86 research outputs found
Photoproduction of the Theta^+ and its vector and axial-vector structure
We present recent investigations on the vector and axial-vector transitions
of the baryon antidecuplet within the framework of the self-consistent SU(3)
chiral quark-soliton model, taking into account the 1/N_c rotational and linear
m_s corrections. The main contribution to the electric-like transition form
factor comes from the wave-function corrections. This is a consequence of the
generalized Ademollo-Gatto theorem. It is also found that in general the
leading-order contributions are almost canceled by the rotational 1/N_c
corrections. The results are summarized as follows: the vector and tensor
K^*-N-Theta coupling constants, g_{K^*-N-Theta}=0.74 - 0.87 and
f_{K^*-N-Theta}=0.53 - 1.16, respectively, and Gamma_{Theta->KN}=0.71 MeV,
based on the result of the K-N-Theta coupling constant g_{K-n-Theta}=0.83. We
also show the differential cross sections and beam asymmetries, based on the
present results. We also discuss the connection of present results with the
original work by Diakonov, Petrov, and Polyakov.Comment: 9 pages, 6 figures, An invited talk given at the Workshop of Excited
Nucleon - NSTAR2009 held in Beijing, April 19-22 200
Observation of a narrow structure in p(gamma,K_s)X via interference with phi-meson production
We report observation of a narrow peak structure at ~1.54 GeV with a Gaussian
width sigma=6 MeV in the missing of K_s in the reaction gamma+p = pK_sK_L. The
observed structure may be due to the interference between a strange (or
anti-strange) baryon resonance in the pK_L system and the phi(K_sK_L)
photoproduction leading to the same final state. The statistical significance
of the observed excess of events estimated as the log likelihood ratio of the
resonant signal+background hypothesis and the phi-production based background
only hypothesis corresponds to 5.3 sigma.Comment: Accepted for publication in Physical Review C, 9 pages, 11 figures, 1
table added, revise
A possible explanation why the Theta+ is seen in some experiments and not in others
To understand the whole set of positive and null data on the
Theta+(1530)-production, we suggest the hypothesis that multiquark hadrons are
mainly generated from many-quark states, which emerge either as short-term
hadron fluctuations, or as hadron remnants in hard processes. This approach
allows us to describe both non-observation of the Theta+ in current null
experiments and peculiar features of its production in positive experiments.
Further, we are able to propose new experiments that might be decisive for the
problem of the Theta+ existence. Distributions of the Theta+ in such
experiments can give important information both on higher Fock components of
conventional hadrons and about structure and hadronization properties of hadron
remnants produced in hard processes. We also explain that description of
multiquark hadrons may require a modified form of the constituent quark model,
with quark masses and couplings being intermediate between their values for the
familiar constituent quarks and the current ones.Comment: 18 pages. Some changes in the text; experimental suggestions
collected in a special subsection, references added and refreshe
Observation of narrow baryon resonance decaying into in pA-interactions at with SVD-2 setup
SVD-2 experiment data have been analyzed to search for an exotic baryon
state, the -baryon, in a decay mode at on IHEP
accelerator. The reaction with a limited multiplicity was
used in the analysis. The invariant mass spectrum shows a resonant
structure with and . The statistical significance of this peak was estimated to be of . The mass and width of the resonance is compatible with the recently
reported - baryon with positive strangeness which was predicted as an
exotic pentaquark () baryon state. The total cross section for
production in pN-interactions for was estimated to be
and no essential deviation from A-dependence for inelastic
events was found.Comment: 8 pages, 7 figures, To be submitted to Yadernaya Fizika. v3-v5 - Some
references added, minor typos correcte
Atmospheric Muon Flux at Sea Level, Underground, and Underwater
The vertical sea-level muon spectrum at energies above 1 GeV and the
underground/underwater muon intensities at depths up to 18 km w.e. are
calculated. The results are particularly collated with a great body of the
ground-level, underground, and underwater muon data. In the hadron-cascade
calculations, the growth with energy of inelastic cross sections and pion,
kaon, and nucleon generation in pion-nucleus collisions are taken into account.
For evaluating the prompt muon contribution to the muon flux, we apply two
phenomenological approaches to the charm production problem: the recombination
quark-parton model and the quark-gluon string model. To solve the muon
transport equation at large depths of homogeneous medium, a semi-analytical
method is used. The simple fitting formulas describing our numerical results
are given. Our analysis shows that, at depths up to 6-7 km w. e., essentially
all underground data on the muon intensity correlate with each other and with
predicted depth-intensity relation for conventional muons to within 10%.
However, the high-energy sea-level data as well as the data at large depths are
contradictory and cannot be quantitatively decribed by a single nuclear-cascade
model.Comment: 47 pages, REVTeX, 15 EPS figures included; recent experimental data
and references added, typos correcte
Quark-model study of few-baryon systems
We review the application of non-relativistic constituent quark models to
study one, two and three non-strange baryon systems. We present results for the
baryon spectra, potentials and observables of the NN, N,
and NN systems, and also for the binding energies of three
non-strange baryon systems. We make emphasis on observable effects related to
quark antisymmetry and its interplay with quark dynamics.Comment: 82 pages, 36 figures, 18 tables. Accepted for publication in Reports
on Progress in Physic
Search for a strongly decaying neutral charmed pentaquark
We present a search for a charmed pentaquark decaying strongly to
. Finding no evidence for such a state, we set limits on the cross
section times branching ratio relative to and under particular
assumptions about the production mechanism.Comment: To be published in Physics Letters
Morphological differentiation among migratory fish species from the Paraná River basin
How to Search for Doubly Charmed Baryons and Tetraquarks
Possible experimental searches of doubly charmed baryons and tetraquarks at
fixed target experiments with high energy hadron beams and a high intensity
spectrometer are considered here. The baryons considered are:
(ccd), (ccu), and (ccs); and the tetraquark
is T (). Estimates are given of masses, lifetimes, internal
structure, production cross sections, decay modes, branching ratios, and
yields. Experimental requirements are given for optimizing the signal and
minimizing the backgrounds. The discussion is in the spirit of an experimental
and theoretical review, as part of the planning for a CHarm Experiment with
Omni-Purpose Setup (CHEOPS) at CERN. The CHEOPS objective is to achieve a
state-of-the-art very charming experiment, in the spirit of the aims of the
recent CHARM2000 workshop.Comment: 18 pages text (latex), 16 March 1995, presented at "Physics with
Hadron Beams with a High Intensity Spectrometer", revised 10 May for more
complete bibliography and appropriate references to S. Paul et al., Letter of
Intent, CHEOPS
A-dependence of phi-meson production in p+A collisions
A systematic analysis of the A-dependence of phi-meson production in
proton-nucleus collisions is presented. We apply different formalisms for the
evaluation of the phi-meson distortion in nuclei and discuss the theoretical
uncertainties of the data analysis. The corresponding results are compared to
theoretical predictions. We also discuss the interpretation of the extracted
results with respect to different observables and provide relations between
frequently used definitions. The perspectives of future experiments are
evaluated and estimates based on our systematical study are given.Comment: 14 pages, 8 figure
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