Hunting electroweakinos at future hadron colliders and direct detection experiments

We analyse the mass reach for electroweakinos at future hadron colliders and their interplay with direct detection experiments. Motivated by the LHC data, we focus on split supersymmetry models with different electroweakino spectra. We find for example that a 100 TeV collider may explore Winos up to ~ 7 TeV in low scale gauge mediation models or thermal Wino dark matter around 3 TeV in models of anomaly mediation with long-lived Winos. We show moreover how collider searches and direct detection experiments have the potential to cover large part of the parameter space even in scenarios where the lightest neutralino does not contribute to the whole dark matter relic density.Comment: 25 pages, matches version accepted by JHE

Phenomenology of dark matter at present and future experiments

In this thesis we present a study of two different dark matter candidates. We focus on the neutralino in split supersymmetric models and in models of Dirac gauginos, and on the QCD axion. In the first part of the thesis we discuss supersymmetric searches at future hadron colliders and dark matter direct detection experiments. We obtain mass reach for several simplified models in split supersymmetry with neutralino or gravitino lightest supersymmetric particle at 14, 33 and 100 TeV collider. In particular, a supersymmetric simplified model of anomaly mediation with long lived Winos has crucial importance in the hunt for dark matter since a Wino lightest supersymmetric particle is expected to thermally saturate the relic density for $m_{\tilde{W}}\sim 3$ TeV. In addition, we consider the discovery reach of a future 100 TeV collider for strongly coupled states in supersymmetric theories with Majorana gluinos, and extend this to the cases with Dirac gluinos. Furthermore, we discuss the current bounds and future reach from dark matter direct detection experiments for split SUSY models with universal gaugino masses and models of anomaly mediation. We then study the interplay between the collider and dark matter searches for the models considered. Also, we consider the dark matter candidate in Dirac gaugino models and the relation between collider searches and dark matter direct detection experiments. In the second part of this thesis, we study the properties of the QCD axion at zero and finite temperature. The computation of the relic abundance for QCD axion from the misalignment mechanism dramatically depends on the behaviour of the axion potential at finite temperature. Consequently, we compute the axion potential, and therefore its mass, at temperatures below the crossover ($T_c\sim170$ MeV) exploiting chiral Lagrangians. Around the critical temperature $T_c$ there is no known reliable perturbative expansion under control and non-perturbative methods, such as lattice QCD, are required. At higher temperatures, when QCD becomes perturbative, the dilute instanton gas approximation is available, which is expected to be reliable at temperatures large enough. We point out however that the bad convergence of the perturbative QCD expansion at finite temperatures makes the instanton result unreliable for temperatures below $10^{6}$ GeV. Therefore, we study the impact of the uncertainty in the computation of the axion relic abundance, providing updated plots for the allowed axion parameter space. Finally, motivated by the fact that zero temperature properties of the QCD axion are fundamental in case of axion discovery in order to infer its possible UV completion, we perform a NLO computation using chiral Lagrangians. We extract zero temperature axion properties, such as the mass, the potential, the self-coupling, the coupling to photon and the tension of domain walls, at the percent level. Moreover, we show a new strategy to extract couplings to nucleons directly from first principle QCD at the 10\% level. Such result can be improved as more lattice QCD simulations become available

Future DUNE constraints on EFT

In the near future, fundamental interactions at high-energy scales may be most efficiently studied via precision measurements at low energies. A universal language to assemble and interpret precision measurements is the so-called SMEFT, which is an effective field theory (EFT) where the Standard Model (SM) Lagrangian is extended by higher-dimensional operators. In this paper we investigate the possible impact of the DUNE neutrino experiment on constraining the SMEFT. The unprecedented neutrino flux offers an opportunity to greatly improve the current limits via precision measurements of the trident production and neutrino scattering off electrons and nuclei in the DUNE near detector. We quantify the DUNE sensitivity to dimension-6 operators in the SMEFT Lagrangian, and find that in some cases operators suppressed by an O(30) TeV scale can be probed. We also compare the DUNE reach to that of future experiments involving atomic parity violation and polarization asymmetry in electron scattering, which are sensitive to an overlapping set of SMEFT parameters.Comment: 23 pages, 4 figures; v2, agrees the version published in JHE

Probing light mediators at the MUonE experiment

The MUonE experiment, that aims to provide a precise measurement of the hadronic vacuum polarization contribution to the muon $g-2$ via elastic muon-electron scattering, has also the potential to explore the parameter space of light new physics. Exploiting the process $\mu^- N \to \mu^- N X$, where $N$ is the target nucleus and X is a new physics light mediator, we demonstrate that MUonE can be sensitive to new regions of parameter space for sub-GeV dark photons. In particular, thanks to its muon beam, MUonE will be able to explore uncharted parameter space regions for the $L_\mu-L_\tau$ model. Finally, we also find that MUonE can probe the parameter space of axion-like particles for different assumptions of the couplings to electrons, muons and photons.Comment: 6 pages, 3 figure

Collider phenomenology of Hidden Valley mediators of spin 0 or 1/2 with semivisible jets

Many models of Beyond the Standard Model physics contain particles that are charged under both Standard Model and Hidden Valley gauge groups, yet very little effort has been put into establishing their experimental signatures. We provide a general overview of the collider phenomenology of spin 0 or 1/2 mediators with non-trivial gauge numbers under both the Standard Model and a single new confining group. Due to the possibility of many unconventional signatures, the focus is on direct production with semivisible jets. For the mediators to be able to decay, a global $U(1)$ symmetry must be broken. This is best done by introducing a set of operators explicitly violating this symmetry. We find that there is only a finite number of such renormalizable operators and that the phenomenology can be classified into five distinct categories. We show that large regions of the parameter space are already excluded, while others are unconstrained by current search strategies. We also discuss how searches could be modified to better probe these unconstrained regions by exploiting special properties of semivisible jets.Comment: 40 pages, 11 figures, published versio