Hello, Werner, Thank you again for the careful reading of the draft. In what follows, we list our replies. The updated version (which now finally conforms with the EPJ-C style) can be found at http://www-f9.ijs.si/~krizan/herab/open_charm/paper/paper-v5.1.ps In the same directory there is also a record of all questions and answers during the display period (looks like we will be left with only yours). The questions that arose during the refereeing process, are kept in the subdirectory referees, http://www-f9.ijs.si/~krizan/herab/open_charm/paper/referees/ Yours Peter >> ---------------------------------------------------------------------------- >> >> >> Hello, >> >> looks like a nice piece of work; >> it is remarkable how much one can get out of these data! Thanks! It took several people several years to finish, there are five (5) related PhD theses that came out during these years... >> >> Scanning the paper, I noticed a few things, partly trivial, partly not >> quite. >> >> Abstract: "have been measured" appears twice. Replace second by >> "are given for" or so. Done >> >> Page 2, line 6 from bottom "50 mm2" should read maybe "(50 mm)2" ? >> Done >> Section 3: active and passive voice mixed in paper. Mostly >> "was performed" but there are a few "we demanded" etc. Suggest to >> search document for "we" and rephrase. Replaced almost all, left a few (e.g. in the Summary), where we think 'we' is more appropriate. >> >> Page 4, line ~8 from bottom: "Taking into account ... the limited >> acceptance of the detector ... one finds sizable backgrounds". >> I don't think small acceptance makes backgrounds worse! Right. Left out. >> >> Page 5, line ~9 of 3.1: change to "and pions: While" Done. >> >> Middle of page, zeta cut: the cut is described as cut on pt of >> D0 daughters but as defined includes D0 momentum? Text corrected. >> >> Table 2: in the caption, define what is what (b, d, zeta, L), e.g. >> "L_pi is the Pion likelihood, with the normalization L_pi + ... = 1". We think that the caption would become too long, and the definitions of all variables would actually be duplicated, so we prefer to simplify this to 'Selection criteria; the definitions of variables are given in the text.' >> "not optimized" -> "chosen a priori" >> "optimized" -> "optimized using background data and signal MC" Done >> >> By the way, in the low-statistics limit, optimizing on Signal_Mc/ >> sqrt(background_data + ...)is almost as dangerous as optimizing on >> signal_data, since one selects downward fluctuations in the background. >> Works only in case of good background statistics. We have chosen very wide sidebands to accumulate more statistics; for details see the note (http://www-f9.ijs.si/~krizan/herab/open_charm/note_061017.ps.gz), table 9. >> >> Fig. 3 and associated text: should mention that a Poisson-statistics >> likelihood fit is used, otherwise the low counts and >> empty bins would cause trouble Done. >> >> Section 4: does the MC generate multiple interactions to simulate >> their effect on efficiencies? Should be mentioned. It does (Fig 41 in the note). Added to the text. >> >> Page 11, text after eq. (8): mention that one indeed finds alpha >> \approx 1 in the data, and refer to section 5.5 Done >> >> Page 12, "The sum of D cross sections accounts for 89+-4% of charm >> cross section. Unfortunately I cannot look up ref 22 right now, >> but I don't understand how this is calculated. Relative to an >> independently >> measured charm cross section? Unlikely, then the error would much much >> larger! Using a charmed baryon cross section? This needs to be explained! The idea is that if we had measured the production of all possible ground state c-hadrons ( including the c-barions), the sum of measured cross sections would be equal to the ccbar production cross section. Now we have only D0, D+, Ds, but this already accounts for a large fraction. Taking the measured fractions of D0, D+, Ds in the fragmentation of c quarks (i.e. the probability that c quark handronizes in a given D meson) from the data collected at e+e- colliders, this number is 89%. I have added an explanation in the text. >> >> Dito at the end 5.1: "The resulting charm cross section per nucleon >> is..." >> Again, not clear where this number comes from. See above. >> >> Fig. 5: >> Our data agree with models for D0 but fall well below the model curve >> for D+. On the other hand, we say that D+/D0 is understood in simple >> isospin models (I guess, feeddown from D*). This is inconsistent >> unless the model curves violate the isospin arguments! In Fig 5 the curves were taken from the predictions, while the normalisation ('k-factor') is determined from a fit to all existing data. According to Lourenco+Woehri (ref 1), the k-factors could be different for different final states, so the normalisation is left free for each mode independently. Now to the 'simple isospin' argument. If you assume isospin symmetry between D+ and D0 and take P_V (the fraction of vector meson final states) from measurements, you can calculate (assuming feeddown from D*) the D+/D0 ratio. I would say the term 'simple' is somewhat out of place. I have altered the text so that this is now better explained. >> >> Page 14, Description of how the Pt cross section is obtained: as far as >> I understand (it's hard to understand from the description), a fit in pt >> is used to get the background? If yes, all the resulting data points are >> correlated, and not independent. We think that the method is well described in the text. For the background parameters the sidebands are included in the simultaneous fit. >> >> I believe it is "we fit" and not "were fitted" I am not sure which "were fitted" you refer to. I found both OK. >> >> Page 15, first lines: we use x_b = 0.062 from E791. On the other hand, >> I would expect that the cutoff of the power law at x_b is related to mass >> effects, and I would guess that X_b scales more or less as 1/sqrt(s). >> Indeed >> x_b is of order m_b/E_cm. I don't see a good reason why x_b should be >> the same for E791 and us. To determine the impact of a particular choice of xb, and the related systematic error, we repeated the determination with the extreme case xb=0. Only small differences were found and were included in the sys. error. See the note for details. >> >> Page 15, last line: "It is similar to the world average value of 0.1" >> Yes it is "similar" in some sense but it's about 1.5 sigma away and >> that should be mentioned. If might well be that the true value differs >> for e+e- and pp since the mechanisms are not 100% identical. Right. I changed it to: It marginally agrees (within $1.5\sigma$) with the world average value of 0.10$\pm$0.02 of measurements in $e^+e^-$ collisions~\cite{PDG}. >> >> Line 9 of section 6: always a "," before "respectively" Thanks, we missed it before. >> >> a few lines down: again "0.27+-0.09+-0.05 is in agreement with". >> Should not go uncommented, see above. "... marginal agreement..."? Done. >> >> Reference: none of the initials has a ".". Is this the journal style? No. By mistake I took the EJP style file instead of EPJ... Sasha Lanyov actually asked me the same question, but it did not help at that time, I was sure I did it right. The paper has now been fitted to the proper style. A few places need some tuning (e.g. table 2).