"Observation of the B0s to psi(2S) eta and B0(s) to psi(2S) pi+ pi- decays"

Dear authors, 
Congratulations with this nice draft. We discussed it Friday 1 February
with the Nikhef group members.

General comments:
=================
- The introduction focuses on the comparison between the decay modes 
with a J/psi and a psi(2S). 
But what can we conclude from their difference or equality? 
What do the results tell us?
If no such theoretical motivation exists, it seems better to omit this comparison
in the introduction. 
We could then just mention that similar measurements for the J/psi final states 
were reported in Refs. [...]
If a theoretical motivation exists, we should give theoretical/phenomenological
references that discuss these decays, possibly with reference to 
http://arxiv.org/abs/1110.5490.

- The fit in Fig. 1a is very poor, which may be due to a wrong model. 
If you look between 5.55 and 5.6 GeV, the data undershoots the fit. 
Also is missing a partially reconstructed background from B(s)->J/psi eta X 
(where X could be a K0) below 5.2 GeV. 
Including this background could make the uncertainty of the B signal much larger. 
I see no mention of partially reconstructed backgrounds in the systematic section;
the analysis note is also quiet about it. 
Since the Bd->J/psi eta BF is known, why cannot we fix this in the fit? 

- Similarly in Fig. 3 the J/psiK* reflection is included, 
but partial backgrounds from B+->J/psiK2pi, Bs->J/psiPhipipi... are ignored.
And where does the very narrow shape of the K* come from?

Comments and suggestions in detail:
===================================
Abstract:
- Add "including the $\psi({\rm 2S})$" after "meson decay", 
  and replace "each mode" by "each of these modes".
- Replace "dileptonic" by "dilepton".
- Are the "third" uncertainties (B) independent?
  Write "corresponds to the uncertainties of the dilepton branching fractions of
  the $J/psi$ and $\psi({\rm 2S} meson decays" in stead of "comes from ... states".

Line 10, 11:
- Replace the sentence "... also has been recently studied by LHCb[2]" by
  "... has recently been reported by us, including the decay to P/psi eta' [2]."
- Move "The ... has not been previously observed" to line 17.
- Replace "... have been previously studied by the LHCb collaboration ... of ..." 
  by "... has been studied by us and the \pi^+\pi^- final state is found to 
  consist of decay products of ...".

Line 17:
- Replace "Although ... studied. In addition, the relative rates ... states..." 
  by "The decays B0s->psi(2S) eta and B0s->psi(2S) pi+pi- were not reported
  previously. Relative branching fractions of other final states ..."
  There is no need to repeat that J/psi pi+pi- is well known.
Line 20:
- Replace "branching fractions" by "branching fraction ratios".

Line 22: 
- Add "a" in "or a $\pi^+\pi^-$ system".

Line 62:
- Replace "Well identified muons ... greater than zero" by
  "Muons are identified by the particle identification detectors [17] if the
  probability to be a muon is larger than to be a hadron or an electron.
- It is not clear if L_h is the probability L_pi or (L_pi+L_K+L_p),
  as later L_pi and L_K are used individually.

Line 65:
- Add the number of degrees of freedom for the chi2.

Line 70-71: 
- Replace "... intervals (... tails))" by
  "... intervals that allow the acceptance of muon energies with radiative tails".

Line 72:
- Remove "Charged pions ... ndf < 5"
  This is already mentioned in line 61.

Line 83: 
- Remove "As previously mentioned, the".

Line 84:
- Remove "to remove background candidates".

Line 88: 
- Remove wrong definition of decay time (c\tau, with c the speed of light and
  \tau the mean proper life time of B meson).
  Alternatives are: 
  - "the invariant decay length, ct_{CM}, of the ..." and
  - "the life time in the CM system of the B0(s) candidate is required to be
    larger than 0.5 10^-12 s (0.15 mm/c)." 
% Note: compare to tau = 1.52 10^-12 s.

Line 99: 
- As we have a very simple model for the psi(2S)eta mass distribution, 
  why cannot we include its resolution in the fit? 
  If the reason is the stability of the fit with small numbers, do say so. 

Figures 1 (and 3): 
- Replace orange/yellow by a better visible colour for the B0 contribution line.
  It could be dot-dashed red.
 
Line 106:
- Replace "log L_B/L_S+L_B" by "log_e (L_B/L_S+L_B)".

Line 109:
- Add "to separate the signal and the background" after "sPlot technique".

Figure 2:
- Swap the horizontal axis titles of (a) and (b).

Line 127: 
- British versus American spelling consistency:
  In line 25 you use "center-of-mass" (American), 
  whereas here "summarized" (British) is used.

Line 130: 
- Add "a" in "using a partial wave analysis".

Line 131:
- Replace "the available data sample does not ..." by 
  "the number of signal events does not ...".

Line 134: 
- Since the spectrum is background subtracted, we can write here
  "from Bs->psi(2S) pi+pi- decays" instead of "from Bs->psi pi+i- decays".

Figure 4:
- The relevance of this figure and the corresponding text is not so clear.
- The description in the caption of the red filled area is not clear by itself. 
  Replace "shows ... ratio" by "shows the expected signal spectrum for the psi(2S) 
  channel derived from the measured spectrum of the J/psi channel" 
  and refer to the text.

Line 152: 
- Replace "simulation" by "simulated data".

Line 165: 
- Add "a" in "including a B0 signal".
 
Line 169: 
- Replace "of the nominal [19] value" by "around the nominal value [19]".

Line 193:
- It is not clear what is meant by "the ratio of cut efficiencies".
  This is a problem as it concerns the largest contribution.

Line 196: 
- Which acceptance is meant? Time? Geometry? 
  Should it be plural, as in "the efficiency ratios"
  Why do not we correct for the efficiencies in stead of taking
  the difference as a systematic uncertainty?

Table 3: 
- "Decay Model" may not be clear without further text.
  Replace "Decay Model" by "Reconstruction and selection efficiency" 
  or by "Mass dependence of efficiencies".

Line 213+ : 
- Is it obvious that arXiv:1204.1735 (hep-ph) 
  has no effect on the two Bs ratios?
- A remark that these are experimental time-integrated results may
  help the reader.

Line 218: 
- Replace "are seen" by "are found".

Line 222:
- Add "to come" after "more data".