- 3848
- PHYSICS -
beyond the Standard Model? The
Standard Model of Physics explains the fundamental physics of how the universe
works. It has endured over 50 trips around the sun despite experimental
physicists constantly probing for cracks in the model's foundations.
----------------- 3848 - PHYSICS - beyond the Standard Model?
- With few exceptions, it has stood up to
this scrutiny, passing experimental test after experimental test with flying
colors. But this wildly successful model has conceptual gaps that suggest there
is a bit more to be learned about how the universe works.
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- Neutrinos represent three of the 17
fundamental particles in the Standard Model. They zip through every person on Earth
at all times of day. In 2021, physicists
around the world ran a number of experiments that probed the Standard Model.
Teams measured basic parameters of the model more precisely than ever before.
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- Others investigated the fringes of
knowledge where the best experimental measurements don't quite match the
predictions made by the Standard Model.
-
- And finally, groups built more powerful
technologies designed to push the model to its limits and potentially discover
new particles and fields. If these efforts pan out, they could lead to a more
complete theory of the universe in the future.
-
- The Standard Model of physics allows
scientists to make incredibly accurate predictions about how the world works,
but it doesn’t explain everything. The
Standard Model of physics allows scientists to make incredibly accurate
predictions about how the world works, but it doesn't explain everything. In
1897, J.J. Thomson discovered the first fundamental particle, the electron,
using nothing more than glass vacuum tubes and wires. More than 100 years
later, physicists are still discovering new pieces of the Standard Model.
-
- The Standard Model is a predictive
framework that does two things. First, it explains what the basic particles of
matter are. These are things like electrons and the quarks that make up protons
and neutrons.
-
- Second, it predicts how these matter
particles interact with each other using "messenger particles". These
are called bosons, they include photons and the famous Higgs boson, and they
communicate the basic forces of nature. The Higgs boson wasn't discovered until
2012 after decades of work at CERN, the huge particle collider in Europe.
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- The Standard Model is incredibly good at
predicting many aspects of how the world works, but it does have some
holes. Notably, it does not include any
description of gravity. While Einstein's theory of General Relativity describes
how gravity works, physicists have not yet discovered a particle that conveys
the force of gravity.
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- A proper "Theory of Everything"
would do everything the Standard Model can, but also include the messenger
particles that communicate how gravity interacts with other particles.
-
- Another thing the Standard Model can't do
is explain why any particle has a certain mass, physicists must measure the
mass of particles directly using experiments. Only after experiments give
physicists these exact masses can they be used for predictions. The better the
measurements, the better the predictions that can be made.
-
- Recently, physicists on a team at CERN
measured how strongly the Higgs boson feels itself. Another CERN team also measured the Higgs
boson's mass more precisely than ever before.
And, there was also progress on
measuring the mass of neutrinos. Physicists know neutrinos have more than zero
mass but less than the amount currently detectable.
-
- Projects like the “Muon g-2 experiment”
highlight discrepancies between experimental measurements and predictions of
the Standard Model that point to problems somewhere in the physics.
-
- In April 2021, members of the Muon g-2
experiment at Fermilab announced their first measurement of the magnetic moment
of the muon. The muon is one of the fundamental particles in the Standard Model,
and this measurement of one of its properties is the most accurate to date.
-
- The reason this experiment was important
was because the measurement didn't perfectly match the Standard Model
prediction of the magnetic moment. Basically, muons don't behave as they
should. This finding could point to undiscovered particles that interact with
muons.
-
- Simultaneously, in April 2021, physicists
showed how they used a mathematical method called “Lattice QCD” to precisely
calculate the muon's magnetic moment. Their theoretical prediction is different
from old predictions, still works within the Standard Model and, importantly,
matches experimental measurements of the muon.
-
- New tools will help physicists search for
dark matter and other things that could help explain mysteries of the
universe. Physicists must swing between
crafting the mind-bending ideas about reality that make up theories and
advancing technologies to the point where new experiments can test those
theories. 2021 was a big year for advancing the experimental tools of physics.
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- First, the world's largest particle
accelerator, the Large Hadron Collider at CERN, was shut down and underwent
some substantial upgrades. Physicists just restarted the facility in October,
and they plan to begin the next data collection run in May 2022.
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- The upgrades have boosted the power of the
collider so that it can produce collisions at 14 TeV, up from the previous
limit of 13 TeV. This means the batches of tiny protons that travel in beams
around the circular accelerator together carry the same amount of energy as an
800,000-pound passenger train traveling at 100 mph. At these incredible
energies, physicists may discover new particles that were too heavy to see at
lower energies.
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- Some other technological advancements were
made to help the search for dark matter. Many astrophysicists believe that dark
matter particles, which don't currently fit into the Standard Model, could
answer some outstanding questions regarding the way gravity bends around stars,
called gravitational lensing, as well as the speed at which stars rotate in
spiral galaxies.
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- Projects like the “Cryogenic Dark Matter
Search” have yet to find dark matter particles, but the teams are developing
larger and more sensitive detectors to be deployed in the near future. New detectors like Hyper-Kamiokand, and DUNE.
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- Using these detectors, scientists will
hopefully be able to answer questions about a fundamental asymmetry in how
neutrinos oscillate. They will also be used to watch for proton decay, a
proposed phenomenon that certain theories predict should occur.
-
- 2021 highlighted some of the ways the
Standard Model fails to explain every mystery of the universe. But new
measurements and new technology are helping physicists move forward in the
search for the “Theory of Everything”.
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January 27, 2022 PHYSICS -
beyond the Standard Model?
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--------------------- --- Monday, January 30, 2023 ---------------------------
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