757 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
The electronic spectra of protonated PANH molecules
Aims. This study was designed to examine the viability of protonated
nitrogen-substituted polycyclic aromatic hydrocarbons (H+PANHs) as candidates
for the carriers of the diffuse interstellar bands (DIBs). Methods. We obtained
the electronic spectra of two protonated PANH cations, protonated acridine and
phenanthridine, using parent ion photo-fragment spectroscopy and generated
theoretical electronic spectra using ab initio calculations. Results. We show
that the spectra of the two species studied here do not correspond to known
DIBs. However, based on the general properties derived from the spectra of
these small protonated nitrogen-substituted PAHs, we propose that larger H+PANH
cations represent good candidates for DIB carriers due to the expected
positions of their electronic transitions in the UV-visible and their narrow
spectral bands.Comment: 7 pages, 2 figures, accepted for publication in A&
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
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
Photoinduced dynamics in protonated aromatic amino acid
UV photoinduced fragmentation of protonated aromatics amino acids have
emerged the last few years, coming from a situation where nothing was known to
what we think a good understanding of the optical properties. We will mainly
focus this review on the tryptophan case. Three groups have mostly done
spectroscopic studies and one has mainly been involved in dynamics studies of
the excited states in the femtosecond/picosecond range and also in the
fragmentation kinetics from nanosecond to millisecond. All these data, along
with high level ab initio calculations, have shed light on the role of the
different electronic states of the protonated molecules upon the fragmentation
mechanisms
- …