The reaction gammap --> pK+K- was studied at Jefferson Lab with photon energies from 1.8 to 3.8 GeV using a tagged photon beam. The goal was to search for a Theta++ pentaquark, a narrow, doubly charged baryon state having strangeness S=+1 and isospin I=1, in the pK+ invariant mass spectrum. No statistically significant evidence of a Theta++ was found. Upper limits on the total and differential cross section for the reaction gammap --> K-Theta++ were obtained in the mass range from 1.5 to 2.0 GeV/c2, with an upper limit for a narrow resonance with a mass M(Theta++) = 1.54 GeV/c2 of about 0.15 nb, 95% C.L.. This result places a stringent upper limit on the Theta++ width Gamma(Theta++) <0.1 MeV/c2.

Kubarovsky, V

Battaglieri, M

De Vita, R

Goett, J

Guo, L

Mutchler, GS

Stoler, P

Weygand, DP

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Niculescu, I

Niczyporuk, BB

Niroula, MR

Niyazov, RA

Nozar, M

Osipenko, M

Ostrovidov, AI

Park, K

Pasyuk, E

Paterson, C

Pierce, J

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Pozdniakov, S

Price, JW

Prok, Y

Protopopescu, D

Raue, BA

Riccardi, G

Ricco, G

Ripani, M

Ritchie, BG

Ronchetti, F

Rosner, G

Rossi, P

Sabatié, F

Salgado, C

Santoro, JP

Sapunenko, V

Schumacher, RA

Serov, VS

Sharabian, YG

Shvedunov, NV

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Smith, LC

Sober, DI

Stavinsky, A

Stepanyan, SS

Stepanyan, S

Stokes, BE

Strakovsky, II

Strauch, S

Taiuti, M

Tedeschi, DJ

Teymurazyan, A

Thoma, U

Tkabladze, A

Tkachenko, S

Todor, L

Tur, C

Ungaro, M

Vineyard, MF

Vlassov, AV

Weinstein, LB

Williams, M

Wolin, E

Wood, MH

Yegneswaran, A

Zana, L

Zhang, J

Zhao, B

CLAS Collaboration

published 

September 8, 2006

General Physics

Physical Review Letters  Journal