Investigating the Production of Leptoquarks by Means of Zeros of Amplitude at Photon Electron Collider

Leptoquarks are one of the possible candidates for explaining various anomalies in flavour physics. Nonetheless, their existence is yet to be confirmed from experimental side. In this paper we have shown how zeros of single photon tree-level amplitude can be used to extract information about leptoquarks in case of $e$-$\gamma$ colliders. Small number of standard model backgrounds keep the signal clean in this kind of colliders. Unlike other colliders, the zeros of single photon amplitude here depend on $\sqrt{s}$ as well as the mass of leptoquark along with its electric charge. We perform a PYTHIA based simulation for reconstructing the leptoquark from its decay products of first generation and estimating the background with luminosity of 100 fb$^{-1}$. Our analysis is done for all the leptoquarks that can be seen at $e$-$\gamma$ collider with three different masses (70 GeV, 650 GeV and 1 TeV) and three different centre of momentum energy (200 GeV, 2 TeV and 3 TeV). The effects of non-monochromatic photons on the zeros of amplitude under laser backscattering and equivalent photon approximation have also been addressed.Comment: 46 pages, 14 figures, 15 tables, accepted in EPJC. The effects of non-monochromatic photons have been include

Distinguishing Leptoquarks at the LHC/FCC

In this article, we deal with how to distinguish the signatures of different Leptoquarks at the LHC/FCC if all of them lie within similar mass and coupling range and can be produced at present and future colliders. It has been found that hard scattering cross-sections and angular distributions can be used to differentiate scalar and vector Leptoquarks. On the other hand, final state topology and determination of jet charge can separate Leptoquarks with same spin even from same SU(2)L multiplet. We performed a PYTHIA8 based analysis considering all the dominant Standard Model (SM) backgrounds at the LHC/FCC with centre of mass energies of 14, 27 and 100 TeV for scalar (S1) and vector (U˜1μ) Leptoquarks. We see that confirming evidence of scalar Leptoquark at 14 TeV requires 1000 fb−1 of integrated luminosity, whereas the vector Leptoquark can be probed with very early data. But, at 100 TeV with 1000 fb−1 of integrated luminosity, scalar Leptoquark of mass 3.5 TeV and vector Leptoquark of mass more than 5 TeV can be probed easily

Strategies to Distinguish Signatures of Beyond the Standard Model Scenarios in Present and Future Colliders

Different theories have been proposed to address the questions, discrepencies and anomalies which the Standard Model (SM) fails to explain. These theories are referred to with a generic name, theories Beyond the Standard Model (BSM). They extend the particle fields or the gauge group of SM in pursuit of serving their purposes. They, therefore introduce new particles or interactions or both. Different BSM theories may suggest partuicles with different spin and gauge representations within the similar mass range. This leads to the challenge of identifying the signature of one or more such BSM scenarios at particle colliders, well distinguished from other BSM models as well as from SM backgrounds. In this doctoral work, we have principally considered a particular class of the BSM models, the Leptoquarks. They are coloured particles with spins 0 and 1, and share tree-level interaction vertices with a lepton and a quark. We study their signatures in different particle colliders, each collider characterising a particular trait, say spin or the gauge representation of the leptoquarks

Zeros of amplitude in the associated production of photon and leptoquark at \varvec{e}-\varvec{p} collider

Though various extensions of the Standard Model with higher gauge group predict the existence of leptoquarks, none of them has been observed yet at any of the colliders. In this paper, we study the prospect of several past and future e-p colliders like HERA, LHeC and FCC-he to detect them through radiation amplitude zero. We find that the leptoquarks showing zeros in the tree-level single-photon amplitudes at e-p collider lie within the complementary set of those exhibiting zeros at e-γ collider. We present a PYTHIA-based analysis for HERA, LHeC and FCC-he (run II) to detect the leptoquarks with masses 70 GeV, 900 GeV and 1.5 TeV (2.0 TeV) respectively through radiation amplitude zero

Probes of anomalous events at LHC with self-organizing maps

Abstract We propose an Unsupervised Learning Algorithm, Self-Organizing Maps (SOM), built on a neural network architecture, for the probe of a rare top decay, mediated by Flavor Changing Neutral Current (FCNC), to charm and the Higgs boson, with the Higgs boson further decaying to a pair of b-quarks or a pair of gauge bosons ( $$W^{\pm }/Z$$ W ± / Z ) in a boosted regime. Ideally, the particles originating from the decay of the boosted top lead to the reconstruction of a large-R jet, comprising three-prong substructures, with b- and c-tagged subjets. The SOM algorithm has been demonstrated as a model-agnostic anomaly-finder for probing the rare decay at the LHC, by mapping distinct signal and background regions to separate non-overlapping clusters on the Kohnen map. This helps to identify signal regions with higher signal significances. We also discuss the robustness of this algorithm, especially for other BSM probes with model-agnostic and model-dependent searches

Investigating the production of leptoquarks by means of zeros of amplitude at photon electron collider

AbstractLeptoquarks belong to the possible candidates for explaining various anomalies in flavor physics. Nonetheless, their existence is yet to be confirmed on the experimental side. In this paper we show how zeros of the single-photon tree-level amplitude can be used to extract information as regards leptoquarks in the case of e–$$\gamma$$γ colliders. A small number of standard model backgrounds keep the signal clean in this kind of colliders. Unlike other colliders, the zeros of the single-photon amplitude here depend on $$\sqrt{s}$$s and on the mass of leptoquark along with its electric charge. We perform a PYTHIA based simulation for reconstructing the leptoquark from its decay products of the first generation and estimating the background with luminosity of $$100\ \hbox {fb}^{-1}$$100fb-1. Our analysis is done for all the leptoquarks that can be seen at an e–$$\gamma$$γ collider with three different masses (70 GeV, 650 GeV and 1 TeV) and three different center of momentum energies (200 GeV, 2 TeV and 3 TeV). The effects of non-monochromatic photons on the zeros of the amplitude under laser backscattering and the equivalent photon approximation have also been addressed.</jats:p

Zeros of amplitude in the associated production of photon and leptoquark at \varvec{e}-\varvec{p} collider

AbstractThough various extensions of the Standard Model with higher gauge group predict the existence of leptoquarks, none of them has been observed yet at any of the colliders. In this paper, we study the prospect of several past and future $$e$$ e -$$p$$ p colliders like HERA, LHeC and FCC-he to detect them through radiation amplitude zero. We find that the leptoquarks showing zeros in the tree-level single-photon amplitudes at $$e$$ e -$$p$$ p collider lie within the complementary set of those exhibiting zeros at e-$$\gamma$$ γ collider. We present a PYTHIA-based analysis for HERA, LHeC and FCC-he (run II) to detect the leptoquarks with masses 70 GeV, 900 GeV and 1.5 TeV (2.0 TeV) respectively through radiation amplitude zero.</jats:p

Distinguishing Different BSM Signatures at Present and Future Colliders

We show how angular distributions can distinguish different scenarios beyond the standard model by characterising particles of different spins at the LHC. We illustrate the idea with scalar and vector leptoquarks along with the heavy fermions in Type-III seesaw as spin zero, spin one and spin half examples respectively. On the other hand, zeros of single photon tree level amplitude can separate different particles according their electromagnetic charges. This phenomenon can be used to distinguish leptoquarks of different gauge representations, even different excitations of same SU(2)Lgauge group, within the same spin frame work. We explore electron-photon and electron-hadron colliders to discern such scenarios in the context of the leptoquark models by means of zeros in scattering amplitudes. We found that the discerning effect in these two colliders are complementary to each other and both of them are required for an exhaustive analysis of leptoquark models. The analyses are carried out for different leptoquark masses and centre of mass energies of the collisions which involve a PYTHIA based simulation. © 2021 CERN. All rights reserved