Momentum Corrections for the CLAS E5 Data Set

The Thomas Jefferson National Accelerator Facility located in Newport News, Virginia, is home to the CLAS (CEBAF Large Acceptance Spectrometer) detector, which measures scattered particles from high-energy collisions of an electron beam and a nuclear target. Initial measurement of the momentum of charged particles is done by reconstructing tracks using several different detecting elements and a toroidal magnetic field. To improve the accuracy and precision of these momentum measurements for the electron and proton, we have applied the following algorithm. (1) Establish a known standard using the neutron peak in the $ep\rightarrow e^\prime \pi^+ X$ reaction and applying the missing mass technique. (2) Calculate the curvature, $qB/p_m$, event by event where $q$q is particle charge, $B$ is the ratio of torus magnet current to 3860A, and $p_m$ is the reconstructed particle momentum. (3) Calculate the curvature again using the particle momentum $p_c$ derived from only the polar angle of the track. This angle is measured with high precision. (4) Plot the difference between these two curvatures $\Delta(qB/p)$ versus $qB/p_c$ and fit the results to a line. (5) Use these fit results to calculate a new corrected momentum and use it to calculate the missing mass in Step 1. We will present the results of this procedure for the E5 running period at a beam energy of 2.56 GeV on a deuterium target.