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, pn 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 as

pect 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 pn inelastic scattering

Purpose of the p scattering experiment Measure the differential cross section from ~10,000 scattering event

s for these channels. p elastic scattering p elastic scattering pn inelastic scattering

Reliable data enables us to discriminate the theoretical models of BB interaction.

Quark cluster model

Nijmegen model

Large cross section due tothe large hard core

Simulation

Assumed flat distribution

Purpose of the p scattering experiment Measure the differential cross section from ~10,000 scattering event

s for these channels. p elastic scattering p elastic scattering pn 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

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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.

p

: beam momentum (spectrometer)

pn

pkinE )(

: proton direction (tracker)

: proton Ekin (calorimeter)

n

: 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 : 2x107/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

p

: beam momentum (spectrometer)

pn

pkinE )(

: proton direction (tracker)

: proton Ekin (calorimeter)

n

: 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 easierNo proton decay channelLonger 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 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

p case

Scattering event

Identification of p scattering

Background suppression Closest distance cut at reaction vertex Other reaction assumption

p scattering pn inelastic reaction npnp scattering reaction

If the assumption is correct,such event show the peak at E = 0for each kinematics

p assumption n assumption np assumption

Background suppression Closest distance cut at reaction vertex Other reaction assumption

p scattering pn inelastic reaction npnp scattering reaction

If the assumption is correct,such event show the peak at E = 0for each kinematics

After the background suppression

E (MeV)d2 /d

dE

(m

b/sr

/MeV

)

Purpose of the p scattering experiment Measure the differential cross section from ~10,000 scattering event

s for these channels. p elastic scattering p elastic scattering pn inelastic scattering

Reliable data enables us to discriminate the theoretical models of BB interaction.

Yield Estimation

45/spill6.5105/spill

Summary p scattering experiment is a powerful method to investigate BB inte

raction 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, pn reaction data enable us to test the system

atic 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 sc

attering Experimental method is feasible from the simulation study. We try to measure differential cross sections with 100 times larger st

atistics.

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