arXiv subjects

Avital Dery

Publications and source records attributed to Avital Dery.

At least 19 recordsLinked to original sources

arXiv2026

A CKM blind spot: probing $b$-column rescaling with kaons

CKM unitarity triangle constraints are insensitive to New Physics scenarios in which the $b$-column is uniformly rescaled. This is because B physics data over-constrain the angles of the (bd) unitarity triangle, but only calibrate its normalization. We identify this flat direction and derive model-independent constraints on the rescaling. We find that $|\varepsilon_K|$ already constrains the rescaling at the same level as the direct measurement of the $b$-column normalization, with current data allowing for ${\cal O}(4\%)$ deviations. Projected inputs promote the kaon sector to be the leading probe. A toy model employing mixing with a vector-like up-type singlet provides a proof of principle for a possible UV realization.

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arXiv2025

CP violation in $K\to\mu^+\mu^-$ with and without time dependence through a tagged analysis

We point out that using current knowledge of ${\cal B}(K^0_L\to\mu^+\mu^-)$ and $ {\cal B}(K^0_L\to \gamma\gamma)$, one can extract short-distance information from the combined measurement of the time-integrated CP asymmetry, $A_{\rm CP}(K^0\to\mu^+\mu^-)$, and of ${\cal B}(K^0_S\to\mu^+\mu^-)$. We discuss the interplay between this set of observables, and demonstrate that determining ${\rm sign}[A_{\rm CP}(K^0\to\mu^+\mu^-)]$ would eliminate the discrete ambiguity in the Standard Model prediction for ${\cal B}(K^0_L\to\mu^+\mu^-)$. We then move on to feasibility studies within an LHCb-like setup, using both time-integrated and time-dependent information, employing $K^0$ and $\overline K{}^0$ tagging methods. We find that, within an optimistic scenario, the short-distance amplitude, proportional to the CKM parameter combination $|A^2\lambda^5\bar\eta|$, could be constrained by LHCb at the level of about $35\%$ of its Standard Model value, and the discrete ambiguity in ${\cal B}(K^0_L\to\mu^+\mu^-)_{\rm SM}$ could be resolved at more than $3\sigma$ by the end of the high luminosity LHC.

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arXiv2025

Natural complex plane for kaon CKM data: framework, status and future

Kaon physics can be used to independently determine three out of the four parameters of the CKM matrix, without any B physics input. Treating one parameter, $|V_{us}|$, or alternatively Wolfenstein $λ$, as well known, we show that the natural plane for the presentation of kaon CKM information is spanned by the combinations $\left(A^2(1-\hatρ),\, A^2 \hatη\right)$. In this way, the use of B physics inputs is avoided, as well as the artificial inflation of errors due to parametric uncertainties, mainly due to $|V_{cb}|$. We show that the current status of kaon CKM constraints, impacted by recent advances in measurement and theory, is characterized by four allowed regions, and find that incoming data will inevitably disfavor a number of them, either confirming the CKM paradigm as dominant, or discovering a departure from the Standard Model.

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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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arXiv2024

Majorana phases beyond neutrinoless double beta decay

The $ν_M{\rm SM}$ is defined as the SM extended to include dimension-5 operators. In this model neutrino masses violate lepton number, and two parameters of the lepton mixing matrix, the Majorana phases, are yet to be constrained. One combination of these phases and the neutrino masses, often denoted by $m_{ee}$, is probed by neutrinoless double beta decays ($0νββ$). We explore what information may be obtained beyond $0νββ$, and how it depends on the lightest neutrino mass. We point out that with current central values of the mixing parameters, $ΔL_e=2$ and $ΔL_e=ΔL_μ= 1$ (or $ΔL_e=2$ and $ΔL_μ= 2$) processes cannot simultaneously vanish, providing a no-lose theorem, in principle, for excluding the $ν_M{\rm SM}$, even in the case of normal mass ordering.

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arXiv2024

Revisiting leptonic nonunitarity

In the presence of extra neutrino states at high scales, the low-energy effective $3\times 3$ leptonic mixing matrix (LMM) is in general nonunitary. We revisit the question of what is our current knowledge of individual LMM matrix elements without assuming unitarity. We first demonstrate that a minimal set of experimental constraints suffices in bounding LMM nonunitarity parameters to the level of ${\cal O}(10^{-3})$, without the use of neutrino oscillation data. We then revisit oscillation results as a complementary cross-check, using different physics and different experimental techniques to probe a similar parameter space. We correct some common misconceptions in the neutrino nonunitarity literature resulting from an incautious treatment of input parameters. We find that neutrino oscillation experiments can constrain LMM nonclosure, but, contrary to claims in the literature, are completely insensitive to the overall normalization of the LMM. Thus we conclude that oscillation experiments, including the future DUNE experiment, have no power in excluding nonunitarity altogether.

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arXiv2023

A Precision Relation between $Γ(K\toμ^+μ^-)(t)$ and ${\cal B}(K_L\toμ^+μ^-)/{\cal B}(K_L\toγγ)$

We find that the phase appearing in the unitarity relation between $\mathcal{B}(K_L\rightarrow μ^+μ^-)$ and $\mathcal{B}(K_L\rightarrow γγ)$ is equal to the phase shift in the interference term of the time-dependent $K\rightarrow μ^+μ^-$ decay. A probe of this relation at future kaon facilities constitutes a Standard Model test with a theory precision of about $2\%$. The phase has further importance for sensitivity studies regarding the measurement of the time-dependent $K\rightarrow μ^+μ^-$ decay rate to extract the CKM matrix element combination $\vert V_{ts} V_{td} \sin(β+β_s)\vert\approx A^2λ^5\barη$. We find a model-independent theoretically clean prediction, $\cos^2φ_0 = 0.96 \pm 0.03$. The quoted error is a combination of the theoretical and experimental errors, and both of them are expected to shrink in the future. Using input from the large-$N_C$ limit within chiral perturbation theory, we find a theory preference towards solutions with negative $\cosφ_0$, reducing a four-fold ambiguity in the angle $φ_0$ to a two-fold one.

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arXiv2023

New Physics Searches at Kaon and Hyperon Factories

Rare meson decays are among the most sensitive probes of both heavy and light new physics. Among them, new physics searches using kaons benefit from their small total decay widths and the availability of very large datasets. On the other hand, useful complementary information is provided by hyperon decay measurements. We summarize the relevant phenomenological models and the status of the searches in a comprehensive list of kaon and hyperon decay channels. We identify new search strategies for under-explored signatures, and demonstrate that the improved sensitivities from current and next-generation experiments could lead to a qualitative leap in the exploration of light dark sectors.

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arXiv2022

$K\to μ^{+} μ^{-}$ as a third kaon golden mode

Recent progress has demonstrated that the $K\toμ^+μ^-$ decay carries clean short-distance information, attainable from a measurement of time-dependence sensitive to $K_L-K_S$ interference effects. We review the ingredients that go into this proposed extraction, and discuss the sensitivity to the CKM parameter $\barη$ as well as to various NP scenarios.

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arXiv2022

CP violation in $b$ and $c$ quark decays

Generically, non-Standard-Model particles contribute to processes with order-one charge-parity (CP) violating phases, as CP is not a fundamental symmetry of nature. The exploration of CP violation becomes therefore a sensitive search for non-Standard-Model physics. We briefly review the current status of CP-violation studies in bottom- and charm-quark transitions focusing on those quantities that are most sensitive to non-Standard-Model contributions and discuss opportunities and challenges for the next decade and beyond.

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arXiv2021

$K\toμ^+μ^-$ beyond the standard model

We analyze the New Physics sensitivity of a recently proposed method to measure the CP-violating ${\cal B}(K_S\toμ^+μ^-)_{\ell=0}$ decay rate using $K_S - K_L$ interference. We present our findings both in a model-independent EFT approach as well as within several simple NP scenarios. We discuss the relation with associated observables, most notably ${\cal B}(K_L\toπ^0ν\barν)$. We find that simple NP models can significantly enhance ${\cal B}(K_S\toμ^+μ^-)_{\ell=0}$, making this mode a very promising probe of physics beyond the standard model in the kaon sector.

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arXiv2021

$K\to μ^{+} μ^{-}$ as a clean probe of short-distance physics

The $K\toμ^+μ^-$ decay is often considered to be uninformative of fundamental theory parameters since the decay is polluted by long-distance hadronic effects. We demonstrate that, using very mild assumptions and utilizing time-dependent interference effects, ${\cal B}(K_S\toμ^+μ^-)_{\ell=0}$ can be experimentally determined without the need to separate the $\ell=0$ and $\ell=1$ final states. This quantity is very clean theoretically and can be used to test the Standard Model. In particular, it can be used to extract the CKM matrix element combination $\left|V_{ts}V_{td}\sin(β+β_s)\right|\approx |A^2 λ^5 \bar η|$ with hadronic uncertainties below $1\%$.

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arXiv2021

Probing the $ΔU=0$ Rule in Three Body Charm Decays

CP violation in charm decay was observed in the decays $D^0\rightarrow P^{\pm}P^{\mp}$ of a $D^0$ meson to two pseudoscalars. When interpreted within the SM, the results imply that the ratio of the relevant rescattering amplitudes has a magnitude and phase that are both of $O(1)$. We discuss ways to probe similar ratios in $D^0\rightarrow V^{\pm}P^{\mp}$ decays, where $V$ is a vector that decays to two pseudoscalars, from the Dalitz-plot analysis of time-integrated three-body decays. Compared to two-body decays, three-body decays have the advantage that the complete system can be solved without the need for time-dependent CP violation measurements or use of correlated $D^0$--$\overline{D}^0$ production. We discuss the decays $D^0\rightarrow π^+π^-π^0$ and $D^0\rightarrow K^+K^-π^0$ as examples by considering a toy model of only two overlapping charged resonances, treating the underlying pseudo two-body decays in full generality.

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arXiv2020

SU(3)$_F$ Analysis for Beauty Baryon Decays

We perform a general SU(3)$_F$ analysis of $b\rightarrow c\bar{c}s(d)$ decays of members of the beauty baryon antitriplet to a member of the light baryon octet and a singlet. Under several reasonable assumptions we found $\left\vert \mathcal{A}(Ξ_b^0\rightarrow ΛS)/ \mathcal{A}(Ξ_b^0\rightarrow Ξ^0 S)\right\vert\approx 1/\sqrt{6}\, \left\vert V_{cb}^* V_{cd} / (V_{cb}^* V_{cs})\right\vert$ and $\left\vert\mathcal{A}(Λ_b\rightarrow Σ^0 S)/\mathcal{A}(Λ_b\rightarrow ΛS)\right\vert \sim 0.02$. These two relations have been recently probed by LHCb for the case of $S=J/ψ$. The former agrees with the measurement, while for the latter our prediction lies close to the upper bound set by LHCb.

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arXiv2019

Implications of the LHCb discovery of CP violation in charm decays

The recent measurement of $ΔA_{CP}$ by the LHCb collaboration requires an ${\cal O}(10)$ enhancement coming from hadronic physics in order to be explained within the SM. We examine to what extent can NP models explain $ΔA_{CP}$ without such enhancements. We discuss the implications in terms of a low energy effective theory as well as in the context of several explicit NP models.

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arXiv2019

Dark Matter in Very Supersymmetric Dark Sectors

If supersymmetry exists at any scale, regardless of whether it is restored around the weak scale, it may be a good symmetry of the dark sector, enforcing a degeneracy between its lowest lying fermions and bosons. We explore the implications of this scenario for the early universe and dark matter, as well as the corresponding signatures. In particular we show that the thermal history of the dark sector results in co-decaying dark matter in much of the parameter space. This implies new phenomenological signatures and presents a new way to discover high scale supersymmetry.

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arXiv2017

Large Higgs-electron Yukawa coupling in 2HDM

The present upper bound on $κ_e$, the ratio between the electron Yukawa coupling and its Standard Model value, is of ${\cal O}(600)$. We ask what would be the implications in case that $κ_e$ is close to this upper bound. The simplest extension that allows for such enhancement is that of two Higgs doublet models (2HDM) without natural flavor conservation. In this framework, we find the following consequences: (i) Under certain conditions, measuring $κ_e$ and $κ_V$ would be enough to predict values of Yukawa couplings for other fermions and for the $H$ and $A$ scalars. (ii) In the case that the scalar potential has a softly broken $Z_2$ symmetry, the second Higgs doublet must be light, but if there is hard breaking of the symmetry, the second Higgs doublet can be much heavier than the electroweak scale and still allow the electron Yukawa coupling to be very different from its SM value. (iii) CP must not be violated at a level higher than ${\cal O}(0.01/κ_e)$ in both the scalar potential and the Yukawa sector. (iv) LHC searches for $e^+e^-$ resonances constrain this scenario in a significant way. Finally, we study the implications for models where one of the scalar doublets couples only to the first generation, or only to the third generation.

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arXiv2017

Testing Minimal Flavor Violation in Leptoquark Models of the $R_{K^{(*)}}$ Anomaly

The $R_{K^{(*)}}$ anomaly can be explained by tree level exchange of leptoquarks. We study the consequences of subjecting these models to the principle of minimal flavor violation (MFV). We consider MFV in the linear regime, and take the charged lepton Yukawa matrix to be the only spurion that violates lepton flavor universality. We find that a combination of constraints from a variety of processes -- $b\to sμμ$, $b\to sττ$, $b\to sνν$, $b\bar b\toττ$ and $b\to cτν$ -- excludes MFV in these models.

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