The cross-section for deeply virtual Compton scattering in the reaction ep→eγp has been measured with the ZEUS detector at HERA using integrated luminosities of 95.0 pb−1 of e+p and 16.7 pb−1 of e−p ...collisions. Differential cross-sections are presented as a function of the exchanged-photon virtuality, Q2, and the centre-of-mass energy, W, of the γ∗p system in the region 5<Q2<100 GeV2 and 40<W<140 GeV. The measured cross-sections rise steeply with increasing W. The measurements are compared to QCD-based calculations.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A
bstract
The cross sections for inelastic photoproduction of
J/ψ
and
ψ
′ mesons have been measured in
ep
collisions with the ZEUS detector at HERA, using an integrated luminosity of 468 pb
−1
...collected in the period 1996–2007. The
ψ
′ to
J/
ψ cross section ratio was measured in the range 0
.
55
< z <
0
.
9 and 60
< W <
190 GeV as a function of
W
,
z
and
p
T
. Here
W
denotes the photon-proton centre-of-mass energy,
z
is the fraction of the incident photon energy carried by the meson and
p
T
is the transverse momentum of the meson with respect to the beam axis. The
J/ψ
cross sections were measured for 0
.
1
< z <
0
.
9, 60
< W <
240 GeV and
p
T
>
1 GeV. Theoretical predictions within the non-relativistic QCD framework including NLO colour-singlet and colour-octet contributions were compared to the data, as were predictions based on the
k
T
-factorisation approach.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Abstract The photoproduction of D ^sup ±^ mesons has been measured with the ZEUS detector at HERA at three different ep ...centre-of-mass energies, ..., of 318, 251 and 225 GeV. For each data set, D ^sup ±^ mesons were required to have transverse momentum, p ^sub T^^sup D^, and pseudo-rapidity, eta ^sup D^, in the ranges 1.9 < p ^sub T^^sup D^ < 20 GeV and |eta ^sup D^| < 1.6. The events were required to have a virtuality of the incoming photon, Q ^sup 2^, of less than 1 GeV^sup 2^. The dependence on ... was studied by normalising to the high-statistics measurement at ... GeV. This led to the cancellation of a number of systematic effects both in data and theory. Predictions from next-to-leading-order QCD describe the ... dependence of the data well.
The exclusive deep inelastic electroproduction of ψ(2S) and J/ψ(1S) at an ep centre-of-mass energy of 317 GeV has been studied with the ZEUS detector at HERA in the kinematic range 2<Q2<80 GeV2, ...30<W<210 GeV and |t|<1 GeV2, where Q2 is the photon virtuality, W is the photon–proton centre-of-mass energy and t is the squared four-momentum transfer at the proton vertex. The data for 2<Q2<5 GeV2 were taken in the HERA I running period and correspond to an integrated luminosity of 114 pb−1. The data for 5<Q2<80 GeV2 are from both HERA I and HERA II periods and correspond to an integrated luminosity of 468 pb−1. The decay modes analysed were μ+μ− and J/ψ(1S)π+π− for the ψ(2S) and μ+μ− for the J/ψ(1S). The cross-section ratio σψ(2S)/σJ/ψ(1S) has been measured as a function of Q2,W and t. The results are compared to predictions of QCD-inspired models of exclusive vector-meson production.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A simultaneous fit of parton distribution functions (PDFs) and electroweak parameters to HERA data on deep inelastic scattering is presented. The input data are the neutral current and charged ...current inclusive cross sections which were previously used in the QCD analysis leading to the HERAPDF2.0 PDFs. In addition, the polarization of the electron beam was taken into account for the ZEUS data recorded between 2004 and 2007. Results on the vector and axial-vector couplings of the Z boson to u- and d-type quarks, on the value of the electroweak mixing angle and the mass of the W boson are presented. The values obtained for the electroweak parameters are in agreement with Standard Model predictions.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The high-precision HERA data allows searches up to TeV scales for beyond the Standard Model contributions to electron–quark scattering. Combined measurements of the inclusive deep inelastic cross ...sections in neutral and charged current ep scattering corresponding to a luminosity of around 1 fb−1 have been used in this analysis. A new approach to the beyond the Standard Model analysis of the inclusive ep data is presented; simultaneous fits of parton distribution functions together with contributions of “new physics” processes were performed. Results are presented considering a finite radius of quarks within the quark form-factor model. The resulting 95% C.L. upper limit on the effective quark radius is 0.43⋅10−16 cm.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The photoproduction of isolated photons has been measured in diffractive events recorded by the ZEUS detector at HERA. Cross sections are evaluated in the photon transverse-energy and pseudorapidity ...ranges 5<ETγ<15 GeV and −0.7<ηγ<0.9, inclusively, and also with a jet with transverse energy and pseudorapidity in the ranges 4<ETjet<35 GeV and −1.5<ηjet<1.8, using a total integrated electron-proton luminosity of 456 pb−1. A number of kinematic variables were studied and compared to predictions from the rapgap Monte Carlo model. An excess of data is observed above the rapgap predictions for zPmeas>0.9, where zPmeas is the fraction of the longitudinal momentum of the colorless “Pomeron” exchange that is transferred to the photon-jet final state, giving evidence for direct Pomeron interactions.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Dijet differential cross sections for the reaction e+p→e++jet+jet+X in the photoproduction regime have been measured with the ZEUS detector at HERA using an integrated luminosity of 42.7 pb−1. The ...cross sections are given for photon–proton centre-of-mass energies in the range 134<W<277 GeV. The differential cross sections as a function of the dijet mass, Mjj, and of the dijet angular variables have been measured for 47<Mjj<160 GeV and compared to next-to-leading-order QCD calculations. The dijet events in the region 75<Mjj<100 GeV have been used to derive a 95% C.L. upper limit on the cross section for Z0 photoproduction of σe+p→e+Z0X<5.9 pb. Upper limits on the photoproduction of new heavy resonances decaying into two jets are also presented for masses in the range between 60 GeV and 155 GeV.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A search for a narrow baryonic state in the pKS0 and p‾KS0 system has been performed in ep collisions at HERA with the ZEUS detector using an integrated luminosity of 358pb−1 taken in 2003–2007. The ...search was performed with deep inelastic scattering events at an ep centre-of-mass energy of 318GeV for exchanged photon virtuality, Q2, between 20 and 100GeV2. Contrary to evidence presented for such a state around 1.52 GeV in a previous ZEUS analysis using a sample of 121 pb−1 taken in 1996–2000, no resonance peak was found in the p(p‾)KS0 invariant-mass distribution in the range 1.45–1.7 GeV. Upper limits on the production cross section are set.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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