TMD experiments from COMPASS SIDIS Takairo Iwata, (Yamagata University) on bealf of COMPASS Collaboration
OUTLINE Introduction COMPASS setup for DIS & SIDIS Nucleon PDFs Collins asymmetry Collins Asymmetry for single-adron production Di-adron Asymmetry Sivers asymmetry Sivers Asymmetry for single-adron production Weigted Sivers asymmetry Gluon Sivers asymmetry Conclusion
COMPASS at CERN DIS & SI-DIS setup wit muon & PT SciFi Silicon Micromegas GEMs MuonWall Straws SDC MWPC W45 Polarised Target (NH 3 for p, 6 LiD for d) E/HCAL SM1 SM E/HCAL MuonWall Pol. beam fom SPS 160-00 GeV, pol. = 80% RICH two stage spectrometer tracking, calorimetry, PID Hadron Cina 017, 4-8, 017,
Te Polarized Target System DNP tecnique wit a dilution refrigerator (T min.=30mk), a.5t superconducting magnet and microwave (70GHz) system /3 target sections (60+60 cm/30+60+30 cm) longitudinal & transverse pol. modes beam 00-004 NH 3 6 LiD Polarization of proton(nh 3 ) ~90% 006-011 Polarization of deuteron( 6 LiD) ~50% NH 3 6 LiD 6 Li (~ a+d) also polarized dilution factor f=50% Hadron Cina 017, 4-8, 017,
Te Polarized Target System DNP tecnique wit a dilution refrigerator (T min.=30mk), a.5t superconducting magnet and microwave (70GHz) system /3 target sections (60+60 cm/30+60+30 cm) longitudinal & transverse pol. modes beam 00-004 NH 3 6 LiD Polarization of proton(nh 3 ) ~90% 006-011 Polarization of deuteron( 6 LiD) ~50% NH 3 6 LiD 6 Li (~ a+d) also polarized dilution factor f=50% Hadron Cina 017, 4-8, 017,
Nucleon PDFs At LO, taking account of transverse momentum(k T ) of te quarks Quark unpol. long. pol. trans. pol. q( f ) 1 1 T-odd number density Nucleon Parton Nucleon unpol. long. pol. trans. pol. k T Boer- Mulders q g1 L 1L ( ) k T elicity worm-gear- f 1T T-odd g 1T T q 1T k T ( ) kt k T Sivers worm-gear-1 1 transversity pretzelosity 6
Sivers & BM-functions Quark unpol. long. pol. trans. pol. 1 T-odd Nucleon unpol. long. pol. trans. pol. Sivers- and BM-functions are relateted to quark OAM and expected to be process dependent k T Boer- Mulders SIDIS ( x, k ) ( x, k ) 1 SIDIS 1 f 1T T-odd k T Sivers f ( x, k ) f ( x, k ) q q 1T SIDIS 1T DY DY DY 7
SIDIS x-section for single adron production S: nucleon covariant spin vector l:lepton elicity Sivers Collins sin sin S S A UT sin S s sin C C A UT C s s s : struck quark spin s: nucleon spin (initial quark spin) Transverse Target Spin Asymmetries Scattering plane quark direction adron (Breit frame) 15 asymmetries: - UU,1- LU,- UL, - LL,5- UT, 3- LT All measured in COMPASS for p & d 8
Collins & Sivers asymmetries A Coll q e q q e q T Transversity Collins F.F. (polarized quark fragmentation) q H q D q q 1 can be used for quark polarimeter Collins mecanism Sivers PDF unpol. F.F. A Siv q e f D q q 1 T, q q e q q D q Sivers effect 9
Collins Asymmetry on Proton - Event Selection Q >1 (GeV/c) W>5 GeV/c 0.05 < y < 0.9 z > 0.1 P T > 0.07 GeV/c + K - Clearly non-zero in valence region, negative for +, positive for - - Similar trend for K, negative for K +, positive for K -- K + K 0 K 0 > z=e /n PLB 744 (015) 50 Deuteron target asymmetries compatible wit zero (COMPASS PLB673 (009) 17 ) 10
Collins Asymmetry compared wit a Fit Transversity u + - Te fit reproduces te COMPASS data well Collins F.F. d u + favoured global fit by Anselmino group wit HERMES, COMPASS, Belle data [PRD87(013) 094019] dis-favoured u - 11
A Di-adron Asymmetry & Transversity ln l X e q H sin q T q RS q UT q e q q fq Tq Dq Transversity PDF Di-adron FF Modulation according to RS R S R S R : azimutal angle of R (Relative adron momentum vector) S : azimutal angle of struck quark spin S : azimutal angle of initial quark spin 1
Di-adron Asymmetry on Proton COMPASS 007/010 proton Npair=3.5x10 7 after te cuts Clearly negative in te valence region Event Selection Q >1 (GeV/c) W>5 GeV/c 0.1 < y < 0.9 z > 0.1 R T > 0.07 GeV/c r 0 pion mass is assumed Pys. Lett. B736 (014) 14 Deuteron data also publised PLB 713 (01) 10 Te asymmetry is compatible wit zero! 13
Interplay; Di-adron & Collins Asymmetries [1] Mirror symmetry between Collins + and - [] Di-adron asymmetry similar to te Collins + Hint of common pysical origin between Di-adron FF and Collins mecanism PLB 736 (014) 14 Furter study on te Collins asymmetries for te di-adron events gave indication tat tey are driven by te common origin COMPASS PLB 753 (016) 406 y S : positive : negative 1 - R + x 14
Sivers Asymmetry on Proton + K + - Event Selection Q >1 (GeV/c) W>5 GeV/c 0.05 < y < 0.9 z > 0.1 P T > 0.07 GeV/c Significantly large signal for + and K + Compatible wit zero for, K - and K 0 K - K 0 > K 0 PLB 744 (015) 50 Deuteron target asymmetries compatible wit zero (COMPASS PLB673 (009) 17 ) 15
Sivers Asymmetry on Proton; + & K + K + K + signal is even larger tan tat of + + possible contribution from sea quarks 16
Sivers Asymmetry compared wit Global Fits + Te fits reproduce te COMPASS data reasonabley well. - COMPASS results for unidentified adrons on proton is included in te global fits 17
Extracted Sivers function by global fits G.Miguel et al., Pys. Rev. D 89, 074013 (014) Anselmino et al., Eur.Pys.J.A39:89-100,009 18
Q dependence of Sivers Asymmetries COMPASS as measured te TSA in different Q ranges in SIDIS Drell-Yan SIDIS ig mass DY Sivers PBL 770 (017)138 + : Te data are positive in all te Q -ranges. - : Te lowest Q data are compatible wit 0 and data become significantly positive in te oter ranges. 19
Multi Dimensional Sivers Asymmetries Sivers PBL 770 (017)138 + : A>0 in wole Q, increasing as x, z & Pt. - : less and not prominent 0
Oter TSAs in different Q ranges transverse target spin Asymmetries PLB 770 (017) 138 Sivers Collins beam spin & target spin Asymmetries 1
P T Weigted Sivers Asymmetry standard Sivers Asymmetry: LO QCD parton model A e f D q 1 T, q 1, q quarks Siv. q 1, q 1, q quarks e f ( x) D ( z) : convolution over transverse momenta kt PT 1 T, q 1, q T T ( T T ) 1T 1 MPT PT p zk T f D d P d k d p zk p P f D g* N CM system k p PT A N ( ) N 1S A sin 0 Siv. T Siv. Siv. Siv. S usually solved using Gaussian model for PDF and FFs 1 f ( x, k, Q ) f ( x, Q ) e 1T T 1T kt 1 D (z, p, Q ) D (z, Q ) e 1 1 p simple product q (1) 1 Tq, 1, q quarks Siv. ag eq f1, q x D1, q quarks e f D ( ) ( z) a G S p k k T S T / kt S / p M p z Model dependent!
P T Weigted Sivers Asymmetry P T weigted Sivers Asymmetry: proposed by If you weigt wit w P T Mz N ( ) N 1 S A sin, W 0, W W Siv. T Siv. Siv. convolution simple product of Sivers(first moment) and FF A e f ( x) D ( z) q (1) 1 T, q 1, q w (1) quarks Siv. ASiv. q 1, q 1, q quarks e f ( x) D ( z) first moment of Sivers PDF (1) kt f1 T ( x) d kt f 1T ( x, kt ) M model independent way ( no assumption on te sape of PDFs and FFs) 3
P T Weigted Sivers Asymmetry A e f ( x) D ( z) q (1) 1 T, q 1, q w (1) quarks Siv. ASiv. q 1, q 1, q quarks A e f ( x) D ( z) e f D q (1) 1 T, q 1, q quarks Siv. ag q 1, q 1, q quarks e f ( x) D ( z) 4
Gluon Sivers Asymmetry Sivers effect for also gluons? Gluon OAM? Recent review D. Boer et al., Adv. Hig Energy Pys., 015, 371396 (015). It can be studied wit te asymmetry for poton-gluon-fusion To enance te PGF, -adrons wit ig Pt are detected. adron N X p adron Te azimutal angle of te adron pair,, is strongly correlated wit te gluon azimutal angle g Data sample : 010 proton target, 003,4 deuteron target Event selection : Q > 1 ( GeV / c), W > 5 GeV / c, 0.9>y>0.1, P > 0.7 GeV / c, P > 0.4 GeV / c, z, z >0.1, z z 0.9 T1 T 1 1 Witout carge constraint for te adron pair 5
Gluon Sivers Asymmetry However, one as to take account of te background processes; signal + BG Te asymmetry can be decomposed as: MC fp A sin fp ( R A R A R A )sin Siv. Siv. Siv. Siv. T Siv. T PGF PGF QCDC QCDC LP LP Siv. Wit a elp of MC simulation, te process fractions(ri) are evaluated. Te MC simulation : Generator LEPTO + GEANT + Reconstruction program PDF: MSTW008 Parton sower: on FLUKA for secondary interactions Special generator tuning for ig-pt events Fitting te data wit Neural Network trained by te MC, eac asymmetry is determined. 6
Gluon Sivers Asymmetry : Results A 0.6 0.09( stat.) 0.06( sys.) Siv.p PGF xg 0.15 A 0.14 0.15( stat.) 0.10( sys.) Siv. d PGF xg 0.15 proton & deuteron combined A 0.3 0.08( stat.) 0.05( sys.) Siv. PGF Two standard deviation from zero Gluon Sivers effect? 7
Conclusions SIDIS gave and is giving fundamental contribution to te study of te transverse spin structure of te nucleon. COMPASS as provided TSA data for proton and deuteron. Te Collins asymmetries and Sivers Asymmetries were found to be different from zero for proton altoug tey are consistent wit zero for deuteron. Tere is an interplay between te single adron Collins asymmetries and di-adron asymmetries suggesting common origin in production mecanism. Te Sivers asymmetries were obtained in different Q ranges. One of te ranges corresponds to te di-muon mass range were te Drell-Yan measurement of COMPASS was performed. Te Sivers asymmetry for PGF was found to be negative wit two standard deviation from zero suggesting te possible gluon Sivers effect. 8
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Comparison wit calculations In good agreement wit te calculations in low-z & low Pt ranges. PBL 770 (017)138 Calculations are based on fits of onedimensional data ( PRD7(005)094007 [Erratum:PRD 7 099903(005)], EPJ A39 (009)89) However, in ig-z & ig-pt ranges, clear discrepancies are seen. PBL 770 (017)138 30
Expected property for te Sivers PDF Sivers function is process dependent. f ( x, k ) f ( x, k ) q q 1T SIDIS 1T DY sign cange! SIDIS : wit final state interaction (FSI) Drell-Yan: wit initial state interaction (ISI) p p p - (du) p attractive p repulsive g * ejected (red) quark is attracted by te anti-red spectators before anniilating wit te red active quark, te approacing anti-quark(anti-red) is repelled by te anti-red spectators Tis is to be cecked in te common kinematical region in COMPASS experimentally. 31
SIDIS Kinematics l ( E ) : p =,p ( E ) l : p =,p Q = - ( p - p ) n = E - E Lab. x = Q M y = n E n Dq ( z) Fragmentation Function E z = E n Energy fraction of te adron 3
Gluon Sivers Asymmetry : Results Asymmetries for PGF A 0.6 0.09( stast.) 0.06( sys.) Siv.p PGF A 0.14 0.15( stast.) 0.10( sys.) Siv. d PGF xg 0.15 xg 0.15 A 0.3 0.08( stast.) 0.05( sys.) Siv. PGF Asymmetries for BG 33