Strong CP problem: Difference between revisions

Revision as of 20:16, 2 December 2021

Revision as of 20:18, 2 December 2021

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Current experimental upper bounds on the dipole moment give an upper bound of <math>d_N < 10^{-26} \text{e}\cdot</math>cm<ref>{{Cite journal |last1=Baker |first1=C.A. |last2=Doyle |first2=D.D. |last3=Geltenbort |first3=P. |last4=Green |first4=K. |last5=van&nbsp;der&nbsp;Grinten |first5=M.G.D. |last6=Harris |first6=P.G. |last7=Iaydjiev |first7=P. |last8=Ivanov |first8=S.N. |last9=May|first9=D.J.R. |date=2006-09-27 |df=dmy-all |title=Improved experimental limit on the electric dipole moment of the neutron |journal=Physical Review Letters |volume=97 |issue=13 |pages=131801 |doi=10.1103/PhysRevLett.97.131801 |pmid=17026025 |arxiv=hep-ex/0602020|s2cid=119431442 }}</ref>, which requires <math>\bar \theta < 10^{-10}</math>. The angle <math>\bar \theta</math> can take any value between zero and <math>2\pi</math>, so it taking on such a particularly small value is a fine-tuning problem called the strong CP problem.

==Proposed solutions==