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arXiv · 2211.09688

Neutron polarisation transfer, $C_{x'}^n$, in $\pi^+$ photoproduction off the proton

M. Bashkanov·D. P. Watts·S. J. D. Kay·S. Abt·P. Achenbach·P. Adlarson·F. Afzal·Z. Ahmed·C. S. Akondi·J. R. M. Annand·R. Beck·M. Biroth·N. Borisov·A. Braghieri·W. J. Briscoe·F. Cividini·C. Collicott·S. Costanza·A. Denig·E. J. Downie·P. Drexler·S. Fegan·A. Fix·S. Gardner·D. Ghosal·D. I. Glazier·I. Gorodnov·W. Gradl·D. Gurevich·L. Heijkenskjöld·D. Hornidge·G. M. Huber·V. L. Kashevarov·M. Korolija·B. Krusche·A. Lazarev·K. Livingston·S. Lutterer·I. J. D. MacGregor·D. M. Manley·P. P. Martel·R. Miskimen·E. Mornacchi·C. Mullen·A. Neganov·A. Neiser·M. Ostrick·P. B. Otte·D. Paudyal·P. Pedroni·T. Rostomyan·V. Sokhoyan·K. Spieker·O. Steffen·I. I. Strakovsky·T. Strub·I. Supek·A. Thiel·M. Thiel·A. Thomas·Yu. A. Usov·S. Wagner·N. K. Walford·J. Wettig·M. Wolfes·N. Zachariou
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Abstract

We report a first measurement of the double-polarisation observable, $C_{x'}$, in $\pi^+$ photoproduction off the proton. The $C_{x'}$ double-polarisation observable represents the transfer of polarisation from a circularly polarised photon beam to the recoiling neutron. The MAMI circularly polarised photon beam impinged on a liquid deuterium target cell, with reaction products detected in the Crystal Ball calorimeter. Ancillary apparatus surrounding the target provided tracking, particle identification and determination of recoil nucleon polarisation. The $C_{x'}$ observable is determined for photon energies 800-1400 MeV, providing new constraints on models aiming to elucidate the spectrum and properties of nucleon resonances. This is the first determination of any polarisation observable from the beam-recoil group of observables for this reaction, providing a valuable constraint and systematic check of the current solutions of partial wave analysis based theoretical models.

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M. Bashkanov, D. P. Watts, S. J. D. Kay, S. Abt, P. Achenbach, P. Adlarson, F. Afzal, Z. Ahmed, C. S. Akondi, J. R. M. Annand, R. Beck, M. Biroth, N. Borisov, A. Braghieri, W. J. Briscoe, F. Cividini, C. Collicott, S. Costanza, A. Denig, E. J. Downie, P. Drexler, S. Fegan, A. Fix, S. Gardner, D. Ghosal, D. I. Glazier, I. Gorodnov, W. Gradl, D. Gurevich, L. Heijkenskjöld, D. Hornidge, G. M. Huber, V. L. Kashevarov, M. Korolija, B. Krusche, A. Lazarev, K. Livingston, S. Lutterer, I. J. D. MacGregor, D. M. Manley, P. P. Martel, R. Miskimen, E. Mornacchi, C. Mullen, A. Neganov, A. Neiser, M. Ostrick, P. B. Otte, D. Paudyal, P. Pedroni, T. Rostomyan, V. Sokhoyan, K. Spieker, O. Steffen, I. I. Strakovsky, T. Strub, I. Supek, A. Thiel, M. Thiel, A. Thomas, Yu. A. Usov, S. Wagner, N. K. Walford, J. Wettig, M. Wolfes, N. Zachariou. 2022-11-17. Neutron polarisation transfer, $C_{x'}^n$, in $\pi^+$ photoproduction off the proton. https://arxiv.org/abs/2211.09688

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