Parity Violation in the decay of 93 Tc

Parity Violation in the decay of 93 Tc 17/2 - isomers polarized B. S. Nara Singh, M. Hass and G. Goldring Weizmann Institute of Science, ISRAEL D. Ackerman, J. Gerl, F. P. Hessberger, S. Hofmann, I. Kojouharov, P. Kuusiniemi, H. Schaffner, B. Sulignano GSI, Germany B. A. Brown NSCL, Michigan, USA Motivation Experiment Results Future

Motivation 1956: Lee & Yang, Parity Non-Conservation (PNC) discovery. Hpnc different behavior under Parity operation. 1957: Wu et al. Measure PNC in -decay of polarized 60 Co. 1958: Feynman & Gell-mann suggest first-order weak interaction in the nuclear potential (PV nuclear force). Consequence PNC in N-N systems. Adelberger & Haxton, Ann. Rev. Nucl. Parti. Sci. 35(1985). Only accessible to study neutral current WI between quarks. Hweak=HL+HSL+HNL( S=1)+HNL( S=0) PV in Nuclei: Probes HNL( S=0); together with N-N scattering data it establishes IS, IV and IT strengths. An avenue full of surprises. Not just a check on SM B. S. Nara Singh et. al.

Observable Parity mixing in the nuclear energy levels shows up in EM and Strong decay. EM transitions: • Circular Polarization in radiation from Unpolarized nuclei • Up-down asymmetry of radiation following polarized thermal neutron capture • decay angular distribution from polarized B. S. Nara Singh et. al.

Only Few Cases In the presence of 107 times strong interaction. Yet significant due to Structural effects. • 18 F • • < 90 me. V 19 F ~ 380(100) me. V 21 Ne < 30 me. V 93 Tc ~0. 59(19)(25) me. V 180 Hf~1. 0(0. 1) e. V B. S. Nara Singh et. al.

• Parity doublet at 300 e. V Proximity. • N=50, Reasonable nuclear Structure Calculations within Shell model. • Establishes IT component and complementary to the studies in light nuclei. • Unique case For non-zero PNC. B. S. Nara Singh et. al.

M. Hass et al. , PLB 371, 25, previous work at SHIPGSI, RMS-LNL 45 Sc(52 Cr, 2 p 2 n)93 Tc Elab(93 Tc) = 65 Me. V Checked with Si-det. Separates and Transfers to Focal Plane Area TF technique for Polarization 0 -180° Asymmetry (A ) in the M 2/E 3( ) -decay due to E 2 Component B. S. Nara Singh et. al. Stepper Motor 2 mins. + 1 sec 16 foils, @70º 15 -15 g/cm 2

45 Sc Setup 1 mg/cm 2 High count rate handling Counts in 751 ke. V line, 6 M per crystal 16 foils, @70º 15 -15 g/cm 2 B. S. Nara Singh et. al.

Triple Ratios & A Independent of Gamma efficiency Beam current fluctuation and experimental artifacts B. S. Nara Singh et. al.

Results pl = 0. 15 known from QP interaction measurements M. Hass et al. , PRC 43, 2140. E(ke. V) 544(93 Ru) 629(93 Tc) 711(93 Tc) 751(93 Tc) 1392(93 Ru) 1432(93 Tc) PLB Present Average 1. 00107(73) 0. 99912(122) 1. 00056(63) 1. 00055(53) 1. 00088(66) 1. 00068(41) 0. 99989(38) 0. 99962(41) 0. 99977(28) 0. 99833(54) 1. 00028(71) 0. 99904(43) 0. 99933(84) 0. 99972(112) 0. 99947(67) 0. 99977(39) 1. 00038(31) 1. 00015(24) B. S. Nara Singh et. al.

Results Preliminary Present+PLB, 371, 25: A = 4. 8 (2. 1). 10 -4 , =0. 34(14)(25) me. V Theory: 1 p 1/2 -0 g 9/2 with IV strength correction by an empirical factor of 0. 15± 0. 15. = - 0. 2 to 1 me. V B. S. Nara Singh et. al.

Future More experiments on 93 Tc(? ? ) 180 Hf: Huge structural effect. Low magnitude for . Need for an independent check. Technique: Low T orientation with NICOLE ISOLDE, CERN and asymmetry. B. S. Nara Singh et. al. Successful Test run, Oct. 04, Production run, May, 05