588 research outputs found
Selected topics on Hadrons in Nuclei
In this talk we report on selected topics on hadrons in nuclei. The first
topic is the renormalization of the width of the in a nuclear
medium. This is followed by a short update of the situation of the in
the medium. The investigation of the properties of in the nuclear
medium from the study of the reaction is also addressed, as
well as properties of X,Y,Z charmed and hidden charm resonances in a nuclear
medium. Finally we address the novel issue of multimeson states.Comment: Talk at the International Nuclear Physics Conference, Vancouver, July
201
Photoproduction of eta-mesons on the deuteron above S11(1535) in the presence of a narrow P11(1670) resonance
Incoherent photoproduction of eta-mesons on the deuteron is considered. The
main attention is paid to the region above the S11(1535) resonance where rather
narrow resonance like structure in the total cross section extracted for gamma
n -> eta n has been reported. The corresponding experimental results are
analyzed from the phenomenological standpoint within the model containing a
baryon P11 with the mass about 1670 MeV and a width less than 30 MeV. This
resonance was suggested in some recent works as a nonstrange member of the
pentaquark antidecuplet with J^P=1/2^+. The calculation is also performed for
the polarized and nonpolarized angular distributions of mesons. In
addition, we present our predictions for the cross sections of the neutral
kaons and double pion photoproduction, where the same narrow P11(1670)
resonance is assumed to contribute through the decay into K^0 Lambda and pi
Delta configuration.Comment: 11 pages, 5 figure
Primakoff effect in eta-photoproduction off protons
We analyse data on forward eta-meson photoproduction off a proton target and
extract the eta to gamma gamma decay width utilizing the Primakoff effect. The
hadronic amplitude that enters into our analysis is strongly constrained
because it is fixed from a global fit to available gamma p to p eta data for
differential cross sections and polarizations. We compare our results with
present information on the two-photon eta-decay from the literature. We provide
predictions for future PrimEx experiments at Jefferson Laboratory in order to
motivate further studies.Comment: 5 pages, 6 figures, gamma-gamma*-eta form factor included, version to
appear in Eur. Phys. J. A
Using the common-sense model to understand health outcomes for medically unexplained symptoms: a meta-analysis
Consistent with the common-sense model of self-regulation, illness representations are considered the key to improving health outcomes for medically unexplained symptoms and illnesses (MUS). Which illness representations are related to outcomes and how they are related is not well understood. In response, we conducted a meta-analysis of the relationship between illness representations, self-management/coping, and health outcomes (perceived disease state, psychological distress, and quality of life) for patients with MUS. We reviewed 23 studies and found that threat-related illness representations and emotional representations were related to worse health outcomes and more negative coping (moderate to large effect). Generally, increases in negative coping mediated (with a moderate to large effect) the relationship of threat/emotional illness representations and health outcomes. Protective illness representations were related to better health outcomes, less use of negative coping and greater use of positive coping (small to moderate effect). The relationship of protective illness representations to better health outcomes was mediated by decreases in negative coping (moderate to large effect) and increases in positive coping (moderate effect). Perceiving a psychological cause to the MUS was related to more negative health outcomes (moderate to large effect) and more negative emotional coping (small effect). The relationship of perceiving a psychological cause and more negative health outcomes was mediated by increases in negative emotional coping. Improving our understanding of how illness representations impact health outcomes can inform efforts to improve treatments for MUS. Our results suggest behavioural treatments should focus on reducing threat-related illness representations and negative coping
Exploration of hyperfine interaction between constituent quarks via eta productions
In this work, the different exchange freedom, one gluon, one pion or
Goldstone boson, in constituent quark model is investigated, which is
responsible to the hyperfine interaction between constituent quarks, via the
combined analysis of the eta production processes,
and . With the Goldstone-boson exchange, as well as
the one-gluon or one-pion exchange, both the spectrum and observables, such as,
the differential cross section and polarized beam asymmetry, are fitted to the
suggested values of Particle Data Group and the experimental data. The first
two types of exchange freedoms give acceptable description of the spectrum and
observables while the one pion exchange can not describe the observables and
spectrum simultaneously, so can be excluded. The experimental data for the two
processes considered here strongly support the mixing angles for two lowest S11
sates and D13 states as about -30 and 6 degree respectively.Comment: 7 pages, 4 figures, 4 table
Note on the definitions of branching ratios of overlapping resonances
Branching ratios for the decay of hadrons with large width or near thresholds
depend on their definition. We test different definitions and show that rather
different branching ratios can be obtained. For wide resonances and for
sequential decays with wide intermediate resonances, integration over the
spectral functions is mandatory. The tests are performed exploiting the latest
solution of the Bonn-Gatchina multi-channel analysis and published values for
residues of light scalar mesons. For a resonance overlapping with a threshold,
in case its pole lies in a non-adjacent sheet, we show how the total width,
needed for the branching ratios, does not correspond to the imaginary part of
the pole position. We use the Madrid-Krakow dispersive parameterizations to
illustrate this situation with the .Comment: Report, 9 pages (extended to light scalar mesons
Comment on the narrow structure reported by Amaryan et al
The CLAS Collaboration provides a comment on the physics interpretation of
the results presented in a paper published by M. Amaryan et al. regarding the
possible observation of a narrow structure in the mass spectrum of a
photoproduction experiment.Comment: to be published in Physical Review
A comparison of forward and backward pp pair knockout in 3He(e,e'pp)n
Measuring nucleon-nucleon Short Range Correlations (SRC) has been a goal of
the nuclear physics community for many years. They are an important part of the
nuclear wavefunction, accounting for almost all of the high-momentum strength.
They are closely related to the EMC effect. While their overall probability has
been measured, measuring their momentum distributions is more difficult. In
order to determine the best configuration for studying SRC momentum
distributions, we measured the He reaction, looking at events
with high momentum protons ( GeV/c) and a low momentum neutron
( GeV/c). We examined two angular configurations: either both protons
emitted forward or one proton emitted forward and one backward (with respect to
the momentum transfer, ). The measured relative momentum distribution
of the events with one forward and one backward proton was much closer to the
calculated initial-state relative momentum distribution, indicating that
this is the preferred configuration for measuring SRC.Comment: 8 pages, 9 figures, submitted to Phys Rev C. Version 2 incorporates
minor corrections in response to referee comment
Target and beam-target spin asymmetries in exclusive pion electroproduction for Q2>1GeV2 . I. epâeÏ+n
Beam-target double-spin asymmetries and target single-spin asymmetries were measured for the exclusive
Ï
+
electroproduction reaction
Îł
â
p
â
n
Ï
+
. The results were obtained from scattering of 6-GeV longitudinally polarized electrons off longitudinally polarized protons using the CEBAF Large Acceptance Spectrometer at Jefferson Laboratory. The kinematic range covered is
1.1
<
W
<
3
GeV and
1
<
Q
2
<
6
GeV
2
. Results were obtained for about 6000 bins in
W
,
Â
Q
2
,
Â
cos
(
Ξ
â
)
, and
Ï
â
. Except at forward angles, very large target-spin asymmetries are observed over the entire
W
region. Reasonable agreement is found with phenomenological fits to previous data for
W
<
1.6
GeV, but very large differences are seen at higher values of
W
. A generalized parton distributions (GPD)-based model is in poor agreement with the data. When combined with cross-sectional measurements, the present results provide powerful constraints on nucleon resonance amplitudes at moderate and large values of
Q
2
, for resonances with masses as high as 2.4 GeV
- âŠ