rpp2010-rev-z-boson - 1 THE Z BOSON Revised March 2009 by M...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
– 1– THE Z BOSON Revised March 2009 by M. Gr¨unewald (U. College Dublin and U. Ghent), and A. Gurtu (Tata Inst.). Precision measurements at the Z -boson resonance using electron–positron colliding beams began in 1989 at the SLC and at LEP. During 1989–95, the four LEP experiments (ALEPH, DELPHI, L3, OPAL) made high-statistics studies of the pro- duction and decay properties of the Z . Although the SLD experiment at the SLC collected much lower statistics, it was able to match the precision of LEP experiments in determining the effective electroweak mixing angle sin 2 θ W and the rates of Z decay to b - and c -quarks, owing to availability of polarized electron beams, small beam size, and stable beam spot. The Z -boson properties reported in this section may broadly be categorized as: The standard ‘lineshape’ parameters of the Z con- sisting of its mass, M Z , its total width, Γ Z , and its partial decay widths, Γ(hadrons), and Γ( ) where = e, μ, τ, ν ; Z asymmetries in leptonic decays and extraction of Z couplings to charged and neutral leptons; The b - and c -quark-related partial widths and charge asymmetries which require special techniques; Determination of Z decay modes and the search for modes that violate known conservation laws; Average particle multiplicities in hadronic Z decay; Z anomalous couplings. The effective vector and axial-vector coupling constants describing the Z -to-fermion coupling are also measured in p ¯ p and ep collisions at the Tevatron and at HERA. The corresponding cross-section formulae are given in Section 39 (Cross-section formulae for specific processes) and Section 16 (Structure Functions) in this Review . In this minireview, we concentrate on the measurements in e + e collisions at LEP and SLC. The standard ‘lineshape’ parameters of the Z are deter- mined from an analysis of the production cross sections of CITATION: K. Nakamura et al. (Particle Data Group), JPG 37 , 075021 (2010) (URL: http://pdg.lbl.gov) July 30, 2010 14:34
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
– 2– these final states in e + e collisions. The Z ν ν ( γ ) state is identified directly by detecting single photon production and indirectly by subtracting the visible partial widths from the total width. Inclusion in this analysis of the forward-backward asymmetry of charged leptons, A (0 , ) FB , of the τ polarization, P ( τ ), and its forward-backward asymmetry, P ( τ ) fb , enables the separate determination of the effective vector ( g V ) and ax- ial vector ( g A ) couplings of the Z to these leptons and the ratio ( g V / g A ), which is related to the effective electroweak mixing angle sin 2 θ W (see the “Electroweak Model and Constraints on New Physics” review). Determination of the b - and c -quark-related partial widths and charge asymmetries involves tagging the b and c quarks for which various methods are employed: requiring the pres- ence of a high momentum prompt lepton in the event with high transverse momentum with respect to the accompanying jet; impact parameter and lifetime tagging using precision ver-
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern