JPARC DY Workshop, April 7 Ralf Seidl (RBRC) R.Seidl: Transverse Spin 1RIKEN, April 7 In JPARC Drell...

JPARC DY Workshop, April 7

Ralf Seidl (RBRC)

R.Seidl: Transverse Spin 1RIKEN, April 7

In JPARC Drell Yan accessible with: UU (unpolarized beam, unpolarized target)UT (unpolarized beam, transversely polarized target)TU (transversely polarized beam, unpolarized target)TT (transversely polarized beam, transversely

polarized target)

Outline

Introduction of TMDs and TransversityBoer-Mulders Function

Existing DY resultsCOMPASS , RHIC(?), FAIR(??)

Sivers FunctionSIDIS results and global analysisCurrent inclusive RHIC SSAs, future DY , COMPASS,

FAIR(??)Transversity

SIDIS results , global analysisComparison to Lattice predictions Evolution of

Collins FF(?) other measurements at RHIC(Collins, IFF) , SIDIS

(IFF, )R.Seidl: Transverse Spin RIKEN, April 7 2

In DY: UU

In DY: TUor UT

In DY: TT

Unpol. DF

Helicity

Transversity

Transversity and friends

Sivers function

Boer-Mulders function

q(x)

q(x)

q(x)

Tf1

1h

Lh1

Th1

Tg1

R.Seidl: Transverse Spin 3RIKEN, April 7

Boer Mulders measurements

Lam Tung relation: in leading order term should be zero Experiments see large cos asymmetries in +nuclear Drell Yanpossible explanationsvacuum polarization

(Nachtmann, Brandenburg) Boer Mulders function:

R.Seidl: Transverse Spin RIKEN, April 7 4

2cossin

2cos2sincos1

1 22

d

d

a

aaa

at

at

aa

xfxfe

kxhkxhe

)()(

),(),(

2 11112

11112

In DY: UU

Boer Mulders

E866 sees vanishing asymmetries on p+d DY


In DY: UU

Is it the isoscalar target? Or maybe the valence like antiquark in

Models and Lattice suggest, that u and d Boer Mulders function have similar sign

Unless the sea has opposite signs for u and d then this cannot explain smallness

However valence Boer mulders function in pion could

Gluon radiative effect becomes dominant at higher QT

Does that effect behave differently?


In DY: UU

Boer Mulders in SIDIS and future DYDifficult AUU

Asymmetrywhich contains convolution of Boer-Mulders function and Collins fragmentation function

Concurrent with Cahn-effect

For unpolarized asymmety acceptance effects in non 2 detectors

Analysis ongoing in HERMES, COMPASS and CLAS

In DY: COMPASS DY measurements (again large asymmetries?)

PANDA (FAIR) :only one they can do , some day


In DY: UU

RIKEN, April 7 8

Sivers function measurements I asymmetries clearly

positive First evidence of a

nonzero TMD K- asymmetries

consistent with zeroK+ asymmetries 2.3 times

larger than hard to explain

Consistent sign of Sivers functions as from M.Burkhardt’s chromodynamic lensing

R.Seidl: Transverse Spin

In DY: TUor UT

RIKEN, April 7 9

R.Seidl: Transver

se Spin

Sivers function measurements II

Results for all 3 pion states consistent with isospin symmetry

In DY: TUor UT

10

R.Seidl: Transver

se Spin

deuteron target transversely polarisedcharged hadrons (mostly pions)• 2004: results from 2002 data PRL94(2005)202002 confirmed by• 2006: results from 2002-2004 data NPB765(2007)31

Sivers asymmetry III

asymmetries compatible with zero within the statistical errors

(systematic errors much smaller)RIKEN, April 7

In DY: TUor UT

RIKEN, April 7 11

R.Seidl: Transver

se Spin

Sivers measurements IVAgain, 2003-

2004 data for identified hadrons

In DY: TUor UT

RIKEN, April 7 12

R.Seidl: Transver

se Spin

Sivers global analysisSimultaneous fit of

HERMES (02-04) and COMPASS (03-04) data on charged pions

u and d Sivers functions of nearly equal size and opposite sign

Vogelsang, Yuan

Anselmino et al

Collins et al

Anselmino et al

Also available:

Efremov,Goeke, Schweitzer

In DY: TUor UT

measurements in the near future

COMPASS proton targetImportant test of

the HERMES results in the overlap region

JLAB 6 and 12 GeVLow energies and

multiplicities


COMPASS, arXiv:0802.2160

In DY: TUor UT

Improvements in theoretical understanding will allow RHIC AN to be used

Fitting HERMES and COMPASS Sivers data,

Take Collins contribution into account and

Calculate phases to describe RHIC AN results

Pion asymmetries fairly well described

At least same sign for both K asymmetries as in data

Theoretical interpretations not yet consistent F.Yuan (Phys.Rev.Lett.100:032003,2008. )


Boglione, D’Alesia, Murgia e-Print: arXiv:0712.4240 [hep-ph]

STAR asymmetries:

Brahms asymmetries (200GeV):

In DY: TUor UT

Sivers back-to-back jet measurements


Emphasizes (50%+ ) quark Sivers

AN consistent with zero in central region Partial cancellation of SIDIS –like and DY –like

contributions from Sivers function

-VY 1, VY 2 are calculations by Vogelsang & Yuan, PRD 72 (2005) 054028-Bomhof et al PRD 75, (2007) 074019

STAR,PRL,99(2007)142003 In DY: TUor UT

RIKEN, April 7 16

R.Seidl: Transver

se Spin 0.1 0.2 0.3 x

Siv

ers

Am

plit

ude

0

Experiment SIDIS vs Drell Yan: Sivers|DIS= − Sivers|DY

*** Test QCD Prediction of Non-Universality ***HERMES Sivers

Results

Markus DiefenthalerDIS WorkshopMűnchen, April 2007

0RHIC II Drell Yan Projections

Feng YuanWerner Vogelsang

In DY: TUor UT

RIKEN, April 7 17R.Seidl: Transverse Spin

Transversity properties

Does not couple to gluons different QCD evolution than q(x)

Valence dominated Comparable to Lattice calculations, especially tensor charge:

Test relativistic nature of quarks in the nucleon

Positivity bound:

Soffer bound:

xqxδq

xqxqxδq 21

1

0

)()( xqxqdxgT

In DY: TT

RIKEN, April 7 18

R.Seidl: Transver

se Spin

How to access Transversity another chiral-odd function

Drell Yan: Combine two

Transversity distributions with each other

SIDIS: Combine

Transversity distributions with chiral-odd fragmentation function (FF)

Total process is chiral-even: OK

Possible Partners: Collins FF Interference FF Transverse L FF

Most require single spin asymmetries in the fragmentation

In DY: TT

RIKEN, April 7 19

R.Seidl: Transver

se Spin

First successful attempt at a global analysis for the transverse SIDIS and the BELLE Collins data

HERMES AUT p data

COMPASS AUT d data

Belle e+ e-

Collins dataKretzer FF

First extraction of transversity (up to a sign)

Anselmino et al: hep-ex 0701006

Tensor charges obtained from this fit (from Alexei Prokudin) at Q2= 2.4 GeV2:

0.340 +0.398 -

0.346 +0.392 -

189.0195.0

150.0203.0

0.236

0.569

166.0

403.0

du

du

d

u

In DY: TT

Current problems in the global transversity analysisUniversaliy? Is the Collins function from e+e-

the same in SIDIS, how about pp? According to Bacchetta et al.

and Gamberg et al, yesEvolution?

Is the evolution of transversity understood? YesIs the evolution of the Collins function understood?

Not really – is this the reason for low transversity in the global fit so far?

Error treatment, first suggestions to start a CTEQ-like transversity global analysis group with contributors from Theory (Torino), COMPASS(Trieste),HERMES(Ferrara), Belle(Illinois, RBRC)


In DY: TT

RIKEN, April 7 21

R.Seidl: Transver

se Spin

Collins measurements IIK+ asymmetries

compatible with asymmetries (through u quark dominance)

K- asymmetries maybe slightly positive

In DY: TT

Coming additions to global analysis


Very important Test: COMPASS proton data-•Will it be consistent in the overlap with HERMES?•Will they be different

arXiv:0802.2160

COMPASS full d data set,Charged , K and KS

In DY: TT

Further additions

Belle 547 fb-1 data setJLAB 6 and 12 GeV

Low energies and multiplicities

Higher twist an issue?


In DY: TT

Other channels: IFF, polarizationHERMES,COMPASS,pp, BELLE


RIKEN, April 7 25

R.Seidl: Transver

se Spin

DY transversity measurements at RHIC, JPARC and FAIR

DY transverse double spin asymmetries golden channel to Transversity:

Requires both (anti)- protons transversely polarized

For mostly sensitive to u-quark transversity

For pp smaller asymmetries due to sea transversity , but for tensor charge absolutely necessary

)()( xqxqATT

pp

Q= 8GeV

Q= 3GeV

Q= 5GeV

Q=15GeV

RHIC @ √s=200GeV

JPARC @ √s=10 GeV

Kawamura et. alNucl.Phys.B777:203-225,2007.

Assuming Soffer bound

In DY: TT

RIKEN, April 7 26

R.Seidl: Transver

se Spin

Transversity access over DY in single spin asymmetries

Instead of double spin asymmetries measure single spin asymmetries

Advantage: only one proton polarized better FOM at RHIC, earlier feasible at JPARC and GSI

Disadvantage: first have to measure Boer-Mulders function with good precision

Also planned at COMPASS with pion beam

)()(1 xqxhAT

Q=2GeV

Q=3GeV

Q=4GeV

Q=6GeVGSI (collider option) @ √s=15 GeV

Kawamura et. alNucl.Phys.B777:203-225,2007.

Theory for ATT fairly well understood even at very low scales,

if there will be PAX, it will measure mostly u2 – until then already relatively well known only consistency test

Transversity over pp DY in double spin asymmetries

In DY: TT

SummaryBoer Mulders function:

not at all well defined, hopefully some improvements until JPARC DY, but not much

Important JPARC DY measurement even w/o polarization (UU)

Sivers function: Fairly well known from SIDIS, but at low scalesInclusion of pp asymmetries possible, soon?Universality test will be absolutely crucial, then sea

Sivers functions measurements (UT)Transversity:

First global analysis available, errors still huge, evolution of Collins function?New accesses over IFF, polarimetry soonClean experiment, sensitive to sea transversity in (TT)


RIKEN, April 7 29

R.Seidl: Transver

se Spin

Transversity In helicity basis: helicity

distribution and momentum difference and sum of diagonal amplitudes

Transversity contains helicity flip and is not diagonal

Helicity is conserved quantity for (nearly) massless quarks

All interactions conserve helicity/chirality

Transversity cannot be observed in DIS

RIKEN, April 7 30

R.Seidl: Transver

se Spin

q(x), G(x)

Difference of quarks with parallel and antiparallel polarization relative to longitudinally polarized proton(known from fixed target (SI)DIS experiments)

q(x),G(x)Sum of quarks with parallel and antiparallel polarization relative to proton spin(well known from Collider DIS experiments)

q(x)

Quark distributions in spin bases

Difference of quarks with parallel and antiparallel polarization relative to transversely polarized proton(first results from HERMES and COMPASS – with the help of Belle)

Unpolarized distribution function q(x)

Helicity distribution function q(x)

Transversity distribution function q(x)

JPARC DY Workshop, April 7 Ralf Seidl (RBRC) R.Seidl: Transverse Spin 1RIKEN, April 7 In JPARC Drell...

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Transcript of JPARC DY Workshop, April 7 Ralf Seidl (RBRC) R.Seidl: Transverse Spin 1RIKEN, April 7 In JPARC Drell...