Amplified search for new forces
Special setup uses polarized rubidium and xenon as transmitter and
receiver system for exotic fields

Date:
February 1, 2023
Source:
Johannes Gutenberg Universitaet Mainz
Summary:
In the search for new forces and interactions beyond the Standard
Model, an international team of researchers has now taken a good
step forward.

The researchers are using an amplification technique based
on nuclear magnetic resonance. They use their experimental
setup to study a particular exotic interaction between spins:
a parity-violating interaction mediated by a new hypothetical
exchange particle, called a Z' boson, which exists in addition to
the Z boson mediating the weak interaction in the standard Model.


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FULL STORY ==========================================================================
In the search for new forces and interactions beyond the Standard Model,
an international team of researchers involving the PRISMA+ Cluster of Excellence at Johannes Gutenberg University Mainz (JGU) and the Helmholtz Institute Mainz has now taken a good step forward. The researchers, among
them Prof. Dr. Dmitry Budker, are using an amplification technique based
on nuclear magnetic resonance. In their work recently published in Science Advances, they use their experimental setup to study a particular exotic interaction between spins: a parity-violating interaction mediated by a
new hypothetical exchange particle, called a Z' boson, which exists in
addition to the Z boson mediating the weak interaction in the standard
Model. In the current setup, they were unable to detect this particle,
but they were able to increase the sensitivity by five orders of magnitude compared to previous measurements. This allows to set constraints on the strength of the interaction of the new exchange particle with Standard
Model particles that are complementary to astrophysical observations
and open up a previously inaccessible region.


========================================================================== Numerous theories predict the existence of exotic interactions beyond
the Standard Model. They differ from the four known interactions and
are mediated by previously unknown exchange particles. In particular, parity-violating interactions, i.e., where mirror-symmetric is broken,
are currently experiencing a special interest. On the one hand, because
this would immediately indicate the particular type of new physics we are dealing with, and on the other hand, because their effects are easier
to separate from spurious systematic effects, that usually do not show mirror-symmetry breaking.

"In the current article, we take a close look at such an interaction
between the spins of electrons and the spins of neutrons, mediated by a hypothetical Z' boson. In a mirrored world, this interaction would lead
to a different result; parity is violated here," explains Dmitry Budker.

This "result" looks like this: The electron spins within a source are
all aligned in one direction, i.e. polarized, and the polarization is continuously modulated, thus creating an exotic field that is perceived
as a magnetic field and can be measured using a sensor. In a mirrored
world, the exotic field would not point in the same direction as would
be expected in a "real" mirror image, but in the opposite direction:
the parity of this interaction is violated.

SAPPHIRE -- the new gem in the search for new physics "Spin Amplifier
for Particle PHysIcs REsearch" -- SAPPHIRE for short -- is what the
researchers have named their setup, which is based on the two elements
rubidium and xenon. They have already used this technique in a similar
form to search for other exotic interactions and for dark matter fields.

Specifically, in the experimental search for exotic spin-spin
interactions, two chambers filled with the vapor of one of the two
elements are positioned in close proximity to each other: "In our
experiment, we use polarized electron spins of rubidium-87 atoms as a
spin source and polarized neutron spins of the noble gas xenon, or more precisely the isotope xenon-129, as a spin sensor," says Dmitry Budker.

The trick is that the special structure and the polarized xenon atoms
in the spin sensor initially amplify the field generated in the rubidium source: thus, the effect triggered by a potential exotic field would be
a factor of 200 larger. Now the principle of nuclear magnetic resonance
comes into play, i.e.

the fact that nuclear spins react to magnetic fields that oscillate at
a certain resonance frequency. Rubidium-87 atoms are also present in a
small proportion in the sensor cell for this purpose. They in turn act
as an extremely sensitive magnetometer to determine the strength of the resonance signal.

The detection of such an exotic field in the right frequency range would
then be the clue to the new interaction we are looking for. Other special experimental details ensure that the setup is particularly sensitive in
the frequency range of interest and less sensitive to spurious effects
from other magnetic fields that inevitably also arise in the experiment.

"All in all, this is a rather intricate setup that has required a
careful design and calibration. It is highly rewarding to work on such challenging and interesting problems with our long-time collaborators
from the University of Science and Technology (USTC) in Hefei, China
who hosted the experiment," reports Dmitry Budker.

After successful proof-of-principle, the scientists started the first
series of measurements to search for the exotic interaction. Although
they have not yet been able to find a corresponding signal after 24 hours
of measurements, the five orders of magnitude increase in sensitivity
has enabled them to set constraints on the strength of the new exchange particle's interaction with Standard Model particles. Further optimization could even improve the experimental sensitivity to the special exotic interaction by another eight orders of magnitude. This makes it seem
possible to use the ultrasensitive SAPPHIRE setup to discover and study
a new physics with potential Z' bosons.

* RELATED_TOPICS
o Matter_&_Energy
# Spintronics # Physics # Quantum_Physics #
Medical_Technology # Detectors # Nuclear_Energy #
Materials_Science # Energy_and_Resources
* RELATED_TERMS
o Superconducting_Super_Collider o Particle_physics o Quark o
Neutrino o Magnetic_resonance_imaging o Electron o Model_rocket
o Subatomic_particle

========================================================================== Story Source: Materials provided by
Johannes_Gutenberg_Universitaet_Mainz. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Yuanhong Wang, Ying Huang, Chang Guo, Min Jiang, Xiang Kang,
Haowen Su,
Yushu Qin, Wei Ji, Dongdong Hu, Xinhua Peng, Dmitry Budker. Search
for exotic parity-violation interactions with quantum spin
amplifiers.

Science Advances, 2023; 9 (1) DOI: 10.1126/sciadv.ade0353 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/02/230201134227.htm

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