2,370 research outputs found
Fragmentation functions of polarized heavy quarkonium
Study of the polarized heavy quarkonium production in recently proposed QCD
factorization formalism requires knowledge of a large number of input
fragmentation functions (FFs) from a single parton or a heavy quark-antiquark
pair to a polarized heavy quarkonium. In this paper, we calculate these FFs at
the input scale in terms of nonrelativistic QCD (NRQCD) factorization. We
derive all relevant polarized NRQCD long-distance matrix elements based
symmetries and propose a self-consistent scheme to define them in arbitrary
dimensions. We then calculate polarized input FFs contributed from all -wave
and -wave NRQCD intermediate states. With our calculation of the polarized
input FFs, and the partonic hard part available in literatures, the QCD
factorization formalism is ready to be applied to polarized heavy quarkonium
production.Comment: 30 pages, 1 figur
Utilizing the Updated Gamma-Ray Bursts and Type Ia Supernovae to Constrain the Cardassian Expansion Model and Dark Energy
We update gamma-ray burst (GRB) luminosity relations among certain spectral
and light-curve features with 139 GRBs. The distance modulus of 82 GRBs at
can be calibrated with the sample at by using the cubic
spline interpolation method from the Union2.1 Type Ia supernovae (SNe Ia) set.
We investigate the joint constraints on the Cardassian expansion model and dark
energy with 580 Union2.1 SNe Ia sample () and 82 calibrated GRBs data
(). In CDM, we find that adding 82 high-\emph{z} GRBs to
580 SNe Ia significantly improves the constrain on
plane. In the Cardassian expansion model, the
best fit is and
, which is consistent with the CDM cosmology in the
confidence region. We also discuss two dark energy models in which
the equation of state is parametrized as and
, respectively. Based on our analysis, we see that our
Universe at higher redshift up to is consistent with the concordance
model within confidence level.Comment: 17 pages, 6 figures, 2 tables; accepted for publication in Advances
in Astronomy, special issue on Gamma-Ray Burst in Swift and Fermi Era. arXiv
admin note: text overlap with arXiv:0802.4262, arXiv:0706.0938 by other
author
- β¦