References - Bogoliubov Laboratory of Theoretical Physics - JINR

not even resemble the data behavior. Good agreement with earlier ITEP results [6] in the
overlapping region proofs the data quality. A narrow local minimum at 157 o confirmed by
two independent measurements indicates the significant presence of a partial wave with
high orbital momentum L ≈ 8 − 9. The sharp step at 167 o in 1.78 GeV/c data may have
similar interpretation.
In both cases with π − p scattering the latest solution SP06 of the GWU group is not
the closest to the new data. In the lower energy domain (see fig. 4a for π + p at 0.80 GeV/c)
the data are best described by this very solution. CMB80 does not show the sharp peak at
175 o implied by the data, while SM95 gives much smaller asymmetry values. Our results
obviously contradict to the 3 rightmost points from [7] at two adjacent energies.
π + p asymmetry at 1.94 GeV/c shows large negative values around 165 o (fig. 4b). Neither
of the solutions manifest so deep a minimum though all but CMB80 have qualitatively
similar behavior. The closest prediction in this case is from KH80.
The cross section for backward angles at 2.07 GeV/c is extremely low for positive
pions. Our data are not much better statistically than that from previous works and
feature high background levels. The angular dependence of the data most resemble the
curve from CMB80 (fig. 4c). All other solutions show qualitatively different behavior
though KH80 and SM95 are not beyond 3σ boundary of the data.
The obtained results show that in some kinematic areas one or both of the ”classic”
partial wave analysis CMB80 and KH80 are in disagreement with the new data. In some
cases even the qualitative behavior of mentioned PWA does not correspond to that of
the data, which may indicate the wrong choice of the solution branch by these analysis
and, consequently, wrong extraction of baryon properties. The latest solution SP06 of
GWU group seems to be consistent with the data in the lower energy domain, while in
the momentum region above 1.8 GeV/c it’s behavior looks unstable.
The ITEP-PNPI team believes that their new data notably improves the experimental
database for partial wave analysis and becomes a significant step towards reliable light
baryon spectrum.
We are grateful to the ITEP accelerator staff for providing us with excellent beam conditions.
The work was partially supported by Russian Fund for Basic Research (grants
02-02-16121-a and 04-02-16335-a), Russian State Corporation on the Atomic Energy
’Rosatom’ and Russian State program ”Fundamental Nuclear Physics”.
References
[1] G. Höehler et al., πN-Newsletter 9 (1993) 1.
[2] R.E. Cutcosky et al., Phys.Rev.D20 (1979) 2839.
[3] R.A. Arndt et al., Phys.Rev.C52 (1995) 2120.
[4] R.A. Arndt et al., Phys.Rev.C74 (2006) 045205.
[5] Yu.A. Beloglazov et al., Instrum. Exp. Tech. 47 (2005) 744.
[6] I.G. Alekseev et al., Nucl.Phys.B348 (1991) 257.
[7] J.E. Martin et al., Nucl.Phys.B89 (1975) 253.
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