Indication of a Deeply Bound and CompactK−ppState Formed in thepp→pΛK+Reaction at 2.85 GeV

Abstract

We have analyzed data of the DISTO experiment on the exclusive pp --> pLambdaK+ reaction at 2.85 GeV to search for a strongly bound compact K- pp(approximately = X) state to be formed in the pp --> K+ + X reaction. The observed spectra of the K+ missing mass and the pLambda invariant-mass with high transverse momenta of p and K+ revealed a broad distinct peak of 26-sigma confidence with a mass M(X)=2267+/-3(stat)+/-5(syst) MeV/c2 and a width Gamma(X)=118+/-8(stat)+/-10(syst) MeV. The enormously large cross section indicates formation of a compact K- pp with a large binding energy of B(K)=103 MeV, which can be a possible gateway toward cold and dense kaonic nuclear matter.

Hadron physics at J-PARC

“…While we have observed many pairs of − p emitted in the back-to-back from the stopped K − absorption on 6 Li, 7 Li, and 12 C targets, the mass of the − p pairs was largely shifted suggesting a binding of the K − pp system as much as 115 MeV. A similar binding of about 105 MeV was also observed in an exclusive measurement in the p + p → K + + + p reaction at 2.85 GeV by the DISTO group [7].…”

New way to produce dense double-antikaonic dibaryon system, .YEN..YEN.bar{K}.YEN..YEN.bar{K}NN, through .LAMBDA.(1405)-doorway sticking in p + p collisions

“…Since the experimentally identified K − pp has a substantially deeper binding ( B K ∼ 105 MeV as compared with the originally predicted value of 48 MeV), 12) corresponding to a 25% enhanced 𝐾̄ N interaction, K − K − pp is likely to have a much larger binding energy than the originally predicted one. We thus presume that the binding energy can be 150 MeV or more.…”

“…12) A broad peak showing M = 2267 ± 2( stat ) ± 5( syst ) MeV/ c 2 was revealed with as much intensity as free Λ* emission, as shown in Fig. 1 (Upper).…”

Study of the elementary (K−, n) reactions to search for the K¯NN bound state via the 3He (K−, n) reaction at J-PARC

“…± 10(syst.) MeV, respectively [17]. Recently, the J-PARC E27 experiment measured the d (π + , K + ) X missing-mass spectrum, and reported a broad bump structure at the binding energy of 95±18(stat.)±30(syst.)…”