Measurement of branching fractions and charge asymmetries in B+ decays to eta pi+, eta K+, eta rho+, and eta' pi+, and search for B0 decays to eta K0 and eta omega

We present measurements of branching fractions and charge asymmetries for six B-meson decay modes with an eta or eta(') meson in the final state. The data sample corresponds to 232 x 10(6) BB pairs collected with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) B Factory at SLAC. We measure the branching fractions (in units of 10(-6)): B(B+ -->eta pi(+))=5.1+/-0.6+/-0.3, B(B+ etaK+)=3.3+/-0.6+/-0.3, B(B0-->etaK0)=1.5+/-0.7+/-0.1 (<2.5 at 90% C.L.), B(B+-->eta rho(+))=8.4+/-1.9+/-1.1, B(B0-->eta omiga)=1.0+/-0.5+/-0.2 (<1.9 at 90% C.L.), and B(B+-->eta(')pi(+))=4.0+/-0.8+/-0.4, where the first uncertainty is statistical and second systematic. For the charged modes we also determine the charge asymmetries, all found to be compatible with zero.     

Dispersion relations for $$\eta '\rightarrow \eta \pi \pi $$

We present a dispersive analysis of the decay amplitude for \(\eta '\rightarrow \eta \pi \pi \) that is based on the fundamental principles of analyticity and unitarity. In this framework, final-state interactions are fully taken into account. Our dispersive representation relies only on input for the \({\pi \pi }\) and \({\pi }\eta \) scattering phase shifts. Isospin symmetry allows us to describe both the charged and neutral decay channel in terms of the same function. The dispersion relation contains subtraction constants that cannot be fixed by unitarity. We determine these parameters by a fit to Dalitz-plot data from the VES and BES-III experiments. We study the prediction of a low-energy theorem and compare the dispersive fit to variants of chiral perturbation theory.     

Observation of a tensor glueball in the reactions p\bar p \to \pi \pi ,\eta \eta ,\eta \eta '

Partial wave analysis of the reactions $p\bar p \to \pi \pi ,\eta \eta ,\eta \eta '$ in the region of invariant masses 1900–2400 MeV indicates the existence of four relatively narrow tensor-isoscalar resonances ? ₂(1920), ? ₂(2020), ? ₂(2240), ? ₂(2300), as well as the broad state ? ₂(2000). The determined decay couplings of the broad resonance ? ₂(2000) → π⁰π⁰, ηη, ηη′ satisfy the relations appropriate to those of a tensor glueball, while the couplings of other tensor states do not, thus verifying the glueball nature of ? ₂(2000).     

Two-body B meson decays to eta and eta('): observation of B --> eta K*

In a sample of 19 x 10(6) produced B mesons, we have observed the decays B-->eta K(*) and improved our previous measurements of B-->eta'K. The branching fractions we measure for these decay modes are B(B+-->eta K(*+)) = (26.4(+9.6)(-8.2)+/-3.3)x10(-6), B(B(0)-->eta K(*0)) = (13.8(+5.5)(-4.6)+/-1.6)x10(-6), B(B(+)-->eta'K(+) = (80(+10)(-9)+/-7)x10(-6), and B(B(0)-->eta'K0) = (89(+18)(-16)+/-9)x10(-6). We have searched with comparable sensitivity for related decays and report upper limits for these branching fractions.     

Search for rare and forbidden eta(') decays

We have searched for rare and forbidden decays of the eta(') meson in hadronic events at the CLEO II detector. The search is conducted on 4.80 fb(-1) of e(+)e(-) collisions at 10.6 GeV center-of-mass energy at the Cornell Electron Storage Ring. We find no signals, and set 90% confidence level upper limits of their branching fractions: B(eta(')-->e(+)e(-)eta)<2.4x10(-3), B(eta(')-->e(+)e(-)pi(0))<1. 4x10(-3), B(eta(')-->e(+)e(-)gamma)<0.9x10(-3), and B(eta(')-->e&mgr;)<4.7x10(-4). We also fit the matrix element of the eta(')-->pi(+)pi(-)eta Dalitz plot with the parametrization |M|(2) = A|1+alphay|(2), where y is a linear function of the kinetic energy of the eta, and find Re (alpha) = -0.021+/-0.025.