Measurements of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>R</mi></math> and a Search for Heavy-Quark Production in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup></mrow><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> Annihilation at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mrow><mi>s</mi></mrow></msqrt><mo>=</mo><mn>50</mn><mn></mn><mi> </mi><mi mathvariant="normal">and</mi><mi> </mi><mn>52</mn></math> GeV

doi:10.1103/PhysRevLett.60.93

Measurements of $R$ and a Search for Heavy-Quark Production in $e^{+} e^{-}$ Annihilation at $\sqrt{s} = 50 and 52$ GeV

H. Sagawa et al. (The AMY Collaboration)

Phys. Rev. Lett. 60, 93 – Published 11 January 1988

Abstract

The ratio $R$ of the cross section for $e^{+} e^{-}$ annihilation into hadronic final states to the QED cross section for muon-pair production is measured to be 4.34±0.45±0.30 and 4.23±0.20±0.21 at c.m. energies of 50 and 52 GeV, respectively. From these values of $R$ and an analysis of the event shapes we deduce a 95%-confidence-level upper limit for the production rate of new heavy charge $+ \frac{2}{3} e$ or $- \frac{1}{3} e$ quarks to be 0.19 units of $R$ .