11,911 research outputs found
Charm and Bottom Quark Production Cross Sections Near Threshold
The cross sections for charm and bottom quark production in the threshold
region are discussed. We consider the effects of an all order resummation of
initial state soft-plus-virtual gluon radiation on the total cross sections
compared to the order results.Comment: 16 pages LaTeX, 5 figures, to be published in Z. Phys.
Event-by-event study of prompt neutrons from 239Pu(n,f)
Employing a recently developed Monte Carlo model, we study the fission of
240Pu induced by neutrons with energies from thermal to just below the
threshold for second chance fission. Current measurements of the mean number of
prompt neutrons emitted in fission, together with less accurate measurements of
the neutron energy spectra, place remarkably fine constraints on predictions of
microscopic calculations. In particular, the total excitation energy of the
nascent fragments must be specified to within 1 MeV to avoid disagreement with
measurements of the mean neutron multiplicity. The combination of the Monte
Carlo fission model with a statistical likelihood analysis also presents a
powerful tool for the evaluation of fission neutron data. Of particular
importance is the fission spectrum, which plays a key role in determining
reactor criticality. We show that our approach can be used to develop an
estimate of the fission spectrum with uncertainties several times smaller than
current experimental uncertainties for outgoing neutron energies up to 2 MeV.Comment: 17 pages, 20 figure
Impingement of Cloud Droplets on 36.5-Percent-Thick Joukowski Airfoil at Zero Angle of Attack and Discussion of Use as Cloud Measuring Instrument in Dye-Tracer Technique
The trajectories of droplets i n the air flowing past a 36.5-percent-thick Joukowski airfoil at zero angle of attack were determined. The amount of water i n droplet form impinging on the airfoil, the area of droplet impingement, and the rate of droplet impingement per unit area on the airfoil surface were calculated from the trajectories and cover a large range of flight and atmospheric conditions. With the detailed impingement information available, the 36.5-percent-thick Joukowski airfoil can serve the dual purpose of use as the principal element in instruments for making measurements in clouds and of a basic shape for estimating impingement on a thick streamlined body. Methods and examples are presented for illustrating some limitations when the airfoil is used as the principal element in the dye-tracer technique
Impingement of Water Droplets on NACA 65A004 Airfoil at 8 deg Angle of Attack
The trajectories of droplets in the air flowing past an NACA 65AO04 airfoil at an angle of attack of 8 deg were determined.. The amount of water in droplet form impinging on the airfoil, the area of droplet impingement, and the rate of droplet impingement per unit area on the airfoil surface were calculated from the trajectories and presented to cover a large range of flight and atmospheric conditions. These impingement characteristics are compared briefly with those previously reported for the same airfoil at an angle of attack of 4 deg
Sea flavor content of octet baryons and intrinsic five-quark Fock states
Sea quark contents of the octet baryons are investigated by employing an
extended chiral constituent quark approach, which embodies higher Fock
five-quark components in the baryons wave-functions. The well-known flavor
asymmetry of the nucleon sea , is used as input to predict the
probabilities of , and in the nucleon, ,
and baryons, due to the intrinsic five-quark components in the
baryons wave functions.Comment: 22 page
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