1 / 10

In general NON-ABELAIN GAUGE THEORIES :

In general NON-ABELAIN GAUGE THEORIES :. introduce more interactions (vertices) for SU(2) we saw both 3 and 4 particle interaction vertices have (still) massless gauge particles (like the photon!) the gauge field particles posses “charge” just like the fundamental Dirac states

koto
Download Presentation

In general NON-ABELAIN GAUGE THEORIES :

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. In general NON-ABELAIN GAUGE THEORIES: • introduce more interactions (vertices) • for SU(2) we saw both 3 and 4 particle interaction vertices • have (still)massless gauge particles (like the photon!) • the gauge field particles posses “charge” just like the • fundamental Dirac states • not electric charge - we’re trying to think of NEW forces TheYANG-MILLS was built on the premise that there existed • 2 elementary Dirac (spin-1/2) particles of ~equal mass • serving as sources for the force fields through which they interact NO SUCH PAIRS EXIST • proton/neutron isospin states were the inspiration, but • there is NO massless vector (spin 1) iso-triplet • (isospin 1) of known particle states • r-mesons? 770 MeV/c2 • p,n,r now recognized as COMPOSITE particles • isospin of up,dn quarks generalized into SU(3) SU(4) The strong force must be independent of FLAVOR up charm top down strange bottom i.e., the strong force does not couple to flavors. SO WHERE DOES THE STRONG FORCE COME FROM?

  2. Rutherford 1911 Elastic scattering of α – particles on atoms Discovery of atomic nucleus Size of nucleus 10-5 size of atom

  3. 1968 SLAC-MIT Deep inelastic scattering of e- of p, d observation of ~flat q2 dependence of R= σinel/σMott R ~ const →point-like scatterers inside proton Fermi referred to these as “partons” which eventually became identified with the quarks!

  4. We’ve argued for the simple energy dependence Cross section  Energy possibly punctuated by resonances Cross section  and threshold effects as higher energy opens up new production of heavier particles Energy

  5. e+e- anihilation cross section Cross-section, cm2 s = cms energy, GeV

  6. Dirac particlesfundamental,charged Fermions (spin- 1/2) e-e+m-m+t-t+udcst b udcstb q: -1 +1 -1 +1 -1 +1 +2/3 -1/3 +2/3 -1/3 +2/3 -1/3 -2/3 +1/3-2/3 +1/3 -2/3 +1/3 All can be described by DIRAC equations w/charge coupling to g-fields - u e- q=e q=e 2/3e ?? e- - u m105 MeV/c2 u7.5 MeV/c2 d4.2 MeV/c2 c 1100 MeV/c2 s150 MeV/c2 b 4200 MeV/c2

  7. Consider e+e- annihilation in an electron-positron collider e+e-, +-,  +  -, q+q- Q-coupling any flavor e e+ e- unclear if annihilated easy signature to detect! (hadrons) (+-) N e+e-hadrons Ne+e-+- R = = total probability of all possible quarks  iqi2 Q

  8. m105 MeV/c2 u7.5 MeV/c2 d4.2 MeV/c2 c 1100 MeV/c2 s150 MeV/c2 b 4200 MeV/c2 When above the u,d,s threshold 2 3 = above the J/ mass (c-production threshold) 10 9 R = = 1.11 above the upsilon mass (b-production threshold) 11 9 R = = 1.22

  9. 3.67 3.33 1.22 1.11 0.66 Off by a factor of3!!!!! Could every known quark have a previously un-noticed 3-fold degeneracy????

More Related