LN6540 Searches for new physics in diphoton events in $p p bar_ colisions at $sqrt s Abe,F./Akimoto,H./Akopian,A./Albrow,M.G./Amadon,A./Amendolia,S.R./Amidei Dear Dr. Toback: The above manuscript has been reviewed by our referee(s). We ask you to consider the enclosed comments from the report(s). While we cannot make a definite commitment, the probable course of action if you choose to resubmit is indicated below. (x) Acceptance, if the editors can judge that all or most of the criticism has been met. ( ) Return to the previous referee(s) for review if available. ( ) Submittal to new referee(s) for review. Please accompany any resubmittal by a summary of the changes made, and a brief response to all recommendations and criticisms. Sincerely, Robert Garisto Assistant Editor Physical Review Letters P.S. Point 3 of the second report of B seems important to address. __________________________________________________________________ Second Report of Referee A The revised paper by Abe et al. is much improved from the first version. However, I still feel that the authors should include references to Bagger et al., Phys. Rev. D55, 3188 1997 and to Baer et al., Phys. Rev. D55, 4463 1997 for detailed phenomenology of the gauge-mediated SUSY breaking models. The authors argue that they include references to other models which yield diphoton events due to the breadth of their analysis. But in fact specific results are presented within the context of gauge mediated SUSY breaking models, so the relevant phenomenological works ought to be cited. __________________________________________________________________ Second Report of Referee C At this point, I recommend that LN6540 be published as a PRL. It is clear that the authors do not wish to go on record as to the relative likelihood of the EM cluster's origin. Perhaps they will change their mind in the PRD. Having given the reader no further guidance, on the grounds of lack of well-defined ensemble, they leave the readers to their own estimation of prior probability. They should not be surprised if readers conclude that a jet origin is most likely. On the question of ensemble definition, I note that they do not hesitate to propose an ensemble which allows them to estimate the contamination of the gamma-gamma sample. Further, if they have indeed done appropriate background estimations, then they have already done the estimation of the relative likelihood of the origin of the EM cluster from various SM sources. Each source considered has well-defined probability, and they have used these SM probabilities and their measured efficiencies and fake rates to estimate the backgrounds. Thus, they have simply chosen not to report this result, in spite of request from two of the three referees. Obviously, "as experimenters" the CAN and HAVE done more than estimate the probability of a jet fluctuating into something passing the electron cuts. As they state, the sum of the SM probabilities is small (the event IS unusual), but that does not impede giving the relative probabilities among the sources considered. Perhaps they mean to say that they do not in fact trust their calculations, or rather only trust the first-order conclusion that the sum of the rates is small. A vertex uncertainty of 30cm gives Et uncertainties larger than the stated (energy-dominated) errors for most of the 4-vectors, but the main point is to make clear the assumption used, and they have. __________________________________________________________________________ Second Report of Referee B The article is suitable for publication subject to the further minor revisions requested below. I thank Dr. Toback for his detailed response to my questions. My original comments are summarized below together with my responses. 1. I am happy to differ with the authors concerning my general feeling on the style of the paper and do not require any further action here. 2. Table I shows 3 events with extra leptons when 0.3+-0.1 was expected, which I felt was not in good agreement. The response suggests that this should be viewed as the sum of four separately estimated contributions, for each of which either zero or one event is observed. I think the discussion of Table I in the text should make this clearer, by giving the expected background for each contribution. 3. I asked whether Z backgrounds were included, given that two of the objects have a mass of 91 GeV. The authors say that they have in fact included such backgrounds but neglected to mention this for space reasons. I thank them for the clear explanation of how this was checked, but I certainly think that a statement to this effect should be added to the text. (For example "it is interesting to note that the invariant mass of the central electron and one photon is 91 GeV. While this might suggest a Z decay, careful estimation of backgrounds containing a Z boson was carried out and found to be much less than the WW gamma gamma contribution") Also, I think that the paper MUST clearly list ALL the backgrounds that were included in the estimate, or other readers will be misled as I was. 4. The nature of the forward "electron." (This was also commented on by referee C.) The textual change made here is fine; I guess I shall agree to differ with the authors on the relative probability of jet production. Readers should be able to judge this for themselves given the information provided. 5. Comparison with other published limits. I think it is rather novel of Dr. Toback to suggest that "since the referee was able to ... correctly discern that the limits set by D0 are more restrictive," then the text need only say that the limits are "similar". If the authors (understandably) do not wish to say that their limits are weaker than those of other experiments then they should say "may be compared with" or "complement similar analyses by" or some such. __________________________________________________________________