Study of Generalized Parton Distribu ons at Je ff erson Lab for - - PowerPoint PPT Presentation

SLIDE 1

for LIGHT CONE 2016 September 05, 2016

Andrey Kim University of Conneccut

Study of Generalized Parton Distribuons at Jefferson Lab

SLIDE 2

2

LIGHT CONE 2016

xP S rT

Deeply virtual exclusive reacons such as photon or π0 meson producon with large gamma virtuality Q2 are key processes to probe the complex internal structure of nucleon and access informaon about quark posion and angular momentum distribuons from experimental observables.

Two main processes can be used to access this informaon experimentally:

Deeply Virtual Compton Scaering and Deeply Virtual Meson Producon

Introducon

SLIDE 3

3

LIGHT CONE 2016

Form factors Parton distribuons

Correlaon between quark longitudinal momentum and transverse spaal distribuons Elasc Scaering Deep Inelasc Scaering HARD EXCLUSIVE PROCESSES

Generalized parton distribuons

SLIDE 4

4

LIGHT CONE 2016

parton helicity conserving (chiral-even) GPDs parton helicity-flip (chiral-odd) GPDs The GPDs depend on three kinemac variables:

Generalized parton distribuons

e.g.

average parton momentum fracon (skewness) difference between the inial and final fracons of the longitudinal momentum carried by the struck parton momentum transfer between inial and final nucleons

SLIDE 5

5

LIGHT CONE 2016

Exclusive processes at JLab at 6 GeV

✦ parally: complimentary,

• verlapping

✦ The roadmap:

H1, ZEUS

H1, ZEUS

0.7

✦ Early results (2001) from non-dedicated experiment (CLAS) ✦ First round of dedicated experiments in Halls A/B in 2004/2005 ✦ Second round in 2008-2010 ✦ Compeling exclusive program in Halls A/B at 12 GeV

✦ Hall A and Hall B (CLAS) at 6 GeV

✦ Hall A: high accuracy limited kinemacs ✦ Hall B: wide kinemac range limited accuracy

SLIDE 6

6

LIGHT CONE 2016

DVCS experimental observables

DVCS:

unpolarized terms beam polarized target polarized double polarized

SLIDE 7

7

LIGHT CONE 2016

Deeply virtual Compton scaering

Unpolarized cross secons, unpolarized beam and target Polarized beam and Unpolarized target (BSA) Unpolarized beam and Polarized target (TSA) Polarized beam and Polarized target (DSA)

SLIDE 8

8

LIGHT CONE 2016

DVCS cross secons

90 180 270 E00-110 2 |BH+ DVCS| 2 |BH| 2

• |BH|

2 |BH+ DVCS| (deg) φ 90 180 270 (deg) φ 90 180 270 (deg) φ 90 180 270 E00-110 Total fit

DVCS cross secon (nb/GeV4)

0.05 0.1

• 0.02

0.02

beam helicity-independent beam helicity-dependent

PRL97:262002 (2006), C. Munoz Camacho et al. (Hall A collaboraon)

First round experiment at Hall A: E00-110

SLIDE 9

9

LIGHT CONE 2016

DVCS scaling test

PRL97:262002 (2006), C. Munoz Camacho et al. (Hall A collaboraon)

✦ Q2 independence:

✦ Twist-2 dominance (GPDs)

2

= 1.5 GeV

2

Q

2

= 1.9 GeV

2

Q

2

= 2.3 GeV

2

Q VGG model

integrated over t

First round experiment at Hall A: E00-110

curve is from VGG model calculaons (Vanderhaeghen, Guichon, Guidal)

SLIDE 10

10

LIGHT CONE 2016

0.1 0.2 0.3 0.1 0.2 0.3 0.1 0.2 0.3 0.5 1 1.5 0.1 0.2 0.3 0.5 1 1.5 0.5 1 1.5

DVCS beam spin asymmetries

ALUon the proton

JLab Hall A results VGG twist-2 VGG twist-3 VGG model: Vanderhaeghen,Guichon,Guidal

PRL100:162002 (2008) F.X. Girod et al. (CLAS collaboration)

1 2 3 4 0.1 0.2 0.3 0.4 0.5 B

x )

2

(GeV

2

Q

2

• t=

0.28 GeV

2

• t=

0.49 GeV

90 180 270 360

(deg) φ

90 180 270 360

(deg) φ

• 0.2

0.2

• 0.2

0.2

ALU ALU

VGG twist-2 VGG twist-3

Q2=2.8 xB=0.45 Q2=3.3 xB=0.46 Q2=3.7 xB=0.46 Q2=3.0 xB=0.36 Q2=2.7 xB=0.36 Q2=2.3 xB=0.35 Q2=1.7 xB=0.25 Q2=1.9 xB=0.25 Q2=2.2 xB=0.25 Q2=1.2 xB=0.13 Q2=1.4 xB=0.17 Q2=1.6 xB=0.18 CEBAF Large Acceptance Spectrometer

First round experiment at Hall B: E01-113

SLIDE 11

11

LIGHT CONE 2016

• in

bins 24 t in bins 9 ) x , ( in bins 21

B e

• Extraction
• f 4-fold

cross sections

dtd Φ dx dQ σ d

B 2 ep ep 4 γ

• dtd Φ

dx dQ σ d dtd Φ dx dQ σ d

B 2 ep ep 4 B 2 ep ep 4 γ γ

2 1

DVCS kinemac coverage at CLAS

CEBAF Large Acceptance Spectrometer

First round experiment at Hall B: E01-113

plots by H.S. Jo DVCS cross secon measurements

SLIDE 12

12

LIGHT CONE 2016

DVCS cross secons

CEBAF Large Acceptance Spectrometer

First round experiment at Hall B: E01-113

Measurements in a LARGE kinemac domain

KMS VGG KM10 (Kumericki, Mueller) KM10a

PRL115:212003 (2015) H.S. Jo et al. (CLAS collaboration)

SLIDE 13

13

LIGHT CONE 2016

DVCS cross secons

CEBAF Large Acceptance Spectrometer

First round experiment at Hall B: E01-113

fit VGG

0.5 Im

H

• 1

1 2 3 4 5 6 = 0.126

B

x

2

= 1.11GeV

2

Q 0.98

• =

4.25

1

b 0.95

• =

5.30

1

A = 0.126

B

x

2

= 1.11GeV

2

Q

0.5

• 1

1 2 3 4 5 6 = 0.185

B

x

2

= 1.63 GeV

2

Q 0.55

• =

3.03

1

b 0.56

• =

4.98

1

A = 0.185

B

x

2

= 1.63 GeV

2

Q

0.5

• 1

1 2 3 4 5 6 = 0.335

B

x

2

= 2.23 GeV

2

Q 3.68

• =

1.04

1

b 1.25

• =

1.44

1

A = 0.335

B

x

2

= 2.23 GeV

2

Q )

2

• t (GeV

0.1 0.2 0.3 0.4 0.5

Re

H

• 4
• 2

2 4 6 )

2

• t (GeV

0.1 0.2 0.3 0.4 0.5 6 )

2

• t (GeV

0.1 0.2 0.3 0.4 0.5 6

PRL115:212003 (2015) H.S. Jo et al. (CLAS collaboration)

SLIDE 14

14

LIGHT CONE 2016

DVCS target spin asymmetries

• 0.4
• 0.2

0.2 0.4 500 1000 1500 2000 2500

• 0.2

0.2 0.4 50 100 150 200 250

Events

50 100 150 200 250 300 350

• 0.6
• 0.4
• 0.2

0.2 0.4 0.2 0.3 0.4

• 0.2
• 0.1

0.1 0.2 0.3 0.4 0.5 0.15 0.2 0.25

VGG model VGG model

First measurements of DVCS target spin asymmetry:

✦ non-dedicated experiment ✦ no Inner Calorimeter

exclusivity

PRL97:072002 (2006) S. Chen et al. (CLAS collaboration)

CEBAF Large Acceptance Spectrometer

Non-dedicated experiment at Hall B (longitudinally polarized target)

SLIDE 15

15

LIGHT CONE 2016

DVCS target spin asymmetries

CEBAF Large Acceptance Spectrometer

Second round experiment at Hall B: E05-114 (longitudinally polarized target)

PRL114:032001 (2015) E. Seder et al. (CLAS collaboration)

0.1 0.2 0.3 0.4 0.1 0.2 0.3 0.4

This Work CLAS 2006 HERMES 2010 0.4 0.8 1.2 1.6 0.4 0.8 1.2 1.6 0.4 0.8 1.2 0.4 0.8 1.2 0.4 0.8 1.2 0.4 0.8 1.2

0.1 0.2 0.3 0.4 0.1 0.2 0.3 0.4

VGG GK KMM12 GGL

SLIDE 16

16

LIGHT CONE 2016

DVCS Compton form factors

CEBAF Large Acceptance Spectrometer

Second round experiment at Hall B: E05-114 (longitudinally polarized target)

❏ sensivity ❏ wide kinemac coverage ❏ improved precision

0.5 1 1.5 2 2.5 3 3.5 4 0.5 1 1.5 2 2.5

.5 1 1 .5 2 2 .5 .5 1 1 .5 2 2 .5 3

0.2 0.4 0.6 0.8 1 1.2

• 0.2

0.2 0.4 0.6 0.8 1 0.2 0.4 0.6 0.8 1 1.2 0.2 0.4 0.6 0.8 1 1.2 0.2 0.4 0.6 0.8 1 1.2 0.2 0.4 0.6 0.8 1 1.2

PRD91:052014 (2015) S. Pisano et al. (CLAS collaboration)

SLIDE 17

17

LIGHT CONE 2016

Deeply virtual meson producon

e e'

Quark flavor decomposion: ❖ Flavor raos: cancellaon of higher twist effects ❖

Generalized Form Factor

SLIDE 18

18

LIGHT CONE 2016

unpolarized terms longitudinally polarized beam longitudinally polarized beam and longitudinally polarized target longitudinally polarized target

DVMP structure funcons

M B

SLIDE 19

19

LIGHT CONE 2016

unpolarized terms longitudinally polarized beam longitudinally polarized beam and longitudinally polarized target longitudinally polarized target

DVMP structure funcons

SLIDE 20

20

LIGHT CONE 2016

unpolarized terms longitudinally polarized beam longitudinally polarized beam and longitudinally polarized target longitudinally polarized target

DVMP structure funcons

100 200 300 100 200 300

SLIDE 21

21

LIGHT CONE 2016

DVπ0P beam spin asymmetries

1 2 3 4 0.1 0.2 0.3 0.4 0.5

• 0.05

0.05 0.1 0.15 0.2 0.5 1 1.5 α

• 0.05

0.05 0.1 0.15 0.2

• 0.05

0.05 0.1 0.15

• 0.05

0.05 0.1 0.15

• 0.05

0.05 0.1 0.15 0.2

• 0.05

0.05 0.1 0.15 0.2

• 0.05

0.05 0.1 0.15 0.2

• 0.05

0.05 0.1 0.15 0.2

• 0.05

0.05 0.1 0.15 0.2

• 0.05

0.05 0.1 0.15 0.2

• 0.05

0.05 0.1 0.15 0.2

• 0.05

0.05 0.1 0.15 0.2

• 0.05

0.05 0.1 0.15 0.2

• 0.05

0.05 0.1 0.15 0.2

• 0.05

0.05 0.1 0.15 0.2

• R. De Masi et al. Measurement of ep->epπ0 beam

spin asymmetries above the resonance region. Phys.Rev., C77:042201, 2008.

CEBAF Large Acceptance Spectrometer

First round experiment at Hall B: E01-113

0.1 0.2 0.3 Counts/0.002 GeV 5000 10000 15000 20000 25000 0.1 0.2 0.3 30

• 0.1

0.2 0.3 30

• ) (GeV)

γ γ IM ( 0.1 0.2 0.3 30

• PRC77:042201 (2008), R. De Masi et al. (CLAS collaboraon)

Two-photon invariant mass

IC-EC EC-IC IC EC

SLIDE 22

22

LIGHT CONE 2016

B x 0.28 0.3 0.32 0.34 0.36 0.38 0.4 0.42 0.44 ) 2 (GeV 2 Q 1.6 1.8 2.2 2.4 2.6 2 < 1.15 GeV 2 X M

DVπ0P cross secons

PRC83:025125 (2011), E. Fuchey et al. (Hall A collaboraon)

0.05 0.1 0.15 0.2 0.2 0.4 0.6 0.8

2 = 1.9 GeV 2 Q 2 = 2.3 GeV 2 Q (a)

)

2

• t (GeV

m in

t

0.05 0.1 0.15 0.2 0.5 1 (b)

First round experiment at Hall A: E00-110 Leading twist predicts: but:

is likely to dominate at these Q2

but L/T separaon is necessary

kinemac coverage

SLIDE 23

23

LIGHT CONE 2016

DVπ0P cross secons

PRL109:112001 (2012) I. Bedlinskiy et al. (CLAS collaboraon)

solid: P.Kroll & S.Goloskokov dashed: G.R. Goldstein, J.O. Gonzalez & S.Liuti

• 300
• 200
• 100

100 200 300 400 Q2= 1.15 GeV2 xB= 0.13

• 300
• 200
• 100

100 200 300 400 Q2= 1.61 GeV2 xB= 0.19

• 300
• 200
• 100

100 200 300 400 Q2= 1.74 GeV2 xB= 0.22

• 300
• 200
• 100

100 200 300 400 Q2= 2.21 GeV2 xB= 0.28

• 300
• 200
• 100

100 200 300 400 0.2 0.4 0.6 0.8 1 1.2 1.4 Q2= 2.71 GeV2 xB= 0.34

• 300
• 200
• 100

100 200 300 400 0.2 0.4 0.6 0.8 1 1.2 1.4 Q2= 3.22 GeV2 xB= 0.41 dσ/ dt [nb/ Ge V2]

• t, GeV2
• t, GeV
• t, GeV2
• t, GeV

CEBAF Large Acceptance Spectrometer

First round experiment at Hall B: E01-113

Inclusion of the Chiral-odd GPDs brings theorecal calculaons into moderate agreement with the data.

π0 electroproducon is uniquely sensive process to access transversity GPDs.

SLIDE 24

24

LIGHT CONE 2016

DVπ0P spin asymmetries

PRELIMINARY

Goloskokov-Kroll Goldstein-Liu

TARGET SPIN ASYMMETRY DOUBLE SPIN ASYMMETRY

CEBAF Large Acceptance Spectrometer

Second round experiment at Hall B: E05-114 (longitudinally polarized target)

DVπ0P single and double spin asymmetry measurements are underway

.5 1 1 .5 .2 .4 .3 .2 .1 .5 1 1 .5 .3 .2 .4 .6 .8 .2 .4 .5 1 1 .5 .5 1 1 .5

PRELIMINARY

SLIDE 25

25

LIGHT CONE 2016

η and π0 unpolarized structure funcons

• I. Bedlinskiy et al.

π0 η σu σTT

Q2=2.2 GeV2 xB=0.28 Q2=2.2 GeV2 xB=0.28

σLT

• I. Bedlinskiy et al.

σU - drops by a factor of 2.5 for η ❖ σTT - drops by a factor of 10 ❖ GK model (curves) follows the experimental data ❖ The statement about the transversity GPD dominance in the pseudoscalar electroproducon becomes more solid with inclusion of η data ❖

CEBAF Large Acceptance Spectrometer

SLIDE 26

26

LIGHT CONE 2016

η/π0 rao

.1 .2 .3 .4 .5 .6 .7 .8 .9 1 .1 .2 .3 .4 .5 .6

Q2= 1 .2 5 Ge V2 Q2= 1 .7 5 Ge V2 Q2= 2 .2 5 Ge V2 Q2= 2 .7 5 Ge V2 Q2= 3 .2 5 Ge V2

Rao

Chiral-odd GPD models predict this rao to be ~1/3 at CLAS kinemacs Chiral-even GPD models predict this rao to be around 1

CEBAF Large Acceptance Spectrometer

SLIDE 27

27

LIGHT CONE 2016

η and π0 generalized form factors

SLIDE 28

28

LIGHT CONE 2016

Preliminary

1 1 .5 1 1 .5 2

• t Ge

V2

• t Ge

V2

• t Ge

V2

• t Ge

V2 1 1 .5 1 1 .5 2

• t Ge

V2

• t Ge

V2

• t Ge

V2

• t Ge

V2 1 1 .5 1 1 .5 2

• t Ge

V2

• t Ge

V2

• t Ge

V2

• t Ge

V2 1 1 .5 1 1 .5 2

• t Ge

V2

• t Ge

V2

• t Ge

V2

• t Ge

V2 Q2 GeV2 xB 1.2 0.15 1.8 0.22 2.2 0.27 2.7 0.34

η and π0 generalized form factors

The first extracon of the Generalized Form Factors ET>HT for both mesons t-dependence is steeper for ET than for HT The Generalized Form Factors extracted from experimental

• bservables

constrain exisng GPDs parametrizaons

❖ ❖ ❖ ❖

• allow to perform

flavor decomposion

P R E L I M I N A R Y

• V. Kubarovsky, arXiv:1601.04367

SLIDE 29

29

LIGHT CONE 2016

η and π0 generalized form factors

❖ ❖ ❖

• V. Kubarovsky, arXiv:1601.04367

<HT>u and <HT>d have different signs for u and d quarks in accordance with the transversity funcon h1 (Anselmino et al.)experimental

• bservables

<ET>u and <ET>d have the same sign The u/d decomposion was done under assumpon that the relave phases between u and d quarks is 0 or 180 degrees, and u quark was chosen to have posive values

T T T T T T

SLIDE 30

30

LIGHT CONE 2016

PRELIMINARY

Beam spin asymmetries:

and

CEBAF Large Acceptance Spectrometer

.2 .4 .2 .4 .5 1 .2 .4 .5 1 .2

GGL GK

SLIDE 31

31

LIGHT CONE 2016

CLAS12 upgrade

The combinaon of high beam intensity with large acceptance detectors allows for precise measurements of "rare" processes such as deep exclusive reacons: CLAS12 is uniquely suited for simultaneous detecon of various DVMP channels ❖

12 GeV kinemac coverage

0.1 0.3 0.5 0.7 1 5 9

Expansion

• f

the kinemac coverage provides the opportunity to test the mechanism

• f

pseudoscalar meson electroproducon in great details and perform the separaon of the contribuons from the different chiral-odd GPDs ❖

0.18 0.23 0.27 0.33 0.43 0.51

NO DATA EXIST!

will be accessed by CLAS12 at 12 GeV

1 0.25 0.50 0.75 3 5 7 9

[LoI at PAC42]

SLIDE 32

32

LIGHT CONE 2016

Summary

Large data set (cross secons, single and double spin asymmetries) in the wide kinemac region is available ✦ Large number of experimental observables provide ghter constraints for parametrizaons of underlying GPDs DVCS and DVMP provide access to the chiral-even and chiral-odd GPDs. ✦ ✦ ✦ Combinaon of polarized and unpolarized observables provide constraints for t dependence on underlying GPDs and will help to establish the role of transversity in pion electroproducon ✦ Compeling GPD program in the future at JLab at 12 GeV...