A summary is given of the present status (November 1997) of recent and ongoing experimental H-dibaryon searches at the Brookhaven AGS and at KEK. Since other papers at this conference discuss heavy ...ion-induced H production, this summary is restricted to experiments using kaons or protons as projectiles. Included are direct searches either via H production or via detection of H-decay products. The latest experiments searching for
S = −2 hypernuclei, with their indirect implications on the existence of the H, are also mentioned. Several experimental results have recently been published, and these results make the existence of a deeply-bound H appear very unlikely.
A search for lepton flavor violating decays, K+ --> mu+ mu+ pi-, K+ --> e+ e+ pi-, K+ --> pi+ e+ mu-, K+ --> mu+ e+ pi-, and pi0 --> e+ mu-, was performed using the data collected in Experiment E865 ...at the Brookhaven Alternating Gradient Synchrotron. No signal was found in any of the decay modes. At the 90% confidence level, the branching ratios are less than 3.0x10(-9), 6.4x10(-10), 5. 2x10(-10), 5.0x10(-10), and 3.4x10(-9), respectively.
We have developed a GEM-TPC for H-dibaryon search at J-PARC E42, which reconstructs charged particles from the H-dibaryon decay in (K super(-), K super(+)) reaction. Since 10 super(6) cps/cm super(2) ...K super(-) beams are injected to the TPC, GEMs and a gating grid are adopted to suppress positive ion feedback. The TPC is also designed to have good position resolutions corresponding to the LambdaLambda invariant mass resolution of a few MeV/c super(2). The design of the E42 TPC, and performance evaluations of a prototype TPC are described.
The analyzing power for proton-carbon elastic scattering in the Coulomb-nuclear interference region of momentum transfer, 9.0x10(-3)<-t<4.1x10(-2) (GeV/c)(2), was measured with a 21.7 GeV/c polarized ...proton beam at the Alternating Gradient Synchrotron of Brookhaven National Laboratory. The ratio of hadronic spin-flip to nonflip amplitude, r(5), was obtained from the analyzing power to be Rer(5)=0.088+/-0.058 and Imr(5)=-0.161+/-0.226.
The PHENIX collaboration presents first measurements of low-momentum (0.4<p_{T}<3 GeV/c) direct-photon yields from Au+Au collisions at sqrts_{NN}=39 and 62.4 GeV. For both beam energies the ...direct-photon yields are substantially enhanced with respect to expectations from prompt processes, similar to the yields observed in Au+Au collisions at sqrts_{NN}=200. Analyzing the photon yield as a function of the experimental observable dN_{ch}/dη reveals that the low-momentum (>1 GeV/c) direct-photon yield dN_{γ}^{dir}/dη is a smooth function of dN_{ch}/dη and can be well described as proportional to (dN_{ch}/dη)^{α} with α≈1.25. This scaling behavior holds for a wide range of beam energies at the Relativistic Heavy Ion Collider and the Large Hadron Collider, for centrality selected samples, as well as for different A+A collision systems. At a given beam energy, the scaling also holds for high p_{T} (>5 GeV/c), but when results from different collision energies are compared, an additional sqrts_{NN}-dependent multiplicative factor is needed to describe the integrated-direct-photon yield.
A hyperon–nucleon scattering experiment, KEK-PS E289, was carried out at the K2 beam line in KEK. We adopted a scintillating fiber active target as a hydrogen target for hyperon production and ...subsequent hyperon–nucleon scattering. We collected more data than in a previous experiment, KEK-PS E251. In this paper, the differential cross sections for
Σ
+
p
elastic scattering in the incident momentum range from 350 to 750 MeV/
c are presented and compared with theoretical predictions from the Nijmegen group (Nijmegen Soft Core 97) and the Kyoto–Niigata group (RGM-FSS and fss2).
Extensive experimental data from high-energy nucleus-nucleus collisions were recorded using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The comprehensive set of measurements ...from the first three years of RHIC operation includes charged particle multiplicities, transverse energy, yield ratios and spectra of identified hadrons in a wide range of transverse momenta (
p
T
), elliptic flow, two-particle correlations, nonstatistical fluctuations, and suppression of particle production at high
p
T
. The results are examined with an emphasis on implications for the formation of a new state of dense matter. We find that the state of matter created at RHIC cannot be described in terms of ordinary color neutral hadrons.
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