Higgs decays to ZJPsi, JPsiJPsi and YpsilonYpsilon (HIG-20-008)

CADI: https://cms.cern.ch/iCMS/analysisadmin/cadilines?line=HIG-20-008&tp=an&id=2332&ancode=HIG-20-008

Color Code

Color Meaning
BLACK Question or comment from ARC/conveneers
RED Authors know but not yet added/implemented
GREEN Answer from Authors
ORANGE Authors working on this item
BLUE authors answered but might need iteration with ARC

Comments for data-card

NP naming: in order for the NP to completely follow the HComb convention, it would be nice if you could add _hzz to the analysis-specific nuisances names


Lumi NP: you mention that for the lumi you are using a weighted average of the three years as NP. However, this is not taking into account the partial correlations among different years. Also, the value quoted by the Lumi POG for the full Run II uncertainty on the luminosity should be 1.8%, somewhat different than the 2.4% you are quoting. Please consider using the correct value of 1.8%, this should be fine as you are considering a single signal process inclusive on the three years. OTOH note that when using this 1.8% you would not be considering the partial correlations among years, but this should not have any substantial impact on the analysis results.

I changed to the recommended luminosity uncertainty of 1.8%.

Blinded limits: since you are using HybridNew to extract blinded limits, you should generate an asimov toy first (with GenerateOnly --saveToys) and use -D <file_with_toys.root>:toys/toy_asimov to have a blind limit, otherwise you are getting post- fit expected, which already uses data.


CMS_H_mean_e NP: In the ZJpsi->2e2mu and ZJpsi->4mu cards (so the separate ones) there are param lines in the datacards that are not associated with any params that actually exist in the input workspace. For example there is a parameter CMS_H_mean_e in the workspace, and a param line CMS_H_mean param 124.690 0.047 Please fix this and use consistent naming between datacard and workspace.


Background: Both in the AN and in the presentations given at HZZ/HIG PAG meetings you mention that this analysis uses "data-driven background". OTOH you also quote three MC samples used to model the background. Our understanding is that the background is not really data driven, but rather parametrized with an analytical expression using these MC samples. Can you please clarify on this?

The background is dominated by associated production which is sampled from the side-bands. In addition, possible peaking background is estimated from dedicated MC samples and is found to be negligible (far less than 1 event). These backgrounds are not included in the fit. Hence, we characterize the procedure as purely data driven.

Also, you have a NP associated to the background (CMS_bkg_frac param) only in the JJ4mu card. I think you should have NPs associated to the background in all your cards.

The parameters of the background shape functions are free to float. Therefore, they are not accounted for as NP – the inclusion of the background fraction which is floated in the JJ card was a mistake (double counting).

text2workspace: if you are using any particular model, please upload it to the repository. It would be nice, just for completeness, if you could also share the text2worskpace commands you use to generate the workspaces starting from the datacards, especially if they contain any particular option for the POIs ranges and/or re-definitions.


Data-card approval message

Thanks for uploading the datacards for review so early. After some iteration with the authors we're now happy with the cards so they are approved. If major changes to the structure are made between now and the pre-approval presentation, please do let us know so that we can double check. [ https://hypernews.cern.ch/HyperNews/CMS/get/HIG-20-008/3.html]

MUON POG approval message from Jonatan

Thank you for filling the muon documentation required for HIG-20-008[ https://twiki.cern.ch/twiki/bin/view/CMS/TWikiHIG-MUO][ https://twiki.cern.ch/twiki/bin/view/CMS/HIG20008muons]. I have reviewed it and I haven't found any outstanding issue, therefore you have the HIG-MUO green light.

JME approval message from Alexis

Thank you for completing the JME questionnaire. Given that you are using neither jets nor MET, we only have to wish you good luck with the rest of the analysis review! [ https://hypernews.cern.ch/HyperNews/CMS/get/HIG-20-008/5.html]

Comments From Giacomo

Abstract: I think the abstract is the only part needing a somewhat larger revision. The way It is written is a bit too convoluted imho. It would be better to rewrite it making the sentences more straightforward. For example the first sentence could read as “This paper presents the first measurement of the H->Z J/Psi decay. H->Z J/Psi candidate are studied in the four leptons final state exploiting the full LHC Run 2 dataset of 137fb-1. In addition, H and Z boson decays into pairs […] Different polarisation scenarios of the Z boson are studied.” etc.

⇒ We will rewrite the abstract in the next version.

L35 (second paragraph). Is it possible to include a table with the available predictions for the SM? Or add it in a new column in table 3?

⇒ It would be nice to summarize all measured and predicted BF in a table.


Majority of the Quarkonium channels do not have SM predictions:

1. No predictions for Higgs to Y(ns)Y(mS) (except Y(1S)(1S)) and Z boson to Y(nS)Y(mS) channels;

2. Feed-down quarkonium channels (H→ J\psi \psi(2S), H→ \psi(2S) \psi(2S)) have no SM calculations.

In the case of the H→ Y(1S)Y(1S) channel, SM theoretical prediction is not consistent:

Previous calculation using a phenomenological approach provides BF in order of 10^-5 [31]. But Latter, Ref.[35] assumes dominant contribution from indirect Higgs coupling, and provides BF in order of 10^-9 [35].

L35: I’m not sure it is a good idea to cite HL-LHC here, since this is a purely LHC paper. But this can be discussed with ARC and in CWR.

⇒ We removed HL-LHC sentence

L48: I should probably go through ref [29], but it is not clear to me how is it possible to have a BR>1 in any channel. Surely the maximum value should be 1-(whatever has been observed for other channel), isn’t it?

⇒ Ref.[29], page 4, last paragraph: 𝜎(pp→ H). BF(H->ZJ\psi) = 100 pb.

L51: Maybe I miscounted, but isn’t this the “second” class you are speaking of? Otherwise, mention explicitly which is the second when you introduce it.

⇒ L:22 A related class of such processes…….. ⇒ A second related class of such processes…...

L207: You select 4mu events as well, so this should be “event with at least 2 muons plus two leptons”

⇒ done

L210: does the 5 GeV cut applies both to Z and J/psi? If yes, “each dilepton resonance…”

⇒ done

L214-216: Invert the 2 sentences: put “A total of…” first, and “The range of…” second, so the range is already defined when you mention it. L214: you should specify which threshold you are referring to.

⇒ “The range of the four-muon invariant mass is chosen to exclude the region close to the threshold. A total of 164 (124) single candidate events are found in the 4μ(2e2μ) invariant mass between 112 and 142 GeV” is changed to “ ⇒A total of 164 (124) single candidate events are found in the 4$\Pgm$ ($2\Pe2\Pgm$) invariant mass between 112 and 142~\GeV. The lower range of the four-muon invariant mass is chosen to exclude the region close to the threshold.”

L230: “before unblinding”

⇒ done

L232: I think at the end of the line it should be Y (without (1S))

⇒ done

L259: either here or in the systematics section you should mention you did the bias studies and the effect of other shapes was found to be negligible

⇒ L259: Added sentence ⇒ “A possible bias in the choice of the background parameterization is probed with alternative functional forms and found to be negligible.”

L293: Please note there is a new prescription for the treatment of the luminosity uncertainty https://hypernews.cern.ch/HyperNews/CMS/get/physics-announcements/6191.html

⇒ Lumi uncertainty is changed to 1.6 % from 1.8 %

(Data-cards are updated. The expected BF will be updated in the next version.)

It is not necessary for preapproval I think, but is nevertheless better if you start including it Section 8: It would be nice to quote how much you are improving wrt previous results (for those channel where we had a previous result).

⇒ We will quote improvements in the next version.

Table 3: Can you add 2 columns for the results under the alternative polarisation hypotheses? And maybe a third one with SM expectations?

⇒ we will add a column for the polarization hypothesis in table 3 in the next version.

Finally it would be nice to have a summary plot of the results, maybe something similar in style to this one [ https://cms-results.web.cern.ch/cms-results/public-results/publications/HIG-19-001/CMS-HIG-19-001_Figure_014.png] but with BF instead of cross-sections

⇒ Some of our channels do not have SM predictions. Measured Upper limit in our channels are 3 (5) orders of magnitude smaller than the SM prediction in ZJ\psi (Quarkonium) channels. SM predictions for ZJ\psi (Quarkonium) channels are 10^-6(10^-9--10^-12). We prefer showing these result summaries in the table.

Comments From Maria, Nick and Jan

(*) General: It would be great if you can add a comparison of the expected results of this analysis and HIG-18-025, and point out any differences and updates since then.

⇒This concerns the channels H->JJ, H->YY, Z->JJ, Z->YY and we added a table in the next version of the AN (Table 19 and Text L 447 to L452).

L292: You give as source for the muon efficiencies the following link https://twiki.cern.ch/twiki/bin/viewauth/CMS/MuonReferenceEffs2017 - this is for 2017 only, so please update the information

⇒ For the 2016, 2017, and 2018 period the full list is given here: https://twiki.cern.ch/twiki/bin/view/CMS/MuonReferenceEffsRun2 which is included in the next version of the AN.

L329-331: What does it mean that "the event uncertainty is [...] less than unity"?

⇒ The resulting relative uncertainty is found to be less than one percent. ‘Unity’ is a typographical error.

L323-338: It does not become clear how you evaluate the momentum scale uncertainties given that the signal shape is obtained from a fit. Please clarify.

⇒ The change in the resonance mass was finally measured from the J/psi and Z di-lepton signals, in data and Monte Carlo. There we find, that the relative shift between the reconstructed MC signals and the signals in data when fit with the same parameterization is at about 0.2% (PDG values were generated). We conservatively assume that combining the signals leads to a 0.4% relative shift of the Higgs mass. Repeating the UL extraction with this shifted Higgs moves the UL by less than 1% in the 4mu (3% in the (Z->ee J->mumu) channel). We conservatively adopted the 1% in the 4mu, 3% in the 2e2mu channel.

Himal started out using the Rochester (electron) correction method and described this in the note. The scale factors are found to be one. Since we actually use the conservative estimates based on the control signals described above, we updated the text in the AN (L323 to L 333).

Figure 15: Do you have an explanation why the background fraction parameter has such asymmetric uncertainty and impact?

⇒ The impact plot is obtained with toy samples. The toy Monte Carlo demonstrates that this functional form, the combination of an exponential and a uniform function leads to an asymmetry in the fraction.

Figure 20: For the YY channel in the bottom right plot, the signal is far out in the tail, so the background from the fitted function must be negligible. Have you tested fit functions that have a larger tail than exponential + uniform? (I understand from section 7 that you tested different functions, but it is not clear if this led to any uncertainty or whether all tests were satisfactory)

⇒ Other parameterizations were exponential plus uniform and exponential plus exponential. In both cases we found that the extra contribution fits to zero fraction.

-- HimalAcharya - 2021-02-17

Topic attachments
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PDFpdf HIG20-008ResultsWithAsimov.pdf r1 manage 882.2 K 2021-02-17 - 21:20 HimalAcharya Expected branching fraction calculation and impacts of all the channels studied in HIG-20-008
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