Transverse Spin Effects and TMDs in SemiInclusive DIS

Transverse Spin Effects and TMDs in Semi-Inclusive DIS from the COMPASS Experiment at CERN Rainer Joosten University of Bonn Cambridge, July, 26 2011

COMPASS • high energy beam • large angular acceptance • broad kinematical range 0. 003 < x < 0. 7 10 -3 < Q 2 < 102 (Ge. V/c)2 two stage spectrometer Large Angle Spectrometer (SM 1), Small Angle Spectrometer (SM 2) beam: 160 Ge. V/c longitudinal polarisation -76% intensity 2· 108 µ+/spill (4. 8 s/16. 2 s)

COMPASS • high energy beam • large angular acceptance • broad kinematical range two stage spectrometer Large Angle Spectrometer (SM 1), Small Angle Spectrometer (SM 2) 0. 003 < x < 0. 7 10 -3 < Q 2 < 102 (Ge. V/c)2

COMPASS • high energy beam Polarized Target: • large angular acceptance • broad kinematical 6 range 0. 003 < x < 0. 7 10 -3 < Q 2 < 102 (Ge. V/c)2 2002 -2004: Li. D (PT ≈ 50%, f = 0. 38) 2007: NH 3 (PT ≈ 90%, f = 0. 14) two stage spectrometer Large Angle Spectrometer (SM 1), Small Angle Spectrometer (SM 2) solid state targets Polarization reversal: once a week

Perspective of the talk SIDIS reactions in one photon exchange

Perspective of the talk SIDIS reactions in one photon exchange

Perspective of the talk SIDIS reactions in one photon exchange With different targets (p, d, n) and identification of the final hadron: flavour separation

The collinear case In the collinear QPM f 1(x) = q+(x) + q-(x) g 1(x) = q+(x) – q-(x) or integrated over k. T three quark distribution functions contribute in leading order f 1(x) g 1(x) Helicity h 1(x) = q. T (x) – q. T (x) Transversity

The collinear case In the collinear QPM f 1(x) = q+(x) + q-(x) g 1(x) = q+(x) – q-(x) g 1(x) Helicity or integrated over k. T three quark distribution functions contribute in leading order f 1(x) on M i s is 1 h 1(x) = q. T (x) – q. T (x) Transversity

Transversity Mission 1 3 approaches in SIDIS: • Azimuthal asymmetries in one hadron production (Collins effect) • Azimuthal asymmetries in hadron pair production (Interference fragmentation functions) • Transverse hyperon (L) polarization

Collins-Effect The Collins FF correlates the transverse spin of the fragmenting quark and the transverse momentum p. T of produced hadron h h p. T q q p. T h

Collins-Effect The Collins FF correlates the transverse spin of the fragmenting quark and the transverse momentum p. T of produced hadron h h p. T q q p. T h Measured asymmetry:

Deuteron Results: Collins Effect final results from 2002 -2004 data Physics Letters B 673 (2009) 127– 135 Deuteron target 2002 -2004

Collins asymmetry Full 2007 statistics PLB 692 (2010) 240 Proton target

Collins asymmetry Full 2007 statistics ± PLB 692 (2010) 240 Proton target K±

Collins asymmetry Full 2007 statistics Proton target

Transversity in 2 -Hadron Production

Transversity in 2 -Hadron Production

Transversity in 2 -Hadron Production

Transversity in 2 -Hadron Production Independent access to transversity !

Transversity in 2 -Hadron Production Deuteron target

Transversity in 2 -Hadron Production Full 2007 statistics Proton target Deuteron target

Transversity in 2 -Hadron Production Proton target Deuteron target

Introducing transverse momentum k. T

Introducing transverse momentum k. T Transversity

Introducing transverse momentum k. T on M i s is 2

Introducing transverse momentum k. T Sivers

Introducing transverse momentum k. T “pretzelosity”

Introducing transverse momentum k. T “worm-gear”

Cross section for transverse target spin A Bacchetta, M Diehl, K Goeke, A Metz, P Mulders, M Schlegel (06) NLO ……. (4 LO) Mission 2

Cross section for transverse target spin ……. NLO Sivers transversity A Bacchetta, M Diehl, K Goeke, A Metz, P Mulders, M Schlegel (06) (4 LO) pretzelosity worm-gear

Sivers Effect Distribution of unpolarized quarks with transverse momentum k. T in a transversely polarized nucleon The Sivers asymmetry:

Sivers asymmetries final results from 2002 -2004 data Deuteron Target PLB 673 (2009) 127

Sivers asymmetries Full 2007 statistics PLB 692 (2010) 240 Proton target

Sivers asymmetries Full 2007 statistics ± PLB 692 (2010) 240 Proton target K±

Sivers asymmetries ± Proton target K±

Target transverse spin results – (LO) Correlation of the parton transverse momentum and transverse polarization in a transversely polarized nucleon “Pretzelosity” Deuteron Target

Target transverse spin results – (LO) Correlation of the parton transverse momentum and transverse polarization in a transversely polarized nucleon “Pretzelosity” Full 2007 statistics Proton target

Target transverse spin results – (LO) Correlation of the parton transverse momentum and longitudinal polarization in a transversely polarized nucleon “worm-gear” Deuteron Target

Target transverse spin results – (LO) Correlation of the parton transverse momentum and longitudinal polarization in a transversely polarized nucleon “worm-gear” Full 2007 statistics Proton target

Summary Many recent results from COMPASS: Ø Transversity Ø Collins asymmetries for p± and K± for proton and deuteron targets → should be included in the global fit Ø Dihadron asymmetries for proton and deuteron targets → independent access to transversity Ø Sivers asymmetries for p± and K± for proton and deuteron targets → should be included in the global fit Ø Large azimuthal asymmetries of charged hadrons for unpolarized deuteron target → indication of non-vanishing Boer Mulders function

Outlook Short term:

Outlook Short term: Medium and long term: COMPASS II proposal accepted • Two years of DVCS measurements to attack GPDs • Two years of Drell-Yan measurements

Backup slides

Unpolarized Target Cross-Section Cahn effect, Boer-Mulders DF and p. QCD Measured using target-spin averaged samples

Cahn effect: Leading order QED, k. T 0

Cahn effect: Leading order QED, k. T 0 Boer Mulders effect: correlation of parton transv. Momentum and transv. polarization in an unpolarized nucleon

Cahn effect: Flavour independent Leading order QED, k. T 0 Boer Mulders effect: correlation of parton transv. Momentum and transv. polarization in an unpolarized nucleon Flavour dependent

Unpolarised Azimuthal Asymmetries cos modulation (Cahn + Boer-Mulders) Deuteron target Ø Large negative asymmetries Ø Charge dependent

Unpolarised Azimuthal Asymmetries cos 2 modulation (Cahn + Boer-Mulders) Deuteron target Ø Large positive asymmetries Ø Strongly charge dependent

Transversity from L Production

Transversity from L Production

Transversity from L Production

Transversity from L Production

Transversity from L Production

Lambda Selection and Polarization

Target transverse spin results – (NLO)