- 3670 - HIGGS BOSON - ten years since first discovery? - It has been ten years since the Higgs boson’s discovery in 2012. But many of its properties remain mysterious.
---------------- 3670 - HIGGS BOSON - ten years since first discovery?
- On July, 2012, physicists at CERN, Europe’s particle-physics laboratory ( the LHC), declared victory in their long search for the Higgs boson. The elusive particle’s discovery filled in the last gap in the standard model which is physicists’ best description of particles and forces. This opened a new window on physics by providing a way to learn about the Higgs field, which involves a previously unstudied kind of interaction that gives particles their masses.
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- We have learned the Higgs boson’s mass to be 125 billion electronvolts. In the 1960s, physicist Peter Higgs and others theorized that what’s now called a Higgs field could explain why the photon has no mass and the W and Z bosons, which carry the weak nuclear force that is behind radioactivity, are heavy for mass of subatomic particles.
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- The special properties of the Higgs field allowed the same mathematics to account for the masses of all particles, and it became an essential part of the standard model. But the theory made no predictions about the boson’s mass and therefore when the LHC might be able to produce it.
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- The LHC started gathering data in its search for the Higgs in 2009, and both ATLAS and CMS, the accelerator’s general-purpose detectors, saw it in 2012. The detectors observed the decay of just a few dozen Higgs bosons into photons, Ws and Zs, which revealed a bump in the data at 125 billion electronvolts (GeV), about 125 times the mass of the proton.
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- The Higgs’ mass of 125 GeV puts it in a sweet spot that means the boson decays into a wide range of particles at a frequency high enough for LHC experiments to observe.
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- The Higgs boson is a spin-zero particle. Spin is an intrinsic quantum-mechanical property of a particle, often pictured as an internal bar magnet. All other known fundamental particles have a spin of 1/2 or 1, but theories predicted that the Higgs should be unique in having a spin of zero. It was also correctly predicted to have zero charge.
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- In 2013, CERN experiments studied the angle at which photons produced in Higgs boson decays flew out into the detectors, and used this to show with high probability that the particle had zero spin.
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- The Higgs’ properties rule out some theories that extend the standard model. The Standard Model theory breaks down at high energies and can’t explain key observations, such as the existence of dark matter or why there is so little antimatter in the Universe. Physicists have come up with extensions to the model that account for these.
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- Discovering the Higgs boson’s 125-GeV mass has made some of these theories less attractive. The Higgs boson interacts with other particles as the standard model predicts. According to the standard model, a particle’s mass depends on how strongly it interacts with the Higgs field.
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- Although the boson, which is like a ripple in the Higgs field, doesn’t have a role in that process, the rate at which Higgs bosons decay into or are produced by any other given particle provides a measure of how strongly that particle interacts with the field.
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- LHC experiments have confirmed that, at least for the heaviest particles, produced most frequently in Higgs decays, “mass” is proportional to interaction with the field, a remarkable win for a 60-year-old theory.
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- The Universe is stable, but only just stable. Calculations using the mass of the Higgs boson suggest that the Universe might be only temporarily stable, and there’s a vanishingly small chance that it could shift into a lower energy state with catastrophic consequences.
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- Unlike other known fields, the Higgs field has a lowest energy state above zero even in a vacuum, and it pervades the entire Universe. According to the standard model, this ‘ground state’ depends on how particles interact with the field.
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- Shifting to this other state would require it to overcome an enormous energy barrier, and the probability of this happening is so small that it is unlikely to occur on the timescale of the lifetime of the Universe.
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- Can we make Higgs measurements more precise? So far, the Higgs boson’s properties match those predicted by the standard model, but with an uncertainty of around 10%. More data will increase the precision of these measurements and the LHC has collected just one-twentieth of the total amount of information it is expected to gather.
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- Does the Higgs interact with lighter particles? Until now, the Higgs boson’s interactions have seemed to fit with the standard model, but physicists have seen it decay into only the heaviest matter particles, such as the bottom quark.
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- Physicists now want to check whether it interacts in the same way with particles from lighter families, known as generations. In 2020, CMS and ATLAS saw one such interaction, the rare decay of a Higgs to a second-generation cousin of the electron called the “muon1“.
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- Does the Higgs interact with itself? The Higgs boson has mass, so it should interact with itself. But such interactions, for example, the decay of an energetic Higgs boson to two less energetic ones, are extremely rare, because all the particles involved are so heavy. ATLAS and CMS hope to find hints of the interactions after a planned upgrade to the LHC from 2026, but conclusive evidence will probably take a more powerful collider.
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- The probability of self-interaction is determined by how the Higgs field’s potential energy changes near its minimum, which describes conditions just after the Big Bang. So knowing about the Higgs self-interaction could help scientists to understand the dynamics of the early Universe.
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- Many theories that try to explain how matter somehow became more abundant than antimatter require Higgs self-interactions that diverge from the standard model’s prediction by as much as 30%.
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- What is the Higgs boson’s lifetime? Physicists want to know the lifetime of the Higgs ,how long, on average, it sticks around before decaying to other particles, because any deviation from predictions could point to interactions with unknown particles, such as those that make up dark matter. But its lifetime is too small to measure directly.
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- To measure it indirectly, physicists look at the spread, or ‘width’, of the particle’s energy over multiple measurements. Quantum physics says that uncertainty in the particle’s energy should be inversely related to its lifetime.
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- Last year, CMS physicists produced their first rough measurement of the Higgs’ lifetime: 2.1 × 10^−22 seconds. The results suggest that the lifetime is consistent with the standard model.
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- Are any exotic predictions true? Some theories that extend the standard model predict that the Higgs boson is not fundamental, but, like the proton, is made up of other particles. Others predict that there are multiple Higgs bosons, which behave similarly but differ, for example, in charge or spin.
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- As well as checking whether the Higgs is truly a standard-model particle, LHC experiments will look for properties predicted by other theories, including decays into forbidden particle combinations.
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- Ten years go I wrote this Review of what we thought we knew about the Higgs Particle.
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------------------ 735 - The Higgs Particle written in 2010
- December 9, 2006, Fermilab’s particle accelerator physicists may have detected the Higgs particle. The Higgs Boson is the particle expected to give every other fundamental particle its mass. They saw the particle at 160 GeV ( 160,000,000,000 electron volts, 6^10^11 eV, ), which is close to the theoretical mass of the Higgs.
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- We know mass as inertia that resists a force trying to accelerate it. The Higgs Boson may be the particle that causes that resistance. Bosons are photons, W-Z bosons, Gluons and now Higgs. Photons carry the electromagnetic force and have no mass. W-Z bosons carry the nuclear Weak Force but they have a huge mass. The theoretical Higgs Boson would explain the difference between these two forces. Its discovery could unleash an explanation for mass and inertia. It could be one of the fundamental building blocks of nature.
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- Particle accelerators have verified the existence of 12 fundamental particles of matter and 3 fundamental particles of force carriers, but the Higgs has not been found to date (That was in 2012).
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- The Higgs is a quantum particle of the Higgs Field that permeates empty space. The field has a value of 246 GeV. It is a scalar field giving the Higgs Boson a spin of zero, no intrinsic angular momentum. It permeates all of empty space and carries the force that gives the other particles their mass. Theories predict the mass of the Higgs to be between 130 - 190 GeV. This particle discovered at 160 GeV is a good candidate.
(It was discovered to be st 125 GeV)
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- Particle accelerators need tremendous energies to detect these high mass particles. Why are such high energies necessary. It is because E = h*f, E = h*c/w. “h” is Planck’s Constant. “c” is speed of light. “f“ is frequency. “w” is the wavelength.
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-------------------- The Energy = 6.6 * 10^-34 kg*m^2/sec * 3*10^8 m/sec / wavelength.
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------------------- E = 2*10^-25 / wavelength
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- Wavelength is inversely proportional to Energy. In order to “see” with shorter wavelengths we nee to use higher and higher energies.
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- The particle accelerator is a type of microscope. Like the electron microscope can see smaller objects than the photon microscope. Larger energies correspond to smaller distances.
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-------------- Energy, or Mass ------------ Length
------------------ --------
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---------------- 10^28 eV ------------------ --------------------- Planck scale mass
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------------------------------ ------------------ 10^-35 meters - Planck scale length
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---------------- 10^27 eV ------------------
---------------- 10^25 eV ------------------ 10^-33 - Three Forces come together
---------------- 10^24 eV ------------------
-------------------------- ---------------------- 10^-30 meters
---------------- 10^21 eV ------------------
---------------------------- -------------------- 10^-27meters
---------------- 10^18 eV ------------------
-------------------------- ----------------------- 10^-24 meters
---------------- 10^15 eV ------------------
--------------------------- ------------------ --- 10^-21 meters - Energy to find the Higgs
---------------- 10^12 eV ----------------------------------- Weak Force scale
------------------------------ ------------------ 10^-18 meters
---------------- 10^9 eV -------------------------------------- proton mass
------------------------------------------------- 10^-15 meters
---------------- 10^6 eV ------------------------------------ electron mass
------------------------------------------------- 10^-12 meters -
---------------- 1,000 eV ---------------- --- 10^-10 meters - size of atom
---------------------------------------------- --- 10^-9 meters
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- Note that larger energies correspond to smaller distances. The large Planck Scale Energy 10^28 electron volts means that the force of gravity is weak. The Weak Force Scale Energy is 10^12 electron volts and it operates over a distance of 10^-18 meters.
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- It is a mystery to physicists why the Planck scale is 16 orders of magnitude more massive than the Weak scale (10^28 vs. 10^12 = 10^16).
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- The Standard Model predicts that if the mass of the W-Boson is between 80.2 and 80.4 GeV. And, the mass of the Top Quark is between 160 and 185 GeV. Then, the Higgs Boson is between 114 and 400 GeV. But, experiments are giving differing results. So, is the Standard Model correct, or incomplete?
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- One of the theories, called “Super symmetry“, predicts that there are five Higgs Bosons of different masses. However, the Standard Model predicts only a single Higgs. In order to discover which theory is true we need more powerful accelerators.
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- A speed of light collision between protons and anti-protons would create Higgs particles that would decay into 2 Tau Leptons in a fraction of a second. Then the Tau’s would decay into other particles. Physicists are busy studying these collisions and the particle debris they create in search of the illusive Higgs. Its discovery will be a great day in physics ( written in 2012)
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September 1, 2022 HIGGS BOSON - ten years since first discovery? 735 3670
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--------------------- --- Saturday, September 3, 2022 ---------------------------
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