2,909 research outputs found
The Semileptonic Decay Fraction of B Mesons in the Light of Interfering Amplitudes
Consequences of the interference between spectator amplitudes for the
lifetimes and semileptonic decay fractions of B^0 and B^+ mesons are discussed.
Assuming duality and constructive interference between spectator amplitudes we
are able to explain the low experimental value for the semileptonic decay
fraction of mesons. Extracting these amplitudes from a fit to 11 exclusive
hadronic B decay fractions we find
a_1 = 1.05 +/- 0.03 +/- 0.10,
a_2 =+0.227 +/ 0.012 +/- 0.022,
an inclusive semileptonic decay fraction of
(11.2 +/- 0.5 +/- 1.7),
and a lifetime ratio
tau(B^+) / tau(B^0) = 0.83 +/- 0.01 +/- 0.01.Comment: 9 page
Penguin decays of B mesons
Penguin, or loop, decays of B mesons induce effective flavor-changing neutral
currents, which are forbidden at tree level in the Standard Model. These decays
give special insight into the CKM matrix and are sensitive to non-standard
model effects. In this review, we give a historical and theoretical
introduction to penguins and a description of the various types of penguin
processes: electromagnetic, electroweak, and gluonic. We review the
experimental searches for penguin decays, including the measurements of the
electromagnetic penguins b -> s gamma and B -> K* gamma and gluonic penguins B
-> K pi, B+ -> omega K+ and B -> eta' K, and their implications for the
Standard Model and New Physics. We conclude by exploring the future prospects
for penguin physics.Comment: 49 pages, LATEX, 30 embedded figures, submitted to Annual Reviews of
Nuclear and Particle Scienc
Exploiting Cross Correlations and Joint Analyses
In this report, we present a wide variety of ways in which information from
multiple probes of dark energy may be combined to obtain additional information
not accessible when they are considered separately. Fundamentally, because all
major probes are affected by the underlying distribution of matter in the
regions studied, there exist covariances between them that can provide
information on cosmology. Combining multiple probes allows for more accurate
(less contaminated by systematics) and more precise (since there is
cosmological information encoded in cross-correlation statistics) measurements
of dark energy. The potential of cross-correlation methods is only beginning to
be realized. By bringing in information from other wavelengths, the
capabilities of the existing probes of dark energy can be enhanced and
systematic effects can be mitigated further. We present a mixture of work in
progress and suggestions for future scientific efforts. Given the scope of
future dark energy experiments, the greatest gains may only be realized with
more coordination and cooperation between multiple project teams; we recommend
that this interchange should begin sooner, rather than later, to maximize
scientific gains.Comment: Report from the "Dark Energy and CMB" working group for the American
Physical Society's Division of Particles and Fields long-term planning
exercise ("Snowmass"
Planning the Future of U.S. Particle Physics (Snowmass 2013): Chapter 4: Cosmic Frontier
These reports present the results of the 2013 Community Summer Study of the
APS Division of Particles and Fields ("Snowmass 2013") on the future program of
particle physics in the U.S. Chapter 4, on the Cosmic Frontier, discusses the
program of research relevant to cosmology and the early universe. This area
includes the study of dark matter and the search for its particle nature, the
study of dark energy and inflation, and cosmic probes of fundamental
symmetries.Comment: 61 page
The Cherenkov Correlated Timing Detector: Beam Test Results from Quartz and Acrylic Bars
Several prototypes of a Cherenkov Correlated Timing (CCT) Detector have been
tested at the KEK-PS test beam line. We describe the results for Cherenkov
light yields and timing characteristics from quartz and acrylic bar prototypes.
A Cherenkov angle resolution is found to be 15 mrad at a propagation distance
of 100 cm with a 2 cm thick quartz bar prototype.Comment: Presented at the RICH95 workshop, Uppsala, Sweden, June/95. H.
Kichimi corresponding author. 5 pages with 9 figures. LaTex source files and
postscript figures compressed and uuencoded belo
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