Neutrinos detected in particle collider for first time at CERN
For the first time, neutrinos produced in a particle accelerator have been detected.
A general view of the Large Hadron Collider (LHC) experiment is
seen during a media visit at the Organization for Nuclear Research
(CERN) in the French village of Saint-Genis-Pouilly near Geneva in
Switzerland, July 23, 2014 (photo credit: REUTERS/PIERRE ALBOUY)
Researchers at the ForwArd Search ExpeRiment (FASER) at CERN
have detected neutrino candidates in the first such detection in a
particle accelerator, publishing a paper on the breakthrough in the
peer-reviewed journal Physical Review D on Wednesday.
Neutrinos
are the most abundant fundamental particles that have mass in the
universe and have been detected from many sources, including the sun and
cosmic-ray interactions. They are among the least understood particles
in the standard model of particle physics, with neutrinos produced
within a particle collider having never been directly detected.
Collider neutrinos are produced at high energies, at which neutrino interactions have not been well studied. Being able to detect and study collider neutrinos could shed light on the particles, as it would allow scientists to study the particles under highly controlled conditions.
“These neutrinos will have the highest energies yet of man-made
neutrinos, and their detection and study at the LHC will be a milestone
in particle physics, allowing researchers to make highly complementary
measurements in neutrino physics,” said Jamie Boyd, co-spokesperson for
the FASER experiment, in 2019, according to CERN.
“What’s more, FASER
may also pave the way for neutrino programs at future colliders, and the
results of these programs could feed into discussions of proposals for
much larger neutrino detectors.”
The
FASER researchers, led by physicists from the University of California,
Irvine, observed six neutrino interactions during a pilot run of a
compact emulsion detector at the Large Hadron Collider (LHC) at CERN in
2018, shortly before the LHC shut down for maintenance and upgrades,
according to UC Irvine News.
The detector was made up of lead and tungsten plates alternated with
layers of emulsion. During particle collisions at the LHC, some of the
neutrinos produced smash into nuclei in the dense metals, creating
particles that travel through the emulsion layers and create marks that
can be seen following processing. The marks can provide information
about the energies of the particles helping scientists understand what
kind of particles they were.
Study co-author Jonathan Feng, UCI Distinguished Professor of
physics & astronomy and co-leader of the FASER Collaboration,
explained to UC Irvine News that "this significant breakthrough is a
step toward developing a deeper understanding of these elusive particles
and the role they play in the universe.”
The
discovery gave the FASER team two crucial pieces of information,
according to Feng: It verified that the position of the device in the
LHC is the right location for detecting collider neutrinos and
demonstrated that an emulsion detector is effective in observing
neutrino interactions.
The
result of the team's work has a statistical significance of 2.7
standard deviations, just below the three standard deviations required
to claim evidence of a particle or process in particle physics.
“Having
verified the effectiveness of the emulsion detector approach for
observing the interactions of neutrinos produced at a particle collider,
the FASER team is now preparing a new series of experiments with a full
instrument that’s much larger and significantly more sensitive,” said
Feng.
The device
which led to the discovery is only a pilot version of a final much
larger device that will begin operations once the LHC begins running
again in 2022. The final device will weigh over 2,400 pounds, while the
pilot detector weighs only about 64 pounds. The final device will also
be much more reactive and able to differentiate among neutrino
varieties.
According
to CERN, the FASER team expects to observe about 20,000 collider
neutrino interactions once the full-fledged detector becomes active in
the next LHC run, from 2022 to 2024.
The
final device will also be used to investigate the dark matter at the
LHC, with researchers hoping to detect dark photons, which would help
show how dark matter interacts with normal atoms and other matter in the
universe through nongravitational forces.
The Scattering and Neutrino Detector (SND@LHC) will also work to detect
and study neutrinos once the accelerator starts up again in 2022, but
from a different angle than that of FASERν. The detector will also be
able to search for new particles, very weakly interacting particles not predicted by the Standard Model which could make up dark matter.
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