[PPT] - The GPD program in Halls A & C Carlos Mu noz Camacho Institut PowerPoint Presentation

SLIDE 1

The GPD program in Halls A & C

Carlos Mu˜ noz Camacho

Institut de Physique Nucl´ eaire, CNRS/IN2P3 (France)

June 21, 2018 Joint Hall A and C Summer Meeting

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 1 / 35

SLIDE 2

Introduction

Outline

1 Introduction 2 Nucleon 3D-imaging & Generalized Parton Distributions (GPDs) 3 Deeply Virtual Compton Scattering (DVCS): ep → epγ 4 Experimental program at Jefferson Lab

Recent results on DVCS and π0 production Experiments at 12 GeV

5 Summary

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 2 / 35

SLIDE 3

Introduction

Studying the structure of the nucleon experimentally

Elastic scattering

y x z

⊥

r ) ( ⊥ r ρ

⊥

r p x

Form factors

Nobel prize, 1961

Deeply Inelastic Scattering

y x z

⊥

r p

f x ( )

1

xp Q z 1 ~

⊥

δ

x

Parton distributions

Nobel prize, 1969 Nobel prize, 1990

Hard exclusive processes

y x z

p xp Q z 1 ~

⊥

δ

⊥

r

⊥

r

) , (

⊥

r x f

1

Generalized Parton Distributions (GPDs)

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 3 / 35

SLIDE 4

GPDs & DVCS

Deeply Virtual Compton Scattering (DVCS): γ∗ p → γ p

Handbag diagram High Q2 Perturbative QCD Non-perturbative GPDs Bjorken limit : Q2 = −q2 → ∞ ν → ∞

xB =

Q2 2Mν fixed

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 4 / 35

SLIDE 5

GPDs & DVCS

DVCS experimentally: interference with Bethe-Heitler

At leading order in 1/Q (leading twist) : d5 → σ −d5 ← σ = ℑm (T BH · T DV CS) d5 → σ +d5 ← σ = |BH|2 + ℜe (T BH · T DV CS) + |DV CS|2

T DV CS = +1

−1

dx H(x, ξ, t) x − ξ + iǫ + · · · = P +1

−1

dxH(x, ξ, t) x − ξ

Access in helicity-independent cross section

− iπ H(x = ξ, ξ, t)

Access in helicity-dependent cross-section

+ . . .

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 5 / 35

SLIDE 6

GPDs & DVCS

Leading twist GPDs

8 GPDs related to the different combination of quark/nucleon helicities 4 chiral-even GPDs: conserve the helicity of the quark Access through DVCS (and DVMP)

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 6 / 35

SLIDE 7

GPDs & DVCS

Leading twist GPDs

8 GPDs related to the different combination of quark/nucleon helicities 4 chiral-odd GPDs: flip helicity of the quark “transversity GPDs” Experimental access more complicated (π0 electroproduction?)

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 7 / 35

SLIDE 8

GPDs & DVCS

Kinematic coverage

Kinematic complementarity between different facilities:

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 8 / 35

SLIDE 9

DVCS @ JLab

The GPD experimental program at Jefferson Lab

Hall A: high accuracy, limited kinematic coverage Hall B: wide kinematic range, limited precision Hall C: high precision program at 11 GeV Partially overlapping, partially complementary programs with different experimental setups The roadmap: Early results (2001) from non-dedicated experiment (CLAS) 1st round of dedicated experiments in Halls A/B in 2004/5 2nd round on 2008–2010: precision tests + more spin observables Compeling DVCS experiments in Halls A+B+C at 11 GeV (2017)

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 9 / 35

SLIDE 10

DVCS @ JLab Recent results

Experimental setup

100-channel scintillator array High Resolution Spectrometer 132-block PbF2 electromagnetic calorimeter

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 10 / 35

SLIDE 11

DVCS @ JLab Recent results

DVCS cross sections: azimuthal analysis

Q2 = 2.36 GeV2, xB = 0.37, −t = 0.32 GeV2

d4σ = T 2

BH + TBHRe(TDVCS) + T 2 DVCS

Re(TDVCS) ∼ cI

0 + cI 1cos φ + cI 2cos 2φ

T 2

DVCS ∼ cDVCS

+ cDVCS

1

cos φ ∆4σ = d4− → σ − d4← − σ 2 = Im(TDVCS) Im(TDVCS) ∼ sI

1sin φ + sI 2sin 2φ

M. Defurne et al. Phys. Rev. C 92, 055202

(2015)

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 11 / 35

SLIDE 12

DVCS @ JLab Recent results

DVCS cross sections: Q2–dependance

No Q2-dependance within limited range ⇒ leading twist dominance

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 12 / 35

SLIDE 13

DVCS @ JLab Recent results

DVCS cross sections: kinematical power corrections

KM10a: global fit to HERA x-sec & HERMES + CLAS spin asymmetries

Kumericki and Mueller (2010)

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 13 / 35

SLIDE 14

DVCS @ JLab Recent results

DVCS cross sections: kinematical power corrections

KM10a: global fit to HERA x-sec & HERMES + CLAS spin asymmetries

Kumericki and Mueller (2010)

Target-mass corrections (TMC): ∼ O(M 2/Q2) and ∼ O(t/Q2)

Braun, Manashov, Mueller and Pirnay (2014)

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 13 / 35

SLIDE 15

DVCS @ JLab E07-007

Rosenbluth-like separation of the DVCS cross section

σ(ep → epγ) = |BH|2

Known to ∼ 1%

+ I(BH · DV CS)

Linear combination of GPDs

+ |DV CS|2

Bilinear combination of GPDs

I∝ 1/y3 = (k/ν)3,

T DV CS

2∝ 1/y2 = (k/ν)2 BKM-2010 – at leading twist → 7 independent GPD terms:

ℜe, ℑm
CI, CI,V , CI,A

(F)

,

and CDV CS(F, F∗). ϕ-dependence provides 5 independent observables: ∼1, ∼ cos ϕ, ∼ sin ϕ, ∼ cos(2ϕ), ∼ sin(2ϕ)

The measurement of the cross section at two or more beam energies for exactly the same Q2, xB, t kinematics, provides the additional information in order to extract all leading twist observables independently.

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 14 / 35

SLIDE 16

DVCS @ JLab E07-007

E07-007: DVCS beam-energy dependence

Cross section measured at 2 beam energies and constant Q2, xB, t

E = 4.5 GeV E = 5.6 GeV

Leading-twist and LO simultaneous fit of both beam energies (dashed line) does not reproduce the data Light-cone axis in the (q,q′) plane (Braun et al.): H++, H++, E++, E++

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 15 / 35

SLIDE 17

DVCS @ JLab E07-007

Beyond Leading Order (LO) and Leading Twist (LT)

Two fit-scenarios:

Light-cone axis in the (q,q′) plane (Braun et al.)

LO/LT + HT H++, H++, H0+, H0+ LO/LT + NLO H++, H++, H−+, H−+

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 16 / 35

SLIDE 18

DVCS @ JLab E07-007

E07-007: DVCS beam-energy dependence

Cross section measured at 2 beam energies and constant Q2, xB, t

(deg) Φ 100 200 300

4

nb/GeV 0.1 0.2

σ

4

d σ

4

∆

(deg) Φ 100 200 300

4

nb/GeV 0.05 0.1

Fit LT/LO Fit HT KM15

Leading-twist and LO simultaneous fit of both beam energies (dashed line) does not reproduce the data Including either NLO or higher-twist effects (dark solid line) satisfactorily reproduce the angular dependence

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 17 / 35

SLIDE 19

DVCS @ JLab E07-007

DVCS2 and I (DVCS·BH) separation

DVCS2 and I (DVCS·BH) separated in NLO and higher-twist scenarios

(deg) Φ 100 200 300

4

nb/GeV 0.04 − 0.03 − 0.02 − 0.01 − 0.01 0.02 0.03 0.04 ++/-+

2

DVCS Interference ++/-+ ++/0+

2

DVCS Interference ++/0+ (deg) Φ 100 200 300

4

nb/GeV 0.01 − 0.005 − 0.005 0.01

DVCS2 & I significantly different in each scenario Sizeable DVCS2 contribution in the higher-twist scenario in the helicity-dependent cross section

Nature Commun. 8, 1408 (2017)

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 18 / 35

SLIDE 20

DVCS @ JLab π0 electroproduction

π0 electroproduction (ep → epπ0)

At leading twist: dσL dt = 1 2Γ

hN,hN′

|ML(λM = 0, h′

N, hN)|2 ∝ 1

Q6 σT ∝ 1 Q8 ML ∝ 1 dz φπ(z) z 1

−1

dx

1

x − ξ + 1 x + ξ

×
Γ1

Hπ0 + Γ2 Eπ0

Different quark weights: flavor separation of GPDs

|π0 =

1 √ 2{|u¯

u − |d ¯ d}

Hπ0 =

1 √ 2 2 3

Hu + 1

3

Hd
|p = |uud

HDV CS = 4 9Hu + 1 9Hd

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 19 / 35

SLIDE 21

DVCS @ JLab π0 electroproduction

Exclusive π0 electroproduction cross-sections – Hall A

)

2

b GeV µ ( dt

L

σ d

L

∈ +

T

σ d

0.2 0.4 0.6 0.8

2

=1.9 GeV

2

Q

2

=2.3 GeV

2

Q (a)

)

2

t (GeV

min

t

0.05 0.1 0.15 0.2

Kin2

]

L

σ

L

∈ +

T

σ [

Kin3

]

L

σ

L

∈ +

T

σ [

0.5 1 (b)

σT + ǫLσL ∼ Q−5 (similar to σT (ep → epπ+) measured in Hall C) GPDs predict σL ∼ Q−6 σT likely to dominate at these Q2, but L/T separation necessary (→ new experiment. . . )

E. Fuchey et al., Phys. Rev. C83 (2011), 025125
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noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 20 / 35

SLIDE 22

DVCS @ JLab π0 electroproduction

Rosenbluth separation

d4σ dQ2dxBdtdφ = 1 2π Γ(Q2, xB, E) dσT dt +ǫdσL dt +

2ǫ(1 + ǫ)dσT L

dt cos φ+ǫdσT T dt cos 2

Kinematics

Setting Q2 xB Ebeam ǫ (GeV2) (GeV) Kin1 1.50 0.36 3.355 0.52 5.55 0.84 Kin2 1.75 0.36 4.455 0.65 5.55 0.79 Kin3 2.00 0.36 4.455 0.53 5.55 0.72

tmin − t = 0.025 GeV2

(deg) Φ 60 120 180 240 300 360 )

2

b/GeV µ ( Φ dtd σ

2

d π 2 0.4 0.8 1.2 1.6 2 2.4 2.8 (deg) Φ 60 120 180 240 300 360 )

2

b/GeV µ ( Φ dtd σ

2

d π 2 0.4 0.8 1.2 1.6 2 2.4 2.8

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 21 / 35

SLIDE 23

DVCS @ JLab π0 electroproduction

π0 separated response functions

0.02 0.04 0.06 0.08 )

2

barn/GeV µ /dt (

T/L

σ d

0.5

0.5 1 1.5 2

2

=1.5 GeV

2

Q 0.02 0.04 0.06 0.08 )

2

barn/GeV µ /dt (

TL

σ d

0.2
0.15
0.1
0.05

0.05 0.1

2

t (GeV/c)

min

t

0.02 0.04 0.06 0.08 )

2

barn/GeV µ /dt (

TT

σ d

0.6
0.4
0.2

0.02 0.04 0.06 0.08 0.1 0.12

0.5

0.5 1 1.5 2

2

=1.75 GeV

2

Q 0.02 0.04 0.06 0.08 0.1 0.12

0.2
0.15
0.1
0.05

0.05 0.1

2

t (GeV/c)

min

t

0.02 0.04 0.06 0.08 0.1 0.12

0.6
0.4
0.2

0.02 0.04 0.06 0.08

0.5

0.5 1 1.5 2

2

=2 GeV

2

Q 0.02 0.04 0.06 0.08

0.2
0.15
0.1
0.05

0.05 0.1

2

t (GeV/c)

min

t

0.02 0.04 0.06 0.08

0.6
0.4
0.2

Goloskokov, Kroll (2011) Goldstein, Hernandez, Liuti (2011) Vanderhaeghen, Guichon, Guidal (1999)

arXiv:1608.01003

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 22 / 35

SLIDE 24

DVCS @ JLab π0 electroproduction

π0 L/T separated cross section

Cross section largely dominated by transverse component → far from asymptotic prediction of QCD Fair agreement with models using modified factorization approach → potential access to transversity GPDs Indications of small longitudinal response through non-zero σLT

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 23 / 35

SLIDE 25

DVCS @ JLab LD2 target

E08-025: DVCS and π0 off quasi-free neutrons

LD2 as a target Quasi-free p evts subtracted using the (normalized) data from E07-007 Concurrent running: switching LD2/LD2 → minimize uncertainties

D(e, e π0)X − p(e, e π0)p = n(e, e π0)n + d(e, e π0)d

The average momentum transfer to the target is much larger than the np relative momentum, justifying this impulse approximation

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 24 / 35

SLIDE 26

DVCS @ JLab LD2 target

π0 electroproduction cross section off the neutron

Cross section off coherent d found negligeable within uncertainties Very low Ebeam dependence of the n cross section → dominance of σT

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 25 / 35

SLIDE 27

DVCS @ JLab LD2 target

Separated π0 cross section off the neutron

0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

)

2

b/GeV µ ( dt

T

σ d

0.6
0.4
0.2

0.2 0.4 0.6

)n π n(e,e' )d π d(e,e'

0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

)

2

b/GeV µ ( dt

L

σ d

0.6
0.4
0.2

0.2 0.4 0.6

0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

)

2

b/GeV µ ( dt

TT

σ d

0.25
0.2
0.15
0.1
0.05

0.05

)

2

t (GeV

min

t

0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 )

2

b/GeV µ ( dt

LT

σ d

0.06
0.04
0.02

0.02 0.04 0.06

M. Mazouz et al, Phys.Rev.Lett. 118 (2017)

In the modified factorization approach (KG): dσT ∝

1 − ξ2

|HT |2 −

t′ 8M 2

¯

ET

2

dσT T ∝

t′ 8M 2

¯

ET

2

0.15 0.2 0.25 0.3 0.35

| 〉

T

H 〈 |

5

5 10 15 20

| 〉

u T

H 〈 | | 〉

d T

H 〈 |

)

2

(GeV

t

0.15 0.2 0.25 0.3 0.35

| 〉

T

E 〈 |

40
20

20 40 60 80 100

| 〉

u T

E 〈 | | 〉

d T

E 〈 |

|Hp,n

T

|2 = 1

2

2

3

Hu,d

T

+ 1

3

Hd,u

T

2
C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 26 / 35

SLIDE 28

JLab @ 12 GeV Hall A

E12-06-114: JLab Hall A at 11 GeV

JLab12 with 3, 4, 5 pass beam (6.6, 8.8, 11.0 GeV beam energy)

Bj

x 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 )

2

(GeV

2

Q 5 10

2

<4 GeV

2

W 11 GeV ≤

beam

Unphysical with E = 6.6 GeV

beam

E = 8.8 GeV

beam

E = 11.0 GeV

beam

E = 5.75 GeV

beam

E

DVCS measurements in Hall A/JLab

88 days 250k events/setting

1 year of operations in JLab/Hall A

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 27 / 35

SLIDE 29

JLab @ 12 GeV Hall A

Cumulated statistics

F– Fall Sp– Spring Q2 – in GeV2 ~50% of allocated 100 PAC days from Fall 2014, Spring 2016, and Fall 2016

Period Kinematic Q2 xB % target Charge F '14 361 3.20 0.36 100.0 F '16 362 3.60 0.36 100.0 F '16 363 4.47 0.36 100.0 Sp '16 481 2.7 0.48 100.0 Sp '16 482 4.37 0.48 56.6 Sp '16 483 5.33 0.48 76.4 Sp '16 484 6.90 0.48 53.0 F '16 601 5.54 0.60 100.0 F '16 602 6.10 0.60 0.0 F '16 603 8.40 0.60 100.0 F '16 604 9.00 0.60 0.0

C. Mu˜

noz Camacho (IPNO, CNRS/IN2P3) 3D structure of hadrons @ JLab & EIC 06/21/2018 28 / 35