RECENT COMPASS RESULTS ON TRANSVERSE PHYSICS Takahiro Iwata

RECENT COMPASS RESULTS ON TRANSVERSE PHYSICS Takahiro Iwata Yamagata University on behalf of the COMPASS Collaboration COMPASS presentations L-Spin : Celso Franco Future plans: Norihiro Doshita Circum-Pan-Pacific Symposium on High Energy Spin Physics, Cairns, Australia, June 20 -24 , 2011

OUTLINE § Introduction to COMPASS § The experimental setup § Data taking history § Transverse spin and TMD effects § Asymmetries with a polarized proton target § Azimuthal asymmetries in unpolarized SIDIS § Summary Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

ＣＯＭＰＡＳＳ ａｔ CERN Lake LEMAN Nucleon Structure LH C Hadron Spectroscopy COMPASS Airport SPS (p: 450 Ge. V) N CERN (France) CERN (Suisse) 17/06/2021 Takahiro Iwata BEACH 08 26 june 2008 3 Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

THE SPECTROMETER two stage spectrometer • Large Angle Spectrometer (SM 1) • Small Angle Spectrometer (SM 2) tracking, calorimetry, PID Sci. Fi Silicon Micromegas GEMs Straws SDC MWPC W 45 E/HCAL Configuration in Muon program Muon. Wall SM 2 E/HCAL SM 1 Muon. Wall Polarised Target Pol. m beam 160 Ge. V, pol. 80% Takahiro Iwata 0. 003 < x < 0. 5 10 -3 < Q 2 < 10 Ge. V 2 RICH • high energy beam • broad kinematical range • large angular acceptance Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

THE POLARIZED TARGET SYSTEM Solid polarized target operated in Dynamic Nuclear Polarization technique with a dilution refrigerator PT magnet: +180~-180 mrad geometrical acceptance To match larger acceptance: 3 target cells: reduction of false asymmetries Upstream Takahiro Iwata Middle Downstream Target: NH 3 for proton , 6 Li. D for deuteron longitudinal & transverse mode available very long relaxation time (∼ 4000 h) magnetic field rotation without polarization loss Polarization of NH 3 -92%, +88%, -83% Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

THE RICH DETECTOR 3 m 6 m 5 m photon detectors C 4 F 10 • radiator gas: C 4 F 10 • mirror wall: 20 m 2 surface • photon-detectors: • outer part (75%) MWPC(pad RO) with Cs. I cathode • inner part(25%) 576 MAPMTs with indiv. telescope threshold momenta ● p = 2 Ge. V/c ● p = 9 Ge. V/c K ● p =17 Ge. V/c P Takahiro Iwata Installed in 2005, Used in data taking from 2006 Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

DATA TAKING HISTORY 2002 - 2011 § 2002 Data taking started muon program with 160 Ge. V polarized muon • 2002 -2006 6 Li. D polarized target ( pol. deuterons) L-mode: 80 / T-mode: 20 , DG/G measurement 2005 no data taking • 2007 NH 3 polarized target (pol. protons) L-mode: 50 /T-mode: 50 • 2008, 2009 hadron program with hadron beam at 190 Ge. V • 2010 NH 3 polarized target (pol. protons) only T-mode • 2011 Takahiro Iwata ditto only L-mode Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

Transverse Spin and TMD Effects Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

TRANSVERSE SPIN &TMD EFFECTS IN COMPASS Transversity PDF quark with spin parallel to the nucleon spin in a transversely polarized nucleon DTq(x) = q↑↑(x) - q↑↓(x) from Collins asym. in SIDIS single hadron production, two-hadron asym. , transverse L polarization, … TMD effects angular distributions caused by the parton’s transverse momentum related to orbital angular momentum of quark from Sivers asym. in SIDIS, azimuthal distribution of hadrons in unpolarized SIDIS Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

Transverse Spin Effects Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

SINGLE HADRON ASYMMETRIES IN SIDIS cross-section for transv. PT Collins Sivers Collins angle: Azim. angle of a hadron wrt struck quark spin FC = h - S’ (= h + S- p) Sivers angle: Azim. angle of a hadron wrt nucleon spin FS= h - S nucleon spin (initial quark spin) struck quark spin Scattering plane S = azim. angle of nucleon spin (initial quark spin) S’ = azim. angle of struck quark spin S= p- S’ （due to helicity conservation) h = azim. angle of leading hadron Takahiro Iwata hadron quark direction （Breit frame） Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

COLLINS ASYMMETRY Collins Asymmetry Modulation wrt the Collins angle ± : opposite orientation of the transverse spin of the nucleon PT is the target polarization; DNN is the transverse spin transfer coefficient initial struck quark, given by QED Transvesity Collins fragmentation function Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

COLLINS ASYMMETRIES proton h+ h− PLB 692 (2010), 240 deuteron h+ h− PLB 673 (2009), 127 ・ large asymmetry for proton : about 10% , for both h + and h- ・ deuteron result opposite sign of DTu and DTd Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

NEW RESULTS FOR & K proton +- large asymmetry for proton K+- Takahiro Iwata But, not clear for K Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

COMPASS-HERMES COMPARISON in good agreement proton - + COMPASS HERMES for charged pions Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

TRANSVERSITY GLOBAL FITS • Fitting to AColld from COMPASS, ACollp from HERMES and Collins F. F. from BELLE (e+e- scattering) predictions • good agreement with the new proton data of COMPASS ・ DTu and DTd have opposite sign as expected from deuteron data COMPASS proton 2007 Transvesity u d Anselmino et al. Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

TWO-HADRON ASYMMETRY Two hadrons produced in SIDIS Modulation wrt the angle between two-hadron plane and struck quark spin Two-hadron asymmetry f : target dilution facto PT : target polarization DNN : transverse spin transfer coefficient initial struck quark f i h l-l’ S = angle of nucleon spin (=initial quark spin) S’ = angle of final (struck) quark spin S= p - S’ （due to helicity conservation) R = angle of two-hadron plane RS = R – S’ = R + S- p Takahiro Iwata nucleon spin (=initial quark spin) quark direction Trento conventions see hep-ph/0407345 Breit frame Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

TWO-HADRON ASYM. FOR PROTON transversity Interference fragmentation function ( not well known ) Proton Ks + + - r + + - Clear effect observed Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

COMPASS-HERMES COMPARISON in good agreement with the HERMES results Proton HERMES values scaled with 1/Dnn Global fit possible when interference fragmentation function measured (BELLE) Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

TRANSVERSE L POLARIZATION Transversity can be studied through transverse L polarization Transversity Polarized fragmentation function to L PT : target polarization; f : target dilution factor D(y): transverse spin transfer coefficient initial struck quark, given by QED Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

TRANSVERSE L POLARIZATION L and L-bar on transversely polarized proton target two hadron events with the 2 nd. vertex (v 0) e, , K rejection from p-track candidates by RICH Armenteros-Podolanski plot ( for V 0 , after RICH selection) After RICH selection Polarization measured via parity violating decay Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

L POLARIZATION ON PROTON TARGET The measured polarizations are compatible with zero small DTDL/q Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

TMD Effects Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

SIVERS EFFECT IN SIDIS Modulation wrt Sivers angle ± refer to the opposite orientation of the transverse spin of the nucleon Sivers angle: Azim. angle of a hadron wrt the nucleon spin FS= h – S nucleon spin struck quark spin Sivers PDF Scattering plane correlation between transverse momentum of the quark and the transverse polarization of the nucleon Takahiro Iwata hadron quark direction （Breit frame） Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

SIVERS ASYMMETRIES h+ h− COMPASS proton 2007 Proton slightly positive for h+ PLB 692 (2010), 240 Deuteron compatible with zero PLB 673 (2009), 127 Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

SIVERS ASYMMETRIES FOR & K Proton HERMES data show clear signals for + & K+ + - Proton K+ Takahiro Iwata K- No definite conclusion with the COMPASS data due to limited statistics More statistics with 2010 COMPASS data Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

COMPARISON IN DETAIL COMPASS results smaller by a factor ~2 COMPASS h+ PLB 692(2010)240 -246 HERMES + COMPASS proton 2007 PRL 103(2009)152002 h+ Possible explanation kinematical regions are different between COMASS and HERMES Inv. mass of the hadronic final state lower energy region probed in HERMES Takahiro Iwata possible W dependence ? Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

Asymmeties for unpol. target Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

AZIMUTHAL ASYMMETRIES FOR UNPOL. TARGET TMD effects in SIDIS for unpolarized targets h : azumuthal angle of hadron from scatt. plane cos h and cos 2 h modulations affected by Cahn effect Takahiro Iwata & Boer-Mulders Effect Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

CAHN EFFECT kinematical effect by transverse momentum of quark elementary cross-section: elementary Mandelstam variables: Taking account of transverse momentum of quark k: initial quark momentum k. T: initial quark transverse momentum k’ : final quark momentum Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

BOER-MULDERS EFFECT Boer-Mulders function Correlation between quark transverse momentum and quark spin in unpolarized nucleon Contributes to cos h and cos 2 h moments with convoluted Collins function Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

COS h MODULATION COMPASS 2004 6 Li. D h+ Preliminary COMPASS 2004 6 Li. D h- large negative signals over all the x range strong dependence on z, PTh different for h+ & h- Preliminary ( T- mode samples) Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

COS 2 h MODULATION COMPASS 2004 6 Li. D large signals at small-x h+ Preliminary COMPASS 2004 6 Li. D strong dependence on z, x, PTh different for h+ & h- h. Preliminary ( T- mode samples) Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

SUMMARY • COMPASS is a major player in the nucleon spin physics • Transverse Spin and TMD Effects have been intensively studied • Collins and Sivers asymmetries for and K on a transversely polarized proton and a deuteron target • two-hadron asymmetries • small transverse Λ polarization , compatible with zero • large azimuthal asymmetries of hadrons produced on an unpolarized deuteron target Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

BACKUP SLIDES Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

SIVERS ASYMMETRY FOR PROTON Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

SIVERS PDF GLOBAL FIT Global fit using Ad. Siv( ±) and Ad. Siv(K±) from COMPASS and Ap. Siv( ±) and Ap. Siv(K±) from HERMES: Takahiro Iwata M. Boglione in collaboration with M. Anselmino, U. D’Alesio, A. Kotzinian, S. Melis, F. Murgia, A. Prokudin, Circum-Pan-Pacific Symposium, Cairns, Australia, C. June 20 -24 , 2011 Turk

SIVERS ASYM. DATA V. S. PREDICTION comparison with recent M. Anselmino et al. predictions ar. Xiv: 0805. 2677 HERMES proton data COMPASS deuteron data marginal agreement with COMPASS proton data Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

TWO-HADRON ASYMMETRY - Deuteron Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011

TRANSVERSE MOMENTUM DEPENDENT PDFs unpol. Nucleon long. pol. unpol. number density Nucleon Parton trans. pol. Sivers T-odd Quark long. pol. helicity trans. pol. Boer. Mulders transversity survive after integration over k. T T-odd Takahiro Iwata Circum-Pan-Pacific Symposium, Cairns, Australia, June 20 -24 , 2011