684 research outputs found
Meson model for f_0(980) production in peripheral pion-nucleon reactions
The Juelich model for pion-pion-scattering, based on an effective meson-meson
Lagrangian is applied to the analysis of the S-wave production amplitudes
derived from the BNL E852 experiment pi^- p -> pi^0 pi^0 n for a pion momentum
of 18.3 GeV. The unexpected strong dependence of the S-wave partial wave
amplitude on the momentum transfer between the proton and neutron in the
vicinity of the f_0(980) resonance is explained in our analysis as interference
effect between the correlated and uncorrelated pi^0 pi^0 pairs.Comment: 6 pages, 7 figures, formulas added, typos removed, new figure
Study of the reaction pbar p -> phi phi from 1.1 to 2.0 GeV/c
A study has been performed of the reaction pbar p -> 4K using in-flight
antiprotons from 1.1 to 2.0 GeV/c incident momentum interacting with a hydrogen
jet target. The reaction is dominated by the production of a pair of phi
mesons. The pbar p -> phi phi cross section rises sharply above threshold and
then falls continuously as a function of increasing antiproton momentum. The
overall magnitude of the cross section exceeds expectations from a simple
application of the OZI rule by two orders of magnitude. In a fine scan around
the xi/f_J(2230) resonance, no structure is observed. A limit is set for the
double branching ratio B(xi -> pbar p) * B(xi -> phi phi) < 6e-5 for a spin 2
resonance of M = 2.235 GeV and Width = 15 MeV.Comment: 13 pages, 13 figures, 2 tables, Latex. To be published in Phys. Rev.
Optimal Flying Wings: A Numerical Optimization Study
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97067/1/AIAA2012-1758.pd
Couplings of light I=0 scalar mesons to simple operators in the complex plane
The flavour and glue structure of the light scalar mesons in QCD are probed
by studying the couplings of the I=0 mesons and to the
operators , and to two photons. The Roy dispersive
representation for the amplitude is used to determine the
pole positions as well as the residues in the complex plane. On the real axis,
is constrained to solve the Roy equation together with elastic
unitarity up to the K\Kbar threshold leading to an improved description of
the . The problem of using a two-particle threshold as a matching
point is discussed. A simple relation is established between the coupling of a
scalar meson to an operator and the value of the related pion form-factor
computed at the resonance pole. Pion scalar form-factors as well as two-photon
partial-wave amplitudes are expressed as coupled-channel Omn\`es dispersive
representations. Subtraction constants are constrained by chiral symmetry and
experimental data. Comparison of our results for the couplings with
earlier determinations of the analogous couplings of the lightest I=1 and
scalar mesons are compatible with an assignment of the ,
, , into a nonet. Concerning the gluonic operator
we find a significant coupling to both the and the
.Comment: 31 pages, 5 figure
Two Birds, One Stone? Positive Mood Makes Products Seem Less Useful for Multiple-Goal Pursuit
Medicinal Plant Use and Health Sovereignty: Findings from the Tajik and Afghan Pamirs
Medicinal plants are indicators of indigenous
knowledge in the context of political volatility and sociocultural
and ecological change in the Pamir Mountains of
Afghanistan and Tajikistan. Medicinal plants are the
primary health care option in this region of Central Asia.
The main objective of this paper is to demonstrate that
medicinal plants contribute to health security and sovereignty
in a time of instability. We illustrate the nutritional
as well as medicinal significance of plants in the daily
lives of villagers. Based on over a decade and half of
research related to resilience and livelihood security, we
present plant uses in the context of mountain communities.
Villagers identified over 58 cultivated and noncultivated
plants and described 310 distinct uses within
63 categories of treatment and prevention. Presence of
knowledge about medicinal plants is directly connected to
their use
Deficient prefrontal attentional control in late-life generalized anxiety disorder: an fMRI investigation
Younger adults with anxiety disorders are known to show an attentional bias toward negative information. Little is known regarding the role of biased attention in anxious older adults, and even less is known about the neural substrates of any such bias. Functional magnetic resonance imaging (fMRI) was used to assess the mechanisms of attentional bias in late life by contrasting predictions of a top-down model emphasizing deficient prefrontal cortex (PFC) control and a bottom-up model emphasizing amygdalar hyperreactivity. In all, 16 older generalized anxiety disorder (GAD) patients (mean age=66 years) and 12 non-anxious controls (NACs; mean age=67 years) completed the emotional Stroop task to assess selective attention to negative words. Task-related fMRI data were concurrently acquired. Consistent with hypotheses, GAD participants were slower to identify the color of negative words relative to neutral, whereas NACs showed the opposite bias, responding more quickly to negative words. During negative words (in comparison with neutral), the NAC group showed PFC activations, coupled with deactivation of task-irrelevant emotional processing regions such as the amygdala and hippocampus. By contrast, GAD participants showed PFC decreases during negative words and no differences in amygdalar activity across word types. Across all participants, greater attentional bias toward negative words was correlated with decreased PFC recruitment. A significant positive correlation between attentional bias and amygdala activation was also present, but this relationship was mediated by PFC activity. These results are consistent with reduced prefrontal attentional control in late-life GAD. Strategies to enhance top-down attentional control may be particularly relevant in late-life GAD treatment
Measurement of the pbar p -> Ks Ks Reaction from 0.6 to 1.9 GeV/c
The pbar p -> Ks Ks -> 4pi+/- cross section was measured at incident
antiproton momenta between 0.6 and 1.9 GeV/c using the CERN Low Energy
Antiproton Ring (LEAR). This investigation was part of a systematic study of
in-flight antiproton-proton annihilations into two-neutral-meson final states
in a search for hadronic resonances. A coarse scan of the pbar p -> Ks Ks cross
section as a function of center-of-mass energy between 1.964 and 2.395 GeV/c^2
and a fine scan of the region surrounding the Xi(2220) are presented. Upper
limits on the product branching ratio BR(Xi -> pbar p)BR(Xi -> Ks Ks) are
determined for a wide range of mass and width assumptions based on the
non-observation of the Xi(2220). A rise in the pbar p -> Ks Ks cross section is
observed near 2.15 GeV/c^2, which is consistent with the f2(2150) resonance.Comment: 11 pages, Latex, to be published in Phys Rev D (Oct 97
Strong Decays of Strange Quarkonia
In this paper we evaluate strong decay amplitudes and partial widths of
strange mesons (strangeonia and kaonia) in the 3P0 decay model. We give
numerical results for all energetically allowed open-flavor two-body decay
modes of all nsbar and ssbar strange mesons in the 1S, 2S, 3S, 1P, 2P, 1D and
1F multiplets, comprising strong decays of a total of 43 resonances into 525
two-body modes, with 891 numerically evaluated amplitudes. This set of
resonances includes all strange qqbar states with allowed strong decays
expected in the quark model up to ca. 2.2 GeV. We use standard nonrelativistic
quark model SHO wavefunctions to evaluate these amplitudes, and quote numerical
results for all amplitudes present in each decay mode. We also discuss the
status of the associated experimental candidates, and note which states and
decay modes would be especially interesting for future experimental study at
hadronic, e+e- and photoproduction facilities. These results should also be
useful in distinguishing conventional quark model mesons from exotica such as
glueballs and hybrids through their strong decays.Comment: 69 pages, 5 figures, 39 table
Dispersive analysis of the scalar form factor of the nucleon
Based on the recently proposed Roy-Steiner equations for pion-nucleon
scattering, we derive a system of coupled integral equations for the pi pi -->
N-bar N and K-bar K --> N-bar N S-waves. These equations take the form of a
two-channel Muskhelishvili-Omnes problem, whose solution in the presence of a
finite matching point is discussed. We use these results to update the
dispersive analysis of the scalar form factor of the nucleon fully including
K-bar K intermediate states. In particular, we determine the correction
Delta_sigma=sigma(2M_pi^2)-sigma_{pi N}, which is needed for the extraction of
the pion-nucleon sigma term from pi N scattering, as a function of pion-nucleon
subthreshold parameters and the pi N coupling constant.Comment: 24 pages, 6 figures; version published in JHE
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