23,963 research outputs found
Y(4260) as a mixed charmonium-tetraquark state
Using the QCD sum rule approach we study the Y(4260) state assuming that it
can be described by a mixed charmonium-tetraquark current with
quantum numbers. For the mixing angle around , we obtain a value for the mass which is in good agreement with the
experimental mass of the Y(4260). However, for the decay width we find the
value \Ga_Y \approx (1.0\pm 0.2) MeV which is not compatible with the
experimental value \Ga \approx (88\pm 23) MeV. Therefore, we conclude that,
although we can explain the mass of the Y(4260), this state cannot be described
as a mixed charmonium-tetraquark state since, with this assumption, we can not
explain its decay width.Comment: 9 pages, 6 figure
Relation between and from QCD
We have studied, using double ratio of QCD (spectral) sum rules, the ratio
between the masses of and X(3872) assuming that they are respectively
described by the and molecular currents. We found
(within our approximation) that the masses of these two states are almost
degenerate. Since the pion exchange interaction between these mesons is exactly
the same, we conclude that if the observed X(3872) meson is a
molecule, then the molecule should also exist with approximately the
same mass. An extension of the analysis to the -quark case leads to the same
conclusion. We also study the SU(3) breakings for the mass
ratios. Motivated by the recent Belle observation of two states, we
revise our determination of by combining results from exponential and
FESR sum rules.Comment: revised version to appear on Phys. Lett.
Study of and interactions in and relationship to the , states
We use the local hidden gauge approach in order to study the and
interactions for isospin I=1. We show that both interactions via
one light meson exchange are not allowed by OZI rule and, for that reason, we
calculate the contributions due to the exchange of two pions, interacting and
noninteracting among themselves, and also due to the heavy vector mesons. Then,
to compare all these contributions, we use the potential related to the heavy
vector exchange as an effective potential corrected by a factor which takes
into account the contribution of the others light mesons exchange. In order to
look for poles, this effective potential is used as the kernel of the
Bethe-Salpeter equation. As a result, for the interaction we find
a loosely bound state with mass in the range MeV, very close to
the experimental value of the reported by Belle Collaboration. For
the case, we find a cusp at MeV for all spin
cases.Comment: 23 pages, 20 figure
Thick Braneworlds and the Gibbons-Kallosh-Linde No-go Theorem in the Gauss-Bonnet Framework
The sum rules related to thick braneworlds are constructed, in order to
encompass Gauss-Bonnet terms. The generation of thick branes is hence proposed
in a periodic extra dimension scenario, what circumvents the
Gibbons-Kallosh-Linde no-go theorem in this context.Comment: 6 pages, to appear in the EPL. arXiv admin note: text overlap with
arXiv:1406.632
Braneworlds scenarios in a gravity model with higher order spatial three-curvature terms
In this work we study a Horava-like five-dimensional model in the context of
braneworld theory. To begin with, the equations of motion of such model are
obtained and, within the realm of warped geometry, we show that the model is
consistent if and only if takes its relativistic value 1.
Furthermore, since the first derivative of the warp factor is discontinuous
over the branes, we show that the elimination of problematic terms involving
the square of the warp factor second order derivatives are eliminated by
imposing detailed balance condition in the bulk. Afterwards, the Israel's
junction conditions are computed, allowing the attainment of an effective
Lagrangian in the visible brane. In particular, for a (4+1)-dimensional
Horava-like model defined in the bulk without cosmological constant, we show
that the resultant effective Lagrangian in the brane corresponds to a
(3+1)-dimensional Horava-like model with an emergent positive cosmological
constant but without detailed balance condition. Now, restoration of detailed
balance condition, at this time imposed over the brane, plays an interesting
role by fitting accordingly the sign of the arbitrary constant that
labels the extra terms in the model, insuring a positive brane tension and a
real energy for the graviton within its dispersion relation. To end up with,
the brane consistency equations are obtained and, as a result, we show that the
detailed balance condition again plays an essential role in eliminating bad
behaving terms and that the model admits positive brane tensions in the
compactification scheme if, and only if, is negative, what is in
accordance with the previous result obtained for the visible brane.Comment: 23 pages, 1 figure, title modifie
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