273 research outputs found
Can FCNC transition be seen in decays?
The decays present in principle the opportunity to observe the
short distance FCNC transition , which is sensitive to the
physics beyond the Standard Model. We analyze the decays
within the Standard Model, where in addition to the short distance dynamics
also the long distance dynamics is present. The short distance contribution due
to transition, which is present only in the Cabibbo suppressed
decays, is found to be three orders of magnitude smaller than the long distance
contribution. The branching ratios well above for Cabibbo suppressed
decays could signal new physics. The most frequent decays are the Cabibbo
allowed decays and ,
which are expected at the branching ratios of and , respectively. These rates are not much lower than the present
experimental upper limit.Comment: 3 pages, latex, 3 figures, Talk given by S. Prelovsek at the
Hyperons, Charm and Beauty Hadrons, Genova, Italy, 30 June -3 July 1998, to
appear as proceedings in Nucl. Phys.
LHC data and cosmic ray coplanarity at superhigh energies
A new phenomenological model FANSY 2.0 is designed, which makes it possible
to simulate hadron interactions via traditional QGSM-type particle generation
as well as coplanar generation of most energetic particles, observed in cosmic
ray experiments. FANSY 2.0 reproduces a lot of LHC (ALICE, ATLAS, CMS, TOTEM,
LHCf) data. Results of model simulations are compared with LHC data. Problems
of coplanarity are considered and a testing experiment is proposed.Comment: 8 pages, 21 PostScript figures, will be published in EPJ WoC (Proc.
ISVHECRI 2016
Lateral Distribution for Aligned Events in Muon Groups Deep Underground
The paper concerns the so-called aligned events observed in cosmic rays. The
phenomenon of the alignment of the most energetic subcores of gamma-ray--hadron
() families (particles of the highest energies in the central EAS
core) was firstly found in the "Pamir" emulsion chamber experiment and related
to a coplanar particle production at eV. Here a separation
distribution (distances between pairs of muons) for aligned events has been
analyzed throughout muon groups measured by Baksan Underground Scintillation
Telescope (BUST) for threshold energies TeV during a period of
7.7 years. Only muon groups of multiplicity with inclined
trajectories for an interval of zenith angles were
selected for the analysis. The analysis has revealed that the distribution
complies with the exponential law. Meanwhile the distributions become steeper
with the increase of threshold energy. There has been no difference between the
lateral distribution of all the groups and the distribution of the aligned
groups.Comment: 4 pages, 3 figures. Prepared for the ISVHECRI'2006, Weihai, Chin
59Co NMR evidence for charge and orbital order in the kagome like structure of Na2/3CoO2
We report a complete set of Co NMR data taken on the phase of
sodium cobaltates NaCoO, for which we have formerly established the
in plane Na ordering and its three dimensional stacking from a combination of
symmetry arguments taken from Na and Co NQR/NMR data. Here we resolve all the
parameters of the Zeeman and quadrupolar Hamiltonians for all cobalt sites in
the unit cell and report the temperature dependencies of the NMR shift and spin
lattice relaxation data for these sites. We confirm that three
non-magnetic Co (Co1) are in axially symmetric positions and that the
doped holes are delocalized on the nine complementary magnetic cobalt sites
(Co2) of the atomic unit cell. The moderately complicated atomic structure
resumes then in a very simple electronic structure in which the electrons
delocalize on the Co2 kagom\'e sublattice of the triangular lattice of Co
sites. The observation of a single temperature dependence of the spin
susceptibilities indicates that a single band picture applies, and that the
magnetic properties are dominated by the static and dynamic electronic
properties at the Co2 sites. We evidence that they display a strong in plane
electronic anisotropy initially unexpected but which accords perfectly with an
orbital ordering along the kagom\'e sublattice organization. These detailed
data should now permit realistic calculations of the electronic properties of
this compound in order to determine the incidence of electronic correlations.Comment: 20 pages, 15 figures, 3 tables, published in Phys. Rev. B, added new
Appendix
Na atomic order, Co charge disproportionation and magnetism in NaCoO for large Na contents
We have synthesized and characterized four different stable phases of Na
ordered NaCoO, for . Above 100 K they display similar
Curie-Weiss susceptibilities as well as ferromagnetic spin fluctuations
in the CoO planes revealed by Na NMR data. In all phases from
Co NMR data we display evidences that the Co disproportionate already
above 300 K into non magnetic Co and magnetic Co
sites on which holes delocalize. This allows us to understand that metallic
magnetism is favored for these large Na contents. Below 100 K the phases
differentiate, and a magnetic order sets in only for at
22 K. We suggest that the charge order also governs the low energy
scales and transverse couplings
On connection of the cosmic-ray coplanarity of most energetic particles with the collider long-range near-side "ridge" effect
Coplanarity of subcores of -ray--hadron families found in cosmic-ray
experiments at eV requires appearance of a coplanar
generation of most energetic particles. Long-range near-side "ridge" effect in
collisions at TeV was found by the CMS Collaboration in
two-particle correlation functions at
and . The FANSY 2.0 model
reproduces both the hadron coplanarity and "ridge" effect.Comment: Submission to SciPost Phys. Proc, PDFLaTeX, 6 pages, 4 PDF figure
59Co NMR study of the Co states in superconducting and anhydrous cobaltates
Co NMR spectra in oriented powders of NaCoO and in its
hydrated superconducting phase (HSC) NaCoO,1.3HO reveal a
single electronic Co state with identical independent NMR shift tensor.
These phases differ markedly from NaCoO, in which we resolve 3
types of Co sites. The large T variation of their spin susceptibilities and the anisotropy of the orbital susceptibility allow us
to conclude that charge disproportionation occurs, in a non magnetic Co
and two magnetic sites with about 0.3 and 0.7 holes in the multiplet.
The data are consistent with those for the single Co site in the anhydrous and
HSC phase assuming the expected Co charge.Comment: 5 pages, 3 figures, accepted for publication in Phys. Rev. Let
- …