Search for Large Extra Dimensions in the Diphoton Final State at the Large Hadron Collider
Entry on CERN Document Server for Draft 1
General comments:
The paper is well organized, short and well focused. We have two general comments:
1) We do not agree with the separation of this paper from the similar public PAS EXO-10-19 ( for example Tab 1 is the same in both papers). The two analyses combined would show a much more organic effort. We suggest the inclusion in this paper of the results of EXO-10-19.
2) Quite often the explanations are so dense that they are difficult to follow.
Inline comments:
l.15: (EM) is the “diphoton” the only “diboson” final state allowed? if other final states like ZZ are possible, you should specify why they are suppressed, similarly to what is written for fermionic final states.
l.15-25 (NC+NP): The reader might wonder why D0 has done the 2-jet and dielectron analyses and we did not. We should explain the status/reason for not having done it.
l.25: (EM) all the “scales” in the paper are in GeV/c^2 apart this where they are in TeV
eqs.1, 2, 3: (EM) are these equations really needed? Naively one can interpret them as a toolbox to convert limits on M_S between the different models, but this seems to be not the case if one looks at the values in Table 3, e.g. M_S(GRW) != (pi/2)^(1/4) M_S(Hewett)
l.48-49: (EM) why the threshold of the double-photon trigger is larger than that of the single-photon trigger? If the single-photon is prescaled, you should mention it.
l.53 (NC): The eta-cut value of 1.4442 is peculiar. What is our resolution in eta? DO we really know eta to the 4th decimal point?
(NP):Since this value is due to the exclusion of the 2 outermost ECAL barrel rings, has to be mentioned?
l.60-73 (NC): this list is hard to follow. Why not separate the points (i),(ii),(iii) using also new lines?
(NP): ideally one would like to read that isolation criteria are applied both to charghed tracks and to e.m. and hadronic energy depositions within defined DeltaR acceptances around the photon directions
l.65-66: (EM) specify if the “rectangular strip” is centered around the direction of the photon candidate
l.74-82: (EM+ NP) difficult to follow what it was done. Also about the optimal choice for |eta|, we found the tone of the explanation too confidential. Perhaps just say that you choose the barrel/endcap boundary and this was driving the M(gamma-gamma)>500 GeV choice. Furthermore in the rest of the paper it is not clear how the intermediate region is used.
l.77-79 (NC): “We alternate between…” it does not sound very good. Just quote the result.
l.81-82: (EM) GeV→GeV/c^2 (same in Table 1 headings). BTW: change “500< M_gammagamma GeV” to “M_gammagamma>500 GeV”
l.83-84: (NC+EM) This explanation is really too short, and you end with a scale factor compatible with one. why is it needed? Just quote that you have checked with Z→ee the MC prediction
l.83-84: (NP) Comparing to EGM-10-006 the efficiency was computed on the data Zee sample and than corrected by the same factor for the difference e/gamma.
l.89-97 (NC): The K-factor choice needs a longer explanation. It's difficult is a reader has to go to a reference to figure-out this choice. Flat in pt?
l.103: (EM) remove “,” after sample
l.105: (EM) “orthogonal to each other” → “independent”
l.118: (NP) why the error on K factor is 0.3 here and 0.1 in l.96?
l.125, 137, 173: (EM) GeV→GeV/c^2
Fig.1, top left and right (NC): The plot is dominated by statistical fluctuations. You need to reduce the binning by at least a factor of two.
l.133.135 (NC): Is the word “relative” needed?
Fig.2 (NC): the overflow bin is very confusions. best would be to remove it, otherwise you need to explain it. The 2 Ms predictions are dominated by statistical fluctuations. Is it possible to have smoother curves? The legend n_ED can be confused with the expression in line 141 “n_ED events”.
l.141(NC): change “n_ED” with “n_Signal” l.141 (NC): Dont' introduce a new symbol S, just called it “sigma x BR”. Also this “S” can be taken with something related to M_S.
l.142: (EM) Perhaps it is worthwhile to remark that the signal efficiency does not depend on the specific model
eq.4:(NC+EM) what are the coefficients A and B? why are they needed and how the affect the limits on eta_g? Change sigma_ADD =⇒ sigma_total. Otherwise it seems the sigma due to the model ADD.
l.145-148: (EM) this discussion seems to be specific to the HLZ description
Fig. 3 caption: n ⇒n_ED (to be consistent).
l.152: panel
l.154: (EM) 1/M_S^4 (n=2,95%)=0.078 TeV^-4 → 1/M_S^4=0.078 TeV^-4 95% CL with n_ED=2
l.165: not clear why the contribution above the M_S threshold should be set zero (the fact that it is non perturbative does not mean that is finite or small…)
l.166-167: n → n_ED
l.181-183: remove the sentence “While this analysis…M_S”
Table 2: (EM) These are the systematic uncertainties on what? on the extracted signal cross section S?
Figure 2: (EM) what is the accumulation in the last bin? What are the grey/black bands on top of the MC histo?
Figure 3: (EM) in the caption n→n_ED. In the left pane, why points are alternating above/below the dashed line? Is it because of fluctuations due to the limited MC samples used for the signal?
Table 3: (EM) is there a simple explanation why the HLZ limits are not monotonically decreasing as a function of n_ED?
EM: Ernesto NC: Nicolo NP: Nadia