status of the minibeta experiment. maciej perkowski ku leuven: prof. n. severijns wi group ju...
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Status of the miniBETA experiment.
Maciej PerkowskiKU Leuven: prof. N. Severijns WI groupJU Krakow: prof. K. Bodek group
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Outline:
โข Physics goals (ฮฒ spectrum shape)โข Fierz termโข Weak magnetism
โข miniBETA spectrometer
โข Measurement of cosmic muons
โข Single cell efficiency optimization:o Pure isobutane @300mbar
โข Summary/plans for future
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Physics goals:
โข Precise measurements of the beta spectrum (looking for the influence of Fierz term and weak magnetism).
โข Providing data for groups developing models of electrons traversing through matter (backscattering, transmission through thin foil, โฆ) (e.g. for Geant4).
4ฮฒ spectrum shape
term Effect
K constant factor
F Fermi function
M Weak magnetism(~We )
L0 finite size of the nucleus
C nucleonic orbitals
R radiative corrections
W0,e energy
p electron momentum
First order approximation
+ corrections :
๐โฒ=ยฑ ๐พ๐๐๐
โ (๐ถ๐+๐ถ๐โฒ
๐ถ๐ด)
Fierz term
For pure Gammow-Teller transitions:
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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
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F
S
FF
F
magnetic field
plastic scintillator
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r = 0 r =
amo
un
t o
f to
tal
plane multiplicity
Single Cell Efficiency (from the binomial distribution): - multiplicity 3 - 48%;
4 - 45%; 5 - 40%
Drift chambers suppose to have SCEโ100% ...
Measurement of cosmic muons
TDC spectrum
size of the cell
TDC (a.u.)
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Single cell efficiency optimization
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Pure isobutane @300mbar (mB module)
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Pure isobutane @300mbar (mB module)
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Pure isobutane @300mbar (FASTER)
๐=๐ต
๐ต ๐๐๐๐๐๐๐๐๐๐
โ โ
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Pure isobutane @300mbar (FASTER)
๐=๐ต
๐ต ๐๐๐๐๐๐๐๐๐๐
โ โ
13Pure isobutane@300 mbar
๐=๐ต
๐ต ๐๐๐๐๐๐๐๐๐๐
FASTER
miniBETA module
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Summary
โข miniBETA detector is still in testing phase
โข Current status:o ADC range is too small โ hardware change in modules
requiredo Artifacts on TDC spectrum (further investigation)o Very low trigger efficiency (tests with 90Sr, new
detectors)o Still not satisfying single cell efficiency (tests with
multiple planes, different gas mixtures)
THANK YOU
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Literature
โข N. Severijns, M. Beck and O. Naviliat-Cuncic; โTests of the standard electroweak model in nuclear beta decayโ; Reviews of Modern Physics 78 (2006) 991-1040,
โข G. Soti; โSearch for a tensor component in the weak interaction Hamiltonianโ; PhD thesis, 2013
โข F. Sauli (1977) - Principles of operation of multiwire proportional and drift chambers; CERN-77-09,
โข W. Blum, W. Riegler, L. Rolandi (4 Oct 2008). Particle detection with drift chambers. Springer. Retrieved 2012-02-28.
โข K. Lojek, K. Bodek, M. Kuzniak; โUltra-thin gas detector for tracking of low energy electronsโ; NIM A, vol. 611, 2009
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scatteringtransmission
18The general Hamiltonian(Lee and Yang, 1956)
Ci , Cโรญ determine the relative amplitude of each interaction
Can be complex 20 parameters describing symmetries C, P and T
Symmetry Condition for violation
P Ci โ 0 and Cโi โ 0
C (ReCi โ 0 and ReCโi โ 0) or(ImCi โ 0 and ImCโi โ 0)
T Im(Ci /Cj ) โ 0 or Im(Cโi /Cj ) โ 0
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Fierz interference term.
such term appears in almost every correlation measurement:
For pure Gammow-Teller transitions:
๐ป ๐ฝ=๐ป ๐ฝ๐๐โ (1+๐โฒ )
๐พ=โ1โ๐ผ2๐ 2
๐=๐๐บ๐ ๐ถ๐ด
๐๐น๐ถ๐๐โฒ=ยฑ
๐พ๐๐
๐ธ๐
11+๐ 2 [โ (๐ถ๐+๐ถ๐
โฒ
๐ถ๐)+๐ 2โ (๐ถ๐+๐ถ๐
โฒ
๐ถ๐ด)]
Fermi/Gamow-Teller mixing ratio
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Helium-isobutan 70/30 @300mbar (mB module)
๐=๐๐ดฮฉ๐ก
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Helium-isobutan 70/30 @300mbar (mB module)
๐=๐๐ดฮฉ๐ก
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Helium-isobutan 70/30 @300mbar (FASTER)
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Helium-isobutan 70/30 @300mbar (FASTER)
๐=๐๐ดฮฉ๐ก
๐=๐
๐๐ก๐๐๐ฮฉ๐๐ฃ๐๐๐
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Helium-isobutan 70/30 @300mbar
๐=๐
๐๐ก๐๐๐ฮฉ๐๐ฃ๐๐๐
FASTER
miniBeta module