Observation of an exotic baryon with S=+1 in photoproduction from the proton.
The reaction gamma p-->pi(+)K(-)K(+)n was studied at Jefferson Laboratory using a tagged photon beam with an energy range of 3-5.47 GeV. A narrow baryon state with strangeness S=+1 and mass M=1555+/-10 MeV/c(2) was observed in the nK(+) invariant mass spectrum. The peak's width is consistent with the CLAS resolution (FWHM=26 MeV/c(2)), and its statistical significance is (7.8+/-1.0)sigma. A baryon with positive strangeness has exotic structure and cannot be described in the framework of the naive constituent quark model. The mass of the observed state is consistent with the mass predicted by the chiral soliton model for the Theta(+) baryon. In addition, the pK(+) invariant mass distribution was analyzed in the reaction gamma p-->K(-)K(+)p with high statistics in search of doubly charged exotic baryon states. No resonance structures were found in this spectrum.
Kubarovsky
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V
Rensselaer Polytechnic Institute, Troy, New York 12180-3590, USA and Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA.
Guo
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Weygand
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Stoler
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Battaglieri
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DeVita
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Adams
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Li
Ji
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Nozar
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Salgado
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Ambrozewicz
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Anciant
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Anghinolfi
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Asavapibhop
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Audit
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Auger
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Avakian
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Bagdasaryan
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Ball
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Barrow
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Beard
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Bektasoglu
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Bellis
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Benmouna
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Berman
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Bianchi
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Biselli
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Boiarinov
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Bouchigny
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Bradford
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Branford
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Briscoe
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Brooks
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Burkert
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Butuceanu
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Calarco
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Carman
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Carnahan
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Cetina
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Chen
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Ciciani
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Cole
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Connelly
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Cords
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Corvisiero
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Crabb
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Crannell
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Cummings
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De Sanctis
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Degtyarenko
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Denizli
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Dennis
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Dharmawardane
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Djalali
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Dodge
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Doughty
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Dragovitsch
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Dugger
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Dytman
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Dzyubak
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Egiyan
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Egiyan
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Elouadrhiri
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Empl
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Eugenio
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Farhi
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Fatemi
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Feuerbach
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Ficenec
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Forest
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Frolov
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Funsten
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Gaff
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Garçon
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Gavalian
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Gilfoyle
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Giovanetti
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Girard
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Gothe
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Gordon
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Griffioen
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Guidal
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Guillo
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Gyurjyan
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Hadjidakis
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Hakobyan
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Hancock
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Hardie
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Heddle
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Heimberg
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Hersman
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Hicks
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Holtrop
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Hu
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Ilieva
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Ito
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Jenkins
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Joo
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Juengst
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Kelley
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Khandaker
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Kim
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Kim
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Kim
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Klein
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Klimenko
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Klusman
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Kossov
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Kramer
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Kuhn
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Kuhn
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Lachniet
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Laget
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Langheinrich
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Lawrence
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Longhi
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Lukashin
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Major
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Manak
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Marchand
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McAleer
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McNabb
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Mecking
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Mehrabyan
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Melone
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Mestayer
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Meyer
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Mikhailov
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Minehart
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Mirazita
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Miskimen
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Mokeev
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Morand
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Morrow
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Mozer
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Muccifora
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Mueller
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Mutchler
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Napolitano
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Nasseripour
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Nelson
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Niccolai
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Niculescu
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Niculescu
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Niczyporuk
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Niyazov
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O'Brien
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O'Rielly
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Opper
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Osipenko
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Park
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Pasyuk
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Peterson
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Philips
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Pivnyuk
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Pocanic
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Pogorelko
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Polli
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Pozdniakov
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Preedom
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Price
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Protopopescu
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Qin
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Raue
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Riccardi
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Ripani
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Ritchie
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Ronchetti
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Rossi
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Rowntree
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Rubin
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Sabourov
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Santoro
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Sargsyan
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Schumacher
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Serov
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Sharabian
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Shaw
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Simionatto
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Skabelin
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Smith
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Smith
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Smith
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Spraker
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Stavinsky
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Stepanyan
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Strakovsky
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Strauch
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Taiuti
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Taylor
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Tedeschi
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Thoma
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Thompson
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Todor
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Ungaro
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Vineyard
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Vlassov
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Wang
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Weinstein
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Weisberg
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Whisnant
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Wolin
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Wood
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Yegneswaran
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Yun
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