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Eleftheria Malami

Publications and source records attributed to Eleftheria Malami.

28 records · Page 2Linked to original sources
arXiv2022

Using $B^0_s\to D_s^\mp K^\pm$ Decays as a Portal to New Physics

The system of $B^0_s\to D_s^\mp K^\pm$ decays offers a theoretically clean determination of the angle $γ$ of the Unitarity Triangle. A corresponding LHCb analysis resulted in a surprisingly large result, which is in tension with other determinations and global analyses of the Unitarity Triangle. Paying special attention to discrete ambiguities, we confirm this picture and resolve a final ambiguity. Moreover, we extract the branching ratios of the underlying $\bar{B}^0_s\to D_s^+K^-$ and $\bar{B}^0_s\to D_s^- K^+$ modes. Combining them with information from semileptonic $B_{(s)}$ decays, we arrive at another puzzling situation, which we obtain also for other decays with similar dynamics. These patterns could be footprints of New Physics in the $b\to c \bar{u} s$ and $b \to u \bar{c} s$ processes which govern the dynamics of the $\bar{B}^0_s\to D_s^\mp K^\pm$ channels. Employing a model-independent parametrisation, we present a strategy to reveal such effects. Applying it to the present data, we obtain strongly correlated New-Physics contributions with potentially large CP-violating phases. We find that new contributions sizeably smaller than the Standard Model amplitudes could actually accommodate the current data. This strategy offers an exciting probe for new sources of CP violation at the future high-precision frontier of $B$ physics.

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arXiv2022

Penguin Effects in $B_d^0\to J/ψK^0_S$ and $B_s^0\to J/ψϕ$

Controlling the contributions from doubly Cabibbo-suppressed penguin topologies in the decays $B_d^0\to J/ψK^0_S$ and $B_s^0\to J/ψϕ$ is mandatory to reach the highest possible precision in the measurement of the $B^0_q$--$\bar B^0_q$ ($q=d,s$) mixing phases $ϕ_d$ and $ϕ_s$. The penguin contributions can be determined using a strategy based on the $SU(3)$ flavour symmetry of QCD. Using the latest experimental data, we update our combined analysis of the decays $B_d^0\to J/ψK^0_S$, $B_s^0\to J/ψϕ$ and their control channels $B_s^0\to J/ψK^0_S$, $B_d^0\to J/ψπ^0$ and $B_d^0\to J/ψρ^0$. This allows us to simultaneously determine the penguin parameters and both mixing phases. We discuss how the branching fractions of these decays can be used to probe the size of non-factorisable $SU(3)$-breaking effects, which form the main theoretical uncertainty associated with our $SU(3)$-based strategy, and provide new insights into the factorisation approach.

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arXiv2022

Puzzles in the $B^0_s \rightarrow D_s^{\pm} K^{\mp} $ System

Non-leptonic $B^0_s \rightarrow D_s^{\pm} K^{\mp}$ transitions are particularly interesting processes to test the Standard Model. As these decays occur via pure tree diagrams, they allow a theoretically clean determination of the angle $γ$ of the unitarity triangle. Considering recent LHCb results, an intriguing picture arises, showing tension with the Standard Model. Extracting the branching ratios of the underlying $\bar{B}^0_s \rightarrow D_s^{\pm} K^{\mp}$ modes and combining them with information from semileptonic $B_{(s)}$ decays, we arrive at another puzzling situation, in accordance with similar decays. These patterns could be footprints of New Physics. We present a model-independent strategy to include such New-Physics effects and apply it to the data. Interestingly, new contributions of moderate size could accommodate the data. This formalism offers an exciting probe for new sources of CP violation at the future high-precision B physics era.

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arXiv2021

Searching for New Physics with $B^0_s \rightarrow D_s^{\pm} K^{\mp} $ Decays

Particularly interesting processes to test the Standard Model are non-leptonic $B^0_s \rightarrow D_s^{\pm} K^{\mp}$ transitions. As these decays occur via pure tree diagrams, they allow a theoretically clean determination of the angle $γ$ of the unitarity triangle. Considering recent LHCb results, an intriguing picture arises, showing tension with the Standard Model. Utilising the available experimental data, we perform a theoretical analysis in order to shed more light on these puzzling patterns. Do these puzzles actually indicate footprints of New Physics?

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arXiv2021

In Pursuit of New Physics with $B_d^0\to J/ψK^0$ and $B_s^0\to J/ψϕ$ Decays at the High-Precision Frontier

The decays $B_d^0\to J/ψK^0_{\text{S}}$and $B_s^0\to J/ψϕ$ play a key role for the determination of the $B^0_q$-$\bar B^0_q$ ($q=d,s$) mixing phases $ϕ_d$ and $ϕ_s$, respectively. The theoretical precision of the extraction of these quantities is limited by doubly Cabibbo-suppressed penguin topologies, which can be included through control channels by means of the $SU(3)$ flavour symmetry of strong interactions. Using the currently available data and a new simultaneous analysis, we discuss the state-of-the-art picture of these effects and include them in the extracted $ϕ_q$ values. We have a critical look at the Standard Model predictions of these phases and explore the room left for new physics. Considering future scenarios for the high-precision era of flavour physics, we illustrate that we may obtain signals for physics beyond the Standard Model with a significance well above five standard deviations. We also determine effective colour-suppression factors of $B_d^0\to J/ψK^0$, $B_d^0\to J/ψK^0_{\text{S}}$ and $B_d^0\to J/ψπ^0$ decays, which serve as benchmarks for QCD calculations of the underlying decay dynamics, and present a new method using information from semileptonic $B_d^0\toπ^-\ell^+ν_{\ell}$ and $B_s^0\to K^-\ell^+ν_{\ell}$ decays.

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arXiv2020

Exploring New Physics in $B \rightarrow πK$ Decays

B-meson decays play an important role in flavour physics. The $B \rightarrow πK$ decays are dominated by QCD loop diagrams (penguins) but also electroweak penguins, where New Physics may enter, have a significant impact on the decay amplitude. Since measurements from B-factories indicate deviations from the Standard Model picture, we perform a state-of-the-art analysis to explore the correlation of the CP asymmetries and to get an updated picture. We propose a strategy for the optimal determination of the parameters which describe electroweak penguin effects and apply it to current data, utilising both neutral and charged $B \rightarrow πK$ decays. This new method can be fully exploited at the future Belle-II experiment, which will hopefully answer the question: Do these decays imply New Physics?

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arXiv2018

Probing New Physics in $B\toπK$ Decays

Over the last two decades, $B \to πK$ modes have received a lot of attention. They are particularly interesting since the main contribution to these decays comes from QCD penguin topologies. Furthermore, electroweak penguin amplitudes enter at a level comparable to the tree topologies. In the past, a discrepancy was found in the correlation between the CP asymmetries of $B_d^0 \to π^0 K_{\rm S}$. We provide the state-of-the-art picture of this situation and consider new constraints, finding that the effect has become larger. An attractive explanation is offered by a modified electroweak penguin sector. We propose a new method to determine the relevant parameters. It employs an isospin relation between the amplitudes of the $B \to πK$ decays, and makes only minimal use of the $SU(3)$ flavour symmetry. Using current data as well as future scenarios, we demonstrate how the mixing-induced CP asymmetry of $B_d^0 \to π^0 K_{\rm S}$ plays a key role in this analysis. The application of our strategy at the next generation of $B$-physics experiments may establish New Physics and reveal new sources of CP violation in the electroweak penguin sector.

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arXiv2018

Exploring $B\toππ, πK$ Decays at the High-Precision Frontier

The $B\toππ,πK$ system offers a powerful laboratory to probe strong and weak interactions. Using the isospin symmetry, we determine hadronic $B\toππ$ parameters from data where new measurements of direct CP violation in $B^0_d\toπ^0π^0$ resolve a discrete ambiguity. With the help of the $SU(3)$ flavour symmetry, the $B\toππ$ parameters can be converted into their $B\toπK$ counterparts, thereby allowing us to make predictions of observables. A particularly interesting decay is $B^0_d\toπ^0 K_{\rm S}$ as it exhibits mixing-induced CP violation. Using an isospin relation, complemented with a robust $SU(3)$ input, we calculate correlations between the direct and mixing-induced CP asymmetries of $B^0_d\toπ^0 K_{\rm S}$, which are the theoretically cleanest $B\toπK$ probes. Interestingly, they show tensions with respect to the Standard Model. Should this $B\toπK$ puzzle originate from New Physics, electroweak penguins offer an attractive scenario for new particles to enter. We present a strategy to determine the parameters characterising these topologies and obtain the state-of-the-art picture from current data. In the future, this method will allow us to reveal the $B\toπK$ dynamics and to obtain insights into the electroweak penguin sector with unprecedented precision.

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arXiv2018

Utilising $B \to πK$ Decays at the High-Precision Frontier

For about twenty years, $B\toπK$ decays are in the focus of $B$-decay studies. We show that a correlation between the CP asymmetries of $B^0_d\toπ^0K_{\rm S}$ reveals a tension with the Standard Model. Should it be due to New Physics, a modified electroweak penguin sector provides particularly interesting possibilities. We present a new method to determine the electroweak penguin parameters, which uses an isospin relation and requires only minimal $SU(3)$ input. We apply it to the current data for $B\toπK$ decays and discuss the prospects for utilizing CP violation in $B^0_d\toπ^0K_{\rm S}$. The strategy has the exciting potential to establish New Physics in the electroweak penguin sector in the high-precision era of $B$-physics.

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