Polarimeters for Tests of EPR Paradox Kentaro Yako PST05 Nov. 15, 2005 Topics: ・ Bell’s Inequality in Spin Correlation of 2N systems ・ Proton Polarimeter, EPOL ・ Neutron Polarimeter, NPOL →　poster presentation by S. Noji & K. Miki

Collaborators: T. Saito, H. Sakai, T. Kawabata, T. Ikeda, K. Itoh, H. Kuboki, Y. Maeda, N. Matsui, H. Matsubara, K. Miki, S. Noji, M. Sasano, Y. Satou,K. Sekiguchi, K. Suda, A. Tamii, and T. Uesaka

EPR paradox Einstein, Podolsky and Rosen (1935): Quantum mechanics (QM) is incomplete in terms of local realism. “Paradox”. Hidden variables? b a Particle 2 [1S0] Particle 1 Polarimeter B Polarimeter A entangled state QM EPR or

Test of Bell’s inequality by spin correlation measurement J.S. Bell (1964): Any local hidden variable theory contradicts QM. b a Particle 2 [1S0] Particle 1 Polarimeter B Polarimeter A θ C a b Spin correlation function Bell’s inequality QM -1 20 40 60 80 θ (degrees)

Our experiment Spin correlation in 1S0 p-p (2He) system ・ Production of 2He by (d,2He) reaction Two protons in one polarimeter Good figure of merit & 2-proton tracking capability →　EPOL

Polarimetry of EPOL Inclusive p + 12C scattering Left / Right - asymmetry Figure of Merit : analyzing power (Ep,θ) 135 MeV McNaughton et al. Analyzer target

RIKEN Accelerator Facility AVF K = 540 MeV Ed = 270 MeV Ring Cyclotron SMART SMART EPOL EPOL

Production of 2He at SMART EPOL F2 2He production: 1H(d,2He)n reaction at 0 deg Td = 270 MeV 2nd focal plane of SMART high purity 　　　 ～98% In abundance　 2x103 pairs / s (0.3 nA, 100 mg/cm2) ±2% 10 msr 50H x 10V cm2 Focal plane size

Proton polarimeter EPOL ・ Analyzer target : Carbon block 5 cmt ・Trigger signals, charge information : Plastic scintilators HOD1, HOD2 ・Trajectory before and after analyzer: Before After : MWDC#1 4 x (XUV) : MWDC#2, 1 x (UV) MWDC#3 4 x (XY) Y U X ・Angular acceptance : θ < 20 deg V

Multi wire drift chambers ・ cell structure: (MWDC#1) ・ operation gas : Ar(50%) + Ethane(50%) ・ cathode and potential voltage: －2.7 kV ・ number of sense wires: 320 (#1) + 96 (#2) + 384 (#3) = 800 ・ readout : LeCroy2735DC – LeCroyTDC3377 ・ position resolution: ～0.2 mm ・ efficiency : 96～99% / plane

Calibration of EPOL Beams Ay(θ) Energy dependence θc.m. (deg) ・ beam H.O. Meyer et al., PRC 27, 459 (1983) Primary beam is unavailable Secondary beam : … p + 12C elastic scattering Time reversal → induced polarization P = Ay Ep = 160 MeV at θ = 19o Py = 0.943±0.013 ・　Unpolarized p beam → eliminate the false asymmetry Ay(θ) Energy dependence ・ Energy degraders (brass) θc.m. (deg) EPOL較正

Spin precession Spin precession C target Swinger EPOL SMART Energy Degrader EPOL SMART 158 -- -0.552 140 6.0 -0.522 130 9.0 -0.505 120 12.0 -0.491 Ep (MeV) Degrader (mm) Px @ FP2 EPOL較正

Spectra with degrader

Effective Ay of EPOL Sector Results at Ep = 120～160 MeV AC = 0.11～0.30 εds = 2.8～4.7% FOM = (0.7～2.6) x 10-3 結果

Two-ray tracking efficiency Hit in the same cell … efficiency becomes low. analysis of x-position …OK. y-position …difficult ・ |y(1)－y(2)| > 20 mm on Carbon target x 0.70 ・ Two-ray tracking x 0.79 Total effieicncy 0.55 0 25 50 75 100 125 |y(1)－y(2)| (mm) イベント選択

Summary To test Bell’s inequality by measuring C(θ) in two-proton system, we constructed a focal plane polarimeter, EPOL, at SMART at RIKEN. EPOL was calibrated at 120ー160 MeV by using polarized protons produced by p+C elastic scattering: EPOL is capable of measuring two-proton’s polarization simultaneously. Two-ray tracking efficiency is ～0.55. AC = 0.11～0.30 εds = 2.8～4.7% FOM = (0.7～2.6) x 10-3

Spin correlation function

Result of spin correlation measurement Bell’s inequality is violated by 2.9 standard deviations. Sakai et al., submitted to Nature Physics

EPR correlation in n-p system … NPOL 2H target NPOL n(TOF) p EPOL np[1S0] SMART 2H(d,d*)d* d* : pn 系が[1S0]に結合した状態

RIKEN NPOL