Observation of a new $\mathrm{\eta \pi^0\pi^0}$ resonance at 1900 $\mathrm{MeV/c^2}$ in two-photon scattering
- Karch, K.
- Antreasyan, D.
- Cabenda, R.
- Cartacci, A.
- Cavalli-Sforza, M.
- Clare, R.
- Compagnucci, A.
- Conforto, G.
- Cooper, S.
- Cowan, R.
- Coyne, D. G.
- Engler, A.
- Bartels, H. W. S.
- Fairfield, K.
- Folger, G.
- Fridman, A.
- Gaiser, J.
- Gelphman, D.
- Glaser, G.
- Godfrey, G.
- Graaf, K.
- Heimlich, F. H.
- Heinsius, F. H.
- Besset, D.
- Hofstadter, R.
- Irion, J.
- Jakubowski, Z.
- Janssen, H.
- Keh, S.
- Kiel, T.
- Kilian, H.
- Kirkbride, I.
- Kloiber, T.
- Kobel, M.
- Bieler, C.
- Koch, W. S.
- Konig, A. C.
- Konigsmann, Kay
- Kraemer, R. W.
- Kruger, S.
- Landi, G.
- Lee, R.
- Leffler, S.
- Lekebusch, R.
- Litke, A.
- Bienlein, J. K.
- Lockman, William S.
- Lowe, S.
- Lurz, B.
- Marlow, Daniel R.
- Marsiske, H.
- Maschmann, W. S.
- McBride, P.
- Messing, F.
- Metzger, W. J.
- Meyer, H.
- Bizzeti, A.
- Monteleoni, B.
- Muryn, B.
- Nernst, R.
- Niczyporuk, B.
- Nowak, G.
- Peck, C.
- Pelfer, P. G.
- Pollock, B.
- Porter, F.
- Prindle, D.
- Bloom, Elliott D.
- Ratoff, P.
- Reidenbach, M.
- Renger, B.
- Rippich, C.
- Scheer, M.
- Schmitt, P.
- Schotanus, J.
- Schutte, J.
- Schwarz, Andreas S.
- Sievers, D.
- Brock, I.
- Skwarnicki, T.
- Stock, V.
- Strauch, K.
- Strohbusch, U.
- Tompkins, J.
- Trost, H. J.
- van Uitert, B.
- Van de Walle, R. T.
- Vogel, H.
- Voigt, A.
- Brockmuller, K.
- Volland, U.
- Wachs, K.
- Wacker, K.
- Walk, W. S.
- Wegener, H.
- Williams, D.
- Zschorsch, P.
- Crystal Ball Collaboration
DOIAbstract
Using the Crystal Ball detector at the DORIS II $e^+e^−$ storage ring, we measure the $ηπ^0π^0$ mass spectrum in the reaction $e^+e^−→e^+e^−ηπ^0π^0→e^+e^−6γ$ from the ηπ0π0 threshold to about 2500 MeV/c$^2$. The spectrum is dominated by the η′, for which we determine $Γγγ(η′)BR(η'→6γ)=0.36±0.02±0.03$ keV. In addition, we observe an enhancement in the cross section near 1900 MeV/c$^2$ which we attribute to the two-photon production of a new resonance X(1900). The angular distributions and the invariant mass distribution of the ηπ0 subsystem are consistent with those expected for the hypothetical η2 meson with $JPC=2\pm$. For this JP assignment the resonance parameters are M(X) = 1876 ±35±50 MeV/c$^2$, Γtot(X)=228±90±34 MeV/c$^2$ and $Γγγ(X)B...
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