559 research outputs found
Hints on the quadrupole deformation of the (1232)
The E2/M1 ratio (EMR) of the (1232) is extracted from the world data
in pion photoproduction by means of an Effective Lagrangian Approach (ELA).This
quantity has been derived within a crossing symmetric, gauge invariant, and
chiral symmetric Lagrangian model which also contains a consistent modern
treatment of the (1232) resonance. The \textit{bare} s-channel
(1232) contribution is well isolated and Final State Interactions (FSI)
are effectively taken into account fulfilling Watson's theorem. The obtained
EMR value, EMR%, is in good agreement with the latest lattice
QCD calculations [Phys. Rev. Lett. 94, 021601 (2005)] and disagrees with
results of current quark model calculations.Comment: Enlarged conclusions and explanations on the E2/M1 ratio. Figure 3
improved. References updated. 5 pages. 3 figures. 2 tables. Accepted for
publication in Physical Review
On the Determination of and from Hadronic Two Body Decays
{}From Class I decays : B^o \ra \pi^+ ( \rho^+ ) + D^- ( {D^*}^- ), we
determine , and from Class III decays : B^+ \ra \pi^+ ( \rho^+ ) +
\ol{D}^o ( {\ol{D}^*}^o ), we determine an allowed domain in the plane. We find that within one standard deviation errors, the allowed band
of from Class I decays is at least three standard deviations removed from
the allowed domain from Class III decays.If we expand the
experimental errors to two standard deviations we do find a small intersection
between the band and the allowed domain. The results
usually quoted in the literature lie in this intersection. We suggest : (1) an
independent measurement of the branching ratio for the Class III decay, B^+
\ra \rho^+ \ol{D}^o , (2) a high-statistics measurement of the branching ratio
of the Class I decay, B \ra \ol{D} ( \ol{D}^* ) + D_s ( D_s^* ) in both
charged states, and (3) a measurement of the longitudinal polarization fraction
in the Class III decay B^+ \ra \rho^+ {\ol{D}^*}^o to shed more light on the
questions involved .Comment: 9pages(Latex)+4 figures(PS file appended), PAR/LPTHE/94-2
Mean eigenvalues for simple, simply connected, compact Lie groups
We determine for each of the simple, simply connected, compact and complex
Lie groups SU(n), Spin and that particular region inside the unit
disk in the complex plane which is filled by their mean eigenvalues. We give
analytical parameterizations for the boundary curves of these so-called trace
figures. The area enclosed by a trace figure turns out to be a rational
multiple of in each case. We calculate also the length of the boundary
curve and determine the radius of the largest circle that is contained in a
trace figure. The discrete center of the corresponding compact complex Lie
group shows up prominently in the form of cusp points of the trace figure
placed symmetrically on the unit circle. For the exceptional Lie groups ,
and with trivial center we determine the (negative) lower bound on
their mean eigenvalues lying within the real interval . We find the
rational boundary values -2/7, -3/13 and -1/31 for , and ,
respectively.Comment: 12 pages, 8 figure
Test of the reaction mechanism for gamma N -> K Lambda(1520) using the polarized photon
We study the reaction mechanism for the photoproduction of the Lambda(1520),
based on an effective Lagrangian approach. We investigate each contribution of
the s-, u-, t-channel processes and contact term, separately. One of the most
characteristic features of this reaction is the contact-term dominance which
governs the photoproduction from the proton, when the K*-exchange contribution
is possibly not too large. We suggest several different ways of the
polarizations and arrangement of the beam and target to make to understand the
role of each contribution separately in future experiments.Comment: 10 pages, 14 figures, accepted for publication in PR
Nonfactorization and the decays and
In six chosen scenarios for the dependence of the form factors involved
in transition, we have determined the allowed domain
of and from the experimentally measured
ratios and in a scheme that uses the value of the phenomenological parameter and includes nonfactorized
contribution. We find that the experimentally measured values of and
from semileptonic decays of favor solutions which have significant
nonfactorized contribution, and, in particular, favors solutions in
scenarios where is either flat or decreasing with .Comment: 15 pages, Latex, four figure (available on request)
Characterization of thermo-mechanical behavior of insulated cable stacks representative of accelerator magnet coils
Ageing influences the effect of pre-hypoxic administration of clonidine, an alpha₂-adrenoceptor agonist, on post-hypoxic vasomotricity
- …