Dear all,
Here are my (and Pieters) comments on PAPER-2014-039 ("First observation of a baryonic $B_c^+$ decay"). Textual suggestions are in attachment. I will submit to CDS on Tuesday.
These are the most important comments:
1) We would like a stronger first paragraph, where the motivation is optimally presented for the PRL reader. (a) We suggest to move L.12 - L.17 to the 2nd sentence; "The baryonic decays of B mesons are important, ... in the low mass region." (b) We suggest to move the 'prediction' of L.190 to the first paragraph. (c) Q: does a similar measurement also exist in Bs or Bu decays?
2) L.127 Here you correct the measured mass by +0.20 MeV due to FSR. (a) Q: How is this usually done within LHCb? Did we always have such a correction to the mass measurement? (b) Q: The uncertainty to this correction is 0.03 MeV. Does that purely come from MC statistics, or does the uncertainty include theoretical uncertainties as well?
3) L.143 You discuss a new selection for the BR(Bc) measurement compared to the M(Bc) measurement. Q: To reduce the systematics, you decrease the yield from 23.9 to 19.3 events. Since the statistical unc is dominant, is this reduction in statistics indeed compensated by a smaller systematic unc?
4) L.151-154 and Tab.2. We could not follow how you determined the single-track efficiency. (a) Q: How did you use Lc->pKpi or D*->D0pi events? (b) Q: Does the single-track efficiency only refer to tracking efficiency on reconstructable effects? (c) Q: Wat do you mean with "Reco. of p,pbar" in Tab.2 ? Is that the same single-track efficiency? (d) Q: How is the unc due to the acceptance of 0.7% determined, in Tab.2 ?
5) L.135 The systematic uncertainty of the combined result is larger than the systematic unc of your measured value, that is one of the inputs. In App. A you explain a bit more: in the combination you weight the inputs using their total uncorrelated unc. Then, presumably, you add the correlated sys uncertainty to the final result. But how do you determine the total systematic uncertainty on the final result?
Cheers, Niels
On Fri, 4 Jul 2014, Tjeerd Ketel wrote:
Dear all,
We will circulate the comments on both papers latest on Monday. Please, send your comments by reply.
Niels and Tjeerd
On Fri, 4 Jul 2014, Tjeerd Ketel wrote:
Dear all,
After the masterpresentation of Lennart we will be back on Vidyo around 10h40 for the discussion of the two papers.
Best regards, Tjeerd
Citeren Tjeerd Ketel tjeerd@nikhef.nl:
Dear colleagues,
Long Bfys Meeting Friday 4 July at 9:30 in H331 and Vidyo
9:30 - 9:50 Staff meeting (only permanent staff)
10:00 - 10:50 Master presentation by Lennaert Bel: "Measurement of the branching fractions of Bs0 to Ds-(+) K+(-), Bs0 to Ds- pi+ and B0 to Ds- K+"
11:00 - 12:00 Discussion of LHCb-PAPER-2014-035 "Observation of overlapping spin-1 and spin-3 states at mDbar0K- ~ 2.86 GeV/c2" Deadline : 08-Jul-2014 Link : https://cds.cern.ch/record/1711270
12:00 - 12:30 Discussion of LHCb-PAPER-2014-039 "First observation of a baryonic Bc+ decay" Deadline : 09-Jul-2014 Link : https://cds.cern.ch/record/1712264
The material can be found at http://agenda.nikhef.nl/conferenceDisplay.py?confId=2877 and will be protected by lhcb, etc.
Vidyo link in Nikhef Bfys Meeting (at Institutes->Nikhef of Friday 14 March 2014) https://indico.cern.ch/event/307385/ protected by PIN 1328.
Best regards, Tjeerd