Factorization of heavy-to-light form factors in soft-colline(10)

Heavy-to-light transition form factors at large recoil energy of the light meson have been conjectured to obey a factorization formula, where the set of form factors is reduced to a smaller number of universal form factors up to hard-scattering corrections

Thehard-collinearintegralsareidenticalastheyshouldbe,becausethetwointegralsdi eronlyatthesmallscaleλ4.Thecollinearcontributionisnowgivenby

′Ic= 1

2p′·l δ 1

0duπd/2 1 1

Itisverylikelythatwithmoreloops,moremodesofsuccessivelysmallervirtualitymustbeintroduced,withnolowerlimitonthevirtualityasthenumberofloopsincreases.3