「COMPASSでの核子スピン構造の研究」 STUDY OF SPIN STRUCTURE OF NUCLEON IN COMPASS Takahiro Iwata Yamagata University on behalf of the COMPASS Collaboration KEK Nucleon Structure 2007, January 12, 2007

DG/G from high pT hadron pairs & open charm OUTLINE COMPASS apparatus Data taking history DG/G from high pT hadron pairs & open charm g1D, new COMPASS QCD fit, DG evaluation Transverse spin effects: single-hadron asymmetries two-hadron asymmetries L transverse polarization Upgrades in 2006 Prospects Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

COMPASS SETUP two stages spectrometer Large Angle Spectrometer (SM1) Small Angle Spectrometer (SM2) tracking, calorimetry, PID SciFi Silicon Micromegas GEMs Straws SDC MWPC W45 MuonWall SM2 E/HCAL E/HCAL SM1 Polarised Target MuonWall RICH m beam high energy beam (160 GeV) broad kinematical range large angular acceptance X(min.)~0.002 Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

solid target operated in frozen spin mode THE TARGET SYSTEM superconductive Solenoid (2.5 T) 3He – 4He Dilution refrigerator (T~50mK) Dipole (0.5 T) two 60 cm long cells with opposite polarization (systematics) solid target operated in frozen spin mode Target material: 6LiD dN/dz 2000 zvtx (mm) -1000 1000 4000 THE RICH DETECTOR 5 m 6 m 3 m C4F10 photon detectors threshold momenta pp = 2 GeV/c pK = 9 GeV/c pP =17 GeV/c Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

2002 160 GeV m beam & 6LiD Long./Transv. Pol. 2003 ditto (~ 80/20) DATA TAKING HISTORY 2002 - 2006 2002 160 GeV m beam & 6LiD Long./Transv. Pol. 2003 ditto (~ 80/20) 2004 ditto (~ 80/20) 2004 test run with hadron beam 2005 NO SPS beam (Several upgrades) 2006 160 GeV m beam & 6LiD Long. Pol. Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

DIRECT MEASUREMENT OF DG/G Photon Gluon Fusion: gg -> qq two ways to access DG/G q = u,d,s “HIGH pT HADRON PAIRS” 2 hadrons with high pT  Large statistics  physical background: „model” (MC) dependent, q = c “OPEN CHARM” charm production  less background, less MC dependent.  small statistics Leading order analysis in the moment.. Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

+ HIGH PT HADRON PAIRS measure extracted Monte Carlo(LO) SIGNAL BACKGROUND + Photon Gluon Fusion Resolved g Q2 < 1 (GeV/c)2 Leading Order DIS QCD compton Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

HIGH PT HADRON PAIRS : Q2>1 GeV2 pT1, pT2 > 0.7 GeV/c, ΣpT2 > 2.5 (GeV/c)2 0.1 < y < 0.9 small x : small A1d  LODIS and QCDC neglected LEPTO Monte Carlo low Q2 high Q2 2002-2003 data result: (prelim.) systematic error: false asymmetry mainly contributes Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

HIGH PT HADRON PAIRS : Q2<1 GeV2 Direct Resolved photon PGF QCDC neglect LO DIS neglect PYTHIA-Monte Carlo for low Q² Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

Resolved photon processes HIGH PT HADRON PAIRS : Q2<1 GeV2 Resolved photon processes photon PDFs : unknown point like: perturbative(calculable) VMD: non-pertarbative  extream scenarios M.Gluck et al., Eur.Phys.J. C20:272(2001) 2002-2004 data result: (prelim.) Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

DG/G FROM OPEN CHARM Photon Gluon Fusion: gg -> cc c c hard scale m2 = 4mc2 Theory understood c Kaon ID with RICH c Combinatorial background Limited statistics Challenging measurement. Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

DG/G FROM OPEN CHARM BR:68% BR:4% D* tagging with slow pion untagged D0Kp D0Kpp0 D0Kp Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

DG/G = - 0.57 ± 0.41 (stat) ± (syst ≤ stat) DG/G FROM OPEN CHARM from Neural Network (parameterization) trained with AROMA Monte Carlo (full kinematics) f : dilution factor ~0.4 Pb : beam polarization ~0.8 Pt : target polarization ~0.5 S/(S+B): determined from fit AROMA MC VS. Neural Network 2002 – 2004 data D0 + D* DG/G = - 0.57 ± 0.41 (stat) ± (syst ≤ stat) @ xg ~ 0.15, m2 ~ 13 GeV2 Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

DIRECT MEASUREMENTS OF DG/G ∫G(x) = 2. 5 GRSV2000 NLO fits to g1 m2 = 3 Gev2 ∫G(x) = 0.6 (GRSV stdr) ∫G(x) = 0.2 ΔG/G is small (xg ≈ 0.1) ∫DG>1　unlikely Consistent also with RHIC ALL (p0 channel) measurements Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

precise data at low x , 3~4 better than SMC COMPASS g1D (2002-2004) precise data at low x , 3~4 better than SMC NEGATIVE TREND NOT OBSERVED hep-ex/060938, CERN-PH-EP/2006-029 Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

QCD FIT OF WORLD DATA WITH COMPASS g1D Input data usual cut : Q2>1GeV2 MS-bar renormalization and factorization scheme in NLO SU(3) flavor symmetry Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

COMPASS g1D WITH NLO QCD FIT Two equally possible solutions: DG>0 and DG<0 Previous fits do not show the trend of the data at low x Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

RESULTS OF NLO QCD FIT solutions : DG > 0 DG < 0 ∫G(x)dx = +0.26 +0.04,-0.06 -0.31 +0.10,-0.14 ∫S(x)dx = +0.28 ± 0.01 +0.32 ± 0.01 @ Q2=3(GeV)2 Both give 0.2-0.3 for the absolute value of the gluon spin contribution (∫G(x)dx) Gluon spin contribution is not large Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

QCD FIT & DIRECT MEASUREMENTS ∫G(x) = 0.3 NLO fit to g1 Q2 = 3 Gev2 ∫G(x) = -0.3 COMPASS high PT, Q2<1(GeV)2 data : good agreement with DG>0 , but only 1.3s away from DG<0. Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

DG>0 is in better agreement to the direct measurement. DG/G SUMMARY DG/G (xg ≈ 0.1) is small from the direct measurement ( high Pt hadron pairs ,Q2<1GeV2) Global QCD fit to g1 data gives two solutions. DG>0 and DG<0 |DG| not large (0.2-0.3) DG>0 is in better agreement to the direct measurement. Large DG unlikely Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

TRANSVERSE SPIN EFFECTS Transversity PDF quark with spin parallel to the nucleon spin in a transversely polarized nucleon DTq(x) = q↑↑(x) - q↑↓(x) h1q(x), dq(x), dTq(x) from Collins asym. in SIDIS single hadron production and two hadron asym. , L transverse polarization TMD PDFs an intrinsic asymmetry in the parton transverse momentum distribution induced by the nucleon spin related to orbital angular momentum of quark Sivers PDF from Sivers asym. in SIDIS single hadron production Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

RUN WITH TRANSVERSE POL. TARGET transversely polarised deuteron target ~ 20% of the running time 2002 11 days of data taking, 2 periods 2003 9 days of data taking, 1 period 2004 14 days of data taking, Collins and Sivers asymmetries published results 2002 prel results 2002-2004 with RICH PID Two hadron asymmetries Λ polarimetry prel results 2002-2003 trigger (large x, Q2) DAQ, on line filter DIS events (106) Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

SINGLE HADRON ASYMMETRIES SIDIS cross-section for transv. PT Collins Sivers fS = azim. angle of initial quark spin fS’ = azim. angle of struck quark spin fS= p- fS’ （due to helicity conservation) fh = azim. angle of leading hadron initial quark spin (nucleon spin) struck quark spin Collins angle: Azim. angle of a hadron wrt the struck quark spin FC = fh - fS’ (= fh +fS- p) Sivers angle:Azim. angle of a hadron wrt the initial quark spin (=nucleon spin) FS= fh - fS Scattering plane quark direction hadron （Breit frame） Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

COLLINS & SIVERS ASYMMETRIES Collins Asymmetry ± refer to the opposite orientation of the transverse spin of the nucleon PT is the target polarisation; DNN is the transverse spin transfer coefficient initial  struck quark, given by QED Transvesity Collins fragmentation function Sivers Asymmetry Sivers PDF Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

EVENT SELECTION DIS events Q2 > 1 GeV2 W2 > 25 GeV2 0.1 < y < 0.9 hadrons pht > 0.1 GeV/c z > 0.2 (all h) z > 0.25 (leading h) Q2 = 2.4 (GeV/c)2 W = 9.4 GeV/c2 xBj  0.035 2002 data Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

COLLINS ASYMMETRIES FOR DEUTERON DIS2006 DIS2006 2002-2004 small errors (~1%) small asymmetries CERN-PH-EP/2006-036 cancellation between p and n (lh and ah) Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

COLLINS ASYMMETRY & GLOBAL FIT SIDIS(deuteron COMPASS/ proton HERMES) & Belle data Belle(e+e-  hh’X ) Anselmino et al., hep-ph/0701006v1 PRESENT PICTURE DT0D(fav.) ~ - DT0D(unfav) DTd not well constrained from the global fit RICH + AGS annual Users’ Meeting June 6, 2006, www.bnl.gov/rhic ags/users meetings/workshops/basp , and paper in preparation. Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

SIVERS ASYMMETRIES FOR DEUTERON DIS2006 DIS2006 2002-2004 small errors (~1%) small asymmetries CERN-PH-EP/2006-036 cancellation between p and n (lh and ah) Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

SIVERS ASYMMETRIES & MODELS model calculations　consistent with HERMES proton DATA to be compared with the COMPASS 2002-04 data preliminary COMPASS 2002-2004 preliminary COMPASS 2002-2004 Collins et al Vogelsang and Yuan preliminary COMPASS 2002-2004 PRESENT PICTURE RICH + AGS annual Users’ Meeting June 6, 2006, www.bnl.gov/rhic ags/users meetings/workshops/basp , and paper in preparation. Anselmino et al Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

p±, K± ASYMMETRIES 2003-2004 same DIS event selection and hadron definition as before plus PID based on RICH 3% protons 12% kaons 77% pions 5% no RICH information 100% hadrons after all cuts final sample positive all leading pions 5.3 M 3.4 M kaons 0.9 M 0.7 M negative all leading pions 4.2 M 2.8 M kaons 0.6 M 0.4 M Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

p±, K± Collins Asymmetries 2003-2004 again, difficult to see an effect … Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

p±, K± SIVERS ASYMMETRIES 2003-2004 Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

TWO HADRON ASYMMETRIES modulation of the number of events in fRS fS = angle of initial quark spin (=target spin) fS’ = angle of final (struck) quark spin fS= p - fS’ （due to helicity conservation) fR = angle of two-hadron plane fRS =fR –fS’ = fR +fS- p i f h l-l’ transversity : interference fragmentation function( presently unknown) initial quark spin quark direction Trento conventions see hep-ph/0407345 Breit frame Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

TWO HADRON ASYMMETRIES Event selection z1> 0.1 & z2>0.1　 xf1>0.1 & xf2>0.1 z=z1+z2<0.9 diffractive r production 2002-2004 6.1x106 combinations Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

TWO HADRON ASYMMETRIES DNN : transverse spin transfer coefficient initial  struck quark f : target dilution factor PT : target polarization; Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

TWO HADRON ASYMMETRIES z ordered pairs Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

L TRANSVERSE POLARIZATION Transversity PT : target polarization; f : target dilution factor D(y): transverse spin transfer coefficient initial  struck quark, given by QED Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

L TRANSVERSE POLARIZATION systematic errors not larger than statistical errors RICH ID not used yet Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

TRANSVERSE SPIN EFFECTS SUMMARY New deuteron data from COMPASS are available the measured asymmetries and polarizations are very small, compatible with zero Collins and Sivers asymmetries for positive and negative hadrons, p±, K± Two hadron asymmetries L transverse polarization PRESENT PICTURE Collins: DT0D(fav.) ~ - DT0D(unfav) DTd not well constrained Sivers: D0Tu ~ - D0Td Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

UPGRADES IN 2006 upgrade of polarized target New magnet Old SMC Magnet New magnet with a large aperture 60 cm 30 cm hadron acceptance increased Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

UPGRADES IN 2006 RICH upgrade field lenses ¼ of inner part concentrator 3 m 6 m MAPMT photon detectors 5 m ¼ of inner part C4F10 mass spectrum upgrade of RICH p K previous system upgraded RICH inner part : 576 MAPMTs with indiv. Telescope HAMAMATSU R7600-M16-03, 16 ch PID performance raised up Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

PROSPECTS 2007 Transverse polarization run with pol. proton target Hadron program with p/p beam + Liq.H2 target 2008/2009 longitudinal(+transverse) polarization run & hadron program 2010- DVCS measurements with muon beam & Liq.H2 target Polarized Drell-Yan measurements with p- beam & pol. target Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

Nucleon Structure Function 2007 @KEK, January 11-12 2007 BACKUP SLIDES Takahiro Iwata Nucleon Structure Function 2007 @KEK, January 11-12 2007

HERMES DG/G from single hadron P.Liebing (HERMES) SPIN2006, Kyoto RICH + AGS annual Users’ Meeting June 6, 2006, www.bnl.gov/rhic ags/users meetings/workshops/basp , and paper in preparation. Takahiro Iwata Nucleon Structure Function 2007 @KEK, January 11-12 2007

TRANSVERSE MOMENTUM DEPENDENT PDFs Nucleon unpol. long. pol. trans. pol. number density Sivers unpol. Nucleon Parton T-odd helicity long. pol. Quark transversity Boer-Mulders survive after integration over kT RICH + AGS annual Users’ Meeting June 6, 2006, www.bnl.gov/rhic ags/users meetings/workshops/basp , and paper in preparation. trans. pol. T-odd Takahiro Iwata Nucleon Structure Function 2007 @KEK, January 11-12 2007

SINGLE HADRON ASYMMETRIES unpol B and T transvely polarised target SIDIS cross-section long pol B and/or T h azimuthal angle of the hadron s’ azimuthal angle of the transverse spin of the struck quark s azimuthal angle of the transverse spin of the initial quark s’ = p - s FS at leading order Collins Sivers beam polarization independent angles  independent extraction of the asymmetries Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata

increase in statistics by a factor of 7! ASYMMETRIES 2003-2004 vs 2002 2003-2004 data released in April 2006 (DIS2006) comparison with the published 2002 data PRL 94 (2005) 202002 increase in statistics by a factor of 7! Nucleon Structure Function 2007 @KEK, January 11-12 2007 Takahiro Iwata