Evidence of the P$_{c\bar{c}s}$(4459)$^0$ in Upsilon(1S, 2S) inclusive decays at Belle

Le résumé fourni par la source

Using data samples of 102 million Upsilon(1S) events and 158 million Upsilon(2S) events collected by the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider, we search for [udsccbar] pentaquark states decaying to Jpsi Lambda. Using the first observations of Upsilon(1S, 2S) inclusive decays to Jpsi Lambda, we find evidence of the $P_{cc\bar{s}}(4459)^0$ state with a significance of 3.3 standard deviations, including statistical and systematic uncertainties. We measure the mass and width of the $P_{cc\bar{s}}(4459)^0$ to be (4471.7 +- 4.8 +- 0.6) MeV/c2 and (21.9 +- 13.1 +- 2.7) MeV, respectively. The branching fractions for $P_{cc\bar{s}}(4459)^0$ production are measured to be B[Upsilon(1S) -> $P_{cc\bar{s}}(4459)^0$/ Pbar_ccbars(4459)0 + anything] = (3.5 +- 2.0 +- 0.2)*10$^{-6}$ and B[Upsilin(2S) -> $P_{cc\bar{s}}(4459)^0$/ Pbar_ccbars(4459)0 +anything] = (2.9 +- 1.7 +- 0.4)*10$^{-6}$. The inclusive branching fractions of Upsilon(1S, 2S) -> Jpsi Lambda/Lambdabar are measured to be B[Upsilin(1S) -> Jpsi Lambda/Lambdabar + anything] = (36.9 +- 5.3 +- 2.4)*10-6 and B[Upsilon(2S) -> Jpsi Lambda/Lambdabar + anything] = (22.3 +- 5.7 +- 3.1)*10-6. We measure the visible cross section $\sigma(e^+e^- \to J/psi \Lambda/\bar\Lambda$ + anything) = (90 +- 14 +- 6) fb for the continuum production at $\sqrt{s} = 10.52$ GeV. In all cases, the first uncertainties are statistical and the second are systematic.

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