2,039 research outputs found
Elastic scattering of solar neutrinos with electromagnetic moments
We consider the azimuthal asymmetry of the recoil electrons in elastic scattering of solar neutrinos, which can arise if neutrinos have
electromagnetic moments and there is a large solar magnetic field. We show that
using this effect it is not possible to distinguish between magnetic and
electric dipole moment in the 1-Dirac and 2-Majorana neutrino cases and that
averaging over neutrino energy is important and suppresses the azimuthal
asymmetry in the 2-Majorana case.Comment: 4 pages, Talk given by T. Schwetz at EuroConference on Frontiers in
Particle Astrophysics and Cosmology, San Feliu de Guixols, Spain, 30 Sept.-5
Oct. 200
Hyperfine splittings in the system
Recent measurements of the , the ground state of the
system, show the splitting between it and the \Up(1S) to be 69.53.2 MeV,
considerably larger than lattice QCD and potential model predictions, including
recent calculations published by us. The models are unable to incorporate such
a large hyperfine splitting within the context of a consistent description of
the energy spectrum and decays. We demonstrate that in our model, which
incorporates a relativistic kinetic energy term, a linear confining term
including its scalar-exchange relativistic corrections, and the complete
one-loop QCD short distance potential, such a consistent description, including
the measured hyperfine splitting, can be obtained by not softening the delta
function terms in the hyperfine potential. We calculate the hyperfine splitting
to be 67.5 MeV.Comment: 5 pages, 3 tables, text revision
Low-noise monolithic bipolar front-end for silicon drift detectors
Abstract A very low noise, 32-channel preamplifier/shaper chip has been designed for the analogue readout of silicon detectors. The circuit has been optimized in view of the operation of silicon drift detectors, which have very low capacitance and produce gaussian signals of Ï of few tens of ns. The chip (OLA) has been designed and manufactured using the SHPi full-custom bipolar process by Tektronix. Each channel is composed by a preamplifier, a shaper and a symmetrical line driver, which allows to drive either a positive and a negative single ended output separately on 50 Ω impedance or a differential twisted pair. The intrinsic peaking time of the circuit is âŒ60 ns , and the noise is below 250 electrons at zero input load capacitance. The power consumption is 2 mW/channel, mostly due to the output driver
High Resolution Hybrid Pixel Sensors for the e+e- TESLA Linear Collider Vertex Tracker
In order to fully exploit the physics potential of a future high energy e+e-
linear collider, a Vertex Tracker, providing high resolution track
reconstruction, is required. Hybrid Silicon pixel sensors are an attractive
option, for the sensor technology, due to their read-out speed and radiation
hardness, favoured in the high rate environment of the TESLA e+e- linear
collider design but have been so far limited by the achievable single point
space resolution. In this paper, a conceptual design of the TESLA Vertex
Tracker, based on a novel layout of hybrid pixel sensors with interleaved cells
to improve their spatial resolution, is presented.Comment: 12 pages, 5 figures, to appear in the Proceedings of the Vertex99
Workshop, Texel (The Netherlands), June 199
Optimized Variables of the Study of Polarization
The value of the -baryon polarization can be extracted from inclusive data
at LEP with better than 10\% precision based on current statistics. We present
a new variable by which to measure the polarization, which is the ratio of the
average electron energy to the average neutrino energy. This variable is both
sensitive to polarization and insensitive to fragmentation uncertainties.Comment: 10 pages (LaTeX), 2 figures, MIT-CTP-2270, CERN-PPE/94-0
Vertex functions for d-wave mesons in the light-front approach
While the light-front quark model (LFQM) is employed to calculate hadronic
transition matrix elements, the vertex functions must be pre-determined. In
this work we derive the vertex functions for all d-wave states in this model.
Especially, since both of and are mesons, the Lorentz
structures of their vertex functions are the same. Thus when one needs to study
the processes where is involved, all the corresponding formulas for
states can be directly applied, only the coefficient of the vertex
function should be replaced by that for . The results would be useful
for studying the newly observed resonances which are supposed to be d-wave
mesons and furthermore the possible 2S-1D mixing in with the LFQM.Comment: 12 pages, 2 figures, some typos corrected and more discussions added.
Accepted by EPJ
Weak magnetic dipole moments in two-Higgs-doublet models
We investigate the effects of the new scalars in a two-Higgs-doublet model on
the weak magnetic dipole moments of the fermions at the peak.
Proportionality of the Yukawa couplings to the fermion masses, and to
, makes such effects more important for the third family, and
potentially relevant. For the lepton, the new diagrams are suppressed by
, or by powers of , but may still
be comparable to the SM electroweak contributions. In contrast, we find that
the new contributions for the bottom quark may be much larger than the SM
electroweak contributions. These new effects may even compete with the gluonic
contribution, if the extra scalars are light and is large. We also
comment on the problem of the gauge dependence of the vertex, arising when the
is off mass shell. We compute the contributions from the new scalars to the
magnetic dipole moments for top-quark production at the NLC, and for bottom and
production at LEP2. In the case of the top, we find that the SM
electroweak and gluonic contributions to the vertex are
comparable. The new contributions may be of the same order of magnitude as the
standard-model ones, but not much larger.Comment: 17 pages, LaTex, 8 figures available upon reques
The Cosmic-Ray Proton and Helium Spectra measured with the CAPRICE98 balloon experiment
A new measurement of the primary cosmic-ray proton and helium fluxes from 3
to 350 GeV was carried out by the balloon-borne CAPRICE experiment in 1998.
This experimental setup combines different detector techniques and has
excellent particle discrimination capabilities allowing clear particle
identification. Our experiment has the capability to determine accurately
detector selection efficiencies and systematic errors associated with them.
Furthermore, it can check for the first time the energy determined by the
magnet spectrometer by using the Cherenkov angle measured by the RICH detector
well above 20 GeV/n. The analysis of the primary proton and helium components
is described here and the results are compared with other recent measurements
using other magnet spectrometers. The observed energy spectra at the top of the
atmosphere can be represented by (1.27+-0.09)x10^4 E^(-2.75+-0.02) particles
(m^2 GeV sr s)^-1, where E is the kinetic energy, for protons between 20 and
350 GeV and (4.8+-0.8)x10^2 E^(-2.67+-0.06) particles (m^2 GeV nucleon^-1 sr
s)^-1, where E is the kinetic energy per nucleon, for helium nuclei between 15
and 150 GeV nucleon^-1.Comment: To be published on Astroparticle Physics (44 pages, 13 figures, 5
tables
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