46,628 research outputs found
Modelling the number counts of early-type galaxies by pure luminosity evolution
In this paper, we explore the plausible luminosity evolution of early-type
galaxies in different cosmological models by constructing a set of pure
luminosity evolution (PLE) models via the choices of the star formation rate
(SFR) parameters and formation redshift of galaxies, with the
observational constraints derived from the Hubble Space Telescope (HST)
morphological number counts for elliptical and S0 galaxies of the Medium Deep
Survey (MDS) and the Hubble Deep Field (HDF). We find that the number counts of
early-type galaxies can be explained by the pure luminosity evolution models,
without invoking exotic scenarios such as merging or introducing an additional
population. But the evolution should be nearly passive, with a high
assumed. The conclusion is valid in all of the three cosmological models we
adopted in this paper. We also present the redshift distributions for three
bins of observed magnitudes in F814w pass-band, to show at which redshift are
the objects that dominate the counts at a given magnitude. The predictions of
the redshift distribution of are also presented for comparison
with future data.Comment: Plain tex, 15pages, 9 eps figures, plus an extra figure fig2c.eps,
with the tex-macro mn.tex. MNRAS, accepte
Glueball Production via Gluonic Penguin B Decays
We study glueball production in gluonic penguin decay ,
using the next-to-leading order gluonic penguin interaction and
effective couplings of a glueball to two perturbative gluons. Subsequent decays
of a scalar glueball are described by using techniques of effective chiral
Lagrangian to incorporate the interaction between a glueball and pseudoscalar
mesons. Mixing effects between the pure glueball with other mesons are
considered. Identifying the to be a scalar glueball, we find that
both the top and charm penguin to be important and obtain a sizable branching
ratio for of order 1.3\times 10^{-4}
(f/0.07\mbox{GeV}^{-1})^2, where the effective coupling strength is
estimated to be GeV using experimental data for the branching
ratio of based on chiral Lagrangian estimate. An
alternative perturbative QCD based estimation of is a factor of 20 larger,
which would imply a much enhanced branching ratio. Glueball production from
this rare semi-inclusive decay can be probed at the LHCb and Belle II to
narrow down the allowed parameter space. Similar branching ratio is expected
for the pseudoscalar glueball. We also briefly comment on the case of vector
and tensor glueballs.Comment: Latex 14 pages with 2 figures. Significant update from the older
version of arXiv:hep-ph/0612108. Version to appear in Eur. Phys. J.
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