Some of the issues that make sampling parameter spaces of various beyond the Standard Model (BSM) scenarios computationally expensive are the high dimensionality of the input parameter space, complex likelihoods, and stringent experimental constraints. In this work, we explore likelihood-free approaches, leveraging neural network-aided Simulation-Based Inference (SBI) to alleviate this issue. We focus on three amortized SBI methods: Neural Posterior Estimation (NPE), Neural Likelihood Estimation (NLE), and Neural Ratio Estimation (NRE) and perform a comparative analysis through the validation test known as the $\textit{Test of Accuracy with Random Points}$ (TARP), as well as through posterior sample efficiency and computational time. As an example, we focus on the scalar sector of the phenomenological minimal supersymmetric SM (pMSSM) and observe that the NPE method outperforms the others and generates correct posterior distributions of the parameters with a minimal number of samples. The efficacy of this framework is tested on 5 parameter pMSSM with Higgs and flavor physics data and its performance is compared with the MCMC method. We further add dark matter (DM) observables to make the task more challenging and consider a 9 parameter pMSSM. We observe that even though the efficiency factor drops, the amortized SBI method still produces faithful posterior distributions. SBI predicted points satisfying DM constraints are mostly bino-dominated upto ~ 1.5 TeV, and are mostly wino-dominated within the 1.5–2 TeV range.

Netherlands

India

Atrideb Chatterjee

Arghya Choudhury

Sourav Mitra

Arpita Mondal

Subhadeep Mondal

Exploring the BSM parameter space with neural network aided Simulation-Based Inference

We propose a novel technique for sampling particle physics model parameter space. The main sampling method applied is nested sampling (NS), which is boosted by the application of multiple machine learning (ML) networks, e.g., self-normalizing network (SNN) and Normalizing Flow (specifically RealNVP). We apply this to the Type-II Seesaw model to test the algorithm’s efficacy. We present the results of our detailed Bayesian exploration of the model parameter space subjected to theoretical constraints and experimental data corresponding to the 125 GeV Higgs boson, $$\rho $$ -parameter, and the oblique parameters. All associated data, figures, and trained ML models can be found here:GitHub

Rajneil Baruah

Sunando Patra

Satyajit Roy

Normalizing flow-assisted nested sampling on Type-II Seesaw model

<p>In this article, we probe the trilinear <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>R</mi></math>-parity violating (RPV) supersymmetric (SUSY) scenarios with specific nonzero interactions in the light of neutrino oscillation, Higgs, and flavor observables. We attempt to fit the set of observables using a state-of-the-art Markov Chain Monte Carlo (MCMC) setup and study its impact on the model parameter space. Our main objective is to constrain the trilinear couplings individually, along with some other SUSY parameters relevant to the observables. We present the constrained parameter regions in the form of marginalized posterior distributions on different two-dimensional parameter planes. We perform our analyses with two different scenarios characterized by our choices for the lightest SUSY particle (LSP), bino, and stop. Our results indicate that the lepton number violating trilinear couplings <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>λ</mi><mrow><mi>i</mi><mn>33</mn></mrow></msub></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>i</mi><mo>=</mo><mn>1</mn></math>, 2) and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>λ</mi><mrow><mi>j</mi><mn>33</mn></mrow><mo>′</mo></msubsup></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>j</mi><mo>=</mo><mn>1</mn></math>, 2, 3) can be at most of the order of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>4</mn></mrow></msup></math> or even smaller while <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>tan</mi><mi>β</mi></math> is restricted to below 15 even when <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3</mn><mi>σ</mi></math> allowed regions are considered. We further comment on the possible LHC signatures of these LSPs focusing on and around the best-fit regions.</p>

Markov chain Monte Carlo analysis to probe trilinear <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>R</mi></math>-parity violating SUSY scenarios and possible LHC signatures

<p>Probing Higgsinos remains a challenge at the LHC owing to their small production cross sections and the complexity of the decay modes of the nearly mass degenerate Higgsino states. The existing limits on Higgsino mass are much weaker compared to its bino and wino counterparts. This leaves a large chunk of sub-TeV supersymmetric parameter space unexplored so far. In this work, we explore the possibility of probing Higgsino masses in the 400–1000 GeV range. We consider a simplified supersymmetric scenario where <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>R</mi></math>-parity is violated through a baryon number violating trilinear coupling. We adopt a machine-learning-based top tagger to tag the boosted top jets originating from Higgsinos, and for our collider analysis, we use a boosted decision tree classifier to discriminate signal over SM backgrounds. We construct two signal regions characterized by at least one top jet and different multiplicities of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi></math>-jets and light jets. Combining the statistical significance obtained from the two signal regions, we show that Higgsino mass as high as 925 GeV can be probed at the HL-LHC.</p>

Kirtiman Ghosh

Rameswar Sahu

Probing sub-TeV Higgsinos aided by a machine-learning-based top tagger in the context of trilinear <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>R</mi></math>-parity violating SUSY

In the so-called 331-models the gauge anomalies cancel only if there are three generations of fermions. This requires one of the quark generations to be in a different representation than the other two. But which generation is treated differently? In this work we study how the choice of differently treated generation effects the quark flavour structure and how the discriminated generation can be deduced from experiments. We study a general model based on $$ \beta =-1/\sqrt{3} $$ , which contains exotic quarks with same electric charges as SM quarks. We take fully into account the effects from exotic quark mixing with the SM quarks, which is often omitted in literature. We will also pay particular attention to 125 GeV Higgs, and show analytically why its flavour violating couplings between SM quarks are suppressed.

Finland

Katri Huitu

Estonia

Niko Koivunen

Timo Kärkkäinen

On the family discrimination in 331-model

In this work, we have explored the sensitivity of multilepton final states in probing the gaugino sector of a R-parity violating supersymmetric scenario with specific lepton number violating trilinear couplings (<math><msub><mi>λ</mi><mrow><mi>i</mi><mi>j</mi><mi>k</mi></mrow></msub></math>) being nonzero. The gaugino spectrum is such that the charged leptons in the final state can arise from the R-parity violating decays of the lightest supersymmetric particle (LSP) as well as R-parity conserving decays of the next-to-LSP (NLSP). Apart from a detailed cut-based analysis, we have also performed a machine learning-based analysis using a boosted decision tree algorithm, which provides much better sensitivity. In the scenarios with nonzero <math><msub><mi>λ</mi><mn>121</mn></msub></math> and/or <math><mrow><msub><mrow><mi>λ</mi></mrow><mrow><mn>122</mn></mrow></msub></mrow></math> couplings, the LSP pair in the final states decays to <math><mrow><mn>4</mn><mi>l</mi></mrow></math> <math><mrow><mo>(</mo><mi>l</mi><mo>=</mo><mi>e</mi><mo>,</mo><mi>μ</mi><mo>)</mo><mo>+</mo><msub><mrow><mrow><mi>E</mi></mrow></mrow><mrow><mi>T</mi></mrow></msub></mrow></math> final states with a 100% branching ratio. We have shown that under this circumstance, a final state with <math><mo>≥</mo><mn>4</mn><mi>l</mi></math> has the highest sensitivity while probing for gaugino masses. We also discuss how the sensitivity can change in the presence of <math><mi>τ</mi></math> lepton(s) in the final state due to other choices of trilinear couplings. We present our results through the estimation of the discovery and exclusion contours in the gaugino mass plane for both the high luminosity LHC (HL-LHC with <math><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>14</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> and <math><mrow><mi>L</mi><mo>=</mo><mn>3000</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>fb</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math>) and high energy LHC (HE-LHC with <math><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>27</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> and <math><mrow><mi>L</mi><mo>=</mo><mn>3000</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>fb</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math>). For the <math><msub><mi>λ</mi><mn>121</mn></msub></math> and/or <math><msub><mi>λ</mi><mn>122</mn></msub></math> nonzero scenario, the projected <math><mrow><mn>2</mn><mi>σ</mi></mrow></math> exclusion limit on NLSP masses reaches upto 2.37 TeV and 4 TeV for the HL-LHC and the HE-LHC, respectively, by using a machine learning based algorithm. We observe an enhancement of <math><mrow><mo>∼</mo><mn>380</mn><mtext> </mtext><mo>(</mo><mn>190</mn><mo>)</mo><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math> in the projected <math><mrow><mn>2</mn><mi>σ</mi></mrow></math> exclusion limit on the NLSP masses at the 27 (14) TeV LHC. Considering the same final state (<math><msub><mi>N</mi><mi>l</mi></msub><mo>≥</mo><mn>4</mn></math>) for the <math><msub><mi>λ</mi><mn>133</mn></msub></math> and/or <math><msub><mi>λ</mi><mn>233</mn></msub></math> nonzero scenario, we find that the corresponding <math><mrow><mn>2</mn><mi>σ</mi></mrow></math> projected limits are <math><mo>∼</mo><mn>1.97</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> and <math><mo>∼</mo><mn>3.25</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> for the HL-LHC and HE-LHC, respectively.

Subhadeep Sarkar

Improving sensitivity of trilinear R-parity violating SUSY searches using machine learning at the LHC

In this work, we explore a well motivated beyond the Standard Model scenario, namely, R-parity violating Supersymmetry, in the context of light neutrino masses and mixing. We assume that the R-parity is only broken by the lepton number violating bilinear term. We try to fit two non-zero neutrino mass square differences and three mixing angle values obtained from the global χ 2 analysis of neutrino oscillation data. We have also taken into account the updated data of the standard model (SM) Higgs mass and its coupling strengths with other SM particles from LHC Run-II along with low energy flavor violating constraints like rare b-hadron decays. We have used a Markov Chain Monte Carlo (MCMC) analysis to constrain the new physics parameter space. While doing so, we ensure that all the existing collider constraints are duly taken into account. Through our analysis, we have derived the most stringent constraints possible to date with existing data on the 9 bilinear R-parity violating parameters along with μ and tan β. We further explore the possibility of explaining the anomalous muon (g - 2) measurement staying within the parameter space allowed by neutrino, Higgs and flavor data while satisfying the collider constraints as well. We find that there still remains a small sub-TeV parameter space where the required excess can be obtained.

Bilinear R-parity violating supersymmetry under the light of neutrino oscillation, Higgs and flavor data

The recently proposed multiphase criticality principle in Coleman-Weinberg models can provide a new explanation for the hierarchy between the electroweak and new physics scales. When applied to the Standard Model, a Higgs boson as light as the pseudo-Goldstone boson of broken-scale invariance occurs. The suppressed mixing between the two light fields still carries information about the large scale of symmetry breaking, albeit up to logarithmic corrections. In this work we probe this scenario with the present LHC data and assess the impact of future lepton and hadron colliders. Our results show that the multiphase criticality can easily explain the apparent absence of new physics at the energy scales tested in current experiments.

Kristjan Kannike

Luca Marzola

Martti Raidal

Multiphase critical Higgs boson at colliders

We attribute deviations of the muon and electron magnetic moments from the theoretical predictions to the presence of an additional U(1)′ supersymmetric model. We interpret the discrepancies between the muon and electron anomalous magnetic moments to be due to the presence of non-universal U(1)′ charges. In a minimally extended model, we show that requiring both deviations to be satisfied imposes constraints on the spectrum of the model, in particular on dark matter candidates and slepton masses and ordering. Choosing three benchmarks with distinct dark matter features, we study implications of the model at colliders, concentrating on variables that can distinguish our non-universal scenario from other U(1)′ implementations.

Canada

Mariana Frank

United Kingdom

Türkiye

Yaşar Hiçyılmaz

Özer Özdal

Cem Ün

Electron and muon magnetic moments and implications for dark matter and model characterisation in non-universal U(1)′ supersymmetric models

We consider dark sectors with spontaneously broken gauge symmetries, where cascade decays of the dark sector fields naturally produce multi-Higgs boson final states along with dark matter. Our study focuses on two and three Higgs boson final states with missing energy using a multivariate analysis with boosted decision trees. We find that the di-Higgs boson channel is quite promising for the <math><mover><mi>b</mi><mo>¯</mo></mover><mi>b</mi><mo>+</mo><mi>γ</mi><mi>γ</mi></math> and <math><mover><mi>b</mi><mo>¯</mo></mover><mi>b</mi><mo>+</mo><mover><mo>ℓ</mo><mo>¯</mo></mover><mo>ℓ</mo></math> decay modes. The tri-Higgs boson final state with missing energy, on the other hand, appears to be beyond the reach of the LHC in analogous channels. This may change when fully hadronic Higgs boson decays are considered.