SciPost Submission Page
Proposal for simplified template cross-sections extension using $\cal{CP}$ observables in $t\overline{t}H$
by Carnelli Alberto
This is not the latest submitted version.
Submission summary
| Authors (as registered SciPost users): | Alberto Carnelli |
| Submission information | |
|---|---|
| Preprint Link: | https://arxiv.org/abs/2501.04837v1 (pdf) |
| Date submitted: | Jan. 13, 2025, 3:17 p.m. |
| Submitted by: | Carnelli, Alberto |
| Submitted to: | SciPost Physics Proceedings |
| Proceedings issue: | The 17th International Workshop on Top Quark Physics (TOP2024) |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
|
| Approach: | Phenomenological |
Abstract
The Large Hadron Collider (LHC) offers a unique opportunity to investigate $\cal{CP}$ violation in the Yukawa coupling between the Higgs boson and the top quark by studying Higgs production in association with top quarks; this is of fundamental importance, seeing that the $\cal{CP}$ properties of the Higgs boson are yet to measure with high precision. To address this, the focus of this work has been an extension of the simplified template cross-section (STXS) framework, devised to be sensitive to $\cal{CP}$ effects. Our study focused on $\cal{CP}$-sensitive observables across multiple Higgs decay channels, comparing their performances. The result indicates that the most efficient extension of the current binning used in the STXS framework, which currently uses the Higgs boson's transverse momentum $p_{T,H}$, requires adding one further split using $\cal{CP}$-sensitive observables. Between these observables, one of the best is the Collins-Soper angle $|\cos\theta^*|$, a variable derived from momenta information of the top quarks. We have investigated the improvement brought by our two-dimensional STXS setup and compared it to the currently employed methodologies, finding an increase in performances at an integrated luminosity of $300$ fb$^{-1}$. Moreover, our results highlight that this advantage seems to be present also at $3000$ fb$^{-1}$.
Current status:
Reports on this Submission
Strengths
Weaknesses
Report
Requested changes
1- Introduction: I suggest to rephrase the statement "that BSM theories predict a larger amount of CP violation in the Yukawa couplings with respect to other possible sources". While it is true that BSM theories can provide additional sources of CP violation beyond the SM, this is up to construction of the specific BSM theory, and not an imperative. So "can provide", "allow for" or similar seems more appropriate than "predict".
2- Bullet list below eq. (1): "g_t acts" (typo)
3- Last paragraph of section 1, "are tailored to the various channels and are not easy to combine." It is not directly clear the what is meant by by [search] channels. Searches in specific final states? Please make this specific. After all "channels" is used repeatedly thereafter.
4- Section 2: provide the MadGraph version number
5- Section 2, "applying a scaling factor of 1.14": A caveat that higher-order corrections might influence kinematic distributions seems in order here.
6- Section 3, "The effect of reconstruction effects (detector performance, etc) are taken into account by using scaling and smearing factors to the parton-level ttH events to produce realistic yields." is too vague. Provide details or appropriate references where these details are available (or directly the scaling and smearing functions in a code repository).
7- Section 4: define the "best observables" (what are b_1^lab etc.?) or provide a reference! And, why is cos\theta* not part of the list?
8- Provide the binning (bin sizes) used for obtaining the results in Fig. 1. For |cos\theta*| this is crucial. For p_T,H this is probably the STXS v1.2 binning, but it is better to give it explicitly. Also, how many events are there in each bin for the benchmark?
9- The improvement of limits on g_t and \alpha_t from adding |cos\theta*| is sizeable only in the b\bar b and multi-lepton channels. But, since the fit is dominated by the diphoton channel, the overall improvement is very mild, not to say marginal. This should be commented upon. Moreover, the combined result needs to be quantified in the text.
10- Conclusions, "the proposed two-dimensional binning outperforms the current STXS binning": as already requested in point 9, the "outperforming" needs to be quantified.
Recommendation
Ask for minor revision