Charged particle production has been studied in neutral current deep inelastic
ep
scattering with the ZEUS detector at HERA using an integrated luminosity of 0.44 fb
−1
. Distributions of scaled ...momenta in the Breit frame are presented for particles in the current fragmentation region. The evolution of these spectra with the photon virtuality,
Q
2
, is described in the kinematic region 10 <
Q
2
< 41000Ge V
2
. Next-to-leading-order and modified leading-log-approximation QCD calculations as well as predictions from Monte Carlo models are compared to the data. The results are also compared to
e
+
e
−
annihilation data. The dependences of the pseudorapidity distribution of the particles on
Q
2
and on the energy in the γ
p
system,
W
, are presented and interpreted in the context of the hypothesis of limiting fragmentation.
A particle detector made of semi-insulating GaAs is used for preliminary study of X-ray imaging. A standard technology developed in our laboratory is applied to prepare this detector. The detector ...works at room temperature in the photon counting mode. Results show that the quality of images taken at chosen exposure range is limited only by the photonic noise from used X-ray source
241Am.
Subjet distributions were measured in neutral current deep inelastic
ep
scattering with the ZEUS detector at HERA using an integrated luminosity of 81.7 pb
−1
. Jets were identified using the
k
T
...cluster algorithm in the laboratory frame. Subjets were defined as jet-like substructures identified by a reapplication of the cluster algorithm at a smaller value of the resolution parameter
. Measurements of subjet distributions for jets with exactly two subjets for
are presented as functions of observables sensitive to the pattern of parton radiation and to the colour coherence between the initial and final states. Perturbative QCD predictions give an adequate description of the data.
Electrical characteristics and detection performance of recently developed and fabricated 32-pixel line array chip for detection of X- and γ-rays named “SAMO” based on semi-insulating GaAs and InP ...are reported. The chip with dimensions of 7×2.4×(0.2–0.3) mm
3 is mounted on a ceramic holder. Single pixel has an active area of 2000×(120–180) μm
2 with pitch of 220
μm. Current density of GaAs-based single pixel at a bias voltage of 120
V ranges between 15 and 60
nA/mm
2. The threshold voltage ranges between 150 and 500
V. Pulse-height spectra in both,
side as well as
top irradiation modes measured using 59.5
V and 122
keV γ-sources are demonstrated. The best detection performance observed with GaAs-based SAMO line detector reached charge collection efficiency of 85%, relative energy resolution in HWHM 4%, and detection efficiency in the photopeak 52% (122
keV, 300
K, the
side irradiation). Preliminary results obtained with InP-based SAMO line detector are discussed.
Study of taupair production at HERA Aggarwal, R.; Antonelli, S.; Antonov, A. ...
The journal of high energy physics,
02/2011, Letnik:
2011, Številka:
2
Journal Article
Recenzirano
Odprti dostop
A study of events containing two tau leptons with high transverse momentum has been performed with the ZEUS detector at HERA, using a data sample corresponding to an integrated luminosity of 0.33 fb
...−1
. The tau candidates were identified from their decays into electrons, muons or hadronic jets. The number of tau-pair candidates has been compared with the prediction from the Standard Model, where the largest contribution is expected from Bethe-Heitler processes. The total visible cross section was extracted. Standard Model expectations agree well with the measured distributions, also at high invariant mass of the tau pair.
The distribution of the azimuthal angle of charged and neutral hadrons relative to the lepton plane has been studied for neutral current deep inelastic ep scattering using an integrated luminosity of ...45 pb-1 taken with the ZEUS detector. The kinematic range is 100<Q2<8000 GeV2, 0.2<y<0.8 and 0.01<x<0.1 where Q2 is the virtuality of the exchanged boson, y is the inelasticity and x is the Bjorken variable. The measurements were made in the hadronic centre-of-mass system. The analysis exploits the energy-flow method, which allows the measurement to be made over a larger range of pseudorapidity compared to previous results. The dependence of the moments of the azimuthal distributions on the pseudorapidity and minimum transverse energy of the final-state hadrons are presented. Although the predictions from next-to-leading-order QCD describe the data better than do the Monte Carlo models incorporating leading-logarithm parton showers, they still fail to describe the magnitude of the asymmetries. This suggests that higher-order calculations may be necessary to describe these data.
The production of beauty quarks with a \(D^{\ast\pm}\) and a muon in the final state has been measured with the ZEUS detector at HERA using an integrated luminosity of 114 pb-1. Low ...transverse-momentum thresholds for the muon and D* meson allow for a measurement of beauty production closer to the production threshold than previous measurements. The beauty signal was extracted using the charge correlations and angular distributions of the muon with respect to the D* meson. Cross sections for photoproduction and deep inelastic scattering are somewhat higher than, but compatible with, next-to-leading-order QCD predictions, and compatible with other measurements.
ArchaeoGRID, a GRID for archaeology Pelfer, P.G.; Barcelo, J.A.; McDonaill, C. ...
IEEE Symposium Conference Record Nuclear Science 2004,
2004, Letnik:
4
Conference Proceeding
The approach of modern archaeology to the study of the evolution of ancient human societies is based on the acquisition and analysis of many types of data. It is well known that in archaeology large ...use is done of digital technologies and computer applications for data acquisition, storage, analysis and visualization. The amount of information coming from remote sensing, from acquisition of 3D artifacts images by scanners laser, from GPS precise reference of geographical points and from other sciences are increasing at a large extent the amount of data that it need to be stored and made available for analysis. Such data must, however, be analyzed if they are to become valuable information and knowledge. The data analysis use advanced methods developed in mathematics, informatics, and physics and in other natural and human sciences. Moreover the use of virtual archaeology as a new approach to the narration and visualization in archaeology, is expanding rapidly, not only in the museum and archaeology professions, but also in the broadcast media, tourism and heritage industries. The inevitable result of this is an exponential increase of the amount and complexity of information that must be acquired, transferred, stored, processed and analyzed. From another side natural disasters, wars and terrorism created enormous damages to the archaeological heritage and in many case destroyed definitively all information about ancient civilizations. It is urgent a long term project for acquiring at least the archaeological information.
Measurements of the cross sections for charged current deep inelastic scattering in e+p collisions with a longitudinally polarised positron beam are presented. The measurements are based on a data ...sample with an integrated luminosity of 132 pb−1 collected with the ZEUS detector at HERA at a centre-of-mass energy of 318 GeV. The total cross section is presented at positive and negative values of the longitudinal polarisation of the positron beams. The single-differential cross-sections dσ/dQ2, dσ/dx and dσ/dy are presented for Q2>200 GeV2. The reduced cross-section \(\tilde{\sigma}\) is presented in the kinematic range 200<Q2<60 000 GeV2 and 0.006<x<0.562. The measurements agree well with the predictions of the Standard Model. The results are used to determine a lower limit on the mass of a hypothetical right-handed W boson.
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