Weak hypercharge Information & Weak hypercharge Links at HealthHaven.com
advertise
add site
services
publishers
database
health videos
Bookmark and Share

search wiki for    ?
web dir firms image gallery news pdf wiki shop video 
about
toolbar
stats
live show
health store
more stuff
JOIN/LOGIN
Featured Results:
 Weak Ankles: Causes and Cures for Weak Ankles, Supination
Weak Ankles: Causes and Cures for Weak Ankles, Supination
mortonsfoot.com
 Systolic Blood Pressure Can Damage Weak Arteries
Systolic Blood Pressure Can Damage Weak Arteries
fitnesshealthandwellnessc...
 Types of Weak Non-covalent Bonds - Part 1
Types of Weak Non-covalent Bonds - Part 1
accessexcellence.org
 
Flavour in particle physics
Flavour quantum numbers:

Combinations:

  • Hypercharge: Y
    • Y = (B + S + C + B′ + T)
    • Y = 2 (QI3)
  • Weak hypercharge: YW
    • YW = 2 (QT3)
    • X + 2YW = 5 (BL)

Flavour mixing

The weak hypercharge in particle physics is a conserved quantum number relating the electrical charge and the third component of weak isospin, and is similar to the Gell-Mann–Nishijima formula for the hypercharge of strong interactions (which is not conserved). It is frequently denoted YW and corresponds to the gauge symmetry U(1).[1]

Contents

[edit] Definition

It is the generator of the U(1) component of the electroweak gauge group, SU(2)xU(1) and its associated quantum field B mixes with the W3 electroweak quantum field to produce the observed Z0 gauge boson and the photon of quantum electrodynamics.

Weak hypercharge, usually written as YW, is defined as:

\qquad Q = T_3 + {Y_W \over 2}

where Q is the electrical charge (in elementary charge units) and T3 is the third component of weak isospin. Rearranging, the weak hypercharge can be expressed as:

\qquad Y_W = 2(Q - T_3)

Note: sometimes weak hypercharge is scaled so that

\qquad Y_W = Q - T_3

although this is a minority usage.[2]

[edit] Baryon and lepton number

Weak hypercharge is related to baryon number - lepton number via:

X + 2Y_W = 5(B - L) \,

where X is a GUT-associated conserved quantum number. Since weak hypercharge is also conserved this implies that baryon number - lepton number is also conserved, within the Standard Model and most extensions.

[edit] Neutron decay

np + e + νe

Hence neutron decay conserves baryon number B and lepton number L separately, so also the difference B-L is conserved.

[edit] Proton decay

Proton decay is a prediction of many grand unification theories.

p+e+ + π0e+ + 2γ

Hence proton decay conserves B-L, even though it violates both lepton number and baryon number conservation.

[edit] See also

[edit] Notes

  1. ^ J. F. Donoghue, E. Golowich, B. R. Holstein (1994). Dynamics of the standard model. Cambridge University Press. pp. 52. ISBN 0521476526. 
  2. ^ M. R. Anderson (2003). The mathematical theory of cosmic strings. CRC Press. pp. 12. ISBN 0750301600. 



Product Results (view all...)

search wiki for    ?
web dir firms image gallery news pdf wiki shop video 



↑ top of page ↑about thumbshots