LEPS2 detector Yoshikazu Maeda RCNP For LEPS collaboration LEPS2 project Higher intensity and energy photon beam General purposed detector Detector design based on E949 detector Nagoya 08/12/7
Key words : t-channel process 1. Forward angle measurement γ Flavor selection M M 2. Polarized photon N Parity filter M B M B 3. Strangeness M 4. Decay particles Large acceptance
Requirement Detection of the multi-charged particles and neutral particles Reaction (MM) P/P~1% for 1GeV/c kaon at forward θ + π/κ separation. Decay (IM) Low momentum down to 01GeV/c 0.1GeV/c Wide polar angle, smooth and full acceptance p g, p for azimuthal direction Coplanarity Decay distribution Polarization measurement
New Beamline Project at SPring-8(BL31ID) Backward Compton Scattering SPring-8 SR ring 8 GeV electron BL31ID: Better divergence beam collimated photon beam BL31ID <σ x >=14 µrad Recoil electron (Tagging) Laser or re-injected X-ray Inside building High intensity Multi (ex. 4) laser injection & Laser beam shaping ~10 7 photons/s LEPS ~10 6 High energy Re-injection of X-ray Eγ < 7.5GeV 150m 30 m Outside building Experimental hutch
Experimental building for LEPS2 E949 at BNL kaon
BNL-E949 detector Designed for K + π + νν Solenoid 1 T Inner volume 2.22x2.96 m Range Stack counter Plastic scintillators 19 layers Energy and Range Barrel Photon detector Plastic & lead sandwich detector t 14.3X 0 Energy and position
Setup 2.22 m
Tracking system Side way tracker (TPC) R = 500 mm (24-26 layer), σ rφ =150um, σ z =2mm, 90 mm Forward MWDC chamber(450mm) 4 He+Ethane (X/X 0 = 1.1x10-3 ) 6 plane (x,x, u(45) u (-45), y y ) σ xy =150um, y Barrel tracker Cathode strip + Anode wire σ rφ = 250um, σ z = 2-3 mm Sensor 68x53mm 2 (Micron) ->896x6 channel(42chip) BELLE SVD2 SSD (Cylindrical+ i l+ Disk) Double side strip sensor σ=35um, Z< 1 mm at θ>20 0
P/P at forward region 2 o <θ< 17 o Vertex + Fd MWDC No SW tracker At 10 degree P/P = 1.3% (He4 gas) 1.9% (Air) θ > 17 o MS effect in SW tracker TPC Ar/CH 4 or Ne/CH 4
Momentum dep. of P/P 17 o
P/P at SW region (θ>30 o ) Ne 90%)+Methan(10%) IM [MeV/c 2 ] Λ pπ - 1.3 Λ pk - 22 2.2 K 0 π + π 2.6 θ + pk 0 3.0-3.6
PID for side region TPC E/E~5% Pion Kaon Proton Range counter K + π + π 0 and K + µ+ν(γ) (π/µ separation) 19 layers x19mm thick plastic For π/κ separation P< 1 GeV/c 15 layers (55 cm-89.6cm) High resolution TOF counter Stopped particle Barrel γ Peak EFF ~ 0.8(0.6) S/N~0.02(π/K=1) Non stopped due to Nucl. reaction Tracker
π/k sep of 6σ at 1.5 GeV/c T=50 psec Disk type DIRC Light correction from inner part No dead space T.Kamae et al, Nucl, Instr A382(1996)430-440 Quartz disk Aerogel (n<1.03) Chiba univ.
Magnet 2.22 m 50 45 40 35 30 25 20 15 10 Detection of Neutron in RS Pn < 0.8 GeV/c TOF σ=500ps) ) Path : straight line. -> Beta -1 = 0.1 Pn/Pn = Beta/(1-Beta 2 ) x0.1 Θ = R/L 2 Z(=7.5cm) φ = 4 o (2π/24/12 1/2 ) m 2.96 TPC Helium Bag EFF( E>7MeV ee )=15-20%
Hyperon production at Eγ=2.4 GeV Θ Κ < 15 degree M=40 MeV/c 2 Strangeness tagging Θ Κ > 15 degree M=16 MeV/c 2 + γ + p K + Λ(1116 ) p π + γ + p K + Σ(1192) Λ γ M=2 MeV/c 2 Coplanerity Cut p π φ Κ+ φ Λ [deg]
Penta-quark Θ + M(K 0 )=2.4 MeV/c 2 Strangeness tagging γ + n K + Θ + CDC and TPC MC effect on LH2 targett p Κ 0 IM(π+,π ) [GeV/c2 ] π + π Invariant Mass measurement M(Θ + )=3.5 MeV/c 2 IM(π +,π,p) [GeV/c 2 ]
γp Λ(1405) ( ) π + π K 0 π + ( ) γ + p Κ + + Λ(1405) Σ + π n n π + π + Missing mass resolution for Λ(1405) 8 MeV/c 2 M [GeV/c 2 ]
Summary BNL-E949 is considered to be used as a large acceptance detector at SPring8/LEPS2. The detector was designed based on E949 solenoid only as a first step. SSD and Planer DC for forward,and TPC for large angle are considered for tracking system. P/P < 1.3% at θ lab > 10 degree 1.5 GeV/c kaon RS, TOF and DIRC counter are discussed for PID. R&D have to be made to have the realistic detector design.
Back up
γd Λ(1520)Θ + γd Λ(1520) ( ) Θ + γd Λ(1520) Θ + γd Λ(1520) ( ) Θ + K - p K - p K + n K - p K s p Missing Mass + Kinematical fit Invariant Mass M(Θ + )=17 MeV/c 2 M(Θ + )=10 MeV/c 2 M(Θ + )=3 MeV/c 2
Target
Barrel photon detector Fvis=0.3 Barrel photon detector 14.3 radiation length Attenuation length 90 cm speed of light 17.44 cm /ns 16,18,20,21 layers E E = 1.5 E(MeV( ) By Tsunemi Eg. 15 MeV@100MeV Θ =? φ = 2 o (2π/48/12 1/2 )
Basic concept for tracking system σ P σ P P T rϕ T = 2 T 0.3 BL 720 N + 4 Forward part Θ< 20 deg SSD and Planer DC chamber Side part 20 < Θ < 90 deg TPC or CDC B=1T 0.5m 1.8 m σ =150um, N=13, P=1 GeV/c P/P = 0.5 % at Θ=10(deg) N=26, P=0.5 05 GeV/c P/P = 0.5 % at Θ=90(deg)
Multiple scattering effect for forward charged particle σ Pt P t P t = 0.016 0.3B β sinθ L X 0 L=1.8 m X/X 0 10-3 Air 6.0 Ar 9.1 He4 0.3 Setup SSD + TPC(Ar) + planer DC(He4) SSD + CDC(He4)
GAS mixture for TPC Experiment Gas mixture Proportion Gas ρ X0 X0 n mp [g/ l] [g/cm2] [m] [1/cm] ALEPH Ar/CH4 91/9 He 0.1785 94.32 5280 2.7 NA49 VTPC Ne/CO2 90/10 Ne 0.89990 28.94 322 16 NA49 MTPC Ar/CO2/CH4 90/5/5 Ar 1.784 19.55 110 38 STAR Ar/CH4 (P10) 90/10 CH4 0.717 46.22 645 30 ALICE Ne/CO2 90/10 CO2 1.977 36.2 183 50 TESLA Ar/CO2/CH4 93/2/5 C2H6 1.356 45.47 335 59 TDR of PANDA
MWDC 6 wire plane x,x, u(45) u (-45), y y Z Window 6x Wire plane 7xCathode -45 45 60 mm Cell structure t 10mm 10mm
Material for MWDC GAS X0 [m] X[mm] X/X0x10-4 He+Ethane(50%) 640 60 0.94 Ar +IsoB(30%) 127 60 4.72 Window [cm] [um] Mylar 28.7 2x50 3.48 Cathode plane [cm] [um] Mylar 28.7 7x10 2.44 Al 8.9 7x3 2.36 Cathode wire [cm] [um] CuBe(φ50um) 211 2.11 687 6.87 326 3.26 Al(125um) 8.9 43 4.83 Anode wire W(30um) 0.35 0.50 1.41 Field wire CuBe(φ50um) 2.11 1.37 0.65 Al(125um) 8.9 8.5 0.96 Cathode plane CuBe for FW ΣX/X0= 1.1x10-3 (He) 1.5x10-3 (Ar) ->DP/P ~ 1 %
PID (Chrenkov) 30mrad (p K separation) at 2 GeV
Θ + γ θ c.m. d Λ(1520)
15 layers scinti π 03 0.3 GeV/c K 0.5 GeV/c P 0.8 GeV/c 45 degree 2.96 m Magnet 2.2222 m TPC Helium Bag 50 45 40 35 30 25 20 15 10 E [M MeV] MM 2 [GeV V/c 2 ] 2 π Κ p Momentum GeV/c 2
Mass spectra (p<0.3 GeV/c) π + π K + P K - MM 2 [GeV/c 2 ] 2 MM 2 [GeV/c 2 ] 2
Peak efficiency and BG(π) Peak efficiency 45 degree π contamination in Kaon cut Νπ/Νκ (1:1) K + p π + Κ
0.6<P<1.0 GeV/c Positive 0.625 0.665 0.71 Negative 0.755 0.800 0.845 0.890 0.935 0.980 P.E(K + ) ~0.8 π and p BG~ 0.02-0.1, 0.03-0.08 P.E(K - ) ~0.5 0.6 0.6
γp Κ + Λ Κ+ π p Cos Θ cm Θ lab Momentum [GeV/c] Momentum [GeV/c] Momentum [GeV/c]
γ η N γ(η) 32 MeV(σ M )