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.
Diffractive photoproduction of dijets was measured with the ZEUS detector at the ep collider HERA using an integrated luminosity of 77.2 pb
-1
. The measurements were made in the kinematic range Q
2
...< 1 GeV
2
, 0.20<y<0.85 and x
IP
<0.025, where Q
2
is the photon virtuality, y is the inelasticity and x
IP
is the fraction of the proton momentum taken by the diffractive exchange. The two jets with the highest transverse energy, E
T
jet
, were required to satisfy E
T
jet
>7.5 and 6.5 GeV, respectively, and to lie in the pseudorapidity range -1.5<η
jet
<1.5. Differential cross sections were compared to perturbative QCD calculations using available parameterisations of diffractive parton distributions of the proton.
The production of charm and beauty quarks in
ep
interactions has been measured with the ZEUS detector at HERA for squared four-momentum exchange
Q
2
>20 GeV
2
, using an integrated luminosity of ...126 pb
−1
. Charm and beauty quarks were identified through their decays into muons. Differential cross sections were measured for muon transverse momenta
and pseudorapidities −1.6<
η
μ
<2.3, as a function of
,
η
μ
,
Q
2
and Bjorken
x
. The charm and beauty contributions to the proton structure function
F
2
were also extracted. The results agree with previous measurements based on independent techniques and are well described by QCD predictions.
The production of dijets in diffractive deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 61 pb-1. The dijet cross section has been measured ...for virtualities of the exchanged virtual photon, 5 < Q2 < 100 GeV2, and γ*p centre-of-mass energies, 100 < W < 250 GeV. The jets, identified using the inclusive kT algorithm in the γ*p frame, were required to have a transverse energy E*T,jet > 4 GeV and the jet with the highest transverse energy was required to have E*T,jet > 5 GeV. All jets were required to be in the pseudorapidity range -3.5<η*jet<0. The differential cross sections are compared to leading-order predictions and next-to-leading-order QCD calculations based on recent diffractive parton densities extracted from inclusive diffractive deep inelastic scattering data.
Measurements of the cross sections for charged current deep inelastic scattering in
e
−
p
collisions with longitudinally polarised electron beams are presented. The measurements are based on a data ...sample with an integrated luminosity of 175 pb
−1
collected with the ZEUS detector at HERA at a centre-of-mass energy of 318 GeV. The total cross section is given for positively and negatively polarised electron beams. The differential cross-sections
d
σ
/
dQ
2
,
d
σ
/
dx
and
d
σ
/
dy
are presented for
Q
2
>200 GeV
2
. The double-differential cross-section
d
2
σ
/
dxdQ
2
is presented in the kinematic range 280<
Q
2
<30 000 GeV
2
and 0.015<
x
<0.65. The measured cross sections are compared with the predictions of the Standard Model.
Exclusive electroproduction of two pions at HERA Abramowicz, H.; Aggarwal, R.; Antonov, A. ...
The European physical journal. C, Particles and fields,
01/2012, Letnik:
72, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The exclusive electroproduction of two pions in the mass range 0.4<
M
ππ
<2.5 GeV has been studied with the ZEUS detector at HERA using an integrated luminosity of 82 pb
−1
. The analysis was carried ...out in the kinematic range of 2<
Q
2
<80 GeV
2
, 32<
W
<180 GeV and |
t
|<0.6 GeV
2
, where
Q
2
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 two-pion invariant-mass distribution is interpreted in terms of the pion electromagnetic form factor, |
F
(
M
ππ
)|, assuming that the studied mass range includes the contributions of the
ρ
,
ρ
′ and
ρ
′′ vector-meson states. The masses and widths of the resonances were obtained and the
Q
2
dependence of the cross-section ratios
σ
(
ρ
′→
ππ
)/
σ
(
ρ
) and
σ
(
ρ
′′→
ππ
)/
σ
(
ρ
) was extracted. The pion form factor obtained in the present analysis is compared to that obtained in
e
+
e
−
→
π
+
π
−
.
The production of beauty quarks in
ep
interactions has been studied with the ZEUS detector at HERA for exchanged four-momentum squared
Q
2
>10 GeV
2
, using an integrated luminosity of 363 pb
−1
. ...The beauty events were identified using electrons from semileptonic
b
decays with a transverse momentum
GeV and pseudorapidity |
η
e
|<1.5. Cross sections for beauty production were measured and compared with next-to-leading-order QCD calculations. The beauty contribution to the proton structure function
F
2
was extracted from the double-differential cross section as a function of Bjorken-
x
and
Q
2
.
Charm production in deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 120 pb
−1
. The hadronic decay channels
D
+
→
K
S
0
π
+
, Λ
c
+
→
pK
S
...0
and Λ
c
+
→ Λ
π
+
, and their charge conjugates, were reconstructed. The presence of a neutral strange hadron in the final state reduces the combinatorial background and extends the measured sensitivity into the low transverse momentum region. The kinematic range is 0
< p
T
(
D
+
, Λ
c
+
) < 10 GeV, |
η
(
D
+
, Λ
c
+
)| < 1
.
6, 1.5 <
Q
2
< 1000 GeV
2
and 0
.
02 <
y
< 0.7. Inclusive and differential cross sections for the production of
D
+
mesons are compared to next-to-leading-order QCD predictions. The fraction of
c
quarks hadronising into Λ
c
+
baryons is extracted.
The production of excited charm,
D
1
(2420)
0
and
D
2
*
(2460)
0
, and charm-strange,
D
s
1
(2536)
±
, mesons in
ep
collisions was measured with the ZEUS detector at HERA using an integrated ...luminosity of 126 pb
−1
. Masses, widths and helicity parameters were determined. The measured yields were converted to the rates of
c
quarks hadronising as a given excited charm meson and to the ratios of the dominant
D
2
*
(2460)
0
and
D
s
1
(2536)
±
branching fractions. A search for the radially excited charm meson,
D
*′
(2640)
±
, was also performed. The results are compared with those measured previously and with theoretical expectations.
In this work the role of electrode technology of a radiation detector based on Liquid Encapsulated Czochralski semi-insulating (SI) InP is investigated with emphasis on the development of a ...monolithic array of pixel detectors. Two different electrode technologies are applied: (i) Au evaporation to form a metal–semiconductor–metal structure with a quasi-Schottky barrier, and (ii) MOCVD of a p+ layer for the creation of a pin structure using the same SI InP base. The I–V characteristics and pulse height spectra of 241Am and 57Co are measured at room and lower temperatures and evaluated. The observed results show different electrical as well as detection performance of fabricated structures. Mechanical sawing and wet etched trench methods are applied with the aim of reducing electrical charge inter-diffusion between neighbouring strip detectors as a preliminary study to the fabrication of a segmented, monolithic detector array based on SI InP. SM and I–V methods are used for the evaluation of the wet chemical process used. The observed results and future works are discussed in view of results obtained within the study.
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