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Title: Toward precise Q{sub EC} values for the superallowed 0{sup +}->0{sup +} beta decays of T=2 nuclides: The masses of {sup 20}Na, {sup 24}Al, {sup 28}P, and {sup 32}Cl

Journal Article · · Physical Review. C, Nuclear Physics
 [1];  [2];  [2]; ; ; ; ; ; ;  [3]; ;  [4];  [5];  [1];  [5]
  1. Department of Physics, University of Washington, Seattle, Washington 98195 (United States)
  2. Wright Nuclear Structure Laboratory, Yale University, New Haven, Connecticut 06520 (United States)
  3. Physik Department E12, Technische Universitaet Muenchen, D-85748, Garching (Germany)
  4. Fakultaet fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, D-85784, Garching (Germany)
  5. Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1 (Canada)

High-precision measurements of superallowed 0{sup +}->0{sup +} beta decays of T=2 nuclides such as {sup 20}Mg, {sup 24}Si, {sup 28}S, and {sup 32}Ar can contribute to searches for physics beyond the standard model of particle physics if the Q{sub EC} values are accurate to a few keV or better. As a step toward providing precise Q{sub EC} values for these decays, the ground-state masses of the respective daughter nuclei {sup 20}Na, {sup 24}Al, {sup 28}P, and {sup 32}Cl have been determined by measuring the ({sup 3}He,t) reactions leading to them with the {sup 36}Ar({sup 3}He,t){sup 36}K reaction as a calibration. A quadrupole-dipole-dipole-dipole (Q3D) magnetic spectrograph was used together with thin ion-implanted carbon-foil targets of {sup 20}Ne, {sup 24}Mg, {sup 28}Si, {sup 32}S, and {sup 36}Ar. The masses of {sup 20}Na and {sup 32}Cl are found to be in good agreement with the values from the 2003 Atomic Mass Evaluation (AME03) [G. Audi, A. H. Wapstra, and C. Thibault, Nucl. Phys. A 729, 337 (2003)], and the precision has been improved by a factor of 6 in both cases. The masses of {sup 24}Al and {sup 28}P are found to be higher than the values from AME03 by 9.5 keV (3.2sigma) and 11.5 keV (3.6sigma), respectively, and the precision has been improved by a factor of 2.5 in both cases. The new {sup 32}Cl mass is used together with the excitation energy of its lowest T=2 level and the mass of {sup 32}Ar to derive an improved superallowed Q{sub EC} value of 6087.3(22) keV for this case. The effects on quantities related to standard-model tests including the beta-nu correlation coefficient a and the isospin-symmetry-breaking correction delta{sub C} are examined for the A=32 case.

OSTI ID:
21389068
Journal Information:
Physical Review. C, Nuclear Physics, Vol. 81, Issue 5; Other Information: DOI: 10.1103/PhysRevC.81.055503; (c) 2010 The American Physical Society; ISSN 0556-2813
Country of Publication:
United States
Language:
English

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