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

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.

Note:

34 pages including 10 figures and 6 tables: added tables for correlated and uncorrelated systematic uncertainties and fixed the total systematic uncertainty for dsigma/dxdQ2 (Table 4 and Figs.7-8): erratum submitted to Eur. Phys. J Report-no: DESY-99-059 Journal-ref: Eur.Phys.J. C12 (2000) 411-428

positron p: colliding beams
positron p: deep inelastic scattering
charged current
momentum transfer: high
differential cross section: momentum transfer
x-dependence
nucleon: structure function
quark: sea
electroweak interaction: validity test
coupling constant

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