approach angle at the calorimeter face result in a systematic underestimation of the jet momentum by up to 10%, as determined from simulation
Summary
This paper presents a search for massive, long-lived exotic particles, decaying into quark-antiquark pairs (qq ), using data collected with the CMS detector at the CERN LHC. We search for events containing a pair of jets originating from a common secondary vertex that lies within the volume of the CMS tracker and is significantly displaced from the colliding beams. This topological signature has the potential to provide clear evidence for physics beyond the standard model (SM). Previous searches by the CMS collaboration for long-lived particles utilized high-ionization signals, large time-of-flight measurements, nonpointing photons or leptons, and decays inside the CMS hadron calorimeter [10,11,12,13]
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