Formation of spin-one mesons by photon-photon fusion
1988; American Physical Society; Volume: 38; Issue: 1 Linguagem: Inglês
10.1103/physrevd.38.1
ISSN1538-4500
AutoresH. Aihara, M. Alston‐Garnjost, R. E. Avery, A. Barbaro-Galtieri, A. Barker, B. A. Barnett, D. Bauer, A. Bay, H. -U. Bengtsson, G. J. Bobbink, C. D. Buchanan, A. Buijs, D. O. Caldwell, H. Y. Chao, S-B. Chun, A. R. Clark, G. Cowan, D. Crane, O. I. Dahl, M. Daoudi, K. A. Derby, J. J. Eastman, Philippe Eberhard, T. K. Edberg, A. M. Eisner, R. Enomoto, F.C. Erné, K. Fairfield, J. M. Hauptman, W. Hofmann, J. Hylen, T. Kamae, H. S. Kaye, Robert W. Kenney, S. Khacheryan, R. Kofler, W. G. J. Langeveld, J. G. Layter, W.T. Lin, F. Linde, S. C. Loken, A. Lu, G. Lynch, R. J. Madaras, B. D. Magnuson, G. Masek, L. G. Mathis, J. A. J. Matthews, S. J. Maxfield, E. S. Miller, W. Moses, D. R. Nygren, P. J. Oddone, H. P. Paar, S. K. Park, D. E. Pellett, M. Pripstein, M. T. Ronan, R. R. Ross, F. Rouse, K. A. Schwitkis, J.C. Sens, G. Shapiro, B. C. Shen, W. Slater, J. R. Smith, J. S. Steinman, R. W. Stephens, M. L. Stevenson, D. H. Stork, M. Strauss, M. K. Sullivan, T. Takahashi, S. Toutounchi, R. van Tyen, G. J. VanDalen, W. Vernon, W. Wagner, E. M. Wang, Y-X. Wang, W. A. Wenzel, Z. R. Wolf, H. Yamamoto, S. Yellin, C. Zeitlin,
Tópico(s)Atomic and Subatomic Physics Research
ResumoWe have observed the formation of two spin-one mesons in \ensuremath{\gamma}\ensuremath{\gamma} fusion reactions in which one photon was highly virtual. The first, consistent with being the ${J}^{\mathrm{PC}}$${=1}^{++}$ ${f}_{1}$(1285), was seen in the final state \ensuremath{\eta}${\ensuremath{\pi}}^{+}$${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$ (\ensuremath{\eta}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}), as was the \ensuremath{\eta}'(958). We have previously reported the observation of the second spin-one state, the X(1420), in the final state ${K}^{\ifmmode\pm\else\textpm\fi{}}$${K}_{S}^{0}$${\ensuremath{\pi}}^{\ensuremath{\mp}}$ (${K}_{S}^{0}$\ensuremath{\rightarrow}${\ensuremath{\pi}}^{+}$${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$). The formation of this state, which may be the ${f}_{1}$(1420) observed in hadronic interactions, is reanalyzed using a new model and more data. We consider whether the X(1420) could be the partner of the ${f}_{1}$(1285) in the ${J}^{\mathrm{PC}}$${=1}^{++}$ meson nonet. The \ensuremath{\gamma}${\ensuremath{\gamma}}^{\mathrm{*}}$ width of each resonance was determined in several ${Q}^{2}$ bins. Using a model due to Cahn with a \ensuremath{\rho} form factor, we obtained for the coupling parameter \ensuremath{\Gamma}${\ifmmode \tilde{}\else \~{}\fi{}}_{\ensuremath{\gamma}\ensuremath{\gamma}}$(${f}_{1}$(1285)) the value 2.4\ifmmode\pm\else\textpm\fi{}0.5\ifmmode\pm\else\textpm\fi{}0.5 keV.We also found B(X(1420)\ensuremath{\rightarrow}KK\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\pi})\ensuremath{\Gamma}${\mathrm{\ifmmode \tilde{}\else \~{}\fi{}}}_{\ensuremath{\gamma}\ensuremath{\gamma}}$(X(1420))=1.3\ifmmode\pm\else\textpm\fi{}0.5\ifmmode\pm\else\textpm\fi{}0.3 keV using a \ensuremath{\rho} form factor, or 0.63\ifmmode\pm\else\textpm\fi{}0.24\ifmmode\pm\else\textpm\fi{}0.15 keV using a \ensuremath{\varphi} form factor. The decay distributions of the observed X(1420) events are consistent with a decay proceeding via ${K}^{\mathrm{*}}$(892)K, and favor positive, but do not exclude negative, parity. Assuming that the X(1420) and the ${f}_{1}$(1285) are members of the same qq\ifmmode\bar\else\textasciimacron\fi{} meson nonet and that B(X(1420)\ensuremath{\rightarrow}KK\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\pi})\ensuremath{\approxeq}1, and using a \ensuremath{\varphi} form factor in the model for X(1420) formation, we determined the singlet-octet mixing angle of that nonet. The result, (45.4\ifmmode\pm\else\textpm\fi{}6.2)\ifmmode^\circ\else\textdegree\fi{}, agrees well with the 42.2\ifmmode^\circ\else\textdegree\fi{} implied by the Gell-Mann--Okubo quadratic mass formula; it is farther from the 35.3\ifmmode^\circ\else\textdegree\fi{} ideal mixing angle. Our results are thus consistent with the X(1420) being the mostly ss\ifmmode\bar\else\textasciimacron\fi{} isoscalar member of the axial-vector qq\ifmmode\bar\else\textasciimacron\fi{} meson nonet; however, we have no evidence contrary to hypotheses that the X(1420) is an exotic ${q}^{2}$q\ifmmode\bar\else\textasciimacron\fi{} $^{2}$ or qq\ifmmode\bar\else\textasciimacron\fi{}g state.
Referência(s)