Evidence for a Kaon-Bound StateK−ppProduced inK−Absorption Reactions at Rest

Abstract

We have searched for a deeply bound kaonic state by using the FINUDA spectrometer installed at the e(+)e(-) collider DAPhiNE. Almost monochromatic K(-)'s produced through the decay of phi(1020) mesons are used to observe K(-) absorption reactions stopped on very thin nuclear targets. Taking this unique advantage, we have succeeded to detect a kaon-bound state K(-)pp through its two-body decay into a Lambda hyperon and a proton. The binding energy and the decay width are determined from the invariant-mass distribution as 115(+6)(-5)(stat)(+3)(-4)(syst) MeV and 67(+14)(-11)(stat)(+2)(-3)(syst) MeV, respectively.

Determination of the real part of theη′-Nb optical potential

“…The possible existence of compact K − pp clusters was proposed by Yamazaki and Akaishi [11] and has attracted a lot of attention experimentally and theoretically. Following first claims of observing kaonic clusters [12,13] conflicting results have been reported and the existence of such states discussed controversially (see recent publications [14][15][16] and references cited therein). The binding energy of these states may not be very large and they may have a rather large width which makes it difficult to detect them experimentally.…”

Search for Deeply Bound Kaonic Nuclear States in the AMADEUS Experiment

“…However, an F-Test was carried out to compare the two models (with and without a K − pp bound state) results in a 1σ significance for the best fit which does not allow to claim the observation of a bound state. Similar measurements have been carried out and re [9,20]. In [9] stopped K − in a 4 He target have been consid the integrated contribution to the final state 0 ( ) wit emission was extracted and found to be equal to 0.11 per stopped K − .…”

“…The data in [20] show the measurement of th nal state from a 13 Similar measurements have been carried out and rep [9,20]. In [9] stopped K − in a 4 He target have been consid the integrated contribution to the final state 0 ( ) with emission was extracted and found to be equal to 0.117 per stopped K − . This large number is due to the conta in the sample and to the fact that absorptions on p-n p included.…”

“…The position of the Λ(1405) reflects the strength of theKN interaction, thus influencing the possible formation of K multi-nucleon bound states. Accordingly, recent theoretical calculations, based on different approaches, deliver a wide range of bindings and widths for the di-baryonic kaonic bound state ppK − [2][3][4][5][6][7], while the experimental results are contradictory [8][9][10][11][12][13][14]. Moreover, the extraction of a ppK − signal in K − absorption experiments is strongly affected by the yield and the shape of the competing K − multi-nucleon absorption processes.…”

$\Lambda-p/d/t$ correlations with the KLOE Drift Chamber by the AMADEUS collaboration

“…Until now several experiments presented their results, but the interpretation is not conclusive, so the puzzle remains unsolved. Two main experimental approaches have been used in the search for K − pp clusters: p-p and heavy ion collisions, as, for example, in the DISTO experiment [8] and a low momentum or stopped K − interactions in light nuclei, as in the FINUDA [9] and KEK-PS E549 [10] experiments. The second approach is used also in our experiment.…”