1,131 research outputs found
Electromagnetic Form Factors of Charged and Neutral Kaons
The charged and neutral kaon form factors are calculated as a
phenomenological application of the QCD Dyson-Schwinger equations. The results
are compared with the pion form factor calculated in the same framework and
yield \mbox{} on
\mbox{~GeV}; and a neutral kaon form factor that is similar in
form and magnitude to the neutron charge form factor. These results are
sensitive to the difference between the kaon and pion Bethe-Salpeter amplitude
and the - and -quark propagation characteristics.Comment: 11 Pages, 2 figures, REVTEX, uses epsfig. No chang
Hard Constituent Quarks and Electroweak Properties of Pseudoscalar Mesons
The high momentum components generated in the wave function of pseudoscalar
mes* by the one-gluon-exchange interaction are investigated within a
relativistic constituent quark model. Adopting the light-cone formalism, the
sensitivity of the weak decay constant and the charge form factor to hard
constituent quarks is illustrated.Comment: 11 pages and 5 figs. (to be requested), LaTeX, INFN-ISS 94/3. To
appear in Physics Lett.
Off-shell pion electromagnetic form factor from a gauge-invariant Nambu-Jona-Lasinio model
The off--shell electromagnetic vertex function of pions and kaons is studied
in a bosonized Nambu--Jona-Lasinio model with a gauge--invariant proper--time
cutoff. The slope of the pion form factor with respect to the pion 4--momentum
is found to be equal to the on--shell pion charge radius in the chiral limit.
The off--shell slope of the form factor is zero, that of the
about 15\% smaller than that of the pion. We compare our results with those of
a recent calculation in chiral perturbation theory.Comment: (9 p., standard LaTeX, 1 PostScript figure appended) UNITUE-THEP-7/9
Position Sensing from Charge Dispersion in Micro-Pattern Gas Detectors with a Resistive Anode
Micro-pattern gas detectors, such as the Gas Electron Multiplier (GEM) and
the Micromegas need narrow high density anode readout elements to achieve good
spatial resolution. A high-density anode readout would require an unmanageable
number of electronics channels for certain potential micro-detector
applications such as the Time Projection Chamber. We describe below a new
technique to achieve good spatial resolution without increasing the electronics
channel count in a modified micro-detector outfitted with a high surface
resistivity anode readout structure. The concept and preliminary measurements
of spatial resolution from charge dispersion in a modified GEM detector with a
resistive anode are described below.Comment: 14 pages, 8 figures, submitted to Nucl. Inst. Meth; typo in eqn 4
corrected, fig 2 updated accordingl
The interplay of soft and hard contributions in the electromagnetic pion form factor
We consider various relativistic models for the valence Fock-state wave
function of the pion. These models are obtained from simple instant-form wave
functions by applying a Melosh rotation to the spin part and by imposing
physical constraints on the parameters. We discuss how the soft and the hard
(perturbative) parts of the electromagnetic form factor are affected by the
choice of the model and by the Melosh rotation.Comment: 3 pages, 2 eps-figures, uses espcrc2.st
Corrections to Sirlin's Theorem in Chiral Perturbation Theory
We present the results of the first two-loop calculation of a form factor in
full Chiral Perturbation Theory. We choose a specific
linear combination of and form factors (the one
appearing in Sirlin's theorem) which does not get contributions from order
operators with unknown constants. For the charge radii, the correction to
the previous one-loop result turns out to be significant, but still there is no
agreement with the present data due to large experimental uncertainties in the
kaon charge radii.Comment: 6 pages, Latex, 2 LaTeX figure
Electroweak properties of the , and in the three forms of relativistic kinematics
The electromagnetic form factors, charge radii and decay constants of pion, K
and K*(892) are calculated using the three forms of relativistic kinematics:
instant form, point form and (light) front form. Simple representations of the
mass operator together with single quark currents are employed with all the
forms. Making use of previously fixed parameters, together with the constituent
quark mass for the strange quark, a reasonable reproduction of the available
data for form factors, charge radii and decay constants of pion, rho, K and
K*(892) is obtained in front form. With instant form a similar description, but
with a systematic underestimation of the vector meson decay constants is
obtained using two different sets of parameters, one for pion and rho and
another one for K and K*(892). Point form produces a poor description of the
data.Comment: Accepted in Eur. Phys. Jour. A (2005
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