{ital R}{sub {ital b}} in supersymmetric models

Journal Article · Sun Oct 01 04:00:00 EDT 1995 · Physical Review, D

DOI:https://doi.org/10.1103/PhysRevD.52.4116· OSTI ID:249543

Wang, X; Lopez, J L ^[1]; Nanopoulos, D V ^[1]

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1. Center for Theoretical Physics, Department of Physics, Texas A&M University, College Station, Texas 77843-4242 (United States)

We compute the supersymmetric contribution to {ital R}{sub {ital b}}{equivalent_to}{Gamma}({ital Z}{r_arrow}{ital b{bar b}})/{Gamma}({ital Z}{r_arrow} hadrons) in a variety of supersymmetric models. In the context of supergravity models with universal soft supersymmetry breaking and radiative electroweak breaking we find {ital R}{sub {ital b}}{sup SUSY}{approx_lt}0.0004, which does not shift significantly the standard model prediction ({ital R}{sub {ital b}}{sup SM}=0.2157 for {ital m}{sub {ital t}}=175 GeV; {ital R}{sub {ital b}}{sup expt}=0.2204{plus_minus}0.0020). We also compute {ital R}{sub {ital b}} in the minimal supersymmetric standard model (MSSM), and delineate the region of parameter space which yields interestingly large values of {ital R}{sub {ital b}}. This region entails light charginos and top squarks, but is {ital strongly} restricted by the {ital combined} constraints from {ital B}({ital b}{r_arrow}{ital s}{gamma}) and a not-too-large invisible top-quark branching ratio: only a few percent of the points with {ital R}{sub {ital b}}{sup SUSY}{gt}0.0020 (1{sigma}) are allowed.

• Research Organization: Texas A&M Research Foundation
• DOE Contract Number: FG05-91ER40633
• OSTI ID: 249543
• Journal Information: Physical Review, D, Journal Name: Physical Review, D Journal Issue: 7 Vol. 52; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
BOTTOMONIUM
HADRONS
STANDARD MODEL
SUPERGRAVITY
SUPERSYMMETRY
SYMMETRY BREAKING
WEAK HADRONIC DECAY
Z NEUTRAL BOSONS