A. Rusek

Searching for the H-Dibaryon at Brookhaven

At the Brookhaven AGS several experiments are searching for the unique strangeness S = −2 H-dibaryon with the quark composition (uuddss). The E813/E836 collaboration, in particular, is using a high-intensity, separated 1.8 GeV/c K − beam and two different target configurations. In E836 the reaction K − + 3He→K + + H + n is used to search for a relatively deeply-bound H. Complementary to E836 the reactions K − + p → Ξ − + K +, followed by (Ξ −, d)atom → H + n are used to search near twice the A mass. The status of these two experiments is summarized, and other H-dibaryon searches are briefly reviewed.

H-dibaryon search via the (K-,K+) reaction using a diamond target (BNL-E885)

Abstract An experiment to study double-strangeness systems was performed at the BNL-AGS via the (K − ,K + ) reaction using a diamond target and scintillating fiber (SCIFI) blocks (E885). A search for the H dibaryon through the stopped Ξ − process is one of the objectives. The number of stopped Ξ − s is about 9,000, and the expected sensitivity of the H dibaryon search is more than one order of magnitude higher than that of the previous experiment at KEK-PS (E224).

Searches for the H-dibaryon at the AGS

A review is made of those past, present, and planned experiments at the AGS whose primary purpose is to determine whether the H‐dibaryon exists. Preliminary results are given for experiment E813, based on partially‐completed analysis.

GAMMA SPECTROSCOPY OF P-SHELL HYPERNUCLEI AND ΛN SPIN-DEPENDENT INTERACTIONS-REPORT OF BNL E930

High resolution γ spectroscopy of hypernuclei using Hyperball has revealed detailed level structure of several p-shell Λ hypernuclei and allowed us to extract the strengths of ΛN spin-dependent interactions. In the experiment BNL E930, we observed E2(3/2+, 5/2+ → 1/2+) transitions in and confirmed a small size of the Λ-spin-dependent spin-orbit force. Recently we took data for and in order to investigate the strength of the ΛN tensor force. In a preliminary analysis, we observed γ rays of and .

Evidence of Xi hypernuclear production in the C-12(K-,K+)(Xi)Be-12 reaction

The E885 collaboration utilized the 1.8 GeV/c K^- beam line at the AGS to accumulate 3 x 10^5 (K^-,K^+) events. Xi hypernuclear states are expected to be produced through the reaction K^- + ^{12}C -> K^+ + ^{12}_{Xi}Be. The measured missing-mass spectrum indicates the existence of a signal below the threshold for free Xi production. Although the resolution was not sufficient to resolve discrete hypernuclear states, the excess of events in the region of missing mass, kinematically inaccessible in free Xi production, is compared to theoretical prediction for ^{12}_{Xi}Be production.

H-dibaryon search via the (K-,K+) reaction using a diamond target

Abstract An experiment to study double-strangeness systems was performed at the BNL-AGS via the (K − ,K + ) reaction using a diamond target and scintillating fiber (SCIFI) blocks (E885). A search for the H dibaryon through the stopped Ξ − process is one of the objectives. The number of stopped Ξ − s is about 9,000, and the expected sensitivity of the H dibaryon search is more than one order of magnitude higher than that of the previous experiment at KEK-PS (E224).

Search for strangelets and other rare objects in Au + Pt collisions at the AGS using a fixed-angle focusing spectrometer

Abstract During the 1993 AGS heavy ion run, experiment E886 conducted a strangelet search in Au + Pt reactions, with beam momentum of 10.8 GeV/c per nucleon. Presented here are the upper limit for strangelet production, invariant cross sections for p, t, d 3 He, 4 He, 6 He, 8 He, 6 Li, 7 Li, 8 Li and 7 Be, along with a demonstration of their agreement with a coalescence model fit to data collected by E886 during the 1992 engineering run, and upper limits for production cross sections for other rare objects, such as (H dibaryon)-nucleus systems. All results reported here are preliminary.