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TMD experiments from COMPASS SIDIS

This presentation discusses the TMD experiments conducted by the COMPASS collaboration at CERN. Topics include nucleon PDFs, Collins asymmetry, di-hadron asymmetry, Sivers asymmetry, and more.

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TMD experiments from COMPASS SIDIS

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  1. TMD experiments from COMPASS SIDIS Takahiro Iwata, (Yamagata University) on behalf of COMPASS Collaboration Hadron China 2017, 24-28, 2017, Nanjing

  2. OUTLINE • Introduction • COMPASS setup for DIS & SIDIS • Nucleon PDFs • Collins asymmetry • Collins Asymmetry for single-hadron production • Di-hadron Asymmetry • Sivers asymmetry • Sivers Asymmetry for single-hadron production • Weighted Sivers asymmetry • Gluon Sivers asymmetry • Conclusion Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  3. COMPASS at CERN DIS & SI-DIS setup with muon & PT Straws SDC MWPC W45 SciFi Silicon Micromegas GEMs MuonWall Polarised Target (NH3 for p, 6LiD for d) E/HCAL E/HCAL SM2 SM1 MuonWall Pol. • beam fom SPS 160-200 GeV, pol. = 80% RICH two stage spectrometer tracking, calorimetry, PID Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  4. The Polarized Target System DNP technique with a dilution refrigerator (Tmin.=30mK) , a 2.5T superconducting magnet and microwave (70GHz) system • 2/3 target sections (60+60 cm/30+60+30 cm) • longitudinal & transverse pol. modes The world biggest PT beam 2002 - 2004 NH3 6LiD  Polarization of proton(NH3 ) ~90% Polarization of deuteron( 6LiD) ~50% 2006 - 2011 6LiD NH3 • 6Li (~ a+d) also polarized •  dilution factor f=50% Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  5. The Polarized Target System DNP technique with a dilution refrigerator (Tmin.=30mK) , a 2.5T superconducting magnet and microwave (70GHz) system • 2/3 target sections (60+60 cm/30+60+30 cm) • longitudinal & transverse pol. modes The world biggest PT beam NH3 2002 - 2004 6LiD  Polarization of proton(NH3 ) ~90% Polarization of deuteron( 6LiD) ~50% 2006 - 2011 6LiD NH3 • 6Li (~ a+d) also polarized •  dilution factor f=50% Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  6. At LO, taking account of transverse momentum(kT) of the quarks Nucleon PDFs Nucleon unpol. long. pol. trans. pol. number density Sivers unpol. Nucleon T-odd Parton worm-gear-1 helicity long. pol. Quark transversity Boer-Mulders pretzelosity trans. pol. worm-gear-2 T-odd Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  7. Sivers & BM-functions Nucleon unpol. long. pol. trans. pol. Sivers Sivers- and BM-functions are relateted to quark OAM and expected to be process dependent unpol. T-odd long. pol. Quark DY SIDIS Boer-Mulders trans. pol. T-odd Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  8. SIDIS x-section for single hadron production S: nucleon covariant spin vector l:lepton helicity Sivers s: nucleon spin (initial quark spin) s’: struck quark spin Collins Transverse Target Spin Asymmetries Scattering plane quark direction hadron （Breit frame） 15 asymmetries: 2-”UU”,1-”LU”,2-”UL”, 2-”LL”,5-”UT”, 3-”LT” All measured in COMPASS for p & d Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  9. Collins & Sivers asymmetries Transversity Collins F.F. (polarized quark fragmentation) can be used for quark polarimeter Collins mechanism unpol. F.F. Sivers PDF Sivers effect Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  10. Collins Asymmetry on Proton Event Selection Q2>1 (GeV/c)2 W>5 GeV/c2 0.05 < y < 0.9 z > 0.1 |PhT| > 0.07 GeV/c p- Clearly non-zero in valence region, negative for p+ , positive for p- - p+ K- Similar trend for K, negative for K+ , positive for K-- K+ K0->p+p- K0 Deuteron target asymmetries compatible with zero (COMPASS PLB673 (2009) 127 ) PLB 744 (2015) 250 z=Eh/n Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  11. Collins Asymmetry compared with a Fit Transversity u p+ The fit reproduces the COMPASS data well d p- Collins F.F. up+ favoured up- global fit by Anselmino group with HERMES, COMPASS, Belle data [PRD87(2013) 094019] dis-favoured Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  12. Di-hadron Asymmetry & Transversity Transversity PDF “Di-hadron FF” Modulation according to fR: azimuthal angle of R (Relative hadron momentum vector) fS’: azimuthal angle of struck quark spin fS: azimuthal angle of initial quark spin Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  13. Di-hadron Asymmetry on Proton Event Selection Q2>1 (GeV/c)2 W>5 GeV/c2 0.1 < y < 0.9 z > 0.1 |RT| > 0.07 GeV/c COMPASS 2007/2010 proton r0 Npair=3.5x107 after the cuts Clearly negative in the valence region pion mass is assumed Phys. Lett. B736 (2014) 124 Deuteron data also published PLB713 (2012) 10 The asymmetry is compatible with zero ! Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  14. Interplay; Di-hadron & Collins Asymmetries [1] Mirror symmetry between Collins h+ and h- [2] Di-hadron asymmetry similar to the Collins h+  Hint of common physical origin between Di-hadron FF and Collins mechanism Further study on the Collins asymmetries for the di-hadron events gave indication that they are driven by the common origin PLB 736 (2014) 124 COMPASS PLB 753 (2016) 406 : positive : negative y S’ h- R h+ x Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  15. Sivers Asymmetry on Proton Event Selection Q2>1 (GeV/c)2 W>5 GeV/c2 0.05 < y < 0.9 z > 0.1 |PhT| > 0.07 GeV/c p+ Significantly large signal for p+ and K+ p- Compatible with zero for p- , K - and K0 K+ K0->p+p- K- PLB 744 (2015) 250 K0 Deuteron target asymmetries compatible with zero (COMPASS PLB673 (2009) 127 ) Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  16. Sivers Asymmetry on Proton; p+ & K+ K+ K+ signal is even larger than that of p+ • possible contribution from sea quarks p+ Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  17. Sivers Asymmetry compared with Global Fits The fits reproduce the COMPASS data reasonabley well. p+ p- COMPASS results for unidentified hadrons on proton is included in the global fits Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  18. Extracted Sivers function by global fits G.Miguel et al., Phys. Rev. D 89, 074013 (2014) Anselmino et al., Eur.Phys.J.A39:89-100,2009 Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  19. Q2 dependence of Sivers Asymmetries COMPASS has measured the TSA in different Q2 ranges in SIDIS SIDIS Drell-Yan high mass DY Sivers PBL 770 (2017)138 h+ : The data are positive in all the Q2-ranges. h- : The lowest Q2 data are compatible with 0 and data become significantly positive in the other ranges. Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  20. Multi Dimensional Sivers Asymmetries Sivers PBL 770 (2017)138 h+ : A>0 in whole Q2, increasing as x, z & Pt. h- : less and not prominent Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  21. Other TSAs in different Q2 ranges transverse target spin Asymmetries PLB 770 (2017) 138 Sivers Collins beam spin & target spin Asymmetries Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  22. PTh Weighted Sivers Asymmetry “standard” Sivers Asymmetry: LO QCD parton model usually solved using Gaussian model for PDF and FFs : convolution over transverse momenta g* N CM system simple product Model dependent ! Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  23. PTh Weighted Sivers Asymmetry If you weight with “PTh weighted ” Sivers Asymmetry: proposed by convolution  simple product of Sivers(first moment) and FF first moment of Sivers PDF model independent way ( no assumption on the shape of PDFs and FFs) Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  24. PTh Weighted Sivers Asymmetry Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  25. Gluon Sivers Asymmetry Sivers effect for also gluons? Gluon OAM ? Recent review  D. Boer et al., Adv. High Energy Phys., 2015, 371396 (2015). It can be studied with the asymmetry for photon-gluon-fusion To enhance the PGF, 2-hadrons with high Pt are detected. hadron The azimuthal angle of the hadron pair, f2h, is strongly correlated with the gluon azimuthal angle fg hadron Data sample : 2010 proton target, 2003,4 deuteron target Event selection : Without charge constraint for the hadron pair Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  26. Gluon Sivers Asymmetry However, one has to take account of the background processes; + BG signal MC The asymmetry can be decomposed as: With a help of MC simulation, the process fractions(Ri) are evaluated. The MC simulation : • Generator LEPTO + GEANT + Reconstruction program • PDF: MSTW2008 • Parton shower: on • FLUKA for secondary interactions • Special generator tuning for high-Pt events Fitting the data with Neural Network trained by the MC, each asymmetry is determined. Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  27. Gluon Sivers Asymmetry : Results proton & deuteron combined Two standard deviation from zero  Gluon Sivers effect ? Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  28. Conclusions • SIDIS gave and is giving fundamental contribution to the study of the transverse spin structure of the nucleon. • COMPASS has provided TSA data for proton and deuteron. • The Collins asymmetries and Sivers Asymmetries were found to be different from zero for proton although they are consistent with zero for deuteron. • There is an interplay between the single hadron Collins asymmetries and di-hadron asymmetries suggesting common origin in production mechanism. • The Sivers asymmetries were obtained in different Q2 ranges. One of the ranges corresponds to the di-muon mass range where the Drell-Yan measurement of COMPASS was performed. • The Sivers asymmetry for PGF was found to be negative with two standard deviation from zero suggesting the possible gluon Sivers effect. Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  29. Spares Hadron China 2017, 24-28, 2017, Nanjing

  30. Comparison with calculations In good agreement with the calculations in low-z & low Pt ranges. Calculations are based on fits of one-dimensional data ( PRD72(2005)094007 [Erratum:PRD 72 099903(2005)], EPJ A39 (2009)89) PBL 770 (2017)138 However, in high-z & high-Pt ranges, clear discrepancies are seen. PBL 770 (2017)138 Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  31. Expected property for the Sivers PDF Sivers function is process dependent. sign change ! SIDIS : with final state interaction (FSI) Drell-Yan: with initial state interaction (ISI) repulsive attractive ejected (red) quark is attracted by the anti-red spectators before annihilating with the red active quark, the approaching anti-quark(anti-red) is repelled by the anti-red spectators This is to be checked in the common kinematical region in COMPASS experimentally. Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  32. SIDIS Kinematics Fragmentation Function Energy fraction of the hadron Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

  33. Gluon Sivers Asymmetry : Results Asymmetries for PGF Asymmetries for BG Takahiro IWATA, Hadron China 2017, 24-28, 2017, Nanjing

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