arXiv subjects

Alexey A. Petrov

Publications and source records attributed to Alexey A. Petrov.

At least 19 recordsLinked to original sources

arXiv2026

Precision Physics with Muons : A Decade of Theoretical and Experimental Advances

The muon has been instrumental in establishing the Standard Model of particle physics and continues to play a key role in exploring the nature of New Physics. A global program is underway to enhance the discovery potential of a wide range of muon probes, with significant increases in sensitivity anticipated over the next decade. In this review, we examine recent experimental advancements in the study of muon decays, the determination of the muon magnetic and electric dipole moments, and the search for charged lepton flavor-violating transitions. We explore the implications for scenarios of physics beyond the Standard Model, focusing on models involving light new particles, such as axions and hidden sectors. Opportunities from novel experimental concepts and proposal for new muon facilities are also discussed.

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arXiv2026

New Avenues for $|ΔB|$ = 2 Processes Beyond Neutron-Antineutron Oscillations

We explore baryon-number-violating ($|ΔB| = 2$) processes beyond the well-known neutron-antineutron ($n - \bar{n}$) oscillations, focusing on the $Λ- \bar Λ$ system. The presence of a strange quark in the $Λ$ baryon introduces a new set of six-quark operators roughly of the form $(uds)^2$, which are different from the $(udd)^2$ operators responsible for $n - \bar{n}$ oscillations. Using the Standard Model Effective Field Theory (SMEFT), we classify all dimension-9 operators that cause $|ΔB|=2$ transitions and study their UV completions mediated by exotic scalar fields with trilinear interactions. We demonstrate that in these models, $Λ- \bar Λ$ oscillations can occur at tree level, with $n - \bar{n}$ mixing potentially appearing at higher loop levels. We employ a chiral effective theory to constrain the effective mass mixing $δm_Λ$, deriving bounds from current experimental limits on $n - \bar{n}$ oscillations and dinucleon decays such as $p \,p \to K^+ K^+$. These bounds indicate that $Λ- \barΛ$ oscillations probe a complementary parameter space, sensitive to baryon-number violation at scales up to $10^2-10^3$ TeV. We show that the existing indirect bounds make it challenging to provide a competitive bound on $δm_Λ$ at BESIII.

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arXiv2026

Axion-like Particles and Lepton Flavor Violation in Muonic Atoms

We explore the potential of the Mu2e experiment to probe the lepton-flavor-violating process $μ^- e^- \to e^- e^-$ in a muonic atom within a simplified axion-like particle (ALP) framework featuring flavor-violating $e$-$μ$ couplings and a flavor-diagonal pseudoscalar coupling to electrons, which also allows for possible invisible ALP decays into a dark sector. We compute the ALP-mediated contribution to the transition rate and show that, at fixed couplings, the branching ratio increases for lighter mediators and scales as $(Z-1)^3$, favoring heavier nuclei. We compare the model against constraints from $μ\to eγ$, $μ\to 3e$, $μ\to eγγ$, $μ\to e+\mathrm{inv}$, and muonium-antimuonium conversion, as well as from the anomalous magnetic moments of the electron and muon. Additional astrophysical and beam-dump limits on the electron coupling are also discussed. A key result is that $Δa_e$ provides one of the most stringent probes of the parameter space and, in the global scan, excludes the largest fraction of sampled points. After applying the laboratory constraints used in the scan, the viable branching ratio for $μ^- e^- \to e^- e^-$ in aluminum drops to at most $\mathcal{O}(10^{-20})$, while the resonant region $2m_e<m_a<m_μ-m_e$ is much more heavily suppressed. The highest achievable values are closely tied to $\mathcal{B}(μ\to 3e)$ near its current limit, indicating that the upcoming Mu3e experiment will explore the most promising region relevant for this muonic-atom signal. Our analysis shows that, although a light ALP can parametrically enhance $μ^- e^- \to e^- e^-$ at fixed couplings, existing bounds -- especially $Δa_e$, $μ\to 3e$, $μ\to eγ$, and muonium oscillations -- severely limit the observable rate.

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arXiv2026

The Physics and Prospects of Super-Tau Charm Factories

The proposed Super tau-charm factories are a powerful new class of high-luminosity electron-positron colliders operating in the center-of-mass energy range between 2 and 7 GeV, a region that spans thresholds for tau leptons, open-charm hadrons, charmonium and charmonium-like states, hyperons, and light hadrons. With unprecedented data samples, threshold kinematics, and quantum-coherent production, these facilities offer unique opportunities to advance precision tests of the Standard Model and to search for physics beyond it. In this review, we examine the physics prospects of the Super Tau-Charm Facility, focusing on precision charm measurements, CP violation in mesons and baryons, tau lepton properties and rare decays, and nonperturbative QCD phenomena such as hadronization, spectroscopy, and time-like form factors. We also discuss the experimental landscape, technological challenges, and complementarity with existing and planned facilities. Together, these capabilities position super tau-charm factories at the forefront of the precision frontier in particle physics.

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arXiv2025

Conceptual Design of the Muonium-to-Antimuonium Conversion Experiment (MACE)

The spontaneous conversion of muonium to antimuonium is one of the interesting charged lepton flavor violation phenomena offering a sensitive probe of potential new physics and serving as a tool to constrain the parameter space beyond the Standard Model. The Muonium-to-Antimuonium Conversion Experiment (MACE) is designed to utilize a high-intensity muon beam, a Michel electron magnetic spectrometer, a positron transport system, and a positron detection system, to either discover or constrain this rare process with a conversion probability of $\mathcal{O}(10^{-13})$. This article presents an overview of the theoretical framework as well as a detailed description of the experimental design for the search for muonium-to-antimuonium conversion.

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arXiv2025

Nonperturbative Dynamics in D-meson Mixing

Theoretical predictions for the $D^0\overline{D^0}$ mixing parameters fall significantly short of experimental measurements, with discrepancies spanning several orders of magnitude. This gap is mainly due to the Glashow-Iliopoulos-Maiani (GIM) mechanism, which suppresses leading-order contributions by high powers of $m_s/m_c$. However, higher-order corrections and nonperturbative effects could reduce this suppression, especially through flavor $SU(3)_F$ symmetry breaking. In this work, we investigate the long-distance contributions from QCD condensates, including, for the first time, the effects of mixed quark-gluon and four-quark condensates. Our results show an increase in the predicted values of $D^0\overline{D^0}$ mixing parameters by two orders of magnitude compared to perturbative NLO result, providing valuable insights into nonperturbative QCD dynamics. Although the theoretical estimates still fall below experimental values, this study represents an important step toward narrowing the gap between theory and observation, highlighting the significance of higher-order $1/m_c$ QCD effects in understanding $D^0\overline{D^0}$ mixing.

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arXiv2025

Searching for neutrino polarizability at DUNE

We perform an initial study of DUNE's sensitivity to enhanced neutrino polarizability within models of light scalar mediators. We identify two possible signatures of polarizability due to neutrino scattering on electrons and due to coherent scattering on argon nuclei. These result in either one or two separated electromagnetic showers, respectively, with no associated hadronic activity. For each signature we compute the signal rates and the relevant backgrounds, obtaining the projected reach of the DUNE near detector. We then compare this with the current astrophysical and terrestrial bounds on light scalar models coupling to neutrinos and/or photons.

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arXiv2025

Baryon Number Violation: From Nuclear Matrix Elements to BSM Physics

Processes that violate baryon number, most notably proton decay and $n\bar n$ transitions, are promising probes of physics beyond the Standard Model (BSM) needed to understand the lack of antimatter in the Universe. To interpret current and forthcoming experimental limits, theory input from nuclear matrix elements to UV complete models enters. Thus, an interplay of experiment, effective field theory, lattice QCD, and BSM model building is required to develop strategies to accurately extract information from current and future data and maximize the impact and sensitivity of next-generation experiments. Here, we briefly summarize the main results and discussions from the workshop "INT-25-91W: Baryon Number Violation: From Nuclear Matrix Elements to BSM Physics," held at the Institute for Nuclear Theory, University of Washington, Seattle, WA, January 13-17, 2025.

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arXiv2024

Finite width effects in nonleptonic D-decays

Many analyses of two-body non-leptonic decays of $D$-mesons rely on flavor SU(3) symmetry relations and fits of experimental data of decays rates to extract the universal transition amplitudes. Such fits assume that the final state mesons are well-defined asymptotic states of QCD. We develop a technique to take into account the finite width effects of the final state mesons and study their effects on the extracted values of transition amplitudes.

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arXiv2024

$D^0\overline{D^0}$ mixing from nonlocal condensate contributions

A significant discrepancy, spanning multiple orders of magnitude, exists between the leading order contribution to the $D^0\overline{D^0}$ mixing parameters and experimental values. This is largely due to the Glashow-Iliopoulos-Maiani (GIM) mechanism, which results in substantial suppression of the theoretical predictions. To bridge this gap, various efforts have been made to account for higher-order terms and nonperturbative effects, which, although suppressed in the operator product expansion (OPE), could potentially lead to a larger contribution by weakening the GIM cancellation through flavour SU(3) symmetry breaking. In this work, we compute the long-distance contributions of nonlocal QCD condensates within different models and, for the first time, determine the impact of the mixed condensate. Although our results still fall short of the experimental value, they represent an improvement over current theoretical estimates by an order of magnitude.

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arXiv2024

Constraints on light dark sector particles from lifetime difference of heavy neutral mesons

Heavy meson decays with missing energy in the final state offer interesting avenues to search for light invisible new physics such as dark matter (DM). In this context, we show that such new physics (NP) interactions also affect lifetime difference in neutral meson-antimeson mixing. We consider general dimension-six effective quark interactions involving a pair of DM particles and calculate their contributions to lifetime difference in beauty and charm meson systems. We use the latest data on mixing observables to constrain the relevant effective operators. We find that lifetime differences provide novel and complementary flavor constraints compared to those obtained from heavy meson decays.

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arXiv2024

Indirect constraints on third generation baryon number violation

The non-observation of baryon number violation suggests that the scale of baryon-number violating interactions at zero temperature is comparable to the GUT scale. However, the pertinent measurements involve hadrons made of the first-generation quarks, such as protons and neutrons. One may therefore entertain the idea that new flavour physics breaks baryon number at a much lower scale, but only in the coupling to a third generation quark, leading to observable baryon-number violating $b$-hadron decay rates. In this paper we show that indirect constraints on the new physics scale $Λ_{\rm BNV}$ from the existing bounds on the proton lifetime do not allow for this possibility. For this purpose we consider the three dominant proton decay channels $p \to \ell^+ ν_\ell \barν$, $p \to π^+ \barν$ and $p \to π^0 \ell^+$ mediated by a virtual bottom quark.

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arXiv2023

Report of the 2021 U.S. Community Study on the Future of Particle Physics (Snowmass 2021) Summary Chapter

The 2021-22 High-Energy Physics Community Planning Exercise (a.k.a. ``Snowmass 2021'') was organized by the Division of Particles and Fields of the American Physical Society. Snowmass 2021 was a scientific study that provided an opportunity for the entire U.S. particle physics community, along with its international partners, to identify the most important scientific questions in High Energy Physics for the following decade, with an eye to the decade after that, and the experiments, facilities, infrastructure, and R&D needed to pursue them. This Snowmass summary report synthesizes the lessons learned and the main conclusions of the Community Planning Exercise as a whole and presents a community-informed synopsis of U.S. particle physics at the beginning of 2023. This document, along with the Snowmass reports from the various subfields, will provide input to the 2023 Particle Physics Project Prioritization Panel (P5) subpanel of the U.S. High-Energy Physics Advisory Panel (HEPAP), and will help to guide and inform the activity of the U.S. particle physics community during the next decade and beyond.

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arXiv2022

Report of the Frontier For Rare Processes and Precision Measurements

This is the Snowmass 2021 Rare and Precision Frontier Report. The Rare Processes and Precision Measurements Frontier, referred to as the ``Rare and Precision Frontier", or RPF, encompasses searches for extremely rare processes or tiny deviations from the Standard Model (SM) that can be studied with intense sources and high-precision detectors. Our community studies have identified several unique research opportunities that may pin down the scales associated with New Physics (NP) interactions and constrain the couplings of possible new degrees of freedom. Searches for rare flavor transition processes and precision measurements are indispensable probes of flavor and fundamental symmetries, and provide insights into physics that manifests itself at higher energy or through weaker interactions than those directly accessible at high-energy colliders.

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arXiv2022

Snowmass2021 Whitepaper: Muonium to antimuonium conversion

The spontaneous muonium to antimuonium conversion is one of the interesting charged lepton flavor violation processes. It serves as a clear indication of new physics and plays an important role in constraining the parameter space beyond Standard Model. MACE is a proposed experiment to probe such a phenomenon and expected to enhance the sensitivity to the conversion probability by more than two orders of magnitude from the current best upper constraint obtained by the PSI experiment two decades ago. Recent developments in the theoretical and experimental aspects to search for such a rare process are summarized.

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arXiv2022

Studying $ΔL=2$ Lepton Flavor Violation with Muons

Flavor violating processes in the lepton sector have highly suppressed branching ratios in the standard model. Thus, observation of lepton flavor violation (LFV) constitutes a clear indication of physics beyond the standard model (BSM). We review new physics searches in the processes that violate the conservation of lepton (muon) flavor by two units with muonia and muonium--antimuonium oscillations.

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arXiv2021

Flavor $SU(3)$ in Cabibbo-favored $D$-meson decays

Model-independent description of nonleptonic decays of charmed mesons is a challenging task due to large nonperturbative effects of strong interactions on the transition amplitudes. We discuss the equivalence of two different flavor-$SU(3)$-based descriptions of Cabibbo-favored non-leptonic decays of charmed mesons to two-pseudoscalars final states including the $η$ and $η^\prime$ mesons.

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arXiv2020

Muonium-antimuonium oscillations in effective field theory

Flavor violating processes in the lepton sector have highly suppressed branching ratios in the standard model mainly due to the tiny neutrino mass. This means that observing lepton flavor violation (LFV) in the next round of experiments would constitute a clear indication of physics beyond the standard model (BSM). We revisit a discussion of one possible way to search for LFV, muonium-antimuonium oscillations. This process violates muon lepton number by two units and could be sensitive to the types of BSM physics that are not probed by other types of LFV processes. Using techniques of effective field theory, we calculate the mass and width differences of the mass eigenstates of muonium. We argue that its invisible decays give the parametrically leading contribution to the lifetime difference and put constraints on the scales of new physics probed by effective operators in muonium oscillations.

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