Measurement of the Unpolarized K⁺ Λ and K⁺ Σ⁰ Electroproduction Cross Sections and Interference Terms from the Proton with the CLAS Detector

Abstract

Using the CLAS detector, we measure the K + Λ and K + Σ 0 electroproduction response functions over the continuous kinematic range from threshold to W = 2.05 GeV and for Q 2 between 0.5 and 1.5 (GeV/c) 2 , with nearly complete angular coverage in the center-of-momentum frame angles. The σ T + σ L , σ T T and σ LT terms are extracted and compared to recent theoretical calculations based upon a hadrodynamic effective-Lagrangian framework. From examining the W-dependence of the response functions for the K + Λ final state, we find features in the (σ T + σ L) term in the W = 1.75 to 1.90 GeV region, similar to features seen in recent photoproduction results. In general, the σ T T and σ LT response-functions for Λ production are of the same order of magnitude as the (σ T + σ L) term, suggesting that both σ T and σ L contribute significantly. For the K + Σ 0 final state the W-dependence of the (σ T + σ L) and σ T T terms have large, resonant-like features near W = 1.9 GeV. Unlike in Λ electroproduction, the σ LT interference term for Σ 0 electroproduction is found to be consistent with zero across nearly the entire kinematic range, while σ T T is comparable in magnitude to the σ T + σ L differential cross-section. The models, while achieving some qualitative agreement with the data, fail to both describe the details of the angular distributions and reproduce the resonant-like behavior observed. i Acknowledgments This measurement was the result of the contributions and hard work of many individuals, to whom I am thankful. I would like to specifically acknowledge the assistance and support offered by the Jefferson Lab staff, the past and present members of the CLAS Collaboration, and by all the members of the CMU Medium Energy group. My financial support was provided by the Department of Energy. Finally, I owe the completion of this project to the emotional support of friends and family. I would like to thank the Medium Energy Group at CMU for their assistance, support and for maintaining an open and (relatively) stress-free environment in which to work. First, I am grateful to my advisor, Reinhard Schumacher, for his support, council, and shared experience throughout the duration. My also thanks go out to my longtime friend, colleague, and office-mate John McNabb for the relentless discussions and debates, occasional distractions, and overall support. I am indebted to Bob Bradford for his friendship and selfless assistance. Paul Eugenio and Kent Paschke both possessed an inspirational enthusiasm, on the softball field and in the office, that made my graduate-student life and work more enjoyable. My discussions with Professors Curtis Meyer, Gregg Franklin, and Brian Quinn helped broaden my view of nuclear physics beyond my specific experiment, as well as improving the analysis, and are valued as well. I would like to also thank Professors Robert Kraemer and Frank Tabakin for serving on my thesis committee. I wish to thank Si McAleer and Steve Barrow for their tireless efforts to process the data used in this analysis, as...