B2hh GFact Asymmetry Fitting page

The aims for the asymmetry fitter are the following

• Perform basic checks of current fitting package with toy data for Bd and Bs asymmetries.
• Add proper time pdf to the fitting package
• Add Bs→KK pdf to fit package
• Think about adding the other background pdfs (3 body, Λ's)
• Alter the parameters that are being varied by the minimiser to d, θ and γ
• Move to MC data/ real data (Bd) for first looks. So far 0.3fb-1 data is enough for asymmetry fitter

Most of the following is on my web page http://ppewww.physics.gla.ac.uk/~alison/B2hh.html where all the attached files are there and work. I have now stopped using my web page and will now just post all my results here.

Basic Checks with asymmetry fitter

1. B_d → π π

50 datasets were generated with 6099 events per data set using 0.68 b2pipi (sf1=1 and ssb = 0.68) and 0.32 combinatoric background (MassDistribution) mass distribution. The asymmetry fitter was used to fit for Bd asymmetries only with sf1'=0.68 and obtained the following:
Adir Bd - input was 0.38 and fitted was 0.3953 ± 0.0476 ( A^dir_Bd)
Amix Bd - input was 0.61 and fitted was 0.6503 ± 0.0311 ( A^mix_Bd)
Then re-ran same job with 150 data sets with 2000 events per data set and fitted for the following:
Adir Bd - input was 0.38 and fitted was 0.4338 ± 0.0196 ( A^dir_Bd)
Amix Bd - input was 0.61 and fitted was 0.6619 ± 0.0197 ( A^mix_Bd)
The asymmetry plot is shown here .

2. B_s → K K

50 datasets were generated with 6099 events per data set using 0.68 bs2KK (sf3=1 and ssb = 0.68) and 0.32 combinatoric background ( mass distribution ). The asymmetry fitter was used to fit for Bs asymmetries only with sf3'=0.68 and obtained the following Adir for Bd and Amix for Bs which in numbers are:
Adir Bs - input was 0.1 and fitted was 0.0811 ± 0.0275
Amix Bs - input was 0.25 and fitted was 0.1799 ± 0.0346

3. B_d → π π and B_d → K π

50 data sets were generated with 6099 events per data set using 0.68 bd2pipi and bd2Kpi (sf1=sf2=0.5 and ssb = 0.68) and 0.32 combinatoric background ( mass distribution ).The asymmetry fitter was used to fit for Bd asymmetries only with sf1'=sf2'=0.34 and obtained the following Adir for Bd and Amix for Bd which in numbers are:
Adir Bd - input was 0.38 and fitted was 0.298 ± 0.206
Amix Bd - input was 0.61 and fitted was 0.660 ± 0.062

Now using 150 data sets with 100k events per data set using bd2pipi and bd2Kpi (sf1= 0.845 and sf2=0.155 and ssb = 0.664, see Laurence's thesis, page 183). The asymmetry fitter was used to fit for Bd asymmetries with sf1'=0.561 and sf2'=0.103 and obtained the following:
Adir Bd - input was 0.38 and fitted was 0.4241 ± 0.0017 ( A^dir_Bd) and Laurence got 0.407 ± 0.033
Amix Bd - input was 0.61 and fitted was 0.6818 ± 0.0018 ( A^mix_Bd) and Laurence got 0.655 ± 0.024
The asymmetry plot is shown here . The pull plots show a large bias. The only difference was the large mass window I used (4800 - 5800 MeV) compared with Laurence (5229 - 5329 MeV). Hence I have re-run the same signal fractions in a 5fb-1 job (300 data sets with 100k events per data set) with the much tighter mass window and found the following:

Adir Bd - input was 0.38 and fitted was 0. ± 0. ( A^dir_Bd) and Laurence got 0.407 ± 0.033

Amix Bd - input was 0.61 and fitted was 0. ± 0. ( A^mix_Bd) and Laurence got 0.655 ± 0.024

The asymmetry plot is shown here .

4. B_d → π π, B_d → K π and B_s → K K

50 datasets were generated with 6099 events per data set using all 3 channels with sf1=sf2=sf3=0.333 and ssb = 0.68) and 0.32 combinatoric background ( mass distribution ). The asymmetry fitter was used to fit for Bd asymmetries only with sf1'=sf2'=sf3'=0.226 and obtained the following Adir for Bd and Amix for Bd which in numbers are:
Adir Bd - input was 0.38 and fitted was 0.4917 ± 0.0638
Amix Bd - input was 0.61 and fitted was 0.6852 ± 0.0456
Then re-ran the asymmetry fitter for the B_s asymmetries and found;
Adir Bs - input was 0.1 and fitted was 0.0416 ± 0.0606 ( A^dir_Bs)
Amix Bs - input was 0.25 and fitted was 0.1505 ± 0.0598( A^mix_Bs)

-- AlisonBates - 2010-08-06