Pion-LT (E12-19-006)

h2. 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 binds 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 the 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 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. 

The E12-07-105 experiment is an exclusive measurement of the L/T separated pion electroproduction cross section, it aims 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 the 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 conducting a measurement of the Q2 dependence of the 

π+ longitudinal and transverse cross sections. A significant longitudinal response may be indicative of the realisation 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 of the 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 the Hall C High Momentum Spectrometer (HMS) and Super High Momentum Spectrometer (SHMS). We will extract the cross sections using the Rosenbluth technique. In additon, measurements in non-parallel kinematics will allow for simultaneous extraction of the interference terms and serve as a test of t-dependence of the π+ cross section. 

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h2. E12-07-105 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

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h2. Run Information

* [[Run Plans and Run Sheets]] 

* "Experimental Safety Asessment Documentation Summer 2019":https://hallcweb.jlab.org/safety-docs/Summer2019/ESAD.pdf

* "Conduct of Operations Summer 2019":https://hallcweb.jlab.org/safety-docs/Summer2019/ESAD.pdf

* "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

* "Beam Schedule":https://www.jlab.org/exp_prog/experiment_schedule/2019/20190225.0.pdf

* "Shift Signup":https://misportal.jlab.org/mis/apps/physics/shiftSchedule/index.cfm?experimentRunId=HALLC-SPRING-2019

* "Shift Signup, read only":https://misportal.jlab.org/mis/physics/shiftSchedule/?experimentRunId=HALLC-SPRING-2019

* Hall C How-Tos: "1":https://hallcweb.jlab.org/document/howtos/ , "2":https://hallcweb.jlab.org/wiki/index.php/How-to

* "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

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h2. Data Analysis

* "UTIL_PION Git Repository":https://github.com/JeffersonLab/UTIL_PION

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

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

* [[Online Replay Histograms]]

* "Joint Hall A & C Data Analysis":https://redmine.jlab.org/projects/podd/wiki/Workshop2018

* "L/T Separation Software":https://github.com/billlee77/omega_analysis (see Sec 4.2 of https://misportal.jlab.org/ul/publications/view_pub.cfm?pub_id=15234 for description)

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h2. Meetings

* [[Hall C Commissioning Analysis Meetings]]

* "Detector Working Group Meetings":https://hallcweb.jlab.org/wiki/index.php/Detector_Working_Group_Meetings#Detector_Working_Group_Meetings_in_2017

* [[Pion LT Meetings]]

* [[BlueJeans Information]]  

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h2. Collaboration

* [[Spokespersons]]

* [[Collaboration List]]

* [[Mailing List]]