Spin physics at the SMC Spin Muon Collaboration A. Magnon (CEA-Saclay/IRFU & COMPASS)
Spin structure function g 1 p(n) Flavor singlet Flavor non singlets Bjorken Sum Rule Phys. Rev. 148 (1966) Ellis Jaffe Sum Rule Phys. Rev. D9 (1974) 1 st moment 12/7/2010 2
Nucleon Spin Naive quark parton model + relativistic corrections ~ 0.75 the rest is given by orbital momentum L ½= ½ + G + L q + L g quark gluon orbital momenta QCD; Ellis - Jaffe, SU(3) assuming s =0 ~ Alain Magnon12/7/2010
Early measurements of (1) SLAC with polarized e - E e- = 16 and 22 GeV (1976 – 1983) large, “as expected” g1pg1p x Bj SLAC SLAC Compatible with =0.6 V.W.Hughes 4 Alain Magnon12/7/2010 Phys. Rev. Lett. 51 (1983) 1135
Early measurements of (2) CERN with polarized + E. Gabathuler ( ) E. Gabathuler 5 Alain Magnon12/7/2010
Early measurements of (2) CERN E = 100, 120 and 200 GeV ( ) Access lower x 6 Alain Magnon 12/7/2010 Phys.. Lett. B206 (1988) 364
∫g 1 p x Bj x Bj g 1 p Ellis-Jaffe =0.60 EMC CERN ( ) → = 0.12 ± 0.17 → ” Spin crisis ’’ Early measurements of (2) 7 Alain Magnon 12/7/2010
Private conversation (~ end 1989) with B.Jaffe: “I have practiced QCD for so many years… our Sum Rule cannot be that wrong” 8 Alain Magnon12/7/2010
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 P Polarized protons and deuterons to measure also the Polarized protons and deuterons to measure also the neutron and verify the Bjorken Sum Rule 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 Magnon12/7/2010
JINR/Dubna = /7/2010Alain Magnon SMC =162
The CERN Beam Momentum Station Beam Definition Forward Spectrometer Beam polarimeter 12/7/ Alain Magnon DT67 DT67 -detection Polarised target target JINR/Dubna
The Polarised Target The CERN Few field uniformity Frequent spin rotation Transverse polarisation 12 12/7/2010Alain Magnon
~ 5 years of data SMC ~25% then 13 12/7/2010Alain Magnon
“ intervention by Y.Kisselev on the regulator circuit It was found - “ intervention by Y.Kisselev on the regulator circuit of the HV supply of the wave source” of the HV supply of the wave source” - that a significant increase in deuteron polarization is obtained by modulating rapidly the polarizing wave frequency over a range of ~30 MHz F+F+ F-F- No FM With FM Enhanced deuteron SMC /7/2010Alain Magnon
P D is by ~1.7 No FM With FM 13 May 1995 We reached 100% STAT to 1/(P D N 1/2 ) Enhanced deuteron SMC 15 12/7/2010Alain Magnon
- Measurement of the Spin-dependent Structure Function g1(x) of the Deuteron Phys. Lett. B 302 (1993) Measurement of the Polarization of a High Energy Muon Beam Nucl. Instr. and Meth. A 343 (1994) Combined analysis of world data on nucleon spin structure functions Phys. Lett. B 320 (1994) Measurement of the Deuteron Polarization in a Large Target Nucl. Instr. and Meth. A 349 (1994) Measurement of the Spin-dependent Structure Function g1(x) of the Proton Phys. Lett. B 329 (1994) Spin Asymmetry in Muon-Proton Deep Inelastic Scattering on a Transversely- Polarized Target Phys. Lett. B 336 (1994) A New Measurement of the Spin-dependent Structure Function g1(x) of the Deuteron Phys. Lett. B 357 (1995) Proceedings of Seventh International Workshop on Polarized Target Materials and Techniques Nucl. Instr. and Meth. A 356 (1995) No. 1 SMC publications (1) 16 12/7/2010
- Large Enhancement of Nuclear Polarization with Frequency Modulated Microwaves Nucl. Instr. and Meth. A 372 (1996) 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) Spin structure of the proton from polarized inclusive deep-inelastic scattering Phys. Rev. D56 (1997) A Line-shape Analysis for Spin-1 NMR Signals Nucl. Instr. and Meth. A 398 (1997) 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 SMC publications (2) 17 12/7/2010
- Spin Asymmetries A1 and structure functions g1 of the proton and the deuteron from polarized high energy muon scattering deuteron from polarized high energy muon scattering Phys. Rev. D58 (1998) Phys. Rev. D58 (1998) A next-to-leading order QCD analysis of the spin structure function g1 Phys. Rev. D58 (1998) Phys. Rev. D58 (1998) A large streamer chamber muon tracking detector in a high-flux fixed-target application Nucl. Instr. and Meth. A 435 (1999) 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) , Erratum-ibid.D62 (2000) 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, (2004) SMC publications (3) Final results, also using hadron-tagging at low x Bj < In total 23 SMC Publications 12/7/2010
Conclusions from SMC Q 0 2 = 10 GeV 1 p 1 d 1 p - 1 n SMC 0.120± ± ±0.023 Ellis/Jaffe 0.170± ±0.004 Bjorken 0.187± Phys. Rev. D58 (1998) Ellis/Jaffe Sum Rule Sum Rule NOT verified NOT verified Bjorken Sum Rule Sum Rule IS verified IS verified 19 Alain Magnon12/7/2010
a 0 ~ 0.3 GG Conclusions from SMC 20 12/7/2010Alain Magnon = 0.6 Need to get G -- HERMES COMPASS COMPASS RHIC RHIC --COMPASS-II (GPDs, DY & Primakoff) G~2