The (Li-6,Li-6*[3.56 MeV]) reaction at 100 MeV/u as a probe of Gamow-Teller transition strengths in the inelastic scattering channel

C. Sullivan, R. G. T. Zegers*, S. Noji, Sam M. Austin, J. Schmitt, N. Aoi, D. Bazin, M. Carpenter, J. J. Carroll, H. Fujita, U. Garg, G. Gey, C. J. Guess, T. H. Hoang, M. N. Harakeh, E. Hudson, N. Ichige, E. Ideguchi, A. Inoue, J. IsaakC. Iwamoto, C. Kacir, T. Koike, N. Kobayashi, S. Lipschutz, M. Liu, P. von Neumann-Cosel, H. J. Ong, J. Pereira, M. Kumar Raju, A. Tamii, R. Titus, K. Werner, Y. Yamamoto, Y. D. Fang, J. C. Zamora, S. Zhu, X. Zhou

*Bijbehorende auteur voor dit werk

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Samenvatting

Background: Inelastic neutrino-nucleus scattering is important for understanding core-collapse supernovae and the detection of emitted neutrinos from such events in earth-based detectors. Direct measurement of the cross sections is difficult and has only been performed on a few nuclei. It is, therefore, important to develop indirect techniques from which the inelastic neutrino-nucleus scattering cross sections can be determined.

Purpose: This paper presents a development of the (Li-6,Li-6*[T = 1, T-z = 0, 0(+), 3.56 MeV]) reaction at 100 MeV/u as a probe for isolating the isovector spin-transfer response in the inelastic channel (Delta S = 1, Delta T = 1, Delta T-z = 0) from which the Gamow-Teller transition strengths from nuclei of relevance for inelastic neutrino-nucleus scattering cross sections can be extracted.

Method: By measuring the Li-6 ejectile in a magnetic spectrometer and selecting events in which the 3.56 MeV gamma ray from the decay of the Li-6*[3.56 MeV] state is detected, the isovector spin-transfer selectivity is obtained. High-purity germanium clover detectors served to detect the gamma rays. Doppler reconstruction was used to determine the gamma energy in the rest frame of Li-6. From the Li-6 and 3.56 MeV gamma-momentum vectors the excitation energy of the residual nucleus was determined.

Results: In the study of the C-12(Li-6,Li-6*[3.56 MeV]) reaction, the isovector spin-transfer excitation-energy spectrum in the inelastic channel was successfully measured. The strong Gamow-Teller state in C-12 at 15.1 MeV was observed. Comparisons with the analog C-12(Li-6,He-6) reaction validate the method of extracting the Gamow-Teller strength. In measurements of the Mg-24, Nb-93(Li-6,Li-6*[3.56 MeV]) reactions, the 3.56 MeV gamma peak could not be isolated from the strong background in the gamma spectrum from the decay of the isoscalar excitations. It is argued that by using a gamma-ray tracking array instead of a clover array, it is feasible to extend the mass range over which the (Li-6,Li-6*) reaction can be used for extracting the isovector spin-transfer response up to mass numbers of similar to 25 and perhaps higher.

Conclusions: It is demonstrated that the (Li-6,Li-6*[3.56 MeV]) reaction probe can be used to isolate the inelastic isovector spin-transfer response in nuclei. Application to nuclei with mass numbers of about 25 or more, however, will require a more efficient gamma-ray array with a better tracking capability.

Originele taal-2English
Artikelnummer015804
Aantal pagina's10
TijdschriftPhysical Review C
Volume98
Nummer van het tijdschrift1
DOI's
StatusPublished - 31-jul-2018

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