THE DECAY η'c → ηc ππ

It is pointed out that the decay of the recently observed charmonium η'c resonance, η'c → ηc ππ is simply related to the well-studied decay ψ′ → J/ψππ and can thus be used for absolute normalization of other decay modes of the η'c. The total rate of the discussed decay should be approximately three to four times the corresponding rate for the ψ′ resonance making the channel with charged pions the most probable exclusive decay mode of the η'c with the branching ratio in the range 5–10%.

BUILDING THE GLUON DISTRIBUTION IN NUCLEONS

We present a direct perturbative QCD calculation of the gluon distribution in nucleons as a QCD radiative effect. We assume that the only infrared regulator is the nucleon's radius which emerges as a natural cutoff. A technique is introduced which allows constructing the glue step by step keeping a careful balance of valence, gluons and sea and obeying all constraints. The absolute normalization and shape of the calculated gluon distribution are in good agreement with the experimental determinations.

N=2 LANDAU-GINZBURG VS. CALABI-YAU σ-MODELS: NON-PERTURBATIVE ASPECTS

We discuss some nonperturbative aspects of the correspondence between N=2 Landau-Ginzburg orbifolds and Calabi-Yau σ-models. We suggest that the correct framework is Deligne’s theory of mixed Hodge structures (closely related to catastrophe theory). We derive a general topological formula for the chiral ring OPE coefficients of any Landau-Ginzburg model, including the absolute normalization. This follows from the identification of spectral flow with Grothendieck’s local duality. Wherever the LG model has a CY interpretation, its OPE coefficients are equal to those of the σ-model as given by intersection theory, including normalization. We discuss at length the tricky case of a number of LG fields greater than c/3+2, presenting explicit examples. In passing, we get many results about the geometry of moduli spaces for such conformal theories. We explain the beautiful algebraic geometry connected with a remarkable model pointed out by Vafa, and its relations with moduli space geometry.

Recent studies of radiative capture and photodisintegration in few-nucleon systems

A recent measurement of the neutron–proton radiative capture cross section at Tn = 185 MeV is discussed in the context of previous data and current theories. The method used to obtain an absolute normalization of the data is outlined. Recent data on proton–deuteron capture are also presented and discussed. Future plans are indicated.