7,404 research outputs found
Nucleon and Delta resonances in K Sigma(1385) photoproduction from nucleons
The reaction mechanisms for photoproduction from the reaction
in the resonance energy region are
investigated in a hadronic model. Both contributions from and
resonances of masses around 2 GeV as given in the Review of Particle Data Group
and by the quark model predictions are included. The Lagrangians for describing
the decays of these resonances into are constructed with the
coupling constants determined from the decay amplitudes predicted by a quark
model. Comparing the resulting total cross section for the reaction with the preliminary data from the Thomas Jefferson
National Accelerator Facility, we find that the most important contributions
are from the two-star rated resonances , , and , as well as the missing resonance
predicted in the quark model. Predictions on the
differential cross section and photon asymmetry in this reaction are also
given.Comment: 13 pages, 6 figures, REVTeX, to appear in Phys. Rev.
Swift Observations of the Be/X-ray Transient System 1A 1118-615
We report results of Swift observations for the high mass Be/X-ray binary
system 1A 1118-615, during an outburst stage in January, 2009 and at a flaring
stage in March, 2009. Using the epoch-folding method, we successfully detected
a pulsed period of 407.69(2) sec in the outburst of January and of 407.26(1)
sec after the flare detection in March. We find that the spectral detection for
the source during outburst can be described by a blackbody model with a high
temperature (kT ~ 1-3 keV) and a small radius (R ~ 1 km), indicating that the
emission results from the polar cap of the neutron star. On the other hand, the
spectra obtained after the outburst can further be described by adding an
additional component with a lower temperature (kT ~ 0.1-0.2 keV) and a larger
emission radius (R ~ 10-500 km), which indicates the emission from around the
inner region of an accretion disk. We find that the thermal emission from the
hot spot of the accreting neutron star dominates the radiation in outburst; the
existence of both this X-ray contribution and the additional soft component
suggest that the polar cap and the accretion disk emission might co-exist after
the outburst. Because the two-blackbody signature at the flaring stage is a
unique feature of 1A 1118-615, our spectral results may provide a new insight
to interpret the X-ray emission for the accreting neutron star. The time
separation between the three main outbursts of this system is ~17 years and it
might be related to the orbital period. We derive and discuss the associated
physical properties by assuming the elongated orbit for this specific Be/X-ray
transient.Comment: 9 pages, 3 figures and 4 tables; accepted by MNRA
Keeping the Listener Engaged: a Dynamic Model of Bayesian Persuasion
We consider a dynamic model of Bayesian persuasion in which information takes time and is costly for the sender to generate and for the receiver to process, and neither player can commit to their future actions. Persuasion may totally collapse in a Markov perfect equilibrium (MPE) of this game. However, for persuasion costs sufficiently small, a version of a folk theorem holds: outcomes that approximate Kamenica and Gentzkow (2011)'s sender-optimal persuasion as well as full revelation and everything in between are obtained in MPE, as the cost vanishes
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