Alan S. Cornell, Aldo Deandrea, Naveen Gaur, Hideo Itoh, Michael Klasen, Yasuhiro Okada
Many extensions of the Standard Model (SM) of particle physics predict the existence of charged Higgs bosons with substantial couplings to SM particles, which would render them observable both directly at the LHC and indirectly at B-factories. For example, the charged Higgs boson couplings to fermions in two doublet Higgs models of type II, are proportional to the ratio of the two Higgs doublet vacuum expectation values (tan(beta)) and fermionic mass factors and could thus be substantial at large tan(beta) and/or for heavy fermions. In this work we perform a model-independent study of the charged Higgs boson couplings at the LHC and at B-factories for large values of tan(beta). We have shown that at high luminosity it is possible to measure the couplings of a charged Higgs boson to the third generation of quarks up to an accuracy of 10%. We further argue that by combining the possible measurements of the LHC and the B-factories, it is possible to perform a universality test of charged Higgs boson couplings to quarks.
Giacomo Cacciapaglia, Aldo Deandrea, Jeremie Llodra-Perez
We study the unique 6 dimensional orbifold with chiral fermions where a stable dark matter candidate is present due to Lorentz invariance on the orbifold, with no additional discrete symmetries imposed by hand. We propose a model of Universal Extra Dimensions where a scalar photon of few hundred GeV is a good candidate for dark matter. The spectrum of the model is characteristic of the geometry, and it has clear distinctive features compared to previous models of Kaluza-Klein dark matter. The 5 dimensional limit of this model is the minimal model of natural Kaluza-Klein dark matter. Notwithstanding the low mass range preferred by cosmology, the model will be a challenge for the LHC due to the relatively small splitting between the states in the same KK level.
Giacomo Cacciapaglia, Aldo Deandrea, Naveen Gaur, Daisuke Harada, Yasuhiro Okada, Luca Panizzi
We consider the phenomenology at the Large Hadron Collider of new heavy vector-like quarks which couple mainly to the third generation quarks via Yukawa interactions, with special emphasis on non-standard doublet representations which are less constrained from present data. We also discuss in detail the flavour limits at tree level and loop level and implications of a generalised CKM mixing matrix to these cases.
A. S. Cornell, Aldo Deandrea, Lu-Xin Liu, Ahmad Tarhini
We discuss a five-dimensional Minimal Supersymmetric Standard Model compactified on a $S^1/Z_2$ orbifold, looking at, in particular, the one-loop evolution equations of the Yukawa couplings for the quark sector and various flavor observables. Different possibilities for the matter fields are discussed, that is, where they are in the bulk or localised to the brane. The two possibilities give rise to quite different behaviours. By studying the implications of the evolution with the renormalisation group of the Yukawa couplings and of the flavor observables we find that, for a theory that is valid up to the unification scale, the case where fields are localised to the brane, with a large $\tanβ$, would be more easily distinguishable from other scenarios.
Alexandre Arbey, Giacomo Cacciapaglia, Aldo Deandrea, Bogna Kubik
The real projective plane is a compact, non-orientable orbifold of Euler characteristic 1 without boundaries, which can be described as a twisted Klein bottle. We shortly review the motivations for choosing such a geometry among all possible two-dimensional orbifolds, while the main part of the study will be devoted to dark matter study and limits in Universal Extra Dimensional (UED) models based on this peculiar geometry. In the following we consider such a UED construction based on the direct product of the real projective plane with the standard four-dimensional Minkowski space-time and discuss its relevance as a model of a weakly interacting Dark Matter candidate. One important difference with other typical UED models is the origin of the symmetry leading to the stability of the dark matter particle. This symmetry in our case is a remnant of the six-dimensional Minkowski space-time symmetry partially broken by the compactification. Another important difference is the very small mass splitting between the particles of a given Kaluza-Klein tier, which gives a very important role to co-annihilation effects. Finally the role of higher Kaluza-Klein tiers is also important and is discussed together with a detailed numerical description of the influence of the resonances.
Giacomo Cacciapaglia, Aldo Deandrea, Naveen Gaur, Daisuke Harada, Yasuhiro Okada, Luca Panizzi
The existence of new vector-like quarks is often predicted by models of new physics beyond the Standard Model, and the development of discovery strategies at colliders is the object of an intense effort from the high-energy community. Our analysis aims at identifying the constraints on and peculiar signatures of simplified scenarios containing \textit{two} vector-like quark doublets mixing with \textit{any} of the SM quark generations. This scenario is a necessary ingredient of a broad class of theoretically motivated constructions. We focus on the two charge $2/3$ states $t_{1,2}^\prime$ that, due to their peculiar mixing patterns, feature new production and decay modes that are not searched for at the LHC: single production of the heavier state can dominate over the light one, while pair production via electroweak interactions overcomes the QCD one for masses at the TeV scale.
Alan S. Cornell, Aldo Deandrea, Thomas Flacke, Benjamin Fuks, Lara Mason
We investigate the phenomenology of a scalar top-philic dark matter candidate when adding a dimension-five contact interaction term, as motivated by possible underlying extensions of the Standard Model such as composite Higgs models. We show that the presence of contact interactions can have a major impact on the dark matter relic density as well as on its direct and indirect detection prospects, while the collider phenomenology of the model is unaffected. This underlines the complementarity of collider and cosmological constraints on dark matter models.
Ammar Abdalgabar, Alan S. Cornell, Aldo Deandrea, Moritz McGarrie
Even if the unification and supersymmetry breaking scales are around $10^6$ to $10^{9}$ TeV, a large $A_t$ coupling may be entirely generated at low energies through RGE evolution in the 5D MSSM. Independent of the precise details of supersymmetry breaking, we take advantage of power law running in five dimensions and a compactification scale in the $10-10^3$ TeV range to show how the gluino mass may drive a large enough $A_t$ to achieve the required $125.5$ GeV Higgs mass. This also allows for sub-TeV stops, possibly observable at the LHC, and preserving GUT unification, thereby resulting in improved naturalness properties with respect to the four dimensional MSSM. The results apply also to models of "split families" in which the first and second generation matter fields are in the bulk and the third is on the boundary, which may assist in the generation of light stops whilst satisfying collider constraints on the first two generations of squarks.
Aldo Deandrea, Pierre Hosteins, Micaela Oertel, Julien Welzel
We discuss in detail a five-dimensional Minimal Supersymmetric Standard Model compactified on $S^1/Z_2$ extended by the effective Majorana neutrino mass operator. We study the evolution of neutrino masses and mixings. Masses and angles, in particular the atmospheric mixing angle $θ_{23}$, can be significantly lowered at high energies with respect to their value at low energy.
Ammar Abdalgabar, A. S. Cornell, Aldo Deandrea, Ahmad Tarhini
The evolution equations of the Yukawa couplings and quark mixings are derived for the one-loop renormalization group equations in the two Universal Extra Dimension Models (UED), that is six-dimensional models, compactified in different possible ways to yield standard four space-time dimension. Different possibilities for the matter fields are discussed, such as the case of bulk propagating or localised brane fields. We discuss in both cases the evolution of the Yukawa couplings, the Jarlskog parameter and the CKM matrix elements, and we find that, for both scenarios, as we run up to the unification scale, significant renormalization group corrections are present. We also discuss the results of different observables of the five-dimensional UED model in comparison with these six-dimensional models and the model dependence of the results.
David Andriot, Giacomo Cacciapaglia, Aldo Deandrea, Nicolas Deutschmann, Dimitrios Tsimpis
We present a first study of the field spectrum on a class of negatively-curved compact spaces: nilmanifolds or twisted tori. This is a case where analytical results can be obtained, allowing to check numerical methods. We focus on the Kaluza-Klein expansion of a scalar field. The results are then applied to a toy model where a natural Dark Matter candidate arises as a stable massive state of the bulk scalar.
David Andriot, Alan Cornell, Aldo Deandrea, Fabio Dogliotti, Dimitrios Tsimpis
We present a method to obtain a scalar potential at tree level from a pure gauge theory on nilmanifolds, a class of negatively-curved compact spaces, and discuss the spontaneous symmetry breaking mechanism induced in the residual Minkowski space after compactification at low energy. We show that the scalar potential is completely determined by the gauge symmetries and the geometry of the compact manifold. In order to allow for simple analytic calculations we consider three extra space dimensions as the minimal example of a nilmanifold, therefore considering a pure Yang-Mills theory in seven dimensions.
Giacomo Cacciapaglia, Roberto Chierici, Aldo Deandrea, Luca Panizzi, Stèphane Perries, Silvano Tosi
We explore the four top signal ttbar ttbar at the 7 TeV Large Hadron Collider as a probe of physics beyond the standard model. Enhancement of the corresponding cross-section with respect to the Standard Model value can probe the electroweak symmetry breaking sector or test extra dimensional models with heavy Kaluza-Klein gluons and quarks. We perform a detailed analysis including background and detector simulation in the specific case of a universal extra-dimensional model with two extra dimensions compactified using the geometry of the real projective plane. For masses around 600 GeV, a discovery is possible for an effective cross section above 210 fb (36 fb) for 1/fb (10/fb) of integrated luminosity. This implies a branching ratio in tops of the (1,1) heavy photon above 13% (5%). Furthermore, the 4-top signal from the (2,0) and (0,2) tiers can be discovered with an integrated luminosity of 3.5/fb. The results of our simulation can be easily adapted to other models since the background processes are identical. Concerning the signal, typical production mechanisms for the ttbar ttbar signal are similar even if cross-section values may vary considerably depending on the model and the spectrum of the new particles.
Giacomo Cacciapaglia, Aldo Deandrea, John Ellis, Jad Marrouche, Luca Panizzi
We consider the performance of the ATLAS and CMS searches for events with missing transverse energy, which were originally motivated by supersymmetry, in constraining extensions of the Standard Model based on extra dimensions, in which the mass differences between recurrences at the same level are generically smaller than the mass hierarchies in typical supersymmetric models. We consider first a toy model with pair-production of a single vector-like quark U1 decaying into a spin-zero stable particle A1 and jet, exploring the sensitivity of the CMS alphaT and ATLAS meff analysis to U1 mass and the U1-A1 mass difference. For this purpose we use versions of the Delphes generic detector simulation with CMS and ATLAS cards, which have been shown to reproduce the published results of CMS and ATLAS searches for supersymmetry. We then explore the sensitivity of these searches to a specific model with two universal extra dimensions, whose signal is dominated by the pair production of quark recurrences, including searches with leptons. We find that the LHC searches have greater sensitivity to this more realistic model, due partly to the contributions of signatures with leptons, and partly to events with large missing transverse energy generated by the decays of higher-level Kaluza-Klein recurrences. We find that the CMS alphaT analysis with ~5/fb of data at 7 TeV excludes a recurrence scale of 600 GeV at a confidence level above 99%, increasing to 99.9% when combined with the CMS single-lepton search, whereas a recurrence scale of 700 GeV is disfavoured at the 72% confidence level.
Giacomo Cacciapaglia, Aldo Deandrea, Christian Verollet
Asymptotic grand unification is an alternative framework to traditional quantitative unification, as the renormalisation flow leads towards an ultra-violet safe fixed point. Phenomenologically, 5-dimensional realisations permit new particles with masses as low as the TeV scale, well below the usual unification scale. We explore the impact of such models on electroweak precision observables, focusing on a minimal SU(5) template for concreteness. We show that current measurements are not sensitive to this class of models. Future colliders, such as CEPC and FCC-ee, can push the 95% limit on the Kaluza-Klein mass up to 2 and 4 TeV, respectively, beyond the direct reach of the LHC programme.
Anna Chrysostomou, Alan S. Cornell, Aldo Deandrea, Hajar Noshad, Seong Chan Park
Rich physics can be divined from charged black holes subjected to extremal conditions. When applied in conjunction with principles like Weak Cosmic Censorship, this naturally leads to constraints on the mass and charge of the black hole. However, more nuanced principles such as the Weak Gravity Conjecture (WGC) and the recently proposed Festina-Lente (FL) bound can provide, respectively, upper and lower bounds on elementary charged particles. In this study, we examine the quasinormal modes (QNMs) exhibited by a massive scalar test field carrying an electric charge, oscillating in the outer region of the black hole. These modes are subjected to the constraints imposed by the FL and WGC bounds. Our analysis provides insight into the behaviour of QNMs, particularly in regions that approach the extremal conditions of the black hole. Notably, in these regimes, the stability of the modes becomes precarious, particularly in the presence of a positive cosmological constant. The implications of our findings are far-reaching and significant. They extend from safeguarding the principles of cosmic censorship to addressing the structural stability of the black hole's interior. Our semi-classical analysis presents compelling evidence suggesting that Strong Cosmic Censorship may be violated for black holes that are in close proximity to extremality within the context of Reissner-Nordström-de Sitter (RNdS) geometries.
Giacomo Cacciapaglia, Aldo Deandrea, Shahram Vatani
We propose a new family structure for the Standard Model fermions, where the muon is assigned to the third family, taking the placeholder from the tau lepton. This reassignment, which is a mere choice of convention in the Standard Model, becomes physically meaningful in the presence of new physics assuming a direct link between quarks and leptons. In fact, when quark and leptons are coupled by new interactions, the choice of which lepton is assigned to a particular quark generation brings physical consequences, revealing potentially meaningful patterns in the masses and mixings, while pointing to precise and testable predictions for experiments.
A. S. Cornell, Aldo Deandrea, Lu-Xin Liu, Ahmad Tarhini
We review the Universal Extra-Dimensional Model compactified on a S1/Z2 orbifold, and the renormalisation group evolution of quark and lepton masses, mixing angles and phases both in the UED extension of the Standard Model and of the Minimal Supersymmetric Standard Model. We consider two typical scenarios: all matter fields propagating in the bulk, and matter fields constrained to the brane. The resulting renormalisation group evolution equations in these scenarios are compared with the existing results in the literature, together with their implications.
Giacomo Cacciapaglia, Alan S. Cornell, Corentin Cot, Aldo Deandrea
We present a minimal model of asymptotic grand unification based on an $SU(5)$ gauge theory in a compact $S^1/(\mathbb{Z}_2 \times \mathbb{Z}'_2)$ orbifold. The gauge couplings run to a unified fixed point in the UV, without supersymmetry. By construction, fermions are embedded in different $SU(5)$ bulk fields. As a consequence, baryon number is conserved, thus preventing proton decay, and the lightest Kaluza-Klein tier consists of new states that cannot decay into standard model ones. We show that the Yukawa couplings can be either in the bulk or localized, and run to an asymptotically free fixed point in the UV. The lightest massive state can play the role of Dark Matter, produced via baryogenesis, for a Kaluza-Klein mass of about $2.4$ TeV.
Giacomo Cacciapaglia, Aldo Deandrea, Guillaume Drieu La Rochelle, Jean-Baptiste Flament
We consider the Higgs boson decay processes and its production, and provide a parameterisation tailored for testing models of new physics beyond the Standard Model. We also compare our formalism to other existing parameterisations based on scaling factors in front of the couplings and to effective Lagrangian approaches. Different formalisms allow to best address different aspects of the Higgs boson physics. The choice of a particular parameterisation depends on a non-obvious balance of quantity and quality of the available experimental data, envisaged purpose for the parameterisation and degree of model independence, importance of the radiative corrections, scale at which new particles appear explicitly in the physical spectrum. At present only simple parameterisations with a limited number of fit parameters can be performed, but this situation will improve with the forthcoming experimental LHC data. Detailed fits can only be performed by the experimental collaborations at present, as the full information on the different decay modes is not completely available in the public domain. It is therefore important that different approaches are considered and that the most detailed information is made available to allow testing the different aspects of the Higgs boson physics and the possible hints beyond the Standard Model.