We have investigated neutron-proton (np) pairing in light nuclei (2p-1
f shell) using a specalized Hartree-Fock-Bogoliubov (HFB) method. For
the pairing interaction we used the constant Kisslinger-Sorensen inter
action and the realistic G-matrix obtained by solving the Bethe-Goldst
one equation with the Bonn one-boson-exchange potential. Our results s
how that there are at least two minima of the total energy correspondi
ng to two solutions of the HFB equation. The lower solution shows larg
e np pairing. This is confirmed by a recent empirical determination of
the np pairing gap, which turns out to be surprisingly large in agree
ment with our theoretical result. If one renormalizes the Brueckner re
action matrix elements of the Bonn potential by a factor g(np) multipl
ying the neutron-proton particle-particle matrix elements to reproduce
the experimental np gaps delta(np), one obtains large T = 1 np pairin
g. Preliminary results indicate that the np pairing increases even mor
e if particle-number projection is included. These effects are expecte
d to affect strongly the double-beta decay. The 2nu double-beta.decay
in Ca-48(20)28 --> Ti-48(22)26 is calculated. The Gamow-Teller matrix
elements are reduced remarkably by the large np pairing compared to th
e results without np pairing. The sensitivity of the 2nu double-beta d
ecay transition on the particle-particle force strength parameter g(pp
) is also reduced compared with the results without np pairing correla
tions.