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Report No.

Observation of the "$$K^-pp$$"-like structure in the $$d(pi^+, K^+)$$ reaction at 1.69 GeV/$$c$$

Ichikawa, Yudai ; Hasegawa, Shoichi  ; Hosomi, Kenji ; Imai, Kenichi; Sako, Hiroyuki  ; Sato, Susumu ; Sugimura, Hitoshi; 37 of others*

We have observed a "$$K^-pp$$"-like structure in the $$d(pi^+,K^+)$$ reaction at 1.69 GeV/$$c$$. In this reaction a $$Lambda(1405)$$ hyperon resonance is expected to be produced as a doorway to form $$K^-pp$$ through the $$Lambda^*prightarrow K^-pp$$ process. However, most of the $$Lambda(1405)$$ produced would escape from the deuteron without secondary reactions. Therefore, coincidence of high-momentum ($$>$$ 250 MeV/$$c$$) proton(s)at large emission angles ($$39^circ<theta_{rm lab.}<122 circ$$) was requested to enhance the signal-to-background ratio. A broad enhancement in the proton coincidence spectra is observed around the missing mass of 2.27 GeV/$$c^2$$, which corresponds to the $$K^-pp$$ binding energy of 95 $$^{+18}_{-17}$$ (stat.) $$^{+30}_{-21}$$ (syst.) MeV and the width of 162 $$^{+87}_{-45}$$ (stat.) $$^{+66}_{-78}$$ (syst.) MeV.



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Category:Physics, Multidisciplinary



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