Spin resonances can depolarize or spin flip a polarized beam. We studied 1st and higher order spin resonances with stored $2.1\mathrm{GeV}/c$ vertically polarized protons. The 1st order vertical (${\nu }_y$) resonance caused almost full spin flip, while some higher order ${\nu }_y$ resonances caused partial depolarization. The 1st order horizontal (${\nu }_x$) resonance caused almost full depolarization, while some higher order ${\nu }_x$ resonances again caused partial depolarization. Moreover, a 2nd order ${\nu }_x$ resonance is about as strong as some 3rd order ${\nu }_x$ resonances, while some 3rd order ${\nu }_y$ resonances are much stronger than a 2nd order ${\nu }_y$ resonance. One thought that ${\nu }_y$ spin resonances are far stronger than ${\nu }_x$, and that lower order resonances are stronger than higher order; the data do not support this.

• Received 25 April 2011

DOI:https://doi.org/10.1103/PhysRevLett.108.074801