A taste of Proton-rich nuclei. David Jenkins

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1 A taste of Proton-rich nuclei David Jenkins

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3 even%a% odd%a%!2%%%%%%%%%%%%%!1%%%%%%%%%%%%%%0%%%%%%%%%%%%%%1%%%%%%%%%%%%%%2%!5/2%%%%%%%%%!3/2%%%%%%%%%!1/2%%%%%%%%%%1/2%%%%%%%%%%3/2%%%%%%%%%%5/2% Isobaric Spin (Isospin) In the absence of Coulomb interactions between the protons, a perfectly charge-symmetric and chargeindependent nuclear T% excited%states% force would result in the binding energies of all these isobaric analogue nuclei being identical; that is, they would be structurally identical. forbidden%states% proton%rich% N=Z% N=Z% neutron%rich% ( ) 2 T z = N Z projec;on% forbidden%states% 5/2% % % % 3/2% % % % 1/2% % % isospin% % % 2% % % % 1% % % % 0%

4 X-ray burst scenario Neutron stars: 10 km radius, 1.4 M o, Normal star 4

5 Nuclear Astrophysics and N=Z

6 Astrophysical rp-process From: Possible waiting-point nuclides 6

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8 Testing unitarity of the CKM matrix For beta decays between T=1 analogue states, the CVC hypothesis demands that: Tests of this can therefore be performed for N=Z nuclei with T=1 ground states or for T z =-1 nuclei (harder) The CKM matrix Euroschool Piaski, September

9 Testing the CVC hypothesis High precision measurements needed (some of the most precise ever made on nuclei): Decay Q-value = Mass measurements Drives development of trapping technology Lifetime = High precision decay measurement with pure sample Drives techniques with radioactive beams Branching ratio = Locate as many non-analog branches as possible Other corrections e.g. radiative, isospin purity Present approach is to calculate and hope these are accurate Some possible scope for experimental measurements

10 Ft-values 22 Mg, 34 Ar, 62 Ga and 74 Rb: Error bars in Ft dos not reflect the accuracy of Q EC -determination Q EC -values of 26 Si and 42 Ti in progress V ud = (26) New Q EC -value determinations (Penning Trap): 22 Mg M. Mukherjee et al., Phys. Rev. Lett. 93 (2004) Al m, 42 Sc, 46 V T. Eronen et al., Phys. Rev. Lett. 97 (2006) Ar F. Herfurth et al., Eur. Phys. J. A 15 (2002) Ca G. Bollen et al., Phys. Rev. Lett. 96 (2006) S. George et al., Phys. Rev. Lett. 98 (2007) V G. Savard et al,, Phys. Rev. Lett. 95 (2005) Ga T. Eronen et al., Phys. Lett. B 636 (2006) Rb A. Kellerbauer et al., Phys. Rev. Lett. 93 (2004) Mn and 54 Co T. Eronen et al., Phys. Rev. Lett. 100 (2008) = (10)

11 Example 1: Isospin non-conserving forces

12 For T=1 triplets: MED J = E J,T z = 1 E J,T z =+1. Mirror energy differences are isovector and sensitive to: single-particle Coulomb shifts, electromagnetic spin-orbit interaction, changes of shape/radius of nuclei TED J = E J,T z = 1 + E J,T z =+1 2E J,T z =0. Isotensor energy differences reflecting differences between nn, pp and pn force. Not sensitive to one-body terms but only two-body i.e. sensitive to Coulomb multipole and isospin-nonconserving forces 12

13 Shapes of N=Z nuclei Very, very sensitive to underlying quantum structure The original phenomonological M-M theory, (Microscopic Macroscopic) was very sound. Very Prolate Oblate Triaxial P. Moller and J.R. Nix. At. Nuc. Data Tables, 26 (1981) 1965 S. Aberg. Phys Scr. 25 (1982) 23 W. Nazarewicz. Nucl. Phys A435 (1985) 397. R. Bengtsson. Conf on the structure in the zirconium region, 1988 {Classic Potential Energy Surface calculations. BUT The whole concept of isolated shapes is naive: there are multiple shapes with lots of mixing, as the barriers between shapes are not high.

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15 Recoil-decay tagging 15

16 Recoil-beta tagging 16

17 Recoil separators RITU (Jyvaskyla) FMA (Argonne) 17

18 RDT Instrumentation at JYFL GREAT Focal plane spectrometer RITU Gas-filled recoil separator Transmission % JUROGAM TDR Total Data Readout Triggerless data acquisition system with 10 ns time stamping 18

19 RITU+GREAT 19

20 Test case: 74 Rb 20

21 Proof-of-principle nat Ca ( 36 Ar, pn) 74 Rb E beam = 103 MeV τ ½ ( 74 Rb) = 65 ms β + endpoint ~ 10 MeV σ ~ 10 µb 21

22 High energy positrons 22

23 74 Rb 23

24 Identification of 74 Rb A.N. Steer, et al., NIM A565, 630 (2006) 24

25 74 Rb level scheme from RBT 25

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27 Crossing the line of N=Z 27

28 UoY Designed to suppress events associated with cp evaporamon channels. Consists of x 20 mm CsI crystals (Hamamatsu) divided into 6 flanges (8 x 2 crystals in each flange). Signal chain: Mesytech preamplifiers -> GObox -> Lyrtech ADCs. Measured detecmon efficiency for 1 charged parmcle is %. RITU LISA chamber JurogamII

29 66 Se P. Ruotsalainen et al., Phys. Rev. C 83, (2013) 29

30 Counts / kev Counts / kev Counts / kev Sr 74 Sr kev 74 Rb kev 74 Rb kev 74 Sr kev (a) (b) (c) E γ (kev) Counts / 2 kev (a) (b) (c) ( 70 Br) 70 Kr 964 ( 70 Br) Energy (kev) 1069 ( 70 Br)

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32 Conclusions New techniques developed to study structure of nuclei beyond the line of N=Z: - Beta-tagging Charged particle veto - Highly-pixellated silicon detectors Results obtained on excited states of N=Z-2 nuclei: 66 Se, 70 Kr and 74 Sr TED extracted and compared with shell model calculations TED appear to need additional isospin-nonconserving component to reproduce them as earlier shown in f7/2 shell TED can be reproduced using 100 kev INC term irrespective of orbitals involved e.g. fp for 66 Se and g9/2 for 74 Rb What is the origin of this INC component in terms of nuclear force?