Research in Theoretical Hadronic Physics and Related Topics

College Of William And Mary, Williamsburg VA

Investigators

Abstract

We propose to investigate a n mber of topics,including: Hard Pion Electroproduction. We will calculate high transverse momentum semi-exclusive pion electroproduction,considering especially the higher twist process where the pions are pro- duced directly and appear kinematically isolated,but including leading twist (where the pions are produced by parton fragmentation and appear as part of a jet)and estimates of soft pro- cesses.The direct and leading twist processes allow data to yield information about the quark and gluon distributions in the target.Two particular new items are to do electroproduction rather than photoproduction and to include initial state parton transverse momentum.An ap- plication is to see if the higher twist process are relevant to data from HERMES,and possibly Hall B data from Je .erson Lab,where there is considerable interest in the result. Dipions and the Polarization of Gluons. HERMES has measured dipions photoproduced with polarized photons o .polarized targets,which has given the .rst determination of the po- larization of gluons in the proton.The published result depends heavily upon the theoretical analysis,in turn heavily based on program packages that are tuned to higher energies.We propose what we believe is a necessary independent calculation the contributions of the vari- ous processes (photon-gluon fusion,QCD Compton,and vector meson dominance (VMD)),in particular to see the sensitivity of the results to di .ering fragmentation models,initial state transverse momentum,and di .ering estimates of the VMD contribution. The Deuteron Form Factor. The only perturbative QCD calculation of the asymptotic deuteron form factor lies well below the data,but strikingly omits the short range wave functions that provide for hidden color states.We have recently developed ways to manipulate 6-quark cluster wave functions that model these components.We propose to calculate the asymptotic form factor with wave functions including a hidden color component,to see the e .ect of the hidden color components upon the magnitude of the result. Bringing Perturbative QCD to Lower Momentum Transfers. We will study formal and applied aspects of relations between the Breit and light-front helicity amplitudes,next-to-leading power corrections to the high momentum transfer behavior of those amplitudes,and application of discrete symmetries to light-front amplitudes.The formal results can allow s,for example,to .nd constraints that approximations to the subdominant helicity amplitudes must obey (which are not always realized in the literature).More positively,we can se the formal results to guide investigation of how non-leading powers can be parameterized and see,again for example,how and where the N .(1232)transition may approach the perturbative QCD results. Phenomenology of Noncommutative Field Theory. Following up on an earlier research path,we would like to complete the set of Feynman rules for the Lorentz conserving noncom- mutative .eld theory and .nd the signatures of noncommutative spacetime for a selection of processes in addition to fAfA elastic scattering.Also we would like to consider ways to do Lorentz conserving noncommutative .eld theory with operator algebras in addition to the contracted Snyder algebra we have worked out so far. NSF Review Criteria. Intellectual merit of the proposed activity:Most of the activity is at the forefront of modern hadronic physics,and the rest is at the forefront of the phenomenology of an interesting direction in particle physics.The projects will lead to many publications in the leading refereed journals.Broader impacts of the proposed activity:The projects will help bridge the gap between hadronic theory and observed phenomena,and lead to greater understanding of the mechanisms of hadronic reactions.They will also train new students, including undergraduates.The PI has had two successful women Ph.D.students,and the present project may extend opportunities for women entering the .eld.The PI is regularly at the Je .erson Laboratory and bridging the gap between university and national lab as well as between data and theory.