SEZIONE DI FIRENZE
Proton is such a fundamental object for the nuclear physics and thus it has been intensely studied as the development of particle accelerators and the QCD, Believe it or not, it's basic properties such as neither charge radius nor the origin of its spin 1/2 have not been understood even today. In this seminar, I will introduce our challenge to explain the origin of its spin 1/2 from its constituents, i.e. quarks and gluons. Based on the conservation of angular momentum, the proton spin 1/2 is supposed to be composed by the sum of the quark spin, the gluon spin, and their angular momentum. Pioneering experiments of a high energy deep inelastic scattering revealed that the quark spin carries only 20 to 30% of proton spin in 1980s. The gluon spin contribution has been explored by high energy polarized proton and proton collision experiments at Brookhaven National Laboratory using the relativistic heavy ion collider (RHIC). After the accumulation of data over more than a decade, latest results indicate that the gluon spin carries somewhat similar fraction as the quark spin. Nowadays experimental challenges are rather focused to measure the angular momentum portion. The seminar covers the role of RHICf experiment on this observable. The RHICf experiment was executed in 2017 using the LHCf detector at RHIC. Left-right asymmetries of pi0 and neutron production were measured. (Prof. Itaru Nakagawa)

DATA: 26-11-2018