Transverse spin measurements in European SIDIS experiments Outline

Transverse spin measurements in European SIDIS experiments Outline: • A short Transverse spin/ TMD overview • The HERMES and COMPASS detectors • Transversity/Collins results • HERMESmany (proton) slides taken from Transversity/TMD • COMPASS (deuteron) workshop last week in Trento • A first successful global analysis to extract transversity (no new conventions, though) • Transversity/Interference FF • Sivers asymmetries Presented by an ex-hermesean • Other TMD measurements • Outlook BNL, July 21 th R. Seidl: Measurements of fragmentation functions at Belle: results and prospects

BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 2

BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 3

COMPASS • high energy beam • large angular acceptance • broad kinematical range beam: 160 Ge. V/c polarisation intensity - 76% (2002 -03) - 80% (2004) 2· 108 µ+/spill (4. 8 s/16. 2 s) two stages spectrometer Large Angle Spectrometer (SM 1), Small Angle Spectrometer (SM 2) Muon. Wall tracking, calorimetry, PID NEW TECHNOLOGIES SM 2 E/HCAL SM 1 Muon. Wall Polarised Target RICH m beam BNL, June 19 th Sci. Fi Silicon Micromegas GEMs R. Seidl: Trasnverse spin results from HERMES and COMPASS Straws SDC MWPC W 45 4

the COMPASS target system (2002 -2004) solid state target operated in frozen spin mode 3 He – 4 He Dilution refrigerator (T~50 m. K) superconductive Solenoid (2. 5 T) Dipole (0. 5 T) two 60 cm long cells with opposite polarization (systematics) d. N/dz 2000 BNL, June 19 th 2006: • PTM replaced with the large acceptance COMPASS magnet • 2 3 cells during data taking with transverse polarization • dipole field always • polarization reversal in the 2 cells after ~ 5 days 4000 0 2002 -2004: 6 Li. D dilution factor f = 0. 38 polarization PT = 50% ~20% of the time transversely polarized -1000 0 R. Seidl: Trasnverse spin results 1000 from zvtx (mm) HERMES and COMPASS 5

data taking with transversely polarized target 2002 -2004: 6 Li. D 2007: NH 3 SIDIS events (106) 11 days (19) BNL, June 19 th 9 days (14) R. Seidl: Trasnverse spin results from HERMES and COMPASS 14 days (24) 6

Quark distributions Sum of quarks with parallel and antiparallel polarization relative to proton spin (well known from Collider DIS experiments) q(x), G(x) Unpolarized distribution function q(x) Difference of quarks with parallel and antiparallel polarization relative to longitudinally polarized proton (known from fixed target (SI)DIS experiments) Dq(x), DG(x) Helicity distribution function Dq(x) Difference of quarks with parallel and antiparallel polarization relative to transversely polarized proton (first results from HERMES and COMPASS – with the help of Belle) dq(x) Transversity distribution function dq(x) BNL, June 19 th R. Seidl: Transverse Spin results from HERMES and COMPASS 7

Transversity properties: Three notations in use: dq(x), h 1(x), DTq(x) • • Helicity flip amplitude Chiral odd needs other chiral odd partner: – Transversity in DY – Collins fragmentation function – Interference fragmentation function – L Polarization • • • Since all interactions conserve chirality one needs another chiral odd object Does not couple to gluons adifferent QCD evolution than Dq(x) Valence dominateda Comparable to Lattice calculations, especially tensor charge BNL, June 19 th Positivity bound: Soffer bound: R. Seidl: Transverse Spin results from HERMES and COMPASS 8

Azimuthal asymmetries in SIDIS • Sivers and Collins effect are not distiguishable with longitudinally polarized target • Higher Twist effects are kinematically favored in longitudinal case • With transversely polarized target a 2 nd angle allows to distinguish effects U: unpolarized beam T: transversely polarized target BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 9

Collins measurements I • Large, positive p+ asymmetries: no surprise from u-quark dominance • Large, negative pasymmetries: first a surprise, now understood by large, negative disfavored Collins function • Contamination from decay of exclusive vector mesons BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 10

Collins measurements II • K+ asymmetries compatible with p+ asymmetries (through u quark dominance) • K- asymmetries maybe slightly positive BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 11

-ACollins measurements III PRL 94, 202002 (2005) and Nucl. Phys. B 765: 31 -70, 2007 • Smaller asymmetries than in • First fits to HERMES and proton case COMPASS data using assumptions on Transversity Hint of cancellation of show results consistent with transversity in isoscalar each other target BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 12

- Collins measurements IV - COMPASS preliminary 2003 -2004 data from deuteron for identified hadrons BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 13

Global Fit of HERMES, COMPASS and BELLE data BNL, June 19 th R. Seidl: Transverse Spin results from HERMES and COMPASS 14

First extraction of Collins functions and transversity distributions from fitting HERMES + COMPASS + BELLE data By Anselmino et al. , PRD 75 (07) BNL, June 19 th R. Seidl: Transverse Spin results from HERMES and COMPASS 15

Predictions for COMPASS data on a proton target from global fit BNL, June 19 th R. Seidl: Transverse Spin results from HERMES and COMPASS 16

Comparison with some models [1] Soffer et al. PRD 65 (02) [4] Wakamatsu, PLB 509 (01) [2] Korotkov et al. EPJC 18 (01) [5] Pasquini et al. , PRD 72 (05) [3] Schweitzer et al. , PRD 64 (01) [6] Anselmino et al. , PRD 75 (07) BNL, June 19 th R. Seidl: Transverse Spin results from HERMES and COMPASS 17

Transversity from di-hadrons – Interference fragmentation function • Second chiral-odd fragmentation function • Integrated over transverse momentum BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 18

BNL, June 19 th R. Seidl: Transverse Spin results from HERMES and COMPASS 19

di-hadron asymmetries identified hadrons on the deuteron target BNL, June 19 th p +p – K+ K– p + K– R. Seidl: Trasnverse spin results from HERMES and COMPASS 20

di-hadron asymmetries identified hadrons on the deuteron target BNL, June 19 th p +p – K+ K– p + K– R. Seidl: Trasnverse spin results from HERMES and COMPASS 21

L polarimetry S BNL, June 19 th x 10 all Q 2 R. Seidl: Trasnverse spin results from HERMES and COMPASS 22

L polarimetry systematic errors not larger than statistical errors RICH ID not used yet; some other improvement in selection still foreseen BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 23

8 leading-twist spin-k┴ dependent (TMD) distribution functions f 1(x) h 1(x) Sivers function g 1(x) Courtesy of Aram Kotzinian BNL, June 19 th Boer-Mulders R. Seidl: Transversefunction Spin results from HERMES and COMPASS 24

Sivers function Boer-Mulders function BNL, June 19 th R. Seidl: Transverse Spin results from HERMES and COMPASS 25

Sivers function measurements I p+ asymmetries clearly positive • First evidence of a nonzero TMD • p- K- asymmetries consistent with zero • K+ asymmetries 2. 3 times larger than p+ hard to explain • Consistent sign of Sivers functions as from M. Burkhardt’s chromodynamic lensing • BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 26

Sivers function measurements II • Results for all 3 pion states consistent with isospin symmetry BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 27

Sivers asymmetry III deuteron target transversely polarised charged hadrons (mostly pions) • 2004: results from 2002 data PRL 94(2005)202002 confirmed by • 2006: results from 2002 -2004 data NPB 765(2007)31 asymmetries compatible with zero within the statistical errors (systematic errors much smaller) BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 28

Sivers measurements IV • Again, 2003 -2004 data for identified hadrons BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 29

Sivers global analysis • • Simultaneous fit of HERMES (02 -04) and COMPASS (03 -04) data on identified hadrons u and d Sivers functions of nearly equal size and opposite sign Anselmino et al Collins et al Vogelsang, Yuan Also available: Efremov, Goeke, Schweitzer BNL, June 19 th R. Seidl: Transverse Spin results from HERMES and COMPASS 30

Other TMDs accessible in SIDIS (leading twist – many more at subleading twist) • 2 unpolarized functions (Cahn effect and Boer Mulders function) – Boer Mulders function interesting, models see same sign for u and d, quark spin-orbit correlation • • 2 with longitudinally polarized target (g 1 missing from table) 4 with transversely polarized target BNL, June 19 th R. Seidl: Transverse Spin results from HERMES and COMPASS 31

1 -D fitting procedure (MINUIT with c 2 minimization method) 9 – XBj, 8 – z, 9 - Ph. T bins and 16 Φj bins. Fitting the “ratio product” quantities Newly extracted Collins & Sivers asymmetries gave the same result as published (NP B 765 (2007) 31) BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 32

Correlation Coefficients (+/- hadrons, x, z and PT) BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 33

Results for (2002 -2004 deuteron data, 1 D fit) BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 34

Results for (2002 -2004 deuteron data, 1 D fit) BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 35

Results for (2002 -2004 deuteron data, 1 D fit) BNL, June 19 th R. Seidl: Trasnverse spin results from HERMES and COMPASS 36

Summary and Outlook • Nonzero Collins asymmetries • Global Sivers for analysis p+ and p-sees large u and d Sivers measured at HERMES functions, on transversely sea and Gluons polarized seem small proton target • Efforts to extract further TMDs through • Nearly vanishing Collins distinct asymmetries azimuthalobtained dependencies from COMPASS on deuteron target • Global transversity analysis on HERMES, • HERMES has finished taking polarized data COMPASS and BELLE – data Unweighted asymmetries contain full data set – Confirms large, negative disfavored Collins moments function and other azimuthal – Analysis of weighted – Extracts first u and ddependencies Transversityongoing distribution • Interference FF results from HERMES and June 30 – End of HERMES running COMPASS • COMPASS is just starting to run with a transversely polarized proton (NH 3) target • L polarization result from COMPASS • Sivers data from HERMES (nonzero) and COMPASS (zero) BNL, June 19 th R. Seidl: Transverse Spin results from HERMES and COMPASS 37

COMPASS proton run 2007 solid state target operated in frozen spin mode 2007: NH 3 dilution factor f = 0. 14 polarization PT = 90% 2 3 cells Coupling hole Microwave power Beam line BNL, June 19 th Cavity 1 Cavity 2 Thermal screen R. Seidl: Transverse Spin results from HERMES and COMPASS Cavity 3 38