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PIONEER is a rapidly developing effort aimed to perform a pristine test of lepton flavour universality (LFU) and of the unitarity of the first row of the CKM matrix by significantly improving the measurements of rare decays of the charged pion. In Phase I, PIONEER aims to measure the charged-pion branching ratio to electrons vs.\\ muons \\(R_{e/\\mu}\\) to 1 part in \\(10^4\\), improving the current experimental result \\(R_{e/\\mu}\\,\\text{(exp)} =1.2327(23)\\times10^{-4}\\) by a factor of 15. This precision on \\(R_{e/\\mu}\\) will match the theoretical accuracy of the SM prediction allowing for a test of LFU at an unprecedented level, probing non-SM explanations of LFU violation through sensitivity to quantum effects of new particles up to the PeV mass scale. Phase II and III will aim to improve the experimental precision of the branching ratio of pion beta decay, \\(\\pi^+\\to \\pi^0 e^+ \\nu (\\gamma)\\), currently at \\(1.036(6)\\times10^{-8}\\), by a factor of three and six, respectively. The improved measurements will be used to extract \\(V_{ud}\\) in a theoretically pristine manner. The ultimate precision of \\(V_{ud}\\) is expected to reach the 0.05\\,\\% level, allowing for a stringent test of CKM unitarity. The PIONEER experiment will also improve the experimental limits by an order of magnitude or more on a host of exotic decays that probe the effects of heavy neutrinos and dark sector physics. This input to the 2026 update of the European Strategy for Particle Physics Strategy describes the physics motivation and the conceptual design of the PIONEER experiment, and is prepared based on the PIONEER proposal submitted to and approved with high priority by the PSI program advisory committee (PAC). Using intense pion beams, and state-of-the-art instrumentation and computational resources, the PIONEER experiment is aiming to begin data taking by the end of this decade.

In this white paper for the 2021 Snowmass process, we give a description of the proposed Future Circular Collider (FCC) project and its physics program. The paper summarizes and updates the discussion submitted to the European Strategy on Particle Physics. After construction of an approximately 90 km tunnel, an electron-positron collider based on established technologies allows world-record instantaneous luminosities at center-of-mass energies from the Z resonance up to tt thresholds, enabling a rich set of fundamental measurements including Higgs couplings determinations at the sub percent level, precision tests of the weak and strong forces, and searches for new particles, including dark matter, both directly and via virtual corrections or mixing. Among other possibilities, the FCC-ee will be able to (i) indirectly discover new particles coupling to the Higgs and/or electroweak bosons up to scales around 7 and 50 TeV, respectively; (ii) perform competitive SUSY tests at the loop level in regions not accessible at the LHC; (iii) study heavy-flavor and tau physics in ultra-rare decays beyond the LHC reach, and (iv) achieve the best potential in direct collider searches for dark matter, sterile neutrinos, and axion-like particles with masses up to around 90 GeV. The tunnel can then be reused for a proton-proton collider, establishing record center-of-mass collision energy, allowing unprecedented reach for direct searches for new particles up to the around 50 TeV scale, and a diverse program of measurements of the Standard Model and Higgs boson, including a precision measurement of the Higgs self-coupling, and conclusively testing weakly-interacting massive particle scenarios of thermal relic dark matter.

The Compact Linear Collider (CLIC) is a mature option for the future of high energy physics. It combines the benefits of the clean environment of \\(e^+e^-\\) colliders with operation at high centre-of-mass energies, allowing to probe scales beyond the reach of the Large Hadron Collider (LHC) for many scenarios of new physics. This places the CLIC project at a privileged spot in between the precision and energy frontiers, with capabilities that will significantly extend knowledge on both fronts at the end of the LHC era. In this report we review and revisit the potential of CLIC to search, directly and indirectly, for physics beyond the Standard Model.

The physics motivation and the conceptual design of the PIONEER experiment, a next-generation rare pion decay experiment testing lepton flavor universality and CKM unitarity, are described. Phase I of the PIONEER experiment, which was proposed and approved at Paul Scherrer Institut, aims at measuring the charged-pion branching ratio to electrons vs.\\ muons, \\(R_{e/\\mu}\\), 15 times more precisely than the current experimental result, reaching the precision of the Standard Model (SM) prediction at 1 part in \\(10^4\\). Considering several inconsistencies between the SM predictions and data pointing towards the potential violation of lepton flavor universality, the PIONEER experiment will probe non-SM explanations of these anomalies through sensitivity to quantum effects of new particles up to the PeV mass scale. The later phases of the PIONEER experiment aim at improving the experimental precision of the branching ratio of pion beta decay (BRPB), \\(\\pi^+\\to \\pi^0 e^+ \\nu (\\gamma)\\), currently at \\(1.036(6)\\times10^{-8}\\), by a factor of three (Phase II) and an order of magnitude (Phase III). Such precise measurements of BRPB will allow for tests of CKM unitarity in light of the Cabibbo Angle Anomaly and the theoretically cleanest extraction of \\(|V_{ud}|\\) at the 0.02\\% level, comparable to the deduction from superallowed beta decays.

A next-generation rare pion decay experiment, PIONEER, is strongly motivated by several inconsistencies between Standard Model (SM) predictions and data pointing towards the potential violation of lepton flavor universality. It will probe non-SM explanations of these anomalies through sensitivity to quantum effects of new particles even if their masses are at very high scales. Measurement of the charged-pion branching ratio to electrons vs. muons \\(R_{e/\\mu}\\) is extremely sensitive to new physics effects. At present, the SM prediction for \\(R_{e/\\mu}\\) is known to 1 part in \\(10^4\\), which is 15 times more precise than the current experimental result. An experiment reaching the theoretical accuracy will test lepton flavor universality at an unprecedented level, probing mass scales up to the PeV range. Measurement of pion beta decay, \\(\\pi^+\\to \\pi^0 e^+ \\nu (\\gamma)\\), with 3 to 10-fold improvement in sensitivity, will determine \\(V_{ud}\\) in a theoretically pristine manner and test CKM unitarity, which is very important in light of the recently emerged tensions. In addition, various exotic rare decays involving sterile neutrinos and axions will be searched for with unprecedented sensitivity. The experiment design benefits from experience with the recent PIENU and PEN experiments at TRIUMF and the Paul Scherrer Institut (PSI). Excellent energy and time resolutions, greatly increased calorimeter depth, high-speed detector and electronics response, large solid angle coverage, and complete event reconstruction are all critical aspects of the approach. The PIONEER experiment design includes a 3\\(\\pi\\) sr 25 radiation length calorimeter, a segmented low gain avalanche detector stopping target, a positron tracker, and other detectors. Using intense pion beams, and state-of-the-art instrumentation and computational resources, the experiments can be performed at the PSI ring cyclotron.

We analyze the low energy implications of a flavor blind supersymmetric scenario (where the CKM matrix is the only source of flavor violation) in the presence of new CP violating but flavor conserving phases in the soft sector. We find that the best probes of this rather restricted scenario are i) the electric dipole moments (EDMs) of the electron (d_e) and the neutron (d_n) and ii) flavor changing and CP violating processes in B systems, like the CP asymmetries in b->s gamma and B->phi(eta^')K_S, i.e. A_CP(b->s gamma) and S_phi(eta^')K_S, respectively. The non-standard values for S_phi(eta^')K_S, measured at the B factories, can find a natural explanation within our scenario and this would unambiguously imply i) positive and often large (non-standard) values for A_CP(b->s gamma) and ii) a lower bound for the electron and neutron EDMs at the level of d_e,n > 10^-28 e cm. Moreover, we predict positive New Physics (NP) contributions to epsilon_K which could be welcomed in view of the recently lowered Standard Model value for epsilon_K. Interestingly, an explanation for the non-standard values for S_phi(eta^')K_S can also naturally lead to an explanation for the anomaly of the muon anomalous magnetic moment. Finally, we outline the role and the interplay of the direct NP searches at the LHC with the indirect searches performed by low energy flavor physics observables.

We perform an extensive study of FCNC and CP Violation within Supersymmetric (SUSY) theories with particular emphasis put on processes governed by b->s transitions and of their correlations with processes governed by b->d transitions, s->d transitions, \\(D^0-\\bar D^0\\) oscillations, lepton flavour violating decays, electric dipole moments and (g-2)_mu. We first perform a comprehensive model-independent analysis of Delta F=2 observables and we emphasize the usefulness of the R_b-gamma plane in exhibiting transparently various tensions in the present UT analyses. Secondly, we consider a number of SUSY models: the general MSSM, a flavour blind MSSM, the MSSM with Minimal Flavour Violation as well as SUSY flavour models based on abelian and non-abelian flavour symmetries that show representative flavour structures in the soft SUSY breaking terms. We show how the characteristic patterns of correlations among the considered flavour observables allow to distinguish between these different SUSY scenarios. Of particular importance are the correlations between the CP asymmetry S_psi phi and B_s->mu^+\\mu^-, between the anomalies in S_phi K_S and S_psi phi, between S_phi K_S and d_e, between S_psi phi and (g-2)_mu and also those involving lepton flavour violating decays. In our analysis, the presence of right-handed currents and of the double Higgs penguin contributions to B_s mixing plays a very important role. We propose a \"DNA-Flavour Test\" of NP models including Supersymmetry, the Littlest Higgs model with T-parity and the Randall-Sundrum model with custodial protection, with the aim of showing a tool to distinguish between these NP scenarios, once additional data on flavour changing processes become available.

This report represents the response of the Intensity Frontier Quark Flavor Physics Working Group to the Snowmass charge. We summarize the current status of quark flavor physics and identify many exciting future opportunities for studying the properties of strange, charm, and bottom quarks. The ability of these studies to reveal the effects of new physics at high mass scales make them an essential ingredient in a well-balanced experimental particle physics program.

Objective This study aimed to assess patients’ preferences regarding the content and features of a digital patient navigator app. A secondary objective was to explore how patient characteristics influence the perceived importance and anticipated frequency of use of different app components. Methods The study was a monocentric cross-sectional survey conducted at the University Hospital Erlangen. A questionnaire consisting of 20 questions was designed to inquire about patients’ preferences for a digital patient navigator. Participants had breast diseases. Descriptive analyses were conducted to identify key app features and their correlation with patient characteristics. Results Questionnaires from 243 patients were analyzed. Preferred key app features, in order of preference from highest to lowest, were as follows: a communication feature to chat with treating physicians, a personalized treatment plan, real-time notifications, mediation services for providing support, 3D navigation within the hospital, and personal documents. Patients’ age, native language, and education significantly influenced the assessment of importance and frequency of use of some app features. A personalized treatment plan was considered more important by younger individuals (≤60 years, p < 0.001), whereas real-time notifications were considered more important by participants with a lower educational level (p = 0.003) and younger individuals (p = 0.036). Increased frequency of use of a personalized treatment plan tool was also associated with younger age (p < 0.001) and lower education levels (p = 0.025). Conclusion These findings suggest that a patient navigator app could be a valuable tool for a broad range of patients, potentially complementing in-person patient navigators. To ensure broad usability and acceptance, future development should account for varying needs across patient subgroups—particularly in terms of personalization, language accessibility, and communication features.

Objective Mobile Health apps could be a feasible and effective tool to raise awareness for breast cancer prevention and to support women to change their behaviour to a healthier lifestyle. The aim of this study was to analyse the characteristics and quality of apps designed for breast cancer prevention and education. Methods We conducted a systematic search for apps covering breast cancer prevention topics in the Google Play and Apple App Store accessible from Germany using search terms either in German or in English. Only apps with a last update after June 2020 were included. The apps identified were downloaded and evaluated by two independent researchers. App quality was analysed using the Mobile Application Rating Scale (MARS). Associations of app characteristics and MARS rating were analysed. Results We identified 19 apps available in the Google Play Store and seven apps available in the Apple App Store that met all inclusion criteria. The mean MARS score was 3.07 and 3.50, respectively. Functionality was the highest-scoring domain. Operating system, developer (healthcare), download rates and time since the last update were significantly associated with overall MARS score. In addition, the presence of the following app functions significantly influenced MARS rating: breast self-examination tutorial, reminder for self-examination, documentation feature and education about breast cancer risk factors. Conclusions Although most of the apps offer important features for breast cancer prevention, none of the analysed apps combined all functions. The absence of healthcare professionals’ expertise in developing apps negatively affects the overall quality.