2,052 research outputs found
Baryonium, a common ground for atomic and high energy physics
Indications of the existence of quasi-bound states in the N-Nbar system are
presented. Measurements by BES discovered a broad enhancement close to the
p-pbar threshold in the S wave, isospin 0 state formed in radiative decays of
J/psi. Another enhancement located about 50 MeV below the threshold was found
in mesonic decays of J/psi. In terms of the Paris potential model it was shown
that these are likely to represent the same state. Antiprotonic atomic data
provide some support for this interpretation and indicate the existence of
another fairly narrow quasi-bound state in a P wave.Comment: 6 pages, 6 figures - Contribution to EXA2014 Vienna to appear in a
special edition of Hyperfine Interaction
K* resonance effects on direct CP violation in B -> pi pi K
Charged and neutral B decays into two charged pions and a charged or a
neutral kaon are analyzed within the QCD factorization scheme where final state
interactions before and after hadronization are included. The K*(892) and
K*(1430) resonance effects are taken into account using the presently known
pion-Kaon strange vector and scalar form factors. The weak decay amplitudes,
which are calculated at leading power in Lambda_QCD/m_b and at the
next-to-leading order in the strong coupling constant, include the hard
scattering and annihilation contributions. The end point divergences of these
weak final state interactions are controlled by two complex parameters
determined through a fit to the available effective mass and helicity angle
distribution, CP asymmetry and K*(892) branching ratio data. The predicted
K*(1430) branching ratios and the calculated direct CP violation asymmetries
are compared to the Belle and BABAR Collaboration data.Comment: Comments: 22 pages, 2 figures and 3 tables. In this new version, the
results are unchanged, but, the last paragraph of the Section "RESULTS AND
SUMMARY" (now called "RESULTS AND DISCUSSION") has been replaced by a new
Section "SUMMARY AND OUTLOOK". To appear in Physical Review
On the structure of the X(1835) baryonium
The measurement by the BES collaboration of J/psi -> gamma p pbar decays
indicates an enhancement at the p-pbar threshold. In another experiment BES
finds a peak in the invariant mass of pi-mesons produced in the possibly
related decay J/psi -> gamma pi+ pi- eta'. Using a semi-phenomenological
potential model which describes all the N-Nbar scattering data, we show that
the explanation of both effects may be given by a broad quasi-bound state in
the spin and isospin singlet S wave. The structure of the observed peak is due
to an interference of this quasi-bound state with a background amplitude and
depends on the annihilation mechanism.Comment: 7 pages, 7 figures, this version corresponds to the published paper
in Phys. Rev. C: minor corrections done and in section 5 suggestions of
experiments to confirm the link of the X(1835) to the antiproton-proton
syste
Equality of Voice: Towards Fair Representation in Crowdsourced Top-K Recommendations
To help their users to discover important items at a particular time, major
websites like Twitter, Yelp, TripAdvisor or NYTimes provide Top-K
recommendations (e.g., 10 Trending Topics, Top 5 Hotels in Paris or 10 Most
Viewed News Stories), which rely on crowdsourced popularity signals to select
the items. However, different sections of a crowd may have different
preferences, and there is a large silent majority who do not explicitly express
their opinion. Also, the crowd often consists of actors like bots, spammers, or
people running orchestrated campaigns. Recommendation algorithms today largely
do not consider such nuances, hence are vulnerable to strategic manipulation by
small but hyper-active user groups.
To fairly aggregate the preferences of all users while recommending top-K
items, we borrow ideas from prior research on social choice theory, and
identify a voting mechanism called Single Transferable Vote (STV) as having
many of the fairness properties we desire in top-K item (s)elections. We
develop an innovative mechanism to attribute preferences of silent majority
which also make STV completely operational. We show the generalizability of our
approach by implementing it on two different real-world datasets. Through
extensive experimentation and comparison with state-of-the-art techniques, we
show that our proposed approach provides maximum user satisfaction, and cuts
down drastically on items disliked by most but hyper-actively promoted by a few
users.Comment: In the proceedings of the Conference on Fairness, Accountability, and
Transparency (FAT* '19). Please cite the conference versio
Combined Quantitative X-ray Diffraction, Scanning Electron Microscopy, and Transmission Electron Microscopy Investigations of Crystal Evolution in CaOâAl2O3âSiO2âTiO2âZrO2âNd2O3âNa2O System
Glass-ceramics, with a specific crystalline phase assembly, can combine the advantages of glass and ceramic and avoid their disadvantages. In this study, both cubic-zirconia and zirconolite-based glass-ceramics were obtained by the crystallization of SiO2-CaO-Al2O3-TiO2-ZrO2-Nd2O3-Na2O glass. Results show that all samples underwent a phase transformation from cubic-zirconia to zirconolite when crystallized at 900, 950, and 1000 °C. The size of the cubic-zirconia crystal could be controlled by temperature and dwelling time. Both cubic-zirconia and zirconolite crystals/particles show dendrite shapes, but with different dendrite branching. The dendrite cubic-zirconia showed highly oriented growth. Scanning electron microscopy images show that the branches of the cubic-zirconia crystal had a snowflake-like appearance, while those in zirconolite were composed of many individual crystals. Rietveld quantitative analysis revealed that the maximum amount of zirconolite was âŒ19 wt %. A two-stage crystallization method was used to obtain different microstructures of zirconolite-based glass-ceramic. The amount of zirconolite remained approximately 19 wt %, but the individual crystals were smaller and more homogeneously dispersed in the dendrite structure than those obtained from one-stage crystallization. This process-control feature can result in different sizes and morphologies of cubic-zirconia and zirconolite crystals to facilitate the design of glass-ceramic waste forms for nuclear wastes
Pseudoscalar-scalar transition form factors in covariant light front dynamics
In an explicitly covariant light-front formalism, we analyze transition form
factors between pseudoscalar and scalar mesons. Application is performed in
case of the transition in the full available transfer momentum
range .Comment: 4 pages, 4 figures. Talk given at the XXXIII International Conference
on High Energy Physics, ICHEP06, Moscow, 26 July-02 Augus
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