Pion-LT (E12-19-006)

h1. Experiment Overview

Pion occupies a special place in nature as one of the lightest hadrons, with one valence quark, and one valence antiquark. Small as it might be, the pion is also responsible for the long range character of the strong interaction that bind the atomic nucleus together. If chiral symmetry, which implies that Dirac Fermions are massless, were an exact global symmetry of strong interactions then pions would be massless. Through gluon-quark interaction and by explicit inclusion of light quark masses, chiral symmetry of massless QCD undergoes explicit symmetry breaking, thus giving pion its mass. This puts the pion at the core of the mechanism that dynamically generates all the mass of the hadrons and makes it a crucial element in understanding the hadron structure. Globally, this experiment will aim to confirm the potential of pion measurements both for studies of the pion structure itself and of the 3D structure of the proton, in terms of spatial imaging (tomography). In particular, E12-07-105 will probe if the measurements to map the spatial extension of the charged pion can be utilized to enable 3D spatial tomography of light quarks. 

TheE12-07-105 experiment is an exclusive measurement of the L/T separated pion electroproduction cross section aimed to probe conditions for factorization of deep exclusive measurements for charged pions in GPD studies and the pion form factor. It will make precision measurements of the L/T separated pion electroproduction cross sections to the highest achievable value of Q2 at the 12 GeV Jefferson Lab, ~10 GeV2. Before considering the extraction of GPDs from pion electroproduction data, we must confirm that charged pion longitudinal cross section is more dominant than the transverse cross section as expected from GPD models. We will test the longitudinal cross section dominance in charged pion production by making measurement of the Q2 dependence of the 

π+ longitudinal and transverse cross sections. A significant longitudinal response maybe indicative of the realization of the scaling expectation of the GPD formalism for charged pion electroproduction. The results may be useful in constraining the longitudinal backgrounds in the extraction if pion form factor from pion electroproduction data. We will measure forward π+ electroproduction by detecting the the pion produced in coincidence with the scattered electron using Hall C HMS and SHMS confuguration, and extract the cross sections using Rosenbluth technique. In additon, measurements in non-parallel kinematics will allow for simultaneous extraction of the interference terms and test of t- dependence of the π+ cross section. 

h2. PR12-07-105 Documents

"Proposals":https://misportal.jlab.org/mis/physics/experiments/viewProposal.cfm?paperId=512

"Hall C Wiki":https://hallcweb.jlab.org/wiki/index.php/Main_Page

"Hall C Electronic Logbook":https://logbooks.jlab.org/book/hclog

Hall C Information":https://www.jlab.org/physics/hall-c

"Experiment Schedule":https://www.jlab.org/physics/experiments/schedule

h3. Run Information

"Information for Shift Takers":https://hallcweb.jlab.org/wiki/index.php/Information_for_Shift_Takers

"Documentation for Running Hall C":https://www.jlab.org/Hall-C/document/manuals.html

"Analysis on Cdaq":https://hallcweb.jlab.org/wiki/index.php/Analysis_How-to

"Contact Experts":https://hallcweb.jlab.org/wiki/index.php/Experts_on_call

h4. Data Analysis

"SIMC":https://hallcweb.jlab.org/wiki/index.php/SIMC_Monte_Carlo

"Hall C Analyzer":https://hallcweb.jlab.org/wiki/index.php/ROOT_Analyzer