Measurement of High-Q^2 Charged-Current e^+p Deep Inelastic Scattering Cross Sections at HERA

TL;DR

This paper reports precise measurements of charged-current deep inelastic scattering cross sections at HERA, confirming the Standard Model predictions and providing new estimates for the W boson mass and Fermi constant.

Contribution

The study provides the first detailed measurement of $d\sigma/dQ^2$, $d\sigma/dx$, and $d\sigma/dy$ for high Q^2 in e^+p scattering, and extracts fundamental electroweak parameters from the data.

Findings

Cross section $d\sigma/dQ^2$ decreases by a factor of 50,000 from 280 to 30,000 GeV^2.

Data agree well with Standard Model predictions including quark and antiquark contributions.

Estimated W boson mass as $80.8^{+4.9}_{-4.5}$ GeV from the fit.

Abstract

The e^+p charged-current deep inelastic scattering cross sections, $d\sigma/dQ^2$ for Q^2 between 200 and 60000 GeV^2, and $d\sigma/dx$ and $d\sigma/dy$ for Q^2 > 200 GeV^2, have been measured with the ZEUS detector at HERA. A data sample of 47.7 pb^-1, collected at a center-of-mass energy of 300 GeV, has been used. The cross section $d\sigma/dQ^2$ falls by a factor of about 50000 as Q^2 increases from 280 to 30000 GeV^2. The double differential cross section $d^2\sigma/dxdQ^2$ has also been measured. A comparison between the data and Standard Model (SM) predictions shows that contributions from antiquarks ($\bar{u}$ and $\bar{c}$) and quarks (d and s) are both required by the data. The predictions of the SM give a good description of the full body of the data presented here. A comparison of the charged-current cross section $d\sigma/dQ^2$ with the recent ZEUS results for neutral-current scattering shows that the weak and electromagnetic forces have similar strengths for Q^2 above $M^2_W, M^2_Z$. A fit to the data for $d\sigma/dQ^2$ with the Fermi constant $G_F$ and $M_W$ as free parameters yields $G_F = (1.171 \pm 0.034 (stat.) ^{+0.026}_{-0.032} (syst.) ^{+0.016}_{-0.015} (PDF)) \times 10^{-5} GeV^{-2}$ and $M_W = 80.8 ^{+4.9}_{-4.5} (stat.) ^{+5.0}_{-4.3} (syst.) ^{+1.4}_{-1.3} (PDF) GeV$. Results for $M_W$, where the propagator effect alone or the SM constraint between $G_F$ and $M_W$ have been considered, are also presented.