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Rensselaer Polytechnic Institute, Troy, New York 12180-3590, USA.
Phys Rev Lett. 2006 Sep 8;97(10):102001. doi: 10.1103/PhysRevLett.97.102001. Epub 2006 Sep 7.
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.
利用标记光子束在杰斐逊实验室对反应γp→pK⁺K⁻进行了研究，光子能量范围为1.8至3.8 GeV。目的是在pK⁺不变质量谱中寻找Θ⁺⁺五夸克，这是一种窄的、双重带电的重子态，奇异数S = +1，同位旋I = 1。未发现具有统计显著性的Θ⁺⁺证据。在1.5至2.0 GeV/c²的质量范围内获得了反应γp→K⁻Θ⁺⁺的总截面和微分截面的上限，对于质量M(Θ⁺⁺) = 1.54 GeV/c²的窄共振，其上限约为0.15 nb，置信水平为95%。该结果对Θ⁺⁺的宽度Γ(Θ⁺⁺) < 0.1 MeV/c²给出了严格的上限。
