3,431 research outputs found
Recent Results on Particle Production from OPAL
Three recent OPAL studies are presented in which the fragmentation process in
quark and gluon jets and in identified up, down and strange flavour jets is
studied. The first is a measurement of charged particle, pi0, eta and K0
multiplicities in quark and gluon jets. No evidence is found for a
particle-species dependent multiplicity enhancement in gluon jets. In another
study leading pion, kaon, K0, proton and lambda rates have been measured in up,
down and strange flavour jets. The results confirm the leading particle effect
in the fragmentation of light flavour jets. In addition, a direct determination
of the strangeness suppression factor has been performed, yielding
gamma_s=0.422 +/- 0.049(stat.) +/- 0.059(syst.). In a third study, mean charged
particle multiplicities were measured for up, down and strange flavoured Z0
decays and found to be identical within the uncertainties of the measurement,
as expected from the flavour independence of the strong interaction.Comment: 6 pages, LaTeX, to appear in the proceedings of the 30th
International Symposium on Multiparticle Dynamics, October 9 - 15, 2000,
Tihany, Hungar
Jets and multiplicities in e+e-
Recent results on jet and inclusive charged particle production in hadronic
e+e- interactions are reviewed.Comment: 5 pages, to appear in the proceedings of the EPS/HEP-2001 conference,
Budapest, Hungar
Tyrosine phosphorylation-dependent activation of phosphatidylinositide 3-kinase occurs upstream of Ca^(2+)-signalling induced by Fcy receptor cross-linking in human neutrophils
The effect of wortmannin on IgG-receptor (FcyR)-mediated
stimulation of human neutrophils was investigated. The Ca^(2+)
influx induced by clustering of both Fcy receptors was inhibited
by wortmannin, as was the release of Ca^(2+) from intracellular
stores. Wortmannin also inhibited, with the same efficacy, the
accumulation of Ins(1,4,5)P3 observed after FcyR stimulation,
but did not affect the increase in Ins(1,4,5)P3 induced by the
chemotactic peptide, formyl-methionine-leucine-phenylalanine.
Because wortmannin is, in the concentrations used here, an
inhibitor of PtdIns 3-kinase, these results suggested a role for
PtdIns 3-kinase upstream of Ca^(2+) signalling, induced by FcyR
cross-linking. Support for this notion was obtained by investigating
the effect of another inhibitor of PtdIns 3-kinase, LY
294002, and by studying the kinetics of PtdIns 3-kinase activation.
We found translocation of PtdIns 3-kinase to the plasma
membrane and increased PtdIns 3-kinase activity in the membrane
as soon as 5 s after FccR cross-linking, even before the
onset of the Ca^(2+) response. Moreover, the translocation of
PtdIns 3-kinase to the plasma membrane was inhibited by cocross-
linking of either FcyRIIa and FcyRIIIb with the tyrosine
phosphatase, CD45, indicating a requirement for protein tyrosine
phosphorylation in the recruitment of PtdIns 3-kinase to the
plasma membrane. Taken together, our results suggest a role for
PtdIns 3-kinase in early signal transduction events after FcyR
cross-linking in human neutrophils
The Presampler for the Forward and Rear Calorimeter in the ZEUS Detector
The ZEUS detector at HERA has been supplemented with a presampler detector in
front of the forward and rear calorimeters. It consists of a segmented
scintillator array read out with wavelength-shifting fibers. We discuss its
desi gn, construction and performance. Test beam data obtained with a prototype
presampler and the ZEUS prototype calorimeter demonstrate the main function of
this detector, i.e. the correction for the energy lost by an electron
interacting in inactive material in front of the calorimeter.Comment: 20 pages including 16 figure
POREZ NA DOHODAK U REPUBLICI HRVATSKOJ
Ovaj Älanak obraÄuje porez na dohodak kao neposredni (izravni) porez
u poreznom sustavu Republike Hrvatske kojim su obuhvaÄeni fiziÄke osobe, obveznici
poreza na dohodak. Definiranje i pojaĆĄnjenje vrste dohodaka s obzirom na izvor dohotka
i to: dohodak od nesamostalnog rada, dohodak od samostalne djelatnosti, dohodak od
imovine i imovinskih prava, dohodak od kapitala, dohodak od osiguranja, drugi dohodak,
te metodologija utvrÄivanja porezne obveze i poreznih stopa i utvrÄivanje poreznog
razdoblja.
Navedeni su primici koji se ne smatraju dohotkom, ĆĄto je to porezni gubitak te osobni
odbitak kao neoporezivi dio dohotka
Measurement of inclusive D*+- and associated dijet cross sections in photoproduction at HERA
Inclusive photoproduction of D*+- mesons has been measured for photon-proton
centre-of-mass energies in the range 130 < W < 280 GeV and a photon virtuality
Q^2 < 1 GeV^2. The data sample used corresponds to an integrated luminosity of
37 pb^-1. Total and differential cross sections as functions of the D*
transverse momentum and pseudorapidity are presented in restricted kinematical
regions and the data are compared with next-to-leading order (NLO) perturbative
QCD calculations using the "massive charm" and "massless charm" schemes. The
measured cross sections are generally above the NLO calculations, in particular
in the forward (proton) direction. The large data sample also allows the study
of dijet production associated with charm. A significant resolved as well as a
direct photon component contribute to the cross section. Leading order QCD
Monte Carlo calculations indicate that the resolved contribution arises from a
significant charm component in the photon. A massive charm NLO parton level
calculation yields lower cross sections compared to the measured results in a
kinematic region where the resolved photon contribution is significant.Comment: 32 pages including 6 figure
Testbeam results of irradiated ams H18 HV-CMOS pixel sensor prototypes
HV-CMOS pixel sensors are a promising option for the tracker upgrade of the ATLAS experiment at the LHC, as well as for other future tracking applications in which large areas are to be instrumented with radiation-tolerant silicon pixel sensors. We present results of testbeam characterisations of the 4th generation of Capacitively Coupled Pixel Detectors (CCPDv4) produced with the ams H18 HV-CMOS process that have been irradiated with different particles (reactor neutrons and 18 MeV protons) to fluences between 1Ă 1014 and 5Ă 1015 1âMeVâ neq. The sensors were glued to ATLAS FE-I4 pixel readout chips and measured at the CERN SPS H8 beamline using the FE-I4 beam telescope. Results for all fluences are very encouraging with all hit efficiencies being better than 97% for bias voltages of 85 V. The sample irradiated to a fluence of 1Ă 1015 neqâa relevant value for a large volume of the upgraded trackerâexhibited 99.7% average hit efficiency. The results give strong evidence for the radiation tolerance of HV-CMOS sensors and their suitability as sensors for the experimental HL-LHC upgrades and future large-area silicon-based tracking detectors in high-radiation environments
Determination of alpha_s using Jet Rates at LEP with the OPAL detector
Hadronic events produced in e+e- collisions by the LEP collider and recorded
by the OPAL detector were used to form distributions based on the number of
reconstructed jets. The data were collected between 1995 and 2000 and
correspond to energies of 91 GeV, 130-136 GeV and 161-209 GeV. The jet rates
were determined using four different jet-finding algorithms (Cone, JADE, Durham
and Cambridge). The differential two-jet rate and the average jet rate with the
Durham and Cambridge algorithms were used to measure alpha(s) in the LEP energy
range by fitting an expression in which order alpah_2s calculations were
matched to a NLLA prediction and fitted to the data. Combining the measurements
at different centre-of-mass energies, the value of alpha_s (Mz) was determined
to be
alpha(s)(Mz)=0.1177+-0.0006(stat.)+-0.0012$(expt.)+-0.0010(had.)+-0.0032(theo.)
\.Comment: 40 pages, 17 figures, Submitted to Euro. Phys. J.
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