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Parity Violation in the  decay of polarized 93 Tc 17/2 - isomers

Parity Violation in the  decay of polarized 93 Tc 17/2 - isomers. 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

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Parity Violation in the  decay of polarized 93 Tc 17/2 - isomers

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  1. Parity Violation in the  decay of polarized 93Tc 17/2- isomers 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

  2. 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 60Co. 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.

  3. 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 nuclei B.S. Nara Singh et. al.

  4. 18F < 90 meV 19F ~ 380(100) meV 21Ne < 30 meV 93Tc ~0.59(19)(25) meV 180Hf~1.0(0.1) eV Only Few Cases In the presence of 107 times strong interaction. Yet significant due to Structural effects. B.S. Nara Singh et. al.

  5. Parity doublet at 300 eV 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.

  6. 45Sc(52Cr, 2p2n)93Tc Elab(93Tc) = 65 MeV Checked with Si-det. M. Hass et al., PLB 371, 25, previous work at SHIP-GSI, RMS-LNL Separates and Transfers to Focal Plane Area TF technique for Polarization Stepper Motor 2 mins. + 1sec 0-180° Asymmetry (A) in the M2/E3() -decay due to E2 Component 16 foils, @70º 15-15 g/cm2 B.S. Nara Singh et. al.

  7. Setup 45Sc 1mg/cm2 High count rate handling Counts in 751 keV line, 6M per crystal 16 foils, @70º 15-15 g/cm2 B.S. Nara Singh et. al.

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

  9. Results pl = 0.15 known from QP interaction measurements M. Hass et al., PRC 43, 2140. B.S. Nara Singh et. al.

  10. Results Present+PLB, 371, 25: A = 4.8 (2.1). 10-4 , <Hpnc>=0.34(14)(25) meV Preliminary Theory:1p1/2-0g9/2 withIV strength correction by an empirical factor of 0.15±0.15. <Hpnc> = - 0.2 to 1 meV B.S. Nara Singh et. al.

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

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