parity violation in the decay of polarized 93 tc 17/2 - isomers
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
Parity Violation in the decay of polarized 93Tc 17/2- isomers
B.S. Nara Singh, M. Hass and G. GoldringWeizmann 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. BrownNSCL, Michigan, USA
MotivationExperimentResultsFuture
B.S. Nara Singh et. al.
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
Motivation
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 nuclei
B.S. Nara Singh et. al.
Only Few Cases
• 18F < 90 meV
• 19F ~ 380(100) meV
• 21Ne < 30 meV
• 93Tc ~0.59(19)(25) meV
• 180Hf~1.0(0.1) eV
In the presence of 107 times strong interaction .Yet significant due to Structural effects.
kE
O H pnc *||
B.S. Nara Singh et. al.
• 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.
217
|2|2
132
17|2|
213
*||
M
Ek
kE
O H pnc
B.S. Nara Singh et. al.
45Sc(52Cr, 2p2n)93Tc Elab(93Tc) = 65 MeV Checked with Si-det.
Separates and Transfers toFocal Plane Area
M. Hass et al., PLB 371, 25, previous work at SHIP-GSI, RMS-LNL
TF technique for Polarization Stepper Motor
2 mins. + 1sec
16 foils, @70º15-15 g/cm2
0-180° Asymmetry (A) in the M2/E3() -decay due to E2 ComponentmeV
Qp
A
lpncH
1
||)28(91|
2
17||
2
17|
B.S. Nara Singh et. al.
45Sc 1mg/cm2
16 foils, @70º15-15 g/cm2
Setup
High count rate handling
Counts in 751 keV line, 6M per crystal
B.S. Nara Singh et. al.
Triple Ratios & AIndependent of Gamma efficiency
A
A
W
W
llrr
lrrlDR
1
1
)0(
)(
Beam current fluctuation and experimental artifacts
)751(
)()(
iDR
iDRiTR
)751(1
)751(1
TR
TRA
B.S. Nara Singh et. al.
Resultspl = 0.15 known from QP interaction measurements M. Hass et al., PRC 43, 2140.
E(keV)PLBPresentAverage
544)93Ru(1.00107)73(0.99912)122(1.00056)63(
629)93Tc(1.00055)53(1.00088)66(1.00068)41(
711)93Tc(0.99989)38(0.99962)41(0.99977)28(
751)93Tc(0.99833)54(1.00028)71(0.99904)43(
1392)93Ru(0.99933)84(0.99972)112(0.99947)67(
1432)93Tc(0.99977)39(1.00038)31(1.00015)24(
B.S. Nara Singh et. al.
Results
Present+PLB, 371, 25: A = 4.8 (2.1). 10-4 , <Hpnc>=0.34(14)(25) meV
Theory: 1p1/2-0g9/2 with IV strength correction by an empirical factor of 0.15±0.15. <Hpnc> = - 0.2 to 1 meV
Preliminary
B.S. Nara Singh et. al.
Future More experiments on 93Tc(??)
180Hf: Huge structural effect. Low magnitude for <Hpnc>. Need for an independent check.
Technique: Low T orientation with NICOLE ISOLDE, CERN and asymmetry.
Successful Test run, Oct.04,Production run, May, 05