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Searches For New Phenomena Using Events With Three Or More Charged Leptons In Pp Collisions At Sqrts
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Book Synopsis Searches for New Phenomena Using Events with Three Or More Charged Leptons in $pp$ Collisions at $\sqrt{s} by : David Ren-Hwa Yu
Download or read book Searches for New Phenomena Using Events with Three Or More Charged Leptons in $pp$ Collisions at $\sqrt{s} written by David Ren-Hwa Yu and published by . This book was released on 2015 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents two searches for phenomena beyond the Standard Model using events with three or more charged leptons. The searches are based on 20.3 fb-1 of proton- proton collision data with a center-of-mass energy of √s = 8 TeV collected by the ATLAS detector at the CERN Large Hadron Collider in 2012. The first is a model-independent search for excesses beyond Standard Model expectations in many signal regions. The events are required to have least three charged leptons, of which at least two are electrons or muons, and at most one is a hadronically decaying [tau] lepton. The selected events are categorized based on the flavor and charge of the leptons, and the signal regions are defined using several kinematic variables sensitive to beyond the Standard Model phenomena. The second search looks for new heavy leptons decaying resonantly to three electrons or muons, two of which are produced through an intermediate Z boson. The resonant decay produces a narrowly- peaked excess in the trilepton mass spectrum. In both cases, no significant excess beyond Standard Model expectations is observed, and the data are used to set limits on models of new physics. The model-independent trilepton search is used to confront a model of doubly charged scalar particles decaying to e[tau] or [mu][tau], excluding masses below 400 GeV at 95% confidence level. The trilepton resonance search is used to test models of vector-like leptons and the type III neutrino seesaw mechanism. The vector-like lepton model is excluded for most of the mass range 114 GeV - 176 GeV, while the type III seesaw model is excluded for most the mass range 100 GeV - 468 GeV. Both searches also present tools to facilitate reinterpretations in the context of other models predicting the production of three or more charged leptons.
Book Synopsis Search for New Phenomena in Three- Or Four-lepton Events in Pp Collisions at [square Root]s by : [Study Group] ATLAS Collaboration CERN
Download or read book Search for New Phenomena in Three- Or Four-lepton Events 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 with minimal model dependence for physics beyond the Standard Model in events featuring three or four charged leptons (3l and 4l, ) is presented. The analysis aims to be sensitive to a wide range of potential new-physics theories simultaneously. This analysis uses data from pp collisions delivered by the Large Hadron Collider at a centre-of-mass energy of TeV and recorded with the ATLAS detector, corresponding to the full Run 2 dataset of 139 fb−1. The 3l and 4l phase space is divided into 22 event categories according to the number of leptons in the event, the missing transverse momentum, the invariant mass of the leptons, and the presence of leptons originating from a Z-boson candidate. These event categories are analysed independently for the presence of deviations from the Standard Model. No statistically significant deviations from the Standard Model predictions are observed. Upper limits for all signal regions are reported in terms of the visible cross-section
Book Synopsis Search for Anomalous Production of Events with Three Or More Leptons in Pp Collisions at Sqrt(s) by :
Download or read book Search for Anomalous Production of Events with Three Or More Leptons in Pp Collisions at Sqrt(s) written by and published by . This book was released on 2014 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for physics beyond the standard model in events with at least three leptons is presented. The data sample, corresponding to an integrated luminosity of 19.5 inverse femtobarns of proton-proton collisions with center-of-mass energy sqrt(s) = 8 TeV, was collected by the CMS experiment at the LHC during 2012. The data are divided into exclusive categories based on the number of leptons and their flavor, the presence or absence of an opposite-sign, same-flavor lepton pair (OSSF), the invariant mass of the OSSF pair, the presence or absence of a tagged bottom-quark jet, the number of identified hadronically decaying tau leptons, and the magnitude of the missing transverse energy and of the scalar sum of jet transverse momenta. The numbers of observed events are found to be consistent with the expected numbers from standard model processes, and limits are placed on new-physics scenarios that yield multilepton final states. In particular, scenarios that predict Higgs boson production in the context of supersymmetric decay chains are examined. We also place a 95% confidence level upper limit of 1.3% on the branching fraction for the decay of a top quark to a charm quark and a Higgs boson (t to c H), which translates to a bound on the left- and right-handed top-charm flavor-violating Higgs Yukawa couplings, lambda[H, tc] and lambda[H, ct], respectively, of sqrt(abs(lambda[H, tc])2̂ + abs(lambda[H, ct])2̂)
Book Synopsis A Search for Excited Leptons in Pp Collisions at Sqrt(s) by :
Download or read book A Search for Excited Leptons in Pp Collisions at Sqrt(s) written by and published by . This book was released on 2011 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for excited leptons is carried out with the CMS detector at the LHC, using 36 inverse picobarns of pp collision data recorded at sqrt(s) = 7 TeV. The search is performed for associated production of a lepton and an oppositely charged excited lepton pp to l l*, followed by the decay l* to l gamma, resulting in the l l gamma final state, where l = electron or muon. No excess of events above the standard model expectation is observed. Interpreting the findings in the context of l* production through four-fermion contact interactions and subsequent decay via electroweak processes, first upper limits are reported for l* production at this collision energy. The exclusion region in the compositeness scale Lambda and excited lepton mass M(l*) parameter space is extended beyond previously established limits. For Lambda = M(l*), excited lepton masses are excluded below 1070 GeV/c2̂ for e* and 1090 GeV/c2̂ for mu* at the 95% confidence level.
Book Synopsis Search for Physics Beyond the Standard Model in Events with Two Leptons, Jets, and Missing Transverse Momentum in Pp Collisions at Sqrt(s) by :
Download or read book Search for Physics Beyond the Standard Model in Events with Two Leptons, Jets, and Missing Transverse Momentum in Pp Collisions at Sqrt(s) written by and published by . This book was released on 2015 with total page 37 pages. Available in PDF, EPUB and Kindle. Book excerpt: Our search is presented for physics beyond the standard model in final states with two opposite-sign same-flavor leptons, jets, and missing transverse momentum. The data sample corresponds to an integrated luminosity of 19.4 fb-1 of proton-proton collisions at √s = 8 TeV collected with the CMS detector at the CERN LHC in 2012. The analysis focuses on searches for a kinematic edge in the invariant mass distribution of the oppositesign same-flavor lepton pair and for final states with an on-shell Z boson. Furthermore, the observations are consistent with expectations from standard model processes and are interpreted in terms of upper limits on the production of supersymmetric particles.
Book Synopsis Searches for New Phenomena with Lepton Final States at the Tevatron by :
Download or read book Searches for New Phenomena with Lepton Final States at the Tevatron written by and published by . This book was released on 2007 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Numerous searches for new phenomena have been carried out using data from proton-antiproton collisions at Fermilab's Tevatron. Final states with leptons give signatures which are relatively unique and generally have small backgrounds. We present many of the latest results from the CDF and D0 collaborations from 0.4-1.2 fb−1 of data. Topics include supersymmetry, extra gauge bosons, Randall-Sundrum gravitons, excited electrons and neutral, long-lived particles.
Book Synopsis A Generic Search for New Physics in Same-sign Dilepton Events in [square Root] (s) by : Robert Austin Porter
Download or read book A Generic Search for New Physics in Same-sign Dilepton Events in [square Root] (s) written by Robert Austin Porter and published by . This book was released on 2011 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes a generic search for new physics in events with two leptons having the same electric charge resulting from proton-antiproton collisions at the Fermilab Tevatron. The data set analyzed corresponds to 6/fb of integrated luminosity recorded by the Collider Detector at Fermilab (CDF). A previous analysis of 1/fb−1 of data in the same channel observed a small excess, motivating a reexamination of the channel. A data-driven technique is used for modeling events where one lepton is a misidentified jet, and Monte Carlo simulation is used for the remaining Standard Model background. The data are found to be consistent with the expected background and limits are set on several models predicting events in this channel.
Book Synopsis Search for Physics Beyond the Standard Model Using Multilepton Signatures in Pp Collisions at Sqrt(s) by :
Download or read book Search for Physics Beyond the Standard Model Using Multilepton Signatures in Pp Collisions at Sqrt(s) written by and published by . This book was released on 2011 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for physics beyond the standard model in events with at least three leptons and any number of jets is presented. The data sample corresponds to 35 inverse picobarns of integrated luminosity in pp collisions at sqrt(s) = 7 TeV collected by the CMS experiment at the LHC. A number of exclusive multileptonic channels are investigated and standard model backgrounds are suppressed by requiring sufficient missing transverse energy, invariant mass inconsistent with that of the Z boson, or high jet activity. Control samples in data are used to ascertain the robustness of background evaluation techniques and to minimise the reliance on simulation. The observations are consistent with background expectations. These results constrain previously unexplored regions of supersymmetric parameter space.
Book Synopsis Search for New Physics in Lepton + Photon + X Events with 305 Pb**-1 of P Anti-p Collisions at S**ư by :
Download or read book Search for New Physics in Lepton + Photon + X Events with 305 Pb**-1 of P Anti-p Collisions at S**ư written by and published by . This book was released on 2006 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present results of a search for anomalous production of events containing a charged lepton (l, either e or?) and a photon , both with high transverse momentum, accompanied by additional signatures, X, including missing transverse energy (E{sub T}) and additional leptons and photons. We use the same kinematic selection criteria as in a previous CDF search, but with a substantially larger data set, 305 pb−1, a p{bar p} collision energy of 1.96 TeV, and the upgraded CDF II detector. We find 42 l?E{sub T} events versus a standard model expectation of 37.3 ± 5.4 events. The level of excess observed in Run I, 16 events with an expectation of 7.6 ± 0.7 events (corresponding to a 2.7? effect), is not supported by the new data. In the signature of ll? + X we observe 31 events versus an expectation of 23.0 ± 2.7 events. In this sample we find no events with an extra photon or E{sub T} and so find no events like the one ee??E{sub T} event observed in Run I.
Book Synopsis A Search for New Phenomena in Pp Collisions at $\sqrt{s}$ by :
Download or read book A Search for New Phenomena in Pp 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 new phenomena is performed in final states containing one or more jets and an imbalance in transverse momentum in pp collisions at a centre-of-mass energy of 13 TeV. The analysed data sample, recorded with the CMS detector at the CERN LHC, corresponds to an integrated luminosity of 2.3 inverse femtobarns. Several kinematic variables are employed to suppress the dominant background, multijet production, as well as to discriminate between other standard model and new physics processes. The search provides sensitivity to a broad range of new-physics models that yield a stable weakly interacting massive particle. The number of observed candidate events is found to agree with the expected contributions from standard model processes, and the result is interpreted in the mass parameter space of fourteen simplified supersymmetric models that assume the pair production of gluinos or squarks and a range of decay modes. For models that assume gluino pair production, masses up to 1575 and 975 GeV are excluded for gluinos and neutralinos, respectively. For models involving the pair production of top squarks and compressed mass spectra, top squark masses up to 400 GeV are excluded.
Book Synopsis A Search for New Physics in Photon-lepton Events in Proton-antiproton Collisions At[radical] S by :
Download or read book A Search for New Physics in Photon-lepton Events in Proton-antiproton Collisions At[radical] S written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the results of a search in p[bar p] collisions at[radical]s= 1.8 TeV for anomalous production of events containing a photon with large transverse energy and a lepton (e or[mu]) with large transverse energy, using 86 pb[sup -1] of data collected at the Collider Detector at Fermilab during the 1994-95 collider run at the Fermilab Tevatron. The presence of large missing transverse energy (E[sub T]), additional photons, or additional leptons in these events is also analyzed. The results are consistent with standard model expectations, with the possible exception of photon-lepton events with large E[sub T], for which the probability of a statistical fluctuation of the standard model expectation up to and above the observed level is 0.7%.
Book Synopsis Search for Anomalous Production of Multi-lepton Events in P Anti-p Collisions at S**1/2 by :
Download or read book Search for Anomalous Production of Multi-lepton Events in 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: The authors report a search for the anomalous production of events with multiple charged leptons in p{bar p} collisions at √s = 1.96 TeV using a data sample corresponding to an integrated luminosity of 346 pb−1 collected by the CDF II detector at the Fermilab Tevatron. The search is divided into three-lepton and four-or-more-lepton data samples. They observe six events in the three-lepton sample and zero events in the ≥4-lepton sample. Both numbers of events are consistent with standard model background expectations. Within the framework of an R-parity violating supergravity model, the results are interpreted as mass limits on the lightest neutralino ({bar {chi}}1°) and chargino ({bar {chi}}1{sup {+-}}) particles. For one particular choice of model parameters, the limits are M({bar {chi}}1°) > 110 GeV/c2 and M({bar {chi}}1{sup {+-}}) > 203 GeV/c2 at 95% confidence level; the variation of these mass limits with model parameters is presented.
Book Synopsis Search for Anomalous Production of Multi-lepton Events in P Anti-p Collisions at S**ư by :
Download or read book Search for Anomalous Production of Multi-lepton Events in P Anti-p Collisions at S**ư 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 report a search for the anomalous production of events with multiple charged leptons in p{bar p} collisions at √s = 1.96 TeV using a data sample corresponding to an integrated luminosity of 346 pb−1 collected by the CDF II detector at the Fermilab Tevatron. The search is divided into three-lepton and four-or-more-lepton data samples. They observe six events in the three-lepton sample and zero events in the ≥4-lepton sample. Both numbers of events are consistent with standard model background expectations. Within the framework of an R-parity violating supergravity model, the results are interpreted as mass limits on the lightest neutralino ({bar {chi}}1°) and chargino ({bar {chi}}1{sup {+-}}) particles. For one particular choice of model parameters, the limits are M({bar {chi}}1°)> 110 GeV/c2 and M({bar {chi}}1{sup {+-}})> 203 GeV/c2 at 95% confidence level; the variation of these mass limits with model parameters is presented.
Book Synopsis Search for New Physics in Lepton + Photon + X Events with 305 Pb**-1 of P Anti-p Collisions at S**1/2 by :
Download or read book Search for New Physics in Lepton + Photon + X Events with 305 Pb**-1 of P Anti-p Collisions at S**1/2 written by and published by . This book was released on 2006 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present results of a search for anomalous production of events containing a charged lepton (l, either e or [mu]) and a photon ([gamma]), both with high transverse momentum, accompanied by additional signatures, X, including missing transverse energy (E{sub T}) and additional leptons and photons. We use the same kinematic selection criteria as in a previous CDF search, but with a substantially larger data set, 305 pb−1, a p{bar p} collision energy of 1.96 TeV, and the upgraded CDF II detector. We find 42 l[gamma]E{sub T} events versus a standard model expectation of 37.3 ± 5.4 events. The level of excess observed in Run I, 16 events with an expectation of 7.6 ± 0.7 events (corresponding to a 2.7[sigma] effect), is not supported by the new data. In the signature of ll[gamma] + X we observe 31 events versus an expectation of 23.0 ± 2.7 events. In this sample we find no events with an extra photon or E{sub T} and so find no events like the one ee[gamma][gamma]E{sub T} event observed in Run I.
Book Synopsis Search for New Physics in Lepton + Photon + X Events with 929 Pb**-1 of P Anti-p Collisions at S**ư by :
Download or read book Search for New Physics in Lepton + Photon + X Events with 929 Pb**-1 of P Anti-p Collisions at S**ư written by and published by . This book was released on 2006 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present results of a search in 929 ± 56 pb−1 of p{bar p} collisions at 1.96 TeV for the anomalous production of events containing a charged lepton (l, either e or?) and a photon , both with high transverse momentum, accompanied by additional signatures, X, including missing transverse energy (E{sub T}) and additional leptons and photons. They use the same selection criteria as in the previous CDF Run I search, but with an order-magnitude larger data set, a higher p{bar p} collision energy, and the CDF II detector.
Book Synopsis Search for New Physics in Events with Same-sign Dileptons and Jets in Pp Collisions at $\sqrt{s}$ by :
Download or read book Search for New Physics in Events with Same-sign Dileptons and Jets in Pp Collisions at $\sqrt{s}$ written by and published by . This book was released on 2014 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for new physics is performed based on events with jets and a pair of isolated, same-sign leptons. The results are obtained using a sample of proton-proton collision data collected by the CMS experiment at a centre-of-mass energy of 8 TeV at the LHC, corresponding to an integrated luminosity of 19.5 inverse femtobarns. In order to be sensitive to a wide variety of possible signals beyond the standard model, multiple search regions defined by the missing transverse energy, the hadronic energy, the number of jets and b-quark jets, and the transverse momenta of the leptons in the events are considered. No excess above the standard model background expectation is observed and constraints are set on a number of models for new physics, as well as on the same-sign top-quark pair and quadruple-top-quark production cross sections. As a result, information on event selection efficiencies is also provided, so that the results can be used to confront an even broader class of new physics models.
Book Synopsis Search for New Physics in Lepton + Photon + X Events with 929 Pb**-1 of P Anti-p Collisions at S**(1/2) by : A. Loginov
Download or read book Search for New Physics in Lepton + Photon + X Events with 929 Pb**-1 of P Anti-p Collisions at S**(1/2) written by A. Loginov and published by . This book was released on 2006 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present results of a search in 929 {+-} 56 pb{sup -1} of p{bar p} collisions at 1.96 TeV for the anomalous production of events containing a charged lepton ({ell}, either e or {mu}) and a photon ({gamma}), both with high transverse momentum, accompanied by additional signatures, X, including missing transverse energy (E{sub T}) and additional leptons and photons. They use the same selection criteria as in the previous CDF Run I search, but with an order-magnitude larger data set, a higher p{bar p} collision energy, and the CDF II detector.
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