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Violation in Mixing

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1.4 �È <strong>Violation</strong> <strong>in</strong> the Standard Model 35<br />

ÁÑ<br />

ÁÑ<br />

�<br />

Î £<br />

�Î �ÎØ�Î £<br />

�<br />

Î �Î £ �Î £<br />

Ø�ÎØ� � Î £ Ù� ÎÙ�Î �Î £ �<br />

ÎÙ�Î £ Ù� Î £ � Î �<br />

�<br />

�<br />

� ×�Ò ¬� (1.54)<br />

� ×�Ò ­�<br />

In the parameterization 1.47, the terms ÎÙ�, Î �, Î � and ÎØ� are chosen to be real and Î � � so that (from<br />

Eqs. 1.52):<br />

and also:<br />

ÎØ�<br />

Î £ Ù�<br />

×�Ò « � ÁÑ<br />

�<br />

¬<br />

�<br />

ÎÙ�ÎØ�<br />

Î £ Ù�Î £<br />

�<br />

¬<br />

¬ ÎØ�<br />

¬ ÎÙ�<br />

��«<br />

�<br />

ÎØ� � �ÎØ��� �¬<br />

�<br />

Î £<br />

�<br />

×�Ò ¬ � ÁÑ<br />

The same relations can be written through the Wolfenste<strong>in</strong> parameters:<br />

�<br />

Ø� « �<br />

� � �<br />

Ø� ¬ � �<br />

ÎØ�<br />

�<br />

�<br />

Î £ Ù� � �ÎÙ��� �­ �<br />

�<br />

Î £ �<br />

Ù�<br />

×�Ò ­ � ÁÑ �<br />

Ø� ­ � �<br />

� �<br />

1.4.3 Measur<strong>in</strong>g �ÃÅ Parameters with �È Conserv<strong>in</strong>g Processes<br />

Six of the n<strong>in</strong>e absolute values of the �ÃÅ elements are measured directly, basically from tree level<br />

processes. (All numbers below are taken from Review of Particle Physics [14].)<br />

A high precision measurement of �ÎÙ�� is obta<strong>in</strong>ed by compar<strong>in</strong>g the rates for ¬ nuclear decays to the muon<br />

decay rate: it has been obta<strong>in</strong>ed<br />

�ÎÙ�� � ���� ¦ � .<br />

Semileptonic kaon decays and strange barion (hyperon) decays give:<br />

�ÎÙ×� � � � ¦ � �.<br />

Values for ��� and �� can be determ<strong>in</strong>ed with various techniques: the rate of charm production <strong>in</strong><br />

neutr<strong>in</strong>o <strong>in</strong>teractions with valence quarks <strong>in</strong> nucleons gives<br />

�Î �� � � � ¦ � �.<br />

A similar way cannot be used for �Î ×� because of the lack of knowledge regard<strong>in</strong>g the population of ×× pairs<br />

<strong>in</strong> the nucleon “sea”. Alternatively, �Î ×� can be determ<strong>in</strong>ed from the decay � � Ã� ��,giv<strong>in</strong>g<br />

�Î ×� � � ¦ � �.<br />

ÎÙ�<br />

�È VIOLATION IN THE �� SYSTEM

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