Pablo Martín-Ramiro

Multiverse Computing (Spain)

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J. M. Moreno

Universidad Autónoma de Madrid

David Shih

Rutgers Sexual and Reproductive Health and Rights

Jack H. Collins

SLAC National Accelerator Laboratory

Benjamin Nachman

Lawrence Berkeley National Laboratory

Kees Benkendorfer

Harvard University Press

Anders Andreassen

Google (United States)

Charanjit K. Khosa

University of Sussex

M. Pierini

European Organization for Nuclear Research

O. Amram

Fermi National Accelerator Laboratory

Manuel Szewc

University of Cincinnati

Cooperative Institutions

A. Alikhanyan National Laboratory

Fermi National Accelerator Laboratory

University of Adelaide

European Organization for Nuclear Research

Institute of High Energy Physics

Massachusetts Institute of Technology

University of Antwerp

Lawrence Berkeley National Laboratory

University of Chicago

Atlas Scientific (United States)

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A template method to measure the $t \bar t$ polarization.

arXiv (Cornell University) (2021)

J. A. Aguilar–Saavedra M. C. N. Fiolhais Pablo Martín-Ramiro J. M. Moreno A. Onofre

We develop a template method for the measurement of the polarization of $t \bar t$ pairs produced in hadron collisions. The method would allow to extract the individual fractions of $t_L \bar t_L$, $t_R \bar t_R$, $t_L \bar t_R$ and $t_R \bar t_L$ pairs with a fit to data, where $L,R$ refer to the polarization along any axis. These polarization fractions have not been independently measured at present. Secondarily, the method also provides the net polarization of $t$ and $\bar t$, as well as their spin correlation for arbitrary axes.

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B anomalies and dark matter: a complex connection

The European Physical Journal C (2019)

D. G. Cerdeño Andrew Cheek Pablo Martín-Ramiro J. M. Moreno

We study an extension of the Standard Model that addresses the hints of lepton flavour universality violation observed in $B\to K^{(*)} l^+l^-$ decays at LHCb, while providing a viable candidate for dark matter. The model incorporates two new scalar fields and a Majorana fermion that induce one-loop contributions to $B$ meson decays. We show that agreement with observational data requires the new couplings to be complex and that the Majorana fermion can reproduce the observed dark matter relic density. This combination of cosmological and flavour constraints sets an upper limit on the dark matter and mediator masses. We have studied LHC dijet and dilepton searches, finding that they rule out large regions of parameter space by setting lower bounds on the dark matter and mediator masses. In particular, dilepton bounds are much more constraining in a future high-luminosity phase. Finally, we have computed the scattering cross section of dark matter off nuclei and compared it to the sensitivity of current and future direct detection experiments, showing that parts of the parameter space could be accessible in the future to multi-ton experiments. Future collider and direct DM searches complement each other to probe large areas of the parameter space of this model.

Majorana fermion

10.1140/epjc/s10052-019-6979-x

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Multi-disk Clutch Optimization Using Quantum Annealing

IEEE Transactions on Quantum Engineering (2024)

John D. Malcolm Alexander Roth Mladjan Radic Pablo Martín-Ramiro Jon Oillarburu

Quantum annealing

10.1109/tqe.2024.3441229

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Confronting the neutralino and chargino sector of the NMSSM with the multilepton searches at the LHC

Physical review. D/Physical review. D. (2020)

Florian Domingo Jong Soo Kim Víctor Martín Lozano Pablo Martín-Ramiro Roberto Ruiz de Austri

We test the impact of the ATLAS and CMS multilepton searches performed at the LHC with 8 as well as 13 TeV center-of-mass energy (using only the pre-2018 results) on the chargino and neutralino sector of the next-to-minimal supersymmetric Standard Model (NMSSM). Our purpose consists in analyzing the actual reach of these searches for a full model and in emphasizing effects beyond the minimal supersymmetric Standard Model (MSSM) that affect the performance of current (MSSM-inspired) electroweakino searches. To this end, we consider several scenarios characterizing specific features of the NMSSM electroweakino sector. We then perform a detailed collider study, generating Monte Carlo events through pythia and testing against current LHC constraints implemented in the public tool checkmate. We find e.g., that supersymmetric decay chains involving intermediate singlino or Higgs-singlet states can modify the naive MSSM-like picture of the constraints by inducing final states with softer or less easily identifiable SM particles---reversely, a compressed configuration with singlino next-to-lightest supersymmetric particle occasionally induces final states that are rich with photons, which could provide complementary search channels.

Chargino

Lightest Supersymmetric Particle

Higgs sector

10.1103/physrevd.101.075010

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Comparing weak- and unsupervised methods for resonant anomaly detection

The European Physical Journal C (2021)

Jack H. Collins Pablo Martín-Ramiro Benjamin Nachman David Shih

Anomaly detection techniques are growing in importance at the Large Hadron Collider (LHC), motivated by the increasing need to search for new physics in a model-agnostic way. In this work, we provide a detailed comparative study between a well-studied unsupervised method called the autoencoder (AE) and a weakly-supervised approach based on the Classification Without Labels (CWoLa) technique. We examine the ability of the two methods to identify a new physics signal at different cross sections in a fully hadronic resonance search. By construction, the AE classification performance is independent of the amount of injected signal. In contrast, the CWoLa performance improves with increasing signal abundance. When integrating these approaches with a complete background estimate, we find that the two methods have complementary sensitivity. In particular, CWoLa is effective at finding diverse and moderately rare signals while the AE can provide sensitivity to very rare signals, but only with certain topologies. We therefore demonstrate that both techniques are complementary and can be used together for anomaly detection at the LHC.

Anomaly (physics)

10.1140/epjc/s10052-021-09389-x

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Citations (49)

Improving $t \bar{t}$ reconstruction in the dilepton channel at future lepton colliders

arXiv (Cornell University) (2020)

Pablo Martín-Ramiro J. M. Moreno

A future lepton collider, such as the proposed CLIC or ILC, would allow to study top quark properties with unprecedented precision. In this paper, we present a method to reconstruct the $t \bar{t}$ decay in the dilepton channel at future $e^+e^-$ colliders. We derive a simple, closed analytical expression for the neutrino four-momenta as a function of the $W$ boson mass and develop a maximization procedure to find the optimal solution for the reconstruction of the full $t \bar{t}$ event. We show that our method is able to reconstruct neutrino four-momenta with an error of less than $2 \, \%$ in $60 \, \%$ of the times. Finally, we test the performance of this reconstruction method in the calculation of the helicity fractions of the $W$ boson. A precise measurement of these observables could be used to probe new physics effects in the $Wtb$ vertex. We find that, from a large $t \bar{t}$ sample, our reconstruction method allows to calculate these observables with an accuracy better than $1 \, \%$.

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10.48550/arxiv.2003.12320

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The LHC Olympics 2020 a community challenge for anomaly detection in high energy physics

Reports on Progress in Physics (2021)

Gregor Kasieczka Benjamin Nachman David Shih O. Amram Anders Andreassen

A new paradigm for data-driven, model-agnostic new physics searches at colliders is emerging, and aims to leverage recent breakthroughs in anomaly detection and machine learning. In order to develop and benchmark new anomaly detection methods within this framework, it is essential to have standard datasets. To this end, we have created the LHC Olympics 2020, a community challenge accompanied by a set of simulated collider events. Participants in these Olympics have developed their methods using an R&D dataset and then tested them on black boxes: datasets with an unknown anomaly (or not). This paper will review the LHC Olympics 2020 challenge, including an overview of the competition, a description of methods deployed in the competition, lessons learned from the experience, and implications for data analyses with future datasets as well as future colliders.

Leverage (statistics)

Benchmark (surveying)

Anomaly (physics)

10.1088/1361-6633/ac36b9

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Citations (133)

The LHC Olympics 2020: A Community Challenge for Anomaly Detection in High Energy Physics

arXiv (Cornell University) (2021)

Gregor Kasieczka Benjamin Nachman David Shih O. Amram Anders Andreassen

Leverage (statistics)

Benchmark (surveying)

Anomaly (physics)

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Citations (34)

Snowmass 2021 Computational Frontier CompF03 Topical Group Report: Machine Learning

HAL (Le Centre pour la Communication Scientifique Directe) (2022)

Phiala E. Shanahan K. Terao Daniel Whiteson Gert Aarts Andreas Adelmann

Frontier

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A template method to measure the $$t {\bar{t}}$$ polarisation

The European Physical Journal C (2022)

J. A. Aguilar–Saavedra M. C. N. Fiolhais Pablo Martín-Ramiro J. M. Moreno A. Onofre

Abstract We develop a template method for the measurement of the polarisation of $$t {\bar{t}}$$ t t ¯ pairs produced in hadron collisions. The method would allow to extract the individual fractions of $$t_L \bar{t}_L$$ t L t ¯ L , $$t_R {\bar{t}}_R$$ t R t ¯ R , $$t_L {\bar{t}}_R$$ t L t ¯ R and $$t_R {\bar{t}}_L$$ t R t ¯ L pairs with a fit to data, where L , R refer to the polarisation along any axis. These polarisation fractions have not been independently measured at present. Secondarily, the method also provides the net polarisation of t and $${\bar{t}}$$ t ¯ , as well as their spin correlation for arbitrary axes.

10.1140/epjc/s10052-022-10063-z

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Citations (6)