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Analysis of Pair-Symmetric Background Effects on DIS Asymmetry at Jefferson Lab

This paper discusses the impact of background factors on Deep Inelastic Scattering (DIS) asymmetry, specifically focusing on e+e- pairs in the SANE kinematics framework. The analysis covers the contributions of background rates and asymmetries, and systematic errors associated with electron-positron pairs. Key elements include the examination of background contamination, corrections for measured asymmetry, and the trajectory of pairs in experimental setups at Jefferson Lab. The findings are significant for advancing SSF studies related to particle physics.

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Analysis of Pair-Symmetric Background Effects on DIS Asymmetry at Jefferson Lab

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  1. Pair-Symmetric Background Analysis Luwani Z. Ndukum Mississippi State University Hall C Users’ Group Meeting, Jefferson Lab, January, 2010

  2. Motivation • World data and SANE kinematics • Recover data at low x SANE

  3. Outline • Introduction • Effects of Background on DIS Asymmetry • Asymmetry Analysis • Pair Systematic Errors • Trajectory of an electron-positron pair in SANE • Summary

  4. Introduction • Background mostly e+ e- pair • Contamination in cerenkov • Bethe-Heitler (bremsstrahlung) • π0 decay: π0 → γ e+e- (1.2%) π0 → γγ (99%) • Correction will contribute to SSF studies

  5. Effect of Background on DIS Asymmetry • BETA is charge insensitive • The measured electron asymmetry must be corrected for the background counts and asymmetry • Need to estimate both background rate and asymmetry

  6. Asymmetry Analysis • The measured electron asymmetry • where • = measured asymmetry • = Physics asymmetry, • = Background asymmetry • = measured counts, • = fraction of background

  7. Pair Systematic Error • If we assume , but has an uncertainty given by with = e+/e- ratio • Systematic error is given by • Systematic uncertainty • > 20% for E' < 1.1 GeV • Data from table of Vipuli D., SANE report 4/21/05

  8. Pair Systematic Error • Hall C analysis from Jason Seely • Clear theta dependence • Contamination is small at large angles From: VipuliDharmawardane SANE report 4/21/05

  9. Trajectory of an e+e- pair for SANE Example: (each particle) • Pair starting direction: 40° (along BETA's axis) • Vertical deflection = 11.93° (translates to 71cm in BigCal) • 700 MeV/c corresponds to x=0.2 for DIS electrons Top side

  10. Summary • Background for SANE is mostly e+e- pairs • Clear theta dependence • Small contamination at large angles • Large magnifies error • Need to estimate both the background rate and the asymmetry • Systematic uncertainty >20% for E' < 1.1 GeV

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