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Optimal Mass Variables for Semivisible Jets
by Kevin Pedro, Prasanth Shyamsundar
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Submission summary
| Authors (as registered SciPost users): | Kevin Pedro |
| Submission information | |
|---|---|
| Preprint Link: | https://arxiv.org/abs/2303.16253v3 (pdf) |
| Code repository: | https://github.com/kpedro88/evn_svj_public |
| Date submitted: | 2023-07-18 11:49 |
| Submitted by: | Pedro, Kevin |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approaches: | Computational, Phenomenological |
Abstract
Strongly coupled hidden sector theories predict collider production of invisible, composite dark matter candidates mixed with standard model hadrons in the form of semivisible jets. Classical mass reconstruction techniques may not be optimal for these unusual topologies, in which the missing transverse momentum comes from massive particles and has a nontrivial relationship to the visible jet momentum. We apply the artificial event variable network, a semisupervised, interpretable machine learning technique that uses an information bottleneck, to derive superior mass reconstruction functions for several cases of resonant semivisible jet production. We demonstrate that the technique can extrapolate to unknown signal model parameter values. We further demonstrate the viability of conducting an actual search for new physics using this method, by applying the learned functions to standard model background events from quantum chromodynamics.
Author comments upon resubmission
List of changes
* abstract: "regular hadrons" -> "standard model hadrons"
* Section 1, paragraph 2: defined dark quark symbol χ where dark quarks are first introduced
* Section 3, paragraph 3: "will include" -> "may include"
* Figure 1, caption: now reads "Representative Feynman diagrams for leading-order production of a Z′ boson decaying to dark quarks χ (left), a single Φ boson associated with a dark quark and decaying to an SM quark and a dark quark (center), and a pair of Φ bosons each decaying to a dark quark and an SM quark (right)."
* Section 1, paragraph 5: added citation of ATLAS result, "A recent search from the ATLAS experiment sets limits on certain models of non-resonant $t$-channel SVJ production via Φ~\cite{ATLAS:2023swa}, but does not target resonant production."
* Section 1, paragraph 6: added sentence "In particular, Ref.~\cite{Kim:2021pcz} shows that for a fully visible final state where the target parameter is the theoretical mediator mass, the learned function is equivalent to the invariant mass calculation, and therefore we expect the EVN to produce optimal mass estimators in semivisible final states, as well."
* Section 2, paragraph 2: added sentences "The HV module simulates the dark sector dynamics using the Lund string model~\cite{Andersson:1983ia,Sjostrand:1984ic}; we use the default settings for the empirical parameters in this model, which are the values tuned for SM QCD. Different parameter values, or even a different dynamical model or generator software, could change the dark sector dynamics. However, such variations generally impact the formation and substructure of jets, rather than their final four-momenta, and therefore are not expected to have a significant impact on the event-level mass reconstruction pursued here."
* Figure 4: fixed errant negative sign in fit parameter value in legend
* Section 4.2, paragraph 1: fixed typo in sensitivity definition, now "S/√B".
* Section 4.2, paragraph 1: added sentence "The lower ptmiss values in the generator-level background imply that fewer events have high RT values, so this looser selection provides a level of background rejection similar to the realistic analysis."
* Section 4.2, paragraph 1: changed "QCD background" to "QCD multijet background".
* Section 4.2, paragraph 1: added sentences "The overall significance for each signal model and mass variable can be approximated by adding the significance of each bin in quadrature. This calculation shows that the artificial variable has a 3--5\% higher significance than \MT, while \MAOS has only a ${\approx}1\%$ higher significance." and changed "improvement" to "improvements" in the following sentence.
* Section 5.2, paragraph 3: added sentence "Computing the approximate overall significance shows that the artificial variable improves on MT2 by 17% for mΦ = 1000 GeV and 81% for mΦ = 2000 GeV."
Current status:
Reports on this Submission
Anonymous Report 1 on 2023-7-19 (Invited Report)
- Cite as: Anonymous, Report on arXiv:2303.16253v3, delivered 2023-07-18, doi: 10.21468/SciPost.Report.7529
Report
I would like to thank the authors for their careful consideration of my previous report. I am satisfied with their responses to points 1, 3, 4, and 5. I would like to request further changes regarding points 2 and 6. Please see below.
Requested changes
Regarding point 2 in my previous report, the authors should explain in the text why there is no offset in the fit of figure 4, as they did in their response.
Regarding point 6, I disagree that figure 2 puts the different searches in context given that the rates are strongly dependant on the Yukawa coupling, and the value that they have chosen is no more motivated than any other value. If the authors do want to keep figure 2, they should explain how the curves scale with the Yukawa couplings, and qualitatively describe what the figure would look like for a few other values of the coupling.
Author: Kevin Pedro on 2023-07-21 [id 3827]
(in reply to Report 1 on 2023-07-19)
2\. We added a note about this after the next-to-last sentence in the second paragraph of Section 4.1: “(The constant term in the linear fit is found to be very small and is therefore neglected.)”
6\. We added the requested context where the figure is mentioned in paragraph 3 of Section 2: “...shown in Fig. 2 for the chosen Yukawa coupling value y_dark = 1.0. Nonresonant production depends more strongly on y_dark than single production, while pair production primarily depends only on α_S; therefore, the relative fractions of the resonant production modes would increase for smaller y_dark values and decrease for larger y_dark values.”
Anonymous on 2023-07-19 [id 3821]
I thank the authors for considering my suggestions, I am happy with the changes and the the current version.