Abstract:
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Narrow highly excited states with halfwidth of $\Gamma \approx
0.4$ MeV have been recently detected [1] in nuclei formed in pickup
reactions $A_1(d,^3He)A_2^*$. They were observed in kinetic energy spectra
of $^3$He ejectiles. The measurements were performed with targets of
$^{116,120,124}$Sn isotopes in recoil-free kinematics. The last requires
for the two-body reaction $m_1+A_1 -->m_2+A_2^* $ the proper projectile
momentum
\begin{eqnarray}
p_1=\sqrt{[\Delta^2 -(m_1+m_2)^2] [\Delta^2 -(m_1-m_2)^2]}c/(2 \Delta)
\end{eqnarray}
where $\Delta=A_1-A_2$ is a mass difference between nuclei $A_1$ and
$A_2$.
If one changes $^3$He ejectiles by hyperhydrogen nuclei the
possibility is opened to search for narrow highly excited states with
positive strangeness. The following tables contain examples of appropriate
reactions for experimental investigations. Projectile and ejectile kinetic
energies are also determined for excitation of $A_2^*$ at the level of 590
MeV.
Reaction $T_1$, MeV $T_2$, MeV
p +$^{120}$Sn --> $^{118}A_2^*$ +$^3H_1^{\Lambda}$ 1589 811
p +$^{120}$Sn --> $^{117}A_2^*$ +^4H_1^{\Lambda} 1248 469
$\pi^+$ + $^{120}$Sn --> $^{119}A_2^*$ +$\Lambda$ 1489 854
$K^+$ + $^{120}$Sn --> $^{119}A_2^*$ + p 280 173
$K^+$ + d --> $\Theta ^+$ + p 287 178
The last reaction is also proposed in [2].
Reaction $E_{\gamma}$, MeV $T_2$, MeV
$\gamma$ + d --> $\Theta ^+$ + $\Lambda$ 1687 907
$\gamma$ + d --> $\Theta ^+$ + $\Lambda$ 1181 400
$\gamma$ + $^{120}$Sn --> $^{119}A_2^*$+$\Lambda$ 1675 987
$\gamma$ + $^{120}$Sn --> $^{119}A_2^*$+$^3_1H^{\Lambda}$ 934 142
Processes of complex nuclear disintegrations may be closely connected with
the formation of narrow highly excited states in heavy nuclei because of
similar recoil-free kinematics [3].
References
1. K.Suzuki et al., Phys. Rev. Lett. 92 (2004) 072302.
2. A.Gal and E.Friedman, Phys. Rev. Lett. 94 (2005) 072301.
3. L.N.Andronenko et al., Phys. Atom. Nucl. 65 (2002) 478.