Download or read book Search for CP Violation in Top Quark antiquark Production and Decay 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: The results of a first search for CP violation in the production and decay of top quark-antiquark (ttbar) pairs are presented. The search is based on asymmetries in T-odd, triple-product correlation observables, where T is the time-reversal operator. The analysis uses a sample of proton-proton collisions at $\sqrt{s}$ TeV collected by the CMS experiment, corresponding to an integrated luminosity of 19.7 inverse femtobarns. Events are selected having one electron or muon and at least four jets. The T-odd observables are measured using four-momentum vectors associated with ttbar production and decay. The measured asymmetries exhibit no evidence for CP-violating effects, consistent with the expectation from the standard model.
Download or read book Search for Cp Violation in Top Quark antiquark Production and Decay in Proton proton Collisions written by 蔡瑞發 and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Search for CP Violation Using Top Quark antiquark Events in the Lepton jets Channel in Pp Collisions with s written by 陳溥生 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 Searches for CP Violation in Charmed Meson Decays written by Hamish Gordon and published by Springer. This book was released on 2014-06-07 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: Our current understanding of the fundamental building blocks of the Universe, summarised by the Standard Model of particle physics, is incomplete. For example, it fails to explain why we do not see equal, or almost equal, numbers of particles and their antiparticle partners. To explain this asymmetry requires, among other effects, a mechanism known as charge-parity (CP) violation that causes differences between the rates at which particles and antiparticles decay. CP violation is seen in systems containing bottom and strange quarks, but not in those with up, charm or top quarks. This thesis describes searches for particle-antiparticle asymmetries in the decay rates of charmed mesons. No evidence of CP violation is found. With current sensitivities, an asymmetry large enough to observe probably could not be explained by the Standard Model. Instead an explanation could come from new physics, for example contributions from supersymmetric or other undiscovered heavy particles. In the thesis, the development of new techniques to search for these asymmetries is described. They are applied to data from the LHCb experiment at CERN to make precise measurements of asymmetries in the D^+->K^-K^+pi^+ decay channel. This is the most promising charged D decay for CP violation searches.
Download or read book Search for R parity Violating Decays of a Top Squark in Proton u2013 proton Collisions at written by and published by . This book was released on 2016 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results of a search for a supersymmetric partner of the top quark (top squark), pair-produced in proton-proton collisions at $\sqrt{s} =$ 8 TeV, are presented. The search, which focuses on R-parity violating, chargino-mediated decays of the top squark, is performed in final states with low missing transverse momentum, two oppositely charged electrons or muons, and at least five jets. The analysis uses a data sample corresponding to an integrated luminosity of 19.7 fb${̂-1}$ collected with the CMS detector at the LHC in 2012. The data are found to be in agreement with the standard model expectation, and upper limits are placed on the top squark pair production cross section at 95% confidence level. Assuming a 100% branching fraction for the top squark decay chain, $ \mathrm{ \tilde{t} \to t \tilde{\chi}{̂\pm}_1,\, \tilde{\chi}{̂\pm}_1 \to \ell\̂pm+jj } $, top squark masses less than 890 (1000) GeV for the electron (muon) channel are excluded for the first time in models with a single nonzero R-parity violating coupling $\lambda{̂\prime}_{ijk}$ $(i,j,k \leq 2)$, where $i,j,k$ correspond to the three generations.
Download or read book CP Violation in Single Top Quark Production written by Weigang Geng and published by . This book was released on 2012 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a search for CP violation in single top quark production with the DØ experiment at the Tevatron proton-antiproton collider. CP violation in the top electroweak interaction results in different single top quark production cross sections for top and antitop quarks. We perform the search in the single top quark final state using 5.4 fb-1 of data, in the s-channel, t-channel, and for both combined. At this time, we do not see an observable CP asymmetry.
Download or read book CP Violating Anomalous Top quark Coupling in P bar p Collision at sqrt s written by and published by . This book was released on 2011 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt: We conduct the first study of the T-odd correlations in tt events produced in p{bar p} collision at the Fermilab Tevatron collider that can be used to search for CP violation. We select events which have lepton+jets final states to identify t{bar t} events and measure counting asymmetries of several physics observables. Based on the result, we search the top quark anomalous couplings at the production vertex at the Tevatron. In addition, Geant4 development, photon identification, the discrimination of a single photon and a photon doublet from [pi]° decay are discussed in this thesis.
Download or read book CP Violation in Single Top Quark Production written by and published by . This book was released on 2012 with total page 239 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a search for CP violation in single top quark production with the DØ experiment at the Tevatron proton-antiproton collider. CP violation in the top electroweak interaction results in different single top quark production cross sections for top and antitop quarks. We perform the search in the single top quark final state using 5.4 fb-1 of data, in the s-channel, t-channel, and for both combined. At this time, we do not see an observable CP asymmetry.
Download or read book Cp Violation written by Cecilia Jarlskog and published by World Scientific. This book was released on 1989-01-01 with total page 733 pages. Available in PDF, EPUB and Kindle. Book excerpt: Contents:CP Phenomenology:Introduction to CP Violation (C Jarlskog)CP-Violation in the K0-K0-System (K Kleinknecht)The Quark Mixing Matrix, Charm Decays and B Decays (S Stone)The Question of CP Noninvariance — As Seen through the Eyes of Neutral Beauty (I I Bigi et al.)In Search of CP Noninvariance in Heavy Quark Systems (L-L Chau)CP Violation at High Energy e+e- Colliders (J Bernabéu & M B Gavela)CP Violation in the Standard Model with Four Families (A Datta & E A Paschos)CP Effects When Neutrinos are their Own Antiparticles (B Kayser)On Spontaneous CP Violation Triggered by Scalar Bosons (I I Bigi & A I Sanda)CP Violation and Left-Right Symmetry (R N Mohapatra)CP Violation and Supersymmetry (R N Mohapatra)Electric Dipole Moments (S M Barr & W H Marciano)Special Topics: The Strong CP Problem (R D Peccei)CP Violation and Cosmology (P Langacker)Nonleptonic Interactions:The 1/N Approach to Nonleptonic Weak Interactions (A J Buras)Chiral Perturbation Theory Approach to Weak Amplitudes (E de Rafael)What We Learnt from Weak Decays of Heavy Quarks (B Stech)Weak Hamiltonian on the Lattice (G Martinelli) Readership: High energy physicists. Keywords:CP Violation;Quark Mixing Matrix;Charm Decays;B Decays;Nonleptic Interactions;Heavy QuarksReview: “Similar material is most often available in journals, but the book accomplishes a valuable service in drawing it together … the one that will probably have the greatest utility and longest lifespan is the survey of B meson physics by I Bigi, V Khoze, N Uraltsev and A Sanda … Bigi et al. here provide the most thorough and readable account of the issues that I know of. I have seen no review comparable to the excellent summary of electric dipole moments by S Barr and W Marciano … the volume offers a generally readable entry into this field for a reader who has a basic background in particle physics.” John F Donoghue Science “… this book performs a very useful service for anyone active or interested in CP violation, both as a source of primary information and as a work of reference.” K J Peach J Phys. G: Nucl. Part. Phys.
Download or read book Search for S Channel Single Top Quark Production 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 is presented for single top quark production in the s channel in proton-proton collisions with the CMS detector at the CERN LHC in decay modes of the top quark containing a muon or an electron in the final state. The signal is extracted through a maximum-likelihood fit to the distribution of a multivariate discriminant defined using boosted decision trees to separate the expected signal contribution from background processes. Data collected at centre-of-mass energies of 7 and 8 TeV yield cross sections of 7.1 +/- 8.1 pb and 13.4 +/- 7.3 pb, respectively, and a best fit value of 2.0 +/- 0.9 for the combined ratio of the measured and expected values. The signal significance is 2.5 standard deviations, and the upper limit on the rate relative to the standard model expectation is 4.7 at 95% confidence level.
Download or read book Search for Baryon Number Violation in Top quark Decays written by and published by . This book was released on 2014 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for baryon number violation (BNV) in top-quark decays is performed using pp collisions produced by the LHC at sqrt(s) = 8 TeV. The top-quark decay considered in this search results in one light lepton (muon or electron), two jets, but no neutrino in the final state. Data used for the analysis were collected by the CMS detector and correspond to an integrated luminosity of 19.5 inverse femtobarns. The event selection is optimized for top quarks produced in pairs, with one undergoing the BNV decay and the other the standard model hadronic decay to three jets. No significant excess of events over the expected yield from standard model processes is observed. The upper limits at 95% confidence level on the branching fraction of the BNV top-quark decay are calculated to be 0.0016 and 0.0017 for the muon and the electron channels, respectively. Assuming lepton universality, an upper limit of 0.0015 results from the combination of the two channels. These limits are the first that have been obtained on a BNV process involving the top quark.
Download or read book Search for Long lived Neutral Particles Decaying to Quark antiquark Pairs 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 is performed for long-lived massive neutral particles decaying to quark-antiquark pairs. The experimental signature is a distinctive topology of a pair of jets, originating at a secondary vertex. Events were collected with the CMS detector at the CERN LHC in proton-proton collisions at a center-of-mass energy of 8 TeV. The data analyzed correspond to an integrated luminosity of 18.5 fb–1. No significant excess is observed above standard model expectations. Upper limits at 95% confidence level are set on the production cross section of a heavy neutral scalar particle, H, in the mass range of 200 to 1000 GeV, decaying promptly into a pair of long-lived neutral X particles in the mass range of 50 to 350 GeV, each in turn decaying into a quark-antiquark pair. For X with mean proper decay lengths of 0.4 to 200 cm, the upper limits are typically 0.5–200 fb. The results are also interpreted in the context of an R-parity-violating supersymmetric model with long-lived neutralinos decaying into a quark-antiquark pair and a muon. For pair production of squarks that promptly decay to neutralinos with mean proper decay lengths of 2–40 cm, the upper limits on the cross section are typically 0.5–3 fb. As a result, the above limits are the most stringent on these channels to date.
Download or read book Search for Standard Model Production of Four Top Quarks in Proton proton Collisions at sqrt s written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for events containing four top quarks (ttbar-ttbar) is reported from proton-proton collisions recorded by the CMS experiment at sqrt(s) = 13 TeV and corresponding to an integrated luminosity of 2.6 inverse femtobarns The analysis considers the single-lepton (e or mu)+jets and the opposite-sign dilepton (mu+mu-, mu+/- e-/+, or e+e- )+jets channels. It uses boosted decision trees to combine information on the global event and jet properties to distinguish between ttbar-ttbar and ttbar production. The number of events observed after all selection requirements is consistent with expectations from background and standard model signal predictions, and an upper limit is set on the cross section for ttbar-ttbar production in the standard model of 94 fb at 95% confidence level (10.2 times the prediction), with an expected limit of 118 fb. This is combined with the results from the published CMS search in the same-sign dilepton channel, resulting in an improved limit of 69 fb at 95% confidence level (7.4 times the prediction), with an expected limit of 71 fb. These are the strongest constraints on the rate of ttbar-ttbar production to date.
Download or read book Search for the Production of an Excited Bottom Quark Decaying to TW in Proton proton Collisions at sqrt s written by and published by . This book was released on 2015 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: Our search is presented for a singly produced excited bottom quark (b*) decaying to a top quark and a W boson in the all-hadronic, lepton+jets, and dilepton final states in proton-proton collisions at √s = 8 TeV recorded by the CMS experiment at the CERN LHC. Data corresponding to an integrated luminosity of 19.7 fb-1 are used. No significant excess of events is observed with respect to standard model expectations. We set limits at 95% confidence on the product of the b* quark production cross section and its branching fraction to tW. Furthermore, the cross section limits are interpreted for scenarios including left-handed, right-handed, and vector-like couplings of the b* quark and are presented in the two-dimensional coupling plane based on the production and decay coupling constants. The masses of the left-handed, right-handed, and vectorlike b* quark states are excluded at 95% confidence below 1390, 1430, and 1530 GeV, respectively, for benchmark couplings. This analysis gives the most stringent limits on the mass of the b* quark to date.
Download or read book Search for a Heavy Bottom like Quark in Pp Collisions at Sqrt s written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for pair-produced bottom-like quarks in pp collisions at sqrt(s) = 7 TeV is conducted with the CMS experiment at the LHC. The decay b' to tW is considered in this search. The b' b'-bar to tW-̂ t-bar W+̂ process can be identified by the distinctive signature of trileptons and same-sign dileptons. With a data sample corresponding to an integrated luminosity of 34 inverse picobarns, no excess above the standard model background predictions is observed and a b' quark with a mass between 255 and 361 GeV/c2̂ is excluded at the 95% confidence level.
Download or read book A Search for Top Quarks in Proton antiproton Collisions Using Dileptons written by Andrew James Martin and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for tt pairs in pp collisions with a center of mass energy $sqrt s$ = 1.8TeV is presented. The analysis looks for tt pairs which decayed through the chain $bar {tt}to Wsp+bWsp-bar btoellsp+bar nu bellsp-nubar b$ where one of the b quarks is explicitly identified. In a sample of 109.4 $pm$ 7.2 pb$sp{-1}$ of data, 6 tags in 4 events are found with an expected background of 1.53 $pm$.33 events. This results in an estimated production cross section of 4.6$sbsp{-3.1}{+4.4}$ pb at $msb{top}$ = 175 GeV/$csp2.$
Download or read book CP Violation written by Società italiana di fisica and published by IOS Press. This book was released on 2006 with total page 626 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dealing with the CP violation, from quarks to leptons, this publication reviews the field, from both the theoretical and experimental point of view, while planning for the experimentation at LHC and considering possible facilities for kaon, B meson and neutrino physics.
