, Volume 12, Issue 3, pp 411-428

Measurement of high- $Q^2$ charged-current $e^+p$ deep inelastic scattering cross sections at HERA


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 double-differential 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 ( $\overlineu$ and $\overline c$ ) and quarks (d ands) 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 $G_F = \left( 1.171 {\pm 0.034} \,{\rm (stat.)} ^{+0.026}_{-0.032} \,{\rm (syst.)} ^{+0.016}_{-0.015} \,{\rm (PDF)} \right)\times10^{-5}\,{\rm GeV^{-2}}$ and $M_W = 80.8 ^{+4.9}_{-4.5} \,{\rm (stat.)} ^{+5.0}_{-4.3} \,{\rm (syst.)} ^{+1.4}_{-1.3} \,{\rm (PDF) GeV}$ . 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.

Received: 7 July 1999 / Published online: 21 December 1999