7,020 research outputs found
Vacuum structure of a modified MIT Bag
An alternative to introducing and subsequently renormalizing classical
parameters in the expression for the vacuum energy of the MIT bag for quarks is
proposed in the massless case by appealing to the QCD trace anomaly and scale
separation due to asymptotic freedom. The explicit inclusion of gluons implies
an unrealistically low separation scale.Comment: 5 pages, 2 figure
Radiative proton-antiproton annihilation and isospin mixing in protonium
A detailed analysis of the radiative annihilation is made in the
framework of a two-step formalism, the annihilates into meson
channels containing a vector meson with a subsequent conversion into a photon
via the vector dominance model (VDM). Both steps are derived from the
underlying quark model. First, branching ratios for radiative protonium
annihilation are calculated and compared with data. Then, details of the
isospin interference are studied for different models of the initial protonium
state and also for different kinematical form factors. The isospin interference
is shown to be uniquely connected to the mixing in the
protonium state. Values of the interference terms directly deduced from data
are consistent with theoretical expectations, indicating a dominant
component for the and a sizable component for the
protonium state. The analysis is extended to the
transition, where the large observed branching ratio remains unexplained in the
VDM approach.Comment: 34 pages, RevTeX, 2 figures, to appear in Phys. Rev. C; typos
correcte
Correlation of circular differential optical absorption with geometric chirality in plasmonic meta-atoms
We report a strong correlation between the calculated broadband circular differential optical absorption (CDOA) and the geometric chirality of plasmonic meta-atoms with two-dimensional chirality. We investigate this correlation using three common gold meta-atom geometries: L-shapes, triangles, and nanorod dimers, over a broad range of geometric parameters. We show that this correlation holds for both contiguous plasmonic meta-atoms and non-contiguous structures which support plasmonic coupling effects. A potential application for this correlation is the rapid optimization of plasmonic nanostructure for maximum broadband CDOA
The exclusive rare decays B -> K l(bar) l and B_c -> D(D*) l(bar) l in a relativistic quark model
We study the exclusive rare decay B -> K l(bar) l. We calculate the relevant
form factors within a relativistic constituent quark model, for the first time
without employing the impulse approximation. The calculated form factors are
used to evaluate differential decay rates and polarization observables. We
present results on the q2-dependence of a set of observables with and without
long-distance contributions. A similar analysis is done for the exclusive rare
decays B_c -> D (D*) l(bar) l with special emphasis on the cascade decay B_c ->
D* (-> D pi) l(bar) l. We derive a four-fold angular decay distribution for
this process in terms of helicity amplitudes including lepton mass effects. The
four-fold angular decay distribution allows to define a number of physical
observables which are amenable to measurement. We compare our results with the
results of other studies.Comment: 28 pages, 12 figure
Generalized parton distributions in AdS/QCD
The nucleon helicity-independent generalized parton distributions (GPDs) of
quarks are calculated in the zero skewness case, in the framework of the
AdS/QCD model. The present approach is based on a matching procedure of sum
rules relating the electromagnetic form factors to GPDs and AdS modes.Comment: 8 pages, 12 figures; Discussion extended with more examples in impact
parameter dependent GPD
Effect of the channel and interference phenomena in the two-pion transitions of charmonia and bottomonia
The basic shape of di-pion mass spectra in the two-pion transitions of both
charmonia and bottomonia states is explained by an unified mechanism based on
contributions of the , and coupled channels
including their interference. The role of the individual resonances in
shaping the di-pion mass distributions in the charmonia and bottomonia decays
is considered.Comment: 8 pages, 4 figures, Talk at the XXIII International Baldin Seminar on
High Energy Physics Problems "Relativistic Nuclear Physics \& Quantum
Chromodynamics" (Dubna, Russia, 19--24 September 2016). arXiv admin note:
text overlap with arXiv:1610.0789
The interference effects of multi-channel pion-pion scattering contributions to the final states of - and -meson family decays
It is shown that the basic shape of dipion mass distributions in the two-pion
transitions of both charmonia and bottomonia states are explained by an unified
mechanism based on the contribution of the , and
coupled channels including their interference.Comment: 5 pages, 3 figures, talk at the14th International Workshop on Meson
Production, Properties and Interaction (Krakow, Poland, 2nd - 7th June 2016
- …