β decay studies with the WITCH experiment
Michaël Tandecki
on behalf of the WITCH team:
M. Breitenfeldt, S. Van Gorp, E. Traykov , F. Wauters, N. Severijns (K.U.Leuven), M. Beck, P. Friedag, J. Mader, Ch. Weinheimer (Univ. Munster), A. Herlert, F. Wenander (ISOLDE-CERN) , F. Glück, V. Kozlov (FZK Karlsrühe), D. Zakoucky (NPI-Rez, Prague) Overview
• Theory
• WITCH set-up
• Physics program
• First results
• Conclusion & Outlook
Michaël Tandecki - 21/07/2009 Overview
• Theory
• WITCH set-up
• Physics program
• First results
• Conclusion & Outlook
Michaël Tandecki - 21/07/2009 Nuclear beta decay
- - n →→→ p + e + νννe βββ - decay
+ + p →→→ n + e + νννe βββ - decay
- p + e →→→ n + νννe Electron Capture
Four-fermion contact interaction: In gauge theory:
Michaël Tandecki - 21/07/2009 WITCH physics
• Weak Interaction Hamiltonian:
Standard Model (V-A Int.): C S = C T = C P = 0
C 1)C 1) T ≤ 9% S ≤ 7% 95.5% CL (2 σ) CA CV
1) N. Severijns, M. Beck, O. Naviliat-Cuncic, Rev. Mod. Phys. 78 (2006) 991 Michaël Tandecki - 21/07/2009 Beyond Standard Model (SM)
Example :
Exchange by leptoquarks: mediated by vector ( X) or scalar ( Y) leptoquarks
In gauge theory:
(u has charge +2/3e, d has charge -1/3e) Michaël Tandecki - 21/07/2009 Physics principle
β-ν correlation 2 ' 2 v CS+ C S W()θ≅ 1 + a cos() θ a ≈1 − 2 c CV Scalar
Vector β+ β+ 1
0.8 ν 0.6 V νe e S 0.4
0.2
e.g. Fermi βββ+-decay 0 100 200 300 400 500 Recoil energy (eV) Michaël Tandecki - 21/07/2009 Traps for correlations in nuclear beta decay
N. Scielzo, S.J. Freedman et al., PRL 93 (2004) 102501 A. Gorelov, J. Behr et al., PRL 94 (2005) 142501 R. Rodriguez, O. Naviliat et al., NIM A565 (2006) 876 M. Beck, N. Severijns et al., NIM A503 (2003) 567 G.P. Berg, K. Jungmann et al., NIM B204 (2003) 52 S.G. Crane, D.J. Vieira et al., PRL 86 (2001) 2967
Paul
Penning MOT
Michaël Tandecki - 21/07/2009 Overview
• Theory
• WITCH set-up
• Physics program
• First results
• Conclusion & Outlook
Michaël Tandecki - 21/07/2009 WITCH location
Michaël Tandecki - 21/07/2009 Overview of the set-up WITCH: Weak Interaction Trap for Ch arged particles
~7m
Michaël Tandecki - 21/07/2009 Penning traps
B: radial confinement E: axial confinement
Three eigen motions:
Reduced cyclotron at ω+ (mass dependent)
Harmonic oscillation at ωz
Interplay between B and E field at ω- (mass independent) These eigen motions can be excited independently Possibility of mass selectivity/purification Michaël Tandecki - 21/07/2009 Penning traps
• Kapton wires replaced by ceramics • Whole structure redesigned + out of titanium • Buffer gas line in metal • NEG coated foil around traps • Heater to bake the system and activate the NEG
Michaël Tandecki - 21/07/2009 The traps
Michaël Tandecki - 21/07/2009 Penning trap experiments
340
320
s 300 µ 74 Rb 280
260 MeanTOF/ 240 74 + Σ = 1100 ions Rb 220 0 5 10 15 20 25 30 ν - 1230051 / Hz c
JYFLTRAP
ISOLTRAP
SHIPTRAP Michaël Tandecki - 21/07/2009 Retardation
retardation Counter, Micro-channel Plate detector retardation (MCP) potential
!! probes velocity component parallel to electric field !!
conversion of radial into longitudinal kinetic energy necessary
decay trap in 9T –field, retardation in 0.1T field Providing slow enough field change Principle of adiabatic invariance of the magnetic flux:
2 retard trap p⊥ B = const Ekin,⊥ E kin , ⊥ = BB min max
Energy Conversion: 1−Bmin B max = 98.9%
Michaël Tandecki - 21/07/2009 Retardation spectrometer
Michaël Tandecki - 21/07/2009 Other MAC-E filters (aSPECT)
aSPECT - Mainz
Michaël Tandecki - 21/07/2009 Other MAC-E filters (KATRIN)
Michaël Tandecki - 21/07/2009 Pulsed drift tube (PDT)
“late” ions Well Well bunched “early” 39K from REXTRAP
Michaël Tandecki - 21/07/2009 Overview
• Theory
• WITCH set-up
• Physics program
• First results
• Conclusion & Outlook
Michaël Tandecki - 21/07/2009 Choice of isotope
• Interesting from a physics point of view
• Production yield @ ISOLDE ~ 10 6 / 10 7 particles per second • Half-life: order of 1 s • Low ionisation potential • Stable daughter isotope • Decay mode: β- (± 10 times more recoil ions than β+) • Minimal isobaric /isomeric contamination • Simple decay scheme
=> 35 Ar
Michaël Tandecki - 21/07/2009 Issues with 35 Ar
• Isobaric contamination from 35 Cl During the run: 25 times more Cl than Ar In the meantime: ratio should be fifty fifty
• Charge exchange with buffer gas We couldn’t cool the ion cloud, because the ions were neutralized before being cooled
• Secondary ionization ‘Noise’ showing up when switching the spectrometer
Michaël Tandecki - 21/07/2009 Charge exchange
• Charge exchange; not an immediate problem for REXTRAP, because they use high repetition rates. • How probably is charge exchange? In one mm 3 @ 10 -5 mbar: 2.5 10 8 gas part. ↔ 10 5-10 6 in a typical ion cloud
• Impurities possibly coming from; - buffer gas system
Michaël Tandecki - 21/07/2009 Unwanted Penning traps
• Penning trap = magnetic field + electrical field
• Unwanted traps can cause discharges and ‘secondary ionization’
Michaël Tandecki - 21/07/2009 Overview
• Theory
• WITCH set-up
• Physics program
• First results
• Conclusion & Outlook
Michaël Tandecki - 21/07/2009 On-Off
On: retardation = 200 V Off: retardation = 0 V Transfer to Switching of decay trap retardation
124g T½( In) = 3.11(10) s 124m T½( In) = 3.7(2) s
3.44 (13) s 4.06 (07) s Recoil ions 3.52 (12) s
• groundstate & isomer • no significant loss of ions in decay trap
Ions in Ions in cooler trap decay trap
Michaël Tandecki - 21/07/2009 Pulse height and position
on off Position
4.7 cm distribution Pulse height Pulse
Michaël Tandecki - 21/07/2009 Spectrum
Recoil ion energy spectrum
Michaël Tandecki - 21/07/2009 Spectrum interpretation
Fit parameters: • potential offset • isomer contribution • overall scaling • background scaling
Additional parameters: • β- charge state scaling • Gaussian charge state position • Gaussian charge state width
Michaël Tandecki - 21/07/2009 Overview
• Theory
• WITCH set-up
• Physics program
• First results
• Conclusion & Outlook
Michaël Tandecki - 21/07/2009