Experimental study of the inclusiveη-spectrum fromp\(\bar p\) annihilations at rest in liquid hydrogen

The inclusive η-momentum spectrum from\(\bar p\) annihilations at rest in liquid hydrogen was measured at LEAR. Branching ratios were obtained for $$\begin{gathered} p\bar p \to \eta \omega \left( {1.04_{ - 0.10}^{ + 0.09} } \right)\% ,\eta \rho ^0 \left( {0.53_{ - 0.08}^{ + 0.20} } \right)\% , \hfill \\ \pi a_2 \left( {8.49_{ - 1.10}^{ + 1.05} } \right)\% ,\eta \pi ^0 \left( {1.33 \pm 0.27} \right) \times 10^{ - 4} , \hfill \\ \end{gathered} $$ , and ηη(8.1±3.1)×10−5. An upper limit for\(p\bar p \to \eta \eta '\) of 1.8×10−4 at 95% CL was found. The ratio of the branching ratios is BR(ηϱ)/BR(ηω)=0.51 −0.06 +0.20 . For the ratio of branching ratios into two pseudoscalar mesons, we have BR(ηπ0)/BR(π0π0)=0.65±0.14, BR(ηη)/BR(π0π0), BR(ηη ′ )/BR(π0π0) at 95% CL, and BR(ηη)/BR(ηπ0).