217 research outputs found
Theoretical study of incoherent phi photoproduction on a deuteron target
We study the photoproduction of phi mesons in deuteron, paying attention to
the modification of the cross section from bound protons to the free ones with
the aim of comparing with recent results at LEPS. For this purpose we take into
account Fermi motion in single scattering and rescattering of the phi to
account for phi absorption on a second nucleon as well as the rescattering of
the proton. We find that the contribution of the double scattering is much
smaller than the typical cross section of gamma p to phi p in free space, which
implies a very small screening of the phi production in deuteron. The
contribution from the proton rescattering, on the other hand, is found to be
not negligible compared to the cross section of gamma p to phi p in free space,
and leads to a moderate reduction of the phi photoproduction cross section on a
deuteron at forward angles if LEPS set up is taken into account. The Fermi
motion allows contribution of the single scattering in regions forbidden by
phase space in the free case. In particular, we find that for momentum
transferred squared close to the maximum value, the Fermi motion changes
drastically the shape of d sigma / dt, to the point that the ratio of this
cross section to the free one becomes very sensitive to the precise value of t
chosen, or the size of the bin used in an experimental analysis. Hence, this
particular region of t does not seem the most indicated to find effects of a
possible phi absorption in the deuteron. This reaction is studied theoretically
as a function of t and the effect of the experimental angular cuts at LEPS is
also discussed, providing guidelines for future experimental analyses of the
reaction.Comment: 17 pages, 16 figure
Proton strangeness form factors in (4,1) clustering configurations
We reexamine a recent result within a nonrelativistic constituent quark model
(NRCQM) which maintains that the uuds\bar s component in the proton has its
uuds subsystem in P state, with its \bar s in S state (configuration I). When
the result are corrected, contrary to the previous result, we find that all the
empirical signs of the form factors data can be described by the lowest-lying
uuds\bar s configuration with \bar s in P state that has its uuds subsystem in
state (configuration II). Further, it is also found that the removal of the
center-of-mass (CM) motion of the clusters will enhance the contributions of
the transition current considerably. We also show that a reasonable description
of the existing form factors data can be obtained with a very small probability
P_{s\bar s}=0.025% for the uuds\bar s component. We further see that the
agreement of our prediction with the data for G_A^s at low-q^2 region can be
markedly improved by a small admixture of configuration I. It is also found
that by not removing CM motion, P_{s\bar s} would be overestimated by about a
factor of four in the case when transition dominates over direct currents.
Then, we also study the consequence of a recent estimate reached from analyzing
the existing data on quark distributions that P_{s\bar s} lies between 2.4-2.9%
which would lead to a large size for the five-quark (5q) system, as well as a
small bump in both G^s_E+\eta G^s_M and G^s_E in the region of q^2 =< 0.1
GeV^2.Comment: Prepared for The Fifth Asia-Pacific Conference on Few-Body Problems
in Physics 2011 in Seoul, South Korea, 22-26 August 201
Two-Boson Exchange Physics: A Brief Review
Current status of the two-boson exchange contributions to elastic
electron-proton scattering, both for parity conserving and parity-violating, is
briefly reviewed. How the discrepancy in the extraction of elastic nucleon form
factors between unpolarized Rosenbluth and polarization transfer experiments
can be understood, in large part, by the two-photon exchange corrections is
discussed. We also illustrate how the measurement of the ratio between
positron-proton and electron-proton scattering can be used to differentiate
different models of two-photon exchange. For the parity-violating
electron-proton scattering, the interest is on how the two-boson exchange
(TBE), \gamma Z-exchange in particular, could affect the extraction of the
long-sought strangeness form factors. Various calculations all indicate that
the magnitudes of effect of TBE on the extraction of strangeness form factors
is small, though can be large percentage-wise in certain kinematics.Comment: 6 pages, 5 figures, prepared for Proceedings of the fifth
Asia-Pacific Conference on Few-Body Problems in Physics (APFB2011), Seoul,
Korea, August 22-26, 2011, to appear in Few-Body Systems, November 201
Endpoint distribution of directed polymers in 1+1 dimensions
We give an explicit formula for the joint density of the max and argmax of
the Airy process minus a parabola. The argmax has a universal distribution
which governs the rescaled endpoint for large time or temperature of directed
polymers in 1+1 dimensions.Comment: Expanded introductio
Forecast accuracy of determining pseudo range in satellite navigation system through analysis of data from ionosphere monitoring
Annotation: The paper deals with the detection of wave arrival time errors in satellite navigation system by measurements conducted by stationary information system ionosphere monitoring. Develop a method of detecting the field increased ionization and the detection of the conditions for possible reduction of positioning accuracy in the presence of local ionospheric irregularities.The author examines in detail all mathematical aspects of the nature of the error; visual diagrams and graphs, as well as exhaustive mathematical calculations accompany the study. The article also discusses the process and results of computer modeling, an error that arises based on the data provided by the author, and allows one to verify the author's proposed method of detecting and predicting the occurrence of an error in determining the location. In the conclusion satity, the author speaks about the method of applying the developed method in the context of a specialized information system capable of preserving the positioning accuracy on the navigation radio signal.Keywords: radio navigation systems, pseudo range, monitoring, data analysi
MxTiSe2 (M = Cr, Mn, Cu) electronic structure study by methods of resonant X-ray photoemission spectroscopy and X-Ray absorption spectroscopy
Electronic structure and chemical bonding in TiX2 (X=S, Se, Te), TMxTiSe2
(TM=Cr, Mn, Cu) and CrxTi1-xSe2 were studied by x-ray resonance photoemission
and absorption spectroscopy. These methods are detected to be strong sensitive
to chemical bonding. Charge transfer from the intercalated atoms to Ti 3d band
is detected. Narrow Ti 3d and Cu 3d bands are observed under Fermi level in
CuxTiSe2.Comment: 7 pages, 4 figeres, ISIC 16 conferenc
Coherent phi and omega meson photoproduction from deuteron and non-diffractive channels
For coherent photoproduction of phi and omega mesons from deuteron at forward
angles, the isovector pi-exchange amplitude is strongly suppressed.
We show a possibility to study the non-diffractive channels associated with
the unnatural parity exchange in phi-photoproduction and with the baryon
resonance excitations in omega-photoproduction by measuring the spin
observables.Comment: 5 pages, 7 figure
Production of and Mesons in Near-Threshold Reactions: Baryon Resonances and Validity of the OZI Rule
Results of a combined analysis are presented for the production of
and mesons in reactions in the near-threshold region using
throughoutly a conventional ''non-strange'' dynamics based on such processes
which are allowed by the non-ideal mixing. We show that strong
interferences of the (meson exchange) and and (nucleon and nucleon
resonance) channels differ significantly in and production
amplitudes. This leads to a decrease of the relative yields in comparison with
expectations based on one-channel models with standard mixing.
We find a strong and non-trivial difference between observables in and
production reactions caused by the different role of the nucleon and
nucleon resonance amplitudes. A series of predictions for the experimental
study of this effect is presented.Comment: 22 pages with fig
Inclusive pentaquark and strange baryons production in pp and \Sigma p collisions at high energy
We calculate the cross sections for the inclusive production in the
fragmentation region of and in collisions
and in collisions at high energy using the - and
-meson exchange diagrams, respectively. The contributions of these
diagrams survive at asymptotically large energies and are energy independent in
this region up to logarithmic and power corrections. We find that inclusive
production should be at the level of 1
MeV. The ratio of the
over the yields is found to be . The
fraction of yields in and collisions is that quantitatively agrees with the preliminary result of the Fermilab
fixed target experiment E781.Comment: 5 pages, 5 figures, 1 table; RevTeX
Polarization observables in the reaction
We study the reaction slightly above the threshold within an
extended one-boson exchange model which also accounts for knock-out. It
is shown that polarization observables, like the beam-target asymmetry, are
sensible quantities for identifying a admixture in the nucleon wave
function on the few per cent level.Comment: 11 LaTeX pages including 4 ps figure
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