From Polarized Targets to Polarized Ion Beams EIC Accelerator - - PowerPoint PPT Presentation

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From Polarized Targets to Polarized Ion Beams EIC Accelerator - - PowerPoint PPT Presentation

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From Polarized Targets to Polarized Ion Beams EIC Accelerator Collaboration Meeting 2019 Opportunities and challenges for EIC spin physics Whitney R. Armstrong October 11, 2019 Argonne National Laboratory 1 Polarized DIS with Longitudinal and

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SLIDE 1

From Polarized Targets to Polarized Ion Beams

Opportunities and challenges for EIC spin physics Whitney R. Armstrong

Argonne National Laboratory

EIC Accelerator Collaboration Meeting 2019 October 11, 2019

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SLIDE 2

1 Polarized DIS with Longitudinal and Transverse nuclear polarization

Recent results from JLab

2 Overview of Fixed Target Technology 3 Comparing polarized fixed targets with polarized ion colliders 4 Polarized Heavy Ions

W.R. Armstrong October 11, 2019 1 / 13

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SLIDE 3

Introduction

Polarized Deep Inelastic Scattering σ0 = 4α2E′2 q4

  • 2

M F1 sin2(θ/2) + 1 ν F2 cos2(θ/2)

  • 2σ0A = −4α2

Q2 E′ E

  • E + E′ cos θ

Mν g1 − Q2 Mν2 g2

  • 2σ0A⊥ = − 4α2

MQ2 E′2 E sin θ cos φ

  • 1

Mν g1 + 2E Mν2 g2

  • A,⊥ =

Araw

,⊥

fPbPt Need and ⊥ polarizations Measured Asymmetries Araw

  • = σ⇑↓ − σ⇑↑

σ⇑↓ + σ⇑↑ Araw

⊥

= σ⇐↓ − σ⇐↑ σ⇐↓ + σ⇐↑ q P k X k′

W.R. Armstrong October 11, 2019 2 / 13

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SLIDE 4

SANE results for x2gp

1 and x2gp 2

x 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.02 − 0.02 0.04 0.06 0.08

p 1

g

2

x

SLAC E143 SLAC E155 EMC SMC HERMES COMPASS CLAS 2

=1.6 GeV 〉

2

Q 〈

2

=2.9 GeV 〉

2

Q 〈

2

=4.1 GeV 〉

2

Q 〈

2

=6.1 GeV 〉

2

Q 〈

Stat 2015 BB LSS2006 DSSV

x 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.1 − 0.05 − 0.05 0.1 0.15

p 2

g

2

x

SLAC E143 SLAC E155 SLAC E155x SMC HERMES

2

=1.6 GeV 〉

2

Q 〈

2

=2.9 GeV 〉

2

Q 〈

2

=4.1 GeV 〉

2

Q 〈

2

=6.1 GeV 〉

2

Q 〈

Stat 2015 BB LSS2006 DSSV

W.R. Armstrong October 11, 2019 3 / 13

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SLIDE 5

The dynamical twist-3 matrix element: d2

An average color Lorentz force

1

dxxn−1{g1 + n n − 1g2} = 1 2dn−1En

2 (Q2, g)

For n = 3

1

x2{2g1 + 3g2}dx = d2

Interpretations of d2

  • Color Polarizabilities (X.Ji 95, E. Stein et
  • al. 95)
  • Average Color Lorentz force

(M.Burkardt)

  • M. Burkardt Phys.Rev.D 88,114502 (2013) and Nucl.Phys.A 735,185

(2004).

d2 = 1 2MP +2Sx P, S | ¯ q(0)gG+y(0)γ+q(0) | P, S but with v = −cˆ z √ 2G+y = −Ey + Bx = −( E + v × B)y d2 ⇒ average color Lorentz force acting on quark moving backwards (since we are in inf. mom. frame) the instant after being struck by the virtual photon. F y = −2M 2d2

W.R. Armstrong October 11, 2019 4 / 13

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SLIDE 6

Quark-gluon Correlations : g2(x, Q2) = gWW

2

(x, Q2) + ¯ g2(x, Q2)

W.R. Armstrong October 11, 2019 5 / 13

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SLIDE 7

Quark-gluon Correlations : g2(x, Q2) = gWW

2

(x, Q2) + ¯ g2(x, Q2)

Twist-2 (Wandzura, Wilczek, 1977) gW W

2

(x, Q2) = −gLT

1

(x, Q2) +

  • 1

x

gLT

1

(y, Q2)dy/y ≡ gtw2

2

(x, Q2) Twist-3 (Cortes, Pire, Ralston, 1992) ¯ g2(x, Q2) = −

  • 1

x

∂ ∂y

mq

M hT (y, Q2) + ξ(y, Q2)

dy

y ≡ gtw3

2

(x, Q2) d2(Q2) = 3

  • 1

x2¯ g2(x, Q2)dx =

  • 1

x2(2g1(x, Q2) + 3g2(x, Q2))dx As Q2 decreases, when do higher twists begin to matter? When is the color force non-zero?

W.R. Armstrong October 11, 2019 5 / 13

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SLIDE 8

proton: PRL 122, 022002 (2019) neutron

]

2

/c

2

[GeV

2

Q

1 2 3 4 5

n 2

d

  • 0.04
  • 0.03
  • 0.02
  • 0.01

0.01

E01-012 (Resonance) E155x E99-117 + E155x (combined) Lattice QCD Sum Rules Chiral Soliton Bag Models RSS (Resonance) Elastic Contribution (CN)

Existing data

W.R. Armstrong October 11, 2019 6 / 13

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SLIDE 9

proton: PRL 122, 022002 (2019)

1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 ]

2

[GeV

2

Q 0.01 − 0.005 − 0.005 0.01 0.015 0.02 0.025 0.03

Lattice SLAC RSS

2

= 2.8 GeV

2

SANE Q

2

= 4.3 GeV

2

SANE Q

MIT Bag CM Bag Chiral Soliton Sum Rules elastic

neutron

]

2

/c

2

[GeV

2

Q

1 2 3 4 5

n 2

d

  • 0.04
  • 0.03
  • 0.02
  • 0.01

0.01

E01-012 (Resonance) E155x E99-117 + E155x (combined) This Work Lattice QCD Sum Rules Chiral Soliton Bag Models RSS (Resonance) Elastic Contribution (CN)

3 3.5 4 4.5 5 5.5

  • 0.006
  • 0.005
  • 0.004
  • 0.003
  • 0.002
  • 0.001

0.001

This Work (with low-x)

Neutron from dn

2 experiment: D.Flay, et.al.

PRD.94(2016)no.5,052003

SANE and dn

2 Result

  • d2 dips around Q2 ∼ 3 GeV2 for proton and neutron

W.R. Armstrong October 11, 2019 6 / 13

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SLIDE 10

proton: PRL 122, 022002 (2019)

1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 ]

2

[GeV

2

Q 0.01 − 0.005 − 0.005 0.01 0.015 0.02 0.025 0.03

Lattice SLAC RSS

2

= 2.8 GeV

2

SANE Q

2

= 4.3 GeV

2

SANE Q

MIT Bag CM Bag Chiral Soliton Sum Rules elastic

neutron

]

2

/c

2

[GeV

2

Q

1 2 3 4 5

n 2

d

  • 0.04
  • 0.03
  • 0.02
  • 0.01

0.01

E01-012 (Resonance) E155x E99-117 + E155x (combined) This Work Lattice QCD Sum Rules Chiral Soliton Bag Models RSS (Resonance) Elastic Contribution (CN)

3 3.5 4 4.5 5 5.5

  • 0.006
  • 0.005
  • 0.004
  • 0.003
  • 0.002
  • 0.001

0.001

This Work (with low-x)

Neutron from dn

2 experiment: D.Flay, et.al.

PRD.94(2016)no.5,052003

SANE and dn

2 Result

  • d2 dips around Q2 ∼ 3 GeV2 for proton and neutron
  • Is this an isospin independent average color force?

W.R. Armstrong October 11, 2019 6 / 13

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SLIDE 11

proton: PRL 122, 022002 (2019)

1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 ]

2

[GeV

2

Q 0.01 − 0.005 − 0.005 0.01 0.015 0.02 0.025 0.03

Lattice SLAC RSS

2

= 2.8 GeV

2

SANE Q

2

= 4.3 GeV

2

SANE Q

MIT Bag CM Bag Chiral Soliton Sum Rules elastic

neutron

]

2

/c

2

[GeV

2

Q

1 2 3 4 5

n 2

d

  • 0.04
  • 0.03
  • 0.02
  • 0.01

0.01

E01-012 (Resonance) E155x E99-117 + E155x (combined) This Work Lattice QCD Sum Rules Chiral Soliton Bag Models RSS (Resonance) Elastic Contribution (CN)

3 3.5 4 4.5 5 5.5

  • 0.006
  • 0.005
  • 0.004
  • 0.003
  • 0.002
  • 0.001

0.001

This Work (with low-x)

Neutron from dn

2 experiment: D.Flay, et.al.

PRD.94(2016)no.5,052003

SANE and dn

2 Result

  • d2 dips around Q2 ∼ 3 GeV2 for proton and neutron
  • Is this an isospin independent average color force?
  • Updated Lattice calculations are long over due!

W.R. Armstrong October 11, 2019 6 / 13

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SLIDE 12

Fixed Target Technology

A quick overview of polarized fixed targets

Dynamic Nuclear Polarization (DNP) solid Metastability-exchange optical pumping (MEOP) gas Spin exchange optical pumping (SEOP) gas Atomic Beam Source (ABS) internal gas Polarized nucleon targets DNP p Solid frozen target NH3, butanol, LiH ABS p Internal target (Hermes) DNP n From d SEOP n From 3 He MEOP n From 3 He

W.R. Armstrong October 11, 2019 7 / 13

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SLIDE 13

Polarized Target Dilution Factor

Example: Polarized NH3 Target Dilution

  • Takes into account scattering from

unpolarized material in target.

  • Need to know target geometry

and material.

  • Function of x and W

f(x, W) = Npσp(x, W) Npσp +

i Niσi(x, W)

Polarized NH3

  • Packing faction of NH3 about 60%

e− beam Ammonia beads Liquid 4He

∼ 3 cm

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.05 0.1 0.15 0.2 0.25 0.3 W.R. Armstrong October 11, 2019 8 / 13

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SLIDE 14

Collider Benefits

Proton

p

  • No dilution from

extra material Deuteron

n p

  • Polarized neutron or

proton

3He

p p n

  • Polarized neutron
  • No dilution from windows, cryogenics, molecular structure, ...
  • Forward spectator tagging to identify struck nucleon.
  • Arbitrary ion polarization direction

W.R. Armstrong October 11, 2019 9 / 13

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SLIDE 15

Collider Benefits

Fixed Target Ion Collider Dilution NH3: f ≃ 0.12

3He: f ≃ 0.92/3

proton: no dilution neutron: f ≃ 1/3 Spectator Tagging Very difficult Possible with forward detectors Luminosity NH3: Beam current limited to 100 nA → L ≃ 1035s−1cm−2

3He: L ≃ 1037s−1cm−2

L ≃ 1034s−1cm−2 better dilution compensates for lower luminosity ,⊥ polarization NH3: physically rotated 5T magnet leads to different rates/backgrounds in detectors for same kinematics

3He: weak field, dual Helmholtz coils

for easy rotation. Bunch by bunch ion spin rotation?

W.R. Armstrong October 11, 2019 10 / 13

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SLIDE 16

Polarized Heavy Ions

Polarized EMC Effect

R ≃ gA

1 /gp 1

Clo¨ et, et.al., Phys.Rev.Lett. 95 (2005) 052302

Tagging to identify struck system

  • Full tagging of spectator system (A-1)
  • Identify struck nucleon to eliminate dilution of nucleus
  • Would like many polarized ions beyond 3He

W.R. Armstrong October 11, 2019 11 / 13

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SLIDE 17

Laser Driven Source

25 Years Ago at Argonne Recent Developments

  • Hybrid SEOP → K and Rb (M.V. Romalis PRL 105, 243001 (2010))
  • Readily available high power diode lasers for pumping Rb (795 nm)
  • Successful polarized 3He program at JLab.

Beginning to investigate general purpose hybrid SEOP to polarize heavier ions such as 21Ne.

W.R. Armstrong October 11, 2019 12 / 13

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SLIDE 18

Summary

  • Nuclear polarization is key for unraveling QCD at the EIC
  • All polarization directions equally important, especially for imaging program
  • Extreme forward tagging will significantly improve the science extracted with each

polarized ion electron collision

  • Nuclear polarization is needed to investigate Polarized EMC Effect
  • A general purpose laser driven source may provide polarized heavy ions

W.R. Armstrong October 11, 2019 13 / 13

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SLIDE 19

Thank You!

W.R. Armstrong October 11, 2019 13 / 13

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SLIDE 20

Backup

W.R. Armstrong October 11, 2019 0 / 1

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SLIDE 21

E07-003 : Big Electron Telescope Array

ˇ Cerenkov Counter Lucite Hodoscope BigCal Forward Tracker Polarized Target Target Outer Vacuum Chamber Super Conducting Magnet W.R. Armstrong October 11, 2019 1 / 1