The production of D±- and D0-mesons has been measured with the ZEUS detector at HERA using an integrated luminosity of 133.6 pb−1. The measurements cover the kinematic range 5<Q2<1000 GeV2, ...0.02<y<0.7, 1.5<pTD<15 GeV and |ηD|<1.6. Combinatorial background to the D-meson signals is reduced by using the ZEUS microvertex detector to reconstruct displaced secondary vertices. Production cross sections are compared with the predictions of next-to-leading-order QCD, which is found to describe the data well. Measurements are extrapolated to the full kinematic phase space in order to obtain the open-charm contribution, \(F_{2}^{c\bar{c}}\), to the proton structure function, F2.
The proton-dissociative diffractive photoproduction of
J
/
ψ
mesons has been studied in ep collisions with the ZEUS detector at HERA using an integrated luminosity of 112 pb
−1
. The cross section is ...presented as a function of the photon-proton centre-of-mass energy and of the squared four-momentum transfer at the proton vertex. The results are compared to perturbative QCD calculations.
Photoproduction of beauty and charm quarks in events with at least two jets has been measured with the ZEUS detector at HERA using an integrated luminosity of 133 pb
−1
. The fractions of jets ...containing
b
and
c
quarks were 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 jet transverse momentum,
, and pseudorapidity,
η
jet
, were measured. The data are compared with previous measurements and are well described by next-to-leading-order QCD predictions.
Recent results on the electrical properties and detection performances of the semi-insulating InP-based detectors and future programmes are presented. Schottky barrier detectors with a nitride ...barrier-enhanced interfacial layer and the Schottky back contacts, using material from MASPEC, exhibited a charge collection efficiency (CCE) over 75% and an energy resolution of 4.5% full-width at half-maximum (FWHM) for 5.48
MeV
α-particles at RT, CCE over 90% and FWHM less than 3% at 230
K. Furthermore, they are able to detect
γ-rays (122 and 60
keV photons) when cooled down to 240
K. New detectors, fabricated with liquid-encapsulated Czochralski material (LEC), produced with a special high-temperature annealing treatment from Japan Energy, coated with an original patented buffer layer and with a symmetrical circular contact configuration using both-sided photolithography and a final electrode metallisation Ti/Pt/Au for both sides, give the best results with a CCE over 88% and a FWHM less than 9% for detection of 122
keV
γ-rays.
In this work, bulk semi-insulating (SI) InP wafers of four various producers have been used for the fabrication of radiation detectors. The tested detectors were prepared starting from the different ...materials in just one run in order to be sure that their performances were not influenced by technological processes. On one type of material various electrode technologies were used with the aim to analyze their role on the detector performances. The fabricated detectors were tested for detection performance by the
241Am and
57Co gamma-ray sources at below room temperature. The best detector was calibrated and tested also using
133Ba and
137Cs gamma sources. The best detector gives an energy resolution of 7
keV FWHM and a charge collection efficiency (CCE) of 82% (59.5
keV photopeak) at a temperature of 216
K. According to our knowledge, these results are the best which have been obtained with InP radiation detectors till now. The operation of SI InP detector at room temperature is demonstrated and discussed.
In general, the CCE and the energy resolution of radiation detectors fabricated on bulk SI InP materials showed a strong dependence on the electrode technology as well as the base substrate quality.
The photoproduction of prompt photons, together with an accompanying jet, has been studied in ep collisions at a centre-of-mass energy of 318 GeV with the ZEUS detector at HERA using an integrated ...luminosity of 77 pb-1. Cross sections were measured for the transverse energy of the photon and the jet larger than 5 and 6 GeV, respectively. The differential γ+jet cross sections were reconstructed as functions of the transverse energy, pseudorapidity and xγobs, the fraction of the incoming photon momentum taken by the photon-jet system. Predictions based on leading-logarithm parton-shower Monte Carlo models and next-to-leading-order (NLO) QCD generally underestimate the cross sections for the transverse energies of prompt photons below 7 GeV, while the kT-factorisation QCD calculation agrees with the data better. When the minimum transverse energy of prompt photons is increased to 7 GeV, both NLO QCD and the kT-factorisation calculations are in good agreement with the data.
The exclusive photoproduction reaction gamma p arrow right Upsilon ( 1 S ) p has been studied with the ZEUS detector in ep collisions at HERA using an integrated luminosity of 468 pb - 1 . The ...measurement covers the kinematic range 60 < W < 220 GeV and Q 2 < 1 GeV 2 , where W is the photon-proton centre-of-mass energy and Q 2 is the photon virtuality. The exponential slope, b, of the t dependence of the cross section, where t is the squared four-momentum transfer at the proton vertex, has been measured, yielding b = 4.3 - 1.3 + 2.0 ( stat . ) - 0.6 + 0.5 ( syst . ) GeV - 2 . This constitutes the first measurement of the t dependence of the gamma p arrow right Upsilon ( 1 S ) p cross section.
Diffractive photoproduction of D±(2010) at HERA Derrick, M.; Nicholass, D.; Yoshida, R. ...
European physical journal. C, Particles and fields,
7/2007, Letnik:
51, Številka:
2
Journal Article
Recenzirano
Odprti dostop
Diffractive photoproduction of D*±(2010) mesons was measured with the ZEUS detector at the ep collider HERA, using an integrated luminosity of 78.6 pb-1. The D* mesons were reconstructed in the ...kinematic range: transverse momentum pT(D*) > 1.9 GeV and pseudorapidity |η(D*)|<1.6, using the decay D*+→D0π+s followed by D0→K-π+(+c.c.). Diffractive events were identified by a large gap in pseudorapidity between the produced hadronic state and the outgoing proton. Cross sections are reported for photon–proton centre-of-mass energies in the range 130 < W < 300 GeV and for photon virtualities Q2 < 1 GeV2, in two ranges of the Pomeron fractional momentum xIP<0.035 and xIP<0.01. The relative contribution of diffractive events to the inclusive D*±(2010) photoproduction cross section is about 6%. The data are in agreement with perturbative QCD calculations based on various parameterisations of diffractive parton distribution functions. The results are consistent with diffractive QCD factorisation.
Production of
D
∗±(2010)
mesons in diffractive deep inelastic scattering has been measured with the ZEUS detector at HERA using an integrated luminosity of 82 pb
−1. Diffractive events were ...identified by the presence of a large rapidity gap in the final state. Differential cross sections have been measured in the kinematic region 1.5<
Q
2<200 GeV
2, 0.02<
y<0.7,
x
P
<0.035
,
β<0.8,
p
T(D
∗±)>1.5
GeV and
|η(D
∗±)|<1.5
. The measured cross sections are compared to theoretical predictions. The results are presented in terms of the open-charm contribution to the diffractive proton structure function. The data demonstrate a strong sensitivity to the diffractive parton densities.
Forward jet cross sections have been measured in neutral current deep inelastic scattering at low Bjorken-x with the ZEUS detector at HERA using an integrated luminosity of 81.8 pb-1. Measurements ...are presented for inclusive forward jets as well as for forward jets accompanied by a dijet system. The explored phase space, with jet pseudorapidity up to 4.3 is expected to be particularly sensitive to the dynamics of QCD parton evolution at low x. The measurements are compared to fixed-order QCD calculations and to leading-order parton-shower Monte Carlo models.
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