On the determination of $\Theta^+$ quantum numbers and other topics of exotic baryons

From the interpretation of the $\Theta^+$ baryon resonance as an excitation of the ``skyrmion liquid'' with SU(3) flavor symmetry $\bar{10}$ we deduce a new series of baryons, $\Theta_1^{++}$, $\Theta_1^{+}$ and $\Theta_1^0$, situated at the top of the 27-plet of SU(3) flavor, with hypercharge Y=2, isospin T=1 and spin $J=\frac32$. The mass of $\Theta_1$ is estimated 55 MeV/c^2 higher then the mass of $\Theta^+$ and its width at 80 MeV. We also discuss the other baryons from ...

Recently several proposals were put forward to determine the parity of narrow baryonic resonances, in particular the $\Theta^+$. In these proceedings we will briefly comment on the general problems in this task and then discuss in detail the potential of reactions of the type $\vec N\vec N\to\Theta^+Y$, where $Y$ denotes a hyperon (either $\Sigma$ or $\Lambda$) and the arrows indicate that a polarized initial state is required. Besides reiterating the model--independent prope...

We present results on the production of bound states of $\Theta^+$ in nuclei using the $(K^+,\pi^+)$ reaction. By taking into account the states obtained within a wide range of strength of the $\Theta^+$ nucleus optical potential, plus the possibility to replace different nucleons of the nucleus, we obtain an excitation spectra with clearly differentiated peaks. The magnitude of the calculated cross sections is well within reachable range.

An analysis of the recent results from several experimental groups reported observation of a new $\Theta$ baryon has been presented from a view point of the unified picture for hadron spectra developed early \cite{12}. It is shown that, in fact, two different $\Theta$ baryons have been discovered. We have also established that both $\Theta$ baryons are excellently incorporated in the unified picture for hadron spectra. It is argued that the presented experimental material rev...

The recently reported Theta(1540) exotic baryon seems to be very narrow: Gamma(Theta)< 1 MeV according to some analyses. Using methods of low energy scattering theory, we develop expectations for the width of the Theta, an elastic resonance in KN scattering in a theory where the characteristic range of interactions is ~1 Fermi. If the Theta is a potential scattering resonance, generated by the forces in the KN channel, its width is hard to account for unless the KN-channel or...

We propose that the recently discovered \Theta baryon is a bound state of four quarks and an antiquark, containing two highly correlated ud-pairs. If so, the \Theta baryon has positive parity, and it lies in an near-ideally mixed SU(3)_{f} \mathbf{\bar{10}}_{f} oplus \mathbf{8}_{f}. The Roper resonance and the P_{11}(1710) fit naturally into this classification. We predict an isospin 3/2 multiplet of \Xi's (S=-2) with J^{\Pi}=\half^{+} around 1750 MeV. A search for manifestly...

We study the selfenergy of the $\Theta^+$ pentaquark in nuclei associated with two types of interaction: the KN decay of the $\Theta^+$ and two meson baryon decay channels of the $\Theta^+$. Whereas the potential related to the first source is quite weak, the second kind of interaction produces a large and attractive potential that could lead to the existence of $\Theta^+$ nuclear bound states.

Evidence for the $\Theta^+$ pentaquark is still sketchy at the present time. This state, if it exists, has a small width and consequently a small production cross section. No single experiment has overwhelming evidence for the $\Theta^+$ and some non-observations of the $\Theta^+$ are difficult to understand unless this exotic baryon also has an exotic production mechanism. However, new data from the LEPS and CLAS collaborations with higher statistics are on the way, which wi...

Motivated by the recent experimental evidence of the exotic B = S = +1 baryonic state Theta(1540), we examine the older existing data on K+ N elastic scattering through the time delay method. We find positive peaks in time delay around 1.545 and 1.6 GeV in the D03 and P01 partial waves of K+ N scattering respectively, in agreement with experiments. We also find an indication of the J=3/2 Theta* spin-orbit partner to the Theta, in the P03 partial wave at 1.6 GeV. We discuss th...

We present results for the selfenergy of the $\Theta^+$ pentaquark in nuclei associated with two sources: the $KN$ decay of the $\Theta^+$ and the two meson baryon decay channels of the $\Theta^+$ partners in an antidecuplet of baryons. The first source is shown to produce a small potential, unable to bind the $\Theta^+$ in nuclei, while the second source gives rise to a large attractive potential. At the same time we show that the width of the $\Theta^+$ in nuclei is small, ...