18 research outputs found
On causality, unitarity and perturbative expansions
We present a pedagogical case study how to combine micro-causality and
unitarity based on a perturbative approach. The method we advocate constructs
an analytic extrapolation of partial-wave scattering amplitudes that is
constrained by the unitarity condition. Suitably constructed conformal mappings
help to arrive at a systematic approximation of the scattering amplitude. The
technique is illustrated at hand of a Yukawa interaction. The typical case of a
superposition of strong short-range and weak long-range forces is investigated.Comment: 12 pages, 12 figure
Does the enhancement observed in contain two -wave higher charmonia?
Solved is a new puzzle raised by the observation of an enhancement structure
Z(3930) in . If categorizing Z(3930) as
suggested by Belle and BaBar, we must explain why
dominantly decaying into is missing in the
invariant mass spectrum. In this work, we propose that the Z(3930)
enhancement structure may contain two -wave higher charmonia
{} and . We show that this assumption is
supported by our analysis of the invariant mass spectrum and
distribution of . This observation
would not only provide valuable information of two P-wave higher charmonia
and , but also serve as the crucial test of our
novel proposal to the observed enhancement structure Z(3930), especially at the
forthcoming BelleII and the approved SuperB.Comment: 5 pages, 2 tables, 3 figures. More contents and discussions adde
On kinematical constraints in boson-boson systems
We consider the scattering of two-bosons with negative parity and spin 0 or
1. Starting from helicity partial-wave scattering amplitudes we derive
transformations that eliminate all kinematical constraints. Such amplitudes are
expected to satisfy partial-wave dispersion relations and therefore provide a
suitable basis for data analysis and the construction of effective field
theories. Our derivation relies on a decomposition of the various scattering
amplitudes into suitable sets of invariant functions. A novel algebra was
developed that permits the efficient computation of such functions in terms of
computer algebra codes.Comment: 14 pages, 8 table
Electromagnetic transitions in an effective chiral Lagrangian with the eta-prime and light vector mesons
We consider the chiral Lagrangian with a nonet of Goldstone bosons and a
nonet of light vector mesons. The mixing between the pseudoscalar mesons eta
and eta-prime is taken into account. A novel counting scheme is suggested that
is based on hadrogenesis, which conjectures a mass gap in the meson spectrum of
QCD in the limit of a large number of colors. Such a mass gap would justify to
consider the vector mesons and the eta-prime meson as light degrees of freedom.
The complete leading order Lagrangian is constructed and discussed. As a first
application it is tested against electromagnetic transitions of light vector
mesons to pseudoscalar mesons. Our parameters are determined by the
experimental data on photon decays of the omega, phi and eta-prime meson. In
terms of such parameters we predict the corresponding decays into virtual
photons with either dielectrons or dimuons in the final state.Comment: 17 pages, extended discussion on mixin
Mass spectrum of the axial-vector hidden charmed and hidden bottom tetraquark states
In this article, we perform a systematic study of the mass spectrum of the
axial-vector hidden charmed and hidden bottom tetraquark states using the QCD
sum rules, and identify the as an axial-vector tetraquark state
tentatively.Comment: 24 pages, 38 figures, slight revisio
Phenomenology of Pc(4380)+, Pc(4450)+ and related states
The and states recently discovered at LHCb have
masses close to several relevant thresholds, which suggests they can be
described in terms of meson-baryon degrees of freedom. This article explores
the phenomenology of these states, and their possible partners, from this point
of view. Competing models can be distinguished by the masses of the neutral
partners which have yet to be observed, and the existence or otherwise of
further partners with different isospin, spin, and parity. Future experimental
studies in different decay channels can also discriminate among models, using
selection rules and algebraic relations among decays. Among the several
possible meson-baryon pairs which could be important, one implies that the
states are mixtures of isospins 1/2 and 3/2, with characteristic signatures in
production and decay. A previous experimental study of a Cabibbo-suppressed
decay showed no evidence for the states, and further analysis is required to
establish the significance of this non-observation. Several intriguing
similarities suggest that is related to the meson.Comment: 16 pages, 1 figure. Journal version (some very minor changes from
arXiv v1
Possibility to observe higher n(3)D(1) bottomonium states in the e(+)e(-) processes
The possibility to observe new bottomonium states with JPC=1 - in the region 10.7-11.1 GeV is discussed. The analysis of the dielectron widths shows that the (n+1)S13 and nD13 states (n 3) may be mixed with a rather large mixing angle, θ 30°, and this effect provides the correct values of Γee(Υ(10580)) and Γee(Υ(11020)). On the other hand, the S-D mixing gives rise to an increase by 2 orders of magnitude of the dielectron widths of the mixed Υ (nD13) resonances (n=3, 4, 5), which originate from pure D-wave states. The value Γee(Υ (3D))=0.095-0.025+0.028keV is obtained, being only ∼3 times smaller than the dielectron width of Υ(10580), while Γee(Υ (5D))∼135eV appears to be close to Γee(Υ(11020)) and therefore this resonance may become manifest in the e+e- experiments. The mass differences between M(nD) and M((n+1)S) (n=4, 5) are shown to be rather small, 50±10MeV. © 2009 The American Physical Society