http://physicsworld.com/cws/article/news/2014/jul/11/gluons-get-in-on-proton-spin
Gluons get in on proton spin New research shows that gluons carry most of the protons spin <snip> In the latest work, a group of theorists – Daniel de Florian <http://users.df.uba.ar/deflo/deflo/main.html>, from the Aires University in Argentina, and colleagues – analysed several years' worth of collision data from RHIC's STAR and PHENIX experiments. De Florian and colleagues have now studied data collected up until 2009, and have compared those data with a theoretical model they have developed that predicts the likely spin direction of gluons carrying a certain fraction of the momentum involved in the proton collisions. The researchers discovered, in contrast to a null result they obtained using fewer data five years ago, that gluon spin does tend to line up with that of the protons, rather than against it. In fact, they estimate that gluons could supply as much as half of a proton's spin. "This is the first evidence that suggests gluons could make a significant contribution to proton spin," says team member Werner Vogelsang <http://www.tphys.physik.uni-tuebingen.de/~vogelsang/Welcome.html> of Tübingen University in Germany, who adds that, on theoretical grounds, gluons ought to supply the same amount of spin to neutrons. On Sat, Aug 9, 2014 at 9:06 PM, Eric Walker <[email protected]> wrote: > On Sat, Aug 9, 2014 at 4:11 PM, Axil Axil <[email protected]> wrote: > > ... the proton which will then constitute a normal proton again with 3 >> quarks. >> > > My recollection is that there are three "valence quarks" which contribute > to the charge and spin of the proton, together with a multitude of "sea > quarks" that do not contribute (perhaps because they're paired up). > > Eric > >
