First measurement of helicity-dependent cross sections in π0η photoproduction from quasi-free nucleons

(A2 Collaboration at MAMI)

Research output: Contribution to journalArticle

Abstract

The helicity-dependent cross sections for the photoproduction of π0η pairs have been measured for the first time. The experiment was performed at the tagged photon facility of the Mainz MAMI accelerator with the combined Crystal Ball – TAPS calorimeter. The experiment used a polarized deuterated butanol target and a circularly polarized photon beam. This arrangement allowed the σ1/2 (photon and target spin antiparallel) and σ3/2 (parallel spins) components to be measured for quasi-free production of π0η pairs off protons and neutrons. The main finding is that the two helicity components contribute identically, within uncertainties, for both participant protons and neutrons. The absolute couplings for protons and neutrons are also identical. This means that nucleon resonances contributing to this reaction in the investigated energy range have almost equal electromagnetic helicity couplings, A1/2 n,p and A3/2 n,p. Identical couplings for protons and neutrons are typical for Δ resonances and identical A1/2 and A3/2 components are only possible for J≥3/2 states, which constrains possible contributions of nucleon resonances.

Original languageEnglish
Pages (from-to)305-312
Number of pages8
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Volume786
DOIs
Publication statusPublished - 10 Nov 2018

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photoproduction
nucleons
neutrons
protons
cross sections
electromagnetic coupling
photon beams
photons
calorimeters
balls
accelerators
crystals
energy

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

Cite this

@article{0295d2f533424aabb11860e03c71502d,
title = "First measurement of helicity-dependent cross sections in π0η photoproduction from quasi-free nucleons",
abstract = "The helicity-dependent cross sections for the photoproduction of π0η pairs have been measured for the first time. The experiment was performed at the tagged photon facility of the Mainz MAMI accelerator with the combined Crystal Ball – TAPS calorimeter. The experiment used a polarized deuterated butanol target and a circularly polarized photon beam. This arrangement allowed the σ1/2 (photon and target spin antiparallel) and σ3/2 (parallel spins) components to be measured for quasi-free production of π0η pairs off protons and neutrons. The main finding is that the two helicity components contribute identically, within uncertainties, for both participant protons and neutrons. The absolute couplings for protons and neutrons are also identical. This means that nucleon resonances contributing to this reaction in the investigated energy range have almost equal electromagnetic helicity couplings, A1/2 n,p and A3/2 n,p. Identical couplings for protons and neutrons are typical for Δ resonances and identical A1/2 and A3/2 components are only possible for J≥3/2 states, which constrains possible contributions of nucleon resonances.",
author = "{(A2 Collaboration at MAMI)} and A. K{\"a}ser and M. Dieterle and L. Witthauer and S. Abt and P. Achenbach and P. Adlarson and F. Afzal and Z. Ahmed and J. Ahrens and Annand, {J. R.M.} and Arends, {H. J.} and M. Bashkanov and R. Beck and M. Biroth and Borisov, {N. S.} and A. Braghieri and Briscoe, {W. J.} and F. Cividini and C. Collicott and S. Costanza and A. Denig and Downie, {E. J.} and P. Drexler and A. Fix and S. Garni and Glazier, {D. I.} and I. Gorodnov and W. Gradl and M. G{\"u}nther and Gurevich, {G. M.} and L. Heijkenskj{\"o}ld and D. Hornidge and Huber, {G. M.} and Kashevarov, {V. L.} and S. Kay and I. Keshelashvili and R. Kondratiev and M. Korolija and B. Krusche and Lazarev, {A. B.} and V. Lisin and K. Livingston and S. Lutterer and MacGregor, {I. J.D.} and Manley, {D. M.} and Martel, {P. P.} and V. Metag and W. Meyer and R. Miskimen and E. Mornacchi",
year = "2018",
month = "11",
day = "10",
doi = "10.1016/j.physletb.2018.10.006",
language = "English",
volume = "786",
pages = "305--312",
journal = "Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics",
issn = "0370-2693",
publisher = "Elsevier",

}

TY - JOUR

T1 - First measurement of helicity-dependent cross sections in π0η photoproduction from quasi-free nucleons

AU - (A2 Collaboration at MAMI)

AU - Käser, A.

AU - Dieterle, M.

AU - Witthauer, L.

AU - Abt, S.

AU - Achenbach, P.

AU - Adlarson, P.

AU - Afzal, F.

AU - Ahmed, Z.

AU - Ahrens, J.

AU - Annand, J. R.M.

AU - Arends, H. J.

AU - Bashkanov, M.

AU - Beck, R.

AU - Biroth, M.

AU - Borisov, N. S.

AU - Braghieri, A.

AU - Briscoe, W. J.

AU - Cividini, F.

AU - Collicott, C.

AU - Costanza, S.

AU - Denig, A.

AU - Downie, E. J.

AU - Drexler, P.

AU - Fix, A.

AU - Garni, S.

AU - Glazier, D. I.

AU - Gorodnov, I.

AU - Gradl, W.

AU - Günther, M.

AU - Gurevich, G. M.

AU - Heijkenskjöld, L.

AU - Hornidge, D.

AU - Huber, G. M.

AU - Kashevarov, V. L.

AU - Kay, S.

AU - Keshelashvili, I.

AU - Kondratiev, R.

AU - Korolija, M.

AU - Krusche, B.

AU - Lazarev, A. B.

AU - Lisin, V.

AU - Livingston, K.

AU - Lutterer, S.

AU - MacGregor, I. J.D.

AU - Manley, D. M.

AU - Martel, P. P.

AU - Metag, V.

AU - Meyer, W.

AU - Miskimen, R.

AU - Mornacchi, E.

PY - 2018/11/10

Y1 - 2018/11/10

N2 - The helicity-dependent cross sections for the photoproduction of π0η pairs have been measured for the first time. The experiment was performed at the tagged photon facility of the Mainz MAMI accelerator with the combined Crystal Ball – TAPS calorimeter. The experiment used a polarized deuterated butanol target and a circularly polarized photon beam. This arrangement allowed the σ1/2 (photon and target spin antiparallel) and σ3/2 (parallel spins) components to be measured for quasi-free production of π0η pairs off protons and neutrons. The main finding is that the two helicity components contribute identically, within uncertainties, for both participant protons and neutrons. The absolute couplings for protons and neutrons are also identical. This means that nucleon resonances contributing to this reaction in the investigated energy range have almost equal electromagnetic helicity couplings, A1/2 n,p and A3/2 n,p. Identical couplings for protons and neutrons are typical for Δ resonances and identical A1/2 and A3/2 components are only possible for J≥3/2 states, which constrains possible contributions of nucleon resonances.

AB - The helicity-dependent cross sections for the photoproduction of π0η pairs have been measured for the first time. The experiment was performed at the tagged photon facility of the Mainz MAMI accelerator with the combined Crystal Ball – TAPS calorimeter. The experiment used a polarized deuterated butanol target and a circularly polarized photon beam. This arrangement allowed the σ1/2 (photon and target spin antiparallel) and σ3/2 (parallel spins) components to be measured for quasi-free production of π0η pairs off protons and neutrons. The main finding is that the two helicity components contribute identically, within uncertainties, for both participant protons and neutrons. The absolute couplings for protons and neutrons are also identical. This means that nucleon resonances contributing to this reaction in the investigated energy range have almost equal electromagnetic helicity couplings, A1/2 n,p and A3/2 n,p. Identical couplings for protons and neutrons are typical for Δ resonances and identical A1/2 and A3/2 components are only possible for J≥3/2 states, which constrains possible contributions of nucleon resonances.

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U2 - 10.1016/j.physletb.2018.10.006

DO - 10.1016/j.physletb.2018.10.006

M3 - Article

VL - 786

SP - 305

EP - 312

JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics

SN - 0370-2693

ER -