Presentation on theme: "Kinematics Related Systematic Uncertainties via MCEEP P.E. Ulmer Old Dominion University 12/11/02 Hall A Analysis Workshop."— Presentation transcript:
Kinematics Related Systematic Uncertainties via MCEEP P.E. Ulmer Old Dominion University 12/11/02 Hall A Analysis Workshop
Breaking News: Cross sections depend on kinematics! Uncertainties run wild! Coincidence cross section can vary strongly with kinematics. Results in systematic uncertainties: –need to evaluate changes in cross section for variations of kinematical quantities. Account for kinematical constraints: –For example, fixed missing mass. –May include constraints from various calibration measurements, such as H(e,ep) Must acceptance average derivatives. Its a snap with new MCEEP tools: –Cross sections handled at present. –Other observables could be added easily. –Satisfaction guaranteed or your money back.
Procedure MCEEP Hbook file Process MCEEP Ntuple: Get cross sections for variations of kinematical quantities Determine cross section derivatives and total uncertainty, including any kinematical correlations
Process Ntuple Fortran Program: systerr Start with MCEEP Ntuple, containing Transport coordinates at target Vary nine quantities, in turn: (beam, scatt. electron, ejectile) x (delta, phi, theta) Produce new Ntuple, consisting of original variables plus 10 cross sections (nominal and nine shifted). Program links to MCEEP subroutines and has access to its physics models.
Acceptance Average PAW: systerr.kumac Error sum: positive definite quantity –Must first acceptance average. Sum the weights: –Produce vectors of summed cross sections (10 in total). –Bin vectors in terms of any kinematical quantity within Ntuple. Diagnostic histograms: –Fractional derivatives of cross section with respect to each of the nine varied kinematical quantities.
Combine Errors Fortran Program: toterr Produce cross section uncertainty, given kinematical uncertainties and correlations. For each bin, form:
www.physics.odu.edu/~ulmer/mceep /mceep.html –Includes: Sources Installation Instructions User manual –In particular, see: ~/mceep/systerr/README JLAB-TN-02-015 Systematic Uncertainties in E89-003 (K. Fissum & P.E. Ulmer) See: http://hallaweb.jlab.org/publications/Technotes/ files/2002/02-015.ps More Information
Figures Both figures are based on Experiment E94-004 D(e,ep)n cross section vs. Pm –Cross section derivatives for each of the nine quantities: Kinematics centered on Pm=100 MeV/c Units: fractional derivatives per 1 mr or per 10^-3 in momentum. –Total error vs. Pm All kinematics for E94-004 included, from Pm=0 to Pm=500 MeV/c (central values) Uncorrelated analysis Correlated analysis: assumes constraints from 1H(e,ep)