Searches for long-lived charged particles in pp collisions at $ \sqrt{s} $ =7 and 8 TeV

Abstract

Results of searches for heavy stable charged particles produced in pp collisions at √ s = 7 and 8 TeV are presented corresponding to an integrated luminosity of 5.0 fb −1 and 18.8 fb −1 , respectively. Data collected with the CMS detector are used to study the momentum, energy deposition, and time-of-flight of signal candidates. Leptons with an electric charge between e/3 and 8e, as well as bound states that can undergo charge exchange with the detector material, are studied. Analysis results are presented for various combinations of signatures in the inner tracker only, inner tracker and muon detector, and muon detector only. Detector signatures utilized are long time-of-flight to the outer muon system and anomalously high (or low) energy deposition in the inner tracker. The data are consistent with the expected background, and upper limits are set on the production cross section of long-lived gluinos, scalar top quarks, and scalar τ leptons, as well as pair produced long-lived leptons. Corresponding lower mass limits, ranging up to 1322 GeV/c 2 for gluinos, are the most stringent to date.

Search for stopped long-lived particles produced in pp collisions at $ \sqrt {s} = {\text{7TeV}} $

“…By repeating the analysis with increased jet energy thresholds, lower limits on the gluino mass are set up to 720 GeV, valid for E gluon > 150 GeV and lifetimes in the range 10 µs to 1000 s. These results considerably extend constraints obtained from previous stopped particle searches [12][13][14] and are consistent with the complementary exclusions provided by the direct searches [20][21][22].…”

“…This search is complementary to analyses [20][21][22] in which the long-lived particle signature is based on energy loss measurements in the charged-particle tracking system and timing information. Because this analysis relies only on calorimetry, it is sensitive to non-relativistic particles with velocity β ≤ 0.3, for which searches based on tracking information have negligible acceptance.…”

Light stau phenomenology and the Higgs γγ rate

“…However, comparing the cross sections listed in the third column of table 1 to the CMS results, we note that the CMS multilepton searches are still not sensitive to our scenario. 4 Recently CMS has also performed a search for long lived staus [94], putting stringent bounds on their mass, mτ ≥ 223 GeV. However, the most stringent constraint on the mass of a stau which decays promptly into a τ and a neutralino, is given by the LEP bound which is around (85-90) GeV when there is a large mass difference between the stau and the neutralino [44].…”

Search for multiply charged Heavy Stable Charged Particles in data collected with the CMS detector

“…Jets and/or nuclear interactions in the silicon can produce such signals. In other searches for HSCPs in the CMS collaboration, this background is reduced by applying a cluster cleaning procedure that removes wide clusters and clusters containing multiple strips saturated [50,51].…”