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Spin physics at the S pin M uon C ollaboration

This text discusses early measurements of the spin structure function in high-energy scattering experiments, such as the Spin Muon Collaboration (SMC) and the EMC collaboration at CERN. It covers topics such as flavor singlet and non-singlet components, Bjorken sum rule, and the role of orbital momentum in the nucleon spin. The text also mentions advancements in experimental setups and polarization techniques.

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Spin physics at the S pin M uon C ollaboration

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  1. Spin physics at the Spin MuonCollaboration A. Magnon (CEA-Saclay/IRFU & COMPASS)

  2. Spin structure function g1p(n) 1st moment Ellis Jaffe Sum Rule Phys. Rev. D9 (1974) Flavor singlet Flavor non singlets Bjorken Sum Rule Phys. Rev. 148 (1966) 2

  3. Nucleon Spin ½= ½DS+ DG+Lq + Lg quarkgluonorbital momenta • Naive quark parton model + relativistic corrections • DS~ 0.75the rest is given by orbital momentum L • QCD; Ellis - Jaffe, SU(3) assuming Ds =0 • DS ~ 0.60 3 12/7/2010 Alain Magnon

  4. Early measurements of DS (1) SLAC g1p Compatible with DS=0.6 xBj Phys. Rev. Lett. 51 (1983) 1135 V.W.Hughes SLAC with polarized e- Ee- = 16 and 22 GeV (1976 – 1983) DS large, “as expected” 4 Alain Magnon

  5. Early measurements of DS (2) EMC @ CERN with polarized m+ (1985-1986) E. Gabathuler 5 Alain Magnon

  6. Early measurements of DS (2) EMC @ CERN Em = 100, 120 and 200 GeV (1987-88) Phys.. Lett. B206 (1988) 364 Access lower x 6 Alain Magnon

  7. Early measurements of DS (2) Ellis-Jaffe DS=0.60 EMC ∫g1p xBjg1p xBj EMC @ CERN (1987-88) DS= 0.12 ± 0.17 →” Spin crisis ’’ 7 Alain Magnon

  8. Private conversation (~ end 1989) with B.Jaffe: “I have practiced QCD for so many years… our Sum Rule cannot be that wrong” 8 Alain Magnon

  9. Phone call from V.W.Hughes (~ end 1989): • “I do not exclude that the EMC measurement • is in error” • I am setting up SMC with several upgrades: • An improved beam line and beam definition • A new PT magnet solenoid of excellent uniformity • with a transverse dipole to reverse spin more often • A beam polarimeter to measure Pm • Polarized protons and deuterons to measure also the • neutron and verify the Bjorken Sum Rule • “Similar project are launched at SLAC and DESY” • Would you join SMC ? (I did in 1991) 9 Alain Magnon

  10. S SMC =162 S JINR/Dubna = 14 10 Alain Magnon

  11. The SMC @ CERN Beam Momentum Station m Beam polarimeter Beam Definition DT67 m-detection JINR/Dubna Forward Spectrometer Polarised target 11 Alain Magnon

  12. The SMC @ CERN The Polarised Target Few 10-5 field uniformity Frequent spin rotation Transverse polarisation 12 Alain Magnon

  13. ~ 5 years of data taking @ SMC ~25% then 13 Alain Magnon

  14. Enhanced deuteron polarization @ SMC It was found - “ intervention by Y.Kisselev on the regulator circuit of the HV supply of the mwave source” - that a significant increase in deuteron polarization is obtained by modulating rapidly the polarizing mwave frequency over a range of ~30 MHz With FM With FM 0.01 No FM F- F+ 14 Alain Magnon

  15. Enhanced deuteron polarization @ SMC 13 May 1995 We reached 100% With FM PD is  by ~1.7 No FM • sSTAT •  to • 1/(PDN1/2) 15 Alain Magnon

  16. SMC publications (1) - Measurement of the Spin-dependent Structure Function g1(x) of the Deuteron Phys. Lett. B 302 (1993) 533 - Measurement of the Polarization of a High Energy Muon Beam Nucl. Instr. and Meth. A 343 (1994) 363 - Combined analysis of world data on nucleon spin structure functions Phys. Lett. B 320 (1994) 400 - Measurement of the Deuteron Polarization in a Large Target Nucl. Instr. and Meth. A 349 (1994) 334 - Measurement of the Spin-dependent Structure Function g1(x) of the Proton Phys. Lett. B 329 (1994) 399 - Spin Asymmetry in Muon-Proton Deep Inelastic Scattering on a Transversely- Polarized Target Phys. Lett. B 336 (1994) 125 - A New Measurement of the Spin-dependent Structure Function g1(x) of the Deuteron Phys. Lett. B 357 (1995) 248 - Proceedings of Seventh International Workshop on Polarized Target Materials and Techniques Nucl. Instr. and Meth. A 356 (1995) No. 1 16

  17. SMC publications (2) • - Large Enhancement of Nuclear Polarization with Frequency Modulated Microwaves • Nucl. Instr. and Meth. A 372 (1996) 339 • - Polarisation of Valence and non-strange Sea Quarks in the Nucleon from Semi- inclusive Spin Asymmetries • Phys. Lett. B 369 (1996) 93 • The Spin-Dependent Structure Function g1(x) of the Deuteron from Polarized Deep-Inelastic Muon • Scattering • Phys. Lett. B 396 (1997) 338 • The Spin-Dependent Structure Function g1(x) of the Proton from Polarized Deep-Inelastic Muon • Scattering • Phys. Lett. B 412 (1997) 414 • - Spin structure of the proton from polarized inclusive deep-inelastic scattering • Phys. Rev. D56 (1997) 5330 • - A Line-shape Analysis for Spin-1 NMR Signals • Nucl. Instr. and Meth. A 398 (1997) 109 • - Measurement of Proton and Nitrogen Polarization in Ammonia and a Test of Equal Spin Temperature • Nucl. Instr. and Meth. A 419 (1998) 60 • - Polarised Quark Distributions in the Nucleon from Semi-Inclusive Spin-Asymmetries • Phys. Lett. B420 (1998) 180 17

  18. SMC publications (3) - Spin Asymmetries A1 and structure functions g1 of the proton and the deuteron from polarized high energy muon scattering Phys. Rev. D58 (1998) 112001 - A next-to-leading order QCD analysis of the spin structure function g1 Phys. Rev. D58 (1998) 112002 - A large streamer chamber muon tracking detector in a high-flux fixed-target application Nucl. Instr. and Meth. A 435 (1999) 354 - The SMC polarized target Nucl. Instr. and Meth. A 437 (1999) 23 - Spin Asymmetries A1 of the Proton and the Deuteron in the Low x and Low Q2 Region from Polarized High Energy Muon Scattering Phys. Rev. D60 (1999) 072004, Erratum-ibid.D62 (2000) 079902. - Measurement of the SMC muon beam polarisation using the asymmetry in the elastic scattering off polarised electrons Nucl. Instr. and Meth. A443 (2000) 1 - Spin asymmetries for Events with High Pt Hadrons in DIS and an Evaluation of the Gluon Polarization Phys. Rev. D70, 012002 (2004) Final results, also using hadron-tagging at low xBj < 0.02 In total 23 SMC Publications 18

  19. Conclusions from SMC Phys. Rev. D58 (1998) 112002 ------------------------------------------------------------ Q02 = 10 GeV2 ------------------------------------------------------------ 1p 1d 1p- 1n SMC 0.120±0.016 0.019±0.014 0.198±0.023 Ellis/Jaffe 0.170±0.004 0.071±0.004 Bjorken 0.187±0.002 ------------------------------------------------------------ Ellis/Jaffe Sum Rule NOT verified Bjorken Sum Rule IS verified 19 Alain Magnon

  20. Conclusions from SMC Need to get DG -- HERMES COMPASS RHIC -- COMPASS-II (GPDs, DY & Primakoff) DS = 0.6 a0 ~ 0.3 DG~2 DG 20 Alain Magnon

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