Past, present, and future of VBF

19 Oct 2022, 14:00 → 21 Oct 2022, 13:00 Europe/Zurich

40/S2-B01 - Salle Bohr (CERN)

Alexander Karlberg (University of Oxford), Gaetano Barone (Brookhaven National Laboratory), Mathieu Pellen (University of Freiburg), Simon Plätzer (University of Graz (AT)), Stephane Brunet Cooperstein (Univ. of California San Diego (US))

This event aims at boosting activities within the VBF subgroup of the Higgs cross section working group. In particular, it should initiate new projects within the working group.

The program is made of both invited presentations and voluntary contributions. During the workshop, ample time for discussion is planned in order to boost theory/experiment cross talk.

If you wish to give a presentation, please submit an abstract.

Note that we expect in-person speakers and strongly encourage the in-person participation.

Hostel Booking form.docx

Wednesday, 19 October

14:00 → 14:05 Welcome

Speakers: Dr Alexander Karlberg (University of Oxford), Gaetano Barone (Brookhaven National Laboratory), Mathieu Pellen (University of Freiburg), Simon Platzer (University of Graz (AT)), Stephane Brunet Cooperstein (Univ. of California San Diego (US))

Welcome_slides.pdf

14:05 → 17:50 State of the art

14:05 State of the art review of current VBF Higgs experimental results from ATLAS

Speaker: Antonio De Maria (Nanjing University (CN))

Slides_VBF_workshop_ADM.pdf

14:45 State of the art review of VBF Higgs results from CMS

Speaker: Cecile Sarah Caillol (CERN)

VBFH_CMS_Caillol.pdf

15:25 Coffee break

15:55 Theory overview of VBF

Speaker: Silvia Ferrario Ravasio

2022-10-18-VBF_WG_meeting.pdf

Thursday, 20 October

09:00 → 12:30 Parton shower in VBF

09:00 Limiting components of theoretical uncertainties in current VBF Higgs ATLAS measurements

Speaker: Ana Rosario Cueto Gomez (CERN)

VBFWorkshop_Cueto.pdf

09:45 Limiting components of theoretical uncertainties in current VBF Higgs CMS measurements

Speaker: Raffaele Angelo Gerosa (Univ. of California San Diego (US))

RG_VBFH_2022.pdf

10:30 Coffee break

11:00 Electroweak corrections and shower effects to Higgs production in association with two jets at the LHC

Speaker: Johannes Scheller

Scheller_VBF_CERN_v1.pdf

11:30 Parton shower and VBF, an overview

Speaker: Christian Preuss (ETH Zürich)

vbf_ctp.pdf

12:30 → 14:00 Lunch break

14:00 → 18:00 Selected topics on VBF and related

14:00 Deep-learning techniques for VBF Higgs searches: a case study in the invisible decay channel

Vector boson fusion production of the Higgs boson provides a relatively clean channel of investigation compared to the more abundant but rather chaotic gluon fusion production. It has been known for decades that the lack of QCD radiation in the central areas of the detector between the two tagging forward jets is a recognising feature of VBF processes. In this presentation, we discuss the possibility of Convolutional Neural Networks (CNNs) utilising this difference by looking at the inclusive event information in the form of the tower image. Taking the invisible decay of the Higgs boson as a proxy for a difficult signature due to the lack of knowledge of the Higg's decay products, we compare the performance of CNNs with univariate shape analysis of the dijet invariant mass and pseudorapidity separation, as well as with Artificial Neural Networks that take physics-motivated variables, and find that the CNN can put the most stringent bounds on the invisible branching ratio of the Higgs.

The use of inclusive event information, on the other hand, brings in the possibility of CNNs picking up artefacts of the simulation, which generally concentrate more on reproducing the physics of the reconstructed objects. We also study the dependence of the CNN on the parton shower recoil scheme (global and dipole) and the perturbative accuracy (LO and NLO) of the VBF Higgs production. Although there is a large difference in the training accuracies, we find that the validation accuracy of the dipole-NLO generated samples is very mildly affected by the type of signal data used during the training process, with a variation of 1.6% in the AUC. This points toward CNNs being able to learn the underlying physical differences regardless of the sub-par simulation used during training.

Speaker: Vishal Singh Ngairangbam

vbf_deep_learn.pdf

14:30 Experimental falsification of SMEFT

Vector Boson Scattering is central to our understanding of the Electroweak Symmetry Breaking Mechanism. Corrections to the Standard Model are conventionally studied in Standard Model Effective Field Theory (SMEFT). However, SMEFT can be cast in the form of the more general Higgs Effective Field Theory (HEFT). We expose the SMEFT-induced correlations on the coefficients of HEFT that, if found to generate tension with future data, would lead to the experimental falsification of the SMEFT framework. These correlations in VBF couplings are derived from the necessary symmetric point and analyticity of the SMEFT Lagrangian that allows the construction of the SMEFT expansion (as laid out by other groups), and properties at that point of the Higgs-flare function $\mathcal{F}(h)$ coupling Goldstone and Higgs bosons. We present amplitudes for VBF ($W_LW_L\to n\times h$) at the TeV scale, and show how SMEFT produces a theory prediction on cross-section ratios that does not depend on the specific value of the relevant Wilson coefficient (allowing direct experimental falsification of SMEFT).

Speaker: Alexandre Salas-Bernárdez (Universidad Complutense de Madrid)

ExperimentalFalsifiabilitySMEFT2.pdf

15:00 Looking at VBF processes from a polarization perspective

Studying the polarization of weak bosons provides crucial information to better understand the electroweak-symmetry-breaking mechanism that is realized in nature. We will report on the status of Standard-Model calculations of polarized di-boson production in the VBF channel at the LHC, with a focus on vector-boson-scattering and VBF Higgs-boson production. We will show a number of phenomenological results and address the extension of the currently available results to higher orders in perturbation theory.

Speaker: Giovanni Pelliccioli (Würzburg University)

gpvbfpol22.pdf

15:30 Towards WBF with realistic final states and anomalous couplings at NNLO

I present fully differential studies of WBF at NNLO QCD that go beyond stable Higgs boson production. For the first time at this order, decays of the Higgs boson at leading order and anomalous weak couplings of the Higgs boson are included. I will show that for the H -> bbar decay channel currently employed implicit fiducial cuts on stable Higgs boson transverse momentum are crucial and might need to be adapted when radiative corrections to the decay process are taken into account.

Speaker: Konstantin Asteriadis

wbf_cern_2022_asteriadis.pdf

16:00 Coffee break

16:30 High Energy Jets (HEJ) applied to inclusive Higgs + jets production

In order to further study the properties of the Higgs boson at the LHC, both gluon fusion (GF) and vector boson fusion (VBF) production modes have to be investigated. Within VBF cuts of large rapidity separation between jets, high energy effects are numerically significant and have to be taken care of appropriately. The High Energy Jets (HEJ) framework resums these large log(s/t) effects to all orders in the strong coupling, resulting in a suppression of the cross-section compared to fixed-order at large $\Delta y_{12}$ or $m_{jj}$. In the case of Higgs production plus two jets, this suggests that the GF contribution within VBF cuts is further suppressed compared to fixed-order predictions. More recently, inclusive Higgs production plus one jet predictions have been made available within HEJ, thus extending the resummation range of the phase space containing at least two jets from previous predictions and providing the first HEJ results for processes involving only one jet.

In this talk, I will summarise the impact of high-energy resummation in $H+\ge1$j and $H+\ge 2$j, including new comparisons to experimental data.

Speaker: Jérémy Paltrinieri

HEJ_VBF_JP.pdf

17:00 A sensitivity study of VBF-V to dimension-6 EFT operators at the LHC

Vector Boson Fusion (VBF) is a purely electroweak process and a fundamental tool to test the electroweak sector of the standard model (SM). Leptonic decay modes of the vector bosons are used to measure SM processes and search for physics beyond the SM, since they feature a clean signature and hence, a lower level of background.
We present a parton-level study in two VBF channels at the Large Hadron Collider that establishes the VBF sensitivity to a set of dimension-six operators in the Standard Model Effective Field Theory (SMEFT). Two different final state are studied, namely VBF-Z and the VBF-W.
The template analysis performed to define the optimal observables for each operator and process considered is shown.
Constraints are put on dimension-6 operators and compared to current limits extracted in VBS and diboson channels.
An outlook on the possible combination of different final states toward a global SMEFT fit is also given.

Speaker: Flavia Cetorelli (Universita & INFN, Milano-Bicocca (IT))

VBF-V_LHE_201022.pdf

17:30 Experimental potential on CP sensitive SXTS splitting.

Speaker: Benedict Tobias Winter (Albert Ludwigs Universitaet Freiburg (DE))

talk.pdf

19:30 → 21:30 Workshop Dinner

Dinner at Luigia Academy (https://www.luigiacademy.ch/) for those interested.

Friday, 21 October

09:00 → 12:30 Future of VBF

09:00 Experimental prospects of VBF measurements

Speaker: Yacine Haddad (Northeastern University (US))

Experimental-Prospects-VBF.pdf

10:00 Coffee break

10:30 Future of VBF and open issues

Speaker: Simon Platzer (University of Graz (AT))

slides-reduced.pdf

11:30 Discussion