- 3365 - NEUTRINOS - the ghost particle? Millions of barely perceptible “ghost” particles, “neutrinos”, fly through your body every second. Neutrinos have near zero mass and no electric charge. But, they hold secrets that could unlock the very origins of matter itself from the universe’s first moments.
--------------------- 3365 - NEUTRINOS - the ghost particle?
- We all know our world is made of atoms. Atoms are made of electrons and protons. They are also made of “neutrinos’ which is what this review is about. Electrons are fundamental particles. Protons are not fundamental. They are made of even more fundamental particles called quarks and gluons. ( Request my Review about Quarks or about Electrons)
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- If you add energy to electrons and neutrinos they become muons and muon neutrinos. If you add even more energy they become taus and tau neutrinos. (This Review is about those three varieties of neutrinos)
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- The neutrino particles are incredibly difficult to detect. However, scientists have recently shown that particle colliders, like those at CERN, can be used to detect these mystery particles. For the “tau neutrino“, in particular, this could bring their total detected count from only a handful to thousands.
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- Thousands of neutrinos are being created at CERN’s large hadron collider (LHC) every day, but scientists are only just now attempting to detect them.
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- CERN‘s collider is slamming beams of “hadron” particles into each other at nearly the speed of light. As a result of these collisions, subatomic particles such as quarks or “bosons” are shed and caught by detectors like “ATLAS“. Neutrinos have always been a part of this process, but until this point, there haven’t been any experiments designed to detect them.
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- Hadrons are subatomic particles that are affected by the Strong Atomic Force. The Hadrons are composed of Quarks.
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- Bosons are particles with zero and integral spin, such as photons. Photons carry the electromagnetic force. Gluons the Strong Force , and W-Z Bosons the Weak Force.
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- Part of the problem is that CERN’s LHC uses magnets to direct particles around a circular collision path with detectors dotted around these curves. These magnetic traffic signs don’t impact chargeless particles like neutrinos. As a result, neutrinos shoot off the edge of the detector path.
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- This off shoot may be a way to capture these super-symmetric particles. The experiments first results released November, 2021, have confirmed the detection of six neutrinos at the LHC.
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- A neutrino is an incredibly light (at least 6 million times lighter than an electron). It is a particle that has no charge and nearly no interaction with matter as we know it. That’s why these particles can fly right through us without us noticing.
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- High-energy nuclear physics happening at the heart of our sun rain neutrinos down on Earth, providing most of the ones we can detect. But these tiny particles can also be created from atomic decay, cosmic rays, and the collision of Earthly particle beams. While neutrinos may be abundant, they’re difficult to catch.
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- Some experiments studying neutrinos include “Fermilab’s MiniBooNE“, the “IceCube” detector in Antarctica, and the “Super-Kamiokande” detector in Japan. The “FASER“, experiments focus on detecting the constituent parts of a neutrino that it decays into after striking an atomic nucleus just right.
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- The FASER experiment compared to the resource requirements of its predecessors (e.g., 50,000 tons of water in the case of Super-Kamiokande), FASER is a pretty lean experiment. Cobbled together from leftover parts at CERN, the first iteration of FASER weighs in at only 64 pounds .
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- By 2022 a full-size version of FASER will be in place weighing more than 2,400 pounds and be overall more powerful and sensitive than the smaller pilot version.
FASER is optimally positioned in a forgotten section of the LHC to detect flung-off neutrinos.
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- FASER works the same way using technology reminiscent of film photography called “emulsion detection” to catch neutrinos. Plates of lead and tungsten are sandwiched together with layers of emulsions, a light-sensitive goop.
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- Stray neutrinos that LHC strike these plates decay into new particles. These particles then leave marks in the emulsion layers that physicists can develop like a photo. Based on the energies of these marks, researchers can tell which flavor of neutrino is present, tau, muon, or electron, and whether or not it was a neutrino or anti-neutrino
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- Releasing a proton and anti-neutrino is a process called “beta minus decay“, neutrinos will also release either a muon, tau, or electron.
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- Of these flavors, tau neutrinos have proven to be the rarest and most challenging to detect. Before the FASER experiment, only 10 tau neutrinos had ever been observed, with the first detection occurring only twenty-one years ago at Fermilab.
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- In addition to differentiating between different flavors of neutrinos, FASER will also be able to distinguish between neutrinos and anti-neutrinos striking its detector. An anti-neutrino is a form of the original neutrino with an opposite charge.
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- Because both neutrinos and anti-neutrinos are electromagnetically chargeless, this opposite charge refers to the particles’ lepton number instead, a kind of quantum number used to describe the properties of subatomic particles.
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- Scientists aren’t entirely sure what exactly separates a neutrino from an anti-neutrino. However, studying more anti-neutrinos directly using experiments like FASER will be a big step toward answering this question.
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- Beginning in 2022, the FASER team says they expect to start capturing 10,000 or more neutrino signals using their detector. This data could be a huge step forward when it comes to answering existential questions in physics, like where matter comes from and why so much of it is dark matter.
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- The “Large Hadron Collider” (LHC), fired up ten years ago. Aside from the spectacular discovery of the Higgs boson, the project has failed to yield any clues as to what might lie beyond the standard model of particle physics, our current best theory of the micro-cosmos.
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- The standard model has withstood every experimental test thrown at it since it was assembled in the 1970s, so to claim that we’re finally seeing something it can’t explain requires extraordinary evidence.
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- The standard model describes nature on the smallest of scales, comprising fundamental particles known as leptons (such as electrons) and quarks (which can come together to form heavier particles such as protons and neutrons) and the forces they interact with.
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- There are many different kinds of quarks, some of which are unstable and can decay into other particles. The new result relates to an experimental anomaly that was first hinted at in 2014, when LHC physicists spotted “beauty” quarks decaying in unexpected ways.
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- Beauty quarks appeared to be decaying into leptons called “muons” less often than they decayed into electrons. This is strange because the muon is in essence a carbon-copy of the electron, identical in every way except that it’s around 200 times heavier.
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- You would expect beauty quarks to decay into muons just as often as they do to electrons. The only way these decays could happen at different rates is if some never-before-seen particles were getting involved in the decay and tipping the scales against muons.
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- In 2019, LHCb performed the same measurement of beauty quark decay again but with extra data taken in 2015 and 2016. But things weren’t much clearer than they’d been five years earlier. Today’s result doubles the existing dataset by adding the sample recorded in 2017 and 2018. To avoid accidentally introducing biases, the data was analysed “blind” The scientists couldn’t see the result until all the procedures used in the measurement had been tested and reviewed.
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- When the result came up on the screen, the anomaly was still there – around 85 muon decays for every 100 electron decays, but with a smaller uncertainty than before. The uncertainty of the result is now over “three sigma”. There is only around a one in a thousand chance that the result is a random fluke of the data. Conventionally, particle physicists call anything over three sigma “evidence”. However, we are still a long way from a confirmed “discovery” or “observation”, that would require five sigma.
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- One possibility is a fundamental particle called a “Z prime”, in essence a carrier of a brand new force of nature. This force would be extremely weak, which is why we haven’t seen any signs of it until now, and would interact with electrons and muons differently.
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- Another option is the hypothetical “leptoquark”, a particle that has the unique ability to decay to quarks and leptons simultaneously and could be part of a larger puzzle that explains why we see the particles that we do in nature.
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- One exciting possibility is that we might be able to detect the new particles responsible for the effect being created directly in the collisions at the LHC. Meanwhile, the “Belle II” experiment in Japan should be able to make similar measurements.
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- If what we are seeing is really the harbinger of some new fundamental particles then it will finally be the breakthrough that physicists have been yearning for decades. We will have finally seen a part of the larger picture that lies beyond the standard model, which ultimately could allow us to unravel any number of established mysteries.
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- These include the nature of the invisible dark matter that fills the universe or the nature of the Higgs boson. It could even help theorists unify the fundamental particles and forces. Or, perhaps it could be pointing at something we have never even considered.
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- Extraordinary claims require extraordinary evidence. Only time and hard work will tell if we have finally seen the first glimmer of what lies beyond our current understanding of particle physics.
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December 1, 2021 NEUTRINOS - the ghost particle? 3365
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