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Title: Measurements of the Ratio of W and Z Production and the W Boson Decay Width at CDF

Abstract

We present a new method of measuring the ratio of W and Z production and de- cay (R) at the CDF experiment. We analyze 307 pb -1 of proton-antiproton collisions at the Fermilab Tevatron center-of-mass energy of 1.96 TeV. A single sample containing both W and Z boson candidates is selected by requiring at least one high-energy electron in an event with low hadronic activity. We estimate that less than one percent of our sample is made up of background events after a cut on the recoil energy. A maximum likelihood fits is performed on the missing transverse energy spectrum of the events to determine the relative rates of W and Z production in the common sample. This ratio is defined as: R = Z · → Z Γ(W → £ν) 1 Γ(W ) Br(Z → ££) We have obtained the fi result using this method for the electron channel. R = 10.55 ± 0.09(stat) ± 0.12(syst) We then extract the Branching Ratio of W → £ν using the Branching Ratio of Z → £+£- measured at LEP and a theoretical value for the ratio of the cross sections. σZ Br(W → £ν) = R · W Br(Z → £+more » £-) = 0.1054 ± 0.0016 We also obtain an indirect measurement of the W width of Γtot = 2148 ± 32 MeV. This width gives us information about all the possible decays of the W boson. The W width also constrains the sum of the CKM elements involved in W decays. We find the following value for V cs , the least constrained element: |V cs | = 1.008 ± 0.029.« less

Authors:
 [1]
  1. Univ. of Michigan, Ann Arbor, MI (United States)
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1415800
Report Number(s):
FERMILAB-THESIS-2007-83; AAT-3276123; PROQUEST-1490074231
842149
DOE Contract Number:
AC02-07CH11359
Resource Type:
Thesis/Dissertation
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats

Copic, Katherine Ann. Measurements of the Ratio of W and Z Production and the W Boson Decay Width at CDF. United States: N. p., 2007. Web. doi:10.2172/1415800.
Copic, Katherine Ann. Measurements of the Ratio of W and Z Production and the W Boson Decay Width at CDF. United States. doi:10.2172/1415800.
Copic, Katherine Ann. Thu . "Measurements of the Ratio of W and Z Production and the W Boson Decay Width at CDF". United States. doi:10.2172/1415800. https://www.osti.gov/servlets/purl/1415800.
@article{osti_1415800,
title = {Measurements of the Ratio of W and Z Production and the W Boson Decay Width at CDF},
author = {Copic, Katherine Ann},
abstractNote = {We present a new method of measuring the ratio of W and Z production and de- cay (R) at the CDF experiment. We analyze 307 pb-1 of proton-antiproton collisions at the Fermilab Tevatron center-of-mass energy of 1.96 TeV. A single sample containing both W and Z boson candidates is selected by requiring at least one high-energy electron in an event with low hadronic activity. We estimate that less than one percent of our sample is made up of background events after a cut on the recoil energy. A maximum likelihood fits is performed on the missing transverse energy spectrum of the events to determine the relative rates of W and Z production in the common sample. This ratio is defined as: R = Z · → Z Γ(W → £ν) 1 Γ(W ) Br(Z → ££) We have obtained the fi result using this method for the electron channel. R = 10.55 ± 0.09(stat) ± 0.12(syst) We then extract the Branching Ratio of W → £ν using the Branching Ratio of Z → £+£- measured at LEP and a theoretical value for the ratio of the cross sections. σZ Br(W → £ν) = R · W Br(Z → £+ £-) = 0.1054 ± 0.0016 We also obtain an indirect measurement of the W width of Γtot = 2148 ± 32 MeV. This width gives us information about all the possible decays of the W boson. The W width also constrains the sum of the CKM elements involved in W decays. We find the following value for Vcs , the least constrained element: |Vcs | = 1.008 ± 0.029.},
doi = {10.2172/1415800},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2007},
month = {Thu Mar 01 00:00:00 EST 2007}
}

Thesis/Dissertation:
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  • This thesis describes themore » $$W \to \mu\nu$$ and $$Z \to \mu\mu$$ cross-section analysis for Run 1B (1994-1995) in the D0 experiment. The sample corresponds to a total integrated luminosity of 38.3 $$pb^{-1}$$....« less
  • This dissertation reports on measurements of inclusive cross sections times branching fractions into electrons for W and Z bosons produced in pmore » $$\bar{p}$$ collisions at √s = 1.8 TeV. From an integrated luminosity of 84.5 pb -1 recorded in 1994--1995 by the D0 detector at the Fermilab Tevatron, the cross sections are measured to be σp$$\bar{p}$$ → W + X ∙ B(W → ev) = 2,310 ± 10 (stat) ± 50 (Syst) ± 100 (lum) pb and σ(p$$\bar{p}$$ → Z + X) ∙ B(Z → ee) = 221 ± 3 (stat) ± 4 (Syst) ± 10 (lum) pb. The cross section ratio R is determined to be σ(p$$\bar{p}$$ → W + X) ∙ B(W → ev)/σ(p$$\bar{p}$$ → Z + X) ∙ B(Z → ee) = 10.43 ± 0.15 (stat) ± 0.20 (syst) ± 0.10 (NLO)Λ and R is used to determine B(W → ev) = 0.1044 ± 0.0015 (stat) ± 0.0020 (syst) ± 0.0017 (theory) ± 0.0010 (NLO), Λ and , Λ w = 2.169 ± 0.031 (stat) ± 0.042 (syst) ± 0.041 (theory) ± 0.022 (NLO) GeV. The latter is used to set a 95% confidence level upper limit on the partial decay width of the W boson into non-standard model final states ΛΛ w invΛ of 0.213 GeV.« less
  • This dissertation reports on measurements of inclusive cross sections times branching fractions into electrons for W and Z bosons produced in pp collisions at ps = 1.8 TeV. From an integrated luminosity of 84.5 pb -1 recorded in 1994-1995 by the D0 detector at the Fermilab Tevatron, the cross sections are measured to be (pmore » $$\bar{p}$$ → W +X) ∙ B(W → e )= 2310 ± 10 (stat) ± 50 (syst) ± 100 (lum) pb and (p$$\bar{p}$$ → Z +X) ∙ B(Z → ee)= 221 ± 3 (stat) ± 4 (syst) ± 10 (lum) pb. The cross section ratio R is determined to be (p$$\bar{p}$$ → W+X) B(W → e )= (p$$\bar{p}$$ → Z + X) ∙ B(Z → ee) = 10.43 ± 0.15 (stat) 0.20 (syst) ± 0.10 (NLO), and R is used to determine B(W → ev ) = 0.1044 ± 0.0015 (stat) ± 0.0020 (syst) 0.0017 (theory) ± 0.0010 (NLO), and W = 2.169 ± 0.031 (stat) ± 0.042 (syst) 0.041 (theory) ± 0.022 (NLO) GeV. The latter is used to set a 95% confidence level upper limit on the partial decay width of the W boson into non-standard model final states, $$inv\atop{W}$$ , of 0.213 GeV.« less
  • The theory that describes the fundamental particle interactions is called the Standard Model, which is a gauge field theory that comprises the Glashow-Weinberg-Salam model [1, 2, 3] of the weak and electromagnetic interactions and quantum chromodynamics (QCD) [4, 5, 6], the theory of the strong interactions. The discovery of the W [7, 8] and Z [9, 10] bosons in 1983 by the UA1 and UA2 collaborations at the CERN pmore » $$\bar{p}$$ collider provided a direct confirmation of the unification of the weak and electromagnetic interactions. Since then, many experiments have refined our understanding of the characteristics of the W and Z bosons.« less
  • For many measurements at hadron colliders, such as cross sections and branching ratios, the uncertainty of the integrated luminosity is an important contribution to the error of the final result. In 1997, the ETH Zurich group proposed a new approach to determine the integrated luminosity via a counting measurement of the W and Z bosons through their decays to leptons. In this thesis this proposal has been applied on real data as well as on simulation for a future experiment.