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Search for Decays of Stopped Long-lived Particles Produced in Proton-proton Collisions at $\sqrt{s}

2015
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Release : 2015
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Book Synopsis Search for Decays of Stopped Long-lived Particles Produced in Proton-proton Collisions at $\sqrt{s} by :

Download or read book Search for Decays of Stopped Long-lived Particles Produced in Proton-proton Collisions at $\sqrt{s} written by . This book was released on 2015. Available in PDF, EPUB and Kindle. Book excerpt: A search has been performed for long-lived particles that could have come to rest within the CMS detector, using the time intervals between LHC beam crossings. The existence of such particles could be deduced from observation of their decays via energy deposits in the CMS calorimeter appearing at times that are well separated from any proton-proton collisions. Using a data set corresponding to an integrated luminosity of 18.6 fb-1 of 8 TeV proton-proton collisions, and a search interval corresponding to 281 h of trigger livetime, 10 events are observed, with a background prediction of 13.2+3.6 -2.5 events. Limits are presented at 95 % confidence level on gluino and top squark production, for over 13 orders of magnitude in the mean proper lifetime of the stopped particle. Assuming a cloud model of R-hadron interactions, a gluino with mass ≤1000 GeV and a top squark with mass ≤525 GeV are excluded, for lifetimes between 1 μs and 1000 s. Finally, these results are the most stringent constraints on stopped particles to date.

Search for Decays of Stopped Long-lived Particles Produced in Proton-proton Collisions at [arrow]"

2015
Download Search for Decays of Stopped Long-lived Particles Produced in Proton-proton Collisions at [arrow]

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Release : 2015
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Book Synopsis Search for Decays of Stopped Long-lived Particles Produced in Proton-proton Collisions at [arrow]" by :

Download or read book Search for Decays of Stopped Long-lived Particles Produced in Proton-proton Collisions at [arrow]" written by . This book was released on 2015. Available in PDF, EPUB and Kindle. Book excerpt:

Search for the Decays of Stopped Exotic Long-lived Particles Produced in P-P Collisions at 13 TeV at CMS

2018 Large Hadron Collider (France and Switzerland)
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Release : 2018
Genre : Large Hadron Collider (France and Switzerland)
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Book Synopsis Search for the Decays of Stopped Exotic Long-lived Particles Produced in P-P Collisions at 13 TeV at CMS by : Weifeng Ji

Download or read book Search for the Decays of Stopped Exotic Long-lived Particles Produced in P-P Collisions at 13 TeV at CMS written by Weifeng Ji. This book was released on 2018. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, I present the searches looking for decays of stopped massive long-lived exotic particles, which are pair produced in the proton-proton collisions at 13 TeV and come to rest afterwards in the CMS detector at the CERN LHC. The decays are most likely to be observed when there are no collisions. Two specific decay scenarios are studied: a long-lived particle (LLP) decaying hadronically or semi- leptonically in the calorimeter, and a LLP decaying semi-leptonically or leptonically to a pair of muons in the muon detector. The calorimeter-based search is performed using 2.7 fb-1 of 13 TeV collision run data collected in 2015 and 35.9 fb-1 of 13 TeV collision run data collected in 2016, corresponding to a total trigger livetime of 721 hours. The muon search is performed using 2.8 fb-1 of 13 TeV collision run data collected in 2015 and 36.2 fb-1 of 13 TeV collision run data collected in 2016, corresponding to a total trigger livetime of 744 hours. Search results are interpreted in a couple of simplified models. The limits on the production cross sections and masses of LLPs are calculated as a function of particle lifetimes, which vary from 100 ns to 10 days, assuming the corresponding decaying branching fractions to be 100%. The results are the most stringent ones on the stopped LLPs so far.

Search for Long-lived, Weakly Interacting Particles that Decay to Displaced Hadronic Jets in Proton-proton Collisions at √s

2016
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Release : 2016
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Book Synopsis Search for Long-lived, Weakly Interacting Particles that Decay to Displaced Hadronic Jets in Proton-proton Collisions at √s by : Preema R. Pais

Download or read book Search for Long-lived, Weakly Interacting Particles that Decay to Displaced Hadronic Jets in Proton-proton Collisions at √s written by Preema R. Pais. This book was released on 2016. Available in PDF, EPUB and Kindle. Book excerpt: Many new physics models predict the existence of neutral, weakly interacting, long-lived particles that can decay within the detector volume, producing a distinctive experimental signature. A search is performed for a pair of such particles, using proton-proton collision data at √s = 8 TeV collected by the ATLAS detector in 2012, corresponding to a total integrated luminosity of 20.3 fb-1. Novel techniques are developed for the reconstruction of displaced decays to hadronic jets in the inner tracking detector and muon spectrometer. No significant deviation is found from the number of background events expected from Standard Model processes. The data are interpreted in terms of Hidden Valley scenarios with a Z' boson mediator. This dissertation presents the first results for a heavy Z' boson decaying to displaced hadronic jets.

Search for Long-lived Particles that Decay Into Final States Containing Two Electrons Or Two Muons in Proton-proton Collisions at $\sqrt{s}

2015
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Release : 2015
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Book Synopsis Search for Long-lived Particles that Decay Into Final States Containing Two Electrons Or Two Muons in Proton-proton Collisions at $\sqrt{s} by :

Download or read book Search for Long-lived Particles that Decay Into Final States Containing Two Electrons Or Two Muons in Proton-proton Collisions at $\sqrt{s} written by . This book was released on 2015. Available in PDF, EPUB and Kindle. Book excerpt: A search is performed for long-lived particles that decay into final states that include a pair of electrons or a pair of muons. The experimental signature is a distinctive topology consisting of a pair of charged leptons originating from a displaced secondary vertex. Events corresponding to an integrated luminosity of 19.6 (20.5) fb-1 in the electron (muon) channel were collected with the CMS detector at the CERN LHC in proton-proton collisions at √s=8 TeV. No significant excess is observed above standard model expectations. Upper limits on the product of the cross section and branching fraction of such a signal are presented as a function of the long-lived particle's mean proper decay length. The limits are presented in an approximately model-independent way, allowing them to be applied to a wide class of models yielding the above topology. Over much of the investigated parameter space, the limits obtained are the most stringent to date. In the specific case of a model in which a Higgs boson in the mass range 125-1000 GeV/c2 decays into a pair of long-lived neutral bosons in the mass range 20-350 GeV/c2, each of which can then decay to dileptons, the upper limits obtained are typically in the range 0.2-10 fb for mean proper decay lengths of the long-lived particles in the range 0.01-100 cm. In the case of the lowest Higgs mass considered (125 GeV/c2), the limits are in the range 2-50 fb. As a result, these limits are sensitive to Higgs boson branching fractions as low as 10-4.

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