Search results for "Standardimalli"
showing 10 items of 11 documents
Electroweak baryogenesis from a dark sector
2017
Adding an extra singlet scalar $S$ to the Higgs sector can provide a barrier at tree level between a false vacuum with restored electroweak symmetry and the true one. This has been demonstrated to readily give a strong phase transition as required for electroweak baryogenesis. We show that with the addition of a fermionic dark matter particle $\chi$ coupling to $S$, a simple UV-complete model can realize successful electroweak baryogenesis. The dark matter gets a CP asymmetry that is transferred to the standard model through a $CP\ portal\ interaction$, which we take to be a coupling of $\chi$ to $\tau$ leptons and an inert Higgs doublet. The CP asymmetry induced in left-handed $\tau$ lepto…
Higgs mass predicted from the standard model with asymptotically safe gravity
2016
Tässä Pro Gradu -tutkielmassa tavoitteena on ennustaa Higgsin bosonin massa ottaen lähtökohdaksi hiukkasfysiikan standardimalli, johon on kytketty gravitaatio ns. asymptoottisesti turvallisena teoriana. Ennusteen laskemiseksi selvitetään Higgsin bosonin itseiskytkennän ja neljän muun standardimallin kytkinvakion juokseminen, eli kytkinvakioiden käyttäytyminen energiaskaalan funktiona, johtavassa kertaluvussa MS-skeemassa. Standardimallista saatuihin β-funktioihin lisätään asymptoottisesti turvallisen gravitaation antamat korjaukset suurilla energiaskaaloilla, jonka jälkeen β-funktioiden muodostama differentiaaliyhtälöryhmä ratkaistaan numeerisesti. Standardimallin osittainen äärellinen remo…
The 1-loop effective potential for the Standard Model in curved spacetime
2018
The renormalisation group improved Standard Model effective potential in an arbitrary curved spacetime is computed to one loop order in perturbation theory. The loop corrections are computed in the ultraviolet limit, which makes them independent of the choice of the vacuum state and allows the derivation of the complete set of $\beta$-functions. The potential depends on the spacetime curvature through the direct non-minimal Higgs-curvature coupling, curvature contributions to the loop diagrams, and through the curvature dependence of the renormalisation scale. Together, these lead to significant curvature dependence, which needs to be taken into account in cosmological applications, which i…
Enhancement of the double Higgs production via leptoquarks at the LHC
2021
Measurements of single Higgs production and its decays are in good agreement with the Standard Model. There is still room for large modifications in double Higgs production at LHC, though these effects may be correlated with large corrections to other observables, in particular single Higgs production. In this work we address the issue of enhancing double Higgs production in the presence of scalar leptoquarks while satisfying all experimental constraints. We show at leading order that including more than one species of leptoquarks, large cubic interactions with the Higgs can lead to sizable enhancement of di-Higgs production cross section at LHC, while at the same time keeping other Higgs o…
Higgs-like spectator field as the origin of structure
2021
We show that the observed primordial perturbations can be entirely sourced by a light spectator scalar field with a quartic potential, akin to the Higgs boson, provided that the field is sufficiently displaced from vacuum during inflation. The framework relies on the indirect modulation of reheating, which is implemented without any direct coupling between the spectator field and the inflaton and does not require non-renormalisable interactions. The scenario gives rise to local non-Gaussianity with $f_{\rm NL}\simeq 5$ as the typical signal. As an example model where the indirect modulation mechanism is realised for the Higgs boson, we study the Standard Model extended with right-handed neu…
Baryogenesis and gravity waves from a UV-completed electroweak phase transition
2021
We study gravity wave production and baryogenesis at the electroweak phase transition, in a real singlet scalar extension of the Standard Model, including vector-like top partners to generate the CP violation needed for electroweak baryogenesis (EWBG). The singlet makes the phase transition strongly first-order through its coupling to the Higgs boson, and it spontaneously breaks CP invariance through a dimension-5 contribution to the top quark mass term, generated by integrating out the heavy top quark partners. We improve on previous studies by incorporating updated transport equations, compatible with large bubble wall velocities. The wall speed and thickness are computed directly from th…
Beyond the standard model via extended symmetries and dark matter
2015
In this thesis, we discuss ideas of how to go beyond the Standard Model (SM) of particle physics to incorporate the cosmological observations of dark matter and matter–antimatter asymmetry, and to address the theoretical problems related to the scalar sector of the SM. Although the SM has proven to be an excellent description of the interactions of elementary particles, there is both experimental and theoretical evidence that this description cannot be complete. Most notably, the cosmological observations of dark matter (DM) and the matter–antimatter asymmetry in the universe cannot be explained within the SM. We have studied simple singlet extensions of the SM. We found out that these DM a…
Prospects for beyond the Standard Model physics searches at the Deep Underground Neutrino Experiment
2021
The Deep Underground Neutrino Experiment (DUNE) will be a powerful tool for a variety of physics topics. The high-intensity proton beams provide a large neutrino flux, sampled by a near detector system consisting of a combination of capable precision detectors, and by the massive far detector system located deep underground. This configuration sets up DUNE as a machine for discovery, as it enables opportunities not only to perform precision neutrino measurements that may uncover deviations from the present three-flavor mixing paradigm, but also to discover new particles and unveil new interactions and symmetries beyond those predicted in the Standard Model (SM). Of the many potential beyond…
Dark matter and baryogenesis in Higgs portal models
2016
This work focuses on two of the main issues in current understanding of particle physics described by the Standard Model. The Standard Model, despite of its success, is not complete. Existence of dark matter has been clearly verified, but its nature is unknown. Also, the baryon asymmetry in the Universe hints that the Standard Model has to be extended. In this thesis we study Higgs portal models which both contain dark matter candidates, and can provide for a successful production of the baryon asymmetry.