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 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 at CDF II written by and published by . This book was released on 2007 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present the first search for heavy, long-lived particles that decay to photons at a hadron collider. They use a sample of [gamma] + jet + missing transverse energy events in p{bar p} collisions at √s = 1.96 TeV taken with the CDF II detector. Candidate events are selected based on the arrival time of the photon at the detector. Using an integrated luminosity of 570 pb−1 of collision data, they observe 2 events, consistent with the background estimate of 1.3 ± 0.7 events. While the search strategy does not rely on model-specific dynamics, they set cross section limits in a supersymmetric model with {tilde {chi}}1° → [gamma]{tilde G} and place the world-best 95% C.L. lower limit on the {tilde {chi}}1° mass of 101 GeV/c2 at [tau]{sub {tilde {chi}}1°} = 5 ns.
Download or read book Search for New Physics in the Exclusive Gamma MET Final State in P pbar Collisions at Sqrt s written by Adam Jude Aurisano and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents a search for heavy, long-lived, neutral particles that decay to photons in proton anti-proton collisions with a center of mass energy of 1.96 TeV at the Collider Detector at Fermilab (CDF) experiment. Such particles are typical of models of Gauge Mediated Supersymmetry Breaking (GMSB). We select events with a single photon, missing transverse energy, and little other activity in the detector. We model the photon arrival time for Standard Model and non-collision sources using a data-driven method and consider photons which have a time of arrival at the detector which is significantly delayed relative to predictions. Using 6.3 fb-1 of data collected from December 2004 to June 2010, we observe 322 events in the signal region compared to a background prediction of 287 ± 24 events. While the data are consistently above predictions, we report a model excess with a significance of 1.2 standard deviations from the null hypothesis. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/148427
Download or read book Search for Weakly interacting Long lived Particles in Proton proton Collisions at square Root Of S written by Orin Michael Harris and published by . This book was released on 2013 with total page 203 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for the decay of a light Higgs boson to a pair of weakly-interacting, long-lived particles in 20.8 fb-1 of proton-proton collisions at [square root of] s = 8 TeV recorded in 2012 by the ATLAS detector is presented. The strategy requires that both of the long-lived particles decay just before or inside the hadronic calorimeter. No statistically significant excess of events is observed above the expected background and limits on the Higgs boson production and branching ratio to weakly-interacting, long-lived particles are derived as a function of the particle's proper decay length.
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 Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 892 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Search for Long lived Particles Using Delayed Photons in Proton proton Collisions at 13 TeV with the CMS Detector written by Kevin Patrick McDermott and published by . This book was released on 2019 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents a search for long-lived particles using delayed photons in proton-proton collisions at sqrt(s) = 13 TeV recorded by the Compact Muon Solenoid (CMS) experiment at the CERN Large Hadron Collider in 2017, corresponding to an integrated luminosity of 41.5 fb^-1. This analysis includes a number of unique components that will be discussed: a dedicated signal trigger, out-of-time photon reconstruction and identification, and a detector time resolution measurement. The results of this search include the combination of a related analysis using data collected in 2016 also at sqrt(s) = 13 TeV, corresponding to a combined integrated luminosity of 77.4 fb^-1. The combined results are interpreted in the context of supersymmetry with gauge-mediated supersymmetry breaking, where the neutralino is long-lived and decays to a photon and a gravitino. Limits are presented as a function of the neutralino proper decay length and mass. For neutralino proper decay lengths of 10^1, 10^2, 10^3, and 10^4 cm, masses up to 320, 525, 360, and 215 GeV are excluded at 95% confidence level, respectively. Additionally, a discussion on a high-performance computing upgrade to CMS, known as mkFit, will be presented. mkFit is an on-going effort to exploit highly parallel computer architectures in vectorizing and parallelizing combinatorial Kalman filter charged particle track reconstruction algorithms. The current physics and computational performance of this project will be discussed.
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 Stopped Gluinos from P anti p Collisions at S 1 2 written by and published by . This book was released on 2007 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: Long-lived, heavy particles are predicted in a number of models beyond the standard model of particle physics. We present the first direct search for such particles' decays, occurring up to 100 h after their production and not synchronized with an accelerator bunch crossing. We apply the analysis to the gluino ({tilde g}), predicted in split supersymmetry, which after hadronization can become charged and lose enough momentum through ionization to come to rest in dense particle detectors. Approximately 410 pb−1 of p{bar p} collisions at sqrt(s)=1.96 TeV collected with the D0 detector during Run II of the Fermilab Tevatron collider are analyzed in search of such 'stopped gluinos' decaying into a gluon and a neutralino ({tilde {chi}}1°). Limits are placed on the (gluino cross section)x(probability to stop)x[BR({tilde g}→g {tilde {chi}}1{sup 0
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 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 Neutral Long lived Particles in Pp Collisions at square Root s written by [Study Group] ATLAS Collaboration CERN and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: A search for decays of pair-produced neutral long-lived particles (LLPs) is presented using 139 fb−1 of proton-proton collision data collected by the ATLAS detector at the LHC in 2015-2018 at a centre-of-mass energy of 13 TeV. Dedicated techniques were developed for the reconstruction of displaced jets produced by LLPs decaying hadronically in the ATLAS hadronic calorimeter. Two search regions are defined for different LLP kinematic regimes. The observed numbers of events are consistent with the expected background, and limits for several benchmark signals are determined. For a SM Higgs boson with a mass of 125 GeV, branching ratios above 10% are excluded at 95% confidence level for values of c times LLP mean proper lifetime in the range between 20 mm and 10 m depending on the model. Upper limits are also set on the cross-section times branching ratio for scalars with a mass of 60 GeV and for masses between 200 GeV and 1 TeV
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 Charged Particles in Proton proton Collisions at math Display written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Results are presented of a search for heavy stable charged particles produced in proton-proton collisions at √s = 13 TeV using a data sample corresponding to an integrated luminosity of 2.5 fb-1 collected in 2015 with the CMS detector at the CERN LHC. The search is conducted using signatures of anomalously high energy deposits in the silicon tracker and long time-of-flight measurements by the muon system. The data are consistent with the expected background, and upper limits are set on the cross sections for production of long-lived gluinos, top squarks, tau sleptons, and lepton-like long-lived fermions. These upper limits are equivalently expressed as lower limits on the masses of new states; the limits for gluinos, ranging up to 1610 GeV, are the most stringent to date. Furthermore, limits on the cross sections for direct pair production of long-lived tau sleptons are also determined.
Download or read book Search for Stopped Long lived Particles Produced in Pp Collisions at 8 TeV at CMS written by Marissa L. Rodenburg and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: At the Large Hadron Collider counter-rotating proton beams are collided at sqrt(s) = 8 TeV. The Compact Muon Solenoid (CMS) is used to measure the energies and charges of the resulting cascade of particles produced in these collisions. This search focuses on the observation of massive, long-lived particles, such as the gluino, that would suggest new physics beyond the Standard Model. A custom trigger is used to probe time periods during which no proton collisions occur, thereby eliminating most backgrounds to the signal. The remaining backgrounds resulting from cosmic rays, beam-related effects, and instrumental noise, are further reduced using a series of sophisticated selection cuts. Candidate events passing all selection cuts are analyzed using a counting experiment and limits are placed on the cross sections and masses of the gluino and the supersymmetric top quark.
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.
