163 research outputs found

    Autoencoders for per-lumisection data quality monitoring at CMS

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    The monitoring of data quality is crucial both online, during the data taking, to promptly spot issues and act on them, and offline, to provide analysts with datasets that are cleaned against the occasional failures that may have crept in. Typically, data quality monitoring (DQM) is performed by \textit{shifters} who look at a set of integrated quantities, compare them with reference histograms, and, based on their experience and training, assign quality flags. Recently CMS has developed the possibility of producing DQM plots per-lumisection, where a lumisection is a time unit corresponding to about 23 s of data taking. To analyze per-lumisection data, a manual approach would be prohibitive due to the high number of lumisections, therefore an automated one would be preferable. In this work, the first use in CMS of AutoEncoders to perform anomaly detection on per-lumisection data, specifically for quantities associated with jets and missing transverse energy, is presented. The technique developed allows the detection of anomalies at the level of individual lumisections, which might be overlooked when examining integrated quantities, and serves as a proof of concept regarding the efficacy of this and similar approaches

    Search for stealth supersymmetry in final states with two photons, jets, and low missing transverse momentum in proton-proton collisions at s\sqrt{s} = 13 TeV

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    International audienceThe results of a search for stealth supersymmetry in final states with two photons and jets, targeting a phase space region with low missing transverse momentum (pTmissp_\text{T}^\text{miss}), are reported. The study is based on a sample of proton-proton collisions at s\sqrt{s} =13 TeV collected by the CMS experiment, corresponding to an integrated luminosity of 138 fb‚ąí1^{-1}. As LHC results continue to constrain the parameter space of the minimal supersymmetric standard model, the low pTmissp_\text{T}^\text{miss} regime is increasingly valuable to explore. To estimate the backgrounds due to standard model processes in such events, we apply corrections derived from simulation to an estimate based on a control selection in data. The results are interpreted in the context of simplified stealth supersymmetry models with gluino and squark pair production. The observed data are consistent with the standard model predictions, and gluino (squark) masses of up to 2150 (1850) GeV are excluded at the 95% confidence level

    Search for narrow trijet resonances in proton-proton collisions at s\sqrt{s} = 13 TeV