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Neutrinos and antineutrinos are indistinguishable by most of their qualities, butt not all. One of the quantities that distinguish them is exactly the lepton number, which make them interact with other particles in a different way. For example, a neutrino can take part in the reaction $$ n + \nu_e \rightarrow p^+ + e^-$$ but antineutrino can't; on the other ...


7

This seems to be a rather complicated issue. The earliest source I've been able to find proposed the existence of a muon counterpart to the electron neutrino is Sakata & Inoue's On the Correlations between Mesons and Yukawa Particles, published in English in 1946 but formulated several years prior. They postulated the existence of a charged meson $m^{\pm}...


7

The 2018 Particle Data Group gives a value of $880.2\pm 1.0$ s for free neutron lifetime, as an average of the seven best measurements. As can be seen, the measurements have non-overlapping confidence intervals. As discussed in (Wietfeldt 2014) the different experimental methods do not agree on the value. Wietfeldt gives the formula of the lifetime as $$\...


6

So my real question is, do any of the extension of the SM to add neutrino mass signal new physics? What does even count as new physics? I think it would be something like a fifth force. Not sure what the general agreement is on "new physics". Your question is opinion based, and there is no solid answer to it. Lots of question on this site address ...


6

Simplest way? The $\Delta^{++}\sim uuu$ has to be a color singlet. It has spin 3/2, so it is flavor and spin symmetric. But fermion quarks need to be in a fully antisymmetrized state. Can you make an SU(4) singlet out of three antisymmetrized copies of an SU(4) representation, the way you can for SU(3)? (No.) (By now, you simply experimentally check R in $e^+...


6

or is the theory we have have no correct and there is no need for further debate. You are a hundred years too late to be able to play with the models of nuclear physics. Physics reasearch at present has progressed to the level that has shown that protons and neutrons, not only are the two versions of the"same" particle called collectively a ...


4

For a particle propagating through space, its wavefunction furnishes the probability of finding it in a given place which is a different number for every different place. This is a single-valued variable. Electromagnetic waves are very different; they propagate through space as the interplay between a linked pair of an electric field and a magnetic field, ...


3

You might get better answers if you actually identified the particles involved and their decays. I'll just remind you of the dimensional analysis aspect of all of them, which you drill in an introductory HEP course: For weak decays involving one dominant scale, Γ with units of energy must go as the amplitude-squared, involving an exchange of a virtual W in ...


3

Virtual particles are better regarded as a convenient way of representing terms in the infinite sums of quantum field theory than as particles. Feynman introduced his diagrams to organise the calculations but did not claim the virtual particles were "real" in any useful sense. They are not ontological explanations for things, but often used in ...


3

Since there is no way to tell neutrinos and antineutrinos apart There is. Neutrinos are distinguished from antineutrinos since they have opposite signed lepton number and opposite chirality relative to each other. They were also first detected in 1956 as part of an experiment to first detect neutrinos. does conservation of lepton number make any sense? ...


3

I may have found it. I'm quoting Wiki's article on Schoichi Sakata: Sakata and Inoue proposed their two-meson theory in 1942.[3] At the time, a charged particle discovered in the hard component cosmic rays was misidentified as the Yukawa’s meson ($\pi^\pm$, nuclear force career particle). The misinterpretation led to puzzles in the discovered cosmic ray ...


3

EDIT: This answer was for the original question "Motivation behind the principle electrons are not identical." (IMO, the concept of distinguishability is more nuanced, I welcome reading others' answers on it.) The guiding principle is that if you measure a particle that has different properties from an electron, you don't call it an electron. A ...


3

The answers are good, but I need to explicitly state what is conceptually wrong in your question. An electromagnetic wave is made of an electric wave and a magnetic wave, so 2 waves. The classical electromagnetic wave is one wave, its intensity and direction depending on two variables that are a function of each other through the solutions of Maxwell's ...


3

You question begins An electromagnetic wave is made of an electric wave and a magnetic wave, so 2 waves. and asks “How many waves for a particle wave?” However, I think it’s important to realize that “there are two waves” is just one model of the electromagnetic field, and it’s not necessarily the best one. For one thing, electric field $\vec E$ and ...


3

The models that describe photons used in quantum optics and in particle physics are one and the same: the Standard Model of particle physics (often replaceable with just its quantum electrodynamics component) as encased within the formalism of quantum field theory. Moreover, the definition of photons (more specifically, single-photon states of the field) are ...


3

I dont know what you mean by the two equations will become one equation. But in general, yes. There is a process called cherenkov radiation where, if a charged particle (ie an electron) moves faster than the speed of light in that material, then you get a flash of light (if you use a classical electric field this flash is equivalent to the sonic boom when ...


3

This feels like a perfect storm of misconceptions, unleashed by unscrupulous popular science writing. Helicity is Lorentz-variant, so, as you envision, may be reversed by changing your frame. It is either positive or negative; never left-or right handed. Chirality is relativistically invariant, so a left-handed particle is left-handed in any frame, and ...


3

The "size" of a particle at rest such as the muon, is its Compton wavelength, $1/m_\mu$ in natural units ($\hbar=1, c=1$, easy to reinstate uniquely). You may then check that for the muon this is $$ \lambda_\mu \approx \frac{1}{m_\mu} \approx 2~fm= 2 \cdot 10^{-15}m, $$ a mere speck, close to nuclear size. You are contrasting this to tenths of ...


3

You seem to have a misunderstanding. As already pointed out in the comments, a black hole does not have infinite mass. In fact, the "size" of the black hole (to be precise, the radius of the event horizon since the actual singularity is believed to be point-like), is directly related to the black hole's mass (and only to the mass, since all the ...


2

Before going to dangerous irrelevance, it helps to briefly recapitulate what irrelevance under RG means in itself. When thinking of an RG fixed point, the scaling behaviour at low energies/long wavelengths is typically controlled only by a handful of relevant operators which dominate the physics, while all irrelevant terms progressively get smaller and ...


2

Firstly there is the usual intuitive physical argument, which are probably aware of and is also explained in the post by @Ratman. Another version of this same argument is that, because of the asymptotic freedom of QCD, and the high energy scale of the process, the partons inside the hadron are approximately free particle moving collinear to the hadron, since ...


2

Well you could read overviews of reactor physics (search using google) or seeif you can find an online schools like Udemy, Edx, or others (again search for online reactor courses). But to really understand it you'll need to understand the math. Reactor Physics, like all physics involves much math. I just found a course by Edx on the basics of physics ...


2

There are several different interatomic potentials that can model the attraction and repulsion between atoms as a function of distance (and perhaps other parameters), but the Lennard-Jones potential, which looks like $$V_{LJ} = 4\varepsilon\left[\left(\frac{\sigma}r\right)^{12} -\left(\frac{\sigma}r\right)^6\right]$$ is one of the most straight-forward to ...


2

Physicists used accelerators such as the Stanford Linear Collider to study high-energy collisions between electrons and positrons. These experiments found that neither particle has internal constituents at the length scales that the accelerator could probe. They behave as fundamental, non-composite particles, as the Standard Model of particle physics assumes....


2

Photons are excitations of electromagnetic field. These are part of the phenomenon that we call "light", so the phrasing in the book is misleading. Closer to the matter: all particles can be though of as excitations of some field. When the field is electromagnetic, they are called photons. In other words, the statement should be Photons are the ...


2

You may be confused by the phrasing of the statement: particles as excitations of a field. This peculiar way of saying it comes from quantum field theory. A 19th-century physicist --before quantum field theory was established-- would probably say "light is the electromagnetic field moving through the vacuum" or "away from sources". It's ...


2

It fits with the long discussion we had on this question : What is the connection between quantum optical photons and particle physics' photons? and the answers and comments therein. People working with quantum optics have a more general view of the term "excitations of the electromagnetic field". In the quantum field theory used in the standard ...


2

The neutron is a spin 1/2 neutral particle. That means the only magnetic property it can have is a dipole moment, and it must be aligned with the spin. It can have an electric dipole moment, but that is parity and time-reversal violating (see: Electric Dipole Moment of the neutron). Since it is neutral, but has a magnetic moment, it must have internal ...


2

Usually each laser is specified by emitted maximum power and light wavelength. Using energy-power relation $$E=P\,t$$ and the fact that laser energy is the sum of energy of all photons emitted : $$ E=n~h\nu $$, one can calculate total number of photons $n$, given laser power $P$, wavelength $\lambda$ and time window $t$ : $$ n = \frac {P\lambda}{hc} ~t $$ ...


1

Phonons do not have all the ingredients required in the Standard Model (local symmetry, three fermion generations, scalar multiplet, SSB). Is this the reason why phonon are not in the boson list of SM? The table of particles axiomatically assumed for the standard model consists of point elementary particles, i.e.non composite. Phonons by the your ...


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