Beta-decay. studies with proton-rich. rich nuclei. Bertram Blank. Université Bordeaux 1 / CENBG

Transcription

1 Beta-decay studies with proton-rich rich nuclei Super-allowed Fermi transitions Mirror decays proton-rich nuclei in the calcium-to-nickel region branching ratios, half-lives, decay schemes, masses isospin mixing decay of 32,33 Ar at SPIRAL branching ratios, decays schemes B(GT) strength distribution Bertram Blank comparison ISOL - fragmentation Université Bordeaux 1 / CENBG

2 Decay of proton-rich nuclei Measurement of γ rays and β- delayed protons, half-lives T B.R. 1/2 ft = f * = C B(F) + B(GT)

3 Superallowed β decay: theory summary 2000 new measurements summary 2009

4 in general: ft = g 2 V MF 2 K + g 2 A MGT 2 for transitions: only vector current due to selection rules ft = K g 2 V MF 2 = f(q ec ) * T 1/2 / BR experimental quantities: masses of parent and daughter, half-life, branching ratio K / (hc) 6 = (12) * GeV -4 s = constant, <M F > 2 = T(T+1) - T zi T zf g v = g F * V ud to be determined one high-precision measurement would be enough BUT..

5 electromagnetic interactions: e.g. positron with protons radiative correction δ R δ R + δ NS isospin impurity: binding energy difference, configuration mixing Coulomb correction δ c = δ c1 + δ c2 if these effects corrected: constant ft value constant vector current hypothesis (CVC) determination of g v via Ft value: many ft values are needed to test CVC and theoretical corrections from g v : Ft = ft (1 + δ R ) (1 δ c + δ NS ) = determination of V ud matrix element of CKM quark mixing matrix V ud = g v / g F 2 V K g (1 + Δ R ) M F 2

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7 10 C T 1/2 Texas A&M 14 O T 1/2 Leuven, Auckland, Berkeley Q EC Auckland 18 Ne T 1/2 TRIUMF Q EC ISOLDE 22 Mg T 1/2, BR Texas A&M Q EC CPT Argonne, ISOLDE 26 Si Q EC, T 1/2, BR JYFL 26 Al m Q EC JYFL 30 S Q EC, T 1/2, BR JYFL 34 Ar T 1/2, BR Texas A&M Q EC ISOLDE 34 Cl T 1/2 Texas A&M 38 Ca Q EC, T 1/2 ISOLDE Q EC MSU 38 K m T 1/2, BR Auckland, TRIUMF 42 Sc Q EC JYFL 42 Ti Q EC, T 1/2, BR JYFL 46 V Q EC JYFL, CPT Argonne 50 Mn Q EC JYFL T 1/2 Auckland 62 Ga T 1/2, BR GSI, JYFL, TRIUMF, Texas A&M Q EC JYFL 66 As Q EC MSU 74 Rb T 1/2,BR TRIUMF, ISOLDE ISOLDE Q EC

8 <Ft> = ( ± 0.79) s g v = (2) V ud = (22) Hardy & Towner

9 13 best known cases for Tz = -1 nuclei: branching ratios for heavy nuclei: theoretical corrections, in particular isospin corrections

10 Towner & Hardy, 2008

11 Towner & Hardy

12 typical setup: - beam purification system: traps - beta detector - gamma detectors measurement cycles: accumulation - purification - transport - decay different fixed dead times: 2 μs, 8 μs, 100μs different detector high-voltages different detection thresholds cycle selection: no beam, detector sparking half-life cuts: test of dead time correction half-life as a function of background, of rate, of detector settings Is there any dependence of the half-life of these parameters? error budget

13 JYFLTRAP β detector Ge detectors Tape transport system

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18 2μs 8μs 100μs

19 test of dead time correction

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22 counting statistics: 0.45 dead time correction: 0.01 experimental parameters (threshold, HV): 0.00 T 1/2 as function of background: 0.00 T 1/2 as function of counting rate: 0.00 wrong implantation: Total: 0.45 T 1/2 ( 42 Ti) = ± 0.45 ms

23 Half-life of 42 Ti: JYFL kev T. Kurtukian Nieto et al., PRC80 (2009) BR = 48.2(15)% Ft = 3114(79)

24 half-life measurement at GSI: T 1/2 = ( ± 0.04) ms B. Blank et al., 2004 half-life measurement at JYFL: ΔT 1/2 = μs T 1/2 = ( ± 0.15) ms G. Canchel et al., 2005 Ft = (72)

25 Half-life of 26 Si: JYFL 2007 I. Matea et al., EPJA 37, 151 (2008) BR = 75.45(58)% Ft = 3060(37)

26 Half-life of 38 Ca: ISOLDE 2007 B. Blank et al., to be submitted BR = 75.45(58)%

27 Half-life of 30 S: JYFL 2009 T 1/2 = (16) ms J. Souin et al.

28 need to know detection efficiency with a precision of 0.1% calibration program for a single-crystal germanium detector: - source measurements - MC simulations J.C. Hardy s Ge detector

29 Mirror β decay Measurements required: β-decay Q value super-allowed branching ratio β-decay half-life β-ν angular correlation coefficient N. Severijns, O. Naviliat-Cuncic

30 Mirror β decay V ud = (17)

31 V ud ud super-allowed β decay: (22) pion decay: (30) neutron decay: (19) mirror β decay: (17)

32 Half-lives of 29 P and 31 S: JYFL 2009 T. Kurtukian Nieto, A. Bacquias et al. T 1/2 = (51) ms T 1/2 = (18) ms

33 Proton-rich nuclei in the region of Ca to Ni studied at the LISE3 facility study of the most proton-rich nuclei technique results: half-lives, decay schemes, masses isospin impurity

34 Proton-rich nuclei in the region of Ca to Ni Mass region (20 (20 Z 28 et et Tz Tz -3/2) 5 experimentsat at GANIL isotopes studied (( Ti Ti au au Ni) Ni) Calcium: 37,36 Ca Titanium: 41,40,39 Ti Vanadium: 43 V Chromium: 45,44,43,42 Cr Manganese : 47,46 Mn Iron: 49,48,47,46,45 Fe Cobalt: 51,50 Co Nickel: 53,52,51,50,49,48 Ni Copper: 55 Cu Zinc: 56,55,54 Zn

35 Primary beam: MeV/A intensity: 3-4 μae SISSI target: nat Ni 200 mg/cm 2 spectrometer LISE3 : degrader Be (50 μm) Wien filter detection setup silicon telescope identification of implanted fragments DSSSD (X-Y): 2 x 16 x 3 mm - veto for light particles - residual energy, x-y position - energy loss - time of flight: micro-channel plate detectors RF cyclotron

36 7 to 8 identification parameters Identification projectile fragments

37 Proton and gamma branching ratios and energies Radioactivity of 41 Ti Radioactivity of 49 Fe A 41 Ti 41 Ti T 41 Ti Correlation time B 1 B 2 Contaminant from 49 Fe and 45 Cr 41 Ti β Protons

38 Background subtraction for γ rays Before Decay of 49 Fe After 49 F 49 F Contaminants Decay of 49 Fe

39 Half-life determination: Fe T (ε,t,p ) i i 1/2 β 1/2 p 46 Fe 46 Mn 45 Cr Ne 1 -a t 1 -a 2 t -a 1 N(e -e t ) 2 -a 3 t -a 1 N(e -e t ) 3 N = an a P [P +(1-P )ε ] 2 p1 p2 p2 β N 2 =a1n0 a 1 -a 2 P p1 +(1-P p1 )ε β a (1- P )[P + (1- P )ε ] 3 p1 p3 p3 β N 3 =a1n0 a 1 -a 3 P p1 +(1 -Pp1)εβ

40 Spectroscopy of Ni T 1/2 = (23.8 ± 0.2) ms P p = (87.2 ± 0.8) % E γ = (765.3 ± 0.6) kev I γ = (73 ± 4) % E γ = ( ± 0.3) kev I γ = (29 ± 3) % E p = (4662 ± 16) kev I p = (8.7 ± 0.8) %

41 Spectroscopy of Ni T 1/2 = (40.8 ± 0.2) ms P p = (31.4 ± 1.5) % E p = (1057 ± 11) kev I p = (2.9 ± 0.3) % E p = (1349 ± 10) kev I p = (9.4 ± 1.3) % E p = (2815 ± 23) kev I p = (0.9 ± 0.4) %

42 Spectroscopy of Fe T 1/2 = (40.8 ± 0.2) ms P p = (31.4 ± 1.5) % E p = (1013 ± 12) kev I p = (1.8 ± 0.3) % E p = ( ) kev I p = (2.0 ± 0.4) % E p = ( ) kev I p = (1.4 ± 0.5) %

43 Isotope Half-life (ms) Total proton branching ratio (%) Mass excess via IMME 37 Ca ± (43) 36 Ca ± (10) 41 Ti 82.6 ± (6) (7) 40 Ti 52.4 ± (13) -9.06(8) 39 Ti 28.5 ± (28) - 43 V 79.3 ± 2.4 < Cr 60.9 ± (8) (3) 44 Cr 42.8 ± (9) (2) 43 Cr 21.1 ± (28) -1.92(6) 42 Cr 13.3 ± (50) - 47 Mn 88.0 ± 1.3 < Mn 36.2 ± (8) (3) 49 Fe 64.7 ± (4) (2) 48 Fe 45.3 ± (6) (5) 47 Fe 21.9 ± (9) (4) 46 Fe 13.0 ± (38) 0.76 (10) 51 Co 68.8 ± 1.9 < Co 38.8 ± (7) (4) 53 Ni 55.2 ± (10) (4) 52 Ni 40.8 ± (15) (3) 51 Ni 23.8 ± (8) (7) 50 Ni 18.5 ± (39) (3) 49 Ni 7.5 ± (132) - 55 Cu 27.0 ± (43) - 56 Zn 30.0 ± (49) 55 Zn 19.8 ± (51) -

44 Comparison of half-lives (exp / theo) Ti Cr V Mn Quality factor: N cal exp 1 T i -Ti Q=1- N exp i=1 T i Audi: 0.99 (6) extrapolations Honma: 0.96 (3) shell model Ormand: 0.92 (4) shell model Tachibana: 0.75 (4) Gross theory Hirsch: 0.62 (4) pn-qrpa 2 F Co Ni

45 Isospin impurities Proton emission from the IAS is isospin forbidden IAS IAS Comparison of and of for IAS : IAS I p I p I p I βth IX γ IAS I βth I βth 48 IAS Fe : =2.1 %- I = 30% =42 % 52 γ IAS IAS IAS Ni : =10 % - = 38% =64 % Determination of isospin impurities with these experimental data : IAS ' Iγ Γγ Γ γ.sγ = = IAS ' Ip Γ p.ii Γ p.s p.ii ' IAS Γ γ.sγ Ip I (experimental, theory, fixed) I =. ' IAS IAS Γp. Sp Iβth -Ip Γ p : Coulomb and centrifugal barrier penetration S p = 1

46 IAS Isospin impurity: example of Fe Shell model ( 48 Mn) E IAS E γ (IAS 1 + ) Measured energies (kev) Predicted energies (kev) 3037 (10) (1) 2458 IAS I p = 2.1 % IAS I βth = 42 % E γ (2 + - ground state) W.A. Richter, B.A. Brown (5) 233 I I = 0.52 %

47 Isospin impurity: example of Ni IAS Shell model ( 52 Co) Measured energy (kev) Predicted energy (kev) E IAS 2931 (10) 2796 W.A. Richter, B.A. Brown IAS I p = 10 % IAS I βth = 64 % I I = 19 %

48 Isospin impurityof IAS I I ( 48 Fe) = 0.52 %, I I ( 52 Ni) = 19 % neighboring nuclei: surprising however: shell-model study : I I ( 36 Ca) = 0.4 %, I I ( 40 Ti) = 17.3 % (Theory Jyväskylä in sd shell) similar treatment possible for many other nuclei: 45,44 Cr, 46 Mn, 49 Fe, 53,51 Ni. B.A. Brown in sd shell.

49 Beta-decay of proton-rich argon isotopes studied at the low-energy facility of SPIRAL technique results: branching ratios, decay scheme GT quenching B(GT) strength distribution

50 The LIRAT facility at GANIL

51 Experimental setup: Silicon cube detector 6 DSSSDs with 16 * 16 strips 50 cm x 50 cm 6 Plenar silicon detector 50 cm x 50 cm 3 EXOGAM clover detectors I. Matea et al., NIM A607 (2009) 576

52 Proton and γ-ray spectra from Ar 33 Ar proton singles spectrum protons spectrum avec γ coincidence γ-ray spectrum N. Adimi et al., submitted to PRC

53 Quasi complete decay scheme

54 Gamow-Teller strength quenching

55 Gamow-Teller strength distribution: the traditional way 33 Ar

56 Gamow-Teller strength distribution: conversion of the spectrum into B(GT) 33 Ar IAS

57 Gamow-Teller strength distribution: comparison 33 Ar

58 Proton and γ-coincident proton spectra from Ar R. Dominguez Reyes et al.

59 Gamow-Teller strength distribution 32 Ar preliminary R. Dominguez Reyes et al.

60 Conclusion beta decay is a versatile tool - weak interaction studies - isospin impurity determination - BGT measurements