J-PARC でのシグマ陽子散乱実験の提案

1. J-PARCでのシグマ陽子散乱実験の提案 Koji Miwa Tohoku Univ.

2. Contents • Physics Motivation of YN scattering • Understanding Baryon-Baryon interaction • SU(3) framework • Nature of hard core • Our experimental goal • Differential cross section • p scattering • p scattering, pn reaction • Experimental method • High intensity beam handling • Kinematical reconstruction using a LH2 target

3. Potential of nuclear force triplet singlet Baryon Baryon interaction • Understanding of nuclear force • Attractive force by boson exchange • Origin of hard core ? • Understanding of nuclear force from quark picture • NN interaction is just a one aspect of Baryon Baryon interaction

4. (10*) (10) (8a) (8s) (27) (1) p (S=0, T=0) p (S=1) p (T=0) Baryon Baryon interaction • Extended BB interaction to flavor SU(3) • 6 independent forces • Interaction of the new multiplet • a quite different from NN force and quite interesting feature, especially at hard core region. Lattice QCD, T. Inoue et al. arXiv:1007:3559 [hep-lat]

5. p (S=1) Same with NN(I=1,S=0) p scattering experiment • Hyperon proton scattering experiment • Derive information of each channel separately. • 6 independent force • +p channel : key channel for the hard core • Large hard core is expected. • Quark model can naturally derive from Pauli principle • Boson exchange model use a phenomenological core (10)

6. p scattering experiment • Hyperon proton scattering experiment • Derive information of each channel separately. • 6 independent force • +p channel : key channel for the hard core • Large hard core is expected. • Quark model can naturally derive from Pauli principle • Boson exchange model use a phenomenological core • Test of theoretical framework extended to SU(3) symmetry. • Precise information is limited to N interaction • Consistency for all channels • p elastic scattering • pn inelastic scattering

7. Nijmegen model Quark cluster model Large cross section due to the large hard core Purpose of the p scattering experiment • Measure the differential cross section from ~10,000 scattering events for these channels. • p elastic scattering • p elastic scattering • pn inelastic scattering • Reliable data enables us to discriminate the theoretical models of BB interaction. Assumed flat distribution Simulation

8. Purpose of the p scattering experiment • Measure the differential cross section from ~10,000 scattering events for these channels. • p elastic scattering • p elastic scattering • pn inelastic scattering • Reliable data enables us to discriminate the theoretical models of BB interaction.

9. Higher beam momentum Old bubble chamber data Energy dependence of d/d • Energy dependence of S-wave • Inner part of interaction • d/d(=90) contribution from S-wave Sensitivity of the proposed experiment R. Jastrow. Phys.Rev.81(1950) 636

10. Experimental Idea for high statistics YN scattering • From experience from past experiment…… • High rate meson beam should be handled to produce many  beam • LH2 target should be used as  production and p scattering target • The quality of data taking trigger should be sophisticated to select  production or p scattering event.

11. :  beam momentum (spectrometer) : proton direction (tracker) Consistency check Scattering angle : proton Ekin (calorimeter) :  direction (tracker) Background suppression : np scattering etc. Experimental Idea for high statistics YN scattering • From experience from past experiment…… • High rate meson beam should be handled to produce many  beam • LH2 target should be used as  production and p scattering target • The quality of data taking trigger should be sophisticated to select  production or p scattering event. Measurements LH2 target High intensity  Vertex fiber tracker and trigger

12.  Experimental setup at K1.8 •  beam tagging • K1.8 beam line spectrometer + SKS spectrometer •  beam • p (=245 b) • Acceptance 4.5% • + beam • +p+ (=523 b) • Acceptance 7% •  beam rate •  beam rate : 2x107/spill • Fast and stable beam tracker • Fiber tracker • LH2 target Length : 30 cm •  beam : 93/spill •  beam : 370/spill

13. :  beam momentum (spectrometer) : proton direction (tracker) Consistency check Scattering angle : proton Ekin (calorimeter) :  direction (tracker) Detector for scattered proton • Acceptance • 35 % • Angular resolution • 1.3 degree • Reconstructed energy resolution •  = 3.2 MeV • PID • E-E relation •  measurement • Vertex Fiber tracker • Tracking • Accidental background suppression • Trigger possibility • Cylindrical chamber • Tracking with fiber • Calorimeter • Measure energy

14. Simulation of p reaction Experimentally easier No proton decay channel Longer life time For p reaction, the same technique is applied. We must be careful much more to background.

15. p reaction with background process • These events has all final state particle of proton and . • We have to separate these events using kinemtaical information Conversion process becomes Background for p scattering.

16. p case Scattering event Consistency of kinematics Identification of p scattering • Kinematics check • Ecalulate (determined from  assuming p scattering) • Emeasure (measured by Calorimeter) • E = Emeasure-Ecalculate • E should be 0 for p event. • Due to the kinematically overlapped region, there is a contamination of background around E~0

17. np assumption n assumption p assumption Background suppression • Closest distance cut at reaction vertex • Other reaction assumption • p scattering • pn inelastic reaction • npnp scattering reaction If the assumption is correct, such event show the peak at E = 0 for each kinematics

18. d2/ddE (mb/sr/MeV) E (MeV) Background suppression • Closest distance cut at reaction vertex • Other reaction assumption • p scattering • pn inelastic reaction • npnp scattering reaction If the assumption is correct, such event show the peak at E = 0 for each kinematics After the background suppression

19. Purpose of the p scattering experiment • Measure the differential cross section from ~10,000 scattering events for these channels. • p elastic scattering • p elastic scattering • pn inelastic scattering • Reliable data enables us to discriminate the theoretical models of BB interaction.

20. Yield Estimation 45/spill 6.5105/spill

21. Summary • p scattering experiment is a powerful method to investigate BB interaction and the nature of interaction from quark picture. • p channel is the key reaction to understand the nature of the repulsion at the hard core. • p elastic scattering, pn reaction data enable us to test the systematic study of YN interaction • Stability of  particle inside the nucleus. • We are going to propose a p scattering experiment with new experimental method • High intensity  beam • LH2 target • Surrounding detector system which also makes possible to trigger YN scattering • Experimental method is feasible from the simulation study. • We try to measure differential cross sections with 100 times larger statistics.

22. Multichannel fiber detector • Fiber vertex detector • Beam line tracker Fiber + PPD readout • SPIROC-A board with KEK and LAL • 32 channel operation of PPD • Serial Analogue out + Parallel Logic out