P-wave spin-spin splitting and meson loops

In quark potential models the hyperfine splitting of P-wave mesons is zero in the nonrelativistic limit, a prediction strikingly confirmed by experiment in both charmonia and bottomonia. The result, however, ignores the coupling of bare quarkonia to meson-meson pairs. This coupling causes mass shifts among the states and so could potentially spoil the quark model prediction. This turns out not to be the case: in a variety of models the hyperfine splitting remains small despite large mass shifts. This is shown to be a generic feature of models in which the coupling involves the creation of a light quark pair with spin-one and the quark spin wavefunctions are conserved. This talk reports on the results of Phys. Rev. D84, 034021 (2011).Comment: 4 pages, typo corrected. Contribution to the Proceedings of the XIV International Conference on Hadron Spectroscopy (Hadron 2011), 13-17 June 2011, Munich, German

Strong decay amplitudes using the Talmi-Moshinsky transformation and the suppressed production of the 1−+1^{-+} hybrid

The Talmi-Moshinsky transformation is applied to the strong decay and production of mesons. Amplitudes for conventional mesons are obtained in a simple way and are generalised to encompass the production and decay of hybrid states. The selection rule disfavouring hybrid decay into pairs of identical S-wave mesons has a natural explanation and a new class of selection rules is uncovered with implications for production of the exotic $1^{-+}$ hybrid in $e^+e^-$ experiments, charmonia decays and the lattice.Comment: 15 pages; some significant changes in revised version including additional phenomenolog

Dynamics of hadron strong production and decay

We generalize results of lattice QCD to determine the spin-dependent symmetries and factorization properties of meson production in OZI allowed processes. This explains some conjectures previously made in the literature about axial meson decays and gives predictions for exclusive decays of vector charmonia, including ways of establishing the structure of Y(4260) and Y(4325) from their S-wave decays. Factorization gives a selection rule which forbids $e^+e^- \to D^* D_2$ near threshold with the tensor meson in helicity 2. The relations among amplitudes for double charmonia production \e^+e^-\to \psi\chi_{0,1,2} are expected to differ from the analagous relations among light flavour production such as \e^+e^-\to \omega f_{0,1,2}.Comment: 13 pages; journal versio

Angular momentum coefficients for meson strong decay and the unquenched quark model (CHARM 2013)

Most models for the strong decay of mesons, as well as unquenched quark models which incorporate the effect of coupling to meson-meson channels, assume that the coupling is driven by the creation of a quark-antiquark pair in spin triplet. Their matrix elements can be factorised into a sum over (model-dependent) spatial matrix elements multiplied by (model-independent) coefficients. A general expression for these coefficients is obtained, and their properties are studied. Numerical tables of the coefficients can be used as a starting point for future calculations. The coefficients lead to model-independent predictions for decay amplitudes and widths, and can explain how mass shifts in the unquenched quark model do not spoil successful predictions of the ordinary (quenched) quark model. This article is based on work which will be presented in a forthcoming paper.Comment: 6 pages. To appear in the proceedings of The 6th International Workshop on Charm Physics (CHARM 2013

The 2^-+ assignment for the X(3872)

Very recently the BaBar collaboration has put forward a claim that the X(3872) is not a 1^++ resonance, as most of the phenomenological work on the subject was relying on, but rather a 2^-+ one. We examine the consequences of this quantum number assignment for the solution of the X(3872) puzzle. The molecular interpretation appears less likely, and the conventional charmonium interpretation should be reconsidered. There are several well-known difficulties with this interpretation, to which we add a new one: the production cross section at CDF is predicted to be much smaller than that observed. We also confirm, using a relativistic string model, the conclusion from potential models that the mass of the state is not consistent with expectations. In the tetraquark interpretation the 2^-+ assignment implies a rich spectrum of partner states, although the X(3872) may be among the few which are narrow enough to be observable.Comment: 18 pages, 6 figures, 4 tables; minor style corrections. Version to appear in PR

A note on the comparison of three near infrared reflectance spectroscopy calibration strategies for assessing herbage quality of ryegrass

peer-reviewedPerennial ryegrass (n = 1,836), Italian ryegrass (n = 137) and hybrid ryegrass (n = 103) herbage was taken from harvested plots from the Irish national variety evaluation scheme and analysed for in vitro dry matter digestibility, water soluble carbohydrate concentration, crude protein concentration and buffering capacity. Spectral data were obtained using near infrared reflectance spectroscopy and three calibration strategies (global, species-specific or local) were utilised to relate the reference values to the spectral data. The local strategy generally provided the poorest estimation of herbage composition, with global and species-specific calibration strategies producing similarly accurate estimates of each quality trait. The higher accuracy and easier maintenance of the global strategy make it the recommended calibration method for analysing quality of ryegrass.Department of Agriculture, Food and the Marine Research Stimulus Fund (07 526