The study of leptoquarks and their couplings to fermions with different chiralities provides a powerful tool for distinguishing among different leptoquark models. As a case study, we focus on two specific third-generation scalar leptoquark models, $\textit{S}$ and $\textit{R}$ , which differ in their electroweak quantum numbers and chiral structures of couplings to the top quark, leading to distinct top-quark polarization states. To enhance the efficacy of the analysis, we employ jet substructure techniques like Soft Drop, $\textit{N}$-subjettiness, and our custom $\textit{b}$-tagging method, along with other event variables. The analysis has been performed using both fixed radius and dynamic radius jet clustering algorithms. A multivariate analysis using a boosted decision tree (BDT) is performed to isolate signal from the Standard Model background. For a leptoquark mass of 1250 GeV, the analysis achieves a signal significance of up to 5$\textit{.}$3 $\textit{σ}$ at the 14 TeV HL-LHC. Furthermore, a $\textit{CL}$ -based profile likelihood estimator is applied to polarization-sensitive variables to discriminate between the two models. To enhance separation between the two models, an additional BDT classifier score is obtained by training a BDT network to distinguish between the $\textit{S}$ and $\textit{R}$ models. In the chosen signal region, the BDT classifier score provides a separation score of up to 3$\textit{.}$2 $\textit{σ}$, outperforming traditional variables such as $\textit{E}$ /$\textit{E}$ and cos $\textit{θ}$ .

India

Anupam Ghosh

Partha Konar

Tousik Samui

Ritesh Singh

Jet substructure probe on scalar leptoquark models via top polarization

The Inert Higgs Doublet model (IDM), assisted by Peccei-Quinn (PQ) symmetry, offers a simple but natural framework of a dark sector that accommodates Weakly Interacting Massive Particle (WIMP) and axion as dark matter components. Spontaneous breaking of U(1) PQ  symmetry, which was originally proposed as an elegant solution to the strong charge-parity (CP) problem, also ensures the stability of WIMP through a residual ℤ2 symmetry. Interestingly, additional fields necessitated by PQ symmetry further enrich the dark sector. These include a scalar field proprietor for axion DM and a vector-like quark (VLQ) that acts as a portal for the dark sector through Yukawa interactions. Moreover, this combination of the axion and WIMP components satisfies the observed DM relic density and reopens the phenomenologically exciting region of the IDM parameter space where the WIMP mass falls between 100 - 550 GeV. We investigate the model-independent pair production of VLQs exploring this region at the Large Hadron Collider (LHC), incorporating the effects of next-to-leading order (NLO) QCD corrections. After production, each VLQ decays into a top or bottom quark accompanied by an inert scalar, a consequence of the residual ℤ2 symmetry. Utilising relevant observables with a leptonic search channel and employing multivariate analysis, we demonstrate the ability of this analysis to exclude a significant portion of the parameter space with an integrated luminosity of 300 fb −1.

Unveiling desert region in inert doublet model assisted by Peccei-Quinn symmetry

The model-independent theoretical upper bound on the thermal dark matter (DM) mass can be derived from the maximum inelastic DM cross section featuring the whole observed DM abundance. We deploy partial-wave unitarity of the scattering matrix to derive the maximal thermally averaged cross section for general number-changing processes <math><mi>r</mi><mo>→</mo><mn>2</mn></math> (with <math><mi>r</mi><mo>≥</mo><mn>2</mn></math>), which may involve standard model particles or occur solely within the dark sector. The usual upper limit on the DM mass for <math><mi>s</mi></math>-wave annihilation is around 130 TeV (1 GeV) for <math><mi>r</mi><mo>=</mo><mn>2</mn></math> (3) and only applies in the case of a freeze-out occurring in the standard cosmological scenario. We consider the effects of two nonstandard cosmological evolutions, characterized by low-temperature reheating: (i) a kinationlike scenario and (ii) an early matter-dominated scenario. In the first case, early freeze-out strengthens the unitarity bound to a few TeVs for weakly interacting massive particles (WIMPs); while in the second case, the WIMP DM can be as heavy as <math><mo>∼</mo><msup><mn>10</mn><mn>10</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> due to a large entropy dilution.

United Arab Emirates

Nicolás Bernal

Sudipta Show

Unitarity bound on dark matter in low-temperature reheating scenarios

In this study, we critically evaluate the approximation capabilities of existing infra-red and collinear (IRC) safe feature extraction algorithms, namely Energy Flow Networks (EFNs) and Energy-weighted Message Passing Networks (EMPNs). Our analysis reveals that these algorithms fall short in extracting features from any N-point correlation that isn’t a power of two, based on the complete basis of IRC safe observables, specifically C-correlators. To address this limitation, we introduce the Hypergraph Energy-weighted Message Passing Networks (H-EMPNs), designed to capture any N-point correlation among particles efficiently. Using the case study of top vs. QCD jets, which holds significant information in its 3-point correlations, we demonstrate that H-EMPNs targeting up to N=3 correlations exhibit superior performance compared to EMPNs focusing on up to N=4 correlations within jet constituents.

Vishal Ngairangbam

United Kingdom

Michael Spannowsky

Hypergraphs in LHC phenomenology — the next frontier of IRC-safe feature extraction

We explore the pair production of third-generation scalar leptoquark at the Large Hadron Collider to next-to-leading order accuracy in QCD, matched to parton shower for a precise probing of the stemming model. We propose to tag two boosted toplike fatjets produced from the decay of heavy leptoquarks in association with notably large missing transverse momentum and consider them as the potential signal. Such a signal demonstrates the capability of a robust discovery prospect in the multivariate analysis with different high-level observables, including jet substructure variables. Various scalar leptoquark models predict different chirality of the top quark appearing from the decay of the leptoquark carrying the same electromagnetic charge. We make use of the polarization variables sensitive to the top-quark polarization in order to identify the underlying theory.

Debashis Saha

Satyajit Seth

Precise probing and discrimination of third-generation scalar leptoquarks

We examine the singlet-doublet fermionic dark matter model, where the non-thermal production of the dark matter in light of a non-standard cosmology demands a significantly large interaction rate than the typical radiation-dominated Universe. Despite being a model of freeze-in light dark matter and heavy mediator, the characteristic long-lived particle searches at the collider experiment and the displaced vertex signature do not help in probing such a dark sector since this non-standard interaction mandates nearly prompt decay. We make a counterproposal to probe such signal with di-fat-jets generated from the boosted decays of massive vector bosons and Standard Model Higgs, along with the substantial missing transverse momentum to probe the dark matter at LHC. Interestingly, substructure variables associated with these fat jets have an additional handle to tackle the extensive QCD background as it encodes implicit footmarks of their origin. We adopt the multivariate analysis with the booted decision tree to constrain the measured relic density allowed parameter space of dark matter in the presence of the modified cosmological scenario. Our study shows how the non-trivial expansion affects dark matter production in the early Universe and alters the required search strategies at colliders. This probe provides the best discovery prospect at the HL-LHC for extended parameter space now opened up in the dark sector.

Prasanta Das

Saumyen Kundu

Jet substructure probe to unfold singlet-doublet dark matter in the presence of non-standard cosmology

If coupled feebly to the Standard Model bath, dark matter can evade the severe constraints from the direct search experiments. At the same time, such interactions help produce dark matter via the freeze-in mechanism. The freeze-in scenario becomes more interesting if one also includes the thermal masses of the different particles involved in the dark matter phenomenology. Incorporating such thermal corrections opens up the possibility of dark matter production via channels that remain kinematically disallowed in the standard freeze-in setup. Motivated by this, we investigate such freeze-in production of the dark matter in a minimally extended <math><mi>U</mi><mo>(</mo><mn>1</mn><msub><mo>)</mo><mrow><msub><mi>L</mi><mi>μ</mi></msub><mo>−</mo><msub><mi>L</mi><mi>τ</mi></msub></mrow></msub></math> framework, which is also known to resolve the muon <math><mi>g</mi><mo>−</mo><mn>2</mn></math> anomaly. Here, the role of the dark matter is played by a scalar with a nontrivial charge under the additional symmetry <math><mi>U</mi><mo>(</mo><mn>1</mn><msub><mo>)</mo><mrow><msub><mi>L</mi><mi>μ</mi></msub><mo>−</mo><msub><mi>L</mi><mi>τ</mi></msub></mrow></msub></math>. The importance of incorporating the appropriate finite temperature corrections to freeze-in dynamics is aptly demonstrated in this study using the <math><mi>U</mi><mo>(</mo><mn>1</mn><msub><mo>)</mo><mrow><msub><mi>L</mi><mi>μ</mi></msub><mo>−</mo><msub><mi>L</mi><mi>τ</mi></msub></mrow></msub></math> scenario as a prototype.

Nabarun Chakrabarty

South Korea

Rishav Roshan

Thermally corrected masses and freeze-in dark matter: A case study

We explore a two-component dark matter scenario in an extended Kim-Shifman-Vainshtein-Zakharov (KSVZ) axion framework. This hybrid setup incorporates an extra SU(2) L  complex singlet scalar whose lightest component plays the role of one of the dark matter, while the QCD axion of the KSVZ model acts as a second dark matter candidate. In this work, we focus on accentuating the role of vector-like quark that naturally emerges in the KSVZ extension on the dark matter and collider phenomenology. Here, we demonstrate that the presence of this colored particle can significantly affect the allowed dark matter parameter space of the scalar dark matter by opening up additional co-annihilation as well as the direct detection channels. Moreover, the interaction between the color particle with the top quark and scalar dark matter provides a unique topology to generate a boosted-top pair with considerable missing transverse momentum at the LHC. Using jet substructure variables and multivariate analysis, here we show that one can already exclude a vast region of parameter space with 139 fb−1 integrated luminosity at 14 TeV LHC.

Top-philic dark matter in a hybrid KSVZ axion framework

The inert Higgs-doublet model provides a simple framework to accommodate a viable Higgs portal scalar dark matter candidate, together with other heavier scalars of mass 100 GeV or more. We study the effect of next-to-leading order (NLO) QCD corrections in this scenario in the context of the Large Hadron Collider. <math><mi>O</mi><mo>(</mo><msub><mi>α</mi><mi>s</mi></msub><mo>)</mo></math> corrections to the gluon-gluon-Higgs effective coupling have been taken into account in this study wherever appropriate. We find such corrections have a significant impact on various kinematic distributions and reduce scale uncertainties substantially. Fixed order NLO results are matched to the pythia8 parton shower (PS) and the di-fatjet signal associated with the missing transverse momentum is analyzed, as this channel has the ability to explore its entire parameter space during the next phase of the LHC run. A closer look at the <math><mrow><mi>NLO</mi><mo>+</mo><mi>PS</mi></mrow></math> computation indicates a sizable NLO effect together with a subdued contribution from associated production of the heavy scalar compared to the pair production, thereby leading to a refined analysis strategy during the multivariate analysis of this signal.

Precise probing of the inert Higgs-doublet model at the LHC

Vector boson fusion established itself as a highly reliable channel to probe the Higgs boson and an avenue to uncover new physics at the Large Hadron Collider. This channel provides the most stringent bound on Higgs’s invisible decay branching ratio, where the current upper limits are significantly higher than the one expected in the Standard Model. It is remarkable that merely low-level calorimeter data from this characteristically simple process can improve this limit substantially by employing sophisticated deep learning techniques. The construction of such neural networks seems to comprehend the event kinematics and radiation pattern exceptionally well. However, the full potential of this outstanding capability also warrants a precise theoretical projection of QCD parton showering and corresponding radiation pattern. This work demonstrates the relation using different recoil schemes in the parton shower with leading-order and higher-order computation.