PHENIX Spin Program Highlights Recent Results and Future

PHENIX Spin Program: Highlights, Recent Results and Future Expectations ü Nucleon helicity structure ü Transverse spin phenomena in p+p ü Polarized p + A A. Bazilevsky (BNL) September 3 -7, 2018, Singapore XLVIII International Symposium on Multiparticle Dynamics A. Bazilevsky, ISMD-2018 1

922 . 03 ar. Xiv: 1602 RHIC Spin Ø How do quarks and gluons build the proton spin ½ ar. Xiv: 15 01. 01220 Ø What do transverse spin phenomena teach us Ø Polarized probe to study nuclear effects A. Bazilevsky, ISMD-2018 2

PHENIX Spin @ RHIC Absolute Polarimeter (H jet) RHIC p. C Polarimeters BRAHMS & ANDY PHENIX STAR Siberian Snakes Spin Rotators LINAC Partial Siberian Snake BOOSTER Pol. Proton Source 500 m. A, 300 ms 200 Me. V Polarimeter A. Bazilevsky, ISMD-2018 2 1011 Pol. Protons / Bunch e = 20 p mm mrad AGS Internal Polarimeter Rf Dipoles Spin Running in PHENIX, long. /trans. L [pb-1] (recorded) Pol. [%] Year s [Ge. V] 2002 200 − / 0. 15 15 2003 200 0. 35 / − 27 2004 200 0. 12 / − 40 2005 200 3. 4 / 0. 2 49 2006 200 7. 5 / 2. 7 57 2006 62. 4 0. 08 / 0. 02 48 200 − / 5. 2 45 2009 200 16 / − 55 2009 500 14 / − 39 2011 500 18 / − 48 2012 200 − / 9. 7 56 2012 510 32 / − 50 2013 510 155 / − 2015 200 − /50 2015 p. Au@200 − /1. 3 2015 p. Al@200 − /4. 0 3 3 51 57 60 54

PHENIX Detector p 0, g, Electromagnetic Calorimeter: | |<0. 35 Muon Piston Calorimeter: 3. 1<| |<3. 9 p , e, J/y e+e-, W e : | |<0. 35 Drift, Pad Chambers, VTX (| |<1) Ring Imaging Cherenkov Counter, To. F Electromagnetic Calorimeter VTX , h±, J/y + -, W : 1. 2<| |<2. 4 Muon Id/Muon Tracker FVTX Relative Luminosity Beam Counter (BBC) Zero Degree Calorimeter (ZDC) Local Polarimetry – ZDC & SMD Spin direction control A. Bazilevsky, ISMD-2018 4

Proton Spin Decomposition Naïve parton model: 1989 EMC (CERN): =0. 12 0. 09 0. 14 Gluons are polarized ( G) Sea quarks are polarized: For complete description include parton orbital angular momentum LZ: Spin Crisis Determination of G and q-bar has been the main A. Bazilevsky, ISMD-2018 goal of longitudinal spin program at RHIC 5

From DIS to pp: (semi)DIS Probes G: pp Probes G: Q 2 dependence of structure fct Directly from gg and qg scattering Photon-gluon fusion (Anti-)quark flavor separation: Through fragmentation processes A. Bazilevsky, ISMD-2018 (Anti-)quark flavor separation: Through Complementary approaches and 6

G: π0 ALL The most abundant probe in PHENIX (triggering + identification capability) PRD 93, 011501 (2016) ALL ~ Non-zero ALL associated with non-zero ΔG ! A. Bazilevsky, ISMD-2018 7

G: DIS+pp global QCD fit DSSV: D. de Florian R. Sassot M. Stratmann W. Vogelsang pp: PHENIX π0+ STAR jet DSSV: Phys Rev Lett, 101, 072001 (2008) Data from up to 2006 New DSSV: Phys Rev Lett, 113, 012001 (2014) Data from up to 2009 (90% CL) Significant non-zero Δg(x) in the kin. region probed by RHIC Similar result from another global fit NNPDF Still huge uncertainty in unmeasured region (x<0. 05) => Measurements at higher √s and forward rapidity A. Bazilevsky, ISMD-2018 8

G: Towards lower x pp J/ψ at √s=510 Ge. V 1. 2<|η|<2. 4 PRD 94, 112008 (2016) Get access to x down to 2× 10 -3 A. Bazilevsky, ISMD-2018 Already constrained by RHIC J/ψ production mechanism uncertainty Not yet in the global fit 9

G: Towards lower x Projection π0: 3. 1<|η|<3. 9 Aschenauer, Stratmann, Sassot PRD 92, 094030 (2015) From available PHENIX+STAR data from 2011 -15 π0 in forward region at √s=510 Ge. V: Based on collected 2013 data Probes lower x down to ~10 -3 A. Bazilevsky, ISMD-2018 Other channels also being measured (but with weaker stat. power) γ, η, π±, heavy flavor through e and μ, h-h, γ-h 10

q-bar: W e |η|<0. 35 Constrains flavor separated (anti-)quark polarization at high Q~MW at x>0. 05, with no fragmentation involved (as in SIDIS) PRD 93, 051103 (2016) A. Bazilevsky, ISMD-2018 11

q-bar: W μ 1. 2<|η|<2. 4 Constrains flavor separated (anti-)quark polarization at high Q~MW at x>0. 05, with no fragmentation involved (as in SIDIS) PRD 98, 032007 (2018) Uncertainties are large due to sizable background (S/B= 0. 15− 0. 28) Data generally agree with current theory constraint, with some tension in backward region, leading to a preference of ubar polarization to be more positive and dbar polarization to be more negative A. Bazilevsky, ISMD-2018 12

Transverse Spin Asymmetries Large Transverse Spin Asymmetries have been observed in p↑p A. Bazilevsky, ISMD-2018 13

Forward-rapidity π0 AN PRD 90, 012006 (2014) Naïve collinear p. QCD predicts A N ~ α smq / p T ~ 0 Asymmetries survive at highest √s Non-perturbative regime! Asymmetries of the ~same size at all √s Asymmetries scale with x. F Collinear (higher twist) p. QCD predicts AN ~ 1/p. T ? No fall off is observed out to p. T ~5 Ge. V/c STAR showed no fall off up to ~7 Ge. V/c A. Bazilevsky, ISMD-2018 14

Transverse Spin Physics Initial State: Final State: Sivers/Twist 3 mechanism Collins mechanism Ø AN for jets, direct photons Ø AN for heavy flavor gluon Ø AN for W, Z, DY Ø Hadron azimuthal asymmetry in jet Ø Hadron pair azimuthal asymmetry (Interference fragmentation function) Sensitive to correlations proton spin – parton transverse motion Sensitive to transversity x spin-dependent FF Not universal between SIDIS & pp Universal between SIDIS & pp & e+e- Ø Parton dynamics Ø 3 D imaging Ø Quark transversity Ø Tensor charge Other mechanisms Ø Diffraction A. Bazilevsky, ISMD-2018

Mid-rapidity π0 AN |η|<0. 35 PRD 90, 012006 (2014) Consistent with 0 AN To <10 -3 precision level at low p. T Sensitive to gluons Used to constrain gluon Sivers effect: Anselmino et al, PRD 74 (2006), 094011 D’Alesio et al, JHEP 1509 (2015), 119 0 2 A. Bazilevsky, ISMD-2018 4 6 8 p. T (Ge. V/c) 10 12 16

Heavy Flavor AN PRD 95, 112001 (2017) 1. 2<|η|<2. 4 Dominated by gluon-gluon fusion Used to constrain tri-gluon correlation in the Twist-3 collinear framework Z. Kang, J. Qiu, W. Vogelsang, F. Yuan, PRD 78, 114013 Y. Koike, S. Yoshida, PRD 84, 014026 Significant reduction in uncertainties expected from 2015 data A. Bazilevsky, ISMD-2018 17

J/ψ AN PRD 86, 099904(E) (2012) AN sensitive to J/ψ production mechanism F. Yuan, PRD 78, 014024: For non-zero gluon Sivers, AN vanishes in color octet model, but survives in color singlet model Consistent with zero Considerable improvements from 2015 data (see below) A. Bazilevsky, ISMD-2018 18

First Run 15 (2015) data !!! 100 Ge. V/nucleon 100 Ge. V Au, Al Polarized Proton Ø Pin down the origin of AN Ø Study gluon saturation effect with a polarized probe! Kang&Yan PRD 84 034019, Kovchegov&Sivert PRD 86 034028, Hatta et al PRD 95 014008 A. Bazilevsky, ISMD-2018 19

AN: Central rapidity π0 at |η|<0. 35 p+p Very high precision data σA ~ 3× 10 -4 (10 -3) at lowest p. T in pp (p. A) AN consistent with 0 for all systems To be used to constrain gluon Sivers fct. p+Al p+Au A. Bazilevsky, ISMD-2018 20

AN: Forward rapidity PRD 98, 012006 (2018) J/ψ at 1. 2<|η|<2. 4 J/ψ production sensitive to gluon distribution AN sensitive to J/ψ production mechanism F. Yuan, PRD 78, 014024: For non-zero gluon Sivers, AN vanishes in color octet model, but survives in color singlet model In p+p and p+Al: AN ~ 0 In p+Au: trends to AN < 0 ? ? A. Bazilevsky, ISMD-2018 21

AN: Forward rapidity h+ at 1. 2<|η|<2. 4 AN >0 in p+p forward AN ~ 0 (suppressed!) in p+Au Theory expects AN ~ 1/A 1/3 due to gluon saturation Z. Kang and F. Yuan, PRD 84, 034019 (2011) Supported by our data! A. Bazilevsky, ISMD-2018 22

AN: Very forward rapidity n at |η|>6. 8 PRL 120, 022001 (2018) Ø Strong dependence on A and particle production in other rapidity regions Ø Likely multiple mechanisms contribute ZDC (n): η>6. 8 BBC (h±): 3. 0<|η|<3. 9 One pion exchange: B. Kopeliovich et al PRD 84, 114012 Electromagnetic interaction: G. Mitsuka, PRC 95 044908 Ø Correlation with particle production in other rapidities, and different A and √s will help to isolate different channels A. Bazilevsky, ISMD-2018 23

Summary Ø How do gluon contribute to the proton Spin Non-zero (in the limitted x-range) and comparable to (or larger than) quark contribution Data at lower x coming Proton spin decomposition Ø What is the flavor structure of polarized sea in the proton AL(W) will contribute to and Ø What are the origins of transverse spin phenomena in QCD Parton dynamics 3 D imaging AN(π0, η), central and forw; AN(Heavy Flavor, J/ψ) => gluon Sivers Ø First p↑A data ! A wealth of exciting results awaiting for theoretical interpretation A. Bazilevsky, ISMD-2018 Probing gluon saturation 24

Backup A. Bazilevsky, ISMD-2018 25

PHENIX: longer term plans PHENIX s. PHENIX ~2021 -22 By ~2025 Evolve s. PHENIX (pp and HI detector) to EIC Detector (ep and e. A detector) Ø To utilize e and p (A) beams at e. RHIC with e-energy up to 15 Ge. V and p(A)energy up to 250 Ge. V (100 Ge. V/n) EIC detector Ø e, p, He 3 polarized Ø Stage-1 luminosity ~1033 cm-2 s-1 (~1 fb-1 /month) A. Bazilevsky, ISMD-2018 26

W: Central vs Forward region W+ W+ W- Clear Jacobian peak at central rapidities A. Bazilevsky, ISMD-2018 W- Suppressed/No Jacobean peak at forward rapidities 27

Symmetry breaking in polarized sea? Unpolarized sea is not symmetric Polarized sea symmetric may be broken too! A. Bazilevsky, ISMD-2018 Already available data (Run 13) will improve the measurement further 28

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π0 AN in p. A Probing gluon saturated matter, Color Glass Condensate (CGC) with polarized protons Kang, Yuan: PRD 84, 034019 Kovchegov, Sievert: PRD 86, 034028 Ø Unique RHIC possibility p↑A Ø Synergy between CGC based theory and transverse spin physics Ø Suppression of AN in p↑A provides sensitivity to Qs Ø Data already collected in Run-2015! A. Bazilevsky, ISMD-2018 30

AN Measurements φ=0 • Detector Left-Right asymmetries or Spin Up-Down asymmetry φ+π φ A = A(φ)=AN sin(φ) • Square root formula: cancels acceptance and luminosity effects NL −> N(φ) NR −> N(φ+π) A. Bazilevsky, ISMD-2018 31

Color Interaction in QCD Controlled non-universality of Sivers function DIS Attractive FSI QCD: Drell-Yan, W or Z Repulsive ISI Sivers. DIS = −(Sivers. DY or Sivers. W or Sivers. Z) AN(dir. γ) has related sign change in Twist-3 Critical test of TMD factorization All observables can be explored at RHIC A. Bazilevsky, ISMD-2018 32