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Eleftheria Malami

Publications and source records attributed to Eleftheria Malami.

At least 19 recordsLinked to original sources
arXiv2026

QCD-factorization amplitudes from flavour symmetries: beyond the $SU(3)$ symmetric case

Using experimental information on branching ratios as well as direct and mixing-induced CP asymmetries, we perform a data-driven analysis of charmless non-leptonic $B \to PP$ decays, where $P$ is any of the light pseudoscalar mesons. Implementing flavour-$SU(3)$ breaking at the level of transition form factors, decay constants and phase space factors, we find a good fit to the current experimental data. Our best-fit point materializes in QCD-factorization amplitudes whose central values resemble many features of the dynamical predictions obtained within the QCD factorization framework. Moreover, we do not find any strong indications that the size of annihilation amplitudes is numerically enhanced beyond the naïve $Λ_{\textrm{QCD}}/m_b$ scaling. Subsequently, we address a number of phenomenological applications, among which are various flavour puzzles that have been persisting in non-leptonic $B$ decays for quite some time.

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arXiv2026

Shedding New Light on the ${B \to πK}$ Puzzle

The $B \to πK$ system provides a rich laboratory for testing the Standard Model and studying CP violation. A particularly important channel is $B^0_d\toπ^0 K_{\rm S}$, the only mode exhibiting both direct and mixing-induced CP violation. Recent Belle II measurements of the CP asymmetries in this decay provide valuable new input. An updated analysis incorporating these new data provides new insight on the long-standing $B \to πK$ puzzle. Looking ahead to the high-precision era of flavour physics, the $B \to πK$ system can be further exploited to potentially reveal new sources of CP violation.

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arXiv2026

How to tame penguins: Advancing to high-precision measurements of $ϕ_d$ and $ϕ_s$

The complex phases $ϕ_d$ and $ϕ_s$, associated with the mixing between neutral $B_q^0$ and $\bar B_q^0$ mesons ($q\in\{d,s\}$), are key observables to test the Standard Model and search for contributions from new physics. They are conventionally determined from the measurements of mixing-induced CP violation in the decays $B_d^0\to J/ψK^0$, $B_s^0\to J/ψϕ$ and $B_s^0\to D_s^+D_s^-$. To reach the highest possible precision on $ϕ_d$ and $ϕ_s$, it is crucial that corrections from next-to-leading order effects - primarily associated with penguin decay topologies - are accounted for. The strategy adopted in this paper uses the $SU(3)$ flavour symmetry of QCD to relate the unknown contributions from penguin topologies to their counterparts in suitably-chosen control modes, where their effects are enhanced. Utilising new CP asymmetry measurements from LHCb on the decays $B_s^0\to D_s^+D_s^-$, $B_d^0\to D^+D^-$, $B^+\to J/ψK^+$ and $B^+\to J/ψπ^+$, as well as from Belle-II on the decay $B_d^0\to J/ψπ^0$, we present the current state-of-the-art picture on controlling the penguin contributions and extract $ϕ_d$ and $ϕ_s$ from the corresponding observables. We explore the prospects for the end of the Belle-II and HL-LHC flavour physics programmes, and demonstrate the importance of measuring the control modes with future data.

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arXiv2025

Subatomic Heroes

Sharing the amazing achievements of the (particle) physics world with the general public is at the heart of the mission of the Subatomic Heroes, based at the University of Siegen, Germany. Originally this started out as an endeavor of theoretical particle physics, now we are steadily spreading out to cover and include more branches of physics and science. Our activities range from merging art with public physics lectures via marvelous artistic performances at the local theater, over dedicated events for high-school students, to our Subatomic Heroes channel on Instagram and TikTok where you may also find out when and where our famous "hadronic ice-cream" will be served next! So follow us on https://www.instagram.com/subatomic_heroes and https://www.tiktok.com/@subatomic_heroes.

physics.ed-ph↗
arXiv2025

Kaon Physics: A Cornerstone for Future Discoveries

The kaon physics programme, long heralded as a cutting-edge frontier by the European Strategy for Particle Physics, continues to stand at the intersection of discovery and innovation in high-energy physics (HEP). With its unparalleled capacity to explore new physics at the multi-TeV scale, kaon research is poised to unveil phenomena that could reshape our understanding of the Universe. This document highlights the compelling physics case, with emphasis on exciting new opportunities for advancing kaon physics not only in Europe but also on a global stage. As an important player in the future of HEP, the kaon programme promises to drive transformative breakthroughs, inviting exploration at the forefront of scientific discovery.

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arXiv2025

Taming Penguins: Towards High Precision Measurements in $ϕ_d$ and $ϕ_s$

Experimentally, the phases $ϕ_d$ and $ϕ_s$ are determined from CP asymmetry measurements in the "golden modes" $B_d^0\to J/ψK_{\mathrm{S}}^0$ and $B_s^0\to J/ψϕ$. At leading order, the theoretical interpretation of these measurements is straightforward. However, to reach high precision determinations of $ϕ_d$ and $ϕ_s$, which is essential in view of the searches for signs of beyond the SM physics, corrections from next-to-leading order effects need to be accounted for. These corrections primarily originate from so-called penguin topologies. Using the $SU(3)$ flavour symmetry, these corrections can be determined using suitably chosen control modes. Recent new CP asymmetry measurements from LHCb in $B\to DD$ and Belle-II in $B_d^0\to J/ψπ^0$ decays greatly improve our knowledge on the parameters describing the contribution from penguin topologies. These proceedings will discuss the current constraints on the penguin parameters in $B\to J/ψX$ and $B\to DD$ decays, provide corrected determinations for $ϕ_d$ and $ϕ_s$, and highlight what can be expected at the end of the HL-LHC and Belle-II programmes.

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arXiv2024

Targeting (Pseudo)-Scalar CP Violation with $B_s \to μ^+μ^-$

The leptonic decay $B_s \to μ^+μ^-$ is both rare and theoretically clean, making it an excellent probe for New Physics searches. Due to its helicity suppression in the Standard Model, this decay is particularly sensitive to new (pseudo)-scalar contributions. We present a new strategy for detecting CP-violating New Physics contributions of this kind, exploiting two observables: $\mathcal{A}_{ΔΓ_s}^{μμ}$, which is accessible due to the sizeable decay width difference of the $B_s$ system, and the mixing-induced CP asymmetry $\mathcal{S}_{μμ}$. The strategy also uses information from $B\to K^{(*)} μ^+μ^-$ and $B_s\to ϕμ^+μ^-$ decays. We find remarkably constrained regions in the $\mathcal{A}_{ΔΓ_s}^{μμ}$-$\mathcal{S}_{μμ}$ plane that serve as promising targets for future measurements.

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arXiv2024

CP Violation in $B \to K\ell^+\ell^-$ Decays: New Opportunities in the High-Precision Era

Experimental data on rare $B$-meson decays indicate deviations from Standard Model predictions. In studies of these decays, possible new sources of CP violation are often neglected. We discuss CP violation in the rare $B$-meson decays $B\to K\ell^+\ell^- (\ell = μ,e)$ and point to two phenomena that arise when new sources of CP violation are included. First, the Wilson coefficients $C_{9\ell}$ and $C_{10\ell}$ become complex, and we show how we can extract their values from measurements of direct and mixing-induced CP asymmetries. Second, new sources of CP violation can generate nontrivial lepton flavour universality violation. Such a violation is usually measured through ratios like $R_K$ and $R_{K^*}$, but we show that measuring only these ratios leaves a large parameter space unexplored. These results bring exciting opportunities to reveal New Physics effects in the high-precision era.

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arXiv2024

Theoretical Highlights of CP Violation in $B$ Decays

In this presentation, we discuss recent key topics in theoretical analyses of CP violation in benchmarks decays of the $B$ meson. We provide the most updated values of the mixing phases and discuss the importance of including the penguin contributions in their studies. Exploring intriguing patterns in purely tree decays, interesting new methodologies can be developed and applied. New data related to the CP asymmetries of key modes like $B^0_d \to π^0 K_S$ and $B^0_s \to K^+ K^-$ lead to interesting results. The new $R_{K^{(*)}}$ measurement, compatible with the Standard Model, can still allow for electron-muon symmetry violation through new sources of CP violation.

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arXiv2024

Manifestations of CP Violation in the B Meson System: Theoretical Perspective

CP violation in the field of $B$ physics is a crucial topic for exploring the quark sector and search for New Physics, both for theorists and experimentalists. CP violation manifests itself in various ways and in this presentation, we will categorise the decays based on their different dynamics. We aim to present highlights related to the studies of CP violation in each category from a theoretical perspective.

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arXiv2023

New Probes of Electron--Muon Universality in $B \to K\ell^+\ell^-$ Decays

In the pursuit of physics beyond the Standard Model, a promising path is the study of B-meson decays caused by the transition $b \to s\ell^+\ell^-$. A key observable in such decays is the ratio $R_K$, which measures electron--muon universality in $B \to K μ^+μ^-/e^+e^-$. At first sight, the recent LHCb measurement of $R_K \sim 1$ may seem to largely constrain deviations from universality in these decays. However, we show that this is actually not the case: new sources of CP violation allow for significant universality violation consistent with $R_K \sim 1$. This provides an exciting new opportunity to search for New Physics by measuring differences between CP asymmetries in $B \to Kμ^+μ^-$ and $B \to K e^+e^-$.

hep-ph↗
arXiv2023

Revealing New Physics in $B^0_s\to D_s^\mp K^\pm$ Decays

The $B^0_s\to D_s^\mp K^\pm$ system offers a determination of the Unitarity Triangle angle $γ$. Intrigued by an LHCb analysis showing a surprisingly large result in tension with information on the Unitarity Triangle and other $γ$ measurements, we make a transparent study of the measured observables, confirming the LHCb picture. The corresponding $γ$ puzzle at the $3σ$ level would require CP-violating contributions of New Physics, which should also manifest themselves in the corresponding decay branching ratios. Indeed, we find that the rates of the individual $B^0_s\to D_s^\mp K^\pm$ channels show puzzling patterns, in accordance with similar decays, with tensions up to $4.8σ$, thereby making the situation much more exciting. We present a formalism to include New-Physics effects in a model-independent way and apply it to the data to constrain the corresponding parameters. Interestingly, new contributions of moderate size could accommodate the data. Utilising this formalism in the future high-precision $B$ physics era may allow us to finally establish new sources of CP violation.

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arXiv2023

New Perspectives for Testing Electron-Muon Universality

Intriguing results for tests of the universality of electrons and muons through measurements of rates of $B\to K \ell^+ \ell^-$ and similar decays have been in the spotlight for years. The LHCb collaboration has recently reported new results which are in agreement with Lepton Flavour Universality, while the individual decay rates are found below their Standard Model predictions. In view of this new situation, we explore how much space is left for a violation of electron-muon universality. Considering new sources of CP violation and taking the new LHCb measurements into account, we show that significant differences between the short-distance coefficients for electronic and muonic final states are actually allowed by the current data. These patterns can be revealed through CP asymmetries in neutral and charged $B\to K \ell^+ \ell^-$ decays. We obtain correlations between these observables and map them to the short-distance coefficients. This results in regions in New Physics parameter space with large differences between CP asymmetries of the decays with final-state electrons and muons, thereby leaving a lot of room for possible surprises in the future high-precision era.

hep-ph↗
arXiv2023

New Physics in $B_q^0-\bar B_q^0$ Mixing: Present Challenges, Prospects, and Implications for $B_q^0\toμ^+μ^-$

The phenomenon of $B^0_q-\bar B^0_q$ mixing ($q=d,s$) provides a sensitive probe for physics beyond the Standard Model. We explore the corresponding space for New Physics left through the current data, having a careful look at analyses of the Unitarity Triangle that are needed for the Standard Model predictions of the $B_q$ mixing parameters. In particular, we explore the impact of tensions between inclusive and exclusive determinations of the CKM matrix elements $|V_{ub}|$ and $|V_{cb}|$. Moreover, we focus on the angle $γ$ of the Unitarity Triangle, comparing measurements from $B\to DK$ and $B\toππ$, $ρπ$, $ρρ$ decays, where the latter are typically interpreted in terms of the angle $α$. We discuss various scenarios and present the corresponding state-of-the-art constraints on the New Physics parameters of $B_q^0-\bar B_q^0$ mixing. We point out that these results have an interesting application in the analysis of rare $B_q^0\to μ^+μ^-$ decays, allowing us to minimise the impact of CKM parameters in the search for New Physics. In view of the high-precision era, we make future projections. Interestingly, we find that for the extraction of the New Physics parameters in the $B_d$ system the determination of the apex of the Unitarity Triangle results in a key limiting factor. By contrast, the corresponding impact is negligible for the $B_s$ system, making it a promising candidate to reveal sources of New Physics.

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arXiv2023

Studies of New Physics in $B^0_q-\bar{B}^0_q$ Mixing and Implications for Leptonic Decays

The phenomenon of $B^0_q$-$\bar{B}^0_q$ mixing ($q=d,s$) provides a sensitive probe for physics beyond the Standard Model. We have a careful look at the determination of the Unitarity Triangle apex, which is needed for the Standard Model predictions of the $B_q$ mixing parameters, and explore how much space for New Physics is left through the current data. We study the impact of tensions between inclusive and exclusive determinations of the CKM matrix elements $|V_{ub}|$ and $|V_{cb}|$, and focus on the $γ$ angle extraction. We present various future scenarios and discuss the application of these results for leptonic rare $B$ decays, which allows us to minimise the CKM parameter impact in the New Physics searches. Performing future projections, we explore and illustrate the impact of increased precision on key input quantities. It will be exciting to see how more precise data in the future high-precision era of flavour physics can lead to a much sharper picture.

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arXiv2022

Fingerprinting CP-violating New Physics with $B \to Kμ^+μ^-$

The $B \to K \ell^+ \ell^-$ system is particularly interesting to explore physics beyond the Standard Model. Such effects could provide new sources of CP violation, thereby giving rise to Wilson coefficients which could not only be real, as assumed in most analyses, but also be complex. We propose a new strategy to extract the complex $C_{9 μ}$, $C_{10 μ}$ from the data, utilising the complementarity of direct CP violation in $B^+\to K^+ μ^+μ^-$ and mixing-induced CP violation arising - in addition to direct CP violation - in $B^0_d \to K_{S} μ^+μ^-$, as well as the differential rate in appropriate $q^2$ bins. The long-distance effects, which play a key role to generate the direct CP asymmetries, cannot be reliably calculated due to their non-perturbative nature. In order to describe them, we apply a model by the LHCb Collaboration employing experimental data. Assuming specific scenarios, we demonstrate the fingerprinting of CP-violating New Physics and the distinction between ambiguities in the model of the long-distance contributions. Finally, New Physics could couple differently to muons and electrons, as probed through the lepton flavour universality ratio $R_K$. We discuss these effects in the presence of CP violation and present a new way to measure the direct CP asymmetries of the $B \to K e^+ e^-$ channels.

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arXiv2022

CP Violation and Mixing in Beauty Sector: A Theoretical Overview

We provide an overview of the latest progress in the study of CP violation and mixing in the $B$ meson decays. Studying the $B^0_d \to J/ψK^0_S$ and $B^0_s \to J/ψϕ$ decays, we focus on the determination of the mixing phases $ϕ_d$ and $ϕ_s$, including hadronic uncertainties with the help of the data. CP violation in the non-leptonic decays $B \to πK$ and $B^0_s \to D_s^{\mp} K^{\pm}$ indicate puzzling patterns. Could these puzzles indicate New Physics?

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