arXiv subjects

Enrico Maria Sessolo

Publications and source records attributed to Enrico Maria Sessolo.

At least 19 recordsLinked to original sources

arXiv2026

GUT-induced FCC signatures of the LUX-ZEPLIN event

The recent observation of an event with large recoil energy at LUX-ZEPLIN has found a possible explanation in terms of the inelastic scattering of a pseudo-Dirac particle like the Higgsino of the MSSM. For pseudo-Dirac dark matter, the mass splitting $δm$ is correlated with the mass of some heavier states. While rough dimensional considerations seem to indicate mass ranges of the heavy particles hopelessly out of reach even at future colliders, we point out that this is not the case in GUT-induced scenarios. Working with a specific model based on SU(6), we show that the experimentally favored $δm$ implies the presence of a $Z'$ gauge boson with a mass in the 10s of TeV. We derive the predicted $Z'$ signal in the dilepton channel and we confront it with the sensitivity of the FCC-$hh$ to $Z'$ resonances. We show that the $Z'$ falls squarely in reach of the early discovery potential of the FCC-$hh$.

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arXiv2026

Quantum gravity contributions to the gauge and Yukawa couplings in proper time flow

We derive quantum gravity contributions to the beta functions of the gauge and Yukawa couplings of a matter theory using the Schwinger proper-time flow equation. Working in the Einstein-Hilbert truncation, we investigate the gauge-fixing and regulator dependence of the corresponding renormalization group equations. We quantify the sensitivity of our results on unphysical parameters by evaluating the gravitational correction to the running matter couplings at the interactive fixed point of gravity and we compare our findings with existing determinations in alternative schemes. We finally confront the derived contributions with the typical size they should assume to generate observable low-scale predictions in the Standard Model and in several scenarios of new physics.

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arXiv2026

Qubit entanglement from forward scattering

In the context of entanglement in relativistic $2\to 2$ scattering described by a perturbative $S$-matrix, we derive analytically the concurrence for a mixed final state of two qubits corresponding to a discrete quantum number of the scattered particles. The qubit density matrix is obtained by tracing the momentum degrees of freedom out of the full density matrix of the scattered system. Given an initial product state, the derived concurrence depends at the leading order on the real part of the inelastic forward amplitude and the initial state only. We also point out that the real part of the forward amplitude provides a subleading correction to the linearized entropy, reducing it by an amount that, for a computational-basis state, is equivalent to the relative entropy of coherence. We illustrate our findings with two examples of phenomenological interest: high-energy scattering of two scalar fields in the two-Higgs doublet model, and high-energy electron-positron annihilation.

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arXiv2025

Stabilizing dark matter with quantum scale symmetry

In the context of gauge-Yukawa theories with trans-Planckian asymptotic safety, quantum scale symmetry can prevent the appearance in the Lagrangian of couplings that would otherwise be allowed by the gauge symmetry. Such couplings correspond to irrelevant Gaussian fixed points of the renormalization group flow. Their absence in the theory implies that different sectors of the gauge-Yukawa theory are secluded from one another, in similar fashion to the effects of a global or a discrete symmetry. As an example, we impose the trans-Planckian scale symmetry on a model of Grand Unification based on the gauge group SU(6), showing that it leads to the emergence of several fermionic WIMP dark matter candidates whose coupling strengths are entirely predicted by the UV completion.

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arXiv2024

Entanglement in flavored scalar scattering

We investigate quantum entanglement in high-energy $2\to 2$ scalar scattering, where the scalars are characterized by an internal flavor quantum number acting like a qubit. Working at the 1-loop order in perturbation theory, we build the final-state density matrix as a function of the scattering amplitudes connecting the initial to the outgoing state. In this construction, the unitarity of the $S$-matrix is guaranteed at the required order by the optical theorem. We consider the post-scattering entanglement between the momentum and flavor degrees of freedom of the final-state particles, as well as the entanglement of the two-qubit flavor subsystem. In each case we identify the couplings of the scalar potential that can generate, destroy, or transfer entanglement between different bipartite subspaces of the Hilbert space.

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arXiv2023

Naturally small neutrino mass with asymptotic safety and gravitational-wave signatures

We revisit the dynamical generation of an arbitrarily small neutrino Yukawa coupling in the Standard Model with trans-Planckian asymptotic safety and apply the same mechanism to the gauged $B-L$ model. We show that thanks to the presence of additional irrelevant couplings, the described neutrino-mass generation in the $B-L$ model is potentially more in line with existing theoretical calculations in quantum gravity. Interestingly, the model can accommodate, in full naturalness and without extensions, the possibility of purely Dirac, pseudo-Dirac, and Majorana neutrinos with any see-saw scale. We investigate eventual distinctive signatures of these cases in the detection of gravitational waves from first-order phase transitions. We find that, while it is easy to produce a signal observable in new-generation interferometers, its discriminating features are washed out by the strong dependence of the gravitational-wave spectrum on the relevant parameters of the scalar potential.

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arXiv2023

How robust are particle physics predictions in asymptotic safety?

The framework of trans-Planckian asymptotic safety has been shown to generate phenomenological predictions in the Standard Model and in some of its simple new physics extensions. A heuristic approach is often adopted, which bypasses the functional renormalization group by relying on a parametric description of quantum gravity with universal coefficients that are eventually obtained from low-energy observations. Within this approach a few simplifying approximations are typically introduced, including the computation of matter renormalization group equations at 1~loop, an arbitrary definition of the position of the Planck scale at $10^{19}$ GeV, and an instantaneous decoupling of gravitational interactions below the Planck scale. In this work we systematically investigate, both analytically and numerically, the impact of dropping each of those approximations on the predictions for certain particle physics scenarios. In particular we study two extensions of the Standard Model, the gauged $B-L$ model and the leptoquark $S_3$ model, for which we determine a set of irrelevant gauge and Yukawa couplings. In each model, we present numerical and analytical estimates of the uncertainties associated with the predictions from asymptotic safety.

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arXiv2023

Constraints on $Z'$ solutions to the flavor anomalies with trans-Planckian asymptotic safety

Motivated by the flavor anomalies in $b \to s$ transitions, we embed minimal models with a $Z'$ gauge boson, vector-like fermions, and a singlet scalar in the framework of trans-Planckian asymptotic safety. The presence of a fixed point in the renormalization group flow of the models' parameters leads to predictions for the $γ/Z'$ kinetic mixing, the New Physics Yukawa couplings, and the quartic couplings of the scalar potential. We derive the constraint on the kinetic mixing from the most recent high-mass dilepton resonance searches at the LHC, showing that this bound is often inescapable in this framework, unless the U(1) charges conspire to forbid the radiative generation of kinetic mixing. In the latter case, the parameter space consistent with the flavor anomalies can still be probed in depth by direct LHC searches for heavy vector-like quarks and leptons. We derive the current exclusion bounds and projections for future high-luminosity runs.

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arXiv2022

Naturally small Yukawa couplings from trans-Planckian asymptotic safety

In gauge-Yukawa systems embedded in the framework of trans-Planckian asymptotic safety we discuss the dynamical generation of arbitrarily small Yukawa couplings driven by the presence of a non-interactive infrared-attractive fixed point in the renormalization group flow. Additional ultraviolet-attractive fixed points guarantee that the theory remains well defined up to an infinitely high scale. We apply this mechanism to the Yukawa couplings of the Standard Model extended with right-handed neutrinos, finding that asymptotically safe solutions in agreement with the current experimental determination of the masses and mixing angles exist for Dirac neutrinos with normal mass ordering. We generalize the discussion by applying the same mechanism to a new-physics model with sterile-neutrino dark matter, where we generate naturally the feeble Yukawa interaction required to reproduce via freeze-in the correct relic abundance.

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arXiv2022

Simple and statistically sound recommendations for analysing physical theories

Physical theories that depend on many parameters or are tested against data from many different experiments pose unique challenges to statistical inference. Many models in particle physics, astrophysics and cosmology fall into one or both of these categories. These issues are often sidestepped with statistically unsound ad hoc methods, involving intersection of parameter intervals estimated by multiple experiments, and random or grid sampling of model parameters. Whilst these methods are easy to apply, they exhibit pathologies even in low-dimensional parameter spaces, and quickly become problematic to use and interpret in higher dimensions. In this article we give clear guidance for going beyond these procedures, suggesting where possible simple methods for performing statistically sound inference, and recommendations of readily-available software tools and standards that can assist in doing so. Our aim is to provide any physicists lacking comprehensive statistical training with recommendations for reaching correct scientific conclusions, with only a modest increase in analysis burden. Our examples can be reproduced with the code publicly available at https://doi.org/10.5281/zenodo.4322283.

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arXiv2022

Flavour anomalies and the muon $g-2$ from feebly interacting particles

We perform a phenomenological analysis of simplified models of light, feebly interacting particles~(FIPs)that can provide a combined explanation of the anomalies in $b\to s l^+ l ^-$ transitions at LHCb and the anomalous magnetic moment of the muon. Different scenarios are categorised according to the explicit momentum dependence of the FIP coupling to the $b-s$ and $μ-μ$ vector currents and they are subject to several constraints from flavour and precision physics. We show that viable combined solutions to the muon $g-2$ and flavour anomalies exist with the exchange of a vector FIP with mass larger than $4 \,\textrm{GeV}$. Interestingly, the LHC has the potential to probe this region of the parameter space by increasing the precision of the $Z\to 4μ$ cross-section measurement. Conversely, we find that solutions based on the exchange of a lighter vector, in the $m_V < 1\,\textrm{GeV}$ range, are essentially excluded by a combination of $B\to K +\textrm{invisible}$ and $W$-decay precision bounds.

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arXiv2021

Minimal models for $g-2$ and dark matter confront asymptotic safety

We use the framework of asymptotic safety above the Planck scale to constrain the parameter space of simple models of new physics that can accommodate the measured value of the anomalous magnetic moment of the muon and the relic density of dark matter. We couple parametrically to the trans-Planckian quantum physics a set of SU(2)$\times$U(1) invariant extensions of the Standard Model, each comprising an inert scalar field and one pair of colorless fermions that communicate to the muons through Yukawa-type interactions. The presence of an interactive UV fixed point in the system of gauge and Yukawa couplings imposes a set of boundary conditions at the Planck scale, which allow one to derive unique phenomenological predictions in each case and distinguish the different representations of the gauge group from one another. We apply to the models constraints from the $h\to μμ$ signal strength at ATLAS and CMS, direct LHC searches for electroweak production with leptons and missing energy in the final state, and the dark matter relic density. We find that they further restrict the available parameter space.

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arXiv2021

Constraints on charmphilic solutions to the muon g-2 with leptoquarks

We derive constraints from flavor and LHC searches on charmphilic contributions to the muon anomalous magnetic moment with a single leptoquark. Only the scalar leptoquarks $S_1$ and $R_2$ are relevant for the present analysis. We find that for $S_1$ some parameter space remains consistent at $2σ$ with the Brookhaven National Laboratory measurement of the muon $g-2$, under the assumption that the left-type coupling between the muon and the charm quark is a free parameter. The surviving parameter space is, on the other hand, going to be probed in its entirety at the LHC with 300/fb of luminosity or less. All other possibilities are excluded by the LHC dimuon search results in combination with several flavor bounds, which together require one to introduce sizable couplings to the top quark to be evaded.

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arXiv2021

Flavor anomalies from asymptotically safe gravity

We use the framework of asymptotically safe quantum gravity to derive predictions for scalar leptoquark solutions to the $b \to s$ and $b\to c$ flavor anomalies. The presence of an interactive UV fixed point in the system of gauge and Yukawa couplings imposes a set of boundary conditions at the Planck scale, which allows one to determine low-energy values of the leptoquark Yukawa matrix elements. As a consequence, the allowed leptoquark mass range can be significantly narrowed down. We find that a consistent gravity-driven solution to the $b\to s$ anomalies predicts a leptoquark with the mass of 4-7 TeV, entirely within the reach of a future hadron-hadron collider with $\sqrt{s}=100$ TeV. Conversely, in the case of the $b\to c$ anomalies the asymptotically safe gravity framework predicts a leptoquark mass at the edge of the current LHC bounds. Complementary signatures appear in flavor observables, namely the (semi)leptonic decays of B and D mesons and kaons.

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arXiv2020

Flavour anomalies from a split dark sector

We investigate solutions to the flavour anomalies in $B$ decays based on loop diagrams of a "split" dark sector characterised by the simultaneous presence of heavy particles at the TeV scale and light particles around and below the $B$-meson mass scale. We show that viable parameter space exists for solutions based on penguin diagrams with a vector mediator, while minimal constructions relying on box diagrams are in strong tension with the constraints from the LHC, LEP, and the anomalous magnetic moment of the muon. In particular, we highlight a regime where the mediator lies close to the $B$-meson mass, naturally realising a resonance structure and a $q^2$-dependent effective coupling. We perform a full fit to the relevant flavour observables and analyse the constraints from intensity frontier experiments. Besides new measurements of the anomalous magnetic moment of the muon, we find that decays of the $B$ meson, $B_s$-mixing, missing energy searches at Belle-II, and LHC searches for top/bottom partners can robustly test these scenarios in the near future.

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arXiv2019

Testing dark matter with Cherenkov light -- prospects of H.E.S.S. and CTA for exploring minimal supersymmetry

We provide an updated and improved study of the prospects of the H.E.S.S. and Cherenkov Telescope Array (CTA) experiments in testing neutralino dark matter in the Minimal Supersymmetric Standard Model with nine free parameters (p9MSSM). We include all relevant experimental constraints and theoretical developments, in particular the calculation of the Sommerfeld enhancement for both present-day annihilation and the relic abundance. We perform a state-of-the-art analysis of the CTA sensitivity with a log-likelihood test ratio statistics and apply it to a numerical scan of the p9MSSM parameter space focusing on a TeV scale dark matter. We find that, assuming Einasto profile of dark matter halo in the Milky Way, H.E.S.S. has already been able to nearly reach the so-called thermal WIMP value, while CTA will go below it by providing a further improvement of at least an order of magnitude. Both H.E.S.S. and CTA are sensitive to several cases for which direct detection cross section will be below the so-called neutrino floor, with H.E.S.S. being sensitive to most of the wino region, while CTA also covering a large fraction of the ~1 TeV higgsino region. We show that CTA sensitivity will be further improved in the monochromatic photon search mode for both single-component and underabundant dark matter.

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arXiv2019

Implications for New Physics in $b\to s μμ$ transitions after recent measurements by Belle and LHCb

We present a Bayesian analysis of the implications for new physics in semileptonic $b\to s$ transitions after including new measurements of $R_K$ at LHCb and new determinations of $R_{K^*}$ and $R_{K^{*+}}$ at Belle. We perform global fits with 1, 2, 4, and 8 input Wilson coefficients, plus one CKM nuisance parameter to take into account uncertainties that are not factorizable. We infer the 68% and 95.4% credibility regions of the marginalized posterior probability density for all scenarios and perform comparisons of models in pairs by calculating the Bayes factor given a common data set. We then proceed to analyzing a few well known BSM models that can provide a high energy framework for the EFT analysis. These include the exchange of a heavy $Z^{'}$ boson in models with heavy vector-like fermions and a scalar field, and a model with scalar leptoquarks. We provide predictions for the BSM couplings and expected mass values.

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arXiv2019

Global Bayesian Analysis of new physics in $b \to s μμ$ transitions after Moriond-2019

The recent measurement of $R_K$ at LHCb continues to support the hint of violation of lepton flavor universality. We perform a global fit for new physics in semileptonic $b\to s$ transitions using all the relevant data with a Bayesian analysis technique. We include new measurements of $R_K$ at LHCb and new determinations of $R_{K^*}$ and $R_{K^{*+}}$ at Belle. We perform the scan for various NP scenarios and infer the 68\% and 95.4\% credibility regions of the marginalized posterior probability density for all scenarios. We also compare the models in pairs by calculating the Bayes factor given a common data set. A few well-known BSM models are analyzed that can provide a high energy framework for the EFT analysis. These include the exchange of a heavy $Z^{'}$ boson in models with heavy vector-like fermions and a scalar field, and a model with scalar leptoquarks. We provide predictions for the BSM couplings and expected mass values.

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