p−presonances: A link between nuclear and hadronic excitations

Abstract

Evidence of resonant behavior has recently been discovered in p-p scattering, and possibly also in n-p scattering. In particular, the p-p data indicate the existence of 'D,, 3F,, and 'G, resonances at energies of approximately 2140, 2260, and 2430 MeV. The correlation between increasing 1 values and increasing energies that is observed in these resonances suggests a form of rotational motion. Since a virtually boutld nucleon-nucleon state represents the low-mass limit of a multinucleon (nuclear) system, we logically expect the rotational behavior of this dinucleon state to follow the known systematics of nuclear physics. The rotational motion is highly nonadiabatic for this very light dinucleon system, so that an l(1 + 1) energy interval rule is expected to apply, where 1 is the orbital angular momentum quantum number. In support of this idea, we show experimental data plots which reveal that (1) rotational bands in very light nuclei and in the dinucleon follow the expected l(1 + 1) interval rule, and (2) the experimental moments of inertia of the rotating bandheads exhibit the expected A behavior, where A is the atomic weight. We can extend these concepts even farther by formally sorting the observed baryon and meson resonances into nonadiabatic rotational bands. When we do this, we discover that the experimental moments of inertia of these hadron rotational bands, plotted as a function of the bandhead masses, extrapolate smoothly into the moments of inertia of the very light atomic nuclei. Applying the 1(1 + 1) energy interval rule to the observed 'D,, %,, and 'G, p-p resonances, and then extrapolating to 1 = 0 to obtain the mass of the unobserved p-p bandhead, we discover that it corresponds to a virtual ppw bound state, which is a characteristic hadronic excitation. Hence the p-p resonances form a direct and unique experimental link between nuclear and hadronic excitations: The p-p rotational levels, which are nuclear in origin, can be used to pinpoint the mass of the p-p bandhead excitation, which is hadronic in origin. The CLL, AmL, and A u , measurements carried out at Argonne are crucial in the identification of these rather weak p-p resonances. Unfortunately, the low-energy limit of these Argonne measurements falls above the predicted energy values of the, (unobserved) 1 = 0 and 1 = 1 levels in the p-p rotational band. Thus the present results suggest the usefulness of extending the CLL, A u L , and A u , experiments at Argonne from the present lower limit of 1.0 G e V / c down to at least 0.8 GeV/c.

$P$-wave dibaryon resonances in $pp$ elastic scattering and near-threshold pion production

“…., respectively. 6 Most of these isovector dibaryons have been detected to date, except for the 3 P 1 resonance which should have the mass of about 2.07 GeV to fit into the above trajectory [48]. On the other hand, in the present study we have obtained the 3 P 1 dibaryon resonance with the mass M th ( 3 P 1 ) = 2230 MeV, i.e., close to the 3 P 0 and 3 P 2 resonances found experimentally.…”

“…[46], the resonance state with the mass M ( 3 P 1 ) = 2179 MeV and the width Γ( 3 P 1 ) = 86 MeV was found from the PWA of pp scattering. At the same time, the hypothetical 3 P 1 dibaryon state with the mass M ( 3 P 1 ) ≃ 2.07 GeV can be considered as a member of the Regge trajectory for isovector dibaryons [48]. The resonance with the same mass was also mentioned in Ref.…”

“…In this way, we can describe the whole isovector trajectory 1 S 0 , 3 P 1 , 1 D 2 , 3 F 3 , 1 G 4 , etc., considered in Ref. [48] as rotational excitations in the N N system, by a rotating color string between the 4q and 2q clusters with the orbital angular momenta L = 0, 1, 2, . .…”

“…However, some indications of its existence can be found in the literature (see, e.g., Refs. [46][47][48][49]). Thus, for consistency of our study of P -wave pp scattering within the dibaryon model, we present below the results of calculations for the 3 P 1 partial channel as well.…”

Hidden dibaryons in one- and two-pion production in NN collisions

“…It is interesting to note that in some previous works (see, e.g., [123]) the same isovector dibaryons were considered as lying on a rotational band in the NN system, in the spirit of rotational bands in nuclear physics. It was found [123] that the trajectory of isovector dibaryons on the graph [L N N (L N N + 1), M D ], where L N N = L + 2 = J, is also rather close to a straight line. However, since the dibaryons are known to be highly inelastic in the NN channel, the description in terms of quark clusters [q 4 − q 2 ] rather than [N − N] looks to be more appropriate.…”