Influence of DeltaT=3/2 terms on s- and p-shell contributions to the asymmetry parameter of Lambda p -> np decay

C. BARBERO

NUCLEAR PHYSICS A

Elsevier

Año: 2007 vol. 785 p. 339 - 350

0375-9474

Here is evaluated the effect of the Delta T= 3/2 isospin terms of weak interaction on the asymmetry parameter, a_Lambda, for proton induced nonmesonic hypernuclear weakdecay, Lambda p -> np. There has been used a general shell model formalism for finite hypernuclei recently developed. A strangeness-changing weak transition potential including the exchange of pseudoscalar mesons (pion, eta, K) is adopted. The effects of Delta T= 3/2 isospin changes have been included through an adequate modification of the weak coupling constants. A comparison with Delta T= 1/2 contribution is made for s and p-shell hypernuclei. It is analytically shown and numerically corroborated for ^{12}_{Lambda}C and ^5_{Lambda}He that Delta T= 3/2 terms affect approximately in the same percentage both s and p-shell contributions to proton asymmetry parameter. The value of this observable is increased in 4%. The effect of Delta T= 3/2 terms helps to enhance the asymmetry parameter value, but is not enough to reproduce the experimental data. The necessity of a similar detailed analysis including vector meson exchange is suggested.