Determining Strangeness Quark Spin in Neutrino-Nucleon Scattering
at J-PARC
T.-A. Shibata (Tokyo Tech) in collaboration with N. Saito (Kyoto Univ) andY. Miyachi (Tokyo Tech)
Aug 25, 2004
NP04, KEK
for the ‘Strangeness Spin in Neutrino Scattering’ Working Group http://www.nucl.phys.titech.ac.jp/~sspin
Aug 25, 2004 T.-A. Shibata, NP04-Neutrino 2
Contents:
1. Introduction
--- Strangeness Quark Spin and
the Proton Spin Problem
2. Strangeness Quark Spin in Neutrino Scattering
3. Measurements
4. Conclusions
s
Aug 25, 2004 T.-A. Shibata, NP04-Neutrino 3
1. Introduction
u, d, and s Quark Spin in the Nucleon:Worldwide studies with accelerators
1.1 EMC experiment at CERN (1988) J. Ashman et al. Phys. Lett. B206 (1988) 364, Nucl. Phys. B328 (1989) 1
sdu
These papers obtained rather large number of citations in accelerator-based particle physics experiments ≈ 1200
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Quark Spin in the Proton
12 ± 9± 14 % 20 – 30 % of Proton Spin
2
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p
Proton Spin Problem
Aug 25, 2004 T.-A. Shibata, NP04-Neutrino 4
CERN EMC, SMC, COMPASS mu 160 GeV pol p,d DISDESY-HERA HERMES e 28 GeV pol p,d DISSLAC e 50 GeV pol 3He, p,d DISJLAb Hall A e 6 GeV pol 3He DIS Hall B e 6 GeV pol p,d Resonance Reg. Hall C e 6 GeV pol p,d Resonance Reg.
MIT/Bates SAMPLE e 0.2 GeV p,d Elastic Scatt. PVJLAB G0 e 6 GeV p,d Elastic Scatt. PVJLAB HAPPEX e 6 GeV p,d Elastic Scatt. PVMainz-MAMI e 0.88 GeV p,d Elastic Scatt. PVBNL E734 nu 1.3 GeV p Elastic Scatt. NC
BNL-RHIC PHENIX p+p 100 or 250 GeV gluon spin, sea quark STAR p+p 100 or 250 GeV gluon spin, sea quark
KEK B-factory BELLE e + e, 8 on 3.5 GeV fragmentation function
Collider Experiments:
Fixed Target Experiments:
Experiments on the Proton Spin and related measurements
Aug 25, 2004 T.-A. Shibata, NP04-Neutrino 5
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Aug 25, 2004 T.-A. Shibata, NP04-Neutrino 6
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Aug 25, 2004 T.-A. Shibata, NP04-Neutrino 7
Spin of the Proton
Sum of Spins of u u d Quarks = Spin of Proton
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Aug 25, 2004 T.-A. Shibata, NP04-Neutrino 8
Impact of s Measurement
• Spin Flavor Structure of the Proton – Beyond Flavor SU(3) assumption
• Neutron EDM – Neutron-EDM predicted
using q-EDM and q
• Dark Matter – Better determination of Dark-Matter reaction
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Aug 25, 2004 T.-A. Shibata, NP04-Neutrino 9
Neutrino-nucleon elastic scattering cross sectionfrom viewpoint of strange quark spin in the proton
L.A. Ahrens et al., Phys. Rev. D35 (1987) 785,G.T. Garvey et al., Phys. Rev. C48 (1993) 761 BNL734 experiment with Neutrino beam from AGS on proton, (mean energy 1.3 GeV) , (1.2 GeV) 0.5 E19 POT, 2.5E19 POT elastic scattering axial vector dipole mass needs to be determined.
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G.T. Garvey et al., Prog. Part. Nucl. Phys. 34 (1995) 245. Neutral current neutrino-proton and -neutron scattering cross section Strange form factors. Axial vector form factor 0.1 – 0.25 GeV , + p, + n elastic cross sections LSND at LAMPF
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Aug 25, 2004 T.-A. Shibata, NP04-Neutrino 10
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How to measure:
for
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Aug 25, 2004 T.-A. Shibata, NP04-Neutrino 11
:only beam
proton (LiqScintillator subtraction)
nuclear target • corrections for nuclear effects• high statistics
beam:
:beamsand cross section difference linear in G
sensitive to both G and G2
target:
• clear interpretation of G
Aug 25, 2004 T.-A. Shibata, NP04-Neutrino 12
N Elastic Scattering Exp at J-PARC evaluation by Saito
• On-axis at near detector hall of T2K• LiqScintillator with different H/C mixture for pure pr
oton signal (subtraction method)– e.g Bicron BC510A (H/C=1.212) and BC-533 (H/C=1.96)– Pure Carbon can be extracted for A cross section
– e.g. 5x5x5m3 • 1.0E21 POT possible in one year (130 days)
– 30 times BNL-E734– and beams
Conditions:
Aug 25, 2004 T.-A. Shibata, NP04-Neutrino 13
Sensitivity for s Conditions:
– Similar Detection Efficiency to E734:
• 7.6% for neutrino-N elastic• 5.4% for anti-neutrino-N elastic
– with lower Q2 cut-off : 0.1 GeV2
• Achievable with more uniform detector
– 25 times more statistics but pure proton only 1/6
• Factor 2 reduction in statistical error – Systematic control improvements
to ~5% • E734, 7.6% dominated by Beam
Flux and Nuclear Effects • Possible to remove Nuclear Effects
which could be larger in lower Q2 region
Aug 25, 2004 T.-A. Shibata, NP04-Neutrino 14
Comparison with BNL-E734
• If s is the only parameter to be determined– E734: – J-PARC:
• If s and MA are both free parameters – E734: – J-PARC: – N.B. other analysis of E734
provided better precision:
08.010.0 s03.010.0 s
27.010.0 s12.010.0 s
Aug 25, 2004 T.-A. Shibata, NP04-Neutrino 15
Conclusions
is strangeness quark spin in the proton
Physics with proton spin problem, neutron EDM, dark matter
‘Proton spin problem’ is an important subject for particle physics and is studied worldwide. Strange quark has been suggested to be negatively polarized but need closer examination
Neutrino scattering provides while from DIS requires extrapolation to unmeasured region
Neutrino beam at J-PARC provides a unique possibility to measure through axial vector form factor with neutral current elastic scattering cross section
The case of proton target (LiqScintillator subtraction) was estimated
Design and detector tests are planned
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