Gamma-ray spectroscopyof light hypernuclei

の Simulation

Proposed DAY-1 experiment

　　　　　 (1) Spin-flip B(M1) measurement and g in a nucleus 7

Li : Least ambiguities exist and most reliable.

(2) Further N interaction study from p-shell hypernuclei 10

B and 11B:

(3) Radial dependence of N interaction from sd-shell hypernuclei 19

F : Easiest in sd-shell

(4) Charge symmetry breaking in N interaction and

spin-flip property in hypernuclear production

4He : Largest CSB is suggested but previous data is suspicious.

Easiest to observe a spin-flip state

Confirmation of N spin-dependence NN coupling

DAY1 program: Feasible even with low intensity beam (~2A)

(K-,- ) at pK = 1.5 GeV/c

Inconsistency exists.Experimental data not enough.Few-body approach as well as shell model is possible.

Best K- beam momentum

pK = 1.1 GeV/c : K1.1 + “SKS” (ideal) pK = 1.5 GeV/c : K1.8 + SKS (realistic)

Both spin-flip and nonflip states should be produced. -> pK = 1.1 or 1.5 GeV/c

K- + n -> + -

High K/ ratio to minimize radiation damage to Ge detectors -> Double-stage separation. K1.8BR is not good.

1.5 GeV/c

Beam and Setup

Beamline: K1.8 0.5x106 K-/spill at 1.5 GeV/c (9A) K/ >> 1

Spectrometer: SKS (modified) p ~ 4 MeV (FWHM) ~ 110 msr

Hyperball-J ~ 7% at 1 MeV

-

K1.8

K-

　 SDC3,4: Large-size (2.0mx0.8m), fine cell (1~2cm)

　 SMF: Muon filter to suppress K- ->-

　 SP0: Veto counters to reject K- -> -0To be constructed

Ge crystalPWO suppressor

Gecoolingsystem

K- beam

target

Single (r.e.~70%) x 30-40 peak efficiency ~ 7% at 1MeV 　 ( x3 of Hyperball)　 Mechanical cooling (under development) -- Lower temp. for less radiation damage -- save space for flexible arrangement

PWO background suppression counters replaced from BGO for higher rate

Hyperball-J

+ Waveform readout (under deveopment) => Rate limit ~2x107 particles /s (x5 of Hyperball) => Yield: x 15 for single x 45 for

Grant: ~ 3.3Myen, 2005-2009 　“Gamma spectroscopy of

strange baryon multi-body systems”科研費特定領域 ( 田村 )

Lower half

Photo-peak efficiency

SimulationSimulation

J-PARC K1.8 Beam Line

BDC1,2 BDC3,4 SDC1,2 BDC3,4

BH1 BH2 SFV SMFTOF

BAC SAC

SP0

Ge+PWO

Beam line part SKS part

Hyperball-J

Set up -SKS Minus-

Acceptance of SKS Minus

Acceptance Check by Present SKS

Next Simulation

Beam direction Target Point

Momentum resolution

To make formatter　　　　　　↓Analyzing by SKS analyzer・・・・

Trigger Rate and Background Study