I=32 πNResonances in the 1900-MeV Region

Abstract

We report results of a TTN partial-wave analysis for I =| resonances observed in the 1900-MeV region: ^3 5 (1885), F 37 (1945), P 31 (1940), and D 35 (1925). The D 35 (1925) is difficult to accommodate in conventional baryon models; we discuss an alternative model having such a state.The SU(6)xO(3) harmonic-oscillator model proposed by Greenberg, 1 its relativistic 2 and diquark 3 variations, and recent "dual string" 4 and "bag" 5 models have had notable success in reproducing the observed baryon mass spectrum. Primary information to test such models comes from partial-wave analyses. We report here initial results of a TTN partial-wave analysis between 1550 and 2150 MeV. We concentrate on resonances observed in the F 359 F 37 , P 31 , and D 35 partial waves around 1900 MeV. The even-parity states at this mass are placed by harmonic-oscillator quark models in a (5£, 2 + ) SU(6)xO(3) supermultiplet. 6 However, the odd-parity D 35 (1925) is not readily accommodated by such models. We have performed additional tests which support the existence of the i)3 5 (1925), and present a model which provides a D 35 resonance at this energy.World up elastic and charge-exchange scattering data were amalgamated at 26 momenta in the range 0.8 ^/> lab < 2.0 GeV/c. The amalgamated data were partial-wave analyzed by a combination of the accelerated convergence expansion (ACE) technique for an energy-independent fitting and a hyperbolic dispersion technique for the resolution of ambiguities and the imposition of s-channel analyticity constraints. The amalgamation took into account normalization errors, momentum calibration errors, discrepancies between experiments, correlated interpolation errors, and other systematic effects. 7 Single-energy fits to these data were made using a parametrization with each invariant amplitude represented as a sum of a fixed "Born term" and a fitted polynomial term constructed according to the ACE prescription. 8 The Born term contains contributions from Pomeron and peripheral di-pion exchange, 9 and also from Reggeized p, /, N, and A exchange. The parametrization 10 is analytic in the cut cos8 plane, with asymptotic power behavior (cos9) a{s) for large |cos#|, and has no sharp cutoff in angular momentum. At each momentum, depending on the completeness of data, there were three to fifteen clusters of statistically indistinguishable local x 2 minima. The covariance matrix estimated for each cluster includes the spread within the cluster.To resolve ambiguities the reconstructed invariant amplitudes along four hyperbolic curves in the physical region of the s-t plane (supplemented by results of Carter et al. 11 and Ayed and Bareyre 12 outside our energy range) were fitted with a parametrization based on hyperbolic dispersion relations (HDR). 13 The HDR fit selected a unique cluster at each energy. To check and further stabilize these results, the input amplitudes at each energy in turn were deleted and HDR predictions were generated. These predictions, with enlarged errors, were then combined with the scat...

Systematics of the SU(3) Baryon Spectra and Deformed Oscillator Quark Model

“…There are works on this state by Cutkosky and Hendrick 23) and Bowler et al, 24) where the possibility of a quark-gluon hybrid state is discussed. §4.…”

The baryonic spectrum in a constituent quark model including a three-body force

“…Due to difficulties in reproducing some helicity amplitudes relative to 7-decay, it has been suggested that some low energy states such as the Roper resonance (again) or the states P~ at 1710MeV and PJ3 at 1730 MeV be hybrid states [9]. Such an explanation has also been suggested for the state A (5/2-) at 1930 MeV which is relatively quite low in energy [ 10].…”

Pion-nucleon form factor in the Chew-Low theory

“…3 A. i+-mr d&1 + 2(pt)p 31 (P') (A14) Thus, in the absence of crossing symmetry, the = (1+f '~m ')+LMM' (&) This result can also be derived by comparing the inverse problem for v'(p) in the potential model of Ref. 2 with the Chew-Low inverse problem developed here.…”

“…It is possible to completely eliminate the multimeson matrix elements which appear explicitly in (2.2) (11,13 and 31,33), (2,9) wl (2.13) known dependence on p and p' and one having a complicated dependen. ce on co, (p~T( )~p)= "" , ""'.…”