Ratios of W±γ and Zγ cross sections: New tools in probing the weak boson sector at the Fermilab Tevatron

The ratios Rγ,l=B(Z→l+l-)σ(Zγ)B(W→lν) σ(W±γ), Rγ,ν=B(Z→ν̄ν) σ(Zγ)B(W→lν)σ(W±γ), RWγ= σ(W±γ)σ(W±), and RZγ=σ(Zγ) σ(Z) are studied as tools to probe the electroweak boson self-interactions. As a function of the minimum photon transverse momentum, Rγ,l and Rγ, ν are found to directly reflect the radiation zero present in W±γ production in the standard model. All four ratios are sensitive to anomalous WWγ and/or ZZγZγγ couplings. The sensitivity of the cross-section ratios to the cuts imposed on the final-state particles, as well as the systematic uncertainties resulting from different parametrizations of parton distribution functions, the choice of the factorization scale Q2, and from higher-order QCD corrections, are explored. Taking into account these uncertainties, sensitivity limits for anomalous three gauge boson couplings, based on a measurement of the cross-section ratios with an integrated luminosity of 25 pb-1 at the Fermilab Tevatron, are estimated.