Measurement of the beam-helicity asymmetry I-circle dot in the photoproduction of pi(0)pi(+/-) pairs off protons and off neutrons

Crystal Ball MAMI Collaboration; Crystal Ball TAPS Collaboration; Crystal Ball A2 Collaboration; M. Oberle; J. Ahrens; J. R. M. Annand; H. J. Arends; K. Bantawa; P. A. Bartolome; R. Beck; V. Bekrenev; H. Berghauser; A. Braghieri; D. Branford; W. J. Briscoe; J. Brudvik; S. Cherepnya; B. Demissie; M. Dieterle; E. J. Downie; P. Drexler; L. V. Fil'kov; A. Fix; D. I. Glazier; E. Heid; D. Hornidge; D. Howdle; G. M. Huber; O. Jahn; I. Jaegle; T. C. Jude; A. Kaeser; V. L. Kashevarov; I. Keshelashvili; R. Kondratiev; M. Korolija; S. P. Kruglov; B. Krusche; A. Kulbardis; V. Lisin; K. Livingston; I. J. D. MacGregor; Y. Maghrbi; J. Mancell; D. M. Manley; Z. Marinides; M. Martinez; J. C. McGeorge; E. McNicoll; D. Mekterovic; V. Metag; S. Micanovic; D. P. Watts

doi:10.1140/epja/i2014-14054-5

Measurement of the beam-helicity asymmetry I-circle dot in the photoproduction of pi(0)pi(+/-) pairs off protons and off neutrons

Crystal Ball MAMI Collaboration, Crystal Ball TAPS Collaboration, Crystal Ball A2 Collaboration, M. Oberle^*, J. Ahrens, J. R. M. Annand, H. J. Arends, K. Bantawa, P. A. Bartolome, R. Beck, V. Bekrenev, H. Berghauser, A. Braghieri, D. Branford, W. J. Briscoe, J. Brudvik, S. Cherepnya, B. Demissie, M. Dieterle, E. J. DownieP. Drexler, L. V. Fil'kov, A. Fix, D. I. Glazier, E. Heid, D. Hornidge, D. Howdle, G. M. Huber, O. Jahn, I. Jaegle, T. C. Jude, A. Kaeser, V. L. Kashevarov, I. Keshelashvili, R. Kondratiev, M. Korolija, S. P. Kruglov, B. Krusche, A. Kulbardis, V. Lisin, K. Livingston, I. J. D. MacGregor, Y. Maghrbi, J. Mancell, D. M. Manley, Z. Marinides, M. Martinez, J. C. McGeorge, E. McNicoll, D. Mekterovic, V. Metag, S. Micanovic, D. P. Watts

^*Corresponding author for this work

School of Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

Abstract / Description of output

Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz for the photoproduction of mixed-charge pion pairs in the reactions gamma p -> n pi(0)pi(+) off free protons and gamma d -> (p)p pi(0)pi(-) and gamma d -> (p)n pi(0)pi(+) off quasi-free nucleons bound in the deuteron for incident photon energies up to 1.4 GeV. Circularly polarized photons were produced from bremsstrahlung of longitudinally polarized electrons and tagged with the Glasgow-Mainz magnetic spectrometer. The charged pions, recoil protons, recoil neutrons, and decay photons from pi(0) mesons were detected in the 4 pi electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. Using a complete kinematic reconstruction of the final state, excellent agreement was found between the results for free and quasi-free protons, suggesting that the quasi-free neutron results are also a close approximation of the free-neutron asymmetries. A comparison of the results to the predictions of the Two-Pion-MAID reaction model shows that the reaction mechanisms are still not well understood, in particular at low incident photon energies in the second nucleon-resonance region.

Original language	English
Article number	54
Number of pages	18
Journal	The European Physical Journal A (EPJ A)
Volume	50
Issue number	3
DOIs	https://doi.org/10.1140/epja/i2014-14054-5
Publication status	Published - 10 Mar 2014

Keywords / Materials (for Non-textual outputs)

DOUBLE-PION-PHOTOPRODUCTION
TAGGED PHOTON SPECTROMETER
CROSS-SECTION MEASUREMENT
2ND RESONANCE REGION
PI(0) PHOTOPRODUCTION
BARYON RESONANCES
PARTIAL-WAVE
MICROTRON
THRESHOLD
DEUTERON

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10.1140/epja/i2014-14054-5

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Crystal Ball MAMI Collaboration, Crystal Ball TAPS Collaboration, Crystal Ball A2 Collaboration, Oberle, M., Ahrens, J., Annand, J. R. M., Arends, H. J., Bantawa, K., Bartolome, P. A., Beck, R., Bekrenev, V., Berghauser, H., Braghieri, A., Branford, D., Briscoe, W. J., Brudvik, J., Cherepnya, S., Demissie, B., Dieterle, M., ... Watts, D. P. (2014). Measurement of the beam-helicity asymmetry I-circle dot in the photoproduction of pi(0)pi(+/-) pairs off protons and off neutrons. The European Physical Journal A (EPJ A), 50(3), Article 54. https://doi.org/10.1140/epja/i2014-14054-5

@article{10bccf51b3674e0b8b827586ecbe6c75,

title = "Measurement of the beam-helicity asymmetry I-circle dot in the photoproduction of pi(0)pi(+/-) pairs off protons and off neutrons",

abstract = "Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz for the photoproduction of mixed-charge pion pairs in the reactions gamma p -> n pi(0)pi(+) off free protons and gamma d -> (p)p pi(0)pi(-) and gamma d -> (p)n pi(0)pi(+) off quasi-free nucleons bound in the deuteron for incident photon energies up to 1.4 GeV. Circularly polarized photons were produced from bremsstrahlung of longitudinally polarized electrons and tagged with the Glasgow-Mainz magnetic spectrometer. The charged pions, recoil protons, recoil neutrons, and decay photons from pi(0) mesons were detected in the 4 pi electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. Using a complete kinematic reconstruction of the final state, excellent agreement was found between the results for free and quasi-free protons, suggesting that the quasi-free neutron results are also a close approximation of the free-neutron asymmetries. A comparison of the results to the predictions of the Two-Pion-MAID reaction model shows that the reaction mechanisms are still not well understood, in particular at low incident photon energies in the second nucleon-resonance region.",

keywords = "DOUBLE-PION-PHOTOPRODUCTION, TAGGED PHOTON SPECTROMETER, CROSS-SECTION MEASUREMENT, 2ND RESONANCE REGION, PI(0) PHOTOPRODUCTION, BARYON RESONANCES, PARTIAL-WAVE, MICROTRON, THRESHOLD, DEUTERON",

author = "{Crystal Ball MAMI Collaboration} and {Crystal Ball TAPS Collaboration} and {Crystal Ball A2 Collaboration} and M. Oberle and J. Ahrens and Annand, {J. R. M.} and Arends, {H. J.} and K. Bantawa and Bartolome, {P. A.} and R. Beck and V. Bekrenev and H. Berghauser and A. Braghieri and D. Branford and Briscoe, {W. J.} and J. Brudvik and S. Cherepnya and B. Demissie and M. Dieterle and Downie, {E. J.} and P. Drexler and Fil'kov, {L. V.} and A. Fix and Glazier, {D. I.} and E. Heid and D. Hornidge and D. Howdle and Huber, {G. M.} and O. Jahn and I. Jaegle and Jude, {T. C.} and A. Kaeser and Kashevarov, {V. L.} and I. Keshelashvili and R. Kondratiev and M. Korolija and Kruglov, {S. P.} and B. Krusche and A. Kulbardis and V. Lisin and K. Livingston and MacGregor, {I. J. D.} and Y. Maghrbi and J. Mancell and Manley, {D. M.} and Z. Marinides and M. Martinez and McGeorge, {J. C.} and E. McNicoll and D. Mekterovic and V. Metag and S. Micanovic and Watts, {D. P.}",

year = "2014",

month = mar,

day = "10",

doi = "10.1140/epja/i2014-14054-5",

language = "English",

volume = "50",

journal = "The European Physical Journal A (EPJ A)",

issn = "1434-6001",

publisher = "Springer",

number = "3",

}

Crystal Ball MAMI Collaboration, Crystal Ball TAPS Collaboration, Crystal Ball A2 Collaboration, Oberle, M, Ahrens, J, Annand, JRM, Arends, HJ, Bantawa, K, Bartolome, PA, Beck, R, Bekrenev, V, Berghauser, H, Braghieri, A, Branford, D, Briscoe, WJ, Brudvik, J, Cherepnya, S, Demissie, B, Dieterle, M, Downie, EJ, Drexler, P, Fil'kov, LV, Fix, A, Glazier, DI, Heid, E, Hornidge, D, Howdle, D, Huber, GM, Jahn, O, Jaegle, I, Jude, TC, Kaeser, A, Kashevarov, VL, Keshelashvili, I, Kondratiev, R, Korolija, M, Kruglov, SP, Krusche, B, Kulbardis, A, Lisin, V, Livingston, K, MacGregor, IJD, Maghrbi, Y, Mancell, J, Manley, DM, Marinides, Z, Martinez, M, McGeorge, JC, McNicoll, E, Mekterovic, D, Metag, V, Micanovic, S & Watts, DP 2014, 'Measurement of the beam-helicity asymmetry I-circle dot in the photoproduction of pi(0)pi(+/-) pairs off protons and off neutrons', The European Physical Journal A (EPJ A), vol. 50, no. 3, 54. https://doi.org/10.1140/epja/i2014-14054-5

Measurement of the beam-helicity asymmetry I-circle dot in the photoproduction of pi(0)pi(+/-) pairs off protons and off neutrons. / Crystal Ball MAMI Collaboration; Crystal Ball TAPS Collaboration; Crystal Ball A2 Collaboration et al.
In: The European Physical Journal A (EPJ A), Vol. 50, No. 3, 54, 10.03.2014.

Research output: Contribution to journal › Article › peer-review

TY - JOUR

T1 - Measurement of the beam-helicity asymmetry I-circle dot in the photoproduction of pi(0)pi(+/-) pairs off protons and off neutrons

AU - Crystal Ball MAMI Collaboration

AU - Crystal Ball TAPS Collaboration

AU - Crystal Ball A2 Collaboration

AU - Oberle, M.

AU - Ahrens, J.

AU - Annand, J. R. M.

AU - Arends, H. J.

AU - Bantawa, K.

AU - Bartolome, P. A.

AU - Beck, R.

AU - Bekrenev, V.

AU - Berghauser, H.

AU - Braghieri, A.

AU - Branford, D.

AU - Briscoe, W. J.

AU - Brudvik, J.

AU - Cherepnya, S.

AU - Demissie, B.

AU - Dieterle, M.

AU - Downie, E. J.

AU - Drexler, P.

AU - Fil'kov, L. V.

AU - Fix, A.

AU - Glazier, D. I.

AU - Heid, E.

AU - Hornidge, D.

AU - Howdle, D.

AU - Huber, G. M.

AU - Jahn, O.

AU - Jaegle, I.

AU - Jude, T. C.

AU - Kaeser, A.

AU - Kashevarov, V. L.

AU - Keshelashvili, I.

AU - Kondratiev, R.

AU - Korolija, M.

AU - Kruglov, S. P.

AU - Krusche, B.

AU - Kulbardis, A.

AU - Lisin, V.

AU - Livingston, K.

AU - MacGregor, I. J. D.

AU - Maghrbi, Y.

AU - Mancell, J.

AU - Manley, D. M.

AU - Marinides, Z.

AU - Martinez, M.

AU - McGeorge, J. C.

AU - McNicoll, E.

AU - Mekterovic, D.

AU - Metag, V.

AU - Micanovic, S.

AU - Watts, D. P.

PY - 2014/3/10

Y1 - 2014/3/10

N2 - Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz for the photoproduction of mixed-charge pion pairs in the reactions gamma p -> n pi(0)pi(+) off free protons and gamma d -> (p)p pi(0)pi(-) and gamma d -> (p)n pi(0)pi(+) off quasi-free nucleons bound in the deuteron for incident photon energies up to 1.4 GeV. Circularly polarized photons were produced from bremsstrahlung of longitudinally polarized electrons and tagged with the Glasgow-Mainz magnetic spectrometer. The charged pions, recoil protons, recoil neutrons, and decay photons from pi(0) mesons were detected in the 4 pi electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. Using a complete kinematic reconstruction of the final state, excellent agreement was found between the results for free and quasi-free protons, suggesting that the quasi-free neutron results are also a close approximation of the free-neutron asymmetries. A comparison of the results to the predictions of the Two-Pion-MAID reaction model shows that the reaction mechanisms are still not well understood, in particular at low incident photon energies in the second nucleon-resonance region.

AB - Beam-helicity asymmetries have been measured at the MAMI accelerator in Mainz for the photoproduction of mixed-charge pion pairs in the reactions gamma p -> n pi(0)pi(+) off free protons and gamma d -> (p)p pi(0)pi(-) and gamma d -> (p)n pi(0)pi(+) off quasi-free nucleons bound in the deuteron for incident photon energies up to 1.4 GeV. Circularly polarized photons were produced from bremsstrahlung of longitudinally polarized electrons and tagged with the Glasgow-Mainz magnetic spectrometer. The charged pions, recoil protons, recoil neutrons, and decay photons from pi(0) mesons were detected in the 4 pi electromagnetic calorimeter composed of the Crystal Ball and TAPS detectors. Using a complete kinematic reconstruction of the final state, excellent agreement was found between the results for free and quasi-free protons, suggesting that the quasi-free neutron results are also a close approximation of the free-neutron asymmetries. A comparison of the results to the predictions of the Two-Pion-MAID reaction model shows that the reaction mechanisms are still not well understood, in particular at low incident photon energies in the second nucleon-resonance region.

KW - DOUBLE-PION-PHOTOPRODUCTION

KW - TAGGED PHOTON SPECTROMETER

KW - CROSS-SECTION MEASUREMENT

KW - 2ND RESONANCE REGION

KW - PI(0) PHOTOPRODUCTION

KW - BARYON RESONANCES

KW - PARTIAL-WAVE

KW - MICROTRON

KW - THRESHOLD

KW - DEUTERON

U2 - 10.1140/epja/i2014-14054-5

DO - 10.1140/epja/i2014-14054-5

M3 - Article

SN - 1434-6001

VL - 50

JO - The European Physical Journal A (EPJ A)

JF - The European Physical Journal A (EPJ A)

IS - 3

M1 - 54

ER -

Measurement of the beam-helicity asymmetry I-circle dot in the photoproduction of pi(0)pi(+/-) pairs off protons and off neutrons

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Keywords / Materials (for Non-textual outputs)

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