arXiv subjects

Elena Venturini

Publications and source records attributed to Elena Venturini.

12 recordsLinked to original sources

arXiv2026

An EFT study of the $pp \to \bar{t} t Z(ll) h(bb)$ process at the FCC-$\boldsymbol{hh}$

We carry out an Effective Field Theory (EFT) study of the $pp \to \bar{t} t Zh$ process in the $4b + 3 \ell + \ge 2j + \slashed{E}_T$ final state. This process can uniquely probe the $\bar{t} t Zh$ couplings arising from higher dimensional EFT operators and can also provide bounds on $\bar{t} t Z$ coupling deviations. We highlight the importance of the proposed proton-proton Future Circular Collider (FCC-$hh$) to study this process and then perform a complete collider analysis by examining the relevant background processes. This allows us to determine the FCC-$hh$ sensitivity to probe anomalous $\bar{t} t Zh$ couplings.

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arXiv2023

Electric dipole moments at one-loop in the dimension-6 SMEFT

In this paper we present the complete expressions of the lepton and neutron electric dipole moments (EDMs) in the Standard Model Effective Field Theory (SMEFT), up to 1-loop and dimension-6 level and including both RG running contributions and finite corrections. The latter play a fundamental role in the cases of operators that do not renormalize the dipoles, but there are also classes of operators for which they provide an important fraction, $10-20\%$, of the total 1-loop contribution, if the new physics scale is around $Λ=5$ TeV. We present the full set of bounds on each individual Wilson coefficient contributing to the EDMs using both the current experimental constraints, as well as those from future experiments, which are expected to improve by at least an order of magnitude.

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arXiv2022

The Exclusive Vision of Rare $K$ and $B$ Decays and of the Quark Mixing in the Standard Model

The most common predictions for rare $K$ and $B$ decay branching ratios in the Standard Model are based on the CKM elements $|V_{cb}|$ and $|V_{ub}|$ resulting from global fits, that are in the ballpark of their inclusive and exclusive determinations, respectively. In the present paper we follow another route. We assume that the future true values of $|V_{cb}|$ and $|V_{ub}|$ will be both from exclusive determinations and set them equal to the most recent ones from FLAG. An unusual pattern of SM predictions results from this study with some existing tensions being dwarfed and new tensions being born. In particular using the HPQCD $B^0_{s,d}-\bar B^0_{s,d}$ hadronic matrix elements a $3.1σ$ tension in $ΔM_s$ independently of $γ$ is found. For $60^\circ\leγ\le 75^\circ$ the tension in $ΔM_d$ between $4.0σ$ and $1.1σ$ is found and in the case of $ε_K$ between $5.2σ$ and $2.1σ$. Moreover, the room for new physics in $K^+\toπ^+ν\barν$, $K_L\toπ^0ν\barν$ and $B\to K(K^*)ν\barν$ decays is significantly increased. We compare the results in this EXCLUSIVE scenario with the HYBRID one in which $|V_{cb}|$ in the former scenario is replaced by the most recent inclusive $|V_{cb}|$ and present the dependence of all observables considered by us in both scenarios as functions of $γ$. We also compare the determination of $|V_{cb}|$ from $ΔM_s$, $ΔM_d$, $ε_K$ and $S_{ψK_S}$ using $B^0_{s,d}-\bar B^0_{s,d}$ hadronic matrix elements from LQCD with $2+1+1$ flavours, $2+1$ flavours and their average. Only for the $2+1+1$ case values for $β$ and $γ$ exist for which the same value of $|V_{cb}|$ is found: $|V_{cb}|=42.6(4)\times 10^{-3}$. This in turn implies a $2.7σ$ anomaly in $B_s\toμ^+μ^-$.

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arXiv2022

Searching for New Physics in Rare $K$ and $B$ Decays without $|V_{cb}|$ and $|V_{ub}|$ Uncertainties

We reemphasize the strong dependence of the branching ratios $B(K^+\toπ^+ν\barν)$ and $B(K_L\toπ^0ν\barν)$ on $|V_{cb}|$ that is stronger than in rare $B$ decays, in particular for $K_L\toπ^0ν\barν$. Thereby the persistent tension between inclusive and exclusive determinations of $|V_{cb}|$ weakens the power of these theoretically clean decays in the search for new physics (NP). We demonstrate how this uncertainty can be practically removed by considering within the SM suitable ratios of the two branching ratios between each other and with other observables like the branching ratios for $K_S\toμ^+μ^-$, $B_{s,d}\toμ^+μ^-$ and $B\to K(K^*)ν\barν$. We use as basic CKM parameters $V_{us}$, $|V_{cb}|$ and the angles $β$ and $γ$ in the unitarity triangle (UT). This avoids the use of the problematic $|V_{ub}|$. A ratio involving $B(K^+\toπ^+ν\barν)$ and $B(B_s\toμ^+μ^-)$ while being $|V_{cb}|$-independent exhibits sizable dependence on the angle $γ$. It should be of interest for several experimental groups in the coming years. We point out that the $|V_{cb}|$-independent ratio of $B(B^+\to K^+ν\barν)$ and $B(B_s\toμ^+μ^-)$ from Belle II and LHCb signals a $1.8σ$ tension with its SM value. As a complementary test of the Standard Model, we propose to extract $|V_{cb}|$ from different observables as a function of $β$ and $γ$. We illustrate this with $ε_K$, $ΔM_d$ and $ΔM_s$ finding tensions between these three determinations of $|V_{cb}|$ within the SM. From $ΔM_s$ and $S_{ψK_S}$ alone we find $|V_{cb}|=41.8(6)\times 10^{-3}$ and $|V_{ub}|=3.65(12)\times 10^{-3}$. We stress the importance of a precise measurement of $γ$. We obtain most precise SM predictions for considered branching ratios of rare K and B decays to date.

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arXiv2022

Standard Model Predictions for Rare $K$ and $B$ Decays without $|V_{cb}|$ and $|V_{ub}|$ Uncertainties

The persistent tensions between inclusive and exclusive determinations of $|V_{cb}|$ and $|V_{ub}|$ weaken the power of theoretically clean rare $K$ and $B$ decays in the search for new physics (NP). We demonstrate how this uncertainty can be practically removed by considering within the SM suitable ratios of various branching ratios. This includes the branching ratios for $K^+\toπ^+ν\barν$, $K_{L}\toπ^0ν\barν$, $K_S\toμ^+μ^-$, $B_{s,d}\toμ^+μ^-$ and $B\to K(K^*)ν\barν$. Also $ε_K$, $ΔM_d$, $ΔM_s$ and the mixing induced CP-asymmetry $S_{ψK_S}$, all measured already very precisely, play an important role in this analysis. The highlights of our analysis are 16 $|V_{cb}|$ and $|V_{ub}|$ independent ratios that often are independent of the CKM arameters or depend only on the angles $β$ and $γ$ in the Unitarity Triangle with $β$ already precisely known and $γ$ to be measured precisely in the coming years by the LHCb and Belle II collaborations. Once $γ$ Once $γ$ is measured precisely these 16 ratios taken together are expected to be a powerful tool in the search for new physics. Assuming no NP in $|ε_K|$ and $S_{ψK_S}$ we determine independently of $|V_{cb}|$: $\mathcal{B}(K^+\toπ^+ν\barν)_\text{SM}= (8.60\pm0.42)\times 10^{-11}$ and $\mathcal{B}(K_L\toπ^0ν\barν)_\text{SM}=(2.94\pm 0.15)\times 10^{-11}$. This are the most precise determinations to date. Assuming no NP in $ΔM_{s,d}$ allows to obtain analogous results for all $B$ decay branching ratios considered in our paper without any CKM uncertainties.

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arXiv2021

From B-meson anomalies to Kaon physics with scalar leptoquarks

In this work we study possible connections between $B$-meson anomalies and Kaon physics observables in the context of combined solutions with the singlet and triplet scalar leptoquarks $S_1$ and $S_3$. By assuming a flavor structure for the leptoquark couplings dictated by a minimally broken $U(2)^5$ flavor symmetry we can make a sharp connection between these two classes of observables. We find that the bound on $\mathcal{B}(K^+ \rightarrow π^+ νν)$ from NA62 puts already some tension in the model, while the present limits on $\mathcal{B}(K_L \rightarrow μ^+ μ^-)$ and $μ\to e$ conversion in nuclei can be saturated. Relaxing instead the flavor assumption we study what values for $\mathcal{B}(K^+ \rightarrowπ^+ νν)$, as well as for $\mathcal{B}(K_L \rightarrowπ^0 νν)$ and $\mathcal{B}(K_{L,S} \rightarrowμ^+ μ^-)$, are viable compatibly with all other phenomenological constraints.

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arXiv2021

Matching scalar leptoquarks to the SMEFT at one loop

In this paper we present the complete one-loop matching conditions, up to dimension-six operators of the Standard Model effective field theory, resulting by integrating out the two scalar leptoquarks $S_{1}$ and $S_{3}$. This allows a phenomenological study of low-energy constraints on this model at one-loop accuracy, which will be the focus of a subsequent work. Furthermore, it provides a rich comparison for functional and computational methods for one-loop matching, that are being developed. As a corollary result, we derive a complete set of dimension-six operators independent under integration by parts, but not under equations of motions, called Green's basis, as well as the complete reduction formulae from this set to the Warsaw basis.

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arXiv2021

A fully differential SMEFT analysis of the golden channel using the method of moments

The Method of Moments is a powerful framework to disentangle the relative contributions of amplitudes of a specific process to its various phase space regions. We apply this method to carry out a fully differential analysis of the Higgs decay channel $h \to 4\ell$ and constrain gauge-Higgs coupling modifications parametrised by dimension-six effective operators. We find that this analysis approach provides very good constraints and minimises degeneracies in the parameter space of the effective theory. By combining the decay $h \to 4\ell$ with Higgs-associated production processes, $Wh$ and $Zh$, we obtain the strongest reported bounds on anomalous gauge-Higgs couplings.

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arXiv2020

Low-energy phenomenology of scalar leptoquarks at one-loop accuracy

We perform a complete study of the low-energy phenomenology of $S_1$ and $S_3$ lepto-quarks, aimed at addressing the observed deviations in $B$-meson decays and the muon magnetic dipole moment. Leptoquark contributions to observables are computed at one-loop accuracy in an effective field theory approach, using the recently published complete one-loop matching of these leptoquarks to the Standard Model effective field theory. We present several scenarios, discussing in each case the preferred parameter space and the most relevant observables.

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arXiv2020

Singlet night in Feynman-ville: one-loop matching of a real scalar

A complete one-loop matching calculation for real singlet scalar extensions of the Standard Model to the Standard Model effective field theory (SMEFT) of dimension-six operators is presented. We compare our analytic results obtained by using Feynman diagrams to the expressions derived in the literature by a combination of the universal one-loop effective action (UOLEA) approach and Feynman calculus. After identifying contributions that have been overlooked in the existing calculations, we find that the pure diagrammatic approach and the mixed method lead to identical results. We highlight some of the subtleties involved in computing one-loop matching corrections in SMEFT.

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arXiv2018

Anatomy of $b \to c \, τ\, ν$ anomalies

In recent times, one of the strongest hints of Physics Beyond the Standard Model (BSM) has been the anomaly in the ratios $R_D$ and $R_{D^\ast}$ measured in the charged current decays of $B$-mesons. In this work, we perform a comprehensive analysis of these decay modes, first in a model independent way and subsequently, in the context of composite Higgs models. We discuss in depth as to how linearly realised $\rm SU(2)_L \times U(1)_Y$ symmetry imposes severe constraint on the various scenarios because of correlations with other $ΔF =1$ processes and $Z\,τ\,τ$ and $Z\,ν\,ν$ couplings. In the composite Higgs paradigm with partial compositeness, we show that, irrespective of the flavour structure of the composite sector, constraints from $ΔF =2$ processes bring the compositeness scale down to $\sim 650$ GeV which is in tension with electroweak precision observables. In the presence of composite leptoquarks, the situation improves only marginally (a factor of $\sqrt{2}$ in the compositeness scale), thus making the new states soon discoverable by direct searches at the LHC. We also comment on the possible explanation of the $R_{K,K^*}$ anomalies within the composite Higgs framework.

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arXiv2017

FCNC decays of SM fermions into a dark photon

We analyze a new class of FCNC processes, the $f \to f^{\prime} \, \barγ$ decays of a fermion $f$ into a lighter (same-charge) fermion $f^{\prime}$ plus a {\it massless} neutral vector boson, a {\it dark photon} $\barγ$. A massless dark photon does not interact at tree level with observable fields, and the $f \!\to\! f^{\prime} \, \barγ$ decay presents a characteristic signature where the final fermion $f^{\prime}$ is balanced by a {\it massless invisible} system. Models recently proposed to explain the exponential spread in the standard-model Yukawa couplings can indeed foresee an extra unbroken {\it dark} $U(1)$ gauge group, and the possibility to couple on-shell dark photons to standard-model fermions via one-loop magnetic-dipole kind of FCNC interactions. The latter are suppressed by the characteristic scale related to the mass of heavy messengers, connecting the standard model particles to the dark sector. We compute the corresponding decay rates for the top, bottom, and charm decays ($t\to c\, \barγ,u\, \barγ$, $\;b\to s\, \barγ,d\, \barγ$, and $c\to u \barγ$), and for the charged-lepton decays ($τ\to μ\, \barγ, e\, \barγ$, and $μ\to e \barγ$) in terms of model parameters. We find that large branching ratios for both quark and lepton decays are allowed in case the messenger masses are in the discovery range of the LHC. Implications of these new decay channels at present and future collider experiments are briefly discussed.

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