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

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

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

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. (27) (10*)(8s)(10)(8a) (1) Lattice QCD, T. Inoue et al. arXiv:1007:3559 [hep-lat]   p (S=1)   p (S=0, T=0)   p (T=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 Same with NN(I=1,S=0)   p (S=1) (10)

 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

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. Quark cluster model Nijmegen model Large cross section due to the large hard core Simulation Assumed flat distribution

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.

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

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.

Experimental Idea for high statistics YN scattering Measurements Background suppression : np scattering etc. :  beam momentum (spectrometer) : proton direction (tracker) : proton Ekin (calorimeter) :  direction (tracker) Scattering angle Consistency check 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. LH2 target High intensity  Vertex fiber tracker and trigger

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 : 2x10 7 /spill Fast and stable beam tracker  Fiber tracker LH2 target Length : 30 cm   beam : 93/spill   beam : 370/spill 

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

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.

  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.

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

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   p assumption  n assumption np 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 After the background suppression  E (MeV) d 2  /d  dE (mb/sr/MeV)

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.

Yield Estimation 45/spill 6.5  10 5 /spill

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 LH 2 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.

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