Spin physics at the Spin Muon Collaboration

A. Magnon (CEA-Saclay/IRFU & COMPASS)

NSsdu

NSdu

QQ

nsdu

qa

qsduqq

npnp

Caaaa

Caaa

aaaa

qq

aedxxg

s

BjBj

f

1)(

3

1

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6

1

)(2

,,

221)()(

1

2

)(

8

3

2)

2(

0

1

0

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D3F

G

G

G

V

A

(

Spin structure function g1p(n)

Flavor singlet

Flavor non singlets

Bjorken Sum RulePhys. Rev. 148 (1966)

Ellis Jaffe Sum Rule Phys. Rev. D9 (1974)

1st moment

12/7/2010 2

Nucleon Spin

Naive quark parton model + relativistic corrections

DS ~ 0.75 the rest is given by orbital momentum

L

½= ½DS + DG + Lq + Lg

quark gluon orbital momenta

QCD; Ellis - Jaffe, SU(3) assuming Ds =0

DS ~ 0.60

3Alain Magnon12/7/2010

Early measurements of DS (1)

SLAC with polarized e-

Ee- = 16 and 22 GeV

(1976 – 1983)

DS large, “as expected”

g1p

xBj

SLAC

Compatible with DS=0.6

V.W.Hughes

4Alain Magnon12/7/2010

Phys. Rev. Lett. 51 (1983) 1135

Early measurements of DS (2)

EMC @ CERN with polarized m+

(1985-1986) E. Gabathuler

5Alain Magnon12/7/2010

Early measurements of DS (2)EMC @ CERN Em = 100, 120 and 200 GeV (1987-88)

Access lower x

6Alain Magnon12/7/2010

Phys.. Lett. B206 (1988) 364

∫g1p

xBj

xBjg1p

Ellis-Jaffe DS=0.60EMC

EMC @ CERN (1987-88) DS = 0.12 ± 0.17 → ” Spin crisis ’’

Early measurements of DS (2)

7Alain Magnon12/7/2010

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

8Alain 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 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)

9Alain Magnon12/7/2010

S JINR/Dubna = 14

1012/7/2010 Alain Magnon

S SMC =162

The SMC @ CERNBeam Momentum Station

Beam Definition

Forward Spectrometer

m Beam polarimeter

12/7/2010 11Alain Magnon

DT67m-detection

Polarised target

JINR/Dubna

The Polarised Target

The SMC @ CERN

Few 10-5 field uniformityFrequent spin rotation Transverse polarisation

1212/7/2010 Alain Magnon

~ 5 years of data taking @ SMC

~25% then

1312/7/2010 Alain Magnon

It was found - “ intervention by Y.Kisselev on the regulator circuitof 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

F+ F-

No FM

With FMWith FM

Enhanced deuteron polarization @ SMC

0.01

1412/7/2010 Alain Magnon

PD is by ~1.7 No FM

With FM

13 May 1995We reached 100%

sSTAT

to

1/(PDN1/2)

Enhanced deuteron polarization @ SMC

1512/7/2010 Alain Magnon

- 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

SMC publications (1)

1612/7/2010

- 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

SMC publications (2)

1712/7/2010

- 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)

SMC publications (3)

Final results, alsousing hadron-taggingat low xBj < 0.02

18

In total 23 SMC Publications12/7/2010

Conclusions from SMC

------------------------------------------------------------ Q0

2 = 10 GeV2

------------------------------------------------------------ 1

p 1d 1

p- 1n

SMC 0.120±0.016 0.019±0.014 0.198±0.023 Ellis/Jaffe 0.170±0.004 0.071±0.004Bjorken 0.187±0.002------------------------------------------------------------

Phys. Rev. D58 (1998) 112002

Ellis/Jaffe Sum Rule NOT verified

Bjorken Sum Rule IS verified

19Alain Magnon12/7/2010

a0 ~ 0.3

DG

Conclusions from SMC

2012/7/2010 Alain Magnon

DS = 0.6Need to get DG -- HERMES COMPASS RHIC

--COMPASS-II(GPDs, DY& Primakoff)DG~2