L.C. Bland

Indication of a deeply bound and compact K- pp state formed in the pp- -> pLambdaK+ reaction at 2.85 GeV.

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.

Production of η' mesons in the pp→ppη' reaction at 3.67 GeV/c

Abstract The ratio of the total exclusive production cross sections for η and η mesons has been measured in the pp reaction at p beam =3.67xa0GeV/ c . The observed η ′ / η ratio is (0.83±0.11 +0.23 −0.18 )×10 −2 from which the exclusive η ′ meson production cross section is determined to be (1.12±0.15 +0.42 −0.31 )xa0μb. Differential cross section distributions have been measured. Their shape is consistent with isotropic η ′ meson production.

K- meson production in the proton proton reaction at 3.67-GeV/c

Abstract The total cross section of the reaction pp→ppK+K− has been determined for proton–proton reactions with p beam =3.67 GeV /c . This represents the first cross section measurement of the pp→ppK−K+ channel near threshold, and is equivalent to the inclusive pp→ppK−X cross section at this beam momentum. The cross section determined at this beam momentum is about a factor 20 lower than that for inclusive pp→ppK+X meson production at the same CM energy above the corresponding threshold. This large difference in the K+ and K− meson inclusive production cross sections in proton-proton reactions is in strong contrast to cross sections measured in sub-threshold heavy ion collisions, which are similar in magnitude at the same energy per nucleon below the respective thresholds.

First exclusive measurements of the K − pp state populated in the pp → K + Λp reaction at 2.85 GeV

We have analyzed data of the DISTO experiment on the exclusive pp → Ku2009+u2009 Λp process at Tpu2009=u20092.85xa0GeV to search for a Ku2009−u2009pp xa0(u2009≡u2009X) nuclear bound state to be formed in the pp → Ku2009+u2009u2009+u2009X reaction. The deviation spectra of the Ku2009+u2009 missing-mass ΔM (Ku2009+u2009) and Λp invariant-mass M(Λp) with selection of large-angle proton emission revealed a structure with MXu2009=u20092265 ±2xa0MeV/c2 and ΓXu2009=u2009118 ±8xa0MeV.

Spin observables in hyperon production

4(DISTO Collaboration) * The first exclusive measurements of the spin transfer parameter DN N in the reaction fJp -t p[{+Ahas been performed at Saturne with the polarized beam and with the DISTO spectrometer. The results suggest an OBE mechanism dominated by kaon exchange.

Quasifree inclusive and exclusive cross sections at 200 MeV

Abstract Cross section measurements for both inclusive (p,p′) and exclusive (p,2p) and (p,np) quasifree scattering at 200 MeV from 2 H and 12 C have been completed from 27° to 34°. Inter-comparisons of these inclusive and exclusive data are employed to determine the contribution of single-step NN scattering to the inclusive scattering yield. This determination is crucial to address whether the inclusive yield arises primarily from these simple hard scattering processes, as is tacitly assumed in most theoretical calculations of this process, or whether non-negligible contributions from more complicated reaction dynamics are present. These data are also employed to study the effect of the nuclear medium on the underlying NN interaction and to show that there is no strong evidence for collectivity in the nuclear response at 200 MeV.

Study of continuum nuclear structure of 12C via (p, p′X) at intermediate energies☆

The inclusive 12 C(p, p ) and exclusive 12 C(p, pX) reactions have been studied with a beam energy of 156 MeV and for X = p and α. The study focuses on the (p, pX) reaction mechanism and on the structure of 12 C just above the particle-emission threshold, 14 ≤ Ex ≤ 28 MeV. Cross sections were simultaneously measured for all three reactions. The exclusive data were analyzed by making multiple-peak fits of the spectra and by Legendre-polynomial fits of the angular correlations. Multiple- peak fits were also made of the inclusive spectra. The resultant cross sections were compared to theoretical calculations. An analysis of the results shows that this region of Ex consists predominantly of resonant excitations, in contradiction to the findings of previous analyses.

Development of a tagged neutron facility for neutron scattering experiments at intermediate energies

We describe the ongoing development of a tagged neutron facility at the Indiana University Cooler. The neutrons are produced via the interaction of a stored 200 MeV proton beam with a deuterium gas jet target. Energy and position measurements of the two l

The 4He(p, n)4Li∗ reaction at 100 and 200 MeV: Implications for the mass-four system and for astrophysics

Double-differential cross sections, d2σ(dΩdEx), for the inclusive 4He(p, n) reaction were measured at 100 and 200 MeV. The data contradict previous evidence for narrow states in 4Li and are in qualitative agreement with predictions using continuum shell model wave functions. These data are needed to constrain models of neutron production in solar flares and in the atmospheres of accreting neutron stars.

Quasifree (p↘,Np) reaction studies at 200 MeV

The quasifree knock‐out reaction, (p↘,Np) has been studies on 2H and 12C targets at the proton energy of 200 MeV at the Indiana University Cyclotron Facility. Differential cross sections and analyzing powers are presented along with plane and distorted wave impulse approximation calculations. (AIP)