Status of the miniBETA experiment. Maciej Perkowski KU Leuven: prof. N. Severijns WI group JU Krakow: prof. K. Bodek group

Outline: Physics goals ( β spectrum shape) Fierz term Weak magnetism miniBETA spectrometer Measurement of cosmic muons Single cell efficiency optimization: o Pure Summary/plans for future 2

Physics goals: Precise measurements of the beta spectrum (looking for the influence of Fierz term and weak magnetism). Providing data for groups developing models of electrons traversing through matter (backscattering, transmission through thin foil, …) (e.g. for Geant4). 3

β spectrum shape termEffect Kconstant factor FFermi function MWeak magnetism(~W e ) L0L0 finite size of the nucleus Cnucleonic orbitals Rradiative corrections W 0,e energy pelectron momentum First order approximation + corrections : Fierz term For pure Gammow-Teller transitions: 4

miniBETA spectrometer magnetic field plastic scintillator -Modular reconfigurable drift chamber -beta source inside -energy from curvature of trajectory in mag. field (~0.01T) -trigger from scintillators (start signal for TDC) -operates with light gas at low pressure (~300mbar) -80 hexagonal cells (10 signal planes with 8 wires) -X-Y space resolution 0.5mm - Z position from charge division 5

F S 6 F F F magnetic field plastic scintillator

r = 0 r = amount of total plane multiplicity Single Cell Efficiency (from the binomial distribution): - multiplicity %; %; % Drift chambers suppose to have SCE≈100%... Measurement of cosmic muons TDC spectrum size of the cell TDC (a.u.) 7

Single cell efficiency optimization 8

Pure (mB module) 9

10

Pure (FASTER) 11 „ ”

Pure (FASTER) 12 „ ”

Pure mbar FASTER miniBETA module 13

Summary miniBETA detector is still in testing phase Current status: o ADC range is too small – hardware change in modules required o Artifacts on TDC spectrum (further investigation) o Very low trigger efficiency (tests with 90 Sr, new detectors) o Still not satisfying single cell efficiency (tests with multiple planes, different gas mixtures) 14

Literature N. Severijns, M. Beck and O. Naviliat-Cuncic; “Tests of the standard electroweak model in nuclear beta decay”; Reviews of Modern Physics 78 (2006) , G. Soti; “Search for a tensor component in the weak interaction Hamiltonian”; PhD thesis, 2013 F. Sauli (1977) - Principles of operation of multiwire proportional and drift chambers; CERN-77-09, W. Blum, W. Riegler, L. Rolandi (4 Oct 2008). Particle detection with drift chambers. Springer. Retrieved K. Lojek, K. Bodek, M. Kuzniak; “Ultra-thin gas detector for tracking of low energy electrons”; NIM A, vol. 611,

scattering transmission 17

The general Hamiltonian The general Hamiltonian (Lee and Yang, 1956) C i, C‘ í determine the relative amplitude of each interaction Can be complex  20 parameters describing symmetries C, P and T SymmetryCondition for violation P C i ≠ 0 and C’ i ≠ 0 C (ReC i ≠ 0 and Re C’ i ≠ 0 ) or (ImC i ≠ 0 and Im C’ i ≠ 0 ) T Im(C i /C j ) ≠ 0 or Im( C’ i /C j ) ≠ 0 18

Fierz interference term. such term appears in almost every correlation measurement: For pure Gammow-Teller transitions: 19 Fermi/Gamow-Teller mixing ratio

Helium-isobutan (mB module) 20

Helium-isobutan (mB module) 21

Helium-isobutan (FASTER) 22

Helium-isobutan (FASTER) 23

Helium-isobutan FASTER miniBeta module 24