Thomas Roser Snowmass 2001 June 30 - July 21, 2001 Polarized Proton Acceleration and Collisions Spin dynamics and Siberian Snakes Polarized proton acceleration in AGS and RHIC Possible RHIC proton-proton luminosity upgrades Polarized proton acceleration in HERA

RHIC Spin Physics Spinning Proton Spinning Quarks or Gluons Quark, Gluon, Photon, Electron or Neutrino from W or Z Decay Spin structure functions of gluon and anti-quarks Parity violation in parton-parton scattering

Spin Dynamics Precession Equation in Laboratory Frame: (Thomas [1927], Bargmann, Michel, Telegdi [1959]) dP/dt = - (e/  m) [G  B  + (1+G) B  ]  P Lorentz Force equation: dv/dt = - (e/  m) [ B  ]  v For pure vertical field: Spin rotates G  times faster than motion, sp = G  For spin manipulation: At low energy, use longitudinal fields At high energy, use transverse fields

Depolarizing Spin Resonances Spin tune: Number of 360 degree spin rotations per turn Depolarizing resonance condition: Number of spin rotations per turn = Number of spin kicks per turn Imperfection resonance (magnet errors and misalignments): G  = sp = n Intrinsic resonance (Vertical focusing fields): G  = sp = Pn ± y P: Superperiodicity [AGS: 12] y : Betatron tune [AGS: 8.75]

Siberian Snakes (Local Spin Rotators) cos(180  sp ) = cos(  /2) · cos(180  G  )   0   sp  n No imperfection resonances Partial Siberian snake (AGS)  = 180   sp = ½ No imperfection resonances and No Intrinsic resonances Full Siberian Snake Two Siberian Snakes in RHIC

(Naïve) Limits for Siberian Snakes Spin rotation of Siberian snake > Spin rotation of driving fields Imperfection resonances   Energy Intrinsic resonances    Energy Partial Siberian snake (AGS,  = 9  )  =  /360  One full snake  = 1/2 Two full snakes (RHIC)  = 1 N full snakes (HERA, LHC)  = N/2

BRAHMS & PP2PP (p) STAR (p) PHENIX (p) AGS LINAC BOOSTER Polarized proton collisions in RHIC Pol. Proton Source 500  A, 300  s Spin Rotators Partial Siberian Snake Siberian Snakes 200 MeV Polarimeter AGS Internal Polarimeter Rf Dipoles RHIC pC Polarimeters Absolute Polarimeter (H jet) 2  Pol. Protons / Bunch  = 20  mm mrad

High intensity polarized H - source KEK OPPIS upgraded at TRIUMF % Polarization 15  protons/pulse at source 6  protons/pulse at end of LINAC

Proton polarization at the AGS Full spin flip at all imperfection resonances using partial Siberian snake Full spin flip at strong intrinsic resonances using rf dipole Remaining polarization loss from coupling and weak intrinsic resonances New tune working point and smaller horizontal emittance will reduce polarization loss

First Siberian Snake in RHIC Tunnel Siberian Snake: 4 superconducting helical dipoles, 4Tesla, 2.4 m long with full 360  twist Funded by RIKEN, Japan Designed and constructed at BNL

Commissioning with a single snake in RHIC snake polarimeter -12º G  = 46.5 or 55.7 G  = 48 or 60.3 Inject vertically pol. beam with snake off Turn on snake  Horizontally pol. beam Accelerate

Polarized proton injection into RHIC Sensitive to betatron tune setting y = Injection at G  = 46.5 without snake: vertical polarization! y = 29.23

Snake operating points Single snake RUN2000 B1 = B2 Two snakes for RUN2001

Acceleration with single snake G  =46.5 G  =48.0 G  =55.7 G  =60.3

Measured RHIC asymmetries Asymmetry (  ) GG P  19 % P  40 % at AGS GeV

Spin resonances in RHIC (w/o Snakes) Inj. Energy G  = 46.5 E = 24.3 GeV G  = 48 G  = 55.7 E = 29.1 GeV G  = 60.3 E = 31.5 GeV

Spin tracking with single snake (single particle) Longitudinal beam polarization opposite of snake Radial beam polarization at the polarimeter rms orbit distortions: ___ 0 mm ___ 1 mm ___ 2 mm Need well corrected orbit! Strong spin resonance

Typical closed orbits at injection Before correction After correction

Spintracking trough strongest RHIC resonance Two Siberian snakes 1 mm rms misalignment (Survey: < 0.5 mm) 0.2 mm rms closed orbit 20   m emittance (95%) (~ 10   m in RUN2000 ) Whole beam Edge particle

Polarized proton status and plans (1) FY2000 run: l Single Siberian snake and pC polarimeter installed in blue ring l New polarized proton source: ~ pol. protons/pulse l Accelerated polarized beam in blue ring FY2001/ FY2002 run: l All four Snakes and pC polarimeters installed in blue and yellow ring Goal: 100 GeV  100 GeV collision with long. pol. at interaction regions Accelerate with two Snakes Collide beams with one Snake per ring for longitudinal polarization Polarization:  50 % protons per bunch; 60 bunches;  * = 2 m; L = 5  cm -2 s -1 Integrated luminosity per week : 1.5 (pb) -1 (50% availability) Accelerate polarized beam to 250 GeV

Polarized proton status and plans (2) FY2003 run: l All eight spin rotators installed l Goal: 250 GeV  250 GeV collision with long. pol. at STAR and PHENIX FY2004 run: l Polarized hydrogen jet target for absolute polarimetry installed

Luminosity Upgrades RHIC SpinRHIC IIFuture Upgrade Emittance(95%)  m Beta function at IR [m]110.3 Number of bunches Bunch population [10 11 ]222 Beam-beam parameter per IR Angular size at IR [  rad] RMS beam size at IR [  m] Luminosity [10 32 cm -2 s -1 ] RUN2000: Au-Au luminosity: 3.3  cm -2 s -1 [N-N luminosity ~ cm -2 s -1 ] RHIC II : Beam-beam tune shift limited for 2 interaction regions Future Upgrade: Mini-beta quads and more bunches Will also require major detector upgrades

Polarized protons in HERA Difficulties for polarized protons in HERA Not perfect symmetry Vertical bends (Remedy: flattening Snakes) Not built for polarization Hardly space for more than 4 Siberian Snakes Very high energy (920 GeV) and spin tune (1758)

Invariant spin field

Requirements and installation

Summary l Very successful first RHIC spin commissioning run: n RHIC Polarimeter commissioned n Single Siberian snake works l With two snakes per ring and improved tune and orbit control during acceleration expect 100 GeV on 100 GeV polarized proton collisions this year. l Collisions of polarized protons at 500 GeV and 2  cm -2 s -1 possible by FY2004 l Luminosity upgrade for RHIC possible to 4  cm -2 s -1