504 research outputs found
Indications for Factorization and from Rare B Decay Data
Surveying known hadronic rare B decays, we find that the factorization
approximation can give a coherent account of , and
data and give predictions for , and modes,
{\it if is taken as negative} (in standard phase convention)
rather than positive. As further confirmation, we expect a lower
value at B Factories as compared to current fits, and mixing close to LEP
bounds at SLD and CDF.Comment: 11 pages, revtex, 4 figures (unchanged and eps files included);
version (including title and abstract change) to appear in Phys. Rev. Let
Upscaling of perovskite solar modules: The synergy of fully evaporated layer fabrication and all‐laser‐scribed interconnections
Given the outstanding progress in research over the past decade, perovskite photovoltaics (PV) is about to step up from laboratory prototypes to commercial products. For this to happen, realizing scalable processes to allow the technology to transition from solar cells to modules is pivotal. This work presents all-evaporated perovskite PV modules with all thin films coated by established vacuum deposition processes. A common 532-nm nanosecond laser source is employed to realize all three interconnection lines of the solar modules. The resulting module interconnections exhibit low series resistance and a small total lateral extension down to 160 μm. In comparison with interconnection fabrication approaches utilizing multiple scribing tools, the process complexity is reduced while the obtained geometrical fill factor of 96% is comparable with established inorganic thin-film PV technologies. The all-evaporated perovskite minimodules demonstrate power conversion efficiencies of 18.0% and 16.6% on aperture areas of 4 and 51 cm, respectively. Most importantly, the all-evaporated minimodules exhibit only minimal upscaling losses as low as 3.1% per decade of upscaled area, at the same time being the most efficient perovskite PV minimodules based on an all-evaporated layer stack sequence
Phenomenological Study of Strong Decays of Heavy Hadrons in Heavy Quark Effective Theory
The application of the tensor formalism of the heavy quark effective theory
(HQET) at leading order to strong decays of heavy hadrons is presented.
Comparisons between experimental and theoretical predictions of ratios of decay
rates for B mesons, D mesons and kaons are given. The application of HQET to
strange mesons presents some encouraging results. The spin-flavor symmetry is
used to predict some decay rates that have not yet been measured.Comment: 10 page
CP-Violating Asymmetries in Charmless Non-Leptonic Decays in the Factorization Approach
We present estimates of the direct (in decay amplitudes) and indirect
(mixing- induced) CP-violating asymmetries in the non-leptonic charmless
two-body decay rates for , and decays and their
charged conjugates, where P(V) is a light pseudoscalar (vector) meson. These
estimates are based on a generalized factorization approach making use of
next-to-leading order perturbative QCD contributions which generate the
required strong phases. No soft final state interactions are included. We study
the dependence of the asymmetries on a number of input parameters and show that
there are at least two (possibly three) classes of decays in which the
asymmetries are parametrically stable in this approach. The decay modes of
particular interest are: \optbar{B^0} \to \pi^+ \pi^-, \optbar{B^0} \to
K_S^0 \pi^0, \optbar{B^0} \to K_S^0 \eta^\prime, \optbar{B^0} \to K_S^0
\eta and \optbar{B^0} \to \rho^+ \rho^-. Likewise, the CP-violating
asymmetry in the decays \optbar{B^0} \to K_S^0 h^0 with is found to be parametrically stable and large. Measurements
of these asymmetries will lead to a determination of the phases
and and we work out the relationships in these modes in the
present theoretical framework. We also show the extent of the so-called
"penguin pollution" in the rate asymmetry and of the
"tree shadow" in the asymmetry which will effect the
determination of and from the respective
measurements. CP-violating asymmetries in ,
, and are potentially interesting and are studied here.Comment: 42 pages (LaTex) including 19 figures, requires epsfig.sty; submitted
to Phys. Rev.
Forward Neutron Production at the Fermilab Main Injector
We have measured cross sections for forward neutron production from a variety
of targets using proton beams from the Fermilab Main Injector. Measurements
were performed for proton beam momenta of 58 GeV/c, 84 GeV/c, and 120 GeV/c.
The cross section dependence on the atomic weight (A) of the targets was found
to vary as where is for a beam momentum of
58 GeV/c and 0.540.05 for 120 GeV/c. The cross sections show reasonable
agreement with FLUKA and DPMJET Monte Carlos. Comparisons have also been made
with the LAQGSM Monte Carlo.Comment: Accepted for publication in Physical Review D. This version
incorporates small changes suggested by referee and small corrections in the
neutron production cross sections predicted by FLUK
Observation of the Dynamic Beta Effect at CESR with CLEO
Using the silicon strip detector of the CLEO experiment operating at the
Cornell Electron-positron Storage Ring (CESR), we have observed that the
horizontal size of the luminous region decreases in the presence of the
beam-beam interaction from what is expected without the beam-beam interaction.
The dependence on the bunch current agrees with the prediction of the dynamic
beta effect. This is the first direct observation of the effect.Comment: 9 page uuencoded postscript file, postscritp file also available
through http://w4.lns.cornell.edu/public/CLNS, submitted to Phys. Rev.
Measurement of Charged Pion Production Yields off the NuMI Target
The fixed-target MIPP experiment, Fermilab E907, was designed to measure the
production of hadrons from the collisions of hadrons of momenta ranging from 5
to 120 GeV/c on a variety of nuclei. These data will generally improve the
simulation of particle detectors and predictions of particle beam fluxes at
accelerators. The spectrometer momentum resolution is between 3 and 4%, and
particle identification is performed for particles ranging between 0.3 and 80
GeV/c using , time-of-flight and Cherenkov radiation measurements. MIPP
collected events of 120 GeV Main Injector protons striking a
target used in the NuMI facility at Fermilab. The data have been analyzed and
we present here charged pion yields per proton-on-target determined in bins of
longitudinal and transverse momentum between 0.5 and 80 GeV/c, with combined
statistical and systematic relative uncertainties between 5 and 10%.Comment: 15 pages, 13 figure
Analysis of Neutral Higgs-Boson Contributions to the Decays B_s -> l^+l^- and B -> K l^+l^-
We report on a calculation of Higgs-boson contributions to the decays B_s ->
l^+l^- and B -> K l^+l^- (l=e, mu) which are governed by the effective
Hamiltonian describing b -> s l^+ l^-. Compact formulae for the Wilson
coefficients are provided in the context of the type-II two-Higgs-doublet model
(2HDM) and supersymmetry (SUSY) with minimal flavour violation, focusing on the
case of large tan(beta). We derive, in a model-independent way, constraints on
Higgs-boson-mediated interactions, using present experimental results on rare B
decays including b -> s gamma, B_s -> mu^+ mu^-, and B -> K^(*) mu^+ mu^-. In
particular, we assess the impact of possible scalar and pseudoscalar
interactions transcending the standard model (SM) on the branching ratio of B_s
-> mu^+ mu^- and the forward-backward (FB) asymmetry of mu^- in B -> K mu^+
mu^- decay. We find that the average FB asymmetry, which is unobservably small
within the SM, and therefore a potentially valuable tool to search for new
physics, is predicted to be no greater than 4% for a nominal branching ratio of
about 6x10^{-7}. Moreover, striking effects on the decay spectrum of B -> K
mu^+ mu^- are already ruled out by experimental data on the B_s -> mu^+ mu^-
branching fraction. In addition, we study the constraints on the parameter
space of the 2HDM and SUSY with minimal flavour violation. While the type-II
2HDM does not give any sizable contributions to the above decay modes, we find
that SUSY contributions obeying the constraint on b -> s gamma can affect
significantly the branching ratio of B_s -> mu^+ mu^-. We also comment on
previous calculations contained in the literature.Comment: 29 pages, REVTeX, 8 figures. Minor corrections in Eqs. (5.4), (5.11)
and (6.3) of the published versio
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