arXiv subjects

Haroon Sagheer

Publications and source records attributed to Haroon Sagheer.

5 recordsLinked to original sources

arXiv2026

Probing Singlet Vector-Like Top Quarks in the Hadronic tZ Channel at the HL-LHC using Machine and Deep Learning Architectures

In this work, we study the single production of a vector-like singlet top partner $ T $ at the 14 TeV HL-LHC in the channel $ pp \to T j $ with $ T \to t Z $, $ t \to b W \to b j j $, and $ Z \to ν\barν $. Signal and background samples are generated with MadGraph5\_aMC@NLO v3.5.11, showered with Pythia 8, and passed through Delphes. The dominant backgrounds are $ t \bar{t} $, $ t Z j $, $ ZZ j j $, and $ W Z j j $ (including charge conjugates). A hadronic pre-selection ($ N_j \geq 3 $, $ N_b \geq 1 $, $ N_\ell = 0 $) is imposed as trigger, followed by optimized kinematic cuts. We perform multivariate classification with Extreme Gradient Boosting (XGBoost) and a Graph Neural Network (GNN) based on jet-level features. Sensitivities at 3000 fb$^{-1}$ are quoted using the Asimov significance, $ S / \sqrt{S + B} $, and an Asimov variant with a 20\% background systematic. The model parameters $ g^* $ and $ R_L $ are defined in Sec.~2, and a single global working point is used to avoid per-mass tuning bias. In the $ (g^*, m_T) $ scan, we present 2$σ$ exclusion and 5$σ$ discovery contours for $ R_L = 0 $ and $ R_L = 0.5 $. For $ R_L = 0 $, 2$σ$ exclusion corresponds to $ g^* \in [0.17, 0.49] $ ($ 0.16, 0.43 $) over $ m_T \in [1.8, 2.7] $ TeV, while 5$σ$ discovery corresponds to $ g^* \in [0.27, 0.44] $ ($ 0.26, 0.40 $) over $ m_T \in [1.8, 2.2] $ TeV for XGBoost and GNN respectively. For $ R_L = 0.5 $, the 2$σ$ reach is $ g^* \in [0.21, 0.48] $ ($ 0.20, 0.43 $) over $ m_T \in [1.8, 2.5] $ TeV, and the 5$σ$ reach is $ g^* \in [0.33, 0.43] $ ($ 0.31, 0.49 $) over $ m_T \in [1.8, 2.2] $ TeV, with the GNN yielding slightly stronger and smoother limits across the scan.

hep-ph↗

arXiv2026

Search for Vector-Like Singlet Top ($T$) Quark in a Future Muon-Proton ($μp$) Collider at $\sqrt{s} = 5.29, 6.48,$ and $9.16$ TeV using Advanced Machine Learning Architectures

In this work, we explore the discovery potential of Vector-Like Singlet Top quarks ($T$) at a future $μp$ collider with center-of-mass energies of 5.29, 6.48, and 9.16 TeV, providing a unique environment to probe beyond Standard Model limits. We analyze the $T \to Wb$ decay mode in both fully hadronic ($bjj$) and leptonic ($blν$) final states, offering a multi-channel assessment of $T$-quark sensitivity across a mass range of 2 to 5 TeV. Our methodology employs multivariate classifiers such as Boosted Decision Trees (BDTs) and Multi-Layer Perceptrons (MLP) to optimize signal-to-background discrimination in complex final states. The results demonstrate that the 9.16 TeV benchmark acts as a definitive discovery machine; even with 100 fb$^{-1}$ of data, the statistical significance exceeds $5σ$ up to 4 TeV masses. We identify a crossover effect where hadronic channels provide superior reach at intermediate masses due to higher branching ratios, while leptonic channels offer robustness at 5 TeV where purity limits detection. Incorporating a 20\% systematic uncertainty via Asimov significance ($Z_A$), we quantify the transition from fluctuation-dominated to systematic-dominated regimes at high luminosities. At 3000 fb$^{-1}$, regions with $g^{*} \in [0.20, 0.50]$ and $m_T$ up to 4 TeV are discoverable via the hadronic channel with MLP, and regions with $g^{*} \in [0.10, 0.50]$ and $m_T$ up to 5 TeV are accessible through the leptonic channel with BDT, highlighting the collider's potential to probe new physics beyond the Standard Model.

hep-ph↗

arXiv2026

Vector-Like Lepton Pair Production With Polarized Beams at Linear Colliders:Sensitivity Projections and Chirality Observables

We study pair production of a vector-like lepton doublet at polarized future linear colliders, focusing on the charged and neutral channels $e^+e^-\toτ^\prime\barτ^\prime$ and $e^+e^-\toν^\prime\barν^\prime$. The benchmark masses are $M_{\rm VLL}=1000,1200~{\rm GeV}$ at CLIC with $\sqrt{s}=3~{\rm TeV}$ and $M_{\rm VLL}=390,460~{\rm GeV}$ at ILC with $\sqrt{s}=1~{\rm TeV}$. Using the realistic polarization configurations LR$=(-0.8,+0.3)$, RL$=(+0.8,-0.3)$, LL$=(-0.8,-0.3)$, and RR$=(+0.8,+0.3)$, we evaluate tree-level production-level cross sections and construct observables designed to test the electroweak structure of the doublet. The charged channel is consistently larger than the neutral channel because it receives both photon and $Z$ exchange. In the LR configuration, the charged-channel rates reach $23.32$ and $20.28~{\rm fb}$ at CLIC, and $188.83$ and $129.04~{\rm fb}$ at ILC, for the two benchmark masses at each collider. We express rate reach through the projected visible-fraction requirement $f_{\rm vis}^{95}=3/(\mathcal{L}σ_{\rm prod})$, keeping the result independent of a specific decay selection. To quantify charged--neutral separation we use the absolute discriminator $D_σ$, which reaches about $0.546$ at CLIC and $0.542$ at ILC in the LR benchmark. We also find a stable observed asymmetry separation, $|ΔA_{LR}^{\rm obs}|\simeq 0.45$--$0.46$, between the charged and neutral channels. The corresponding production-level statistical projection gives sizeable $Z_A$ values for the benchmark luminosities, scaling as $\sqrt{\mathcal{L}_{\rm tot}f_{\rm vis}}$ under an equal LR/RL luminosity split. These results demonstrate that the beam polarization can provide a representation-sensitive diagnostic of vector-like lepton doublets, beyond a simple rate enhancement.

hep-ph↗

arXiv2026

Impact of Colliding Beams Helicity on the Production of Leptoquarks and Collider Experimental Parameters

Vector Leptoquarks (VLQs) have emerged as primary candidates for resolving discrepancies in the Standard Model, specifically within $B$-meson decay channels and the anomalous magnetic moment of the muon. This work presents a rigorous evaluation of VLQ pair production across $e^{-}e^{+}$ collision modes at future linear colliders with center-of-mass energies ranging from 14~TeV to 100~TeV. Our analysis demonstrates that longitudinal beam polarization is a transformative tool for enhancing signal sensitivity. We find that $e^{-}e^{+}$ annihilation consistently yields superior cross-sections compared to photon fusion processes across a mass range of 500--3000~GeV. By optimizing beam helicity to specific configurations, such as $P_{e^{-}} = -0.8$ and $P_{e^{+}} = +0.6$, the production cross-section can be maximized to 120~fb at $\sqrt{s} = 3$~TeV. We further establish that the Left-Right Asymmetry ($A_{LR}$) serves as a robust discriminator for the chiral structure of new physics, peaking at 0.16 under full polarization. Additionally, we show that effective luminosity can be enhanced to 95\% of the total luminosity, while high polarization degrees significantly suppress relative uncertainties in the effective polarization. These results provide a quantitative roadmap for optimizing discovery potential and minimizing systematic errors in future high-energy physics experiments.

hep-ph↗

arXiv2026

Unraveling Dirac Magnetic Monopoles with Muon Beams at TeV Energies Using Machine Learning

The focus of this paper is the production of magnetic monopoles Drell-Yan and the Photon-Fusion mechanisms to generate velocity-dependent scalar, fermionic, and vector monopoles of spin angular momentum $0,\frac{1}{2},1$ respectively at a future muon collider. A computational study compares the monopole pair-production cross-sections for both methods at various center-of-mass energies ($\sqrt{s}$) with different magnetic dipole moments. The comparison of kinematic distributions of monopoles at the generator and reconstructed level is demonstrated for both DY and PF mechanisms. We demonstrate the observability of magnetic monopoles against the most relevant Standard Model background using multivariate analysis techniques. Specifically, we apply three different classifiers based on neural networks, e.g., Boosted Decision Trees, Multilayer Perceptrons, and Likelihood methods, to evaluate their effectiveness. Our results highlight the efficiency and robustness of these approaches in distinguishing magnetic monopole signals from background noise.

hep-ph↗