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Register a new userStudy of proton capture resonant state of ^{15}O at 7556 keV
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The slowest reaction in the CNO cycle 14N(p, gamma)15O has been studied by populating the E^lab_p =278 keV (E^r_c.m.=259 keV) proton capture resonant state of ^{15}O at 7556 keV. The strength of the resonance has been determined from the experimental data. The level lifetime of the sub-threshold resonant state at Ex=6792 keV, as well as the lifetimes of the 5181 keV and 6172 keV states, have been measured using the Doppler shift attenuation method (DSAM). The structural properties of the nucleus ^{15}O, such as, the level energies, transition strengths, level lifetimes, and spectroscopic factors, have been calculated theoretically by using the large basis shell model, which agrees reasonably well with the present as well as the previous experimental data.
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We report on a new measurement of $^{14}$N(p,$gamma$)$^{15}$O for the ground state capture transition at $E_p$ = 360, 380 and 400 keV, using the 400 kV LUNA accelerator. The true coincidence summing effect --the major source of error in the ground state capture determination-- has been significantly reduced by using a Clover--type gamma detector.
This paper reports results from a study of the reaction pp->pK0Sigma+ at beam momenta of p_{beam} = 2950, 3059, and 3200 MeV/c (excess energies of epsilon= 126, 161, and 206 MeV). Total cross sections were determined for all energies; a set of differential cross sections (Dalitz plots; invariant mass spectra of all two-body subsystems; angular distributions of all final state particles; distributions in helicity and Jackson frames) are presented for epsilon= 161 MeV. The total cross sections are proportional to the volume of available three-body phase-space indicating that the transition matrix element does not change significantly in this range of excess energies. It is concluded from the differential data that the reaction proceeds dominantly via the N(1710)P_{11} and/or N(1720)P_{13} resonance(s); N(1650)S_{11} and Delta(1600)P_{33} could also contribute.
Bound-systems of $Xi^-$--$^{14}_{}{rm N}$ are studied via $Xi^-$ capture at rest followed by emission of a twin single-$Lambda$ hypernucleus in the emulsion detectors. Two events forming extremely deep $Xi^-$ bound states were obtained by analysis of a hybrid method in the E07 experiment at J-PARC and reanalysis of the E373 experiment at KEK-PS. The decay mode of one event was assigned as $Xi^-+^{14}_{}{rm N}to^{5}_{Lambda}{rm He}$+$^{5}_{Lambda}{rm He}$+$^{4}_{}{rm He}$+n. Since there are no excited states for daughter particles, the binding energy of the $Xi^-$ hyperon, $B_{Xi^-}$, in $^{14}_{}{rm N}$ nucleus was uniquely determined to be 6.27 $pm$ 0.27 MeV. Another $Xi^-$--$^{14}_{}{rm N}$ system via the decay $^{9}_{Lambda}{rm Be}$ + $^{5}_{Lambda}{rm He}$ + n brings a $B_{Xi^-}$ value, 8.00 $pm$ 0.77 MeV or 4.96 $pm$ 0.77 MeV, where the two possible values of $B_{Xi^-}$ correspond to the ground and the excited states of the daughter $^{9}_{Lambda}{rm Be}$ nucleus, respectively. Because the $B_{Xi^-}$ values are larger than those of the previously reported events (KISO and IBUKI), which are both interpreted as the nuclear $1p$ state of the $Xi^-$--$^{14}_{}{rm N}$ system, these new events give the first indication of the nuclear $1s$ state of the $Xi$ hypernucleus, $^{15}_{Xi}{rm C}$.
Differential and total cross sections for the pp -> ppK+K- reaction have been measured at a proton beam energy of 2.83 GeV using the COSY-ANKE magnetic spectrometer. Detailed model descriptions fitted to a variety of one-dimensional distributions permit the separation of the pp -> pp phi cross section from that of non-phi production. The differential spectra show that higher partial waves represent the majority of the pp -> pp phi total cross section at an excess energy of 76 MeV, whose energy dependence would then seem to require some s-wave phi-p enhancement near threshold. The non-phi data can be described in terms of the combined effects of two-body final state interactions using the same effective scattering parameters determined from lower energy data.
The differential cross section for proton-proton elastic scattering has been measured at a beam energy of 1.0 GeV and in 200 MeV steps from 1.6 to 2.8 GeV for centre-of-mass angles in the range from 12-16 degrees to 25-30 degrees, depending on the energy. Absolute normalisations of typically 3% were achieved by studying the energy losses of the circulating beam of the COSY storage ring as it passed repeatedly through the windowless hydrogen target of the ANKE magnetic spectrometer. It is shown that the data have a significant impact upon a partial wave analysis. After extrapolating the differential cross sections to the forward direction, the results are broadly compatible with the predictions of forward dispersion relations.
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