Experimental study of thep+6Li→η+7Bereaction 11.3 MeV above threshold

Abstract

The cross section for the reaction p+ 6 Li → η+ 7 Be was measured at an excess energy of 11.28 MeV above threshold by detecting the recoiling 7 Be nuclei. A dedicated set of focal plane detectors was built for the magnetic spectrograph Big Karl and was used for identification and four momentum measurement of the 7 Be. A differential cross section of dσ dΩ = (0.69±0.20( stat.)±0.20( syst.)) nb/sr for the ground state plus the 1/2 − was measured. The result is compared to model calculations. 25.40.Ve, 25.90.+k

A Search for $\phi $ Meson Nucleus Bound State Using Antiproton Annihilation on Nucleus

“…η Li and 7 η Be Krusche has shown results for the γ 7 Li → η 7 Li reaction near threshold [17] and these complement earlier data taken on the p 6 Li → η 7 Be reaction [15,16]. It is important to note here that the structure of these A = 7 nuclei consists of a ground state doublet with orbital angular momentum L = 1 and another doublet with L = 3.…”

“…There have been measurements of the production of ηd [5], η 3 He [2, 3, 6-10], η 4 He [11][12][13][14], and η 7 Li/ 7 Be [15][16][17] systems near threshold. The most detailed dp → 3 He η data [9] show an enormous threshold enhancement corresponding to a very large η 3 He scattering length and a pole in the excess energy plane with |Q| < 1 MeV.…”

“…These are then split by a small spin-orbit term which, in the 7 Li case, gives levels with J P = 3/2 − , 1/2 − (0.48 MeV), 7/2 − (4.65 MeV), and 5/2 − (6.60 MeV). None of the three experiments had sufficient energy resolution to be sensitive to the splitting between the J P = 3/2 − and 1/2 − levels, though one of the p 6 Li → η 7 Be experiments [16] only measured particle-stable levels where E X < 2.47 MeV, i.e. the L = 1 doublet, and the shape of the missing-mass distribution in the photoproduction data allowed a degree of separation between the L = 1 and L = 3 excitations [17].…”

“…The p 6 Li → η 7 Be data were analysed in an αd and ατ cluster-model approach, using the dp → 3 He η data as input [27]. The good description of the two data sets [15,16] suggests that, if the energy allows it, the excitation of the L = 3 doublet will be stronger than that of the L = 1 doublet. Have we any idea what the situation is likely to be in the photoproduction case?…”

Search for quasi boundηmesons

“…Two experiments have been reported leading to the mirror nucleus 7 Be. The experiments were performed at SATURNE Saclay [123] and COSY Jülich [124]. Both studies employed the reaction He.…”