689,534 research outputs found
New effective treatment of the light-front nonvalence contribution in timelike exclusive processes
We discuss a necessary nonvalence contribution in timelike exclusive
processes. Following a Schwinger-Dyson type of approach, we relate the
nonvalence contribution to an ordinary light-front wave function that has been
extensively tested in the spacelike exclusive processes. A complicate four-body
energy denominator is exactly cancelled in summing the light-front time-ordered
amplitudes. Applying our method to and
where a rather substantial nonvalence contribution is expected, we find not
only an improvement in comparing with the experimental data but also a
covariance(i.e. frame-independence) of existing light-front constituent quark
model.Comment: 10 pages including 5 figures; Changes: 1-added some sentences;
2-enlarged the figures; 3-added some reference
Towards the MSSM from F-theory
We study the MSSM in F-theory. Its group is the commutant to a structure
group SU(5) x U(1)_Y of a gauge bundle in E_8. The spectrum contains three
generations of quarks and leptons plus vectorlike electroweak and colored
Higgses. The minimal MSSM Yukawa couplings with matter parity is obtained at
the renormalizable level.Comment: 5 pages, 1 figure, published versio
Observations of B335 in the Millimeter Continuum and the 226 GHz H2CO Line
The protostar B335 was observed in the 1.3 mm continuum and in the H2CO 312 -
211 line with an angular resolution of about 8 arcsec. The mass of the inner
envelope detected by the dust continuum emission is about 0.02 Msun. The H2CO
spectrum at the protostellar position shows a blue-skewed double peak profile,
suggesting that the kinematics of the inner envelope is dominated by infall
motion. When the blueshifted and the redshifted peaks were imaged separately,
however, there is a small east-west displacement between the maximum positions.
This displacement suggests that some part of the H2CO emission might come from
the outflowing gas. A combined effect of the infalling envelope and the outflow
on the radiative transfer is discussed. This effect can make the line profile
asymmetry severer than what is expected from infall-only models
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