From: SMTP%"robinson@cepheid.physics.utoronto.ca" 2-NOV-1997 16:27:12.06 To: TOBACK CC: Subj: Date: Sun, 2 Nov 1997 22:27:06 +0000 (GMT) From: Andrew Robinson Reply-To: Andrew Robinson To: toback@uccdf.uchicago.edu, frisch@uccdf.uchicago.edu, reb@hep.anl.gov, stk@sgi6.hep.anl.gov, yagil@fnald.fnal.gov, mdshapiro@lbl.gov cc: cdf_toronto@helios.physics.utoronto.ca Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Dear Authors and Godparents, Recently, the Toronto group met to review the first draft of the paper entitled "Searches for New Physics in Diphoton Events in ppbar collisions at sqrt(s) = 1.8 TeV". We find the draft to be a readable description of an important physics result, and certainly support it's prompt publication in PRL. ** Thank you. This having been said, there are a number of things that we feel could be done to improve the presentation of the analysis. We have divided our suggestions into two categories. In the first, entitled "General Comments", we describe a number of concerns that we have with the general direction of the presentation. A number of minor details are relegated to the subsequent section, "Specific Comments". Finally, we would like to thank the authors of the paper and the supporting documentation for all the effort that they've put into the diphoton search in general and the characterization of the eeggMET event in particular. ** Thank you. Cheers, Andrew Robinson for the Toronto Group. TORONTO COMMENTS FOLLOW ************************************************************************* Although we appreciate the thought that went into the typesetting of the draft, our preference is still a double-spaced draft with a larger font. We find this easier to read and edit. Also, when there are 50+ lines per page, referring to a particular line can be tedious. ** Ok. There is a double space draft available of the second draft on my home page if you like. Most people referred to the line number within a paragraph. http://hep.uchicago.edu/cdf/toback_home.html GENERAL COMMENTS: ================= 1) Although we feel that the complete discussion of any possible signal events is important in any search paper, we also feel that the emphasis of this paper is on the one anomalous event, rather than on what models can be excluded based on the diphoton dataset. We would like to see a more traditional approach taken, where a set of selection criteria is defined, ostensibly before the data is looked at, and then limits are placed on any interesting exotic models, whether they include two electrons in the final state or not. This is particularly true since the identity of the Plug EM cluster in the eeggMET event is subject for debate. We feel that this is a well-motivated search even without the eeggMET event, and that this point should be reflected more clearly by the line of discussion followed by the paper. ** We agree that the analysis is well-motivated even without the event and could be written in such a way to look more like the traditional search paper. This is especially true given that the literature is very rich with new physics models which predict the diphoton +X signature. We agree that it would be nice to add more detail about the search results and set limits on all the important new models. However, this event was found before the searches and it, as well as the searches, are very much part of the culture. Most of the theory is based on the event!!! It would be disingenuous to not address the event head on. Another key point you make is about the plug cluster. It is really important to realize (as discussed in the PRL and extensively in CDF Note 3892) that if the cluster in the plug is not an electron, this makes the even MORE unusual not less unusual (less easy to interpret possibly, but not less unusual). Unfortunately, given the space limitations, we have removed a fair amount of text and we are still well over budget. Space simply does not allow for the additions to make the paper look more traditional. In either case, after lengthy discussions with the GPS and others we feel strongly that the focus of the paper and the detail on the event should not be changed as it would be disingenuous to our audience. Furthermore, much of the additional detail will be given in the PRD. 2) This having been said, we find a discussion of the details of the eeggMET event both interesting and useful. However, we feel that there is an important omission in your discussion. In particular, after reading your discussion in paragraph 10, which ends with "We simply do not have enough information to establish the origin of this cluster.", we are left with no understanding of why the plug EM cluster does not make a reasonable photon/tau/jet candidate. We found your description of the problems associated with interpreting this cluster as an electron enlightening, and feel that the paper would benefit from a similar discussion of the other obvious hypotheses. ** Another good point. The GPS have discussed this at great length and felt that a discussion should not really start unless there is enough room to do it justice. Unfortunately, there is no room for such a discussion; as PRL is well over budget. This is why we have referred to the PRD and thesis where these issues are be discussed in more detail. 3) The paper would also benefit from an increased discussion of the sources and expected magnitudes of the diphoton signal. You state that you measure the fraction of events in the sample having two prompt photons to be 15% with a large uncertainty. Is this what you expect a priori? We also feel that the discussion of backgrounds, now relegated to Ref. [6], should be more self-contained. ** The cuts were set to have high efficiency. We think it is important to point out that this is not a cross section measurement, it is a search for events which are not from the Standard Model. Again, we are over budget and there is no room for side issue like a measurement of the purity. This is more appropriate for the diphoton cross section measurement paper (which is in progress) and the PRD. 4) We feel that other searches for SUSY, particularly our own, need to be referenced in the introductory part of this paper. In addition to this, there are limits from LEP-1.5 that the interested reader may find relevant. In particular, there is an Aleph preprint (hep-ex/9710009) that also documents a search for models motivated by the CDF eeggMET event. ** This is not a search for Supersymmetry. It is a search which is sensitive to many models one (or many) of which is SUSY. We just set limits on SUSY models since they lend themselves well to limit setting. Again, there is no room for such comments, and they take away from the coherence of the paper. SPECIFIC COMMENTS: ================== Everywhere: - Please replace "b's" with "b quarks" ** Done - Please try to avoid using symbols before you've defined them. (eg: N_1 in second sentence) ** Point well taken, however this is defined in the references. TITLE: We find "New Physics" ambiguous. How About "Search for Anomalous Production of Diphoton Events..." ** Hmmm...There are lots of new types of physics we are looking for. We don't want the reader to think we are comparing the total diphoton cross section to expectations. We believe the title is clear and kept it the way it is. Abstract, line 1: We suggest replacing "production of missing E_T..." with "production of events containing missing E_T..." ** We think the text is clear and kept it the way it is. Abstract, last sentence: Please replace "SUSY" with "theoretical" ** These are SUSY models. Standard Model predictions are theoretical as well. We have left it as is Paragraph 1, Line 8: We would prefer not to refer to "Run I" here, this is jargon, and we don't feel that it adds much to the paper. ** You are correct that Run I is jargon. This paragraph has been fixed. Paragraph 1, Line 14: Please state the uncertainty on the Integrated Luminosity. This analysis places limits on the cross-section of a SUSY model. ** The uncertainty on the luminosity is not really appropriate in the introductory paragraph. Given that there is no space to discuss in detail the large number of systematic errors taken into account in the limits, we have chosen not to give this error. It simply opens more questions that it answers and we are over budget for space. Paragraph 2, Line 7: We suggest expanding this sentence to read "...used to identify SECONDARY VERTICES ARISING FROM b hadron decays.". ** There is no space to add this comment. Paragraph 2, Line 13: We suggest expanding this sentence to read "...measurements OF CHARGED PARTICLE TRAJECTORIES between..." ** There is no space to add this comment. Paragraph 2, Line 16: We find your description of the calorimeter awkward. How about replacing "The calorimeter, constructed..." with "The calorimeter system is constructed of projective electromagnetic and hadronic towers and is comprised of three subsystems. A central barrel calorimeter surrounds the solenoid coil and covers the region eta < 1.1, while end-plug calorimeters cover the region 1.1 < eta < 2.4. Finally, forward/backward modules cover the high eta region from 2.4 to 4.2.". In this description, please note the conspicuous absence of the term "pole-pieces of the magnet", formerly used to describe our plug calorimetry. ** This paragraph has been significantly shortened. We do not find the use of the term pole-pieces problematic and feel that the text is clear. Paragraph 2, Line 21: We find that "transverse" conveys more information that "2-dimensional". ** These profiles are in the Z direction as well and are not just transverse. Paragraph 2, Line 23: Please replace "drift chambers" with "proportional wire chambers" ** Done. Paragraph 2, Line 26: We suggest truncating this sentence after "...statistical basis" ** We may use this suggestion if after all else fails we need another half line. However, we think it is important to say at least a little about how the photon purity is measured. Paragraph 3, Line 2: Please replace "...by THE three-level trigger..." with "...by A three-level trigger..." ** We only have one trigger. This one is it. Paragraph 3, Line 11: We suggest replacing "...isolation requirement of less than 4 GeV in a 3-by-3 array of trigger towers..." with "...isolation requirement THAT THERE BE less than 4 GeV in a 3-by-3 array of CALORIMETER towers..." ** In the first part of the sentence we feel that the text is clear and like our version better and so have kept it. The second point would be misleading. There are two calorimeter towers per trigger tower. This is made more explicit in the new version. Paragraph 4, Line 1: Please replace "...selection criteria offline:" with "...selection criteria to define our data sample:" ** We have chosen the shorter version for space reasons as well as it is less wordy. Paragraph 5, Line 5: Is there any way that we could make "...approximately flat in E_T." more quantitative? Failing this, this sentence conveys limited information. ** There are errors on the efficiency and it tells you a great deal if you were a theorist and wanted to make a toy model of the detector. We feel the text is clear and a more quantitative description would be wordy and out of place in the text. Furthermore there is no room for such a description. Paragraph 6, Line 1: You actually search through the CANDIDATE events that you have selected. Most of these events are background from neutral hadronic activity. May we suggest : "We search the diphoton CANDIDATE events for the presence of anomalous E_T OR jets, electrons, muons, tau's, b QUARKS, OR additional photon CANDIDATES." ** This is a good point. However, given the proximity to the purity estimate we think it is redundant and wordy. Thus we have left it as is. Paragraph 6, Line 3: Once again, could you please write out "CALORIMETER towers"? ** Again, these are not calorimeter towers. They are trigger towers which contain two calorimeter towers. Paragraph 6, Line 11: Could you please replace Missing E_t with "Missing E_T Vector". ** It makes the sentence awkward. We have left it as is. Paragraph 9, Line 2: We suggest replacing "the largest missing E_T in the diphoton distribution..." with "...the largest missing E_T among all diphoton candidates..." ** Done. Paragraph 9, Line 11: We are not sure how this reasoning applies to say, energy loss due to a jet hitting a crack in the calorimeter... ** It implies that most of the imbalance is caused by the electromagnetic objects. If the met were due to a jet hitting a crack in the calorimeter, we would see such a jet and an imbalance with it. Paragraph 9, Line 19: We suggest replacing "...the total system..." with "...the `eeggMET' system..." ** We think it is clear and have left it as is. Paragraph 10, line 19: Once again, we suggest replacing "new physics" with something more specific, like "anomalous production of diphoton events". ** I assume you mean paragraph 11. We have chosen the shorter version since for space reasons, it is clear and the alternative you suggest would make the sentence awkward. Paragraph 11, line 3: Please replace "...passing the electron requirements and Missing E_t,..." with "...passing the electron identification and Missing E_t selection criteria,... ** We think it is clear and have chosen to add the additional words for space reasons. Paragraph 11, line 6: Please replace "...production of SM WWgg and ttbar, as well..." with "... SM production of WWgg and ttbar FINAL STATES, as well..." ** The WWgg and ttbar are NOT final states. They are intermediate states. The leptons and photons are final state particles. Paragraph 11, line 11: Please add "production" to the end of this sentence. ** This would be redundant. We have chosen to leave it as is. Paragraph 12, line 14: Please replace "gauge-mediated breaking" with "gauge-mediated symmetry breaking...". ** Since not all light gravitino models are gauge-mediated we have simply removed the reference. Paragraph 12, line 17: We prefer "second order process" to "loop" ** We have differed to the theorists who use the "loop" terminology. Paragraph 13, line 1: "...SPYTHIA Monte Carlo PROGRAM". ** We have stuck with the conventional usage of Monte Carlo and omitted the word program. Paragraph 13, Line 12: We suggest removing the reference to "model builders" entirely, and simply state the acceptance*efficiency. ** We think that this is an important point. Without it people don't know why we've given the information. Paragraph 15, Line 6: We suggest replacing "sits on the tail of the E_T distribution" with "has unusually large E_T". ** Done Paragraph 16, last Sentence: Are these acknowledgements standard? Do we still have collaborators supported by the Sloan Foundation? ** I believe you are correct. This has been fixed. References: Reference [1] : We feel that it would be more correct to break this into 8 separate references. In d), a comma is required after the authors. Also, in h), no comma before et al. ** Done Reference [6] : Please replace "in CDF" with a comma ** Done. Reference [10] " Please replace "...with both photons with E_T..." with "with both photons HAVING E_T..." ** We like with better. Reference [15] Needs to be fixed up a bit before this become a preprint. ** Done References [16] and [19] should end with periods. ** Done Reference [17] Is this really of any use to a PRL reader? ** We have removed it for space reasons. Reference [21] The author's name should come first. ** Done. Figures: Figure 1 Caption The last sentence of the caption: "c) and d) the same plots with photon E_T > 25 GeV." would be better off as "Figures c) and d) are the same plots as a) and b) with photon E_T > 25 GeV". ** We think it is clear as it is and have left it. Thanks again for all your hard work. ** You're welcome.