A narrow dip structure has been observed at 1.9 GeV/c$^2$ in a study of diffractive photoproduction of the $~3pi^+3pi^-$ final state performed by the Fermilab experiment E687.
New results on quasi-free $eta$ photoproduction on the neutron and proton bound in a deuteron target are presented. The $gamma n to eta n$ quasi-free cross section reveals a bump-like structure which is not seen in the cross section on the proton. Th
is structure may signal the existence of a relatively narrow ($Msim 1.68$ GeV, $Gamma leq 30$ MeV) baryon state.
The total cross section for gamma p -> 3pi0 p has been measured for the first time from threshold to 1.4 GeV using the tagged photon beam of the Mainz Microtron. The equipment utilized the Crystal Ball multiphoton spectrometer, the TAPS forward detec
tor and a particle identification detector. The gamma p -> 3pi0 p total cross section has two broad enhancements at sqrt{s}~1.5 GeV and 1.7 GeV. We obtained the ratio of the total cross sections gamma p -> 3pi0 p to gamma p -> eta p equal to 0.014 pm 0.001 at sqrt{s}~1.5 GeV.
Evidence is presented for the decay $B_c+rightarrow J/psi 3pi^+2pi^-$ using proton-proton collision data, corresponding to an integrated luminosity of 3fb$^{-1}$, collected with the LHCb detector. A signal yield of $32pm8$ decays is found with a sign
ificance of 4.5 standard deviations. The ratio of the branching fraction of the $B_c^+rightarrow J/psi 3pi^+ 2pi^-$ decay to that of the $B_c^+ rightarrow J/psi pi^+$ decay is measured to be $$ frac{Br (B_c^+ rightarrow J/psi 3pi^+2pi^)}{Br (B_c^+ rightarrow J/psi pi^+)} = 1.74pm0.44pm0.24, $$ where the first uncertainty is statistical and the second is systematic.
We report a preliminary measurement of the slope parameter $alpha$ for the $etato 3piz$ decay carried out with KLOE at DA$Phi$NE; where $alpha$ is the parameter describing the energy dependence of the square of the matrix element for this decay. By f
itting the event density in the Dalitz plot with a collected statistic of 420 pb$^{-1}$ we determine $alpha = -0.027 pm 0.004 (stat) ^{+0.004}_{-0.006} (syst)$. This result is consistent with current chiral perturbation theory calculations within the unitary approach.
E687 Collaboration: P.L. Frabetti
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(2001)
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"Evidence for a narrow dip structure at 1.9 GeV/c$^2$ in $3pi^+ 3pi^- $ diffractive photoproduction"
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Peter H. Garbincius
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