Analysis of Single Top Polarization using Parton Level Atlas samples

3. Optimal basis/ Spectator basis

For the Optimal basis (s-channel) you have to take the incoming antiquark and the antilepton in the CM-frame of the top quark.
The Optimal Basis in the s-channel corresponds to the Spectator basis in the t-channel.
For the Spectator basis in the t-channel use spectator quark and the antilepton in the CM frame of the top quark.

4. Degree of Polarization

The degree of polarization is defined as D=(N--N+)/(N-+N+) where N- is the number of events with a negative polarized top and N+ is the number of events with a positive polarized top.

There are two ways to get the N- and the N+ from the histogram:

The first method means you just take the number of events at the left and right corner of the histogram (cos(θ)=-1 and cos(θ)=1 respectively). In the second method you actually count events and plug the total number of events with negative/positive polarized tops. This requires a fit.

The first method works as D is a ratio and using the actual number of N-/N+ we can simplify it by cancelling, so that we end up with the values at cos(θ)=-1 and cos(θ)=1.

5. ONETOP-samples

-- SarahHeim - 10 Mar 2008
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Topic revision: r23 - 21 Mar 2008, SarahHeim

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