Abstract
Nuclear beta decays play an important role in uncovering the nature of the weak interaction. The weak magnetism (WM) form factor,
b
WM
, is generally a small correction to the beta decay ...rate that arises at first order as an interference term between the dominant Gamow-Teller and the magnetic dipole contributions to the weak current. This form factor is still poorly known for nuclei with higher atomic number. We performed a careful analysis of the measured beta spectrum shape for Gamow-Teller transitions in
114
In and
32
P nuclei. The precision spectrum shape measurements were carried out using the miniBETA spectrometer consisting of a low-mass, low-
Z
multi-wire gas tracker and a plastic scintillator energy detector. The preliminary results for the weak magnetism extraction for
114
In and
32
P nuclei are presented.
Neutron and nuclear beta decay correlation coefficients are linearly sensitive to the exotic scalar and tensor interactions that are not included in the Standard Model (SM). The proposed experiment ...will measure simultaneously 11 neutron correlation coefficients (
a
,
a
,
B
,
D
,
H
,
L
,
N
,
R
,
S
,
U
,
V
) where 7 of them (
H
,
L
,
N
,
R
,
S
,
U
,
V
) depend on the transverse electron polarization – a quantity that vanishes for the SM weak interaction. The neutron decay correlation coefficients
H
,
L
,
S
,
U
,
V
were never attempted experimentally before. The expected ultimate sensitivity of the proposed experiment that currently takes off on the cold neutron beamline PF1B at the Institut Laue-Langevin, Grenoble, France, is comparable to that of the planned electron spectrum shape measurements in neutron and nuclear β decays but offers completely different systematics and additional sensitivity to imaginary parts of the scalar and tensor couplings.
BRAND—A detection system for β-decay correlation measurement Dhanmeher, K.; Bodek, K.; Choi, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
March 2023, Letnik:
1048
Journal Article
Recenzirano
The BRAND experiment aims at the search of Beyond Standard Model (BSM) physics via measurement of exotic components of the weak interaction. For this purpose, eleven correlation coefficients of ...neutron β-decay will be measured simultaneously. The BRAND detection system is oriented for the registration of charged products of β-decay of polarized, free neutrons. With the measurement of the four-momenta of electron and proton, the complete kinematic of the decay will be determined. Moreover, the transverse spin component of the electron, which is the crucial observable to probe BSM exotic components of weak interaction, will be measured via Mott scattering. The electron detection system features both tracking and energy measurement capability. It is also responsible for the determination of the electron spin orientation. A challenging detection of low-energy protons from the β-decay is performed with a system, which involves the acceleration and subsequent conversion of protons into bunches of electrons. To test the feasibility of the proposed experimental techniques, a small-scale prototype setup was installed at the cold neutron beam facility PF1B at the Laue-Langevin Institute (ILL) in Grenoble, France. In this contribution, the preliminary results of the commissioning run are presented with an emphasis on the performance of individual parts of the detection system.
Neutron and nuclear beta decay correlation coefficients are sensitive to the exotic scalar and tensor interactions that are not included in the Standard Model (SM). The proposed experiment BRAND will ...measure simultaneously seven neutron correlation coefficients:
H
,
L
,
N
,
R
,
S
,
U
and
V
that depend on the transverse electron polarization – a quantity which vanishes in the SM. Five of these correlations:
H
,
L
,
S
,
U
and
V
were never attempted experimentally before. The expected impact of the proposed experiment is comparable to that of frequently measured “traditional” correlation coefficients (
a
,
b
,
A
,
B
,
D
) but offers completely different systematics and additional sensitivity to imaginary parts of the scalar and tensor couplings. In order to demonstrate the feasibility of the challenging techniques such as the event-by-event decay kinematics reconstruction together with the electron polarimetry a test setup was installed at the cold neutron beam line PF1B at the Laue-Langevin Institute, Grenoble, France. In this contribution, the results of the first run as well as plans for the run in Autumn 2021 will be discussed.
Neutron and nuclear beta decay correlation coefficients are sensitive to the exotic scalar and tensor interactions that are not included in the Standard Model (SM). The proposed experiment BRAND will ...measure simultaneously seven neutron correlation coefficients: H, L, N, R, S, U and V that depend on the transverse electron polarization – a quantity which vanishes in the SM. Five of these correlations: H, L, S, U and V were never attempted experimentally before. The expected impact of the proposed experiment is comparable to that of frequently measured “traditional” correlation coefficients (a, b, A, B, D) but offers completely different systematics and additional sensitivity to imaginary parts of the scalar and tensor couplings. In order to demonstrate the feasibility of the challenging techniques such as the event-by-event decay kinematics reconstruction together with the electron polarimetry a test setup was installed at the cold neutron beam line PF1B at the Laue-Langevin Institute, Grenoble, France. In this contribution, the results of the first run as well as plans for the run in Autumn 2021 will be discussed.
Spectrum shape measurements in nuclear $\beta$ decay can be used to test
physics beyond the Standard Model with results being complementary to
high-energy collider experiments. In particular, Beyond ...Standard Model
sensitivity of the weak interaction is expressed through the so-called Fierz
interference term. Additionally, the $\beta$ spectrum shape is a useful tool to
probe Standard Model effects, among which the most prominent is \textit{weak
magnetism}, a higher-order recoil correction induced by nuclear pion exchange.
To study effects in the $\beta$ spectrum shape at a precision level competitive
with the LHC, a new spectrometer was designed and built. It consists of a 3D
low-pressure gas electron tracker and a plastic scintillator used for
triggering the data acquisition and recording the $\beta$ particle energy. In
this Letter, the results from $\beta$ spectrum shape measurements on the
allowed Gamow-Teller transition $^{114}\text{In} \rightarrow ^{114}\text{Sn}$
are presented, including a first extraction of the weak magnetism form factor
in the high nuclear mass range and a new estimate of the $90\%$ confidence
interval for the Fierz interference term.
For identification and 3D-tracking of low-energy electrons a new type of gas-based detector was designed that minimizes scattering and energy loss. The current version of the detector is a ...combination of a plastic scintillator, serving as a trigger source and energy detector, and a hexagonally structured multi-wire drift chamber (MWDC), filled with a mixture of helium and isobutane gas. The drift time information is used to track particles in the plane perpendicular to the wires, while a charge division technique provides spatial information along the wires. The gas tracker was successfully used in the miniBETA project as a beta spectrometer for a measurement of the weak magnetism form factor in nuclear beta decay. The precision of the three-dimensional electron tracking, in combination with low-mass, low-Z materials and identification of backscattering from scintillator, facilitated a reduction of the main systematics effects. At certain conditions, a spatial resolution better than 0.5 mm was obtained in the plane perpendicular to the wires, while resolutions of about 6 mm were achieved along wires. Thanks to precise tracking information, it is possible to eliminate electrons and other particles not originating from the desired decay with high efficiency. Additionally, using the coincidence between MWDC and scintillator, background from gamma emission typically accompanying radioactive decays, was highly suppressed. An overview of different event topologies is presented together with the tracker's ability to correctly recognize them. The analysis is supported by Monte Carlo simulations using Geant4 and Garfield++ packages. Finally, the preliminary results from the 114In spectrum study are presented.
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