Pairing effect on critical spin in chiral rotation

The critical spin I-c (or critical frequency (h) over bar omega(c)) represents the minimum spin (or rotational frequency) required for stable chiral solutions in nuclear systems. The effect of pairing on the critical spin has been examined for the particle -hole configuration pi(1h(11/2)) circle times v(1(11/2))(-1) with a triaxial deformation parameter of y = 30 degrees using the particle rotor model, which treats the total angular momentum as a good quantum number. Increasing pairing interaction keeps the critical spin I-c constant, but decreases the critical rotational frequency (h) over bar omega(c). This is due to that the enhanced pairing interaction causes valence nucleons angular momenta to align preferentially along the medium axis, resulting in a larger effective collective moment of inertia and facilitating the emergence of chiral rotation at a lower frequency. However, even with an increase in pairing gap from 0.0 to 2.0 MeV, the resulting increase in medium axis alignment is less than 1 (h) over bar, which is insufficient to change the value of the critical spin I-c. This study suggests that the critical spin remains robust against the influence of pairing interaction.