abstract

The ATLAS experiment at the LHC has performed measurements of \(B\)‑meson rare decays proceeding via suppressed electroweak flavour changing neutral currents, and of mixing and CP violation in the neutral \(B_s\)‑meson system. The focus is on the latest results from the ATLAS Collaboration, such as rare processes \(B^0_s \rightarrow \mu \mu \) and \(B^0_d \rightarrow \mu \mu \), and CP violation in \(B_s \rightarrow J/\psi \phi \) decays. In the latter, the Standard Model predicts the CP violating mixing phase, \(\phi _{s}\), to be very small and its SM value is very well constrained, while in many new physics models, large \(\phi _{s}\) values are expected. The latest measurements of \(\phi _{s}\) and several other parameters describing the \(B^0_s \rightarrow \mu \mu \) decays will be reported.

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The PYTHIA program is a standard tool for the generation of events in high-energy collisions. It comprises a coherent set of physics models describing the evolution from a few-body hard process to a complex multi-particle final state including the multi-parton interaction. The model for soft interactions describing minimum-bias events is based on various parameters whose values are a priori unknown and thus need to be constrained by data. This study shows the impact of parameters on the multiplicity of events in proton–proton collisions at the center-of-mass energy 14 TeV and offers insights into which parameters could be optimized for Run 3.

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The hyperons are produced with a non-zero spin polarization that is straightforward to parameterize in processes involving virtual photons or vector mesons, allowing direct and precise CP violation tests. These CP tests can be performed on e.g. \(J/\psi \to {\mit \Lambda }\bar {\mit \Lambda }\), \(J/\psi \to {\mit \Xi }\bar {\mit \Xi }\), and \(J/\psi ,\psi '\to {\mit \Sigma }\bar {\mit \Sigma }\). For the \({\mit \Xi }\to {\mit \Lambda }\pi \) decay, the exclusive measurement of the final-state particles allows for three independent CP-symmetry tests and the determination of the strong and weak phase differences. Thanks to the large datasets in the tau-mass region, including the world’s largest data samples at the \(J/\psi \) and \(\psi '\) resonances collected at the BESIII experiment, the multi-dimensional analyses making use of polarization and entanglement have been performed for these processes.

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The Belle II Collaboration presents their first measurements of the magnitude of the Cabibbo–Kobayashi–Maskawa matrix elements \(|V_{cb}|\) and \(|V_{ub}|\), as well as their first branching fraction measurement of \(B\rightarrow K^*\ell ^+\ell ^-\) based on up to 189.3 fb\(^{-1}\) of data collected at the \({\mit \Upsilon }(4S)\) resonance. The magnitude \(|V_{cb}|\) was measured using \(B^0\rightarrow D^{*-}\ell ^+\nu _\ell \) by performing a fit to its \(w\) distribution. In particular, \(|V_{ub}|\) was obtained using a fit to the \(q^2\) distribution of \(B^+ \rightarrow \pi ^0e^+\nu _{e}\) and \(B^0 \rightarrow \pi ^-e^+\nu _{e}\). Finally, the results of an inclusive \(|V_{cb}|\) fit based on measurements of \(q^2\) moments are presented.

abstract

Recently, generative Machine Learning methods have gained a number of applications in physics analysis and detector science as they prove to be an excellent tool for data modeling. Generative Adversarial Networks (GANs), invented in 2014, were a breakthrough in computer vision and image synthesis, e.g. being able to generate realistic human faces. Although these networks show a growing presence in High-Energy Physics, their applications in this field are still quite scarce. The document investigates the potential use of GANs in Monte Carlo (MC) data generation in physics analysis, on the example of \(B^0\) → \(D_s ^-\) \(\pi ^+\) decay, simulated under the LHCb spectrometer geometry, and investigates whether they could be potentially used as an alternative method to the existing MC generators. Although GAN can quickly learn the shape of the distribution and recreate some correlations between physics parameters, its disadvantage is the lack of precision. The paper gives an overview of GAN capabilities as well as the optimized configuration of the model.

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The Standard Model (SM) description of CP violation can be tested by over-constraining the angles of the Unitary Triangle. Differences in measurements of the Cabibbo–Kobayashi–Maskawa angle \(\gamma \) performed with the tree-level and loop-dominated processes may be evidence for physics not covered by the Standard Model. Recent results of measurements of the CKM angle \(\gamma \), including one of the most precise determinations of the CKM angle \(\gamma \) in a single measurement obtained in studies of \(B^\pm \to D K^\pm \) with the \(D \to K^\mp \pi ^\pm \pi ^\pm \pi ^\mp \) decay and results of studies of \(B^\pm \to D h^\pm \) with the \(D \to h^\pm h^{'\mp }\pi ^0\) and \(B^\pm \to D[K^\mp \pi ^\pm \pi ^\pm \pi ^\mp ]h^\pm \) decays, are presented in these proceedings.

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The MUonE experiment is dedicated to the precise measurement of the hadronic contribution to the anomalous magnetic moment of the muon, \(a_{\mu }\), which may lead to the observation of a significant discrepancy with respect to the Standard Model predictions. It is planned to be operating at SPS and will allow for a precise determination of hadronic contribution to \(a_{\mu }\) employing the measurement of shape of differential cross section for the \(\mu e \rightarrow \mu e\) elastic process, reaching a competitive precision below 0.5% on the leading hadronic contribution, under the condition that systematic uncertainties are well controlled. The Test Run detector geometry with a reduced setup is being prepared, following a successful test beam in 2018, aimed mainly at checking the ability to select a clean sample of elastic scattering events in view of designing the final experiment.

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From the first principles, particles with the same quark content and similar masses should have similar kinematic distributions. Transverse mass scaling may be employed to estimate possible differences in the momentum distribution of such particles. Based on this scaling, the excited bottomonium states measured at the LHC are found to be significantly different from \({\mit \Upsilon }(1S)\) to the extent that the integrated yield of \({\mit \Upsilon }(2S)\) is 1.6 times less and \({\mit \Upsilon }(3S)\) 2.4 times less than would be explained by the mass difference. This contribution explains how the estimate is worked out and relates it to other measurements performed at the LHC.

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The second upgrade of the LHCb detector is planned for the long shutdown 4 of the LHC. In this upgrade, part of the existing spectrometer will be replaced and new tracking detectors allowing for time measurements will be installed. This upgrade will enable the exploitation of the physics potential of the high-luminosity LHC runs. The corresponding data sets will provide heavy-flavour results with unprecedented precision as well as significantly increase the sensitivity of BSM searches with displaced vertices. In this paper, the physics goals of Upgrade II will be reviewed, as well as the detector design and technology options which will allow for meeting the desired specifications.

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The NA62 experiment at CERN took data in 2016–2018 with the main goal of measuring the \(K^{+} \to \pi ^{+}\nu \bar {\nu }\) decay. The high-intensity fixed-target setup and the detector performance make the NA62 experiment particularly suited to make precision measurements of charged kaon decays. Preliminary results of the \(K^{\pm } \to \pi ^{0}\pi ^{0}\mu ^{\pm }\nu (K_{\mu 4}^{00})\) decay first observation and analysis based on NA48/2 data collected in 2003–2004 are presented. Results from studies of \(K^{+} \to \pi ^{0} e^{+}\nu \gamma (K_{e3}^{0})\) decays are reported, based on a data sample of more than \(10^{5}\) \(K_{e3}^{0}\) candidates recorded in 2017–2018. Preliminary results with the most precise measurements of the \(K_{e3}^{0}\) branching ratios and of T-asymmetry in the \(K_{e3}^{0}\) decay are presented. The flavour-changing neutral current decay \(K^{+} \to \pi ^{+}\mu ^{+}\mu ^{-}\) is induced at the one-loop level in the Standard Model. Preliminary results from an analysis of the \(K^{+}\to \pi ^{+}\mu ^{+}\mu ^{-}\) decay are reported, using a large sample of about \(3\times 10^{12}\) kaon decays into two muons recorded with a downscaled dimuon trigger operating along with the main trigger. The most precise determination of the \(K^{+} \to \pi ^{+}\mu ^{+}\mu ^{-}\) form-factor parameters \(a_{+}\) and \(b_{+}\) has been made by NA62 using data collected in 2017 and 2018.

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We report on recent measurements of hadronic \(B\) decays using data collected from 2019 to 2021 by the Belle II experiment and corresponding to an integrated luminosity of 189.8 fb\(^{-1}\). We present the measurement of the CKM angle \(\gamma \), performed by combining Belle II data with the full Belle data set, and measurements of \(B^0\) lifetime and \(B^0\)–\(\bar {B}^0\) mixing frequency, branching fractions, and CP-violating asymmetries of \(B^+ \to \rho ^+\rho ^0\) and \(B^0 \to K_{\mathrm {S}}^0\pi ^0\) decays.

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The LHCb experiment has collected the world’s largest sample of charmed hadrons during the LHC periods: Run 1 and Run 2. Based on these data, the LHCb experiment provides the world’s most precise measurements of properties, including searches for CP violation and branching ratios of the known charmed baryons, as well as discovering many unobserved states till now. The latest results from the LHCb Collaboration on charmed baryons are reviewed in this manuscript, focusing on searches for CP violation.

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A promising tool to probe charge-conjugation and parity violation (CPV) consists in the non-leptonic two-body weak decays of the hyperons. We explore their prominent characteristics and possible statistical improvements within the hyperon production framework of electron–positron \(J/\psi \) factories, Super Charm-Tau (SCTF). Such a production mechanism allows for an analysis and comparison of baryons to their antimatter counterpart, being produced in a spin-entangled state. We outline the weight of such a spin correlation within the \(B\bar {B}\) pair and explore the impact of polarizing the electron beam on CPV observables measurements. With our data-based projections, we conclude that more detailed feasibility studies can provide a deeper insight into the CPV mechanism in hyperons and should prompt an update of the theoretical predictions.

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By dedicated off-resonance energy scans, the BESIII experiment provides unique information on the time-like structure of strange and single-charm hyperons. In particular, exploiting polarised and entangled hyperon–antihyperon pairs, has enabled the first complete measurement of the time-like structure of a baryon at a single energy. From this, we gain new insights into the strong interaction forming visible matter.

abstract

In 1993, a new Hyperon Beta Decay study was introduced into the KTeV experiment and although it would have only collected less than 1000 events, it was to become a major important step in particle physics, because it showed that the CKM matrix obeyed unitarity. This new idea was introduced by myself while a new PostDoc just starting my career after getting a Ph.D. The 98% analyzing power of these decays allowed us to study beta decay form factors and showed that the CKM matrix element \(V_{us}\) historically used for 35 years was wrong and that this correction changed \(V_{us}\) by 6 sigma bringing a new understanding to quark flavor physics. Today the CKM matrix is a guide for a similar matrix in the neutrino matrix and continues to have an important impact on particle quark flavor searches for new physics.

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In the era of precision flavour physics in the quark sector, an ongoing discussion around the origin of direct CP violation in charmed mesons started earlier in the century, but only in 2019 was direct CP violation discovered with a \(5\sigma \) significance for the first time, reheating the debate. The controversy stems mainly from the difficulty in calculating hadronic effects in the relevant energy regime. In this work, we provide a Standard Model calculation addressing the decays of neutral charm mesons to two pions or two kaons, and give predictions for the amount of CP violation present in such decays.

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Nowadays, simulated data are commonly used in modern high-energy physics experiments. They are essential not only in determining certain performances but also in training machine learning algorithms. However, in some cases, such as rare heavy meson decays, generating data requires enormous computational resources. To speed up this process significantly, we propose a new method — to replicate simulated data using existing samples. Preliminary results of the algorithm are presented.

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The large amount of heavy flavour data collected by the ATLAS experiment at the LHC allows the analysis of rare processes potentially sensitive to New Physics, which could be evident in processes that are naturally suppressed in the Standard Model. The results of the analysis of the angular distribution parameters describing the \(B_{d}^{0} \to K^{\star 0}\mu ^{+}\mu ^{-} \to K^{+}\pi ^{-}\mu ^{+}\mu ^{-}\) decay based on full Run 1 data are presented. They are consistent with the Standard Model predictions.

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The LHCb experiment collected the world’s largest data samples with charmed hadrons during the first two runs of the LHC operations. These samples allow us to measure CP-violating observables in \(D\)-meson decays with precision not available till now. New measurements of CP violation in different charged and neutral-charm decays based on these data sets are reported.

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This contribution summarizes a selection of recent results from the ALICE experiment. We show the cross section of beauty jets in \(pp\) collisions, as well as the charmed baryon-to-meson production ratios, down to unprecedentedly low momenta at \(\sqrt {s_{NN}} = 5.02\) and 13 TeV collision energies. We present the nuclear modification of \(D^0\) jets and the \(v_2\) of non-prompt \(D^0\) in Pb–Pb collisions at \(\sqrt {s_{NN}} = 5.02\) TeV. We also discuss the implications and constraints from comparing these data to some of the most recent theoretical models.

abstract

Recent results from the LHC proton–proton collision data taken by the ATLAS experiment on exotic resonances are presented. A search for \(J/\psi p\) resonances which are potential pentaquarks in the \({\mit \Lambda }_{b}\rightarrow J/\psi p K\) decays with large \(p K\)-invariant masses is reported.