Pion photoproduction in the <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Δ</mi></math></span> resonance region

R. A. Arndt; I. I. Strakovsky; R. L. Workman

doi:10.1103/PhysRevC.56.577

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Pion photoproduction in the $Δ$ resonance region

R. A. Arndt, I. I. Strakovsky, and R. L. Workman

Department of Physics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061

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Phys. Rev. C 56, 577 – Published 1 July, 1997

DOI: https://doi.org/10.1103/PhysRevC.56.577

Abstract

We have updated our multipole analyses to incorporate new data from the low-energy and $Δ$ resonance regions. We note a slight decrease in our estimate of the $Δ$ photodecay amplitudes. This agrees with results found in Compton scattering. Our values are also in good agreement with another previous determination. We have reexamined our determinations of the $E 2 / M 1$ ratio at the resonance energy and at the pole. We find an $E 2 / M 1$ ratio (at the pole) which is in good agreement with the recent Mainz value.

References (15)

R.A. Arndt, I.I. Strakovsky, and R.L. Workman, Phys. Rev. C 53, 430 (1996).
M. MacCormick et al., Phys. Rev. C 53, 41 (1996).
J. Peise et al., Phys. Lett. B 384, 37 (1996).
R.L. Crawford and W.T. Morton, Nucl. Phys. B211, 1 (1983).
R.M. Davidson, N.C. Mukhopadhyay, and R.S. Wittman, Phys. Rev. D 43, 71 (1991).
These solutions can be viewed using SAID with a TELNET call to clsaid.phys.vt.edu with userid: said, or through our WWW site at http://clsaid.phys.vt.edu.
R.L. Workman, R.A. Arndt, and Z. Li, Phys. Rev. C 46, 1546 (1992).
R.M. Barnett et al., Phys. Rev. D 54, 1 (1996).
M. Khandaker and A.M. Sandorfi, Phys. Rev. D 51, 3966 (1995).
A.M. Sandorfi (private communications).
R. Beck et al., Phys. Rev. Lett. 78, 606 (1997). There appears to be a typographical error in Eq. (4) of this paper. The signs of the $M_{1 +}$ and $M_{1 -}$ multipoles should be reversed.
O. Hanstein, D. Drechsel, and L. Tiator, Phys. Lett. B 385, 45 (1996).
A number of our earlier solutions predict the Mainz data [11] with a $χ^{2}$ /data near unity. The solution SM95 [6] actually gives a $χ^{2}$ /data of 168/182 for this data set. This explains why our result for the $E 2 / M 1$ ratio was not greatly influenced by the Mainz experiment.
We expect the ratio of pole residues to be less model dependent than the individual residues for $E 2$ and $M 1$ . If one assumes a factorizable pole [see, for example, R.A. Arndt et al., Phys. Rev. C 42, 1864 (1990)], the pion-nucleon residue cancels in the ratio. In a representative fit with the ratio (modulus, phase) of (0.065, $- 126 °)$ , we found (1.33, $- 152 °)$ and (20.5, $- 26 °)$ for the $E 2$ and $M 1$ residues, in the units (10 $^{- 3}$ /m $_{π})$ of Ref. [12].
L. Tiator has claimed a value of $- 2.4 %$ for the $E 2 / M 1$ ratio at the resonance energy, using the amplitudes of Ref. [12]. A comparison of the resonant and pole values from several sources was given during the N $^{*}$ meeting at INT, Seattle, 1996, edited by T.-S.H. Lee and W. Roberts (World Scientific, Singapore, in press).

[c1] R.A. Arndt, I.I. Strakovsky, and R.L. Workman, Phys. Rev. C 53, 430 (1996).

[c2] M. MacCormick et al., Phys. Rev. C 53, 41 (1996).

[c3] J. Peise et al., Phys. Lett. B 384, 37 (1996).

[c4] R.L. Crawford and W.T. Morton, Nucl. Phys. B211, 1 (1983).

[c5] R.M. Davidson, N.C. Mukhopadhyay, and R.S. Wittman, Phys. Rev. D 43, 71 (1991).

[c6] These solutions can be viewed using SAID with a TELNET call to clsaid.phys.vt.edu with userid: said, or through our WWW site at http://clsaid.phys.vt.edu.

[c7] R.L. Workman, R.A. Arndt, and Z. Li, Phys. Rev. C 46, 1546 (1992).

[c8] R.M. Barnett et al., Phys. Rev. D 54, 1 (1996).

[c9] M. Khandaker and A.M. Sandorfi, Phys. Rev. D 51, 3966 (1995).

[c10] A.M. Sandorfi (private communications).

[c11] R. Beck et al., Phys. Rev. Lett. 78, 606 (1997). There appears to be a typographical error in Eq. (4) of this paper. The signs of the $M_{1 +}$ and $M_{1 -}$ multipoles should be reversed.

[c12] O. Hanstein, D. Drechsel, and L. Tiator, Phys. Lett. B 385, 45 (1996).

[c13] A number of our earlier solutions predict the Mainz data [11] with a $χ^{2}$ /data near unity. The solution SM95 [6] actually gives a $χ^{2}$ /data of 168/182 for this data set. This explains why our result for the $E 2 / M 1$ ratio was not greatly influenced by the Mainz experiment.

[c14] We expect the ratio of pole residues to be less model dependent than the individual residues for $E 2$ and $M 1$ . If one assumes a factorizable pole [see, for example, R.A. Arndt et al., Phys. Rev. C 42, 1864 (1990)], the pion-nucleon residue cancels in the ratio. In a representative fit with the ratio (modulus, phase) of (0.065, $- 126 °)$ , we found (1.33, $- 152 °)$ and (20.5, $- 26 °)$ for the $E 2$ and $M 1$ residues, in the units (10 $^{- 3}$ /m $_{π})$ of Ref. [12].

[c15] L. Tiator has claimed a value of $- 2.4 %$ for the $E 2 / M 1$ ratio at the resonance energy, using the amplitudes of Ref. [12]. A comparison of the resonant and pole values from several sources was given during the N $^{*}$ meeting at INT, Seattle, 1996, edited by T.-S.H. Lee and W. Roberts (World Scientific, Singapore, in press).

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Pion photoproduction in the $Δ$ resonance region

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Pion photoproduction in the Δ resonance region

Abstract

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Pion photoproduction in the $Δ$ resonance region