Dear Mat, dear Steve, Congratulations with this interesting result, and well-written paper! Please find below our suggestions on behalf of the Nikhef group. Kind regards, Niels, Patrick, Jeroen General: ---------- 1) We find your treatment of the resolution confusing. In L.98 you say you fix to the simulation (implying the simulation is OK, but not saying so). In line 122 you imply this should be scaled by a factor 1.1. Why is that not the default fit then? 2) In L.82 you say you keep multiple candidates per event (about 1.15/event). But in L.124 you remove multiple candidates. (How do you select, in fact?) 3) L.126: what do you do with the fit to the wrong sign sample? Front page ----------- Title: why is Xib upright here and nowhere else? Page 1 ------ L.2: The Xib stats... (bsd). It took some time to understand what you mean. As the sentence is written it sounds like bsu and bds are an isodoublet each. Suggest to rewrite as "isodoublets composed of a Xibz (bsu) and a Xibm (bsd) state. L.2 A sketch of m vs J to indicate the full Xib spectroscopy would help! L.5 It would help to add the decay of Xib(5945)0: "and one other resonance, the Xib(5945) decaing to ..., reported by" L.5 You use a different name for Xib(5945)0 on L.22: Xib*0. Better to use the same naming convention consistently. L.6-7: here it sounds like the state is excited in the system. Re-order. L7-10: Suggestion to smoothen this sentence: "... system, which occur in different spin-states for the sq diquark and spin-parity J^P for the baryon: one spin-antisymmetric state with J^P=1/2+, one spin-symmetric state with J^P=1/2+, and one spin-symmetric state with J^P=3/2+. L.23-25: The mass difference _is_ the isospin splitting? L.25: isposin? Did you mean "mass splitting" ? L.30-31: Remove brackets. (No need to put this sentence in brackets.) Page 2 ------ L.60: you can remove daughter without loss of information. L.68: you can remove "for the daughter particles" without loss of information. (In any case, you need to remove the subsequent comma in L68.) L.70: nearest -> any (means the same but is clearer) L.72: Remove "about". The cut is at exactly 3.�� L.77: "that the Xib candidate passes..." Suggest to remove this sentence anyway, since it was said already in L51-52. L.79-80. This sentence reads as if _every_ pp collision contains 1.15 Xib candidates. The PRL reader cannot know that you mean in every selected��event. Suggest to remove the "After all selection requirements," And change "per event" into "per selected event". L.80: "Such multiple candidates" L.83: Projection is jargon. It is more clear to write: "The invariant mass of the Xib0 baryon in Xib0-pis candidates..." Page 3 ------ L97: What is meant with the weighted average of the 3 Gaussian widths? Is the RMS or adding the Gaussian widths in quadrature a better figure? Page 4 ------ Fig.2: It would perhaps be better to give a color version here already? L.104: "line shape" (2 words). L.104: It is more intuitive to introduce the acronym BW, rather than RBW. Suggest to change: "(RBW)" -> "(BW)" (Then BW can be used in L.121 and L.123.) L.107: uncertainty -> resolution (In fact, you could remove "within the experimental uncertainty" without loss of information. That is obvious when you say that it is consistent?) L.109-111: Do you really need to say that both peaks are 10 sigma? Any reader can make the same calculation.�� N/sigma_N is always smaller than the significance and is not a simple metric for it. We suggest to remove this sentence and just add ", with significance in excess of 10sigma" to the previous one. Page 5 ------ L.131: It is not clear what "The result" refers back to. Suggest to write: "The value m(D*)-m(D0)" L.132: keV is not in LHCb style. Use \kevcc. L.134+ For consistency, use same notation for result as in abstract. The style in the abstract is preferred. (Spelling out delta m on L.198 would also be more clear, probably.) L.135: We suggest to add the uncertainties in quadrature. In that case, it will be directly clear where the 0.50 uncertainty in the following result comes from. Page 6 ------ L.149: Why don't you show the cosTheta_h distributions? (At least in the supplementary material, but could even be included in the main text, as it is important information when interpreting the states you discovered?) You could consider to prefer the cos(th) distribution over the m(Xib0) plot of Fig.1? L.158: It is not clear what "A scaling factor of 0.1" means. To what is this applied? Suggest to rephrase. Page 7 ------ L.174: move "at LHCb" to the end and change to "in the LHCb acceptance", or more generally "at the LHC in the forward acceptance" Supp. material: Perhaps the number of delta m plots is a bit much?