Polarized beams in RHIC A.Zelenski, BNL PSTP 2011, September 12, St.Petersburg

RHIC High-Luminosity (Polarized) Hadron Collider ,31, 19.5,3.9, 5.5 GeV

RHIC: the “Polarized” Collider STAR PHENIX AGS, 24GeV LINAC BOOSTER, 2.5 GeV Pol. H - ion source Spin Rotators 20% Snake Siberian Snakes 200 MeV polarimeter RHIC pC “CNI” polarimeters RHIC Absolute H-jet polarimeter Design goal - 70% Polarization L max = 1.6  s -1 cm < √s < 500 GeV AGS pC “CNI” polarimeter 5% Snake Polarization facilities at RHIC.

Optically-Pumped Polarized H - Ion Source (OPPIS) at RHIC, (originally developed in collaboration between KEK, BNL, TRIUMF and INR Moscow). RHIC OPPIS produces reliably mA (maximum 1.6 mA) polarized H - ion current. Pulse duration 400 us. Polarization at 200 MeV P = 85-90%. Beam intensity (ion/pulse) routine operation: Source H - /pulse Linac (200MeV) - 5∙10 11 AGS - 1.7∙10 11 RHIC - 1.4∙10 11 (protons/bunch). A beam intensity greatly exceeds RHIC limit, which allowed strong beam collimation in the Booster, to reduce longitudinal and transverse beam emittances.

Schematic Layout of the RHIC OPPIS 29.2 GHz ECR proton source 29.2 GHz ECR proton source SCS solenoid Probe laser Na-jet Ionizer cell Na-jet Ionizer cell Pumping laser Cryopumps Sona-transition Rb-cell SCS -solenoid

Depopulation Optical Pumping 5S 1/2 5P 1/2 λ = 795 nm Circularly Polarized light M J = -1/2 M J = +1/2 Spontaneous decays. nL J ~ 100% polarized Rb atoms! 1.56 eV W. Happer, Rev. Mod. Phys. 44, 170 (1972) relaxation Optical pumping application is limited by available laser wavelenghes!? Recent progress in laser technology is very promising for new applications.

Optical pumping of alkali metals 2 S 1/2 5/2 3/2 F =5/2 2 P 1/2 3/2   8 Li I = 2 Li 671 nm Na 590 K 770 Rb 795 Cs 894 Fr 817 Typical polarization = 60 – 70% 381 MHz mFmF -5/2 -3/2 -1/2 1/2 3/2 5/2 Valence electron absorbs light  tranfers polarization to nucleus via hyperfine coupling

Collinear Optical Pumping polarizer at TRIUMF

Faraday rotation polarimeter of Rb vapor. Θp-optical pumping –on. Θ 0 -optical pumping -off. PD1 PD 1 =I 0 sin θ p PD 2 =I 0 cos θ p P Rb = ( θ p - θ 0 )/  θ 0 PD2 Cr:LISAF pumping laser at795 nm Rb-cell λ/2 Linear polarized probe laser beam at 780 nm.

Polarized H - ion current pulse out of 200 MeV linac. Faradey rotation polarization sinal. 500 uA cuurent At 200 MeV. 85-hole ECR Source for the maximum polarization. 400 uS 12· polarized H - /pulse.

EBIS ionizer for polarized 3 He gas (proposal). He(2S)→ He(1S) He(2S)→ He(1S) He-3 metastability- exchange polarized cell P %. Pumping laser 1083 nm. EBIS-ionizer, B~ 50 kG EBIS-ionizer, B~ 50 kG RFQ Linac Booster AGS RHIC RFQ Linac Booster AGS RHIC He-transfer line. Valve. ~50· He /pulse. 2.5·10 11 He ++ /pulse Polarization by optical pumping Ionization 1.5·10 11 He ++ /pulse

AGS Cold Snake installed. The two-snake solution provides better spin matching at injection and extraction.

PHENIX and STAR STAR STAR: Large acceptance with azimuthal symmetry Good tracking and PID Central and forward calorimetry PHENIX: High rate capability High granularity Good mass resolution and PID Limited acceptance

Intermediate bozons W ± - can be produced directly in electroweak processes in collisions of polarized proton beams of √ S= 500 GeV energy at RHIC. In this case parity-violating A L can be as large as 50% and spin-correlation can be used for studies of different flavor quark contribution to the proton spin. Sea-quarks polarization studies via intermediate boson W ± Production at RHIC, √S= 500 GeV. u d u +d  W +, d +u  W - W + Spinning Proton Spinning Quarks or Gluons Quark, Gluon, Photon, Electron or Neutrino from W or Z Decay

2013HP8 Measure flavor-identified q and  q contributions to the spin of the proton via the longitudinal-spin asymmetry of W production.  Initial 500 GeV p+p run already demonstrates W reconstruction capabilities in STAR and PHENIX, with only ~10 pb  1.  W asymmetry measurements with power to discriminate among antiquark distribution models require ~300 pb  1 and >60% polariz’n.  u and d polarizations predicted to be substantially different in many nucleon structure models.

RHIC luminosity in Run-2011 Bunch intensity ~ 1.6 *10 11 proton/bunch Peak luminosity ~1.5*10 32 cm 2 s

Polarized beam luminosity.

Foundation of the RHIC Spin Physics.  High-intensity polarized proton source.  “Siberian snakes” to preserve polarization.  P-P and P-Carbon CNI polarimeters.  Theoretical “tools”: QCD calculations.

Polarized Proton Polarimetry from the Source to RHIC energies. A polarimeter has to satisfy the following: Beam polarization monitor for Physics ( < 5 % ) Several samples over a reasonable time period, one fill Beam polarization diagnostic and Machine tuning tool Sample on demand and online, fast/within minutes Low systematic errors. A large dynamic range & Energy independence Large analyzing power, large cross section, & low background Reasonable Cost. Unlike electron polarimeters where processes are calculable, proton reactions rely on experimental verification specially at high energies.

Measuring the beam polarization In accelerators, the stable spin direction is normally vertical (up/down). We measure using a nuclear reaction in a plane that is perpendicular to the polarization direction. N L and N R are the number of scatters to the left and right. A: is the analyzing power of the reaction The statistical error in the measurement for PA << 1 is The polarimeter figure of merit (to optimize) is  A 2 u  : is the cross section of the reaction

Polarized beams at RHIC. OPPIS LINAC Booster AGS RHIC p/bunch, P ~65-70% 10∙10 11 (maximum 40∙10 11 ) polarized H - /pulse. 5∙10 11 polarized H - /pulse at 200 MeV, P=85-90% 2∙10 11 protons /pulse at 2.3 GeV Figure of merit for the double spin Asymmetry Collisions is ~ P 4 ∙L

Polarimetry at RHIC  Faraday rotation polarimeter  Lamb-shift polarimeter  200 MeV - absolute polarimeter  AGS p-Carbon CNI polarimeter  RHIC p-Carbon CNI polarimeter  RHIC - absolute H-jet polarimeter  Local polarimeters at STAR and PHENIX

SCHEMATIC LAYOUT OF THE RHIC OPPIS GHz ECR proton source 29.2 GHz ECR proton source SCS solenoid Probe laser Na-jet Ionizer cell Na-jet Ionizer cell Pumping laser Cryopumps Correction coil Sona-shield Rb-cell SCS -solenoid

Proton Lamb-shift polarimeter. H - → H + → H(2S) B=575 G La(10.2eV) nm H(2S) N + =N 0 (1+P) / 2 N - = N 0 (1-P) / 2 P=2 (N + -N - )/(N + +N - )

OPPIS Lamb-shift polarimeter. He-ionizer cell Na-cell, spin-filter and L  detector are placed inside the vacuum chamber.

Polarized injector, 200 MeV linac and injection lines. OPPIS 200 MeV polarimeter Polarization direction is adjusted vertically in the 750 keV beamline by the solenoidal spin - rotator.

Layout of the 200 MeV proton polarimeter, (2010) 16.2 deg

Polarimeters after the 200 MeV Linac p-Carbon and p-D polarimeters D-recoil arm 12 deg. Proton arms

Proton-Carbon Elastic Scattering at 200 MeV.

Measurements of the cross section and analyzing power for proton scattering from 12 C at 200 MeV. The blue (green) curves correspond to protons exiting from the ground (4.44-MeV) state. The black curve represents the sum of the two data sets. Edward J. Stephenson, 10/22/ deg ~40mb/sr ~5mb/sr ~80% Notes on the Calibration of the 200-MeV Proton Polarization

A y =99.96+/0.02%

elastic GEANT calculation of pC polarimeter for 200MeV proton beam inelastic E p =198.7MeV E p =194.3MeV

Detector and variable absorber setup for 200 MeV proton beam.

195.6 Mev Mev Counting rate (S1^S2) vs. Cu absorber thickness. ~20

Measured Analyzing Power vs length of absorber. A y (pC) =0.62+/-0.02

Measured Analyzing Power vs length of absorber Cu absorber thickness, mm A y (pC) =0.62+/-0.02 A y (pC) =0.620+/-0.005

LINAC energy measurements.  Energy measurement by calibrated bending magnet in the Linac HEBT.  Comparison with energy measurement in Booster.  Laser stripping.  Energy stability monitoring in the 200 MeV polarimeter.

Counting rate (S1^S2/S3) vs Cu absorber thickness Mev Mev ~12

Vertical detector Horizontal 12 0 detector Polarization vs current of the spin rotator.

80.85+/-0.09% /-0.019%

Summary. 1.Elastic proton-Carbon scattering (at 16.2 deg. angle) is used in a new polarimeter setup. Analyzing power at 200 MeV is 99.35%. 2.The elastic scattering is used for calibration of inclusive 12 deg. polarimeter arm: 3.Rate in 16 deg arms is ~ 10 event/pulse (12 deg ~300); 4. Ratio N(Sc1^Sc2)/N(Sc1^Sc3) is used for the beam energy monitoring. A y (pC) =0.620+/

Proton-Carbon CNI polarimeters in AGS and RHIC.

October 6-10, 2008 A.S. Belov, A. N. Zelenski, SPIN2008, USA BRAMS STAR PHENIX AGS LINAC BOOSTER Pol. H - ion source Spin Rotators 10-20% Snake Siberian Snakes 200 MeV polarimeter RHIC pC “CNI” polarimeters PHOBOS RHIC Absolute H-jet polarimeter Design goal - 70% Polarization, L max = 1.6  s -1 cm -2, 50  √s  500 GeV AGS pC “CNI” polarimeter Polarization facilities at RHIC. Polarimeters. 5.9% Snake

p-Carbon Polarimetry at RHIC Polarized proton Recoil carbon 90º in Lab frame Carbon target P beam Required Accuracy ~5%

the left – right scattering asymmetry A N arises from the interference of the spin non-flip amplitude with the spin flip amplitude (Schwinger) in absence of hadronic spin – flip contributions A N is exactly calculable (Kopeliovich & Lapidus): hadronic spin- flip modifies the QED “predictions” interpreted in terms of Pomeron spin – flip and parametrized as A N for Coulomb -Nuclear Interference.  1) p  pp had A N (t)

H ydrogen Gas Jet and Carbon Wire Targets. Gas Jet Target Carbon Wire Target Beam Cross Section  FWHM~1.8mm Average P ave Peak P peak

The target ladder.

New target motion mechanism.

Detector Setup Ultra thin Carbon ribbon Target (3.5  g/cm 2 ) Si strip detectors (TOF, E C ) 18cm 10mm 2mm pitch 12 strips 72 strips in total Redundancy  Systematic/Consistency Check Redundancy  Systematic/Consistency Check Detector port (inner view) SSD

Event Selection Carbon  400<E<900keV Very clean Carbon event extraction! 33

A N at Coulomb Nuclear Interference (CNI) Region ? Reggen/Pomeron exchange zero hadronic spin-flip With hadronic spin-flip (E950) Phys.Rev.Lett.,89,052302(2002) pC Analyzing Power E beam = 21.7GeV ( High energy & small t limit ) E beam = 100 GeV unpublished Run04  9%

Polarization measurements in RHIC at 100 GeV. Polarization at 100 GeV in RHIC 60-65%.

May 3, 2011A. Poblaguev Spin Meeting APEX measurements May 3, 2011A. Poblaguev Spin Meeting56 Many measurements during short period of time No collisions, rotations, etc. Different targets in the same fill. Blue 2 Vertical Target 6 3 measurements

Polarization profiles, Run 2011

Very thin target, practically non-destructive. Very high rate. Very good signal/noise ratio. Delayed C-ion detection. Single bunch measurements. Remaining problems : Target alignment (Solved). Carbon strips are not straight. Target lifetime. P-CNI polarimeter can be an ideal wire-scanner. P-CNI polarimeter as a wire scanner. AGS and RHIC CNI polarimeters target mechanisms were upgraded for this Run.

Yellow, Vertical-15pi, Horiz-13 pi

AGS pol., during H-jet meas. at injection Intensity A AGS ~ A RHIC injection / 1.11

 Proton polarization measurements in AGS and RHIC at the beam energies GeV) are based on Proton- Carbon and Proton-Proton ( H-jet polarimeter) elastic scattering in the Coulomb Nuclear Interference (CNI) region.  The CNI polarimeters are the essential tools for polarized proton acceleration setup and operation and provide polarization values for RHIC experiments.  Polarimeter operation in the scanning mode also gives polarization profile and beam intensity profile (beam emittance) measurements. Bunch by bunch emittance measurements is a very powerful tool for the machine setup.

AGS polarimeter upgrade and Tune-jump system in Run2011.

RHIC: the “Polarized” Collider STAR PHENIX AGS, 24GeV LINAC BOOSTER, 2.5 GeV Pol. H - ion source Spin Rotators 20% Snake Siberian Snakes 200 MeV polarimeter RHIC pC “CNI” polarimeters RHIC Absolute H-jet polarimeter Design goal: P=70%, L max = 1.6  s -1 cm < √s < 500 GeV AGS pC “CNI” polarimeter 5% Snake Polarization facilities at RHIC. 20% snake

Tune jump system in AGS

72.7% Polarization measurement in AGS at 24 GeV. Polarization out of AGS 60-70%

Polarization at injection in RHIC with the Jump-Quads in operation.

16 February 2011Spin Meeting AGS CNI Polarimeter February 2011RHIC Spin Collaboration Meeting67 1,8 - Hamamatsu, slow preamplifiers 2,3,6,7 - BNL, fast preamplifiers 4,5 - Hamamatsu, fast preamplifiers 3 different detector types: Run 2009: BNL, slow preamplifiers Larger length (50 cm ) Regular length (30 cm ) OuterInner

AGS Horiz. polarization profile, JQ-off time

AGS Horiz. polarization profile, JQ-on

Polarization measurements on the energy ramp in AGS.

Horizontal emittance, AGS intensity- 1.5*10^11

Vertical emittance, AGS intensity-1.5*10^11

Absolute H-jet polarimeter in RHIC.

October 6-10, 2008 A.S. Belov, A. N. Zelenski, SPIN2008, USA Spin filtering technique. Atomic Beam Sources. Hydrogen atoms with electron polarization: m J =+1/2 trajectories. Electron magnetic moment is 659 times Larger than proton :  e /  P ~659. Focusing strength: ~ (dB/dr)   e RF transition, polarization transfer from electrons to protons RHIC beam crossing Breit-Rabi polarimeter permanent magnet sextupole T gradient 5.7 T/cm

H-jet polarimeter. The H-jet polarimeter includes three major parts: polarized Atomic Beam source (ABS), scattering chamber, and Breit-Rabi polarimeter. The polarimeter axis is vertical and the recoil protons are detected in the horizontal plane. The common vacuum system is assembled from nine identical vacuum chambers, which provide nine stages of differential pumping. The system building block is a cylindrical vacuum chamber 50 cm in diameter and of 32 cm length with the four 20 cm (8.0”) ID pumping ports.

H-jet dissociator design. 65 cm Cooling multifoil copper straps. Window. Cold head, 42 K

Fix RHIC proton beam position (diameter  ~1mm). Move H-Jet-target system for every 1.5 mm step. Recoil detector can detect H-Jet-target ! Using RHIC-beam and Recoil detector Using 2.0 mm diameter compression tube Find the best collision point !

RHIC proton beam Forward scattered proton H-jet target recoil proton H-Jet polarimeter. P target is measured by Breit- Rabi Polarimeter <5% Elastic scattering: Interference between electromagnetic and hadronic amplitudes in the Coulumb-Nuclear Interference (CNI) region.

RHIC proton beam H-jet target IP12 recoil proton Si detectors (8cm  5cm)  3  L-R sides Strip runs along RHIC beam axis 1ch width = 4mm (400strips) Channel # relates to recoil angle  R, 5 mrad pitch. Each channel measures kinetic energy T R and TOF. L = 0.8 m

Ch#1  source for energy calibration 241 Am(5.486 MeV) How to identify elastic events ? proton beam Forward scattered proton proton target recoil proton Array of Si detectors measures T R & ToF of recoil particles. Channel # corresponds to recoil angle  R. 2 correlations (T R & ToF ) and (T R &  R )  the elastic process Ch#2Ch#3 Ch#4Ch#5 Ch#6 Ch#7Ch#8 Ch#9 Ch#10 Ch#11,12 Ch#13 Ch#14Ch#15 Ch#16 Ch#1-16 Ch#   R,  R big  T R big  fast protons RR Ch#1 #16

H-jet is an ideal polarimeter ! High (~4.5%) analyzing power in a wide energy range ( GeV). High event rate due to high intensity (~100 mA) circulated beam current in the storage ring (~6% statistical accuracy in one 8hrs. long fill). High polarized H-jet density in RHIC ABS. Non-destructive. No scattering for recoil protons. Clean elastic scattering event identification. Straightforward calibration with Breit-Rabi polarimeter. Most of the false asymmetries are cancelled out in the ratio: P beam =( 1/A)Beam asym / Target asym Problem. Polarization dilution by H 2, H 2 O and other residual gases. Largest source of systematic error.

H-Jet polarimeter: A N in pp 24 GeV: calculations with no hadronic spin flip amplitude contribution are not consistent with data 100 GeV: calculations with no hadronic spin flip amplitude contribution are consistent with data More data to come: 24 GeV: take more data in Run9/10 31 GeV: finalize analysis of data from Run6 250 GeV: take data in Run9/10 24 GeV 100 GeVPLB638, 450 Preliminary

250 GeV luminescence In H-jet

Blue vert. IPM measurement-16 pi. Blue vertical emittance measurement by luminescence monitor in the H-jet polarimeter.

H-jet polarization measurements, Run 2011 Blue- Blue ring Red- Yellow ring

Polarization measurements in RHIC with the H-jet polarimeter. P Target A PP P B A pC P B – beam polarization Exp.asymm.(pp) GeV beam energy. ± 5% absolute accuracy. Analyzing power measurement Exp.asymm.(pC) Measured to ±1% accuracy by the BRP and background evaluation.

RHIC local polarimeter

BRAHMS STAR PHENIX AGS LINAC BOOSTER Pol. H - ion source Spin Rotators 10-20% Snake Siberian Snakes 200 MeV polarimeter RHIC pC “CNI” polarimeters PHOBOS RHIC Absolute H-jet polarimeter AGS pC “CNI” polarimeter Polarization facilities at RHIC. “Siberian Snakes” 5.9% Snake E.Courant coined the “Siberian Snake” name

PHENIX Local Polarimeter Utilizes spin dependence of very forward neutron production (PLB650, 325): neutron charged particles ZDC (energy) + SMD (position) SMD ZDC

PHENIX local polarimeter

PHENIX Local Polarimeter BlueYellow BlueYellow BlueYellow Spin Rotators OFF Vertical polarization Spin Rotators ON Correct Current ! Longitudinal polarization! Spin Rotators ON Current Reversed Radial polarization Asymmetry vs φ Monitors spin direction in PHENIX collision region

STAR Local Polarimeter 3.3<|  |< 5.0 (small tiles only) Utilizes spin dependence of hadron production at high x F : Bunch-by-bunch (relative) polarization Monitors spin direction in STAR collision region Capable to precisely monitor polarization vs time in a fill, and bunch-by-bunch

Summary of RHIC polarimetry Source, Linac, AGS-injector polarimetrs. Hjet: Absolute polarization measurements Absolute normalization for other RHIC Polarimeters pC: Separate for blue and yellow beams Normalization from HJet Polarization vs. time in a fill Polarization profile Fill-by-fill polarizations for experiments PHENIX and STAR Local Polarimeters: Monitor spin direction (through transverse spin component) at collision Polarization vs time in a fill (for trans. pol. beams) Polarization vs bunch (for trans. pol. beams)