7,978 research outputs found
Two Body B Decays, Factorization and LambdaQCD/mb Corrections
By using the recent experimental measurements of B -> pi pi and B -> K pi
branching ratios, we find that the amplitudes computed at the leading order of
the LambdaQCD/mb expansion disagree with the observed BRs, even taking into
account the uncertainties of the input parameters. Beyond the leading order,
Charming and GIM penguins allow to reconcile the theoretical predictions with
the data. Because of these large effects, we conclude, however, that it is not
possible, with the present theoretical and experimental accuracy, to determine
the CP violation angle gamma from these decays. We compare our results with
those obtained with the parametrization of the chirally enhanced
non-perturbative contributions by BBNS. We also predict large asymmetries for
several of the particle--antiparticle BRs, in particular BR(B+ -> K+ pi0),
BR(Bd -> K+ pi-) and BR(Bd -> pi+ pi-).Comment: 14 pages 3 figures uses aippro
Charming Penguins Saga
We briefly recall the main formulae for computing the B -> K pi branching
ratios within the "charming penguin" approach, present an updated fit to the
data, and explain why we believe that, in general, these fits can hardly be
used to extract gamma.Comment: Invited talk at FPCP '02 given by M. Ciuchini, uses econfmacros.tex.
Final version with minor changes to appear in the proceeding
The tilt of the Fundamental Plane of Early-type galaxies: wavelength dependence
The photometric parameters R_e and mu_e of 74 early-type (E+S0+S0a) galaxies
in the Coma cluster are derived for the first time in the near IR H band. These
are used, coupled with measurements of the central velocity dispersion found in
the literature, to determine the H band Fundamental Plane (FP) relation of this
cluster. The same procedure is applied to previously available photometric data
in the B, V, r, I, and K bands, to perform a multi-wavelength study of the FP.
Because systematic uncertainties in the value of the FP parameters are
introduced both by the choice of the fitting algorithm, and by the presence of
statistical biases connected with the sample selection procedure, we emphasize
the importance of deriving the FP parameters in the six photometric bands using
an identical fitting algorithm, and appropriate corrections to eliminate the
effects of sample incompleteness. We find that the FP mu_e coefficient is
stable with wavelength, while the sigma coefficient increases significantly
with increasing wavelength, in agreement with an earlier result presented by
Pahre & Djorgovski. The slope of the FP relation, although changing with
wavelength, never approaches the virial theorem expectation. We also find that
the magnitude of the slope change can be entirely explained by the presence of
the well known relation between color and magnitude among early-type galaxies.
We conclude that the tilt of the Fundamental Plane is significant, and must be
due to some form of broken homology among early-type galaxies, while its
wavelength dependence derives from whatever mechanism (currently the preferred
one is the existence of a mass-metal content sequence) produces the
color-magnitude relation in those galaxies.Comment: 8 pages, 7 figures, 6 tables; table 3 should be printed in landscape
mode, and inserted into the text. Accepted for publication in MNRA
Penguin Contractions and Factorization in B -> K pi Decays
We study Lambda_{QCD}/m_B corrections to factorization in B -> K pi decays.
First, we analyze these decay channels within factorization, showing that,
irrespectively of the value of gamma, it is not possible to reproduce the
experimental data. Then, we discuss Lambda_{QCD}/m_B corrections to these
processes, and argue that there is a class of doubly Cabibbo enhanced
non-factorizable contributions, usually called charming penguins, that cannot
be neglected. Including these corrections, we obtain an excellent agreement
with experimental data. Furthermore, contrary to what is obtained with
factorization, we predict sizable rate asymmetries in B^\pm -> K^\pm \pi^0 and
B -> K^\pm pi^\mp.Comment: 4 pages, 3 figures. Talk given by L. Silvestrini at BCP4, Ise-Shima,
Japan, 18-23 Feb 200
Two-body nonleptonic B decays in the Standard Model and beyond
We briefly discuss the phenomenology of B to pi pi, B to K pi and B to phi K
decays in the Standard Model and in Supersymmetry.Comment: 7 pages, 2 figures, uses moriond.sty. Talk given by L. Silvestrini at
the XXXIXth Rencontres de Moriond on ElectroWeak Interactions and Unified
Theories, La Thuile, Aosta Valley, Italy, March 21st-28th 200
Physical Sources of Scatter in the Tully-Fisher Relation
We analyze residuals from the Tully-Fisher relation for the emission-line
galaxies in the Nearby Field Galaxy Survey, a broadly representative survey
designed to fairly sample the variety of galaxy morphologies and environments
in the local universe. For spirals brighter than M_R^i=-18, we find strong
correlations between Tully-Fisher residuals and both B-R color and EW(Halpha).
The extremes of the correlations are populated by Sa galaxies, which show
consistently red colors, and spirals with morphological peculiarities, which
are often blue. If we apply an EW(Halpha)-dependent or B-R color-dependent
correction term to the Tully-Fisher relation, the scatter in the relation no
longer increases from R to B to U but instead drops to a nearly constant level
close to the scatter we expect from measurement errors. We argue that these
results probably reflect correlated offsets in luminosity and color as a
function of star formation history. Broadening the sample in morphology and
luminosity, we find that most non-spirals brighter than M_R^i=-18 follow the
same correlations as do spirals, albeit with greater scatter. However, the
color and EW(Halpha) correlations do not apply to galaxies fainter than
M_R^i=-18 or to emission-line S0 galaxies with anomalous gas kinematics. For
the dwarf galaxy population, the parameters controlling Tully-Fisher residuals
are instead related to the degree of recent disturbance: overluminous dwarfs
have higher rotation curve asymmetries, brighter U-band effective surface
brightnesses, and shorter gas consumption timescales than their underluminous
counterparts. As a result, sample selection strongly affects the measured
faint-end slope of the Tully-Fisher relation. Passively evolving, rotationally
supported galaxies display a break toward steeper slope at low luminosities.Comment: 58 pages including 21 figures, AJ, accepte
Dust Attenuation in Late-Type Galaxies. I. Effects on Bulge and Disk Components
We present results of new Monte Carlo calculations made with the DIRTY code
of radiative transfer of stellar and scattered radiation for a dusty giant
late-type galaxy like the Milky Way, which illustrate the effect of the
attenuation of stellar light by internal dust on the integrated photometry of
the individual bulge and disk components. Here we focus on the behavior of the
attenuation function, the color excess, and the fraction of light scattered or
directly transmitted towards the outside observer as a function of the total
amount of dust and the inclination of the galaxy, and the structure of the
dusty interstellar medium (ISM) of the disk. We confirm that dust attenuation
produces qualitatively and quantitatively different effects on the integrated
photometry of bulge and disk, whatever the wavelength. In addition, we find
that the structure of the dusty ISM affects more sensitively the observed
magnitudes than the observed colors of both bulge and disk. Finally, we show
that the contribution of the scattered radiation to the total monochromatic
light received by the outside observer is significant, particularly at UV
wavelengths, even for a two-phase, clumpy, dusty ISM. Thus understanding dust
scattering properties is fundamental for the interpretation of extragalactic
observations in the rest-frame UV.Comment: 62 pages, 28 eps-figures, 1 table, accepted for publication in ApJ
Main Journa
Investigating The Physics Case of Running a B-Factory at the Y(5S) Resonance
We discuss the physics case of a high luminosity B-Factory running at the
Y(5S) resonance. We show that the coherence of the B meson pairs is preserved
at this resonance, and that Bs can be well distinguished from Bd and charged B
mesons. These facts allow to cover the physics program of a traditional
B-Factory and, at the same time, to perform complementary measurements which
are not accessible at the Y(4S). In particular we show how, despite the
experimental limitations in performing time-dependent measurements of Bs
decays, the same experimental information can be extracted, in several cases,
from the determination of time-integrated observables. In addition, a few
examples of the potentiality in measuring rare Bs decays are given. Finally, we
discuss how the study of Bs meson will improve the constraints on New Physics
parameters in the Bs sector, in the context of the generalized Unitarity
Triangle analysis.Comment: 47 pages, 22 figure
Resonance tuning and broadening of bowtie nanoantennas on graphene
Cataloged from PDF version of article.Metallic bowtie antennas are used in nanophotonics applications in order to confine the electromagnetic field into volumes much smaller than that of the incident wavelength. Electrically controllable carrier concentration of graphene opens the door to the use of plasmonic nanoantenna structures with graphene so that the resonant nature of nanoantennas can be tuned. In this study, we demonstrated with the Fourier transform infrared (FTIR) spectroscopy and the Finite Difference Time Domain (FDTD) method that the intensity and resonance peak of bowtie nanoantennas on monolayer graphene can be tuned at mid-infrared (MIR) wavelength regime by applying a gate voltage, since the optical properties of graphene change by changing the carrier concentration. (C) 2014 Elsevier B.V. All rights reserved
Multi-wavelength characterisation of z~2 clustered, dusty star forming galaxies discovered by Planck
(abridged) We report the discovery of PHz G95.5-61.6, a complex structure
detected in emission in the Planck all-sky survey that corresponds to two
over-densities of high-redshift galaxies. This is the first source from the
Planck catalogue of high-z candidates that has been completely characterised
with follow-up observations from the optical to the sub-millimetre domain.
Herschel/SPIRE observations at 250, 350 and 500 microns reveal the existence of
five sources producing a 500 microns emission excess that spatially corresponds
to the candidate proto-clusters discovered by Planck. Further observations at
CFHT in the optical bands (g and i) and in the near infrared (J, H and K_s),
plus mid infrared observations with IRAC/Spitzer (at 3.6 and 4.5 microns)
confirm that the sub-mm red excess is associated with an over-density of
colour-selected galaxies. Follow-up spectroscopy of 13 galaxies with
VLT/X-Shooter establishes the existence of two high-z structures: one at z~1.7
(three confirmed member galaxies), the other at z~2.0 (six confirmed members).
This double structure is also seen in the photometric redshift analysis of a
sample of 127 galaxies located inside a circular region of 1'-radius containing
the five Herschel/SPIRE sources, where we found a double-peaked excess of
galaxies at z~1.7 and z~2.0 with respect to the surrounding region. These
results suggest that PHz G95.5-61.6 corresponds to two accreting nodes, not
physically linked to one another, embedded in the large scale structure of the
Universe at z~2 and along the same line-of-sight. In conclusion, the data,
methods and results illustrated in this pilot project confirm that Planck data
can be used to detect the emission from clustered, dusty star forming galaxies
at high-z, and, thus, to pierce through the early growth of cluster-scale
structures.Comment: 15 pages, 13 figures. Accepted for publication in Astronomy and
Astrophysic
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