Nuclear Physics Experiments with Ion Storage Rings

In the last two decades a number of nuclear structure and astrophysics experiments were performed at heavy-ion storage rings employing unique experimental conditions offered by such machines. Furthermore, building on the experience gained at the two facilities presently in operation, several new storage ring projects were launched worldwide. This contribution is intended to provide a brief review of the fast growing field of nuclear structure and astrophysics research at storage rings.Comment: XVIth International Conference on Electro-Magnetic Isotope Separators and Techniques Related to their Applications, December 2--7, 2012 at Matsue, Japa

Schottky mass measurements of heavy neutron-rich nuclides in the element range 70\leZ \le79 at the ESR

Storage-ring mass spectrometry was applied to neutron-rich $^{197}$Au projectile fragments. Masses of $^{181,183}$Lu, $^{185,186}$Hf, $^{187,188}$Ta, $^{191}$W, and $^{192,193}$Re nuclei were measured for the first time. The uncertainty of previously known masses of $^{189,190}$W and $^{195}$Os nuclei was improved. Observed irregularities on the smooth two-neutron separation energies for Hf and W isotopes are linked to the collectivity phenomena in the corresponding nuclei.Comment: 10 pages, 9 figures, 2 table

High-resolution measurement of the time-modulated orbital electron capture and of the β+\beta^+ decay of hydrogen-like 142^{142}Pm60+^{60+} ions

The periodic time modulations, found recently in the two-body orbital electron-capture (EC) decay of both, hydrogen-like $^{140}$Pr$^{58+}$ and $^{142}$Pm$^{60+}$ ions, with periods near to 7s and amplitudes of about 20%, were re-investigated for the case of $^{142}$Pm$^{60+}$ by using a 245 MHz resonator cavity with a much improved sensitivity and time resolution. We observed that the exponential EC decay is modulated with a period $T = 7.11(11)$s, in accordance with a modulation period $T = 7.12(11)$ s as obtained from simultaneous observations with a capacitive pick-up, employed also in the previous experiments. The modulation amplitudes amount to $a_R = 0.107(24)$ and $a_P = 0.134(27)$ for the 245 MHz resonator and the capacitive pick-up, respectively. These new results corroborate for both detectors {\it exactly} our previous findings of modulation periods near to 7s, though with {\it distinctly smaller} amplitudes. Also the three-body $\beta^+$ decays have been analyzed. For a supposed modulation period near to 7s we found an amplitude $a = 0.027(27)$, compatible with $a = 0$ and in agreement with the preliminary result $a = 0.030(30)$ of our previous experiment. These observations could point at weak interaction as origin of the observed 7s-modulation of the EC decay. Furthermore, the data suggest that interference terms occur in the two-body EC decay, although the neutrinos are not directly observed.Comment: In memoriam of Prof. Paul Kienle, 9 pages, 1 table, 5 figures Phys. Lett. B (2013) onlin

Approaching the Gamow Window with Stored Ions : Direct Measurement of Xe 124 (p,γ) in the ESR Storage Ring

© 2019 American Physical Society. All rights reserved.We report the first measurement of low-energy proton-capture cross sections of Xe124 in a heavy-ion storage ring. Xe12454+ ions of five different beam energies between 5.5 and 8 AMeV were stored to collide with a windowless hydrogen target. The Cs125 reaction products were directly detected. The interaction energies are located on the high energy tail of the Gamow window for hot, explosive scenarios such as supernovae and x-ray binaries. The results serve as an important test of predicted astrophysical reaction rates in this mass range. Good agreement in the prediction of the astrophysically important proton width at low energy is found, with only a 30% difference between measurement and theory. Larger deviations are found above the neutron emission threshold, where also neutron and γ widths significantly impact the cross sections. The newly established experimental method is a very powerful tool to investigate nuclear reactions on rare ion beams at low center-of-mass energies.Peer reviewedFinal Published versio

Partial-wave analysis of the eta pi+ pi- system produced in the reaction pi-p --> eta pi+ pi- n at 18 GeV/c

A partial-wave analysis of 9082 eta pi+ pi- n events produced in the reaction pi- p --> eta pi+ pi- n at 18.3 GeV/c has been carried out using data from experiment 852 at Brookhaven National Laboratory. The data are dominated by J^{PC} = 0^{-+} partial waves consistent with observation of the eta(1295) and the eta(1440). The mass and width of the eta(1295) were determined to be 1282 +- 5 MeV and 66 +- 13 Mev respectively while the eta(1440) was observed with a mass of 1404 +- 6 MeV and width of 80 +- 21 MeV. Other partial waves of importance include the 1++ and the 1+- waves. Results of the partial wave analysis are combined with results of other experiments to estimate f1(1285) branching fractions. These values are considerably different from current values determined without the aid of amplitude analyses.Comment: 22 pages, 8 figure

A partial wave analysis of the π0π0\pi ^0\pi ^0 system produced in π−p\pi ^-p charge exchange collisions

A partial wave analysis of the of the $\pi ^0\pi ^0$ system produced in the charge exchange reaction: $\pi ^-p\to \pi ^0\pi ^0n$ at an incident momentum of $18.3 GeV/c$ is presented as a function of ${\pi ^0\pi ^0}$ invariant mass, $m_{\pi^0\pi^0}$, and momentum transfer squared, $| {t} |$, from the incident $\pi^-$ to the outgoing ${\pi ^0\pi ^0}$ system.Comment: 24 pages total,8 pages text, 14 figures, 1 table. Submitted to Phys Rev

Evidence for Exotic J^{PC}=1^{-+} Meson Production in the Reaction pi- p --> eta pi- p at 18 GeV/c

Details of the analysis of the eta pi- system studied in the reaction pi^{-} p --> eta pi^{-} p at 18 GeV/c are given. Separate analyses for the 2 gamma and pi+ pi- pi0 decay modes of the eta are presented. An amplitude analysis of the data indicates the presence of interference between the a(2)(1320)- and a J^{PC}=1^{-+} wave between 1.2 and 1.6 GeV/c^2. The phase difference between these waves shows phase motion not attributable solely to the a(2)(1320)-. The data can be fitted by interference between the a(2)(1320)- and an exotic 1^{-+} resonance with M = 1370 +-16 +50 -30} MeV/c^2 and Gamma = 385 +- 40 +65 -105 MeV/c^2. Our results are compared with those of other experiments.Comment: 50 pages of text and 34 figure

Measurement of hadronic shower punchthrough in magnetic field

The total punchthrough probability of showers produced by negative pions, positive pions, positive kaons and protons, has been measured as a function of depth in an absorber in a magnetic field ranging from 0 to 3 Tesla. The incident particle momentum varied from 10 to 300 GeV/c. The lateral shower development and particle multiplicity at several absorber depths have been determined. The measurements are compared with the predictions of Monte Carlo simulation programs