Search

Two-Higgs-doublet models come with an augmented parameter space which allows them to possibly solve some of the shortcomings of the Standard Model, and opens the window to a plethora of new phenomena to be discovered. The introduction of scalar-mediated tree-level flavour-changing neutral currents may be tackled with the imposition of extra symmetries on the model or, alternatively, by demanding a strict proportionality between the flavour-changing couplings and fermion mass matrices. The latter is the very idea behind the Aligned-Two-Higgs-Doublet Model (A2HDM). The coefficients that govern such proportionality are, in general, complex and, therefore, possible new sources of CP violation, a calling card of this class of models. We present here the results of new state-of-the-art analyses of the A2HDM where, in particular, we ascertain whether current data allows the A2HDM to accommodate extra scalars lighter than the 125 GeV Higgs boson. To this effect, we make use of theoretical constraints, bounds from Higgs searches at the LHC and LEP, electroweak precision observables, and a set of flavour observables, all globally combined within HEPfit, a software with a Bayesian Markov Chain Monte Carlo approach to statistical inference. Focusing on the light-pseudoscalar scenario, we find a region of parameter space compatible with all the constraints we impose., Comment: 5 pages, 1 figure, 1 table, Proceedings of LHCP2024

Experiments have confirmed the presence of a mass gap between the Standard Model and potential New Physics. Consequently, the exploration of effective field theories to detect signals indicative of Physics Beyond the Standard Model is of great interest. In this study, we examine a non-linear realization of the electroweak symmetry breaking, wherein the Higgs is a singlet with independent couplings, and Standard Model fields are additionally coupled to heavy bosonic resonances. We present a next-to-leading-order determination of the oblique $S$ and $T$ parameters. Comparing our predictions with experimental values allows us to impose constraints on resonance masses, requiring them to exceed the TeV scale ($M_R > 2\,$TeV). This finding aligns with our earlier analysis, employing a less generalized approach and the experimental bounds of that time, where we computed these observables., Comment: 6 pages, 2 figures. Talk given at the 42nd International Conference on High Energy Physics - ICHEP2024 (18-24 July 2024, Prague, Czech Republic)

Left-Right Models (LRMs) are one of the most relevant extensions of the Standard Model (SM) of particle physics. They introduce an extended gauge sector and can restore parity (P) or charge conjugation (C) symmetries at high enough energies. These theories can be embedded in other more fundamental ones with larger gauge groups. Consequently, the restoration of the C or P symmetries can be pushed towards higher energy scales compared to the scale of the Spontaneous Symmetry Breaking (SSB) of the LRM gauge group. We study three LRMs with different specific realizations of the scalar sector without imposing any additional discrete symmetry on the theory. We present bounds on the masses of the new gauge bosons using data from the LHC Run 2 and study rare meson decays, discussing the structure of the right-handed quark mixing matrix and the impact of the neutrino and scalar sectors. Collider bounds valid for specific LRM realizations are alleviated bringing New Physics (NP) effects in flavour observables closer to an observable level., Comment: Contribution to the Beyond the Standard Model Session of the 42nd International Conference on High Energy Physics

The Two Higgs Doublet Model (2HDM) is a simple extension of the Standard Model (SM), which provides a rich and very interesting phenomenology. To remove the undesirable flavour-changing neutral currents (FCNCs), an additional $\mathcal Z_2$ symmetry is usually imposed into the 2HDM. However, FCNCs can be avoided in a much more general way by assuming a similar Yukawa structure for the two scalar doublets. But one can circumvent the issue of FCNCs by assuming similar Yukawa structure for the two scalar doublets too. The model with this intriguing feature is termed the Aligned Two Higgs Doublet Model (A2HDM). The phenomenological constraints on the A2HDM are much weaker than the ones on the usual $\mathcal Z_2$ models, opening a broader range of possible scenarios. Moreover, the A2HDM also provides a generic framework to study, as particular cases, the different varieties of $\mathcal Z_2$-symmetric 2HDMs. Here, we illustrate a global fit of the A2HDM using the package HEPfit. We study the possibility of having new scalar particles lighter than the SM Higgs. For this global fit we perform a Bayesian analysis, including stability and perturbativity bounds, flavour and electroweak precision observables, and scalar (and pseudoscalar) searches at LEP and LHC., Comment: Proceeding for ICHEP2024

The super tau-charm facility will provide excellent conditions to perform a high-precision investigation of the tau-lepton properties: very high statistics, controllable systematics and low backgrounds. An overview of the broad physics program that could be addressed at this facility is presented., Comment: Invited contribution to FTCF2024. 14 pages, 2 figures

While the third run of the Large Hadron Collider (LHC) is ongoing, the underlying theory that extends the Standard Model remains so far unknown. Left-Right Models (LRMs) introduce a new gauge sector, and can restore parity symmetry at high enough energies. If LRMs are indeed realized in nature, the mediators of the new weak force can be searched for in colliders via their direct production. We recast existing experimental limits from the LHC Run 2 and derive generic bounds on the masses of the heavy LRM gauge bosons. As a novelty, we discuss the dependence of the $W_R$ and $Z_R$ total decay width on the LRM scalar content, obtaining model-independent bounds within the specific realizations of the LRM scalar sectors analysed here. These bounds avoid the need to detail the spectrum of the scalar sector, and apply in the general case where no discrete symmetry is enforced. Moreover, we emphasize the impact on the $W_R$ production at LHC of general textures of the right-handed quark mixing matrix without manifest left-right symmetry. We find that the $W_R$ and $Z_R$ masses are constrained to lie above $2$ TeV and $4$ TeV, respectively., Comment: Contribution to the 2024 Electroweak session of the 58th Rencontres de Moriond

Folklore in complexity theory suspects that circuit lower bounds against $\mathbf{NC}^1$ or $\mathbf{P}/\operatorname{poly}$, currently out of reach, are a necessary step towards proving strong proof complexity lower bounds for systems like Frege or Extended Frege. Establishing such a connection formally, however, is already daunting, as it would imply the breakthrough separation $\mathbf{NEXP} \not\subseteq \mathbf{P}/\operatorname{poly}$, as recently observed by Pich and Santhanam (2023). We show such a connection conditionally for the Implicit Extended Frege proof system ($\mathsf{iEF}$) introduced by Kraj\'i\v{c}ek (The Journal of Symbolic Logic, 2004), capable of formalizing most of contemporary complexity theory. In particular, we show that if $\mathsf{iEF}$ proves efficiently the standard derandomization assumption that a concrete Boolean function is hard on average for subexponential-size circuits, then any superpolynomial lower bound on the length of $\mathsf{iEF}$ proofs implies $\#\mathbf{P} \not\subseteq \mathbf{FP}/\operatorname{poly}$ (which would in turn imply, for example, $\mathbf{PSPACE} \not\subseteq \mathbf{P}/\operatorname{poly}$). Our proof exploits the formalization inside $\mathsf{iEF}$ of the soundness of the sum-check protocol of Lund, Fortnow, Karloff, and Nisan (Journal of the ACM, 1992). This has consequences for the self-provability of circuit upper bounds in $\mathsf{iEF}$. Interestingly, further improving our result seems to require progress in constructing interactive proof systems with more efficient provers., Comment: A conference version of this work is accepted to the 51st EATCS International Colloquium on Automata, Languages and Programming (ICALP 2024)

We prove that if conditions I-II (below) hold and there is a sequence of Boolean functions $f_n$ hard to approximate by p-size circuits such that p-size circuit lower bounds for $f_n$ do not have p-size proofs in Extended Frege system EF, then $P\ne NP$. I. $S^1_2$ proves that a concrete function in ${\sf E}$ is hard to approximate by subexponential-size circuits. II. [Learning from $\neg\exists$ OWF.] $S^1_2$ proves that a p-time reduction transforms circuits breaking one-way functions to p-size circuits learning p-size circuits over the uniform distribution, with membership queries. Here, $S^1_2$ is Buss's theory of bounded arithmetic formalizing p-time reasoning. Further, we show that any of the following assumptions implies that $P\ne NP$, if EF is not p-bounded: 1. [Feasible anticheckers.] $S^1_2$ proves that a p-time function generates anticheckers for SAT. 2. [Witnessing $NP\not\subseteq P/poly$.] $S^1_2$ proves that a p-time function witnesses an error of each p-size circuit which fails to solve SAT. 3. [OWF from $NP\not\subseteq P/poly$ $\&$ hardness of ${\sf E}$.] Condition I holds and $S^1_2$ proves that a p-time reduction transforms circuits breaking one-way functions to p-size circuits computing SAT. The results generalize to stronger theories and proof systems., Comment: arXiv admin note: text overlap with arXiv:2111.10626

Though the Standard Model (SM) provides a very elegant description of the interactions among fundamental particles, there are ample evidences suggesting that new physics is needed. In particular, extending the scalar sector has enough motivation from vacuum stability, electroweak phase transition and various other sectors. Among different such extensions, the two-Higgs-doublet model (THDM) is the simplest one that preserves the electroweak $\rho$ parameter. Flavour-changing neutral currents (FCNC) are usually avoided by implementing additional discrete symmetries, but this type of models are subject to severe phenomenological constraints. In the more general framework of the aligned THDM (ATHDM) tree-level FCNCs are avoided by choosing the same flavour structure for the Yukawa couplings of the two scalar doublets, which results in weaker phenomenological constraints. Here, we present a global fit of the ATHDM, using the package HEPfit that performs a bayesian analysis on the parameter-space of this model with the help of stability and perturbativity bounds, experimental data for various flavour and electroweak precision observables, and constraints from Higgs searches at the LHC. This global fit has been performed assuming that all additional scalars are heavier than the SM Higgs and that there are no extra sources of CP violation beyond the CKM phase., Comment: 6 pages, Contribution to EPS-HEP2023 (21-25 August, 2023, Hamburg, Germany)

Kaon physics is at a turning point -- while the rare-kaon experiments NA62 and KOTO are in full swing, the end of their lifetime is approaching and the future experimental landscape needs to be defined. With HIKE, KOTO-II and LHCb-Phase-II on the table and under scrutiny, it is a very good moment in time to take stock and contemplate about the opportunities these experiments and theoretical developments provide for particle physics in the coming decade and beyond. This paper provides a compact summary of talks and discussions from the Kaons@CERN 2023 workshop., Comment: 55 pages, Summary of Kaons@CERN 23 workshop, references updated, typos fixed, version as published in EPJC

It has been confirmed experimentally the existence of a mass gap between Standard Model (SM) and eventual Beyond Standard Model (BSM) fields. Therefore, the use of effective approaches to search for fingerprints of New Physics is very appealing. A non-linear realizations of the Electroweak Symmetry Breaking is considered here, where the Higgs is a singlet with free couplings and the SM fields are also coupled to bosonic heavy resonances. A one-loop-level calculation of the oblique S and T parameters is presented here. This analysis allows us to constrain resonance masses to be above the TeV scale, $M_R\!>\! 3\,$TeV, in good agreement with our previous determinations, where these observables were computed with a more simplified Lagrangian., Comment: Talk given at the 26th International Conference in Quantum Chromodynamics (QCD 23), 10-14 July 2023, Montpellier (France). 7 pages, 3 figures

While the third run of the Large Hadron Collider (LHC) is ongoing, the underlying theory that extends the Standard Model remains so far unknown. Left-Right Models (LRMs) introduce a new gauge sector, and can restore parity symmetry at high enough energies. If LRMs are indeed realized in nature, the mediators of the new weak force can be searched for in colliders via their direct production. We recast existing experimental bounds from LHC Run 2 on the heavy LRM gauge boson masses. As a novelty, we discuss the effect of the LRM scalar content on the total width of the new gauge bosons, obtaining model-independent bounds within the specific realizations of the LRM scalar sectors analysed here. These bounds avoid the need to detail the spectrum of the scalar sector, and apply in the general case where no discrete symmetry is enforced. Moreover, we emphasize the effect of the structure of the quark right-handed mixing matrix on the charged LRM gauge boson production at LHC. We find that $W_R$ and $Z_R$ masses are constrained to lie above $2$ TeV and $4$ TeV, respectively.

We consider electroweak (EW) gauge boson corrections to the masses of pseudoscalar mesons to next to leading order (NLO) in $\alpha_s$ and $1/N_C$. The pion mass shift induced by the $Z$-boson is shown to be $m_{\pi^\pm}-m_{\pi^0} = -0.00201(12)$ MeV. While being small compared to the electromagnetic mass shift, the prediction lies about a factor of $\sim 4$ above the precision of the current experimental measurement, and a factor $O(10)$ below the precision of current lattice calculations. This motivates future implementations of these EW gauge boson effects on the lattice. Finally, we consider BSM contributions to the pion mass difference., Comment: 6 pages, 1 figure

An updated global fit on the parameter-space of the Aligned Two-Higgs-Doublet model has been performed with the help of the open-source package HEPfit, assuming the Standard-Model Higgs to be the lightest scalar. No new sources of CP violation, other than the phase in the CKM matrix of the Standard Model, have been considered. A similar global fit was previously performed in Ref. [JHEP 05 (2021) 005] with a slightly different set of parameters. Our updated fit incorporates improved analyses of the theoretical constraints required for perturbative unitarity and boundedness of the scalar potential from below, additional flavour observables and updated data on direct searches of heavy scalars at the LHC, Higgs signal strengths and electroweak precision observables. Although not included in the main fit, the implications of the CDF measurement of the $W^\pm$ mass are also discussed., Comment: 38 pages, 15 figures

Urgent theoretical progress is needed in order to provide an estimate in the Standard Model of the recent measurement by LHCb of direct CP violation in charm-meson two-body decays. Rescattering effects must be taken into account for a meaningful theoretical description of the amplitudes involved in such category of observables, as signaled by the presence of large strong phases. We discuss the computation of the latter effects based on a two-channel coupled dispersion relation, which exploits isospin-zero phase-shifts and inelasticity parameterizations of data coming from the rescattering processes $ \pi \pi \to \pi \pi $, $ \pi K \to \pi K $, and $ \pi \pi \to K \overline{K} $. The determination of the subtraction constants of the dispersive integrals relies on the leading contributions to the transition amplitudes from the $ 1/N_C $ counting, where $N_C$ is the number of QCD colours. Furthermore, we use the measured values of the branching ratios to help in selecting the non-perturbative inputs in the isospin limit, from which we predict values for the CP asymmetries. We find that the predicted level of CP violation is much below the experimental value.

Three different approaches to precisely describe the Adler function in the Euclidean regime at around $2\, \mathrm{GeVs}$ are available: dispersion relations based on the hadronic production data in $e^+e^-$ annihilation, lattice simulations and perturbative QCD (pQCD). We make a comprehensive study of the perturbative approach, supplemented with the leading power corrections in the operator product expansion. All known contributions are included, with a careful assessment of uncertainties. The pQCD predictions are compared with the Adler functions extracted from $\Delta\alpha^{\mathrm{had}}_{\mathrm{QED}}(Q^2)$, using both the DHMZ compilation of $e^+e^-$ data and published lattice results. Taking as input the FLAG value of $\alpha_s$, the pQCD Adler function turns out to be in good agreement with the lattice data, while the dispersive results lie systematically below them. Finally, we explore the sensitivity to $\alpha_s$ of the direct comparison between the data-driven, lattice and QCD Euclidean Adler functions. The precision with which the renormalisation group equation can be tested is also evaluated., Comment: 56 pages, 22 figures, 14 tables. Published version

We use the approximation method of Razborov to analyze the locality barrier which arose from the investigation of the hardness magnification approach to complexity lower bounds. Adapting a limitation of the approximation method obtained by Razborov, we show that in many cases it is not possible to combine the approximation method with typical (localizable) hardness magnification theorems to derive strong circuit lower bounds. In particular, one cannot use the approximation method to derive an extremely strong constant-depth circuit lower bound and then magnify it to an $NC^1$ lower bound for an explicit function. To prove this we show that lower bounds obtained by the approximation method are in many cases localizable in the sense that they imply lower bounds for circuits which are allowed to use arbitrarily powerful oracles with small fan-in.

Using the spectral functions measured in $\tau$ decays, we investigate the actual numerical impact of duality violations on the extraction of the strong coupling. These effects are tiny in the standard $\alpha_s(m_\tau^2)$ determinations from integrated distributions of the hadronic spectrum with pinched weights, or from the total $\tau$ hadronic width. The pinched-weight factors suppress very efficiently the violations of duality, making their numerical effects negligible in comparison with the larger perturbative uncertainties. However, combined fits of $\alpha_s$ and duality-violation parameters, performed with non-protected weights, are subject to large systematic errors associated with the assumed modelling of duality-violation effects. These uncertainties have not been taken into account in the published analyses, based on specific models of quark-hadron duality., Comment: 39 pages, 8 figures. References added. Published version

We consider a simple extension of the electroweak theory, incorporating one $SU(2)_L$ doublet of colour-octet scalars with Yukawa couplings satisfying the principle of minimal flavour violation. Using the HEPfit package, we perform a global fit to the available data, including all relevant theoretical constraints, and extract the current bounds on the model parameters. We also calculate the contributions of the additional coloured scalars to the electric dipole moment of the neutron and set limits on its parameter space using the current experimental information. Finally, we study the effect that the last measurement of the $W$-boson mass has in our fit and show how the colour-octet scalar extension struggles to accommodate the new measurement., Comment: Contribution to the 2022 Electroweak session of the 56th Rencontres de Moriond