charitysilikon.blogg.se - Lepton number

LEPTON NUMBER FREE

The Mu2e experiment in construction has a planned sensitivity of order 10 −17.

Some BSM (Beyond Standard Model) theories such as SUSY predict branching ratios of order 10 −12 to 10 −14. Neutrino oscillation Lepton Spin-½ Beta decay Electron neutrino. They are distinguished from the neutrinos by having opposite signs of lepton number and chirality. However, the quantum number B − L is much more likely to work and is seen in different models such as the Pati–Salam model.Įxperiments such as MEGA and SINDRUM have searched for lepton number violation in muon decays to electrons MEG set the current branching limit of order 10 −13 and plans to lower to limit to 10 −14 after 2016. This process, inverse beta decay, conserves lepton number, as the incoming antineutrino has lepton number 1, while the outgoing positron (antielectron) also has lepton number 1. Thus, it is possible to see rare muon decays such as µ → eγ or µN→eN: īecause the lepton number conservation law in fact is violated by chiral anomalies, there are problems applying this symmetry universally over all energy scales. However, the (total) lepton number conservation law must still hold (under the Standard Model). This means the conservation laws are violated, although because of the smallness of the neutrino mass they still hold to a very large degree for interactions containing charged leptons. Since neutrino oscillations have been observed, neutrinos do have a tiny nonzero mass and conservation laws for LF numbers are therefore only approximate. In the Standard Model, leptonic family numbers (LF numbers) would be preserved if neutrinos were massless. Violations of the lepton number conservation laws This is cited as a test for special relativity testing the time dilation effect Like many lepton interactions, muon decay is a Weak Interaction.

LEPTON NUMBER FREE

With the same assigning scheme as the leptonic number: +1 for particles of the corresponding family, −1 for the antiparticles, and 0 for leptons of other families or non-leptonic particles.Īn example is the muon decay. Answer (1 of 4): It’s ultimately an arbitrary convention, but it is a natural enough one so the question in response would really be: Why not There is a well-defined number to be associated with the electron field, corresponding to a globally conserved U(1) symmetry of the free electron Lagrang.

L τ, the tauonic number for the tau and the tau neutrino.

L μ, the muonic number for the muon and the muon neutrino.

L e, the electronic number for the electron and the electron neutrino.

Lepton number was introduced in 1953 and was invoked to explain the absence of reactions such as in the reactor Cowan–Reines neutrino experiment, which observed instead.īeside the leptonic number, leptonic family numbers are also defined: Lepton number (sometimes also called lepton charge) is an additive quantum number, which means that its sum is preserved in interactions (as opposed to multiplicative quantum numbers such as parity, where the product is preserved instead). So all leptons have assigned a value of +1, antileptons −1, and non-leptonic particles 0. In particle physics, the lepton number is a conserved quantum number representing the number of leptons minus the number of antileptons in an elementary particle reaction.