Electron Capture branching ratio measurements at TITAN-TRIUMF

Transcription

1 Electron Capture branching ratio measurements at TITAN-TRIUMF T. Brunner, D. Frekers, A. Lapierre, R. Krücken, I. Tanihata, and J. Dillingfor the TITAN collaboration Canada s National Laboratory for Nuclear and Particle Physics, Vancouver, British Columbia, Canada

2 Outline Neutrino experiments and the neutrino mass Double beta decay experiments and their theoretical description Electron Capture Branching Ratio measurements (EC-BR) with the EBIT 18. Jan 008

3 Neutrino experiments and the neutrino mass Neutrino oscillation Tritium decay KATRIN, picture taken from SNO, picture taken from Indicate a neutrino mass [1] Determination of mixing angle θ ij Indicate mass hierarchy Determination of δm² 18. Jan 008 Relative mass scale [1] T. Kajita and Y. Totsuka, Rev. Mod. Phys. 73(001)85 Absolute mass scale Endpoint energy of 3 H decay Effective mass for degenerated neutrinos: = ν j e j j m U m 3

4 Double βdecay Worldwide topic Standard model EXO SNO Lab NEMO3 New physics GERDA CUORE COBRA Underground labs n + n νdouble β-decay p + β + ν β e n + n 0νdouble β-decay p + β + 0 ν β e ν e ν e Half life> years ( 76 Ge) 18. Jan 008 Dirac- Neutrino β ν e Lepton number violation Half life> 1.9x10 5 years [] ( 76 Ge)!!! Majorana-Neutrino β [] C.E. Aalseth et al., Phys. Rev. D65(00)09007 [3] S.R. Elliott and P. Vogel, Annu. Rev. Nucl. Part. Sci. 5(00)115 4

5 Double βdecay Worldwide topic Standard model EXO SNO Lab NEMO3 New physics GERDA CUORE COBRA Underground labs n + n νdouble β-decay p + β + ν β e n + n 0νdouble β-decay p + β + 0 ν β e ν e ν e Half life> years ( 76 Ge) 18. Jan 008 Dirac- Neutrino β ν e Lepton If observed: number violation Half life> 1.9x10 5 years []( 76 Ge)!!! ( 0ν ) ½ N Majorana-Neutrino β mν = F T½ ev [3] e [] C.E. Aalseth et al., Phys. Rev. D65(00)09007 [3] S.R. Elliott and P. Vogel, Annu. Rev. Nucl. Part. Sci. 5(00)115 5

6 νββ νββdecay 4 ν C G F ( β β ) 7 C F ( ) ( ν ) DGT ( ν ) DGT Γ = cos( Θ ) M f( Q ) 8π = G ν (Q,Z) M Primakoff-Rosen approximation [4] M ( ν ) DGT = = 18. Jan 008 (f) + + (i) 0g. s. σkτk 1 m 1 m σkτ 0 k k k g. s. 1 (f) + m Q ββ(0 g. s.) + E(1 m ) E0 m m + - ( ) m( ) M GT M GT [4] H. Primakoff and S.P. Rosen, Rep. Prog. Phys. (1959)11 E m accessible thru chargeexchange reactions in (n,p) and (p,n) direction ( e.g. (d, He) or ( 3 He,t) ) as well thru EC-BR 6

7 0νββ νββdecay g Γ = G (Q,Z) M M m 0ν 0ν ( β β ) ( 0ν ) V ( 0ν ) DGT DF ga 1 (f) π ββ g.s. m 0 ν e mass of Majorana neutrino (f) π π (i) g.s. O (r, S, L) J m J m O (r, S, L) ν ν στ στ g.s. Γ = G + Fermi β β m Q (0 ) + E( J ) E m νe nucl. matrix element NOTaccessible thru charge-exchange reactions Forbidden in Standard Model lepton number violated neutrino enters as virtual particle J. Dilling et al., Can. J. Phys. 85(007)57

8 Theoretical description Description of double β decay nuclei with the proton-neutron Quasiparticle Random Phase Approximation (pn-qrpa) Adjustable particle-particle parameter g pp in pn-qrpa for all singleand double β decay calculations (The many-particle Hamiltonian is a function of g pp ) Extrapolation of calculated matrix elements to νββhalf life provides g pp (g pp ~ 1) νββdecay is sensitiveto g pp, 0νββdecay is insensitiveto g pp Cross check of g pp with single β - and EC decays 18. Jan 008 8

9 Example 116 Cd Recent critical assessment of the theoretical situation 1. g pp also enters into calculation of single β decay. this allows to make (in few cases) precise predictions about EC-rates 3. in confronting with experiment, theory fails BADLY (if EC is known) ( ν ) M tot In case of single state dominance: M M EC β 1 (f) + Q ββ (0 g. s.) + E g.s. (1 ) E Cd ~ expmt M EC expmt M EC =1.4 ε=0.095% M EC =0.69 ε=(0.07±0.0063)% M EC =0.18 ε=(0.0019±0.003)% theory[5] exp1[6] exp[7] [5] J. Suhonen, Phys. Lett. B607(005)87 [6] M. Bhattacharya et al., Phys. Rev. C58(1998)147 [7] H. Akimune et al., Phys. Lett. B394(1997) ~1.03 gpp

10 Determination of M EC ( ν ) M tot M M EC β 1 (f) + Q ββ (0 g. s.) + E g.s. (1 ) E0 The use of g pp (ββ) ~ 1.0 reproduces the νββdecay half-life but not the single EC and β - decay. Discrepancies of 1 orders of magnitude are possible s 100 Tc The loose end: EC rates are badly known, or not known at all Q EC = ε =(1.8 ±0.9)x10-3 %[8] Q β = 3.0 β - β Mo 100 Ru [8] A. García et al., Phys. Rev. C47(1993) Jan

11 ISAC at TRIUMF TITAN 18. Jan

12 TITAN Facility TRIUMF Ion Trap for Atomic and Nuclear science Penning trap for high precision mass measurements ~5 kv q A + q+ Electron Beam Ion Trap (EBIT) for charge breeding A q+ Radio-Frequency Quadrupole(RFQ) cools and bunches ISAC beams Short-lived isotopes from an Isotope Separator and Accelerator (ISAC) A + Penning trap to cool HCI from EBIT (under design) Wien filter: q/m selection 1

13 The EBIT -Schematic Einzel lenses Cryogen-free superconducting coils Working parameters: Max. e-beam energy: ~70 kev Max. e-beam current: 500 ma(up to 5 A) Max. magnetic field strength: 6 T Current density (center): A/cm Retractable e-gun Magnetic-field distrib. Taken from M. Froese Electron collector _ Up to ~-60 kv Trap + Electron gun _ 0 to ~10 kv Up to ~-60 kv Dip 18. Jan 008 ~460 mm ~35 mm 13

14 The EBIT -Schematic Cryogen-free superconducting coils EC-BR measurements Einzel lenses Beta detector Magnetic-field distrib. Taken from M. Froese 1/7 X-ray detector Trap Dip 18. Jan 008 ~84 mm 14

15 Setup ECBR measurements X-ray detector Storage and detection Penning trap Ion injection ions trapped 6 T magnet Trap electrodes Beta detector (PIPS) TITAN Electron Capture Branching Ratio: New approach: spatial separation of X-ray and β - detection Seven X-ray detectors around segmented trap.1% solid angle for X-ray detection after EC No electron background at X-ray detectors due to strong magnetic field (6T) Long holding times in vacuum of P < mbar 15

16 Branching Ratio Measurements CANDIDATES FOR BRANCHING RATIO MEASUREMENTS 100 Mo : 100 Tc (EC) [1+ 0+, T1/ = 15.8 s] K α = 17.5 kev 110 Pd : 110 Ag (EC) [1+ 0+, T1/ = 4.6 s] K α =1. kev 114 Cd : 114 In (EC) [1+ 0+, T1/ = 71.9 s] K α =5.3 kev 116 Cd : 116 In (EC) [1+ 0+, T1/ = 14.1 s] K α =5.3 kev 8 Se: 8m Br (EC) [- 0+, T1/ = 6.1 min] K α =11. kev 18 Te : 18 I (EC) [1+ 0+, T1/ = 5.0 min] K α =7.5 kev 76 Ge: 76 As (EC) [- 0+, T1/ = 6. h] K α =9.9 kev s Q EC = ε % 100 Tc Q β = β Mo - β Ru 10 5 ions in trap with one half-life measurement cycle: solid angle:.1% 5.7 x 10 detection efficiency: 30% -3 EC counts/cycle 9. Jan EC counts EBIT fills 74h 88h proposed for 100 Tc

17 Simulations B max ~ 3T Ø5 mm B max = 6T 5 kv 4.7 kv 5 kv 3 MeV electrons B max = 6T 84 mm to center 5 mm Loss through magnetic bottle for θ> 79deg: v v B = 1 B max crit min B max = 6T Loss through wall collisions Rotating wall cooling or side-band cooling

18 β-detector Passivated Implanted Planar Silicon detector 9 Li PIPS 9 Li Q = 13.6 MeV Alfoil T ½ [lit] = 178.3ms T ½ [PIPS] = 17.3(16.6)ms 1130 counts.1 x 10 6 counts 18. Jan

19 Summary There are discrepancies in the description of νββwithin the pn-qrpa M EC and M β for single decays do not agree with those extrapolated from νββdecay TITAN EBIT offers a novel approach for EC-BR measurements Long storage times Low background at X-ray detector for the future TITAN EBIT will be connected to the TITAN beam line (EBIT was commissioned in August 006). First EC branching ratio measurements with the EBIT by the end of this year 18. Jan

20 People/Collaborations M. Brodeur, T. Brunner, C. Champagne, J. Dilling, P. Delheij, S. Ettenauer, M. Good, A. Lapierre, D. Lunney, C. Marshall, R. Ringle, V. Ryjkov, M. Smith, and the TITAN collaboration. U. of Manitoba McGill U. Muenster U. MPI-K U. of Calgary U. of Windsor Colorado School of Mines UBC 18. Jan 008 GANIL TU München 0