h. avakian, trento, oct 11 1 transversity program at clas h.avakian (jlab) gpd-2010 trento, oct...

H. Avakian, Trento, Oct 111

Transversity program at CLASTransversity program at CLAS

H.Avakian (JLab)H.Avakian (JLab)

GPD-2010 Trento, Oct 11-15GPD-2010 Trento, Oct 11-15

•Physics motivation•kT-effects with unpolarized and longitudinally polarized target data•Physics with transversely polarized hadrons and quarks•Future studies of 3D PDFs at CLAS at 6 GeV •Transverse structure & CLAS12

•Summary


Some questions to address

• What is the shape of kT-distributions?• Are there correlations between transverse space and momentum

distributions?• Can kT-distributions be flavor dependent?• Are kT-distributions the same for different spin orientations?• How spin-orbit correlations change the momentum distributions?• What is the fraction of kT-generated in FSI?• How quark-gluon correlations affect transverse momentum and space

distributions?• How nuclear medium changes kT and bT-distributions?• How gluons and sea are distributed in kT

How spin-orbit correlations are related to the longitudinal structure and nuclear effects?


Single hadron production in hard scattering

Measurements in different kinematical regions for nucleon and nucleus provide complementary information on the complex nucleon structure.

xF - momentum

in the CM frame

xF>0 (current fragmentation)

xF<0 (target fragmentation)

h

h

Target fragmentation Current fragmentation

Fracture Functions

xF

M

0-1 1

h

h

TMD GPD

kT-dependent PDFs Generalized PDFs

PDF

hFF

DA DA

exclusivesemi-inclusive semi-exclusive


Structure of the Nucleon

d2kT

PDFs q(x), q(x)…

d2rT x-kT and x-rT

correlations define the final x-distributions

d2k T

Wpu(k,rT) “Mother” distributions (Wigner, GTMDs,..)

d2r T

TMD PDFs q(x,kT), q(x,kT)…

GPD/IPDs H(x,rT), H~(x,rT)…

In nuclear env. TMDs and GPDs modify


Nucleon TMDs

+ Higher twist distribution functions

quark polarization


Cross section is a function of scale variables x,y,z

z

SIDIS kinematical plane and observablesSIDIS kinematical plane and observables

U unpolarized

L long.polarized

T trans.polarizedBeam polarizationTarget polarization

sin2moment of the cross section for unpolarized beam and long. polarized target


Scattering of 5.7 GeV electrons off polarized proton and deuteron targets

SIDIS with JLab at 6 GeVSIDIS with JLab at 6 GeV

DIS kinematics, Q2>1 GeV2, W2>4 GeV2, y<0.85 0.4>z>0.7, MX

2>2 GeV2

2

eX

Large PT range and full coverage in azimuthal angle crucial for studies


CLAS configurationsCLAS configurations

e

ep→e’X

Polarizations:Beam: ~80%NH3 proton 80%,ND3 ~30%HD (H-75%,D-25%)

1) Polarized NH3/ND3 (no IC, ~5 days)2) Unpolarized H (with IC ~ 60 days)3) Polarized NH3/ND3 with IC 60 days

10% of data on carbon 4) Polarized HD-Ice (no IC, 25 days)

Inner Calorimeter

Unpolarized, longitudinally and transversely polarized targets

Unpolarized and longitudinally polarized targets

HD-Ice

0.05 K0.6 K

1 K4K


Some analysis topics for latest polarized proton and deuteron target data

SIDIS with JLab at 6 GeVSIDIS with JLab at 6 GeV

•Inclusive g1p •Inclusive g1d•DVCS AUL on proton•DVCS AULon neutron•DVCS ALL

•SIDIS AUL & ALL for pions on proton•SIDIS AUL & ALL for pions on deuteron•SIDIS AUL & ALL for kaons and on proton

•Modifications of azimuthal moments in nuclei

Large acceptance of CLAS allows simultaneous measurements of hard exclusive and semi-inclusive reactions providing complementary information on the complex nucleon structure.


A1 PT-dependence in SIDIS

M.Anselmino et al hep-ph/0608048

+ A1 suggests broader kT distributions for f1 than for g1

- A1 may require non-Gaussian kT-dependence for different helicities and/or flavors

02=0.25GeV2

D2=0.2GeV2

0.4<z<0.7

arXiv:1003.4549


A1

A1 PT-dependence

CLAS data suggests that width of g1 is less than the width of f1

AnselminoCollins

Lattice

New CLAS data would allow multidimensional binning to study kT-dependence for fixed x

PT

PT

arXiv:1003.4549


Quark distributions at large kQuark distributions at large kTT: lattice: lattice

B.Musch arXiv:0907.2381

12

u/u

(dipole formfactor), J.Ellis, D-S.Hwang, A.Kotzinian

JMR model

q

DqMR , R=s,a


Quark distributions vs bQuark distributions vs bTT


13

What we gain modeling + and – distributions for GPDs?

Difference in final distributions when using f1,g1 or q+,q-


Quark distributions at large kQuark distributions at large kTT: lattice: lattice

Higher probability to find a d-quark at large kT


H. Mkrtchyan et al. Phys.Lett.B665:20-25,2008.

http://www.slac.stanford.edu/spires/find/hep/wwwauthors?key=7359527




~10% of E05-113 data

15

Longitudinal Target SSA measurements at CLASLongitudinal Target SSA measurements at CLAS

p1sin+p2sin2

0.12<x<0.48

Q2>1.1 GeV2

PT<1 GeV

ep→e’X

W2>4 GeV2

0.4<z<0.7

MX>1.4 GeV

y<0.85

p1= 0.059±0.010p2=-0.041±0.010

p1=-0.042±0.015p2=-0.052±0.016

p1=0.082±0.018p2=0.012±0.019

CLAS-2009 (E05-113)CLAS PRELIMINARY

CLAS-2000

Data consistent with negative sin2 for +


Kotzinian-Mulders Asymmetries

B.Musch arXiv:0907.2381B.Pasquini et al, arXiv:0910.1677

HERMES

CLAS (5 days)

Worm gear TMDs are unique (no analog in GPDs)


Beam SSA: ALU from CLAS @ JLab

0.5<z<0.8

Beam SSA from hadronization (Collins effect) by Schweitzer et al.

Photon Sivers Effect Afanasev & Carlson, Metz & Schlegel

Beam SSA from initial distribution (Boer-Mulders TMD) F.Yuan using h1

┴ from MIT bag model

Collins contribution should be suppressed → g┴ wanted !!!


Exclusive and from CLAS

e p e p e pe p π+ π-

e- p e- n+π+π0

+

•Measurements of ratios , … Ju,Jd

Gluon exchange at low W suppressed (x-sections for and comparable)Quark exchange, which dominates, can be considered as part of SIDIS


+ SSA from

+ SSA has a significant dependence on the source process

Modulation exist even for vanishing helicity change amplitudes


Exclusive pion beam SSA @CLAS6

Sign flip at z ~ 0.5

At z<0.5 struck quark in neutron


21

HT and Semi-Exclusive Pion Production

A.Afanasev, C.Carlson, C. Wahlquist Phys.Lett.B398:393-399,1997

+

Fragmentation +

0

HT effects and exclusive 0 suppressed

Dominant contribution to meson wave function is a perturbative one gluon exchange and approach its validity at factor ~3 lower Q2 than in case of hard exclusive scattering.

How big is the rho semi-exclusive production compared to pion?


GPDs from cross section ratios

•Study ratio observables: K/K*/+,polarization transfer•Different final state mesons filter out different combinations of unpolarized (H,E) and polarized (H,E) GPDs.

M.Diehl et al. hep-ph/0506171

K*+

K+


1. Small field (∫Bdl~0.005-0.05Tm)2. Small dilution (fraction of events

from polarized material)3. Less radiation length4. Less nuclear background (no nuclear

attenuation)5. Wider acceptance

CLAS transversely polarized HD-Ice targetHD-Ice target vs std nuclear targets


Collins SSAsCollins SSAs

CLAS with a transversely polarized target will allow measurements of transverse spin distributions and constrain Collins fragmentation function

Anselmino et al H.A.,A.Efremov,P.Schweitzer,F.Yuan

helicity-transversity=pretzelosity

CLAS E08-015 (2011)


Measurement of Sivers function and GPD-E

DVCS Transverse asymmetry (function of momentum transfer to proton) is large and has strong sensitivity to GPD-E

CLAS will provide a measurements of Sivers asymmetry at large x, where the effect is large and models unconstrained by previous measurements.

Meissner, Metz & Goeke (2007)

GPD-E=0

(DVCS) (SIDIS) CLAS E08-015


Quark distributions at large kQuark distributions at large kTT

Higher probability to find a hadron at large PT in nuclei

kT-distributions may be wider in nuclei?

PT = p┴ +z kT bigger effect at large z

Understanding of modification of kT widths in nuclei is important also for nucleon TMDs


kT and FSI

l l’

x,kT

proton

spectator system

•The difference is coming from final state interactions (different remnant)•Studies of DIS and SIDIS with nuclear targets provide info on kT

Tang,Wang & Zhou

Phys.Rev.D77:125010,2008

BHS 2002Collins 2002Ji,Yuan 2002

lT

l l’

x,k’T l’T

spectator systemnucleus

total transverse momentum broadening squared

soft gluon exchanges included in the distribution function (gauge link)


Modification of Cahn effect

Bag model

arXiv:1001.3146 Gao, Liang & Wang

•Nuclear modification of Cahn may provide info on kT broadening and proton TMDs 28


CHL-CHL-22

Beam Current: 90 µAMax Pass energy: 2.2 GeVMax Enery Hall A,B,C: 11 GeV

May 2012

6 GeV Accelerator Shutdown starts

May 2013 Accelerator Commissioning starts

2013-2015

Pre-Ops (beam commissioning)

Solenoid 5T

DC R1, R2, R3 LTCC

HTCC

FTOF

PCAL

EC

CLAS12

L = 1035 cm-2s-1

Primary goal of experiments using CLAS12: study of the internal nucleon dynamics by accessing GPDs &

TMDs detector tuned for studies of exclusive and semi-inclusive

reactions in a wide kinematic range. Large acceptance detector and high luminosity capabilities

CEBAF @ 12 GeV and CLAS12


E12-06-112:E12-06-112: Pion SIDIS E12-09-008: E12-09-008: Kaon SIDIS

E12-07-107:E12-07-107: Pion SIDIS E12-09-009: E12-09-009: Kaon SIDIS

LOI12-06-108: LOI12-06-108: Pion SIDISLOI12-09-004: LOI12-09-004: Kaon SIDIS

PAC approved experiments & LoI

Nq

U

L

T

Complete program of TMDs studies for pions and kaons

Kaon measurements crucial for a better understanding of the TMDs “kaon puzzle”

Kaon SIDIS program requires an upgrade of the CLAS12

detector PID RICH detector to replace LTCCProject under development

TMDs program @ 12 GeV in Hall B


K/K* and separations

Detection of K+ crucial for separation of different final states (,K*)


CLAS12: Kinematical coverage

Large Q2 accessible with CLAS12 are important for separation of HT contributions

Q2>1GeV2

W2>4 GeV2(10)y<0.85MX>2GeV

SIDIS kinematics

eX


Longitudinally polarized target: Double spin asymmetries


Collins fragmentation: Longitudinally polarized target

•Study the Collins function of kaons•Provides independent information on the RSMT TMD

Kotzinian-Mulders Asymmetry

proton deuteron

Pasquini et al.


Pretzelosity @ CLAS12:

•CLAS12 will provide pretzelosity measurement in the valence region for Kaons and pions.

B. Pasquini et al. arXiv:0806.2298

Exciting relation:(in bag & spectator model)

g1q (x) h1

q (x)h1Tq (x)

helicity - transversity = ‘measure’ of relativistic effects

http://www.slac.stanford.edu/spires/find/wwwhepau/wwwscan?rawcmd=fin+%22Pasquini%2C%20B%2E%22

http://www.slac.stanford.edu/spires/find/wwwhepau/wwwscan?rawcmd=fin+%22Pasquini%2C%20B%2E%22


Nonperturbative TMDPerturbative region

PT-dependence of beam SSA

sinLU(UL) ~FLU(UL)~ 1/Q (Twist-3)

1/PT

Check of the higher twist nature of observed SSA criticalSSA test transition from non-perturbative to perturbative region

1/Q


Sivers effect in the target fragmentation

A.Kotzinian

High statistics of CLAS12 will allow studies of kinematic dependences of the Sivers effect in target fragmentation region

xF>0 (current fragmentation)

xF<0 (target fragmentation)

Fracture Functions

Mh


production in the target fragmentation

xF - momentum

in the CM frame

Combination of CLAS12 and EIC would allow studies of hadronization in the target fragmentation region (fracture functions) in a wide range of x

polarization in TFR provides information on contribution of strange sea to proton spin

Study polarized diquark fracture functions sensitive to the correlations between struck quark transverse momentum and the diquark spin.

x F(

)EIC CLAS12

(ud)-diquark is a spin and isospin singlet s-quark carries whole spin of uds

Sivers-2009


Deeply Virtual Compton Scattering ep→e’p’

GPD combinations accessible as azimuthal moments of the total cross section.

DVCSBH

LU~ sin{F1H( ,t) + (F1+F2)H +kF2E}

~Polarized beam, unpolarized target:

Unpolarized beam, longitudinal target:

UL~ sin{F1H+(F1+F2)(H +.. }~

Unpolarized beam, transverse target:

UT~ cos{k(F2H – F1E) + …. }

= xB/(2-xB ),k = t/4M2

Kinematically suppressed




CLAS12 - DVCS/BH Target Asymmetry

Transversely polarized target

e p ep

UT~ cosIm{k1(F2H – F1E) +…}d

Q2=2.2 GeV2, xB = 0.25, -t = 0.5GeV2E = 11 GeV

Sample kinematics

AUTx Target polarization in scattering plane

AUTy Target polarization perpendicular to scattering plane

DVCS Transverse asymmetry (function of momentum transfer to proton) is large and has strong sensitivity to GPD-E

Meissner, Metz & Goeke (2007)


Summary

•CLAS longitudinally polarized NH3 and ND3 target data provides superior sample of events allowing detailed studies of single and double spin asymmetries using multidimensional bins

Measurements of spin and azimuthal asymmetries with unpolarized, longitudinally polarized and transversely polarized targets in semi-inclusive processes at JLab :

•Measure TMDs of partons in the valence region•Provide detailed info on partonic spin-orbit correlations •Study quark-gluon correlations (HT)•Study nuclear modification of 3D PDFs

CLAS12 will significantly increase the luminosity, kinematical coverage and particle identification capabilities of CLAS6


Support slides….


SSA in ep->e’X

Strange pattern: 0 SSA bigger at very low and very large z

HERMES 27.5 GeVCLAS 5.7 GeV


Quark distributions at large kQuark distributions at large kTT

Higher probability to find a hadron at large PT in nuclei

kT-distributions may be wider in nuclei?

PT = p┴ +z kT

bigger effect at large z

Understanding of modification of kT widths in nuclei is important also for nucleon TMDs


HDice

• polarized targets of solid hydrogen, +HD (E06-101); e+HD (E08-021)• polarize to frozen-spin state at 12 mK, 15 tesla in new HDice Lab• transfer to CLAS In-Beam-Cryostat

• renovated Lab in Test Lab Annex• installing polarizing equip• assembling Oxford dilution fridge - training SC magnet• new NMR electronics under test - optimize H D spin transfer• fabricating CLAS target cells• HD purity analysis prep time - chromatography & Raman scat

HDice

• polarized targets of solid hydrogen, +HD (E06-101); e+HD (E08-021)• polarize to frozen-spin state at 12 mK, 15 tesla in new HDice Lab• transfer to CLAS In-Beam-Cryostat

• renovated Lab in Test Lab Annex• installing polarizing equip• assembling Oxford dilution fridge - training SC magnet• new NMR electronics under test - optimize H D spin transfer• fabricating CLAS target cells• HD purity analysis prep time - chromatography & Raman scat

HDiceLab

HDiceLab

HallB

HallB


HDice In-Beam Cryostat for CLAS

HDiceTransferCryostat

• designed for both (Start Counter) and e- (mini-Torus)

• ASME code review nearly complete

• under construction

0.05 K0.6 K

1 K4 K

HDice IBC-CLAS loading

HDice In-Beam Cryostat


Kaon TMDs program @ 12 GeV in Hall B

K+

K--

+

• K+ ampl. > + ampl. Unespected from u-quark dominance!

• How large can the effect of s quarks be?

HERMES coll. PRL 103 (2009)

/K measurement @ CLAS12 will provide a more detailed knowledge of Sivers effect

epe’K+X

S.Arnold et al.0805.2137

M. Anselmino et al.0805.2677


kT and FSI

l l’

x,kT

proton

spectator system

•The difference is coming from final state interactions (different remnant)•Studies of DIS and SIDIS with nuclear targets provide info on kT

Tang,Wang & Zhou

Phys.Rev.D77:125010,2008

BHS 2002Collins 2002Ji,Yuan 2002

lT

l l’

x,k’T l’T

spectator systemnucleus

total transverse momentum broadening squared

~4 n, with ~4-6 MeV

soft gluon exchanges included in the distribution function (gauge link)


CLAS slightly lower, but may have bigger

Anselmino et al from EMC data → = 0.25 Wider at smaller beam energies?

Transverse momentum distributions of hadrons

Gauss

49


coscos moment in A moment in ALLLL-P-PTT-dependence-dependence

PT-dependence of cos moment of double spin asymmetry is most sensitive to kT-distributions of quarks with spin orientations along and opposite to the proton spin.

hep-ph/0608048

02=0.25GeV2

D2=0.2GeV2

CLAS PRELIMINARY


Jet limit: Higher Twist azimuthal asymmetriesJet limit: Higher Twist azimuthal asymmetries

No leading twist, provide access to quark-gluon correlations

T-odd

H.A.,A.Efremov,P.Schweitzer,F.Yuan Phys.Rev.D81:074035,2010

“interaction dependent”

Twist-2

Twist-3


A1 PT-dependence in SIDIS


•ALL ) sensitive to difference in kT distributions for f1 and g1 •Wide range in PT allows studies of transition from TMD to perturbative approach

02=0.25GeV2

D2=0.2GeV2

Perturbative limit calculations available for :

J.Zhou, F.Yuan, Z Liang: arXiv:0909.2238


JLab12

EIC

ENC

Q2

Electroproduction kinematics: JLab12→EIC

JLab 0.1<xB<0.7 JLab@12GeV

Study of high x domain requires high luminosity, low x higher energies

EIC

collider experiments

H1, ZEUS 10-4<xB<0.02

EIC 10-4<xB<0.3gluons (and quarks)

fixed target experiments

COMPASS 0.006<xB<0.3

HERMES 0.02<xB<0.3

gluons/valence and sea quarks

valence quarks

EIC (4x60):

ENC (3x15):


AALLLL P PTT-dependence in SIDIS-dependence in SIDIS


•New experiment with 10 times more data will study the PT-dependence for different quark helicities and flavors for bins in x to check if 0< 2

02=0.25GeV2

D2=0.2GeV2

0.4<z<0.7

E05-113


H. Avakian, JLab, May 35555

SIDIS: partonic cross sections

kT

PT = p┴ +z kT

p┴

Ji,Ma,Yuan Phys.Rev.D71:034005,2005

Is the info on x-kT correlations accessible in kT integrated observables?


Extracting widths from A1

Assuming the widths of f1/g1 x,z and flavor independent

Anselmino et al

Collins et al

Fits to unpolarized data

EMC


Dilution factor in SIDIS

Multiple scattering and attenuation in nuclear environment introduces

additional PT-dependence for hadrons

Fraction of events from polarized hydrogen in NH3

Nu,Np -total counts from NH3 and carbon normalized by lumi

u, p -total areal thickness of hydrogen (in NH3), and carbon target

Cn=Nitr/Carbon ratio (~0.98)Diff. symbols for diff x-bins

-


EMC Effect

I. Cloet (Argonne-2010)

NJL-model In medium quarks are more relativisticq more sensitive to angular momentumLower components of wavefunctions more enhancedLower components carry more angular mom.

58H. Avakian, JLab, May 3

In medium modificationMass, magnetic moment, sizeForm factors, PDFs, GPDs, TMDs, etc

How sensitive are inclusive measurements to the transverse structure of nucleon and nucleus ?

h. avakian, trento, oct 11 1 transversity program at clas h.avakian (jlab) gpd-2010 trento, oct...

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