Training Deep 3D Convolutional Neural Networks to Extract BSM Physics Parameters Directly from HEP Data: a Proof-of-Concept Study Using Monte Carlo Simulations

We report on a novel application of computer vision techniques to extract beyond the Standard Model (BSM) parameters directly from high energy physics (HEP) flavor data. We develop a method of transforming angular and kinematic distributions into "quasi-images" that can be used to train a convolutional neural network to perform regression tasks, similar to fitting. This contrasts with the usual classification functions performed using ML/AI in HEP. As a proof-of-concept, we train a 34-layer Residual Neural Network to regress on these images and determine the Wilson Coefficient $C_{9}$ in MC (Monte Carlo) simulations of $B \rightarrow K^{*}\mu^{+}\mu^{-}$ decays. The technique described here can be generalized and may find applicability across various HEP experiments and elsewhere

Machine Learning for New Physics Searches in B → K*0µ+µ− Decays

We report the status of a neural network regression model trained to extract new physics (NP) parameters in Monte Carlo (MC) simulation data. We utilize a new EvtGen NP MC generator to generate B → K*0µ+µ− events according to the deviation of the Wilson Coefficient C9 from its SM value, δC9. We train a three-dimensional ResNet regression model, using images built from the angular observables and the invariant mass of the di-muon system, to extract values of δ C9 directly from the MC data samples. This work is intended for future analyses at the Belle II experiment but may also find applicability at other experiments

Belle II Executive Summary

Belle II is a Super $B$ Factory experiment, expected to record 50 ab$^{-1}$ of $e^+e^-$ collisions at the SuperKEKB accelerator over the next decade. The large samples of $B$ mesons, charm hadrons, and tau leptons produced in the clean experimental environment of $e^+e^-$ collisions will provide the basis of a broad and unique flavor-physics program. Belle II will pursue physics beyond the Standard Model in many ways, for example: improving the precision of weak interaction parameters, particularly Cabibbo-Kobayashi-Maskawa (CKM) matrix elements and phases, and thus more rigorously test the CKM paradigm, measuring lepton-flavor-violating parameters, and performing unique searches for missing-mass dark matter events. Many key measurements will be made with world-leading precision.Comment: 7 pages, to be submitted to the "Rare and Precision Measurements Frontier" of the APS DPF Community Planning Exercise Snowmass 202

B-flavor tagging at Belle II

We report on new flavor tagging algorithms developed to determine the quark-flavor content of bottom ( ) mesons at Belle II. The algorithms provide essential inputs for measurements of quark-flavor mixing and charge-parity violation. We validate and evaluate the performance of the algorithms using hadronic decays with flavor-specific final states reconstructed in a data set corresponding to an integrated luminosity of 62.8 fb−1 , collected at the resonance with the Belle II detector at the SuperKEKB collider. We measure the total effective tagging efficiency to be εeff=(30.0±1.2(stat)±0.4(syst))% for a category-based algorithm and εeff=(28.8±1.2(stat)±0.4(syst))% for a deep-learning-based algorithm

Search for a Light Higgs Boson in Single-Photon Decays of ϒ(1S) Using ϒ(2S)→π+^{+}π−^{-}ϒ(1S) Tagging Method

We search for a light Higgs boson (A$^{0}$) decaying into a τ$^{+}$τ$^{-}$ or μ$^{+}$μ$^{-}$ pair in the radiative decays of Υ(1S). The production of Υ(1S) mesons is tagged by Υ(2S)→π$^{+}$π$^{-}$Υ(1S) transitions, using 158×10$^{6}$ Υ(2S) events accumulated with the Belle detector at the KEKB asymmetric energy electron positron collider. No significant A$^{0}$ signals in the mass range from the τ$^{+}$τ$^{-}$ or μ$^{+}$μ$^{-}$ threshold to 9.2 GeV/c$^{2}$ are observed. We set the upper limits at 90% credibility level (C.L.) on the product branching fractions for Υ(1S)→γA$^{0}$ and A$^{0}$→τ$^{+}$τ$^{-}$ varying from 3.8×10$^{-6}$ to 1.5×10$^{-4}$. Our results represent an approximately twofold improvement on the current world best upper limits for the Υ(1S)→γA$^{0}$(→τ$^{+}$τ$^{-}$) production. For A$^{0}$→μ$^{+}$μ$^{-}$, the upper limits on the product branching fractions for Υ(1S)→γA$^{0}$ and A$^{0}$→μ$^{+}$μ$^{-}$ are at the same level as the world average limits, and vary from 3.1×10$^{-7}$ to 1.6×10$^{-5}$. The upper limits at 90% credibility level on the Yukawa coupling fΥ(1S) and mixing angle sin θ$_{A0}$ are also given

Search for Axionlike Particles Produced in e⁺ e⁻ Collisions at Belle II

International audienceWe present a search for the direct production of a light pseudoscalar a decaying into two photons with the Belle II detector at the SuperKEKB collider. We search for the process e+e-→γa, a→γγ in the mass range 0.2

Search for Axionlike Particles Produced in e+e- Collisions at Belle II

We present a search for the direct production of a light pseudoscalar a decaying into two photons with the Belle II detector at the SuperKEKB collider. We search for the process e+e-→γa, a→γγ in the mass range 0.2<9.7 GeV/c2 using data corresponding to an integrated luminosity of (445±3) pb-1. Light pseudoscalars interacting predominantly with standard model gauge bosons (so-called axionlike particles or ALPs) are frequently postulated in extensions of the standard model. We find no evidence for ALPs and set 95% confidence level upper limits on the coupling strength gaγγ of ALPs to photons at the level of 10-3 GeV-1. The limits are the most restrictive to date for 0.2<1 GeV/c2

Measurement of branching fractions and direct CPCP asymmetries for B→KπB \to K\pi and B→ππB\to\pi\pi decays at Belle II

We report measurements of the branching fractions and direct $\it{CP}$ asymmetries of the decays $B^0 \to K^+ \pi^-$, $B^+ \to K^+ \pi^0$, $B^+ \to K^0 \pi^+$, and $B^0 \to K^0 \pi^0$, and use these for testing the standard model through an isospin-based sum rule. In addition, we measure the branching fraction and direct $\it{CP}$ asymmetry of the decay $B^+ \to \pi^+\pi^0$ and the branching fraction of the decay $B^0 \to \pi^+\pi^-$. The data are collected with the Belle II detector from $e^+e^-$ collisions at the $\Upsilon(4S)$ resonance produced by the SuperKEKB asymmetric-energy collider and contain $387\times 10^6$ bottom-antibottom meson pairs. Signal yields are determined in two-dimensional fits to background-discriminating variables, and range from 500 to 3900 decays, depending on the channel. We obtain $-0.03 \pm 0.13 \pm 0.04$ for the sum rule, in agreement with the standard model expectation of zero and with a precision comparable to the best existing determinations