The ^ { 40 } Ca ( \alpha , \gamma ) ^ { 44 } Ti reaction is believed to be the main production channel for the radioactive nuclide ^ { 44 } Ti in core-collapse supernovae .
Radiation from decaying ^ { 44 } Ti has been observed so far for two supernova remnants , and a precise knowledge of the ^ { 44 } Ti production rate may help improve supernova models .
The ^ { 40 } Ca ( \alpha , \gamma ) ^ { 44 } Ti astrophysical reaction rate is determined by a number of narrow resonances .
Here , the resonance triplet at E _ { \alpha } = 4497 , 4510 , and 4523 keV is studied both by activation , using an underground laboratory for the \gamma counting , and by in-beam \gamma spectrometry .
The target properties are determined by elastic recoil detection analysis and by nuclear reactions .
The strengths of the three resonances are determined to \omega \gamma = ( 0.92 \pm 0.20 ) , ( 6.2 \pm 0.5 ) , and ( 1.32 \pm 0.24 ) eV , respectively , a factor of two more precise than before .
The strengths of this resonance triplet may be used in future works as a point of reference .
In addition , the present new data directly affect the astrophysical reaction rate at relatively high temperatures , above 3.5 GK .