Hadron Structure at COMPASS on behalf of the COMPASS Collaboration - PowerPoint PPT Presentation

Hadron Structure at COMPASS on behalf of the COMPASS Collaboration Krzysztof Kurek, National Centre for Nuclear Reserach, Otwock- Ś wierk, Poland COMPASS Hadronic Physics with Lepton and Hadron Beams, JLab, September 5-8, 2017

Beam: 2 . 10 8 µ + / spill (4.8s / 16.2s) Beam: 2 . 10 8 µ + / spill (4.8s / 16.2s) COMPASS Collaboration at CERN Luminosity ~5 . 10 32 cm -2 s -1 Luminosity ~5 . 10 32 cm -2 s -1 Beam polarization: -80% Beam momentum: 160 & 200 GeV/ c Beam polarization: -80% LHC Beam momentum: 160 GeV/ c Common Muon and Proton Apparatus for Structure and Spectroscopy ~220 physicists, 13 countries 24 institutes COMPASS SPS Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 2 / 46 JLab 5-8 September 2017

COMPASS in muon run The COMPASS spectrometer NIM A 577(2007) 455 
 Trigger Hodoscopes ECALs & HCALs MWPCs 50 m SM2 RICH SM1 Drift Chambers µ Filters/ 6 LiD target Walls Straws • ~ 350 planes • 180 mrad acceptance GEMs 160 GeV µ Si • π , K, p separation Micromegas SciFi (from 2, 9, 17 GeV up veto to ~ 50 GeV) Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 3 / 46 JLab 5-8 September 2017

The COMPASS polarized target and PID Target material: 6 LiD NH 3 Polarisation: >50% ~90% Dilution factor: ~0.4 ~ 0.25 Dynamic Nuclear Polarization 2006 - new solenoid with acceptance 180 mrad 3 target cells (reduce false asymmetries) 2002 − 2004  2006 RICH 2006 upgrade : better PID MAPMTs in central region APV electronics in periphery Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 4 / 46 JLab 5-8 September 2017

Contents • Introduction • DIS, SIDIS & gluon polarisation results from COMPASS • TMD results from COMPASS • DVCS results from COMPASS • DY results from COMPASS • Summary Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 5 / 46 JLab 5-8 September 2017

Beams and targets at COMPASS muon beam deuteron ( 6 LiD) PT 2002 80% L/20% T target polarisation 2003 2004 2006 L target polarisation proton (NH 3 ) PT 2007 50% L /50% T target polarisation Hadron LH target 2008 2009 muon beam proton (NH 3 ) PT 2010 T target polarisation 2011 L target polarisation Hadron Ni target 2012 Primakoff muon beam LH2 target 2012 Pilot DVCS & unpol. SIDIS Hadron Proton (NH3) DT 2014 Pilot DY run PT 2015 DY run 2018 2° year of DY run muon beam LH2 target 2016 DVCS & unpol. SIDIS 2017 Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 6 / 46 JLab 5-8 September 2017

Basic tool: the measurement of inclusive and semi-inclusive asymmetry Inclusive asymmetry: Semi-inclusive asymmetry: Compass g 1 results: deuteron/proton 160 GeV Phys. Lett. B 647 (2007) 8, 330 (low Q 2 ) Phys. Lett. B 690 (2010) 466 proton 200 GeV Phys. Lett. B 660 (2008) 458 Phys. Lett. B 680 (2009) 217 inclusive and semi-inclusive asymmetry measured on proton and neutron Phys. Lett. B 693 (2010) 227 or deuteron allows to full flavour separation Phys. Lett. B 753 (2016) 18 Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 7 / 46 JLab 5-8 September 2017

First moment of g 1 structure functions Sum rules from Y. Goto et al ., PRD62 (2000) ∫ g 1 ( x ) dx first moment Γ 1 = 034017: (SU(3) f assumed for weak decays) a 8 = 0.585 ± 0.025 n = g A p − Γ NS Bjorken s.r. C 1 Γ 1 1 6 g V NS S   p , n = ± a 3 + a 8  C 1 C 1 12 + a 0 Ellis-Jaffe s.r. Γ  1 3 9   measuered in weak β decays (+Su(3) f ) calculable in pQCD MS scheme: a 0 depends on the scale AB scheme: a 0 does not depend on the scale but now α S a 0 = ΔΣ = Δ u + Δ d + Δ s a 0 = ΔΣ − 3 π Δ G 2 Quark contribution to nucleon helicity Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 8 / 46 JLab 5-8 September 2017

First moment of g 1 structure functions Compass only PLB 647 (2007) 8   9 1 − α s ( Q 2 )   ) = 1  a 0 ( Q 2 ) + 1 N Q 2 ( 2 ) Γ + O ( α s 4 a 8    1 π     QCD NLO 2006 data reanalysed 2x statistics new QCD COMPASS fit PLB 753 (2016) 18 S ( Q 2 )  ) = 1 0 + 1 N Q 2 ( NS ( Q 2 ) a 8 beyond NLO 9 C 1 a 36 C 1 Γ 1 C 1 calculated behind 3 loops app. ˆ a 0| Q 2 →∞ = 0.33 ± 0.03( stat ) ± 0.05( syst ) S.A.Larin et al ., Phys.Lett.B404(1997)153 ) = 1 3( ˆ ( Δ s + Δ s a 0 − a 8 ) = − 0.08 ± 0.01( stat ) ± 0.02( syst ) Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 9 / 46 JLab 5-8 September 2017

g1 structure function for deuteron Compass data 2002-2006 and world data 2002-2004 published in PLB 647 (2007) 8 New: Proton da 2006 reanalysed, new NLO COMPASS fit PLB 753 (2016) 18 Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 10 / 46 JLab 5-8 September 2017

g1 structure function for proton Compass data 2007 & 2011 and world data PLB 690 (2010) 466–472 New: Proton da New 2011 proton data & new COMPASS NLO QCD fit PLB 753 (2016) 18 2007: 160 GeV/c 2011: 200 GeV/c Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 11 / 46 JLab 5-8 September 2017

New COMPASS NLO QCD fit Inclusive world data used + new COMPASS PLB 753 (2016) 18 Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 12 / 46 JLab 5-8 September 2017

Test of Bjorken sum rule Compass data (2011 data & new QCD fit included) PLB 690 (2010) 466–472 , PLB 753 (2016) 18 C NS = 0.89 Q 2 = 3 (GeV/c) 2 1.29 0.05 0.1 Flavor separation: PLB 647 (2007) 8 & 690 (2010) 466 Difference asymmetry PLB 660 (2008) 458 Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 13 / 46 JLab 5-8 September 2017

Test of Bjorken sum rule Compass data (2011 data & new QCD fit included) PLB 690 (2010) 466–472 , PLB 753 (2016) 18 C NS = 0.89 Q 2 = 3 (GeV/c) 2 0.7 2 2 2 2 SIDIS+DIS, Q SIDIS+DIS, Q =10 GeV =10 GeV ∫ x ( u + d )dx ∆ ∆ v v 0.6 u = d = s= s ∆ ∆ ∆ ∆ COMPASS 0.5 1.29 0.05 0.1 0.4 unmeasured 0.3 u =- d ∆ ∆ 0.2 0.7 ∫ ( u + d )dx=0.40 0.07 0.06 ∆ ∆ ± ± 0.1 v v 0.006 0 -2 -1 10 10 1 x Flavor separation: PLB 647 (2007) 8 & 690 (2010) 466 Difference asymmetry PLB 660 (2008) 458 Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 13 / 46 JLab 5-8 September 2017

Direct gluon polarisation measurement via tagging PGF process Non direct measurement of gluon polarisation - QCD fits To select PGF process two methods are used @COMPASS: • Open-charm D meson production: charm quark pairs produced in PGF, “clean” channel however with huge combinatorial background, low statistics but analysis less MC dependent • High transverse momentum hadron pairs/single production: light quark pairs produced, high statistics but physical background; strongly model and MC dependent analysis, requires a very good agreement between data and MC R.D.Carlitz, J.C.Collins and A.H.Mueller, PLB 214, 229 (1988) Revisited by A.Bravar,D.von Harrach and A.Kotzinian, PLB 421, 349 (1998) Applied by SMC, HERMES and COMPASS from MC signal asymmetry from data Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 14 / 46 JLab 5-8 September 2017

Large Q 2 : Q 2 > 1 (GeV/c) 2 Physical model: three processes (LO QCD) QC LO N QCD-Compton PGF LO-DIS Same decomposition for inclusive sample to determine A 1LO Optimization needed : “clean” (more PGF, “pure”) sample with limited statistics or less PGF populated but larger sample Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 15 / 46 JLab 5-8 September 2017

Results for low Q 2 : Q 2 < 1 (GeV/c) 2 Cuts used – cut on Σ p T 2 > 2.5 (GeV/c) 2 2002-03 results published: PLB 633 (2006) 25 90% of statistics! PYTHIA generator for low Q ² + spectrometer simulation p T Data & MC Data/MC Data MC.syst resolved ( Δ G/G) stat exp.syst 02-03 0.024 0.089 0.014 0.052 0.018 02-04 0.016 0.058 0.014 0.052 0.013 Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 16 / 46 JLab 5-8 September 2017

New asymmetries (1h) for low Q 2 2006 and 2011 data included COMPASS PLB 753 (2016) 573 NLO calculations M. Stratmann, B Jager, W. Vogelsang EPJC 44(2005) 533 LL d η ∈ [-0.1,0.45] η ∈ [0.45,0.9] η ∈ [0.9,2.4] A COMPASS: potentially discriminated power 0.2 0.2 0.2 + h on gluon polarisation 0.1 0.1 0.1 0 0 0 LL 1 2 3 1 2 3 1 2 3 d A 0.1 0.1 0.1 - h 0 0 0 LL [-0.1,0.45] [0.45,0.9] [0.9,2.4] p η ∈ η ∈ η ∈ A GRSV GRSV − 0.1 0.1 0.1 min max 0.2 0.2 0.2 GRSV + DSSV14 h std 1 2 3 1 2 3 1 2 3 p (GeV/c) p (GeV/c) p (GeV/c) T T T 0.1 0.1 0.1 0 0 0 LL 1 2 3 1 2 3 1 2 3 p A 0.1 0.1 0.1 - h Discrepancy on the level of cross section! 0 0 0 gluons resummation needed? GRSV GRSV min max − 0.1 0.1 0.1 GRSV DSSV14 std COMPASS PRD 88 (2013) 091101 1 2 3 1 2 3 1 2 3 p (GeV/c) p (GeV/c) p (GeV/c) calculations PRD 88 (2013) 014024 T T T Hadronic Physics with Lepton and Hadron Beams COMPASS Krzysztof Kurek 17 / 46 JLab 5-8 September 2017