COLLOQUIUM Teorico - Lunedì 10 Settembre 2018 ore 14:30 Dr Rajan Gupta "Lattice QCD calculations of the quark and gluon contributions to the proton spin"

Relatore: Dr Rajan Gupta - Los Alamos National Laboratory (NM, USA)

Esperto di studi non-perturbativi del settore del modello standard soggetto alla interazione forte

Luogo: sala Feynman

E-mail di riferimento: francesco.direnzo@unipr.it

Abstract:

The remarkable result, from the measurements of spin asymmetry in polarized

deep inelastic scattering by the EMC collaboration, that the sum of the

spins of the quarks contributes less than half of the total spin of the

proton lay down the challenge to explain this “proton spin crisis” from

QCD. I will show that calculations of the required matrix elements using

Lattice QCD are now in a position to provide first principle results with

all systematics under control and the steady reduction in the error budget.

The most well determined of the contributions is of the quark's intrinsic

spin. Existing lattice results will be reviewed and compared with current

phenomenological/experimental estimates.