/ Experiment-HEP hep-ex/0703023

First observation and branching fraction and decay parameter measurements of the weak radiative decay Xi0 ---> Lambda e+ e-

Batley, J.R. (Cambridge U.) ; Kalmus, G.E. (Cambridge U.) ; Lazzeroni, C. (Cambridge U.) ; Munday, D.J. (Cambridge U.) ; Patel, M. (Cambridge U.) ; Slater, M.W. (Cambridge U.) ; Wotton, S.A. (Cambridge U.) ; Arcidiacono, R. (CERN) ; Bocquet, G. (CERN) ; Ceccucci, A. (CERN) ; Cundy, D. (CERN) ; Doble, N. (CERN) ; Falaleev, V. (CERN) ; Gatignon, L. (CERN) ; Gonidec, A. (CERN) ; Grafstrom, P. (CERN) ; Kubischta, W. (CERN) ; Mikulec, I. (CERN) ; Norton, A. (CERN) ; Panzer-Steindel, B. (CERN) ; Rubin, P. (CERN) ; Wahl, H. (CERN) ; Goudzovski, E. (Dubna, JINR) ; Hristov, P. (Dubna, JINR) ; Kekelidze, V. (Dubna, JINR) ; Litov, L. (Dubna, JINR) ; Madigozhin, D. (Dubna, JINR) ; Molokanova, N. (Dubna, JINR) ; Potrebenikov, Yu. (Dubna, JINR) ; Stoynev, S. (Dubna, JINR) ; Zinchenko, A. (Dubna, JINR) ; Monnier, E. (Chicago U.) ; Swallow, E. (Chicago U.) ; Winston, R. (Chicago U.) ; Sacco, R. (Edinburgh U.) ; Walker, A. (Edinburgh U.) ; Baldini, W. (INFN, Ferrara) ; Dalpiaz, P. (INFN, Ferrara) ; Frabetti, P.L. (INFN, Ferrara) ; Gianoli, A. (INFN, Ferrara) ; Martini, M. (INFN, Ferrara) ; Petrucci, F. (INFN, Ferrara) ; Savrie, M. (INFN, Ferrara) ; Scarpa, M. (INFN, Ferrara) ; Bizzeti, A. (INFN, Florence) ; Calvetti, M. (INFN, Florence) ; Collazuol, G. (INFN, Florence) ; Iacopini, E. (INFN, Florence) ; Lenti, M. (INFN, Florence) ; Ruggiero, G. (INFN, Florence) ; Veltri, M. (INFN, Florence) ; Behler, M. (Mainz U., Inst. Phys.) ; Eppard, K. (Mainz U., Inst. Phys.) ; Eppard, M. (Mainz U., Inst. Phys.) ; Hirstius, A. (Mainz U., Inst. Phys.) ; Kleinknecht, K. (Mainz U., Inst. Phys.) ; Koch, U. (Mainz U., Inst. Phys.) ; Marouelli, P. (Mainz U., Inst. Phys.) ; Masetti, L. (Mainz U., Inst. Phys.) ; Moosbrugger, U. (Mainz U., Inst. Phys.) ; Morales Morales, C. (Mainz U., Inst. Phys.) ; Peters, A. (Mainz U., Inst. Phys.) ; Wanke, R. (Mainz U., Inst. Phys.) ; Winhart, A. (Mainz U., Inst. Phys.) ; Dabrowski, A. (Northwestern U.) ; Fonseca Martin, T. (Northwestern U.) ; Velasco, M. (Northwestern U.) ; Anzivino, G. (INFN, Perugia) ; Cenci, P. (INFN, Perugia) ; Imbergamo, E. (INFN, Perugia) ; Lamanna, G. (INFN, Perugia) ; Lubrano, P. (INFN, Perugia) ; Michetti, A. (INFN, Perugia) ; Nappi, A. (INFN, Perugia) ; Pepe, M. (INFN, Perugia) ; Petrucci, M.C. (INFN, Perugia) ; Piccini, M. (INFN, Perugia) ; Valdata, M. (INFN, Perugia) ; Cerri, C. (INFN, Pisa) ; Costantini, F. (INFN, Pisa) ; Fantechi, R. (INFN, Pisa) ; Fiorini, L. (INFN, Pisa) ; Giudici, S. (INFN, Pisa) ; Mannelli, I. (INFN, Pisa) ; Pierazzini, G. (INFN, Pisa) ; Sozzi, M. (INFN, Pisa) ; Cheshkov, C. (DSM, DAPNIA, Saclay) ; Cheze, J.B. (DSM, DAPNIA, Saclay) ; De Beer, M. (DSM, DAPNIA, Saclay) ; Debu, P. (DSM, DAPNIA, Saclay) ; Gouge, G. (DSM, DAPNIA, Saclay) ; Marel, G. (DSM, DAPNIA, Saclay) ; Mazzucato, E. (DSM, DAPNIA, Saclay) ; Peyaud, B. (DSM, DAPNIA, Saclay) ; Vallage, B. (DSM, DAPNIA, Saclay) ; Holder, M. (Siegen U.) ; Maier, A. (Siegen U.) ; Ziolkowski, M. (Siegen U.) ; Biino, C. (INFN, Turin) ; Cartiglia, N. (INFN, Turin) ; Clemencic, M. (INFN, Turin) ; Goy Lopez, S. (INFN, Turin) ; Marchetto, F. (INFN, Turin) ; Menichetti, Ezio A. (INFN, Turin) ; Pastrone, N. (INFN, Turin) ; Wislicki, W. (Warsaw, Inst. Nucl. Studies) ; Dibon, H. (Vienna, OAW) ; Jeitler, M. (Vienna, OAW) ; Markytan, M. (Vienna, OAW) ; Neuhofer, G. (Vienna, OAW) ; Widhalm, L. (Vienna, OAW)

Published in: Phys.Lett.
Year: 2007
Vol.: B650
Page No: 1-8
Pages: 20

Abstract: The weak radiative decay Xi0 --> Lambda e+e- has been detected for the first time. We find 412 candidates in the signal region, with an estimated background of 15 +/- 5 events. We determine the branching fraction B(Xi0 --> Lambda e+e-) = [7.6 +/- 0.4(stat) +/- 0.4(syst) +/- 0.2(norm)] x 10^{-6}, consistent with an internal bremsstrahlung process, and the decay asymmetry parameter alpha_{XiLambdaee} = -0.8 +/- 0.2, consistent with that of Xi0 --> Lambda gamma. The charge conjugate reaction Xi0_bar --> Lambda_bar e+e- has also been observed.

Web-Page: http://pdglive.lbl.gov/REFERENCE_info1.brl?slacrpp=PHLTA,B650,1

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