689,534 research outputs found

    New effective treatment of the light-front nonvalence contribution in timelike exclusive processes

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    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 K3K_{\ell3} and D0K+νlD^0\to K^- \ell^+ \nu_l 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

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    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

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    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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