We calculate the hypertriton binding energy and the d and d scattering lengths using baryon-baryon interactions obtained from a chiral constituent quark model. We study consistently the N N and NN systems by analyzing the effect of the ↔ conversion. Our interactions correctly predict the hypertriton binding energy. The (I, J ) = (0, 3/2) N N channel is also attractive and it might have a bound state. From the condition of nonexistence of a (0,3/2) N N bound state, an upper limit for the spin-triplet N scattering length is obtained. We also present results for the elastic and inelastic N and N cross sections. The consistent description of the N scattering cross sections imposes a lower limit for the corresponding spin-triplet scattering lengths. In the NN system the only attractive channels are (I, J ) = (1, 1/2) and (0, 1/2), the (1, 1/2) state being the most attractive one.
We present a systematic and selfconsistent analysis of four-quark charmonium states and applied it to study compact four-quark systems and meson-meson molecules. Our results are robust and should serve to clarify the situation of charmonium spectroscopy above the threshold production of charmed mesons.PACS numbers: 14.40. Gx,21.30.Fe,12.39.Mk Understanding of charmonium spectroscopy is challenging for experimentalists and theorists alike. Charmonium has been used as the test bed to demonstrate the color Fermi-Breit structure of quark atoms obeying the same principles as ordinary atoms [1]. Its nonrelativistic character (v/c ≈ 0.2 − 0.3) gave rise to an amazing agreement between experiment and simple quark potential model predictions as cc states [2]. The opening of charmed meson thresholds was expected to modify the trend in the construction of quark-antiquark models. In the adiabatic approximation meson loops were absorbed into the static interquark potential. Thus, close to the threshold production of charmed mesons models required of an improved interaction [3]. The corrections introduced to the quark-antiquark spectra explained some deviations observed experimentally [4]. . These new states do not fit, in general, the simple predictions of the quark-antiquark schemes and, moreover, they overpopulate the expected number of states in (simple) two-body theories. This situation is not uncommon in particle physics. For example, in the light scalar-isoscalar meson sector hadronic molecules seem to be needed to explain the experimental data [6][7][8]. Also, the study of the N N system above the pion production threshold required new degrees of freedom to be incorporated in the theory, either as pions or as excited states of the nucleon, i.e., the ∆ [9, 10]. This discussion suggests that charmonium spectroscopy could be rather simple below the threshold production of charmed mesons but much more complex above it. In particular, the coupling to the closest (cc)(nn) system, referred to as unquenching the naive quark model [11], could be an important spectroscopic ingredient. Besides, hiddencharm four-quark states could explain the overpopulation of quark-antiquark theoretical states. Thus, the new experimental discoveries are offering exciting new insights into the subtleties of the strong interaction.In an attempt to disentangle the role played by multiquark configurations in the charmonium spectroscopy we have obtained an exact solution of the four-body problem based on an infinite expansion of the four-quark wave function in terms of hyperspherical harmonics [12]. The method is exact but is not completely adequate to study states that are close to, but below, the charmed meson production threshold. Such states are called molecular, in the sense that they can be exactly expanded in terms of a single singlet-singlet color vector. Close to a threshold, methods based on a series expansion fail to converge since arbitrary large number of terms are required to determine the wave function. From our analysis, we conclud...
Using the two-body interactions obtained from a chiral constituent quark model, we study all N N and NN states with I = 0, 1, 2 and J = 1/2, 3/2 at threshold, taking into account all three-body configurations with S and D wave components. We constrain further the limits for the N spin-triplet scattering length a 1/2,1 . Using the hypertriton binding energy, we find a narrow interval for the possible values of the N spin-singlet scattering length a 1/2,0 . We find that the NN system has a quasibound state in the (I, J ) = (1, 1/2) channel very near threshold with a width of about 2.1 MeV.
We use two-body potentials derived from a constituent quark cluster model to analyze the bound-state problem of the ΣN N system. The observables of the two-body subsystems, N N and ΣN , are well reproduced. We do not find ΣN N bound states, but there are two attractive channels with a resonance close above the three-body threshold. These channels are the (I, J) = (1, 1/2) and (0, 1/2), their quantum numbers, widths and energy ordering consistent with the recently measured strange tribaryons from the 4 He(K
The Lambda_c(2286)-N system is studied in a chiral constituent quark model and the resulting s-wave interaction is used in separable form within three-body models of the pi-Lambda_c-N system with quantum numbers (C,I,JP)=(+1,3/2,2+). Separable interactions are also used for the dominant p-wave pion-baryon channels dominated by the Delta(1232) and Sigma_c(2520) resonances. Faddeev equations with relativistic kinematics are solved on the real axis to search for bound states and in the complex plane to search for three-body resonances. Some of the models considered generate a very narrow bound state, requiring isospin violation for its strong decay. Other models lead to a narrow resonance (Gamma < 0.4 MeV) for resonance mass below the Sigma_c(2455)-N threshold. This would be the lowest-lying C=+1 dibaryon, with mass estimated approximately as 3370+/-15 MeV.Comment: 12 pages, 2 figures, 4 tables, v2--corrected typos and references, to be published in Phys. Rev.
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