29,153 research outputs found
The exclusive Drell-Yan process and deeply virtual pion production
In this talk it is reported on analyses of l p -> l pi+ n and pi- p -> l+ l-
n within the handbag approach. It is argued that recent measurements of hard
pion production performed by HERMES and CLAS clearly indicate the occurrence of
strong contributions from transversely polarized photons. The gamma*T -> pi
transitions are described by the transversity GPDs accompanied by twist-3 pion
wave functions. The experiments also require strong contributions from the pion
pole which can be modeled as a classical one-pion exchange. With these
extensions the handbag approach leads to results on cross sections and spin
asymmetries in fair agreement with experiment. This approach is also used for
an estimate of the partial cross sections for the exclusive Drell-Yan process.Comment: 8 pages, 6 figures, latex with style files jpsj-suppl.cls and
cite.sty invited talk presented at MENU2016, Kyoto (Japan), July 2016. arXiv
admin note: substantial text overlap with arXiv:1602.0380
J/ production and suppression in nuclear collisions
In terms of a new QCD factorization formula for J/ production, we
calculate the J/ suppression in nuclear collisions by including the
multiple scattering between the pre-J/ partonic states and the nuclear
medium. We find agreement with all data on J/ suppression in
hadron-nucleus and nucleus-nucleus collisions, except a couple of points (the
``second drop'') at the highest bins of the new NA50 data.Comment: Latex, 4 pages, to appear in the proceedings of Quark Matter 200
Self-shadowing Effects of Slim Accretion Disks in Active Galactic Nuclei: Diverse Appearance of the Broad-line Region
Supermassive black holes in active galactic nuclei (AGNs) undergo a wide
range of accretion rates, which lead to diversity of appearance. We consider
the effects of anisotropic radiation from accretion disks on the broad-line
region (BLR), from the Shakura-Sunyaev regime to slim disks with
super-Eddington accretion rates. The geometrically thick funnel of the inner
region of slim disks produces strong self-shadowing effects that lead to very
strong anisotropy of the radiation field. We demonstrate that the degree of
anisotropy of the radiation fields grows with increasing accretion rate. As a
result of this anisotropy, BLR clouds receive different spectral energy
distributions depending on their location relative to the disk, resulting in
diverse observational appearance of the BLR. We show that the self-shadowing of
the inner parts of the disk naturally produces two dynamically distinct regions
of the BLR, depending on accretion rate. These two regions manifest themselves
as kinematically distinct components of the broad H line profile with
different line widths and fluxes, which jointly account for the Lorentzian
profile generally observed in narrow-line Seyfert 1 galaxies. In the time
domain, these two components are expected reverberate with different time lags
with respect to the varying ionizing continuum, depending on the accretion rate
and the viewing angle of the observer. The diverse appearance of the BLR due to
the anisotropic ionizing energy source can be tested by reverberation mapping
of H and other broad emission lines (e.g., \feii), providing a new tool
to diagnose the structure and dynamics of the BLR. Other observational
consequences of our model are also explored.Comment: emulatapj style, 15 pages, 6 figures, in pres
Modular Equations and Distortion Functions
Modular equations occur in number theory, but it is less known that such
equations also occur in the study of deformation properties of quasiconformal
mappings. The authors study two important plane quasiconformal distortion
functions, obtaining monotonicity and convexity properties, and finding sharp
bounds for them. Applications are provided that relate to the quasiconformal
Schwarz Lemma and to Schottky's Theorem. These results also yield new bounds
for singular values of complete elliptic integrals.Comment: 23 page
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