Download or read book Search for Decays of Stopped Long lived Particles Produced in Proton proton Collisions at arrow written by and published by . This book was released on 2015 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Search for Decays of Stopped Long lived Particles Produced in Proton proton Collisions at sqrt s written by and published by . This book was released on 2015 with total page 33 pages. 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.
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 and published by . This book was released on 2018 with total page 112 pages. 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.
Download or read book Search for Long lived Weakly Interacting Particles that Decay to Displaced Hadronic Jets in Proton proton Collisions at arrow written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for the decay of neutral, weakly interacting, long-lived particles using data collected by the ATLAS detector at the LHC is presented. This analysis uses the full data set recorded in 2012: 20.3 fb-1 of proton-proton collision data at [arrow]" = 8 TeV. The search employs techniques for reconstructing decay vertices of long-lived particles decaying to jets in the inner tracking detector and muon spectrometer. Signal events require at least two reconstructed vertices. No significant excess of events over the expected background is found, and limits as a function of proper lifetime are reported for the decay of the Higgs boson and other scalar bosons to long-lived particles and for Hidden Valley Z' and Stealth SUSY benchmark models. The first search results for displaced decays in Z' and Stealth SUSY models are presented. The upper bounds of the excluded proper lifetimes are the most stringent to date.
Download or read book Search for Disappearing Tracks in Proton proton Collisions at arrow written by and published by . This book was released on 2015 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search is presented for long-lived charged particles that decay within the CMS detector and produce the signature of a disappearing track. Disappearing tracks are identified as those with little or no associated calorimeter energy deposits and with missing hits in the outer layers of the tracker. The search uses proton-proton collision data recorded at [arrow]" = 8 TeV that corresponds to an integrated luminosity of 19.5 fb-1. The results of the search are interpreted in the context of the anomaly-mediated supersymmetry breaking (AMSB) model. The number of observed events is in agreement with the background expectation, and limits are set on the cross section of direct electroweak chargino production in terms of the chargino mass and mean proper lifetime. At 95% confidence level, AMSB models with a chargino mass less than 260 GeV, corresponding to a mean proper lifetime of 0.2 ns, are excluded.
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 and published by . This book was released on 2016 with total page pages. 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.
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 and published by . This book was released on 2015 with total page pages. 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.
Download or read book Search for Long lived Weakly Interacting Particles that Decay to Displaced Hadronic Jets in Proton proton Collisions at u221A s written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for the decay of neutral, weakly interacting, long-lived particles using data collected by the ATLAS detector at the LHC is presented. This analysis uses the full data set recorded in 2012: 20.3 fb–1 of proton-proton collision data at √s = 8 TeV. The search employs techniques for reconstructing decay vertices of long-lived particles decaying to jets in the inner tracking detector and muon spectrometer. Signal events require at least two reconstructed vertices. No significant excess of events over the expected background is found, and limits as a function of proper lifetime are reported for the decay of the Higgs boson and other scalar bosons to long-lived particles and for Hidden Valley Z' and Stealth SUSY benchmark models. The first search results for displaced decays in Z' and Stealth SUSY models are presented. The upper bounds of the excluded proper lifetimes are the most stringent to date.
Download or read book Search for Long lived Particles Using Delayed Photons in Proton proton Collisions at s written by Albert M. Sirunyan and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Search for Massive Long lived Particles Using Multitrack Displaced Vertices Or Displaced Lepton Pairs in math Display written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. This article presents the results of a search for events containing at least one long-lived particle that decays at a significant distance from its production point into two leptons or into five or more charged particles. In this study, this analysis uses a data sample of proton-proton collisions at \(\sqrt{s} = 8\) TeV corresponding to an integrated luminosity of 20.3 fb−1 collected in 2012 by the ATLAS detector operating at the Large Hadron Collider. No events are observed in any of the signal regions, and limits are set on model parameters within supersymmetric scenarios involving R-parity violation, split supersymmetry, and gauge mediation. In some of the search channels, the trigger and search strategy are based only on the decay products of individual long-lived particles, irrespective of the rest of the event. In these cases, the provided limits can easily be reinterpreted in different scenarios.
Download or read book Search for Dark Matter in Final States Containing Semi visible Jets from Proton proton Collisions at square Root s written by Colin Terrence Fallon and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This dissertation presents a novel search for new physics using the full Run 2 dataset of 137.6 fb-1 collected by the Compact Muon Solenoid during proton-proton runs of the Large Hadron Collider. The new physics in question is dark matter production in a unique signature called semi-visible jets. Semi-visible jets are produced when a new massive mediator particle emerges from the proton-proton interaction. This mediator then decays to unstable dark matter particles which hadronize and produce a mixture of standard model particles and stable dark matter particles. The stable dark particles are only detectable as missing transverse momentum, and the standard particles are detectable as jets. This produces a signature where two jets are produced, one of which is aligned with the total missing transverse momentum. The search is presented in two phases: a classical cut-based search which uses a series of cuts based on event kinematics to select events which look like the signal signature, and a machine learning based search which uses a technique called boosted decision trees to identify semi-visible jets in a more powerful but model-dependent way. No evidence for Physics Beyond the Standard Model is observed in either search. The classical search excludes the possibility that the mediator could have a mass between 1.5 TeV and 3.98 TeV, while the model-dependent search excludes mediators with masses between 1.5 TeV and 5.08 TeV. Additionally, ranges of other signal parameters are excluded"--Page viii.
Download or read book Search for Heavy Long lived Particles that Decay to Photons in Ppbar Collisions at Sqrt s written by Peter Wagner and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents the results of the first search for heavy, neutral, longlived particles that decay to photons at a hadron collider. We use a sample of +jet+missing transverse energy events in pp̄ collisions at s = 1.96 TEV taken with the Collider Detector at Fermilab. Candidate events are selected based on the arrival time of a high-energy photon at the electromagnetic calorimeter as measured with a timing system that was recently installed. The final result is that we find 2 events, using 570"34 pb−1 of data collected during 2004-2005 at the Fermilab Tevatron, consistent with the background estimate of 1.3"0.7 events.
Download or read book Search for Heavy Long lived Particles that Decay to Photons in p bar p Collisions at sqrt s written by and published by . This book was released on 2007 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents the results of the first search for heavy, neutral, longlived particles that decay to photons at a hadron collider. We use a sample of +jet+missing transverse energy events in $p \bar{p}$ collisions at √s = 1.96 TeV taken with the Collider Detector at Fermilab. Candidate events are selected based on the arrival time of a high-energy photon at the electromagnetic calorimeter as measured with a timing system that was recently installed. The final result is that we find 2 events, using 570±34 pb-1 of data collected during 2004-2005 at the Fermilab Tevatron, consistent with the background estimate of 1.3±0.7 events. While our search strategy does not rely on model-specific dynamics, we interpret this result in terms of cross section limits in a supersymmetric model with $\vec{X}$$0\atop{1}$ eG and set a world-best e 01 mass reach of 101 GeV/c2 at e = 5 ns. We can exclude any [gamma]+jet+missing transverse energy signal that would produce more than 5.5 events.
Download or read book Nuclear Physics written by National Research Council and published by National Academies Press. This book was released on 1999-03-31 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dramatic progress has been made in all branches of physics since the National Research Council's 1986 decadal survey of the field. The Physics in a New Era series explores these advances and looks ahead to future goals. The series includes assessments of the major subfields and reports on several smaller subfields, and preparation has begun on an overview volume on the unity of physics, its relationships to other fields, and its contributions to national needs. Nuclear Physics is the latest volume of the series. The book describes current activity in understanding nuclear structure and symmetries, the behavior of matter at extreme densities, the role of nuclear physics in astrophysics and cosmology, and the instrumentation and facilities used by the field. It makes recommendations on the resources needed for experimental and theoretical advances in the coming decade.
Download or read book Measurements of H b b Decays and VH Production with the ATLAS Detector at the Large Hadron Collider in Proton proton Collisions at S written by Thomas Paul Charman and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Search for W u2192 Tb in Proton proton Collisions at sqrt s written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for dark matter particles directly produced in proton-proton collisions recorded by the CMS experiment at the LHC is presented. The data correspond to an integrated luminosity of 18.8 inverse femtobarns, at a center-of-mass energy of 8 TeV. The event selection requires at least two jets and no isolated leptons. The razor variables are used to quantify the transverse momentum balance in the jet momenta. The study is performed separately for events with and without jets originating from b quarks. The observed yields are consistent with the expected backgrounds and, depending on the nature of the production mechanism, dark matter production at the LHC is excluded at 90% confidence level for a mediator mass scale Lambda below 1 TeV. The use of razor variables yields results that complement those previously published.
Download or read book A Search for Long Lived Particles that Decay to Muons Using the ATLAS Detector written by Melissa Yexley and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
