Everything about The Tau Lepton totally explained
The
tau lepton (often called the
tau,
tau particle, or occasionally the
tauon; symbol ) is a negatively charged
elementary particle with a lifetime of and a
mass of (compared to for
protons and for
electrons). It has an associated
antiparticle (the anti-tau) and neutrinos (the
tau neutrino and
tau antineutrino).
Classification
The tau lepton belongs to the 3rd
generation of
leptons. It is the third generation counterpart of the
electron (1st generation) and the
muon (2nd generation). Like the electron and muon, the tau lepton appears to be pointlike; no structure has been detected, and if there's any, it would have to be on a scale of less than . Also, like the electron and muon, the tau has a
spin of 1/2. The tau lepton and its antiparticle carry the same electric charges as the electron and
positron, respectively.
Decay
The tau is the only lepton that can decay into
hadrons—the other leptons don't have the necessary mass. Like the other decay modes of the tau lepton, the hadronic decay is through the
weak interaction.
Since tau-like lepton number is conserved in weak decays, a tau neutrino is created when a tau lepton decays to a muon or electron.
The
branching ratio of the common tau decays are:
- 17.84% for decay into a tau neutrino, electron and electron neutrino
- 17.36% for decay into a tau neutrino, muon and muon neutrino
Discovery
The tau lepton was detected in a series of experiments between 1974 and 1977 by
Martin Lewis Perl with his colleagues at the
SLAC-
LBL group
(External Link
). Their equipment consisted of
SLAC's then-new e
+-e
− colliding ring, called SPEAR, and the
LBL magnetic detector. They could detect and distinguish between leptons, hadrons and
photons. They didn't detect the tau lepton directly, but rather discovered anomalous events:
"
We have discovered 64 events of the form
» + → e
± + μ
∓ ≥ 2 undetected particles
for which we've no conventional explanation."
The need for at least 2 undetected particles was shown by the inability to conserve energy and momentum with only one. However, no other muons, electrons, photons, or hadrons were detected. It was proposed that this event was the production and subsequent decay of a new particle pair:
» + → + → e
± + μ
∓ + 4
This was difficult to verify, because the energy to produce the pair is similar to the threshold for D meson production. Work done at
DESY-Heidelberg, and with the Direct Electron Counter (DELCO) at SPEAR, subsequently established the mass and spin of the tau.
Martin Perl shared the 1995 Nobel Prize for physics with
Frederick Reines. The latter was awarded his share of the prize for detecting the neutrino.
Further Information
Get more info on 'Tau Lepton'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://tau_lepton.totallyexplained.com">Tau lepton Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
