Measurement of the Spin Tune Using the Coherent Spin Motion of Polarized Protons in a Storage Ring.

This Letter reports the first spin tune measurement at high energies (24 and 255 GeV) with a driven coherent spin motion. To maintain polarization in a polarized proton collider, it is important to know the spin tune of the polarized proton beam, which is defined as the number of full spin precessions per revolution. A nine-magnet spin flipper has demonstrated high spin-flip efficiency in the presence of two Siberian snakes [H. Huang et al., Phys. Rev. Lett. 120, 264804 (2018).10.1103/PhysRevLett.120.264804]. The spin flipper drives a spin resonance with a given frequency (or tune) and strength. When the drive tune is close to the spin tune, the proton spin direction is not vertical anymore, but precesses around the vertical direction. By measuring the precession frequency of the horizontal component, the spin tune can be precisely measured. A driven coherent spin motion and fast turn-by-turn polarization measurement are keys to the measurement. The vertical spin direction is restored after turning the spin flipper off and the polarization value is not affected by the measurement. The fact that this manipulation preserves the polarization makes it possible to measure the spin tune during the operation of a high energy accelerator.

[1]  An absolute polarimeter for high energy protons , 2001, hep-ph/0107013.

[2]  M. Tigner,et al.  Handbook of Accelerator Physics and Engineering , 2013 .

[3]  J. Kewisch,et al.  High Spin-Flip Efficiency at 255 GeV for Polarized Protons in a Ring With Two Full Siberian Snakes. , 2018, Physical Review Letters.

[4]  T. Roser,et al.  Full spin flipping in the presence of full Siberian Snake , 2008 .

[5]  A. Skrinsky,et al.  RADIATIVE POLARIZATION: OBTAINING, CONTROL, USING , 1978 .

[6]  B. Smith,et al.  Measurement of analyzing power for proton-carbon elastic scattering in the coulomb-nuclear interference region with a 22-GeV/c polarized proton beam. , 2002, Physical review letters.

[7]  W. J. Womersley,et al.  A measurement of the spin asymmetry and determination of the structure function g1 in deep inelastic muon-proton scattering , 1988 .

[8]  T. Roser,et al.  Electron-Ion Collider: The next QCD frontier , 2012, The European Physical Journal A.

[9]  Tepikian,et al.  Resonance due to a local spin rotator in high-energy accelerators. , 1986, Physical review letters.

[10]  A. Poblaguev,et al.  RHIC Polarized Proton Operation for 2013 , 2017 .

[11]  T. Roser,et al.  Spin tune dependence on closed orbit in RHIC , 2010 .

[12]  Longitudinal double-spin asymmetries for dijet production at intermediate pseudorapidity in polarized pp collisions at s=200  GeV , 2018, Physical Review D.

[13]  C Wilkin,et al.  New Method for a Continuous Determination of the Spin Tune in Storage Rings and Implications for Precision Experiments. , 2015, Physical review letters.

[14]  K. Kurita,et al.  Fiddling Carbon Strings with Polarized Proton Beams , 2006 .

[15]  T. Trueman.  Spin asymmetries for elastic proton scattering and the spin dependent couplings of the Pomeron , 2007, 0711.4593.

[16]  M. Berz,et al.  Phase Locking the Spin Precession in a Storage Ring. , 2017, Physical review letters.

[17]  E. Courant,et al.  Polarized proton collider at RHIC , 2003 .

[18]  Jr.,et al.  Measurements of double-helicity asymmetries in inclusive $J/\psi$ production in longitudinally polarized $p+p$ collisions at $\sqrt{s}=510$ GeV , 2016, 1606.01815.

[19]  R. Maier,et al.  Cooler synchrotron COSY — Performance and perspectives , 1997 .

[20]  Alexander Wu Chao,et al.  Handbook of Accelerator Physics and Engineering: (3rd Printing) , 1999 .

[21]  S. Lee.  Spin Dynamics and Snakes in Synchrotrons , 1997 .

[22]  J. Kewisch,et al.  Minimization of spin tune spread by matching dispersion prime at RHIC , 2017 .

[23]  P. Alam.  ‘S’ , 2021, Composites Engineering: An A–Z Guide.