From: FNALD::SMTP%"benn@physics.ucla.edu" 17-DEC-1997 16:32:49.92 To: TOBACK CC: Subj: Comments on diphoton PRL draft Date: Wed, 17 Dec 1997 14:30:00 -0800 (PST) From: Benn Tannenbaum X-Sender: benn@hepsun14 To: Henry Frisch , toback@fnald.fnal.gov, rebcdf@fnald.fnal.gov, David Stuart , yagil@fnald.fnal.gov, kuhlman@fnald.fnal.gov, mdshapiro@lbl.gov Subject: Comments on diphoton PRL draft Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Content-Transfer-Encoding: QUOTED-PRINTABLE Dear Bob, Dave and Henry and godparents, Following are the comments of the UCLA group (in particular, Jay Hauser, David Saltzberg, Jane Nachtman, H.C. Shankar and Benn Tannenbaum).=20 General comments: You tend to mix both tenses (present perfect and past) and voices. Abstract: There is too much jargon. We'd prefer to see something like "We have searched for events containing two isolated photons and missing transverse energy, jets, leptons (e mu tau), b-quarks or additional photons."=20 ** We don't think that most of this is jargon. We've just used big words to spell out exactly what it is we want to say. The ET and eta thresholds are important. Changing missing ET to missing transverse energy is a reasonable request but we've left it for space reasons. Also, this is common usage, especially in theoretical papers. Standard Model should be capitalized throughout.=20 ** We agree with you. However, PRL doesn't (all our PRL's have the lower case usage). We've left it the way it is. (Carla tells me she put in upper case when she submitted her PRL and they made it lower case without telling her). Remove the phrase "a high-Et" (you never define Et). ** Again the fact that the cluster has high-Et is very important. It would be nice to define all these things in the abstract, but then the abstract would become too long and unwieldy. Replace SUSY with Supersymmetry. ** If you feel strongly we can change this. We feel its clear, and are loath to add a longer word. Replace the symbol MET with the words missing transverse energy at the end = of the abstract. ** We've already define MET so why not use it? Again we are hurting for space. We've left it as is. Paragraph 1: You don't define E_t until later, but use missing Et here. Perhaps "... generate signatures with two photons (\gamma) plus missing transverse energy, jets, leptons, gauge bosons (W+-, Z0, \gamma) or b-quarks." ** Again we're hurting for space. However, we have changed the first ET to transverse energy. CDF has published several papers using the notation with chis for charginos and neutralinos. It is clumsy, but for consistency we'd prefer to see this paper use it as well.=20 ** You are quite correct. We argued about this at length in the Godparents meetings. It was decided that we should use what the authors of the models we are studying use. They use the N and C notation so we went with that. line 7: "...decay via () produces the \gamma\gamma..." ** Done. line 9: "... an unusual eegammagamma event" ** We like keeping the MET, also we didn't want to add the unusual since it takes up space. At the same place, you refer to data taken from 92-95, but down below you only use 85 pb-1. Is the 1a+1b photon sample that small?=20 ** You are correct. It is only 1b. 93-95. This has been fixed in the text. line 18: remove "proceed to" ** Done. Paragraph 2: Change the 2nd sentence to read "The magnetic spectrometer consists of tracking devices inside a 1.4 T superconducting solenoidal magnet."=20 ** We like the paragraph as it is. We think all the numbers are important. Theorists know so little about our detector, we felt it worthwhile. Remove the size from sentence 5. ** (See above) line 10: "momenta" ** Done. line 17: "... in the central (CES) and plug (PES) regions." ** We left this as is because we didn't want people to think that we are referring to the CEM and PEM as the CES and PES. line 21: remove the ' around preradiator. Also, insert "single" before photon, and use \gamma or photon (we'd prefer \gamma) everywhere.=20 ** We think the `' around preradiator are fine. We think the single is redundant and didn't want to have to change it everywhere because of space reasons. line 22: "... on a statistical basis from the difference in conversion probabilities."=20 ** We wanted to use the wording used in that reference. We left it as is. Paragraph 3:=20 line 1: "with" --> "containing" ** Containing is a funny word. This is not a box which `contains' photons. We've left it as is. Also, it's shorter. line 4: remove the hyphen in trigger towers, and replace transverse energies with E_T.=20 ** We think the hyphen is appropriate and have left it. The type of tower is is a trigger tower. It is a modifier. We have changed to ET. line 14: ...=A8photon cluster energies [6]...", removing "calculated with the offline photon algorithm..."=20 ** We think that this is more precise and left it as is. The reference is a really nice reference to the details of how we calculate energies. Paragraph 4: This paragraph is a bit cumbersome. Can you split it into a series of short= er sentences?=20 ** We've argued about this for awhile. It is cumbersome, however it is clear and very efficient for space. We left it as is. line 1: "We require for this analysis..." or "For this analysis, we require= =2E.." ** We left it as is. Author's prerogative. line 6: "and" --> "or" ** No...We require both. See CDF Note 4183. Paragraph 5:=20 How does this efficiency related to the events selected above? Which set(s) of cut(s) above is included in this? You refer to "the sample" several times and we were confused. 15% of what? 2663? If so, why is the sample purity so low? We realize this is a search, but 85% background seems enormous.=20 ** The efficiency is for the identification and isolation requirements. To be explicit these are requirements a, b, c and d. It is true that requirement a is also part acceptance. The diphoton sample is 2239 events, we estimate that 15% of these are prompt diphoton events. You are correct that 85% is huge. There is a reason we haven't done photons in exotics before. They are a pain. The problem is that there simply aren't a lot of handles on photons, and the backgrounds (dijets) are enormous. It simply is really hard to distinguish between neutral meson decay to multiple photons at high energy and prompt photons. It can be done, however, it requires a terrible hit in the efficiency. We had to make a decision, either go with high efficiency and a purity we could measure and understand, or go with low efficiency, a slightly better purity and no way to measure the purity. line 2: remove "control" and "2663". Insert a comma after "measured". ** We disagree with all of these. It is a control sample. The number of events gives on a sense of how well we are going to do statistically. There shouldn't be a comma after measured. line 3: insert a comma after "decays" ** I assume this comma was supposed to go with the earlier one. We decided to leave it as is. It's pretty clear. Paragraph 6:=20 According to the previous paragraph, the sample is 85% background. Does the relationship for sigma(\met) hold true for events that fake diphoton? Do you use this relationship elsewhere? Why not just multiply by root(2)? For events with the third photon, how do you order them? i.e. do you require 2 > 22 and 1 additional > 25 or 3 > 25? Why do you require 25 and not 22?=20 ** You've got a lot here. Yes, the sample is 85% background. We think that the resolution should hold because it is a measurement of events which deposit their energy in the electromagnetic calorimeter. Thus the resolutions should be similar and the comparison appropriate. This is discussed in more detail in CDF Note 4183. This relationship is only used to estimate the uncertainly on the met and thus the met distribution. It is also used to estimate the uncertainty on the met of the eeggmett event. The resolution on the MET is not just root(2) times the resolution on one component. For large values of the met it's is a decent approximation, but for small values it isn't. ** The additional photons are required to come in on events which pass the trigger. They are not ordered. In other words, any combination of photons is considered: if two pass the sample requirements and a third is present and has ET>25 then the event passes. Thus if there are three photons with Ets of 12, 12 and 25 then this event will pass. We require 25 GeV to be consistent with electron, muons, taus and b's. line 7: "In addition we remove..." --> "In the \gamma\gamma + \met search, = we also remove..." ** Done line 12: should that be \bigoplus and the end of the line? ** No. It's not added in quadrature. It's a parameterization of the resolution vs the Sumet. See CDF Note 4183 where this is discussed in great detail. line 16: remove the hyphen in top quark. ** No, the hyphen is appropriate as it is a modifier (or name) of the quark. Remove the last sentence of the paragraph. ** Done. Paragraph 7: You have some information in the paragraph and some in the table. Please put it all in the table and remove the text.=20 ** We thought it important to highlight the most important results in the text. Paragraph 8: Is this information necessary? Why not simply say the events are consistent with background?=20 ** A number of people have pointed out, correctly, that we observe 3 events with a lepton and have an expectation of 0.3. We felt that rather than cause a huge commotion we would let people know that these events are not particularly anomalous and why. Paragraph 9:=20 line 1: "that has" --> "with" ** We kept the "has" to be consistent with the later has. Paragraph 10: Remove the sentence "The probability of an electron..." ** We think this is one of the most important parts of the whole paper and have left it in. Paragraph 11: This paragraph really is the crux of the paper-- it has the calculations for the SM production of such an event. However, we found it to be rather unclear. For example, you refer to "jets". Do you mean 4-jet QCD? or W+2 jets? What is the rate at which a jet can fake an electron? a photon? How often does a photon fake an electron and vice versa? Those are very important numbers which should be included.=20 ** We also think this paragraph is very important. However, I'm afraid I'm not sure what you are asking. We mean any source which include jets which fake electrons, photons and/or met. We have included 4-jet QCD and W+2 jets in our background estimates, however they are so small compared to the others that we have not mentioned them explicitly. We have considered so many sources that we simply could not list them all, and have referred the reader to the PRD for these numbers. Similarly we have pointed the reader to the PRD for the fake rates. Without the production rates, the fake rates are not useful and we simply don't have room to add them here. We have left it as is because including those numbers would ask more questions then they answer. Last sentence: ".. have led to speculation [1], we do not claim evidence of new physics based on one peculiar event."=20 ** A nice shorter version. However, we have used author's prerogative and left it as is. Paragraph 12:=20 Does Ws really need an apostrophe? Also, 3 should be written as three. ** Done. Thanks. Paragraph 14: line 5: remove "a total of" ** Done. line 7: replace "only the" with "anomalous" ** That doesn't read better. We left it as is. line 8: replace "To provide... " with "For comparison, we estimate the acceptance for \chi_2^0\chi_2^0 production to be 5.4% in this model." ** We think it's clear. Also, the average theorist wouldn't understand why we have use N2N2 production since the cross section is so small. Thus, we left it the way it is. Paragraph 15: We were a bit confused by the sign of mu-- are they really the same here as in the figure? Also, you have one < and one >.=20 ** Ooopsss. When I re-made the figure, the mu got switched. The figure has been fixed to say mu<0 as in the text which is correct. The best limit for C1 and for N1 use different signs of mu. That is correct. Thanks! line 2: "[1]e" --> "[1e]" ** That's a tex problem. We left it as is. Paragraph 16:=20 Sentence 2: "We find good agreement with Standard Model expectations, with the exception of one event which has large \met and in addition to the two photon has a ..."=20 ** We think the extra emphasis is correct. We don't want to claim this is an exception, we want to say it is a possible exception. References: in [1]: Bhattacharaya and Mohapatra are misspelled. Also, you need a . and not ; at the end.=20 ** You are correct, we misspelled Mohapatra. You misspelled Bhattacharyya. We fixed the ;. Good eye. We're impressed. [4] To what paper do you refer? There is no information at all. Does it exist? Does it have godparents? Has it been submitted to the collaboration? We don't feel this is a legal reference.=20 ** After lengthy discussion it was decided that all details which are not in this paper should be put into the accompanying PRD and reference here. This is what the godparents wanted. The status of the PRD is that it is basically my thesis which is now done and handed in (i.e, public record and an appropriate legal reference). The plan is to take my thesis and put it into PRD format (a la David and Sacha). The Godparents are the same as for the PRL and it will go to them soon. However, I should point out that there is nothing in the thesis which is not in the CDF Notes. [16] and [17] need . at the end. ** You are correct. These have been fixed. [19] To which event do you refer? The anomalous one? If so, say that. ** Done. [23] needs . ** Again you are correct. This has been fixed. Figures. 1: Much too small. Do you really need all four? Perhaps only the lower two. There are no units on missing E_t. Why not change the y-axis label to merely "Events/5 GeV"? The (N_jets) in the caption is confusing. Please remove it. If you feel you must have all four plots, then the comparable ones should have identical axes.=20 ** We think these plots are important. The lower plots are appropriate for large mass new particles, the upper plots are appropriate for lower mass particles. We have added GeV to the plot axis. We used dN/dMet since it's more correct. Again, if you feel strongly we can change it. If we used the same y-axes for both plots it would look silly. You wouldn't be able to see anything for the Et>25 plots. 2: In the figure you have mu > 0 and in the caption you have mu < 0. Also, why not add a theory line for mu < 0?=20 ** As pointed out above, the line should be mu<0. Its a typo. We chose one line because it has a specific meaning, i.e, the lowest limit line. No other line is comparably compelling. =09=09=09=09=09=09-Benn (for the UCLA group) ** Thanks again.