The particle collider at CERN is revolutionising science.
Particle
physicists announced intriguing evidence for new physics — potentially a new
force of nature — at the Large Hadron Collider (LHC) in March, igniting
worldwide enthusiasm. Now, a new result from CERN's massive particle collider,
which has yet to be peer-reviewed, appears to be bolstering the theory.
The
standard model is our current best theory of particles and forces, and it
accurately represents what we know about the physical material that makes up
the world around us. Despite the fact that the standard model is without a
doubt the most successful scientific theory ever written down, we know it must
be incomplete.
It
is well-known for describing only three of the four fundamental forces: the
electromagnetic force, strong and weak forces, and gravity. It offers no
explanation for the dark matter that, according to astronomy, dominates the
universe, and it can't explain how matter survived the big bang.
Most
physicists believe that there must be more cosmic elements still to be
discovered, and examining a class of fundamental particles known as beauty
quarks is one of the most promising ways to learn more about what's out there.
Beauty
quarks, also known as bottom quarks, are fundamental particles that combine to
form larger particles. Quarks are classified into six flavours: up, down,
weird, charm, beauty/bottom, and truth/top. Protons and neutrons in the atomic
nucleus, for example, are made up of up and down quarks.
Beauty
quarks are unstable, only lasting 1.5 trillionths of a second on average before
disintegrating into other particles. The presence of other fundamental
particles or forces can have a big impact on how beauty quarks decay.
When
a beauty quark decays, the weak force turns it into a collection of lighter
particles, such as electrons. One way a new force of nature can reveal itself
to us is by modifying the frequency with which beauty quarks decay into
different types of particles.
The
data for the March study came from the LHCb experiment, which is one of four
massive particle detectors that records the outcomes of the LHC's
ultra-high-energy collisions. (The letter "b" stands for
"beauty" in LHCb.) It discovered that beauty quarks decayed at
different rates into electrons and their heavier counterparts, muons.
This was surprising because the muon, according to the
conventional model, is essentially a carbon copy of the electron, except that
it is roughly 200 times heavier. This indicates that all forces should exert
the same amount of force on electrons and muons, implying that when a beauty
quark decays into electrons or muons via the weak force, it should do so
equally frequently.
Instead, my colleagues discovered that muon decay
occurs only around 85 percent as frequently as electron decay. If the discovery
is right, the only way to explain such a phenomenon is if a new force of nature
that pushes electrons and muons in opposite directions is interfering with the
disintegration of beauty quarks.
Particle physicists were ecstatic at the outcome. For
decades, scientists have been looking for hints of something other than the
standard model, but despite ten years of effort at the LHC, nothing conclusive
has been discovered. So discovering a new force of nature would be a tremendous
thing, and it could ultimately provide answers to some of modern science's most
perplexing questions.
NEW LARGE HADRON COLLIDER RESULTS
While the outcome was intriguing, it was far from
conclusive. Every measurement has some degree of ambiguity or
"error." There was only around a one-in-1,000 possibility that the
finding was due to a random statistical wobble — or "three-sigma," as
we say in particle physics.
One out of 1,000 may not seem like a lot, but in
particle physics, we make a lot of measurements, so you may expect a tiny
number of outliers to appear by chance.
We'd need to go to five sigma to be confident the
effect is real, which means there's less than a one in a million chance it's
due to a horrible statistical fluke.
We need more data to get there since we need to lower
the amount of the error. One approach to accomplish this is to simply extend
the experiment and record additional decays. The LHCb experiment is currently
being updated so that it will be able to capture collisions at a much faster
rate in the future, allowing for far more exact observations. However, by
looking for comparable types of decays that are more difficult to identify, we
can extract meaningful information from the data we've previously collected.
That is exactly what my coworkers and I have done.
Because all quarks are always bonded up with other quarks to produce larger
particles, we never truly observe beauty quark decays directly. The beauty
quarks were linked with "up" quarks in the March study.
Our findings looked at two decays: one in which the
beauty quarks were associated with "down" quarks and another in which
they were linked with "up" quarks as well. The fact that the pairing
is different shouldn't matter; the degradation going on deep below is the same,
and we'd expect to see the same result if there is a new force out there.
That's exactly what we've witnessed. Muon decays were
only about 70% as common as electron decays this time, but with a greater
inaccuracy, implying that the result differs by around "two sigmas"
from the conventional model (around a two in a hundred chance of being a statistical
anomaly).
This means that, while the result isn't precise enough
to claim clear proof for a new force on its own, it does align extremely
closely with the prior result, adding to the sense that we're on the verge of a
significant breakthrough.
Of course, we must exercise caution. There is still a
long way to go before we can say with certainty that we are witnessing the
effect of nature's fifth force. While preparing for the first run of the
enhanced LHCb experiment, my colleagues are working hard to extract as much
information as possible from the existing data.
In the meantime, additional LHC experiments, as well
as the Belle 2 experiment in Japan, are getting closer to the same results.
It's thrilling to imagine that in the coming months or years, a new window on
our universe's most fundamental constituents will be opened.
0 Comments