2,005 research outputs found
excited states: a molecular approach with heavy-quark spin symmetry
The LHCb Collaboration has recently discovered five excited states
with masses between 3 and 3.1 GeV, four of them corroborated by the Belle
Collaboration. We analyse the dynamical generation of these states within a
molecular baryon-meson model that is consistent with both chiral and
heavy-quark spin symmetries. Earlier predictions within this model found five
states with masses below 3 GeV. Thus, in order to study the possible
identification of any of these states with the experimental ones in the correct
energy region, we explore two different regularization schemes, that is, a
modified regularization subtraction method and a cutoff regularization scheme.
We find that at least three of the dynamically generated states can be
identified with the experimental ones and have spin-parity or
Comment: 6 pages, 3 tables, 1 figure, contribution based on a keynote parallel
talk of the 8th International Conference on Quarks and Nuclear Physics
(QNP2018), November 13-17, 2018, Tsukuba (Japan
Towards the implementation of a preference-and uncertain-aware solver using answer set programming
Logic programs with possibilistic ordered disjunction (or LPPODs) are a recently defined logic-programming framework based on logic programs with ordered disjunction and possibilistic logic. The framework inherits the properties of such formalisms and merging them, it supports a reasoning which is nonmonotonic, preference-and uncertain-aware. The LPPODs syntax allows to specify 1) preferences in a qualitative way, and 2) necessity values about the certainty of program clauses. As a result at semantic level, preferences and necessity values can be used to specify an order among program solutions. This class of program therefore fits well in the representation of decision problems where a best option has to be chosen taking into account both preferences and necessity measures about information. In this paper we study the computation and the complexity of the LPPODs semantics and we describe the algorithm for its implementation following on Answer Set Programming approach. We describe some decision scenarios where the solver can be used to choose the best solutions by checking whether an outcome is possibilistically preferred over another considering preferences and uncertainty at the same time.Postprint (published version
Photon induced Lambda(1520) production and the role of the K^* exchange
We study the photon induced Lambda(1520) production in the effective
Lagrangian method near threshold, E_\gamma^{LAB}<2 GeV, and in the quark-gluon
string model at higher energies 3 GeV < E_\gamma^{LAB} < 5 GeV. In particular,
we study the role of the K^* exchange for the production of Lambda(1520) within
the SU(6) Weinberg-Tomozowa chiral unitary model proposed in Phys. Rev. D74
(2006) 034025. The coupling of the Lambda(1520) resonance to the N \bar K^*
pair, which is dynamically generated, turns out to be relatively small and,
thus, the K exchange mechanism dominates the reaction. In the higher energy
region, where experimental data are available, the quark-gluon string mechanism
with the K Regge trajectory reproduces both the energy and the angular
distribution dependences of the Lambda(1520) photo-production reaction.Comment: 20 pages and 6 page
: what has been really seen?
The resonant structure has been experimentally
observed in the and decays. This structure is intriguing since it is a prominent candidate of
an exotic hadron. Yet, its nature is unclear so far. In this work, we
simultaneously describe the and invariant mass
distributions in which the peak is seen using amplitudes with exact
unitarity. Two different scenarios are statistically acceptable, where the
origin of the state is different. They correspond to using energy
dependent or independent -wave interaction. In the first one,
the peak is due to a resonance with a mass around the
threshold. In the second one, the peak is produced by a virtual state
which must have a hadronic molecular nature. In both cases the two
observations, and , are shown to have the same
common origin, and a bound state solution is not allowed. Precise
measurements of the line shapes around the threshold are called for
in order to understand the nature of this state.Comment: 6 pages, 6 figure
- …