2,721 research outputs found
The role of hyperfine mixing in semileptonic decays of doubly-heavy baryons
We analyze the effects of hyperfine mixing in semileptonic decays
of doubly heavy baryons. We qualitatively confirm the results by W. Roberts and
M. Pervin in Int. J. Mod. Phys. A, 2009, {\bf 24}: 2401-2413, finding that
mixing has a great impact on those transitions. However, predictions without
mixing differ by a factor of 2 and this discrepancy translates to the mixed
case where large differences in decay widths are observed between the two
calculations.Comment: 3 latex pages. Talk given at The 5-th International Conference on
Quarks and Nuclear Physics (QNP09), Beijing, September 200
The role of hyperfine mixing in semileptonic and electromagnetic decays of doubly-heavy baryons
We analyze the effects of hyperfine mixing in semileptonic and
electromagnetic decays of doubly heavy baryons.Comment: Talk given at the Chiral 10 Conferenc
The effect of hyperfine mixing in electromagnetic and semileptonic decays of doubly heavy baryons
We consider the role played by hyperfine mixing in electromagnetic and
semileptonic decays of doubly heavy baryons, which give rise to large
corrections to the decay widths in both cases.Comment: Talk given in Quark Confinement and the Hadron Spectrum IX, Madrid
September 201
Hyperfine mixing in semileptonic decay of doubly heavy baryons
We qualitatively corroborate the results of W. Roberts and M. Pervin in Int.
J. Mod. Phys. A 24, 2401 (2009) according to which hyperfine mixing greatly
affects the decay widths of semileptonic decays involving doubly heavy
baryons. However, our predictions for the decay widths of the unmixed
states differ from those reported in the work of Roberts and Pervin by a factor
of 2, and this discrepancy translates to the mixed case. We further show that
the predictions of heavy quark spin symmetry, might be used in the future to
experimentally extract information on the admixtures in the actual physical
baryons, in a model independent manner.Comment: 7 Latex pages, 4 Table
Heavy quark spin symmetric molecular states from and other coupled channels in the light of the recent LHCb pentaquarks
We consider the states, together with and other coupled channels, and take an interaction consistent with heavy
quark spin symmetry, with the dynamical input obtained from an extension of the
local hidden gauge approach. By fitting only one parameter to the recent three
pentaquark states reported by the LHCb collaboration, we can reproduce the
three of them in base to the mass and the width, providing for them the quantum
numbers and approximate molecular structure as ,
, and , and isospin
. We find another state around 4374 MeV, of
structure, for which indications appear in the experimental spectrum. Two other
near degenerate states of and nature are also found around 4520 MeV, which although less clear,
are not incompatible with the observed spectrum. In addition, a state at the same energy appears, which however does not couple
to in wave, and hence it is not expected to show up in the LHCb
experiment.Comment: 8 page
Nuclear effects on lepton polarization in charged-current quasielastic neutrino scattering
We use a correlated local Fermi gas (LFG) model, which accounts also for long
distance corrections of the RPA type and final-state interactions, to compute
the polarization of the final lepton in charged-current quasielastic neutrino
scattering. The present model has been successfully used in recent studies of
inclusive neutrino nucleus processes and muon capture. We investigate the
relevance of nuclear effects in the particular case of polarization in
tau-neutrino induced reactions for several kinematics of relevance for neutrino
oscillation experiments.Comment: 13 pages, 8 figure
Large Nc Weinberg-Tomozawa interaction and negative parity s--wave baryon resonances
It is shown that in the 70 and 700 SU(6) irreducible spaces, the SU(6)
extension of the Weinberg-Tomozawa (WT) s-wave meson-baryon interaction
incorporating vector mesons ({\it hep-ph/0505233}) scales as ,
instead of the well known behavior for its SU(3)
counterpart. However, the WT interaction behaves as order
within the 56 and 1134 meson-baryon spaces. Explicit expressions for the WT
couplings (eigenvalues) in the irreducible SU(2) spaces, for arbitrary
and , are given. This extended interaction is used as a kernel of
the Bethe-Salpeter equation, to study the large scaling of masses and
widths of the lowest--lying negative parity s-wave baryon resonances.
Analytical expressions are found in the limit, from which it
can be deduced that resonance widths and excitation energies behave
as order , in agreement with model independent arguments, and
moreover they fall in the 70-plet, as expected in constituent quark models for
an orbital excitation. For the 56 and 1134 spaces, excitation energies and
widths grow indicating that such resonances do not
survive in the large limit. The relation of this latter behavior
with the existence of exotic components in these resonances is discussed. The
interaction comes out repulsive in the 700.Comment: 21 pages, 3 figures, requires wick.sty and young.sty. Subsection
added. Conclusions revised. To appear in Physical Review
Resonances and the Weinberg--Tomozawa 56-baryon --35-meson interaction
Vector meson degrees of freedom are incorporated into the
Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian by using a scheme which
relies on spin--flavor SU(6) symmetry. The corresponding Bethe-Salpeter
approximation successfully reproduces previous SU(3)--flavor WT results for the
lowest-lying s--wave negative parity baryon resonances, and it also provides
some information on the dynamics of the heavier ones. Moreover, it also
predicts the existence of an isoscalar spin-parity bound
state (strangeness +1) with a mass around 1.7--1.8 GeV, unstable through
decay. Neglecting d-wave KN decays, this state turns out to be quite narrow
( MeV) and it might provide clear signals in reactions like
by looking at the three body
invariant mass.Comment: Talk given at the IVth International Conference on Quarks an Nuclear
Physics, Madrid, June 5th-10th 2006. Minor correction
Gravitational coupling of neutrinos in a medium
In a medium that contains electrons but not the other charged leptons, such
as normal matter, the gravitational interactions of neutrinos are not the same
for all the neutrino flavors. We calculate the leading order matter-induced
corrections to the neutrino gravitational interactions in such a medium and
consider some of their physical implications.Comment: 21 pages, Latex, uses axodraw.sty (typos corrected; two references
added. To appear in Phys. Rev. D
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