Changes between Version 2 and Version 3 of QandA
 Timestamp:
 04/19/12 09:34:58 (7 years ago)
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QandA
v2 v3 16 16 of the Standard Model (violated by weak interactions) it should be included. The problem is that one would then expect, from naturalness argument 17 17 to have $\theta$ of order one. Experimental bounds coming mainly from the limits on the neutron electric dipole moment gives 18 %$\theta<10^{10}$. This gives the socalled "strong CP problem". The PecceiQuinn mechanism ([http://prola.aps.org/abstract/PRL/v38/i25/p1440_1 Phys.Rev.Lett. 38 (1977), 1440]) is a famous attempt to solve this problem by introducing a dynamical field, which gives rise to the axion. See the PDG section on [http://pdg.lbl.gov/2008/reviews/axion_s029.pdf axion searches] for an uptodate report on axion searches.18 $\theta<10^{10}$. This gives the socalled "strong CP problem". The PecceiQuinn mechanism ([http://prola.aps.org/abstract/PRL/v38/i25/p1440_1 Phys.Rev.Lett. 38 (1977), 1440]) is a famous attempt to solve this problem by introducing a dynamical field, which gives rise to the axion. See the PDG section on [http://pdg.lbl.gov/2008/reviews/axion_s029.pdf axion searches] for an uptodate report on axion searches. 19 19 20 20 ====== The parton distribution functions are nonperturbative quantities. Is there any solid lattice result? ====== … … 33 33 34 34 There are several : the properties (energy and angular distributions) of the muon decay 35 %$\mu^ \to e^ \bar \nu_e \nu_\mu$, Beta decay, and pion decays $\pi^ \to l^ \bar \nu_l$.35 $\mu^ \to e^ \bar \nu_e \nu_\mu$, Beta decay, and pion decays $\pi^ \to l^ \bar \nu_l$. 36 36 A concise list and discussion can be found, for instance, in the older version of the lectures on the SM by A. Pich ([http://www.slac.stanford.edu/spires/find/hep/www?eprint=hepph/9412274 hepph/9412274]). 37 37