A search for pentaquarks decaying to Ξ−π− (Ξ−π+) and corresponding antiparticles has been performed with the ZEUS detector at HERA. The data sample consists of deep inelastic ep scattering events at ...centre-of-mass energies of 300 and 318 GeV, and corresponds to 121 pb−1 of integrated luminosity. A clear signal for Ξ0(1530)→Ξ−π+ was observed. However, no signal for any new baryonic state was observed at higher masses in either the Ξ−π− or Ξ−π+ channels. The searches in the antiparticle channels were also negative. Upper limits on the ratio of a possible Ξ3/2−− (Ξ3/20) signal to the Ξ0(1530) signal were set in the mass range 1650–2350 MeV.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Bose–Einstein correlations of charged and neutral kaons have been measured in e±p deep inelastic scattering with an integrated luminosity of 121 pb−1 using the ZEUS detector at HERA. The two-particle ...correlation function was studied as a function of the four-momentum difference of the kaon pairs, Q12=−(p1−p2)2, assuming a Gaussian shape for the particle source. The values of the radius of the production volume, r, and of the correlation strength, λ, were obtained for both neutral and charged kaons. The radii for charged and neutral kaons are similar and are consistent with those obtained at LEP.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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 photoproduction of
D
∗±
mesons has been measured with the ZEUS detector at HERA at three different
ep
centre-of-mass energies,
s
, of 318, 251 and 225 GeV. For each data set,
D
∗±
...mesons were required to have transverse momentum,
p
T
D
∗
, and pseudo-rapidity,
η
D
∗
, in the ranges 1
.
9
< p
T
D
∗
<
20 GeV and |
η
D
∗
|
<
1
.
6. The events were required to have a virtuality of the incoming photon,
Q
2
, of less than 1 GeV
2
. The dependence on
s
was studied by normalising to the high-statistics measurement at
s
=
318
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
s
dependence of the data well.
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.
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