Large excesses of ^ { 44 } Ca in certain presolar graphite and silicon carbide grains give strong evidence for ^ { 44 } Ti production in supernovae .
Furthermore , recent detection of the ^ { 44 } Ti \gamma -line from the Cas A SNR by CGRO/COMPTEL shows that radioactive ^ { 44 } Ti is produced in supernovae .
These make the ^ { 44 } Ti abundance an observable diagnostic of supernovae .

Through use of a nuclear reaction network , we have systematically varied reaction rates and groups of reaction rates to experimentally identify those that govern ^ { 44 } Ti abundance in core-collapse supernova nucleosynthesis .
We survey the nuclear-rate dependence by repeated calculations of the identical adiabatic expansion , with peak temperature and density chosen to be 5.5 \times 10 ^ { 9 } K and 10 ^ { 7 } g cm ^ { -3 } , respectively , to approximate the conditions in detailed supernova models .
We find that , for equal total numbers of neutrons and protons ( \eta =0 ) , ^ { 44 } Ti production is most sensitive to the following reaction rates : ^ { 44 } Ti ( \alpha , p ) ^ { 47 } V , \alpha ( 2 \alpha , \gamma ) ^ { 12 } C , ^ { 44 } Ti ( \alpha , \gamma ) ^ { 48 } Cr , ^ { 45 } V ( p , \gamma ) ^ { 46 } Cr .
We tabulate the most sensitive reactions in order of their importance to the ^ { 44 } Ti production near the standard values of currently accepted cross-sections , at both reduced reaction rate ( 0.01 \times ) and at increased reaction rate ( 100 \times ) relative to their standard values .
Although most reactions retain their importance for \eta > 0 , that of ^ { 45 } V ( p , \gamma ) ^ { 46 } Cr drops rapidly for \eta \geq 0.0004 .
Other reactions assume greater significance at greater neutron excess : ^ { 12 } C ( \alpha , \gamma ) ^ { 16 } O , ^ { 40 } Ca ( \alpha , \gamma ) ^ { 44 } Ti , ^ { 27 } Al ( \alpha , n ) ^ { 30 } P , ^ { 30 } Si ( \alpha , n ) ^ { 33 } S. Because many of these rates are unknown experimentally , our results suggest the most important targets for future cross section measurements governing the value of this observable abundance .