The Future of Spin Physics at

RHIC Steve Vigdor for Sam AronsonSPIN2008, Charlottesville

October 10, 2008I. Present status and plans to

improve luminosity & polarization

II. Spin performance milestones & 6-year run plan to achieve them

III. Recent highlights and future projections from RHIC Spin

IV. eRHIC and possible stagingV. Precision experiments with

stored polarized beams

p-p at RHIC addresses:

1) What does the share of p spin carried by gluons and sea quarks/ antiquarks reveal about effective degrees of freedom?

2) How is parton orbital motion (on the light front) in p manifested in transverse spin asymmetries?

e-N at EIC would exploit scaling viola-tions & exclusive reactions to extend study to completely gluon-dominated region at low momentum fraction.

Nucleon Spin Structure at RHIC and an Electron-Ion Collider

RHIC: World’s Only Polarized Hadron Collider

RIKEN/RBRC

DOE/RIKEN/RBRC

BRAHMS & PP2PP

STAR

PHENIX

AGS

LINAC BOOSTERPol. H- Source

Solenoid Partial Siberian Snake

200 MeV Polarimeter AGS Internal Polarimeter

Rf DipoleStrong AGS Snake

PHOBOS

Spin flipper

Siberian SnakesSiberian Snakes

RHIC Polarimeters

Spin RotatorsSpin Rotators

muon detector

AGS pC Polarimeter

Warm AGS Snake

Polarized atomic H jet

Siberian snakes: built into

design from the start !

No snakes ~1000 depolarizing resonancesWith snakes no first order resonancesTwo partial AGS snakes (11 and 27 spin rotators)

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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15Weeks into run

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2003P=34%

2005P=46%

2006P=60%

2008P=45%

P L(pb^-1) Results2002 15% 0.15 first pol. pp collisions! 2003 30% 1.6 pi^0, photon cross

section, A_LL(pi^0)

2004 40% 3.0 absolute beam polarization

with polarized H jet2005 50% 13 large gluon pol. ruled out (P^4 x L = 0.8) 2006 60% 46 first long spin run * (P^4 x L = 6) 2007 no spin running

2008 50% (short) run

* support for 2006 run from Renaissance Tech. crucial for program

Polarized Collision Performance at RHIC

2006, P=60%

2008, P=45%

2005, P=46%

2003, P=34%

Delivered luminosity at s = 200 GeV

Further development ( long runs!) needed to reach “enhanced” design goals: P=70%, L = 6 1031 cm2s1 (or 15 pb1/week) at s = 200 GeV

Absolute beam polarization calibration to better than 5% design goal achieved!

Polarized proton acceleration to 250 GeV demon-strated. First collision run anticipated 2009.

45 % polarization on first acceleration to 250 GeV!

Loss at strong intrinsic resonance (136 GeV); correctable by adjusting betatron tunes.

injection 250 GeV

RHIC Spin Luminosity and Polarization Goals

Parameter unit Achieved Luminosityupgrade

p- p operation (2006/08) (~ 2012)Energy GeV 100 100 (250)No of bunches … 111 111Bunch intensity 1011 1.5 2.0Ave. delivered lum.** 1030 cm-2s-1 23 80 (200)Polarization % 60 70

** without vertex cuts

Planned luminosity improvements: reduce * from 1.0 to 0.5 m mitigate 10 Hz quad triplet vibration near-integer working point

non-linear chromaticity correction transfer line and booster mods. 9 MHz and 56 MHz RF upgrades

Planned polarization improvements: horizontal tune jumps in AGS improved orbit control in RHIC snakes

Further p Beam Improvements Under Development: Electron Lenses

p-p luminosity limited by head-on beam-beam tune spread Low energy (~5 keV) e beam interacting with proton beam can

compensate head-on beam-beam tune spread ( 2 luminosity?) Single and multi-particle simulation underway Possible implementation in RHIC by 2014

w/o beam-beam compensation with half and full beam-beam compensation

Large tune spread luminosity loss

See T. Roser talk, 10/11/08.

Further p Beam Improvements Under Development: Coherent Electron Cooling

CeC of high-energy hadron beams: high-gain FEL based on high-brightness ERL (V. Litvinenko & Y. Derbenev) boost LHC and EIC luminosities?

Wiggler: FEL amplification (x 102-3) of e-beam modulations, while chicane adds dispersion to h beam

Kicker: attraction to e-beam density peak re-duces ion-beam E spread.

Modulator: hadron beam structure intro-duces density modu-lation in e-beam

Uses 20 MeV R&D ERL already under

develop-ment at BNLPlan proof-of-principle test @ RHIC by 2014 with Au beam.

Does not address beam-beam limit on RHIC p+p luminosity.

Year Due

# Milestone

2013 HP8 Measure flavor-identified q and q contributions to the spin of the proton via the longitudinal-spin asymmetry of W production.

2013 HP12(update of HP1)

Utilize polarized proton collisions at center of mass energies of 200 and 500 GeV, in combination with global QCD analyses, to determine if gluons have appreciable polarization over any range of momentum fraction between 1 and 30% of the momentum of a polarized proton.

2015 HP13(new)

Test unique QCD predictions for relations between single-transverse spin phenomena in p-p scattering and those observed in deep-inelastic lepton scattering

Near-Term RHIC Spin Program Addresses Three Specific DOE Hadron Physics Performance Milestones

A few brief comments on the physics goals to follow…

Tentative RHIC Run Plan Following 2008 PAC Recommendations(assumes 6-month FY09 CR, 2-species runs in FY10-14 & best info on detector upgrade schedules)

Fiscal Year

Colliding Beam Species/Energy

Comments

2009 200 GeV p+p~12 physics weeks to complete 200 GeV ALL measurements – could be swapped with 500 GeV Run 10 if >6-month FY09 CR likely; STAR DAQ1000 fully operational

2010500 GeV p+p ~5-6 physics weeks to commission collisions, work on polarization & luminosity and

obtain first W production signal to meet 2011 RIKEN milestone

200 GeV Au+Au 9-10 physics weeks with PHENIX HBD, STAR DAQ1000 & TOF permits low-mass dilepton response map and 1st HI collision test of transverse stochastic cooling (one ring)

2011

Au+Au at assorted low E

1st energy scan for critical point search, using top-off mode for luminosity improvement – energies and focus signals to be decided; commission PHENIX VTX (at least prototype)

200 GeV U+U 1st U+U run with EBIS, to increase energy density coverage

2012500 GeV p+p 1st long 500 GeV p+p run, with PHENIX muon trigger and STAR FGT upgrades, to

reach ~100 pb-1 for substantial statistics on W production and G measurements

200 GeV Au+Au Long run with full stochastic cooling, PHENIX VTX and prototype STAR HFT installed; focus on RHIC-II goals: heavy flavor, -jet, quarkonium, multi-particle correlations

2013500 GeV p+p Reach ~300 pb-1 to address 2013 DOE performance milestone on W production

200 GeV Au+Au or 2nd low-E scan

To be determined from 1st low-E scan and 1st upgraded luminosity runs, progress on low-E e-cooling, and on installation of PHENIX FVTX and NCC and full STAR HFT

2014

200 GeV Au+Au or 2nd low-E scan

Run option not chosen for 2013 run – low-E scan addresses 2015 DOE milestone on critical point, full-E run addresses 2014 (-jet) and 2016 (identified heavy flavor) milestones. Proof of principle test of coherent electron cooling.

200 GeV p+p Address 2015 DOE milestone on transverse SSA for -jet; reference data with new detector subsystems; test e-lenses for p+p beam-beam tune spread reduction

Present and Future Constraints on Gluon Polarization in the Proton:

1st NLO pQCD analysis incorporating RHIC spin inclusive jet and 0 ALL (2006) data (arXiv:0804.0422) by de Florian, Sassot, Stratmann & Vogelsang DIS and RHIC spin impose comparable constraints to date on shape & magnitude of gluon polarization vs. x; RHIC spin data should dominate after next long 200 GeV p+p run, with new jet+jet coincidence data significantly constraining x-dependence.

w/ Run 6 RHIC data

w/ projected

Run 9 RHIC data

Future Constraints on Sea Anti-quark Polarization s = 500 GeV p + p W + + X (u+d W + e + or + )

W + X (d+u W e or )

Measure 1-spin PV helicity asymmetry AL for 2 beams 2 charge states u/u, d/d in valence region ( “self-calibration” of technique) d/d, u/u for x ~ 0.02 - 0.2 check prediction of many nucleon structure models that |u d | > |d u | (sizable from FNAL E866)

Anticipate: 1st 500 GeV collision run in 2009

~100 pb1 by 2012

~300 pb1 by 2013

Similar sensitivity for PHENIX

Program relies on ongoing upgrades to PHENIX trigger, STAR forward tracking

STAR projections for mid-rapidity e+ from W+

STAR projec-tions for mid-rapidity e from W

300 pb1, P=0.7, 70% efficiency

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0.1 0.2 0.3 x

Constraining Origin of Transverse Spin Asymmetries:

0RHIC II Drell-Yan Projections

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HERMES Sivers

Results

Large AN observed for pp forward hadron inclusive can arise from entrance- (Sivers) or exit-channel (Collins jet fragmentation) transverse spin-momentum correlations. Sivers asyms. sensitive to quark and gluon orbital ang. mom. on light front same frame where G, measured frame for Ji sum rule AN

Sivers(SIDIS, FSI among outgoing partons) = ANSivers(DY, ISI)

prediction sensitive to all aspects of pQCD treatment

Test predicted sign change first in inclusive p+p +X in time for 2015 DOE milestone.

PHENIX

STAR

e-ion detector

eRHIC

Main ERL (1.9 GeV)

Low energy recirculation pass

Beam dump

Electronsource

Possible locationsfor additional e-ion detectors

Four recirculation passes

Long-Term (>2020) Future of Spin Physics at RHIC: EIC eRHIC

Subsequent stages/ alternative layouts could increase e-beam & ion-beam energies and L from nominal 10 250 GeV, ~3 1033 cm2s1 e+p

Add ERL injector with polarized e source to enable e+p,3He and e+A (up to Uranium) to study matter in gluon-dominated regime

10 GeV electron design energy.Possible upgrade to 20 GeV by doubling main linac length.

5 recirculation passes ( 4 in RHIC tunnel) Multiple electron-hadron interaction points

(IPs) permit multiple detectors; Full polarization transparency at all

energies for the electron beam; Ability to take full advantage of transverse

cooling of the hadron beams; Possible options to include polarized

positrons at lower luminosity: compact storage ring or ILC-type e+ source

R&D already under way on various accelerator issues; more to come.

EIC probes weak coupling regime of very high gluon density, where gauge boson occupancy >> 1. All ordinary matter has at its heart an intense, semi-classical force field -- can we demonstrate its universal behavior?

Search for supersymmetry @ LHC, ILC (?): seeking to unify matter and forces

Electron-Ion Collider: reveal that Nature blurs the distinction

Gluons dominate the soft constituents of hadrons! But density must saturate…

Deep inelastic scattering @ HERA

EIC Science: Study of Force (Gluon)-Dominated Matter

See R. Milner talk, 10/6/08

Polarized e + N at EIC

See R. Milner talk, 10/6/08; Note INT workshops on EIC science, Fall ’09 and ’10.

Polarized DIS, -gluon fusion to determine gluon polarization down to x ~ few 104

Bjorken sum rule test to ≲ 2% precision SIDIS for low-x sea-quark polarization and transverse spin studies

More luminosity-hungry: Polarized DVCS, exclusive reactions + LQCD GPD’s map low-x transverse position-dep. PDF’s; Jq from Ji sum rule

Parity violation in e+p,d at high Q2 to study running of weak coupling below Z-pole

2 x (0.5-0.7) GeV SRF linacs

100 MeV injector2-4 passes, depending on top energy

IP

Stage I e-RHIC with ERL inside RHIC tunnel @ IP2: up to 2 (4) GeV e with RT (SC) magnets

Intermediate-Term Possibilities: 1st (Medium Energy) Stage of EIC?

Would enable few GeV e on 100 GeV/N heavy ions and 250 GeV p First look at saturation surface for nuclei in e+A DIS, confirmation of nuclear “oomph” factor; e+A diffraction tests of high gluon occupancy e-p program emphasizing transverse-spin SIDIS over broad Q2-range TMD evolution; detection of boosted target fragments to probe spin-dependent correlations, intrinsic heavy flavor in nucleon; extend DIS. Need to develop science case, detector design, cost estimate. Most equipment would be reused later in full EIC

ME-EIC parameters for e-p collisions (2 GeV option, 50 mA polarized e source, maintaining pp, pA, AA collisions at RHIC detectors)

not cooled pre-cooled high energy cooling

p e p e p e

Energy, GeV 250 2 250 2 250 2

Number of bunches 111 111 111

Bunch intensity, 1011 2.0 0.31 2.0 0.31 2.0 0.31

Bunch charge, nC 32 5 32 5 32 5

Normalized emittance, 1e-6 m, 95% for p / rms for e 15 37 6 14.7 1.5 3.7

rms emittance, nm 9.4 9.4 3.8 3.8 0.94 0.94

beta*, cm 50 50 50 50 50 50

rms bunch length, cm 40 1 40 1 40 1

beam-beam for p /disruption for e 1.5e-3 12 3.8e-3 31 0.015 120

Peak Luminosity, 1e32, cm-2s-1

0.93 2.3 9.3

Also a test-bed for high-energy coherent e-cooling to prepare for full EIC.

Possible Alternative Intermediate-Term Future: Precision Experiments in Storage Rings

g-2 ring @ AGS

Physics Beyond the Standard Model: Supersymmetry SUSY working group report: Les Houches 2007 (Feb 08 archive)

“The strongest hint for a TeV-scale modifica-tion of the Standard Model originates from theanomalous magnetic moment of the muon.”

History: muon anomalous magnetic moment @ AGS

See W. Marciano’s talk, 10/7/08

Novel Storage Ring EDM Exp’ts @ AGS ? Inject longitudinally pol’d p or d beam, via AGS, into dedicated storage ring Choose magic momentum + static E, B combination (B=0 for protons) to ~cancel (g-2) horizontal spin precession Search for EDM signature of vertical polarization build-up due to precession in strong E-field (static for p, v B for d)

Cancel many systematic errors by measuring for counter-rotating (vertically separated) beams simultaneously. Sensitivity goal ~ few 1029 ecm for p, ~ 1029 ecm for d If EDM 0 observed for n, p and/or d, the combination powerfully constrains the source. E.g., the three systems have quite different sensitivities to QCD vs. SUSY (latter strongly enhanced in d).

See Y. Semertzidis talk, 10/07/08.

Summary1) Strong progress in recent years on luminosity and

polarization for p+p collisions at RHIC, clear plans for reaching ‘enhanced’ design specs over next few years.

2) Despite budget-induced shortening of recent runs, RHIC spin data already important in constraining G(x) and origin of transverse spin asymmetries.

3) Next ~5 years should produce dramatic progress toward 3 milestones in nucleon spin structure, including 500 GeV W production for antiquark polarization.

4) Innovative electron lens and coherent e-cooling R&D plans can have great impact on future p+p and e+p luminosities.

5) eRHIC linac-ring concept, with possible 1st “medium-energy” stage viable strategy toward spin physics at very low x. Much R&D and strengthening of science case needed before next U.S. Nuclear Physics Long Range Plan (~2012-13).

6) Charged-particle EDM searches in storage rings intriguing possibility for complementary beyond-SM spin physics.