Measurements with Polarized Hadrons

Transcription

1 Aug 15, 003 Lepton-Photon 003 Measurements with Polarized Hadrons T.-A. Shibata Tokyo Institute of Technology

2 Contents: Introduction: Spin of Proton Polarized Deep Inelastic Lepton-Nucleon Scattering 1. Flavor Separation of Quark Helicity Distributions. Deeply Virtual Compton Scattering 3. Single-Spin Azimuthal Asymmetries in Semi-Inclusive Deep Inelastic Scattering Polarized Proton-Proton Collisions T.-A. Shibata

3 Introduction: Measurements with Polarized Hadrons Eplore spin structure of hadrons and further develop QCD using Spin QCD was successful, both in perturbative and non-perturbative regions, but spin of the nucleon still needs to be studied in many aspects to be fully eplained with QCD. T.-A. Shibata 3

4 Introduction : Spin of Proton 1 / - 1 / 1 / SU6 Quark Wave Functions of Baryons Sum of Spins of u u d Quarks = Spin of Proton 1 / = = 1 EMC Eperiment u + d + s = ± ± ± 9 ± 14% G T.-A. Shibata % of Nucleon Spin 1 = u + d + s + L + J Nucleon Spin Problem

5 Introduction: Measurements with Polarized Hadrons Eperimental Methods: Lepton-Hadron Scattering, Hadron-Hadron Collision Fied Target Eperiments : Polarized Targets + Polarized Beams Nucleon p, n + e + /e - e - + µ / µ HERMES SLAC, JLab COMPASS Collider Eperiments : Polarized Proton - Proton Collisions RHIC T.-A. Shibata 5

6 Deep Inelastic Scattering, Semi-inclusive Measurements e Inclusive measurement, e σ e e Semi-inclusive measurement, e and π,k,p,p... h σ, z e D z h Flavor tagging uark distribution fragmentation function z = E h /ν T.-A. Shibata 6

7 Detectors HERA Polarized Internal gas targets 3 He, H, D 7.6 GeV e Target T.-A. Shibata 7

8 Compass Set-up CERN 160GeV µ Gluon Spin Contribution D s identified in 00. magnets muon filter polarized target RICH G T.-A. Shibata 8 N γ Photon Gluon Fusion c c

9 1. Flavor Separation of Quark Helicity Distributions u, d, u, d, s T.-A. Shibata 9

10 Quark Helicity Distributions, Flavor Separation Double-spin asymmetry r e + N r e + X Beam and target, both polarized Virtual photon... Nucleon σ A 1, z = σ σ T.-A. Shibata 10 + σ

11 Quark Helicity Distributions, Flavor Separation Double-spin asymmetries A h 1 d from semi-inclusive DIS Hadron identification for the first time A h + 1 K + K - π π π ±, K + asymmetries similar to inclusive asymmetry, - ecept K asymmetry. HERMES T.-A. Shibata 11

12 T.-A. Shibata 1 Quark Helicity Distributions, Flavor Separation, z D e z h h σ Semi-inclusive DIS cross section Double-spin asymmetry /ν z = E h = + = h h h h h h h z D e z D e z z z z z A,,,,, 1 σ σ σ σ Q P A r r = 1,,,, s s d d u u d d u u Q = r X m e N e r r + = = Quark Helicity Distributions Quark Density Distributions,K s u us + Κ unconstrained s N = p, d m = ± ± Κ, π unpol. PDF and FF from data of unpol. semi-inclusive DIS

13 HERMES Flavor Separation, Quark Helicity Distributions u d u d s Result: X bin by bin analysis ecept for smearing correction. No functional forms are assumed. No first moments are assumed. Helicity conservation not assumed 1 as 1 etc. Error band systematic error QCD fits to inclusive measurements T.-A. Shibata 13 d d u > 0 d < 0 0

14 . Deeply Virtual Compton Scattering -- Generalized Off-forward Parton Distributions T.-A. Shibata 14

15 Deeply Virtual Compton Scattering Coss section for inclusive deep inelastic scattering Deeply Virtual Compton Scattering DVCS -- Eclusive production of a real photon γ γ γ γ Im p ξ GPD + ξ p + = ξ t = BJ BJ :Light cone momentum fraction :Echanged longitudinal momentum fraction T.-A. Shibata :Momentum transfer 15

16 Generalized Off-Forward Parton Distributions Deeply Virtual Compton Scattering Eclusive Meson Production Deep Inelastic π, ρ, φ, Scattering, Generalized Parton Distributions GPD H, E ~, H ~, E γ ω F 1, F Electromagnetic Form Factors Elastic Scattering Total Angular Momentum J Orbital Angular Momentum L T.-A. Shibata 16

17 Generalized Parton Distributions H ~ ~, ξ, t, E, ξ, t, H, ξ, t, E, ξ, t Forward limit t 0, ξ 0 H, 0, 0 =, Sum rules, ~ H, 0, 0 = integral, sum over, ξ, t F t, E, ξ, t F t ~, ξ, t g A t, E, ξ, t h A t H 1 ~ H lim 1 t d [ H, ξ, t + E, ξ, t] = 1 1 J = + L z Dirac and Pauli Nucleon Form Factors Aial-vector and Pseudoscalar Form Factors T.-A. Shibata 17 J Ordinary Quark Distributions Total angular momentum Orbital angular momentum nd moment

18 Deeply Virtual Compton Scattering How to measure DVCS Deeply Virtual Compton Scattering 4 d σ A + A = A + DVCS BH DVCS dφ dt dq d r ± s ± σ LU = σ e p - σ e p m sinφ Im I σ ch + = σ e p - σ e p cosφ Re Bethe-Heitler Process, known calculable I A BH + I φ Beam-spin asymmetry by HERMES and CLAS Beam-charge asymmetry by HERMES -- DVCS-BH Interference, Real and Imaginary DVCS Cross Section by ZEUS and H1 T.-A. Shibata 18

19 Deeply Virtual Compton Scattering First observation of beam-spin asymmetry of DVCS A LU HERMES 001 CLAS 001 φ ~ 30% effect T.-A. Shibata 19 φ

20 Deeply Virtual Compton Scattering, Generalized Parton Distributions Beam-Spin Asymmetry sin φ Moment HERMES φ M X Missing Mass Resolution 0.8 GeV T.-A. Shibata 0

21 Deeply Virtual Compton Scattering, Generalized Parton Distributions Beam-Charge Asymmetry cos φ Moment HERMES φ M X Missing Mass Resolution 0.8 GeV T.-A. Shibata 1

22 How to etend Quantum number of final state Select different GPD γ Eclusive Meson Productions π γ ρ, φ, ω GPD GPD ~ H Pseudo scalar meson, ξ, t, ~ E, ξ, t H Vector meson, ξ, t, E, ξ, t HERMES s data T.-A. Shibata

23 3. Single-Spin Azimuthal Asymmetry in Semi-inclusive Deep Inelastic Scattering Quark Transversity Distributions δ T.-A. Shibata 3

24 3 leading twist uark distributions δ: Last unmeasured leading twist distribution T.-A. Shibata 4

25 Single-Spin Azimuthal Asymmetries in Semi-Inclusive DIS, Transversity γ γ γ A h e δ H1, z δ h Quark Density Distributions Quark Helicity Distributions Helicity difference, aial charge Quark Transversity Distributions δ Spin averaged, vector charge Helicity flip, tensor charge 1 δ + is Chiral Odd. Not accessible with inclusive DIS It is accessible with semi-inclusive DIS, accompanied with a Chiral Odd Fragmentation Function H 1 z δ does not couple with gluon. Collins FF Q evolution is different from, Soffer bound

26 Single-Spin Azimuthal Asymmetries in Semi-Inclusive DIS e + N e + m + X N N HERMES, JLab HERMES, COMPASS, JLab Longitudinally Polarized Target Transversely Polarized Target φ s S T Azimuthal Angle φ M Q 1 y = < sinθ γ > with respect to γ φ dependence Azimuthal Angle φ φ + φ s φ φ s dependence dependence T.-A. Shibata 6

27 A UL + π 0 π π + K Single-Spin Azimuthal Asymmetries in Semi-Inclusive DIS A UL Longitudinally polarized target, Target Spin Asymmetry A UL φ = e + d e + m + 1 p sinφ A UL N φ / L + N X φ / L L L N φ / L N φ / P 1 sinφ sinφ moment ~ 0 P1 sinφ + P sinφ + 0 positive for π, π, K Increases with nearly zero for π + φ HERMES T.-A. Shibata 7

28 A ~ S < sinφ > S < sinφ > sinφ UL L Transversely polarized target data can distinguish between the two. becomes dominant. < sin φ + φ < sin φ φ < sinφ > s > UT s > UT UL T Origins of moment, Longitudinally polarized target 1 φ = 0, 1, ~ < sinφ > S UL ~ e hl H1 z h1l H z Q z < sinφ >, ~ e UT H z δ Collins Effect: 1 Quark transversity distribution Chiral odd FF ~ e f T D z 1 1 see also polarized pp collisions S T moment: Collins Effect moment: Sivers Effect HERMES 00-- focused on it. 700K D.I.S. events recorded. Further data taking COMPASS data at higher Q, JLab T.-A. Shibata 8 Q evolution of δ, Q UT Sivers Effect:

29 Polarized Proton-Proton Collisions T.-A. Shibata 9

30 Polarized Proton-Proton Collision Polarized Parton-Parton Collision Gluon spin contribution to the nucleon spin Gluon Compton scattering g + γ + p r g p r γ jet jet production 0 Inclusive π measurement g + g jet π 0 + g + + jet A G 1 LL a LL G 1 T.-A. Shibata 30 ˆ

31 Polarized pp Collisions at RHIC 100 GeV GeV 001/00 P = ~0., Int L ~ 0.3 pb -1, transverse - May 003 P = ~0.3, Int L ~ 0.8 pb -1, transverse + longitudinal Physics Goal P = 0.7, Int L = 30 pb -1, at GeV 800 pb -1, at GeV

32 Polarized pp Collisions at RHIC 0 PHENIX and STAR collected data of inclusive π production Single-Spin Asymmetry, Transversely Polarized Beam STAR p + p π 0 + X, s = 00 GeV 0 Forward π, small p T Similar to the earlier Fermilab data at s=0 GeV, p T = GeV/c Double spin asymmetry, A LL, at large p T will become available soon T.-A. Shibata 3

33 Conclusions 1 To understand hadrons in terms of QCD, Spin Structure of the Nucleon is an important subject. Many eperiments are currently running with e, µ, γ,p... beams at different labs in the world. Flavor separation of uark helicity distributions has been made. Deeply Virtual Compton Scattering provides access to Generalized Parton Distributions. Single-spin azimuthal asymmetries in semi-inclusive DIS have been observed. Quark Transversity Distributions δ is a new subject which is being investigated. Results from transversely polarized targets will become available soon. T.-A. Shibata 33

34 Conclusions Polarized proton-proton collider has now longitudinally as well as transversely polarized beams. Single-spin asymmetries in 0 π productions at small angles from transversely polarized beam have been obtained. The asymmetries at large p T are being analyzed. Spin physics with the nucleon is a rapidly epanding field. Many new ideas of measurements are being proposed. High precision data as well as new surprises are epected. T.-A. Shibata 34