The pentaquark $\hat{I}{˜}^{+}(1540)$ in the string model

Abstract

We consider the $\hat{I}{˜}^{+}(1540)$ pentaquark in the string model that correctly reproduces the linear Regge trajectories for the case of orbital excitations of light $q\bar{q}$ mesons and $qqq$ baryons. Assuming (and arguing in favour of) the diquark-antiquark-diquark ($[ud]\bar{s}[ud]$) clustering of this orbitally excited object we found its mass about $290\mathrm{MeV}$ above the experimental value $1540\mathrm{MeV}$. In the model considered this discrepancy could be attributed to the change of the constituent mass of $\bar{s}$ antiquark as compared to that of $s$ quark localized at the string end.

4 pages, 5 figures