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D.Peshekhonov JINR, Dubna on behalf of the COMPASS collaboration

“Spin physics at COMPASS-II and perspectives of the spin physics at JINR”. D.Peshekhonov JINR, Dubna on behalf of the COMPASS collaboration. Plan. Introduction - nucleon spin - status of the problem Spin physics at COMPASS-II - GPD (DVCS) - TMD (SIDIS, Drell-Yan)

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D.Peshekhonov JINR, Dubna on behalf of the COMPASS collaboration

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  1. “Spin physics at COMPASS-II and perspectives of the spin physics at JINR” D.Peshekhonov JINR, Dubna on behalf of the COMPASS collaboration D.Peshekhonov

  2. Plan • Introduction - nucleon spin - status of the problem • Spin physics at COMPASS-II - GPD (DVCS) - TMD (SIDIS, Drell-Yan) • Spin physics at JINR - NICA facility - spin physics program at NICA D.Peshekhonov

  3. Nucleon spin SQM:up and down quarks carry the nucleon spin! EMC: Quarks spins contribute little (1987/88)ΔΣ = 0.12 D.Peshekhonov

  4. Nucleon spin SQM:up and down quarks carry the nucleon spin! EMC: Quarks spins contribute little (1987/88)ΔΣ = 0.12 quarks gluons orbital small ~0.15 Still poorly known unknown D.Peshekhonov

  5. Laboratories & SLAC CERN 49 GeV e– 160/280 GeV µ+ DESY RHIC JLab 27 GeV e± 6 GeV e – 250+250 GeV pp D.Peshekhonov

  6. & Experiments A worldwide effort since decades E80 E130 E142/3 E154/5 EMC SMC COMPASS HERMES CLAS/HALL-A Phenix/Star D.Peshekhonov

  7. Tools to study the spin structure DIS SIDIS pp D.Peshekhonov

  8. Parton Distribution Functions unpolarised PDF quark with momentum xP in a nucleon well known – unpolarized DIS q(x) f1q (x) helicity PDF quark with spin parallel to the nucleon spinin a longitudinally polarised nucleon known – polarized DIS Dq(x) g1q(x) transversity PDF quark with spin parallel to the nucleon spin in a transversely polarised nucleon DTq(x) h1q(x) chiral odd, poorly known D.Peshekhonov

  9. Examples of some results Structure function g1(x,Q2) p • very precise data • only COMPASS for x < 0.01 (Q2 > 1) • deuteron data: • ΔΣ= 0.33±0.03±0.05 • Δs+Δs = =−0.08±0.01±0.02 • (ΔΣ = a0, evol. to Q2=∞) d D.Peshekhonov

  10. Examples of some results The quark flavours • LO semi-inclusive data analysis D.Peshekhonov

  11. Examples of some results Bjorken sum rule from neutron β decay D.Peshekhonov

  12. Examples of some results Gluon polarization from PGF Data not yet in global fits D.Peshekhonov

  13. What’s next? 1 COmmon Muon and Proton Apparatus for Structure and Spectroscopy Focus on transverse structure of the nucleon • Transverse size and orbital angular momentum (GPDs) → • → DVCS & DVMP with μ beams • Transv.Momentum Dependent PDFs: • Sivers, Boer-Mulders, sign change from SIDIS to DY, • additional TMDs (pretzelozity, worm-gear) → • → Drell-Yanwith  beams D.Peshekhonov 13

  14. 24 Exploring the 3-dimensional phase-space structure of the nucleon From Wigner phase-space-distributions (Ji, PRL 2003, Belitsky, Ji, Yuan PRD 2004) Wecanbuild « mother-distributions » (Meissner, Metz, Schlegel, JHEP 0908:056 2009) and derive • GPD: Generalised Parton Distribution (position in the transverse plane) • TMD:Transverse Momentum Distribution (momentum in the transv. plane) k PDF GPD TMD D.Peshekhonov

  15. SPS proton beam: 2.6 1013/spill of 9.6s each 48s, 400 GeV/c • Secondary hadron beams (, K, …): 6.108 /spill, 50-200 GeV/c • Tertiary muon beam (80% pol): 4.6108 /spill, 100-200 GeV/c • -> Luminosity ~ 1032 cm-2 s-1 GPD with+and a 2.5m long LH target • ~1.2 1032 cm-2 s-1 DYwith -and a 1.1m long NH3 target LHC COMPASS CNGS Gran Sasso 732 kms SPS high energy beams, broad kinematic range, large angular acceptance

  16. GPD Functions • Allow for a unified description of form factors • and parton distributions • Allow for transverse imaging (nucleontomography) and give access to the quark angular momentum (through E) • X.-D. Ji, Phys. Rev. Lett. 78 (1997) 610 Total orbital momentum: x is not x-Bjorken   xB / (2-xB) D.Peshekhonov

  17. Tomographic image of the nucleon • t = −ΔT2 For fixed x GPD H describes the distribution of the transverse distance b of the constituent carried fraction x of the longitudinal momentum p from the center of the nucleon D.Peshekhonov

  18. Experimental requirements for DVCS μ p  μ’ p  μ’  ~ 2.5 m Liquid Hydrogen Target ~ 4 m Recoil Proton Detector (RPD) SM2 ECAL2 SM1 ECAL1 • ECALs upgraded • + ECAL0 before SM1: • increase hermeticity • decrease background • enlarge acceptance μ p’ D.Peshekhonov

  19. Contributions of DVCS and BH at E=160 GeV  μ’ * θ μ p  Deep VCS Bethe-Heitler d  |TDVCS|2 + |TBH|2 + InterferenceTerm Monte-Carlo Simulation for COMPASS set-up with only ECAL1+2 • Missing • DVCS acceptance • without ECAL0 BH dominates study of Interference DVCS dominates excellent  Re TDVCSstudy of dDVCS/dt reference yieldor Im TDVCS Transverse Imaging D.Peshekhonov

  20. DVCS • GPDs need a world-wide effort • Global analysis over large kinematic range mandatory • COMPASS-II: from HERA to JLAB 11 GeV kinematics • The GPD H can be constrained by beam charge and spin (μ+μ−) combinations using an unpolarized proton target • E GPDs require transversely pol. target (later) D.Peshekhonov

  21. Deeply Virtual Compton Scattering Study the transverse imaging with +, - beam and unpolarized 2.5m long LH2 (proton) target • SCS,U  d( +) +d( -) Im(F1 H) Using SCS,U and integration over   and BH subtraction dDVCS/dt~exp(-B|t|)  d( +) -d( -) • DCS,U  Re(F1 H) Re H (,t)= Pdx H(x,,t) /(x-) Im H (,t)=H(x= ,,t) D.Peshekhonov

  22. Deeply Virtual Compton Scattering B(xB) = b0 + 2 α’ ln(x0/xB) α’slope of Reggetraject without any model we can extract B(xB) B(xB) = ½ < r2 (xB) > r is the transverse size of the nucleon D.Peshekhonov

  23. Parton Distribution Functions • 8 PDFs at LO • Azimuthal asymmetries with different angular modulations in the hadron and spin azimuthal angles, Φh and Φs aka Sivers Transversity Boer– Mulders D.Peshekhonov

  24. Experimental check of the change of sign of TMDsconfrontingDrell-Yan and SIDIS results The T-odd character of the Boer-Mulders and Sivers function implies that these functions are process dependent `gauge link changes sign for T-odd TMD’, restricted universality of T-odd TMDs FSI ISI Need experimental verification Test of consistency of the approach Boer-Mulders Sivers D.Peshekhonov

  25. Polarised Drell-Yan • COMPASS-II: 190 GeV/c− beam on transversely pol. proton target • − valence u-antiquark picks nucleon’s u quarkin valence region (u-quark dominance) • Access to transversity , the T-odd Sivers and Boer-Mulders TMDs and `pretzelozity’ D.Peshekhonov

  26. 15 The Drell-Yan process in π- p • Access to TMDs for incoming pion  target nucleon • TMD as Transversity, Sivers, Boer-Mulders, pretzelosity Hadron plane Collins-Soper frame (of virtual photon) ,  lepton plane wrt hadron plane target rest frame Starget transverse spin vector /virtual photon Lepton plane

  27. DY and COMPASS set-up π- 190 GeV • Key elements for a small cross section investigation at high luminosity • Absorber (lesson from 2007-8 tests) to reduce secondary particle flux • COMPASS Polarised Target • Tracking system and beam telescope • Muon trigger (LAS of particular importance - 60% of the DY acceptance) • RICH1, Calorimetry – also important to reduce the background

  28. COMPASS polarized DY dominated by the annihilation of a valence anti-quark from the pion and a valence quark from the polarised proton xp large acceptance of COMPASS in the valence quark region for p and π where SSA are expected to be larger x xF=x−xp xF D.Peshekhonov

  29. TMDs at Drell-Yan: road map • 2010 – COMPASS polarised SIDIS data (Sivers, transversity via global data fit) • 2013 - 2016 COMPASS polarised Drell-Yan pi-p data – TMDs universality and T-odd TMDs sign change SIDISDY • 2015  …… RHIC, NICA pp (un)polarised DY data • 2020  GSI antiproton data D.Peshekhonov

  30. Future DY experiments D.Peshekhonov

  31. Collider 2T C = 336 m NICA Layout & Main Elements 2.3 m 4.0 m Booster KRION-6T & HILac Synchrophasotron yoke “Old” linac MPD Beam transfer line Existing beam lines (Fixed target exp-s) Nuclotron Spin Physics Detector (SPD) D.Peshekhonov

  32. Spin Physics atNICA • The spin program at NICA is under preparation. The main topics are: • Studies of Drell-Yan processes with longitudinally and transversely polarized • p and D beams. Extraction of unknown and poor known PDFs • PDF from J/Ψ production processes • Spin effects in baryon, meson and photon production • Study of spin effects in various exclusive processes • Diffractive processes studies • Cross sections, helicity amplitudes and double spin asymmetries • (Krisch effect) in elastic reactions • Spectroscopy of quarkonium D.Peshekhonov

  33. Spin Physics atNICA - polarized DY From report by A. Nagaytsev, IWSS2010 The set of original software packages (MC simulation, generator etc.) were developed for the feasibility studies of DY polarized processes The SSA asymmetries. Top:access to transversity and Boer-Mulders PDFs. (Sissakian, Shevchenko, Nagaytsev,PRD 72 (2005), EPJ C46 (2006)) Bottom: access to Sivers PDFs (Efremov,… PLB 612(2005), PRD 73(2006)); Asymmetries are estimated for 100 K DY events D.Peshekhonov

  34. Spare

  35. COMPASS-II 2.3 23 *  Q² x+ x- p GPDs t From inclusive to exclusive reactions DeepInelasticScattering Deeply Virtual Compton Scattering p  ’X p ’p’ ’  Q²xB γ* x z p P’ z x P x P b y y x boost x boost Distrib. de Partons q ( x ) Generalized Partons Distrib. H(x,,t ) Px • ( Px,b) Observation of the Nucleon Structure in 1 dimension in 1+2 dimensions

  36. DVCS: Transverse imaging at COMPASS dDVCS/dt ~ exp(-B|t|) ansatz at small xB inspired by Regge Phenomenology: B(xB) = b0 + 2 α’ln(x0/xB) α’slope of Reggetraject • B with an accuracy of 0.1 GeV-2 • α’with an accuracy 2.5 • ifα’ 0.26 with ECAL1+2 • ifα’ 0.125 with ECAL0+1+2 with the projected uncertainties we can determine :

  37. T-odd TMD in SIDIS and DY • J.C. Collins, Phys. Lett. B536 (2002) 43 `gauge link changes signfor T-odd TMD’, restricted universality of T-odd TMDs SIDIS: FSI DY:ISI

  38. Single-polarised DY cross-section: Leading order QCD parton model, TMD PDFs universality At LO the general expression of the DY cross-section simplifies to (Aram Kotzinian): Thus the measurement of 4 asymmetries (modulations in DY cross-section):

  39. DVCS • GPDs need a world-wide effort • Global analysis over large kinematic range mandatory • COMPASS-II: from HERA to JLAB 11 GeV kinematics • H GPDs can be separated from BH and constrained by beam charge & spin (μ+μ−) combinations • E GPDs require transversely pol. target (later)  

  40. Transversity PDF • Couple to chiral odd Collins FF Azimuthal cross-section asymmetry: D.Peshekhonov

  41. Sivers function • Sivers Asymmetry: • proposed (1990, Sivers) • thought to vanish (1993, Collins) • resurrected (2002, Brodsky, Hwang, Schmitt) • different sign in DY and SIDIS D.Peshekhonov

  42. SIDIS & Drell-Yan to study TMDs Drell –Yan π- p +-X with intense pion beam (up to 109 /spill) with the transverselypolarised NH3target with the COMPASS spectrometerequippedwith an absorber - Cross sections: In SIDIS: convolution of a TMD with a fragmentation function In DY: convolution of 2 TMDs ‘’’’  complementary information and universality test ‘ D.Peshekhonov

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