8,807 research outputs found
Manifestation of the electric dipole moment in the decays of leptons produced in annihilation
\mbox{CP}-odd asymmetries in the processes , ,
, and are investigated with account for longitudinal
polarization of electrons (or positrons). These asymmetries is a manifestation
of electric dipole form factor in the
vertex. It is shown that to measure \mbox{Im}\,b, polarization is not needed,
and to measure \mbox{Re}\,b, the polarization is not necessary, but
simplifies the measurement of \mbox{Re}\,b.Comment: 12 pages, 1 figur
Quadrupole radiation and pair production in the collision of nonrelativistic nuclei
We analyze the one-photon mechanism of pair production in the
collision of nonrelativistic nuclei. The contribution of electric quadrupole
radiation of virtual photon to the corresponding cross section is found. The
effect of the finite nuclear size is considered in detail. A comparison is made
with the contribution of electric dipole radiation of virtual photon and with
the contribution of the two-photon pair production mechanism. It is shown that
the contribution of electric quadrupole radiation is dominant in a wide range
of relative velocities. The cross section for the production of pair
with the capture of an electron by one of the nuclei is also analyzed.Comment: 7 pages, 2 figue
An electromagnetic shashlik calorimeter with longitudinal segmentation
A novel technique for longitudinal segmentation of shashlik calorimeters has
been tested in the CERN West Area beam facility. A 25 tower very fine samplings
e.m. calorimeter has been built with vacuum photodiodes inserted in the first 8
radiation lengths to sample the initial development of the shower. Results
concerning energy resolution, impact point reconstruction and electron/pion
separation are reported.Comment: 13 pages, 12 figure
Quantum kinetic approach to the calculation of the Nernst effect
We show that the strong Nernst effect observed recently in amorphous
superconducting films far above the critical temperature is caused by the
fluctuations of the superconducting order parameter. We employ the quantum
kinetic approach for the derivation of the Nernst coefficient. We present here
the main steps of the calculation and discuss some subtle issues that we
encountered while calculating the Nernst coefficient. In particular, we
demonstrate that in the limit T=0 the contribution of the magnetization ensures
the vanishing of the Nernst signal in accordance with the third law of
thermodynamics. We obtained a striking agreement between our theoretical
calculations and the experimental data in a broad region of temperatures and
magnetic fields.Comment: 24 pages, 13 figure
Measurement of the decay form factors in the OKA experiment
A precise measurement of the vector and axial-vector form factors difference
in the decay is presented.
About 95K events of are selected in
the OKA experiment. The result is .
Both errors are smaller than in the previous measurements.Comment: 9 pages, 8 figure
Experimental study of direct photon emission in K- --> pi- pi0 gamma decay using ISTRA+ detector
The branching ratio in the charged-pion kinetic energy region of 55 to 90 MeV
for the direct photon emission in the K- --> pi- pi0 gamma decay has been
measured using in-flight decays detected with the ISTRA+ setup operating in the
25 GeV/c negative secondary beam of the U-70 PS. The value
Br(DE)=[0.37+-0.39(stat)+-0.10(syst)]*10^(-5) obtained from the analysis of 930
completely reconstructed events is consistent with the average value of two
stopped-kaon experiments, but it differs by 2.5 standard deviations from the
average value of three in-flight-kaon experiments. The result is also compared
with recent theoretical predictions.Comment: 13 pages, 8 figure
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