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Results tagged with particle-physics
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user 36793
Particle physics is the study of the fundamental forces of nature as they are embodied in the interactions of elementary and composite particles at high energies and short time and distance scales. DO NOT USE THIS TAG for point particles in classical mechanics.
2
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4
answers
1k
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Majorara mass and fermion number violation
How can it be shown that the Majorana mass violates the fermion number by two units? Can even a Noether charge be defined in presence of Majorana mass term?
- 27.2k
1
vote
1
answer
176
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meaning of Higgs coupling is flavor conserving
I have heard the statement that the Higgs coupling is flavor conserving. What does it mean? What kind of coupling would be flavor non-conserving?
- 27.2k
3
votes
1
answer
133
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Two ways of looking at weak current?
A weak current of the form: $$j^\mu=\bar u_e \gamma^\mu \frac{1}{2}(1-\gamma^5)u_\nu$$ implies that it automatically selects the left-handed neutrino. This current can also be written as: $$j^\mu=\bar …
- 27.2k
3
votes
1
answer
993
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Why is the muon decay a Flavor Changing Charged Current (FCCC) process?
One way of understanding why the muon decay $$\mu^-\to e^-+\bar{\nu}_e+\nu_\mu\tag{1}$$ is a Charged Current (CC) process is to write the intermediate step through which the decay (1) proceeds i.e., $ …
- 27.2k
2
votes
1
answer
202
views
Is degenerate neutrino mass possible?
Can two of the three light neutrino masses be exactly degenerate in the context of current experimental data?
- 27.2k
1
vote
1
answer
361
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Measurement of Solar and other neutrino Mixing angles
According to the neutrino flavour oscillation formula $$
P_{\alpha\beta}=4\sum\limits_{i<j}U_{\alpha i}U_{\beta i}^*U_{\alpha j}U_{\beta j}^* \sin^2\frac{(m_i^2-m_j^2)L}{4E}.$$ Hence, there can be thr …
- 27.2k
0
votes
0
answers
48
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About the experimental measurement of neutrino magnetic moment and its value
Massive neutrinos, be it Dirac or majorana, have magnetic moment. See here, here and here.
$\bullet$ How is it measured (or can be measured) in real experiments? What are the (upper and lower) bound …
- 27.2k
4
votes
1
answer
227
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If $U$ determines the mixing between fields and $U^*$ determines the mixing between states-Why?
In this pdg review, Eq. (14.1), the mixing between the flavour neutrino fields and neutrino fields corresponding to mass eigenstates are denoted as $$\nu_{lL}=\sum\limits_{j}U_{lj}\nu_{jL}\tag{1}$$ wh …
- 27.2k
1
vote
The mass change of electron after absorbing photon
Relativistic mass is an archaic concept, and I believe, it is not used by professional physicists any longer. No. The rest mass won't increase only its momentum will change and it will scatter.
- 27.2k
1
vote
1
answer
156
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How will the light neutrino mass hierarchy be determined?
The light neutrino mass hierarchy is not known yet. This is because for one of the two independent mass-squared differences only the absolute value is known.
Is there a way that in future the hierar …
- 27.2k
3
votes
1
answer
478
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Have all three flavors of solar neutrino been measured?
As far as I know that the sun exclusively produces electron neutrinos ($\nu_e$). When the flux of solar neutrinos ($\nu_e$) is measured on the earth, a depletion is observed in the $\nu_e$ flux i.e., …
- 27.2k
1
vote
Neutrino mass hierarchy
I disagree with the answer provided by @StefanoGariazzo.
Oscillation probabilities are insensitive to the signs of $\Delta m_{ij}^2$ for all $i$ and $j$.
However, the numbering of massive neutrinos …
- 27.2k
3
votes
2
answers
1k
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Can charged leptons undergo oscillation?
Neutrino oscillation is an observed fact while charged lepton oscillation is not. Unlike neutrinos, is it possible for the charged leptons to oscillate, theoretically? In other words, is there anythin …
- 27.2k
3
votes
No massless new goldstone boson after 1D U(1) spontanous symmetry breaking?
Your Lagrangian is not invariant under U(1) transformations $\phi\to e^{i\theta}\phi$. Hence there is no contradiction. The Lagrangian you wrote is that of a real scalar field $\phi$ and it is only in …
- 27.2k
6
votes
3
answers
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Unitarity of PMNS matrix
Why should the neutrino mixing matrix (PMNS matrix) be unitary? Is the unitarity dictated by experiments or is it a theoretical demand?
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