Transcript Slide 1

Spin physics at the
Spin Muon Collaboration
A. Magnon
(CEA-Saclay/IRFU & COMPASS)
Spin structure function g1p(n)
Ellis Jaffe
Sum Rule
Phys. Rev. D9
(1974)
1st moment
1
p (n)
1

 g1
p ( n)
( xBj )dxBj 
1
2
0
aq
 
 qq
2
e
 q aq
q u ,d , s
Flavor singlet
a0  au  ad  as    n f

 (Q 2 )
s
2
 G (Q )
2
Flavor non singlets
a3  au  ad

G
| A
6 G
1
a8  au  ad  2as
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V

NS
| C
1
Bjorken Sum Rule
Phys. Rev. 148 (1966)
NS
(3F  D)  C
1
3
1
2
Nucleon Spin
½= ½ + G + Lq + Lg
quark
gluon
orbital momenta
 Naive quark parton model + relativistic corrections
 ~ 0.75 the rest is given by orbital momentum
L
 QCD; Ellis - Jaffe, SU(3) assuming s =0
 ~ 0.60
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Early measurements of 
(1)
Phys. Rev. Lett. 51 (1983) 1135
SLAC
g1p
V.W.Hughes
Compatible with
=0.6
xBj
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SLAC with polarized eEe- = 16 and 22 GeV
(1976 – 1983)
 large, “as expected”
Alain Magnon
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Early measurements of 
(2)
EMC @ CERN with polarized m+
(1985-1986) E. Gabathuler
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Alain Magnon
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Early measurements of 
(2)
EMC @ CERN Em = 100, 120 and 200 GeV
Phys.. Lett. B206 (1988) 364 (1987-88)
Access lower x
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Early measurements of 
(2)
EMC @ CERN (1987-88)
 = 0.12 ± 0.17 → ” Spin crisis ’’
Ellis-Jaffe =0.60
EMC
∫g1p
xBjg1p
xBj
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Alain Magnon
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Private conversation (~ end 1989) with B.Jaffe:
“I have practiced QCD for so many years…
our Sum Rule cannot be that wrong”
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Alain Magnon
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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)
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 SMC =162
 JINR/Dubna = 14
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The SMC @ CERN
Beam Momentum Station
m Beam polarimeter
Beam Definition
DT67
m-detection
Forward Spectrometer
JINR/Dubna
Polarised
target
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The SMC @ CERN
The Polarised Target
Few 10-5 field uniformity
Frequent spin rotation
Transverse polarisation
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~ 5 years of data taking @ SMC
~25% then
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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
0.01
With FM
With FM
No FM
F-
F+
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Enhanced deuteron polarization @ SMC
13 May 1995
We reached 100%
With FM
PD is  by ~1.7
No FM
sSTAT

to
1/(PDN1/2)
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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 TransverselyPolarized 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
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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
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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
Final results, also
using hadron-tagging
at low xBj < 0.02
- 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)
In total 23 SMC Publications
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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
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Alain Magnon
Bjorken
Sum Rule
IS verified
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Conclusions from SMC
Need to get G
-HERMES
COMPASS
 = 0.6
a0 ~ 0.3
RHIC
--
G
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G~2
Alain Magnon
COMPASS-II
(GPDs, DY
& Primakoff)
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