Hi Concezio,
first of all: congratulations to the new world champion!
Second: Very good progress!
This looks like a real step forward.
Cheers,
Heiko
On Fri, 7 Jul 2006, Concezio Bozzi wrote:
> Hi,
> here are some results for the double ratio
>
> (signal/peakingBG)_MCenriched
> -----------------------------
> (signal/peakingBG)_MCdepleted
>
>
> as a function of mx. We use this double ratio, multiplied by the ratio
> (signal/peakingBG) in the depleted data sample, in order to fix the
> (signal/peakingBG) components in the mES fits on data after all cuts as
> a function of mx.
>
> The various signal (S) and peakingBG (P) components of this double ratio
> on MC can be computed on either:
>
> (1) the entire MC sample, by performing a 3-parameter fit to S, P and
> combinatorialBG (B)
>
> or
>
> (2) on separate "signal" (reconstructed Breco mode == true Breco mode)
> and "background" (reconstructed Breco mode != true Breco mode) samples.
> In this case, the signal sample is used to determine S, whereas the
> background sample is used to determine P and B.
>
> Method (2) has a number of advantages on method (1):
> - the uncertainty on S and P is smaller
> - the bias on S is reduced, since we don't risk to mix up/swap signal
> and peaking background due to the very similar functional forms of their
> PDFs.
>
> The spreadsheet attached to this message proves the above two
> statements.
Excellent!
> The upper part of the spreadsheet contains the results obtained with
> method (1), the lower part refers to method (2). Look e.g. at the
> errors on the peaking background numbers on the enriched sample on
> column E5-E14 for method (1) and E18-E27 for method (2). The same is
> true on the depleted sample (column Q) and for the signal yields
> (columns K and W).
>
> The bias in method (1) on the number of fitted signal and background
> events (columns I5-I14, U5-U14 for signal, AH5-AH14, AI5-AI14 for
> background) is also evident by comparing them to the number of expected
> events in the datasets (respectively: columns AI18-AI27, AI31-AI40 for
> signal, AH18-AH27, AH31-AH40 for background).
>
> The double ratios which come out are flat as a function of mx and are
> compatible with 1, see the light blue cells in the spreadsheet, or the
> attached eps file (The number for the last bin in mx is not meaningful
> since there are very few events in the mES plot).
>
> The bottom line is that the signal/peaking background in the mES fitss
> can be fixed in our data to the values which we obtain on the depleted
> sample, times a MC correction which turns to be about 1 within 10% and a
> ~10% uncertainty, which gets higher at high mx.
>
> This is not the end of the story, of course. The study needs to be
> repeated on the MC samples which we use in VVF (vcb+other, vubIN,
> voubOUT), since we have to fix the signal/peaking background components
> in there as well...
>
> Stay tuned, Antonio&Concezio.
>
