80 research outputs found
New experimental data for the decays and from SND detector
The processes and have been
studied with SND detector at VEPP-2M collider in the vicinity of
resonance. The branching ratios and were obtained.Comment: 5 pages, 4 figures, talk given at 8th International Conference on
Hadron Spectroscopy (HADRON 99), Beijing, China, 24-28 Aug 199
Quark-Resonance model
We construct an effective Lagrangian for low energy hadronic interactions
through an infinite expansion in inverse powers of the low energy cutoff
of all possible chiral invariant non-renormalizable interactions
between quarks and mesons degrees of freedom. We restrict our analysis to the
leading terms in the expansion. The effective expansion is in
(\mu^2/\cutoff^2 )^P \ln (\cutoff^2/\mu^2 )^Q. Concerning the next-to-leading
order, we show that, while the pure \mu^2/\cutoff^2 corrections cannot be
traced back to a finite number of non renormalizable interactions, those of
order (\mu^2/\cutoff^2 ) \ln (\cutoff^2/\mu^2 ) receive contributions from a
finite set of 1/\cutoff^2 terms. Their presence modifies the behaviour of
observable quantities in the intermediate region. We explicitely discuss
their relevance for the two point vector currents Green's function.Comment: 41 pages, 11 figures, preprint ROM2F 93/3
Measurement of omega meson parameters in pi^+pi^-pi^0 decay mode with CMD-2
About 11 200 e^+e^- -> omega -> pi^+pi^-pi^0 events selected in the center of
mass energy range from 760 to 810 MeV were used for the measurement of the
\omega meson parameters. The following results have been obtained: sigma
_{0}=(1457 \pm 23 \pm 19)nb, m_{\omega}=(782.71 \pm 0.07 \pm 0.04) MeV/c^{2},
\Gamma_{\omega}=(8.68 \pm 0.23 \pm 0.10) MeV,
\Gamma_{e^+e^-}\cdot Br (\omega -> pi^+pi^-pi^0)=
(0.528 \pm 0.012 \pm 0.007) \cdot 10^{-3} MeV.Comment: 8 pages, 4 figure
A partial wave analysis of the centrally produced K+K- and K0K0 systems in pp interactions at 450 GeV/c and new information on the spin of the fJ(1710)
A partial wave analysis of the centrally produced K+K- and K0K0 channels has
been performed in pp collisions using an incident beam momentum of 450 GeV/c.
An unambiguous physical solution has been found in each channel. The striking
feature is the observation of peaks in the S-wave corresponding to the f0(1500)
and fJ(1710) with J = 0. The D-wave shows evidence for the f2(1270)/a2(1320),
the f2(1525) and the f2(2150) but there is no evidence for a statistically
significant contribution in the D-wave in the 1.7 GeV mass region.Comment: 15 pages, Latex, 5 Figure
Very-high energy gamma-ray astronomy: A 23-year success story in high-energy astroparticle physics
Very-high energy (VHE) gamma quanta contribute only a minuscule fraction -
below one per million - to the flux of cosmic rays. Nevertheless, being neutral
particles they are currently the best "messengers" of processes from the
relativistic/ultra-relativistic Universe because they can be extrapolated back
to their origin. The window of VHE gamma rays was opened only in 1989 by the
Whipple collaboration, reporting the observation of TeV gamma rays from the
Crab nebula. After a slow start, this new field of research is now rapidly
expanding with the discovery of more than 150 VHE gamma-ray emitting sources.
Progress is intimately related with the steady improvement of detectors and
rapidly increasing computing power. We give an overview of the early attempts
before and around 1989 and the progress after the pioneering work of the
Whipple collaboration. The main focus of this article is on the development of
experimental techniques for Earth-bound gamma-ray detectors; consequently, more
emphasis is given to those experiments that made an initial breakthrough rather
than to the successors which often had and have a similar (sometimes even
higher) scientific output as the pioneering experiments. The considered energy
threshold is about 30 GeV. At lower energies, observations can presently only
be performed with balloon or satellite-borne detectors. Irrespective of the
stormy experimental progress, the success story could not have been called a
success story without a broad scientific output. Therefore we conclude this
article with a summary of the scientific rationales and main results achieved
over the last two decades.Comment: 45 pages, 38 figures, review prepared for EPJ-H special issue "Cosmic
rays, gamma rays and neutrinos: A survey of 100 years of research
Observation of Pseudoscalar and Axial Vector Resonances in pi- p -> K+ K- pi0 n at 18 GeV
A new measurement of the reaction pi- p -> K+ K- pi0 n has been made at a
beam energy of 18 GeV. A partial wave analysis of the K+ K- pi0 system shows
evidence for three pseudoscalar resonances, eta(1295), eta(1416), and
eta(1485), as well as two axial vectors, f1(1285), and f1(1420). Their observed
masses, widths and decay properties are reported. No signal was observed for
C(1480), an IG J{PC} = 1+ 1{--} state previously reported in phi pi0 decay.Comment: 7 pages, 6 figs, to be submitted to Phys. Let
Mapping the drivers of parasitic weed abundance at a national scale : a new approach applied to Striga asiatica in the midâwest of Madagascar
The parasitic weed genus Striga causes huge losses to crop production in subâSaharan Africa, estimated to be in excess of $7 billion per year. There is a paucity of reliable distribution data for Striga ; however, such data are urgently needed to understand current drivers, better target control efforts, as well as to predict future risks. To address this, we developed a methodology to enable rapid, largeâscale monitoring of Striga populations. We used this approach to uncover the factors that currently drive the abundance and distribution of Striga asiatica in Madagascar. Two longâdistance transects were established across the middleâwest region of Madagascar in which S. asiatica abundance in fields adjacent to the road was estimated. Management, crop structure and soil data were also collected. Analysis of the data suggests that crop variety, companion crop and previous crop were correlated with Striga density. A positive relationship between withinâfield Striga density and the density of the nearest neighbouring fields indicates that spatial configuration and connectivity of suitable habitats is also important in determining Striga spread. Our results demonstrate that we are able to capture distribution and management data for Striga density at a landscape scale and use this to understand the ecological and agronomic drivers of abundance. The importance of crop varieties and cropping patterns is significant, as these are key socioâeconomic elements of Malagasy cropping practices. Therefore, they have the potential to be promoted as readily available control options, rather than novel technologies requiring introduction
Del malo pecado al pecado intrĂnsecamente malo: la radicalizaciĂłn fundamentalista de la homofobia catĂłlica desde los tiempos de la InquisiciĂłn hasta Benedicto XVI
Study of doubly strange systems using stored antiprotons
Bound nuclear systems with two units of strangeness are still poorly known despite their importance for many strong interaction phenomena. Stored antiprotons beams in the GeV range represent an unparalleled factory for various hyperon-antihyperon pairs. Their outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of systems which contain two or even more units of strangeness at the PâŸANDA experiment at FAIR. For the first time, high resolution Îł-spectroscopy of doubly strange ÎÎ-hypernuclei will be performed, thus complementing measurements of ground state decays of ÎÎ-hypernuclei at J-PARC or possible decays of particle unstable hypernuclei in heavy ion reactions. High resolution spectroscopy of multistrange Îâ-atoms will be feasible and even the production of Ωâ-atoms will be within reach. The latter might open the door to the |S|=3 world in strangeness nuclear physics, by the study of the hadronic Ωâ-nucleus interaction. For the first time it will be possible to study the behavior of ÎâŸ+ in nuclear systems under well controlled conditions
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