GaAs detectors for hard X-ray astronomy Dubecký, F.; Krempaský, M.; Pelfer, P.G. ...
Nuclear physics. Section B, Proceedings supplement,
03/1997, Letnik:
54, Številka:
3
Journal Article
Recenzirano
Particle detectors fabricated from bulk semi-insulating (SI) GaAs of 4 different suppliers are investigated. I-V, C-V characteristics, material transport parameters as well as inhomogeneities are ...studied and correlated with detector performances. It was observed that the charge collection efficiency and the energy resolution of detectors tested by 5.48 MeV α-particles and 122 keV X-rays is strongly affected by physical properties of the base material. It is concluded that detectors fabricated from the graded bulk SI GaAs material are suitable for application in hard X-ray astronomy.
The photoproduction of dijet events, where the two jets with the highest transverse energy are separated by a large gap in pseudorapidity, have been studied with the ZEUS detector using an integrated ...luminosity of 39 pb-1. Rapidity-gap events are defined in terms of the energy flow between the jets, such that the total summed transverse energy in this region is less than some value ETCUT. The data show a clear excess over the predictions of standard photoproduction models. This is interpreted as evidence for a strongly interacting exchange of a color-singlet object. Monte Carlo models which include such a color-singlet exchange are able to describe the data.
I–V characteristics and detection properties (CCE, FWHM) of the semi-insulating GaAs detectors (base length 200 μm) with the Au-Au and W-W Schottky barriers and N
+-N
+ ohmic contacts, measured at ...room temperature, are presented for
α,
β and heavier particles (up to
Z ⋍ 10). The best results (average values of CCE and FWHM were 87% and 5%, respectively, for 5.48 MeV
α particles from
241Am) give detectors with the Au-Au contact configuration. Detectors with the N
+ contacts have worse parameters, about 30% for both, the CCE and FWHM, respectively. Nevertheless, such detectors operate at a low bias voltage, under 20 V.
The photoproduction of prompt photons, together with an accompanying jet, has been measured with the ZEUS detector at HERA using an integrated luminosity of 38.6 pb
−1. A study of the effective ...transverse momentum, 〈
k
T
〉, of partons in the proton, as modelled within the framework of the PYTHIA Monte Carlo, gives a value of 〈
k
T
〉=1.69±0.18
+0.18
−0.20 GeV for the
γp centre-of-mass energy range 134<
W<251 GeV. This result is in agreement with the previously observed trend in hadron–hadron scattering for 〈
k
T
〉 to rise with interaction energy.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) The production of D ^sup *±^ mesons in deep inelastic ep scattering has been measured for exchanged photon virtualities 5<Q ...^sup 2^<1000 GeV^sup 2^, using an integrated luminosity of 363 pb^sup -1^ with the ZEUS detector at HERA. Differential cross sections have been measured and compared to next-to-leading-order QCD calculations. The cross-sections are used to extract the charm contribution to the proton structure functions, expressed in terms of the reduced charm cross section, ... Theoretical calculations based on fits to inclusive HERA data are compared to the results.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) Charm production in deep inelastic ep scattering was measured with the ZEUS detector using an integrated luminosity of 354 ...pb^sup -1^. Charm quarks were identified by reconstructing D ^sup ±^ mesons in the D ^sup ±^ arrow right K ^sup ^pi^sup ±^pi^sup ±^ decay channel. Lifetime information was used to reduce combinatorial background substantially. Differential cross sections were measured in the kinematic region 5 < Q ^sup 2^ < 1000 GeV^sup 2^, 0.02 < y < 0.7, 1.5 < p ^sub T^ (D ^sup ±^) < 15 GeV and |eta(D ^sup ±^)| < 1.6, where Q ^sup 2^ is the photon virtuality, y is the inelasticity, and p ^sub T^ (D ^sup ±^) and eta(D ^sup ±^) are the transverse momentum and the pseudorapidity of the D ^sup ±^ meson, respectively. Next-to-leading-order QCD predictions are compared to the data. The charm contribution, ..., to the proton structure-function F ^sub 2^ was extracted.
Measurement of K0 S, Λ and Λ̄ production at HERA Derrick, M.; Nicholass, D.; Yagües Molina, A.G. ...
European physical journal. C, Particles and fields,
6/2007, Letnik:
51, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The production of the neutral strange hadrons K0S, Λ and Λ̄ has been measured in ep collisions at HERA using the ZEUS detector. Cross sections, baryon-to-meson ratios, relative yields of strange and ...charged light hadrons, Λ (Λ̄) asymmetry and polarization have been measured in three kinematic regions: Q2 > 25 GeV2; 5 < Q2 < 25 GeV2; and in photoproduction (Q2≃0). In photoproduction the presence of two hadronic jets, each with at least 5 GeV transverse energy, was required. The measurements agree in general with Monte Carlo models and are consistent with measurements made at e+e- colliders, except for an enhancement of baryon relative to meson production in photoproduction.
The cross sections for inelastic photoproduction of J/psi and psi' mesons have been measured in ep collisions with the ZEUS detector at HERA, using an integrated luminosity of 468 pb^sup -1^ ...collected in the period 1996-2007. The psi' to J/psi 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 ^sub 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 ^sub T^ is the transverse momentum of the meson with respect to the beam axis. The J/psi cross sections were measured for 0.1<z<0.9, 60<W<240 GeV and p ^sub 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 ^sub T^-factorisation approach.
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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