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Violation in Mixing

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178 Analysis of the time-dependent �È -violat<strong>in</strong>g asymmetry <strong>in</strong> � � � � decays<br />

ÆÃ�<br />

Æ �Ã�<br />

à �<br />

�� �� �� ��<br />

�<br />

Æ<br />

�à �<br />

��� �� where:<br />

¯ Æ� � fitted number of events of type � <strong>in</strong> the entire sample.<br />

¯ � � � fraction of events of type � that are tagged <strong>in</strong> category .<br />

¯ Æ � È Æ�� � .<br />

¯ �� � Æ Ã � Æ Ã � �Æ Ã � Æ Ã � , the direct �È -violat<strong>in</strong>g asymmetry.<br />

¯ È � � È � Ñ�Ë ¡È � ¡� ¡È � � ¡È � � ¡È � � ¡È � ¡Ø .<br />

Untagged events are treated as a fifth category with � � ¡� � . Due to the small number of signal<br />

events, we use the transformation of variables Æ � � Æ�� � <strong>in</strong> order to fit for the total yields Æ� rather than<br />

the yield <strong>in</strong> each tagg<strong>in</strong>g category. Background tag fractions � come from Table 7-6. For signal we assume<br />

� �� � � Ã� � � Ãà and use the result from the Breco data sample (Table 7-8).<br />

The extended likelihood Ä for a s<strong>in</strong>gle category is given by<br />

Ä � � Æ Æ Æ<br />

�<br />

�<br />

�� � (7.11)<br />

where the Poisson term is the probability of observ<strong>in</strong>g Æ events <strong>in</strong> category when Æ are expected.<br />

Includ<strong>in</strong>g this term allows for the direct fitt<strong>in</strong>g of yields rather than fractions. F<strong>in</strong>ally, the total likelihood<br />

function is the product over all categories:<br />

Ä �<br />

The quantity ÐÒ Ä � È ÐÒ Ä is m<strong>in</strong>imized.<br />

7.7.2 Probability Density Functions<br />

��<br />

�<br />

Ä � (7.12)<br />

The PDF parameterizations for Ñ�Ë, ¡�, �, and � are described <strong>in</strong> detail <strong>in</strong> Sec. 4.6.1.<br />

Top plots <strong>in</strong> Fig. 7-5 shows the Ñ�Ë distributions for signal events for Run 1 and Run 2. We use �Ñ�Ë �<br />

�� � ¦ � Å�Î� and �Ñ�Ë � ��¦ � Å�Î� for both Run 1 and Run 2. The background Ñ�Ë<br />

shape is the usual ARGUS shape but the � parameter is left float<strong>in</strong>g <strong>in</strong> the fit. Bottom plots <strong>in</strong> Fig. 7-5 shows<br />

the distribution of Ñ�Ë <strong>in</strong> the region � � �¡�� � �� ��Î <strong>in</strong> the side-band region. We f<strong>in</strong>d similar<br />

shapes <strong>in</strong> Run 1 and Run 2, so we float common parameters for the entire dataset.<br />

Figure 7-6 shows the ¡� distribution for signal events <strong>in</strong> Run 2 and the comb<strong>in</strong>ed Run 1 + 2 data. The Run 2<br />

parameters are similar to the Run 1 results so we use a common mean, �¡� � � ¦ �Å�Î, and resolution,<br />

�¡� � � �<br />

�� Å�Î, for the entire dataset. The mean of Ã�(ÃÃ) events is shifted by approximately<br />

�� Å�Î ( � Å�Î) relative to ��, where the shift is momentum dependent due to the boost. The two<br />

parameters (three from a second order polynomial m<strong>in</strong>us one of the normalization) of the background ¡�<br />

shape are left float<strong>in</strong>g <strong>in</strong> the fit. Aga<strong>in</strong>, we float common parameters for the entire dataset Run 1 and Run 2.<br />

MARCELLA BONA<br />

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