2,536 research outputs found
Form factor in K+ --> pi+ pi0 gamma: interference versus direct emission
We analyze the effect of a form factor in the magnetic contribution to K+ -->
pi+ pi0 gamma. We emphasize how this can show up experimentally: in particular
we try to explore the difference between a possible interference contribution
and a form factor in the magnetic part. The form factor used for K+ --> pi+ pi0
gamma is analogous to the one for KL --> pi+ pi- gamma, experimentally well
established.Comment: 9 pages revtex, 10 eps figures; improved presentation of theoretical
and experimental status; refs. adde
Precision Measurement of KS Meson Lifetime with the KLOE detector
Using a large sample of pure, slow, short lived K0 mesons collected with KLOE
detector at DaFne, we have measured the KS lifetime. From a fit to the proper
time distribution we find tau = (89.562 +- 0.029_stat +- 0.043_syst) ps. This
is the most precise measurement today in good agreement with the world average
derived from previous measurements. We observe no dependence of the lifetime on
the direction of the Ks.Comment: 5 pages, 7 figure
A New Fast Silicon Photomultiplier Photometer
The realization of low-cost instruments with high technical performance is a
goal which deserves some efforts in an epoch of fast technological
developments: indeed such instruments can be easily reproduced and therefore
allow to open new research programs in several Observatories. We realized a
fast optical photometer based on the SiPM technology, using commercially
available modules. Using low-cost components we have developed a custom
electronic chain to extract the signal produced by a commercial MPPC module
produced by Hamamatsu, in order to obtain sub millisecond sampling of the light
curve of astronomical sources, typically pulsars. In the early February 2011 we
observed the Crab Pulsar at the Cassini telescope with our prototype
photometer, deriving its period, power spectrum and shape of its light curve in
very good agreement with the results obtained in the past with other
instruments.Comment: Accepted for Publications of the Astronomical Society of Pacific
(PASP), 8 pages, 8 figure
Vacuum Properties of Mesons in a Linear Sigma Model with Vector Mesons and Global Chiral Invariance
We present a two-flavour linear sigma model with global chiral symmetry and
vector and axial-vector mesons. We calculate pion-pion scattering lengths and
the decay widths of scalar, vector, and axial-vector mesons. It is demonstrated
that vector and axial-vector meson degrees of freedom play an important role in
these low-energy processes and that a reasonable theoretical description
requires globally chirally invariant terms other than the vector meson mass
term. An important question for meson vacuum phenomenology is the quark content
of the physical scalar f0(600) and a0(980) mesons. We investigate this question
by assigning the quark-antiquark sigma and a0 states of our model with these
physical mesons. We show via a detailed comparison with experimental data that
this scenario can describe all vacuum properties studied here except for the
decay width of the sigma, which turns out to be too small. We also study the
alternative assignment f0(1370) and a0(1450) for the scalar mesons. In this
case the decay width agrees with the experimental value, but the pion-pion
scattering length is too small. This indicates the necessity to
extend our model by additional scalar degrees of freedom.Comment: 22 pages, 6 figure
Two-body hadronic charmed meson decays
We study in this work the two-body hadronic charmed meson decays, including
both the PP and VP modes. The latest experimental data are first analyzed in
the diagrammatic approach. The magnitudes and strong phases of the flavor
amplitudes are extracted from the Cabibbo-favored (CF) decay modes using
minimization. The best-fitted values are then used to predict the
branching fractions of the singly-Cabibbo-suppressed (SCS) and
doubly-Cabibbo-suppressed decay modes in the flavor SU(3) symmetry limit. We
observe significant SU(3) breaking effects in some of SCS channels. In the case
of VP modes, we point out that the and amplitudes cannot be
completely determined based on currently available data. We conjecture that the
quoted experimental results for both and are overestimated. We compare the sizes of color-allowed and
color-suppressed tree amplitudes extracted from the diagrammatical approach
with the effective parameters and defined in the factorization
approach. The ratio is more or less universal among the , and modes. This feature allows
us to discriminate between different solutions of topological amplitudes. For
the long-standing puzzle about the ratio , we argue that, in addition to the SU(3)
breaking effect in the spectator amplitudes, the long-distance resonant
contribution through the nearby resonance can naturally explain why
decays more copiously to than through the
-exchange topology.Comment: 32 pages, 5 figures. An alternative method for error bar extraction
is used; last columns of Tables~I to VI, and all entries in Tables~VII, VIII
and X are modified. To appear in PRD
Study of the process e+e- -> omega pi0 in the phi-meson mass region with the KLOE detector
We have studied the e+e- -> omegapi0 cross section in the sqrt(s) interval
1000-1030 MeV using the pi+pi-pi0pi0 and pi0pi0gamma final states with a sample
of ~600 pb^-1 collected with the KLOE detector at DAFNE. By fitting the
observed interference pattern around M_phi for both final states, we extract
the ratio of the decay widths Gamma(omega->pi0gamma)/Gamma(omega->pi+pi-pi0) =
0.0897 +- 0.0016 and derive the branching fractions BR(omega -> pi+pi-pi0)=
(90.24 +- 0.19)%, BR(omega -> pi0gamma) = (8.09 +- 0.14)%. The parameters
describing the e+e- -> omegapi0 reaction around M_\phi are also used to extract
the branching fraction for the OZI and G-parity violating phi -> omegapi0
decay: BR(phi->omegapi0) = (4.4 +- 0.6)x10^-5.Comment: 12 Pages, 4 figures, submitted to Physics Letter
Soil contribution on the structural identification of a historical masonry bell-tower: simplified vs advanced numerical models
In the last decade, structural identification techniques through dynamic in situ tests have been widely used to investigate the global dynamic behavior of ordinary buildings and built cultural heritage. The choice of proper boundary conditions at the base of the structure, however, is still a critical point in the development of sound numerical models able to reproduce building dynamic response reliably. The contribution of the foundation soil should be ascertained and, if necessary, properly modelled. The paper tries to shed light on the issue of soil-structure-interaction on the structural identification of masonry towers, with reference to the case study of the bell tower of Santa Sofia Church in Benevento (Italy). The experimental results of the dynamic identification, i.e. frequencies and modal shapes, have been interpreted and employed to calibrate both simplified and advanced numerical models of the soil-foundation-tower system. In the first case, soil compliance is represented by a set of springs attached at the base of the tower, which has been modelled as a 1D system. In the second case, a 3D finite element model comprehensive of the tower, the soil and the foundation structure has been developed. Pros and cons of the two numerical approaches on the structural identification process are highlighted and discussed.The authors thank Prof. Maria Rosaria Pecce for her precious support and suggestions. This research
activity was carried out within the framework of the PON Research and Innovation 2014–2020, Axis I-Investments in Human Capital, MIUR notice AIM-“International Attraction and Mobility”- Line 1, Project: AIM 1823125-3 – Cultural Heritage. Part of the work has been developed in the framework of the 2019-2021 Reluis-DPC research program funded by the Italian Civil Protection Department, as a contribution to the geotechnical Work Package Soil-Foundation-Structure Interaction (Task 16.3)
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