Ortho-positronium observation in the Double Chooz Experiment
Abstract
The Double Chooz experiment measures the neutrino mixing angle by detecting reactor via inverse beta decay. The positron-neutron space and time coincidence allows for a sizable background rejection, nonetheless liquid scintillator detectors would profit from a positron/electron discrimination, if feasible in large detector, to suppress the remaining background. Standard particle identification, based on particle dependent time profile of photon emission in liquid scintillator, can not be used given the identical mass of the two particles. However, the positron annihilation is sometimes delayed by the ortho-positronium (o-Ps) metastable state formation, which induces a pulse shape distortion that could be used for positron identification. In this paper we report on the first observation of positronium formation in a large liquid scintillator detector based on pulse shape analysis of single events. The o-Ps formation fraction and its lifetime were measured, finding the values of 44 12 (sys.) 5 (stat.) and ns 0.17ns (sys.) 0.15ns (stat.) respectively, in agreement with the results obtained with a dedicated positron annihilation lifetime spectroscopy setup.
Keywords
Cite
@article{arxiv.1407.6913,
title = {Ortho-positronium observation in the Double Chooz Experiment},
author = {Y. Abe and J. C. dos Anjos and J. C. Barriere and E. Baussan and I. Bekman and M. Bergevin and T. J. C. Bezerra and L. Bezrukov and E. Blucher and C. Buck and J. Busenitz and A. Cabrera and E. Caden and L. Camilleri and R. Carr and M. Cerrada and P. -J. Chang and E. Chauveau and P. Chimenti and A. P. Collin and E. Conover and J. M. Conrad and J. I. Crespo-Anadon and K. Crum and A. S. Cucoanes and E. Damon and J. V. Dawson and J. Dhooghe and D. Dietrich and Z. Djurcic and M. Dracos and M. Elnimr and A. Etenko and M. Fallot and F. von Feilitzsch and J. Felde and S. M. Fernandes and V. Fischer and D. Franco and M. Franke and H. Furuta and I. Gil-Botella and L. Giot and M. Goger-Neff and L. F. G. Gonzalez and L. Goodenough and M. C. Goodman and C. Grant and N. Haag and T. Hara and J. Haser and M. Hofmann and G. A. Horton-Smith and A. Hourlier and M. Ishitsuka and J. Jochum and C. Jollet and F. Kaether and L. N. Kalousis and Y. Kamyshkov and D. M. Kaplan and T. Kawasaki and E. Kemp and H. de Kerret and D. Kryn and M. Kuze and T. Lachenmaier and C. E. Lane and T. Lasserre and A. Letourneau and D. Lhuillier and H. P. Lima and M. Lindner and J. M. Lopez-Castano and J. M. LoSecco and B. Lubsandorzhiev and S. Lucht and J. Maeda and C. Mariani and J. Maricic and J. Martino and T. Matsubara and G. Mention and A. Meregaglia and T. Miletic and R. Milincic and A. Minotti and Y. Nagasaka and Y. Nikitenko and P. Novella and L. Oberauer and M. Obolensky and A. Onillon and A. Osborn and C. Palomares and I. M. Pepe and S. Perasso and P. Pfahler and A. Porta and G. Pronost and J. Reichenbacher and B. Reinhold and M. Rohling and R. Roncin and S. Roth and B. Rybolt and Y. Sakamoto and R. Santorelli and A. C. Schilithz and S. Schonert and S. Schoppmann and M. H. Shaevitz and R. Sharankova and S. Shimojima and D. Shrestha and V. Sibille and V. Sinev and M. Skorokhvatov and E. Smith and J. Spitz and A. Stahl and I. Stancu and L. F. F. Stokes and M. Strait and A. Stuken and F. Suekane and S. Sukhotin and T. Sumiyoshi and Y. Sun and R. Svoboda and K. Terao and A. Tonazzo and H. H. Trinh Thi and G. Valdiviesso and N. Vassilopoulos and C. Veyssiere and M. Vivier and S. Wagner and N. Walsh and H. Watanabe and C. Wiebusch and L. Winslow and M. Wurm and G. Yang and F. Yermia and V. Zimmer},
journal= {arXiv preprint arXiv:1407.6913},
year = {2014}
}
Comments
17 pages, 5 figures