Comments to LHCB-PAPER-2013-055

Abstract: 
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I found the abstract difficult to read due to a slightly confused period.
Can you try to remove a few commas and separate sentences?

General:
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- there are a few footnotes in the text. Beware that PRL does not accept them. Include the relative comments in the text.

Paper:
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- L320: you quote your largest systematic as 5% from the decay model. This systematic is the limiting factor in most precise evaluation of the branching ratios. Nevertheless this is not described anywhere in the text. How is this systematic evaluated? Don't you think that a brief description would help the reader and the journal reviewer to accept it like it is?

- L326: you use the central value from PDG for the f1(1285) mass. Do you apply any momentum calibration to your sample? If not, how do you protect from the 0.3% mass bias introduced by detector misalignments?

- L329: I'd like some clarification on the background description. Did you perform any study that justifies the use of a Gaussian for describing this distribution? Does it correctly take into account phase space effects?

- L342: how is this efficiency calculated? shouldn't it be mentioned in the paper?

- L351-352: I don't understand this sentence and it's importance in the context.

- Tab.2: It's pretty curious that most of the systematic errors have the same value of 2.0. While a reader in LHCb could guess where all these numbers are coming from, an external reader may get confused. A brief description on how they are calculated may help.

- L363: How are these factors calculated?

- L379: Rephrase removing the 'So we' at the beginning of the sentence. It's a bit too personal.

- Tab. 3: Is this table really needed? You could consider removing it if you need to gain some space. Furthermore, I don't think it's appropriate to a PRL article having unnecessary table.

- L390: I would rephrase like this: "This is the first time f(1285) is observed in ..."