発熱型二重荷電交換反応による 4中性子系質量欠損核分光実験

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1 HA RA NiSHiNA C E N T E R 発熱型二重荷電交換反応による 4中性子系質量欠損核分光実験 木佐森慶一 (東大CNS 理研JRA) SHARAQ6 Collaboration 木佐森慶一, 下浦享, 李清秀, 井手口栄治C, 稲辺尚人A, 伊藤正俊D, 上坂友洋A, 大田晋輔, 亀田大輔A, 川畑貴裕B, 川瀬頌一郎, 菊地陽介, 久保敏幸A, 久保田悠樹, 郷慎太郎, 小林幹, 近藤洋介E, 坂口聡志I, 酒井英行A, 笹本良子, 笹野匡紀A, 佐藤広海A, 清水陽平A, 鈴木宏A, 高木基伸, 民井淳C, 竹田浩之A, 武内聡A, 津村美保B, 時枝紘史, 西隆博G, 西村美月A, 野地俊平H, 馬場秀忠A, 馬場辰彦B, 堂園昌伯A, 福田直樹A, 藤井俊彦, 前田幸重F, 松原礼明A, 三木謙二郎C, 道正新一郎, 宮裕之, 柳沢善行A, 矢向謙太郎, 横山輪, 吉田光一A, M. AssieJ, D. BeaumelJ, F. HammacheJ, A. StolzH 東大CNS, 理研仁科セA, 京大理B, 阪大RCNPC, 東工大理D, 東北大CYRICD, 宮崎大工E, 東大理F, MSU NSCLH, 九大理I, IPN OrsayJ 213年 8月 5日 若手三者夏の学校 1 R I K E N Q

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3 n 8 c) I to ~, o~ CD i 5 g~ c5 I I 21 7'2 Pion {'~ Bound State ~Region Momentum (MeV/c) n n Energy (MeV) n + 2 H H 1/2 + + Argonne v 18 With Illinois-2 4 n 2 4 H + 5 H 1/2 + 6 n 3/ n + Fig. 1. The da/d~2dp (lab frame) data plotted versus n + momentum, with arrows indicating the region in which counts corresponding to a bound tetraneutron would be expected modified 1 S 1 S -2π 1 S -AV1 AV18 Exp 4 He 5 He 6 He 6 Li

4 Hamiltonian (1) within a large model space which is conis located at a small relative distance between the neutr sistent with the nn interaction Vnn. To this end, we expand correlation: and that the corresponding configuration is rather comp the wave function!!r1 ; r2 " with the eigenfunctions of the X in the coordinate space. S# ^ ^!The!r ; r " # f!r;! R"' single-particle Hamiltonian h^nc. In the expansion, we ex11r"&yl!r"y 1 2 L L L # wave functions of Li for different value plicitly exclude those states which are occupied by the core T. Nakamura al., PRL 96 as (26) of r. T R are plotted in Fig. 2etL (solid line) a function nucleons, as in the original Cooper problem [1]. The E1 excitation three-body wave function has not been presented in groundn statespatial wave function is obtained as the state with structure at the low-density surface region where is know, the spin wave way asj#far asiwe although the function. coordinate sys S# the total angular momentum J #. We transform it to the b Breakup Strong E1 transition at Breakup reaction!r; R" of has11been Li employed in several previous calculati relative and center of mass (c.m.) coordinates for the [16,22]. For comparison, those of 16 C are also shown by T. Nakamura et al., PRL 96 (26) valence neutrons r # r1 $ r2 and R #!r1 % r2 "=2 (see dashed lines with arbitrary scale. Since we consider onfig. 1) [25 27]. To this end, we use the method of density-dependent contact interaction (2), this is eff Bayman and Kallio [28]. That is, we first decompose the tively equivalent to probing the wave function at differ wave function into the total spin S # and S # 1 compodensities. Let us first discuss the wave function of 11 Li nents. The coordinate transformation is then performed for R # :5 fm, where the density is close to the nor the S # component, which is relevant to the pairing correlation: X R = 4. R =.5 fm.15 R = 2. fm.3 ^!" j#s# i; (3) ^ L!R"'!S#!r1 ; r2 " # fl!r; R"&YL!r"Y.1 Introduction Coulomb Breakup di-neutron correlation L R = 1. fm (fm ) 年12月21日金曜日 R = 2.5 fm R = FIG. 1 (color online). A two-dimensional pl R jfl#r!r; state two-particle function r.4 R = 3. fm = 8.R R = 1.5wave fm plotted.1 as a function of the relative distan neutrons r and the distance between.1 the cent 1 1 as 5 denot 1 5 and 15 core 5 nucleus 15 R, two neutrons the r (fm) r (fm) r (fm) K. Hagino et. al., PRL (27).8 r R fl=(r,r) where j#s# i is the spin wave function. n BCS-BEC crossover 2.5 FIG. 2. The ground state two-particle wave funct

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7 Characteristics of the Reaction 4He(8He, 8Be)4n n at 2 AMeV of 8He beam Small momentum transfer - Exothermic reaction Kinematical Consideration - momentum transfer is less than 2 MeV/c 8 4n 8Be He with small q Binary reaction with small q 4He!4n Inelastic-type but small Q-value Exothermic Charge Exchange Reaction $# Low background and high acceptance - PID of 8Be - coincident Multi8 - invariant mass of the Be Neutron - decay corn satisfy the acceptance decay energy of Be(g.s.): 92 kev!# 4He(8He,8Be) Size of decay corn at final focal 2 A MeV $'()*+,-*./ 4He(18O,18Ne) 4 A MeV 14!" 8 " 8th NP-PAC Meeting6 α 8Be Distance between two alpha for y (mm) $"! ((MeV) n C B Be Li He H n two-alpha particles $1,(23($' α 12 #" %"" q (MeV/c ) %#" &"" Distance between two alpha for x (mm)

8 Specification Beamline - High-resolution achromatic mode - momentum resolution at F6 (dispersive) : Δp/p = 1/7 - target position (achromatic) : σ= 8 mm n SHARAQ spectrometer Effective Solid Angle n Beam 2α 2α Ground State Δp/p <.74 % 2 AMeV 8Be 2α Optimize the ion optics optimized Maximum rigidity 6.8 Tm Momentum resolution 1/1 Momentum acceptance 1.8 % Angular acceptance - vertical 1.5 deg - horizontal 2.9 deg Solid angle 4.3 msr -5 standard 5 1/147 1% liq. He target 1.7 deg 3. deg 4.8 msr 2α

9 !" &5-6/7"-1* ****25#+!# 9-.."32-5!&!'!( :-3+1/3,." 8+#526+5!"#$%&' ("#)*$+,-./"-1!+23*4"1+ n!$#" %" %&!+23

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11 2 alpha tracking at S2 Plastic Scintillator CRDC 2 CRDC 1 E E z 2 drift plane １ anode wire y １ x cathode pad 2 LUPO discri. (FPGA) anode anode anode anode x (mm) V １ time (ns) CRDC2-1 CRDC2-2 ADC T/H (trigger) Disc cathode cathode cathode pulse shape x direction Multiplexer Disc. charge distribution 3 cathode 1-1 Voltage (V) charge (ch) CRDCs: Cathode Readout Drift Chamber y (mm) t focal plane y direction FADC z - x direction - charge distribution of cathode pads - y direction - drift time - pulse shape fitting uing flash-ADC 2 x (mm) CRDC1-2 CRDC1-1

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