A combination is presented of the inclusive deep inelastic cross sections measured by the H1 and ZEUS Collaborations in neutral and charged current unpolarised
e
±
p
scattering at HERA during the ...period 1994-2000. The data span six orders of magnitude in negative four-momentum-transfer squared,
Q
2
, and in Bjorken
x
. The combination method used takes the correlations of systematic uncertainties into account, resulting in an improved accuracy. The combined data are the sole input in a NLO QCD analysis which determines a new set of parton distributions, HERAPDF1.0, with small experimental uncertainties. This set includes an estimate of the model and parametrisation uncertainties of the fit result.
The reduced cross sections for e super(+)p deep inelastic scattering have been measured with the ZEUS detector at HERA at three different center-of-mass energies, 318, 251 and 225 GeV. The cross ...sections, measured double differentially in Bjorken x and the virtuality, Q super(2), were obtained in the region 0.13 < or = y < or = 0.75, where y denotes the inelasticity and 5 < or = Q super(2) < or = 110 GeV super(2). The proton structure functions F sub(2) and F sub(L) were extracted from the measured cross sections.
The production of beauty and charm quarks in ep interactions has been studied with the ZEUS detector at HERA for exchanged four-momentum squared 5 < Q^2 < 1000 GeV^2 using an integrated luminosity of ...354 pb^{-1}. The beauty and charm content in events with at least one jet have been extracted using the invariant mass of charged tracks associated with secondary vertices and the decay-length significance of these vertices. Differential cross sections as a function of Q^2, Bjorken x, jet transverse energy and pseudorapidity were measured and compared with next-to-leading-order QCD calculations. The beauty and charm contributions to the proton structure functions were extracted from the double-differential cross section as a function of x and Q^2. The running beauty-quark mass, m_b at the scale m_b, was determined from a QCD fit at next-to-leading order to HERA data for the first time and found to be 4.07 \pm 0.14 (fit} ^{+0.01}_{-0.07} (mod.) ^{+0.05}_{-0.00} (param.) ^{+0.08}_{-0.05} (theo) GeV.
Measurements of neutral current cross sections for deep inelastic scattering in e+p collisions at HERA with a longitudinally polarized positron beam are presented. The single-differential ...cross-sections dσ/dQ2, dσ/dx and dσ/dy and the reduced cross section σ˜ are measured in the kinematic region Q2>185 GeV2 and y<0.9, where Q2 is the four-momentum transfer squared, x the Bjorken scaling variable and y the inelasticity of the interaction. The measurements are performed separately for positively and negatively polarized positron beams. The measurements are based on an integrated luminosity of 135.5 pb-1 collected with the ZEUS detector in 2006 and 2007 at a center-of-mass energy of 318 GeV. The structure functions F˜3 and F3γZ are determined by combining the e+p results presented in this paper with previously published e-p neutral current results. The asymmetry parameter A+ is used to demonstrate the parity violation predicted in electroweak interactions. The measurements are well described by the predictions of the Standard Model.
Production of exclusive dijets in diffractive deep inelastic
e
±
p
scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 372 pb
-
1
. The measurement was ...performed for
γ
∗
–
p
centre-of-mass energies in the range
90
<
W
<
250
GeV
and for photon virtualities
Q
2
>
25
GeV
2
. Energy flows around the jet axis are presented. The cross section is presented as a function of
β
and
ϕ
, where
β
=
x
/
x
I
P
,
x
is the Bjorken variable and
x
I
P
is the proton fractional longitudinal momentum loss. The angle
ϕ
is defined by the
γ
∗
–dijet plane and the
γ
∗
–
e
±
plane in the rest frame of the diffractive final state. The
ϕ
cross section is measured in bins of
β
. The results are compared to predictions from models based on different assumptions about the nature of the diffractive exchange.
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