Publications
Publication Information
| Title | Polarized electron-deuteron deep-inelastic scattering with spectator nucleon tagging |
| Authors | Wim Cosyn, Christian Weiss |
| JLAB number | JLAB-THY-20-3203 |
| LANL number | arXiv:2006.03033 |
| Other number | DOE/OR/23177-4982 |
| Document Type(s) | (Journal Article) |
| Associated with EIC: | No |
| Supported by Jefferson Lab LDRD Funding: | Yes |
| LDRD Numbers: | 2015-LDRD-06 |
| Funding Source: | Nuclear Physics (NP) |
|
Journal Compiled for Physical Review C Volume 102 Page(s) 065204 Refereed | |
| Publication Abstract: | BACKGROUND: Deep-inelastic scattering (DIS) on the deuteron with detection of a proton in the nuclear fragmentation region (spectator tagging) represents a unique method for extracting the free neutron structure functions and studying their modifications by nuclear binding. The measured proton momentum controls the nuclear configuration during the DIS process and enables a differential analysis of nuclear effects. Combined with electron and deuteron polarization, spectator tagging can be used to extract the free neutron spin structure functions and explore spin-dependent nuclear effects. Such measurements would become possible with the future electron-ion collider (EIC) with polarized electron and deuteron beams and forward proton detectors. PURPOSE: Develop theoretical framework for polarized deuteron DIS with spectator tagging. Calculate the differential cross section and spin observables with spectator tagging; separate low-energy nuclear structure from high-energy DIS process; calculate the polarized deuteron spectral function; study the dependence on the tagged proton momentum; formulate procedures for neutron spin structure extraction. METHODS: The spin density matrix formalism is used to describe general deuteron polarization in collider experiments in relativistically covariant form (vector and tensor polarization, pure states and ensembles). Light-front (LF) quantum mechanics is employed to factorize nuclear and nucleonic structure in the DIS process. The polarized deuteron LF wave function in the proton-neutron degrees of freedom is constructed in a 4-dimensional representation (4-vectors, bispinors), which avoids the use of explicit Melosh rotations and permits efficient evaluation of spin sums. Correspondence with nonrelativistic deuteron structure in the rest frame is established. The polarized deuteron LF spectral function is constructed to summarize the relevant deuteron structure information. Tagged deuteron structure functions are calculated in the impulse approximation (IA). Free neutron structure functions and spin asymmetries are extracted using complex analyticity in the tagged proton momentum (pole extrapolation). RESULTS: General formulas for the polarized tagged deuteron cross section in relativistically invariant form (depolarization factors, structure functions, spin asymmetries). Analytic and numerical results for the polarized deuteron LF spectral function and the nucleon LF momentum distributions (vector and tensor polarization, S and D-waves). Practical expressions for the polarized tagged deuteron structure functions in the IA, permitting studies of the tagged proton momentum dependence and free neutron structure extraction through pole extrapolation. CONCLUSIONS: Tagged DIS provides new tools for precise neutron spin structure measurements. D-wave depolarization can be eliminated through the tagged proton momentum dependence. The neutron spin structure function g_{1n} can be extracted efficiently from the tagged deuteron helicity asymmetry (+- 1 states only, 0 state not needed). The methods can be extended to study tensor-polarized observables, spin-orbit effects in deuteron breakup, and exclusive and diffractive scattering processes. |
| Experiment Numbers: | |
| Group: | THEORY CENTER |
| Document: | |
| DOI: | https://doi.org/10.1103/PhysRevC.102.065204 |
| Accepted Manuscript: | PhysRevC.102.065204.pdf |
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