Download or read book Search for WZ ZZ Production in the Lepton s MET Jets Channel with the CDF Experiment at the Tevatron Collider written by and published by . This book was released on 2014 with total page 233 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis we present a search for the WZ and ZZ production in a final state ("W+2 jets") with a leptonically-decaying W and two energetic jets. We use the full dataset (+"Ldt = 8:9 fb-1) recorded with the CDF detector at Fermilab. The challenge consists in extracting the small Z-hadronic peak from the large amount of background processes. Those processes also include the WW, whose hadronic peak cannot be distinguished from the Z peak, due to the poor calorimeter resolution. In the past such a signature was used to measure the diboson cross section, which is highly dominated by the WW cross section.
Download or read book Search for ZW ZZ Going to Lepton Lepton Jets Production in Proton proton Collisions at CDF written by Wesley Ketchum and published by . This book was released on 2012 with total page 235 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Standard Model of particle physics describes weak interactions mediated by massive gauge bosons that interact with each other in well-defined ways. Observations of the production and decay of WW, WZ, and ZZ boson pairs are an opportunity to check that these self-interactions agree with the Standard Model predictions. Furthermore, final states that include quarks are very similar to the most prominent final state of Higgs bosons produced in association with a W or Z boson. Diboson production where WW is a significant component has been observed at the Tevatron collider in semi-hadronic decay modes. We present a search for ZW and ZZ production in a final state containing two charged leptons and two jets using 8.9 fb−1 of data recorded with the CDF detector at the Tevatron. We select events by identifying those that contain two charged leptons, two hadronic jets, and low transverse missing energy ( E /T ). We increase our acceptance by using a wide suite of high- pT lepton triggers and by relaxing many lepton identification requirements. We develop a new method for calculating corrections to jet energies based on whether the originating parton was a quark or gluon to improve the agreement between data and the Monte Carlo simulations used to model our diboson signal and dominant backgrounds. We also make use of neural-network-based discriminants that are trained to pick out jets originating from b quarks and light-flavor quarks, thereby increasing our sensitivity to Z → bb ̄ and W/Z → qq ̄' decays, respectively. The number of signal events is extracted through a simultaneous fit to the dijet mass spectrum in three channels: a heavy-flavor tagged channel, a light-flavor tagged channel, and an untagged channel. We measure σZW/ZZ = 2.5+2.0-1.0 pb, which is consistent with the SM cross section of 5.1 pb. We establish an upper limit on the cross section of σZW/ZZ
Download or read book W Z Jets Production at the Tevatron written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Both the D0 and CDF experiments at Fermilab Tevatron collider at[radical]s= 1.8 TeV have accumulated over 50pb[sup -1] of data. Each experiment collected more than 50,000 W[yields] l+v and 5000 Z[yields] l+[bar l] candidates for each lepton species (e and[mu]). Using this large data sample of W and Z candidates, the two experiments are actively testing perturbative QCD predictions. Among the studies that are in progress, preliminary results of W/Z+jets characteristics, multiplicity distributions of associated jets, and a study on the determination of the strong coupling constant using the ratio of the W+1 jet to W+ 0 jet cross sections are presented.
Download or read book M morandum sur le boycottage written by and published by . This book was released on 1932 with total page 31 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Search for WZ ZZ Production with Missing Transverse Energy and B Jets at CDF written by and published by . This book was released on 2013 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: Observation of diboson processes at hadron colliders is an important milestone on the road to discovery or exclusion of the standard model Higgs boson. Since the decay processes happen to be closely related, methods, tools, and insights obtained through the more common diboson decays can be incorporated into low-mass standard model Higgs searches. The combined WW + WZ + ZZ diboson cross section has been measured at the Tevatron in hadronic decay modes. In this thesis we take this one step closer to the Higgs by measuring just the WZ + ZZ cross section, exploiting a novel arti cial neural network based b-jet tagger to separate the WW background. The number of signal events is extracted from data events with large ET using a simultaneous t in events with and without two jets consistent with B hadron decays. Using 5:2 fb-1 of data from the CDF II detector, we measure a cross section of (p $\bar{p}$ 2!WZ, ZZ) = 5:8+3.6 -3.0 pb, in agreement with the standard model.
Download or read book CDF Top Results in the Lepton Jets Channel written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Results from the 1992--1993 Tevatron run (ran IA) top search at CDF in the lepton+jets channel are reported. The jet-vertexing algorithm tags 6 events on a background of 2.3 [plus-minus] 0.3 events in the W+ [ge] 3 jets data sample, and the soft lepton analysis finds T events on a background of 3.1 [plus-minus] 0.3 events in the same data sample. Jet-vertex and soft-lepton tag correlations are described. Also given are the expected and observed number of tags in the Z+mulitjet control sample.
Download or read book Search for WZ ZZ Production with Missing Transverse Energy and B Jets at CDF written by Stephen Thomas Poprocki and published by . This book was released on 2013 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Study of W Z Intermediate Bosons Associated Production with the CDF Experiment at the Tevatron Collider written by and published by . This book was released on 2007 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Search for WZ ZZ Production with MET Jets with b Enhancement at sqrt s written by and published by . This book was released on 2011 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Diboson production (WW + WZ + ZZ) has been observed at the Tevatron in hadronic decay modes dominated by the WW process. This paper describes the measurement of the cross section of WZ and ZZ events in final states with large E{sub T} and using b-jet identification as a tool to suppress WW contributions. Due to the limited energy resolution, we cannot distinguish between partially hadronic decays of WZ and ZZ, and we measure the sum of these processes. The number of signal events is extracted using a simultaneous fit to the invariant mass distribution of the two jets for events with two b-jet candidates and events without two b-jet candidates. We measure a cross section [sigma](p{bar p} 2!WZ, ZZ) = 5.8{sub -3.0}{sup +3.6} pb, in agreement with the standard model.
Download or read book Jets in CDF written by and published by . This book was released on 1991 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the 1988/89 Tevatron Collider run the CDF experiment collected 4.0 {plus minus} 0.3 pb−1 of proton-antiproton interactions at a center-of-mass collision energy currently available in the laboratory and gives us a unique opportunity for studying Quantum Chromodymanics (QCD) processes at the highest available energies. We report results from various QCD studies performed with this data. 11 refs., 8 figs.
Download or read book CERN Courier written by and published by . This book was released on 2011 with total page 574 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Electroweak and Top Physics at CDF in Run II written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The CDF experiment at the Tevatron has used p[bar p] collisions at[radical]s= 1.96 TeV to measure the production cross sections of W and Z bosons using several leptonic final states. An indirect measurement of the W width and the ratio of tau and electron electroweak couplings have been extracted. The forward-backward charge asymmetry, A[sub FB], in Drell-Yan dilectron production has been measured up to an invariant mass of 600 GeV/c[sup 2]. CDF has also started looking for WW production in the dilepton channel, WW[prime][yields] ll[prime]vv, with the aim of measuring its cross section and derive limits on the anomalous WWZ and WW[gamma] couplings. The presence of a top quark signal in the Tevatron data has been reestablished by measuring the top quark pair production cross section in the dilepton channel, t[bar t][yields] WbW[bar b][yields][bar l]v[sub l]bl[prime][bar v][sub l[prime]][bar b] and in the lepton plus jets channel, t[bar t][yields] WbW[bar b][yields] q[bar q]lbl[bar b][sub l][bar b]+[bar l]v[sub l]bq[bar q][prime][bar b]. A pre-tagged lepton plus jets sample has also been used to reconstruct the top quark mass.
Download or read book Diboson Production at the Tevatron written by and published by . This book was released on 2008 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the latest results on the production of WW, WZ, Wgamma, Zgamma and ZZ events at the Fermilab Tevatron Collider. The results are based on the analyses of 0.2 - 2 /fb of data collected in p pbar collisions at sqrt(s) = 1.96 TeV by CDF and DO experiments during the Tevatron Run II. Analyses of the diboson production processes provide crucial test of the Standard Model, directly probing its predictions on the Trilinear Gauge Couplings.
Download or read book Studying Z Jet Production in Proton antiproton Collisions at u221A s written by and published by . This book was released on 2009 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: The production of jets in association with a Z/?* boson is an example of an important class of processes at hadron colliders, namely vector boson + jet (V + jet) production. Comparisons of measurements of this class of processes with theory predictions constitute an important, fundamental test of the Standard Model of particle physics, and of the theory of QCD in particular. While having a smaller cross section than other V +jet processes, Z/?*(→ e+e-) + jets production, with Z/?* → e+e-/?+?-, has a distinct experimental signature allowing for measurements characterized by low backgrounds and a direct, precise measurement of the properties of the decay products of the Z/?* boson. In this thesis, several new measurements of the properties of jets produced in association with a Z/?* boson in p$ar{p}$ collisions at √s = 1.96 TeV are presented. The cross section for Z/?*(→ e+e-) + N jet production (N ≤ 3) is measured, differential in the transverse momentum of the Nth jet in the event, normalized to the inclusive Z/?* cross section. Also, the cross section for Z/?*(→e+e-) + N jets (N ≥ 1) is measured, differential in the difference in azimuthal angle between the di-electron system and any jet in the event, normalized to unity. The data used in the measurements were collected by the D0 experiment located at the Tevatron Collider of the Fermi National Accelerator Laboratory and correspond to an integrated luminosity of 1.04 fb-1. The measured jet transverse momentum spectra are compared with the predictions of perturbative calculations at the next-to-leading order in the strong coupling constant. Given the low sensitivity of the calculations to model parameters, these comparisons represent a stringent test of perturbative QCD. One of the main goals currently being pursued in particle physics is the discovery of the only particle predicted by the Standard Model which has so far no been detected experimentally, namely the Higgs boson. It is assumed that the ATLAS and CMS experiments located at the Large Hadron Collider (LHC), a proton-proton collider at √s = 14 TeV, will be able to detect the Higgs boson, or rule out its existence, within the next few years. The collisions delivered by the LHC will also be used to perform a long range of searches for other new particles, for instance particles predicted by models based on the principle of supersymmetry. The associated production of vector bosons with jets has relatively large production rates at the LHC and can produce a long list of different final states which can include charged leptons, missing transverse energy, as well as light- and heavy-flavour jets. This makes V + jet production a major source of background events to many searches for new particles. Most techniques used for estimating the expected number of background events to searches rely on passing the stable final-state particles of simulated hadron collisions generated using a so-called event generator code, through a simulation of the experimental detector system. The development of event generators which are capable of reliably predicting the properties of jets produced in association with a core process, e.g. the production of a vector boson, has been the subject of a large amount of research activity during the last ten years. These efforts have led to the appearance of the CKKW and MLM algorithms which are implemented in several event generators, among them SHERPA and ALPGEN + PYTHIA. The large data sample collected by the D0 experiment during Run II offers an excellent opportunity for validating these new event generators against experimental measurements of V + jet production. As argued above, the Z/?*(→ e+e-) + jets process offers the combination of a clean experimental signature and large production rates, making it the process of choice for these studies.
Download or read book Study of the ZZ Diboson Production at CDF II written by and published by . This book was released on 2013 with total page 197 pages. Available in PDF, EPUB and Kindle. Book excerpt: The subject of this Thesis is the production of a pair of massive Z vector bosons in the proton antiproton collisions at the Tevatron, at the center-of-mass energy √s = 1.96 TeV. We measure the ZZ production cross section in two different leptonic decay modes: into four charged leptons (e or [mu]) and into two charged leptons plus two neutrinos. The results are based on the whole dataset collected by the Collider Detector at Fermilab (CDF), corresponding to 9.7 fb-1 of data. The combination of the two cross section measurements gives (p$\bar{p}$→ZZ) = 1.38+0.28 -0.27 pb, and is the most precise ZZ cross section measurement at the Tevatron to date. We further investigate the four lepton final state searching for the production of the scalar Higgs particle in the decay H →ZZ(*) →lll'l'. No evidence of its production has been seen in the data, hence was set a 95% Confidence Level upper limit on its production cross section as a function of the Higgs particle mass, mH, in the range from 120 to 300 GeV/c2.
Download or read book Highlights from written by and published by . This book was released on 1992 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: The D0 Experiment is a new, large multipurpose experiment at the Tevatron Proton-Antiproton Collider at the Fermi National Accelerator Laboratory. From the analysis of data taken during August--October, 1992, a selection of preliminary physics results will be given on inclusive jet production, direct photon production, the production and decay properties of the W and Z bosons, the search for the top quark in the dilepton and lepton + jets channels, B physics and searches for new particles.
Download or read book First Search at CDF for the Higggs Boson Decaying to a W Boson Pair in Proton antiproton Collisions at the Center of mass Energy of 1 96 TeV written by Shan-Huei S. Chuang and published by . This book was released on 2007 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:
