Abstract
A search is presented for long-lived charged particles that decay within the volume of the silicon tracker of the CMS experiment. Such particles can produce events with an isolated track that is missing hits in the outermost layers of the silicon tracker, and is also associated with little energy deposited in the calorimeters and no hits in the muon detectors. The search for events with this “disappearing track” signature is performed in a sample of proton-proton collisions recorded by the CMS experiment at the LHC with a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 101fb−1 recorded in 2017 and 2018. The observation of 48 events is consistent with the estimated background of 47.8−2.3+2.7(stat)±8.1(syst) events. Upper limits are set on chargino production in the context of an anomaly-mediated supersymmetry breaking model for purely wino and higgsino neutralino scenarios. At 95% confidence level, the first constraint is placed on chargino masses in the higgsino case, excluding below 750 (175) GeV for a lifetime of 3 (0.05)ns. In the wino case, the results of this search are combined with a previous CMS search to produce a result representing the complete LHC data set recorded in 2015–2018, the most stringent constraints to date. At 95% confidence level, chargino masses in the wino case are excluded below 884 (474) GeV for a lifetime of 3 (0.2)ns.
Highlights
Many beyond-the-standard-model (BSM) scenarios introduce long-lived charged particles that could decay within the volume of the tracking detectors used by the CERN LHC experiments
If the decay products of such a particle are undetected, either because they have too little momentum to be reconstructed or because they interact only weakly, a “disappearing track” signature is produced. This signature is identified as an isolated particle track that extends from the interaction region but is missing hits in the outermost region of the tracking detector, and has little associated energy deposited in the calorimeters and no associated hits in the outer muon detectors
Upper limits are set at 95% confidence level (CL) on the product of the cross section and branching fraction for each signal model
Summary
Many beyond-the-standard-model (BSM) scenarios introduce long-lived charged particles that could decay within the volume of the tracking detectors used by the CERN LHC experiments. If the decay products of such a particle are undetected, either because they have too little momentum to be reconstructed or because they interact only weakly, a “disappearing track” signature is produced. 2017 and 2018, corresponding to an integrated luminosity of 101 fb−1 The results of this search are presented in terms of chargino masses and lifetimes within the context of AMSB. The CMS experiment has excluded AMSB chargino masses for a purely wino LSP below 715 GeV for a lifetime of 3 ns [17], using the data collected during 2015 and 2016.
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