A measurement of the proton structure function
F
2(
x,
Q
2) is reported for momentum transfers squared
Q
2 between 4.5 GeV
2 and 1600 GeV
2 and for Bjorken
x between 1.8 × 10
−14 and 0.13 using data ...collected by the HERA experiment H1 in 1993. It is observed that
F
2 increases significantly with decreasing
x, confirming our previous measurement made with one tenth of the data available in this analysis. The
Q
2 dependence is approximately logarithmic over the full kinematic range covered. The subsample of deep inelastic events with a large pseudo-rapidity gap in the hadronic energy flow close to the proton remnant is used to measure the “diffractive” contribution to
F
2.
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IJS, IMTLJ, KILJ, KISLJ, NUK, SBCE, UL, UM, UPCLJ, UPUK
A search for contributions to the reaction ep --> epi(0)N* from photon-odderon fusion in the photoproduction regime at HERA is reported, at an average photon-proton centre-of-mass energy = 215 GeV. ...The measurement proceeds via detection of the pi(0) decay photons, a leading neutron from the N* decay, and the scattered electron. No pi(0) signal is observed and an upper limit on the cross section for the photon-odderon fusion process of sigma(gammap --> pi(0)N*) < 49 nb at the 95% confidence level is derived, integrated over the experimentally accessible range of the squared four-momentum transfer at the nucleon vertex 0.02 < < 0.3 GeV2. This excludes a recent prediction from a calculation based on a non-perturbative QCD model of a photon-odderon fusion cross section above 200 nb. (C) 2002 Elsevier Science B.V. All rights reserved.
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IJS, IMTLJ, KILJ, KISLJ, NUK, SBCE, UL, UM, UPCLJ, UPUK
A measurement of the inclusive cross section for the deep-inelastic scattering of positrons off protons at HERA is presented at momentum transfers 8.5 ≤
Q
2 ≤ 35 GeV
2 and large inelasticity <
y> = ...0.7, i.e. for the Bjorken-
x range 0.00013 ≤
x ≤ 0.00055. Using a next-to-leading order QCD fit to the structure function
F
2 at lower
y values, the contribution of
F
2 to the measured cross section at high
y is calculated and, by subtraction, the longitudinal structure function
F
L
is determined for the first time with an average value of
F
L
= 0.52 ± 0.03 (statt)
−0.22
+0.25 (syst) at
Q
2 = 15.4 GeV
2 and
x = 0.000243.
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IJS, IMTLJ, KILJ, KISLJ, NUK, SBCE, UL, UM, UPCLJ, UPUK
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