JSP meeting on Sept. 10, 2003 Hyperball -- Hypernuclear γ spectroscopy at J-PARC -- H. Tamura Tohoku Univ. 1.Physics Subjects 2. Beam and Setup 3. Upgrade of Hyperball 4. Summary
1. Physics subjects of γ spectroscopy Systematic Study of High-Precision (2 keV) Hypernuclear Structure = “ Table of Hyper-Isotopes ” � YN interactions spin-spin: 7 Λ Li (KEK E419) Λ N : spin-dependent forces PRL 84 (2000) 5963 Λ N- Σ N / Λ NN forces LS: 9 Λ Be (BNL E930) PRL 84 (2002) 082501 charge symmetry breaking tensor: 16 Λ O (BNL E930) p-wave interaction Ukai, 12aSE Ξ N, ΛΛ interactions New method: Hyperfragments (KEK E509) � Impurity effects B(E2) -> shrinking effect B(E2): 7 Λ Li (KEK E419) PRL 86 (2001) 1982 Shrinkage of n-halo Change of cluster/shell structure � Nuclear medium effect B(M1) -> µ Λ inside a nucleus 11 Λ B (KEK E518) density / isospin dependence
“Day-one experiment” Beam intensity Letter Of Intent [ S = -1 ] Low (<1/10) Med (1/10~1/2) (1) Light Hypernuclei by (K - , π - γ ) p= 1.1 and 0.8 GeV/c High (>1/2) All targets of A<30 Detailed ( γγ 、 γπ/γγ corr., pol, B(E2)) for 12 Λ C, 20 Λ Ne, 28 Λ Si, … => Λ N spin-dep. and Λ N/ Σ N interactions, Impurity effect Λ Pb, ..) by (K - , π - γ ) (2) Medium and heavy Hypernuclei ( 89 Λ Y, 139 Λ La, 208 => p-wave Λ N interaction p=1.8, 1.1, 0.8 E1(p Λ ->s Λ ) (3) Hyperfragments by (K - stop , γγ) / (K - , γπ - ) p= 0.8--0.6 n-rich/ p-rich hypernuclei, A=8 => Impurity effect (Shrinkage of n-halo) (4) Mirror / n-rich Hypernuclei by (K - , π 0 γ ) p= 1.1 and 0.8 4 Λ H( 4 Λ He) , 12 Λ B( 12 Λ C), 16 Λ N( 16 Λ O) => Charge Sym. Break. ( π + , K + γ ) or (K - , π - γ ) p=1.1 (5) B(M1) by DSAM => µ Λ in nucleus 11 7 Λ B, Λ Li etc. (K - , π - γ weak) p= 1.1 or 0.8 (6) B(M1) by γ -weak 12 Λ C, heavier
Beam intensity Low (<1/10) Letter Of Intent [ S = -2 ] Med (1/10~1/2) High (>1/2) (7) Ξ atom by (K - , K + γ ) p= 1.8 GeV/c ・ => Ξ N interaction wide range of A (8) ΛΛ− nuclei by (K - , K + π - γ ) p=1.8 ・ => ΛΛ interaction several p-shell targets
“Day-one experiment” Beam intensity Letter Of Intent [ S = -1 ] Low (<1/10) Med (1/10~1/2) (1) Light Hypernuclei by (K - , π - γ ) High (>1/2) p= 1.1 and 0.8 GeV/c All targets of A<30 Detailed ( γγ 、 γπ/γγ corr., pol, B(E2)) for 12 Λ C, 20 Λ Ne, 28 Λ Si, … => Λ N spin-dep. and Λ N/ Σ N interactions, Impurity effect Λ Pb, ..) by (K - , π - γ ) (2) Medium and heavy Hypernuclei ( 89 Λ Y, 139 Λ La, 208 p=1.8, 1.1, 0.8 => p-wave Λ N interaction E1(p Λ ->s Λ ) (3) Hyperfragments by (K - stop , γγ) / (K - , γπ - ) p= 0.8--0.6 n-rich/ p-rich hypernuclei, A=8 => Impurity effect (Shrinkage of n-halo) (4) Mirror / n-rich Hypernuclei by (K - , π 0 γ ) p= 1.1 and 0.8 4 Λ H( 4 Λ He) , 12 Λ B( 12 Λ C), 16 Λ N( 16 Λ O) => Charge Sym. Break. ( π + , K + γ ) or (K - , π - γ ) p=1.1 (5) B(M1) by DSAM => µ Λ in nucleus 11 Λ B, 7 Λ Li etc. (K - , π - γ weak) p= 1.1 or 0.8 (6) B(M1) by γ -weak 12 Λ C, heavier
12 C ( π + ,K + ) 12 Λ C (1) Light hypernuclei SKS ∆ E~1.5 MeV(FWHM) --- example of 12 Λ C Simulation: K1.1, 10g/cm 2 , 120 hours a l Expected transitions c b g d k h o p f k e j n h i g j e c b l m f i d a
c γγ coincidence - ->1 1 - ) coinc. with a (2 1 k h and angular correlations j f 12 Λ C: simulation γγ coincidence spectrum - -> 2 1 - ) coinc. with c (1 2 h -> level scheme k θ πγ angular correlation -> spin assignment
(1) Light hypernuclei Impurity effect --- example of 20 Λ Ne : change of cluster structure shrinking effect considered (cluster model)
“Day-one experiment” Beam intensity Letter Of Intent [ S = -1 ] Low (<1/10) Med (1/10~1/2) (1) Light Hypernuclei by (K - , π - γ ) p= 1.1 and 0.8 GeV/c High (>1/2) All targets of A<30 Detailed ( γγ 、 γπ/γγ corr., pol, B(E2)) for 12 Λ C, 20 Λ Ne, 28 Λ Si, … => Λ N spin-dep. and Λ N/ Σ N interactions, Impurity effect Λ Pb, ..) by (K - , π - γ ) (2) Medium and heavy Hypernuclei ( 89 Λ Y, 139 Λ La, 208 => p-wave Λ N interaction p=1.8, 1.1, 0.8 E1(p Λ ->s Λ ) (3) Hyperfragments by (K - stop , γγ) / (K - , γπ - ) p= 0.8--0.6 n-rich/ p-rich hypernuclei, A=8 => Impurity effect (Shrinkage of n-halo) (4) Mirror / n-rich Hypernuclei by (K - , π 0 γ ) p= 1.1 and 0.8 4 Λ H( 4 Λ He) , 12 Λ B( 12 Λ C), 16 Λ N( 16 Λ O) => Charge Sym. Break. ( π + , K + γ ) or (K - , π - γ ) p=1.1 (5) B(M1) by DSAM => µ Λ in nucleus 11 7 Λ B, Λ Li etc. (K - , π - γ weak) p= 1.1 or 0.8 (6) B(M1) by γ -weak 12 Λ C, heavier
“Day-one experiment” Beam intensity Letter Of Intent [ S = -1 ] Low (<1/10) Med (1/10~1/2) (1) Light Hypernuclei by (K - , π - γ ) p= 1.1 and 0.8 GeV/c High (>1/2) All targets of A<30 Detailed ( γγ 、 γπ/γγ corr., pol, B(E2)) for 12 Λ C, 20 Λ Ne, 28 Λ Si, … => Λ N spin-dep. and Λ N/ Σ N interactions, Impurity effect Λ Pb, ..) by (K - , π - γ ) (2) Medium and heavy Hypernuclei ( 89 Λ Y, 139 Λ La, 208 => p-wave Λ N interaction p=1.8, 1.1, 0.8 E1(p Λ ->s Λ ) (3) Hyperfragments by (K - stop , γγ) / (K - , γπ - ) p= 0.8--0.6 n-rich/ p-rich hypernuclei, A=8 => Impurity effect (Shrinkage of n-halo) (4) Mirror / n-rich Hypernuclei by (K - , π 0 γ ) p= 1.1 and 0.8 4 Λ H( 4 Λ He) , 12 Λ B( 12 Λ C), 16 Λ N( 16 Λ O) => Charge Sym. Break. ( π + , K + γ ) or (K - , π - γ ) p=1.1 (5) B(M1) by DSAM => µ Λ in nucleus 11 7 Λ B, Λ Li etc. (K - , π - γ weak) p= 1.1 or 0.8 (6) B(M1) by γ -weak 12 Λ C, heavier
(5),(6) B(M1) measurements µ Λ in nucleus -> medium effect of baryons g Λ ψ Λ ↑ ψ c J c +1/2 J c "hypernuclear M1 fine structure" J c -1/2 ψ Λ ↓ ψ core nucleus c Λ in s-orbit hypernucleus µ z | B(M1) ∝| < Φ f | Φ i > | 2 = | < ψ Λ ↑ ψ c | g c J c z + g Λ J Λ z | ψ Λ ↓ ψ c > | 2 ∝ ( g c - g Λ ) 2 Accuracy ∆ g Λ < 5% achievable � Doppler shift attenuation method [ same as B(E2), established] Weak K - or π + beam usable for light hypernuclei; � γ -weak coincidence method [ new, only possible at J-PARC] Λ C and heavy hypernuclei; Intense K - beam necessary for 12
B(M1) measurement by γ -weak coincidence method 400 hours for 12 Λ C -> 5% error of B(M1)
K - Beam momentum for S=-1 0.8, 1.8 GeV/c (K - , π - ) = large σ and non-spin-flip + 1.1 GeV/c (K - , π - ) = spin-flip ・ Reveal all the levels ・ Level assignment ・ Spin-flip B(M1) -> µ Λ
3. Beam and Setup Beamline: K1.1 � K - at 1.1, 0.8 GeV/c 4.2x10 7 K - /spill K/ π > 1 π + at 1.05 GeV/c Spectrometer: SPESII � (existing) Hyperball3 ∆ p/p < 2 MeV (FWHM) Ω ~ 20 msr SKS (100 msr) is better Hyperball3 (2007?) � ε > 10% at 1 MeV or Hyperball2 (2003) ε ~ 5% at 1 MeV
Comparison of K1.1, K1.1BR, and K1.8 Subjects (1), (2), (4), (5), (6) require production of spin-flip states by 1.1 GeV/c (K - , π - ) reaction. Beamline K1.1 K1.1BR K1.8 Momentum 1.1 1.1 1.1 K - intensity /spill 4.2x10 7 1.0x10 7 0.049x10 7 K/ π > 1 / 1 ~ 1 / 5 > 1 / 1 Λ Li (3/2 + ) (spin-flip state): d σ/ d Ω = 17 µ b/sr @10 0 , Hyperball3 eg. 7 Ω ( msr) 20 (SPESII) 50 (SKS) γ yield (counts/hour) Ge rate limit = 2x10 7 /spill 280 44 17 0.2 (E419) (Ge no rate limit) (580) (134) (17) Ge damage (relative) 1 6 1
4. Upgrade of Hyperball Hyperball2 : under construction (2003) collaboration with CYRIC, Tohoku � Clover Ge (r.e. >120%) +BGO x 6 added � Peak eff. ~ 2.5% -> 5% at 1 MeV � Beam test of Clover Ge (T536, June 2003) OK � VME-based fast readout � Improvement of preamplifier
Hyperball3 (Segmented Clover version) 14 sets � ε > 10% at 1 MeV (x4 of Hyperball) r.e.= 350% � Rate limit PWO ~2x10 7 particles /s (x5) counters � Yield: x20 for single γ x80 for γγ PWO counters
R&D for Hyperball3 � Waveform readout method –> pileup decomposition, baseline restoration High resolution waveform digitizer Data transfer Analysis software � Lower-gain, faster-reset preamplifiers � Faster suppressor than BGO (PWO, BSO, ..) � LN2-free cooling � Radiation damage
5. Summary γ spectroscopy is one of the main strangeness � programs in J-PARC. Systematic studies for various subjects � (YN interaction, impurity effects, medium effects) are proposed. Regarded as a day-one experiment. K1.1 + Hyperball3 gives 10 3 improvement. � R&Ds for Hyperball3 have been started. �
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