Phenomenology of Neutrino Portal Dark Matter and Supersymmetry

In this thesis we investigate the neutrino portal dark matter which tries to explain non-baryonic dark matter and the neutrino masses at the same time. Bearing in mind that natural theories like the Minimal Supersymmetric Standard Model also provide a WIMP type candidate for dark matter, we also calculate the sensitivities of the High Luminosity (HL) and High Energy (HE) upgrades of the Large Hadron Collider to strong supersymmetry signals. Firstly, we study the feasibility of the indirect detection of dark matter in a simple model using the neutrino portal. We derive the existing constraints on this scenario from Planck cosmic microwave background measurements, Fermi dwarf spheroidal galaxies and Galactic Center gamma-rays observations, and AMS-02 antiprotons observations. Secondly, by modifying our simple model, we analyze the scenario in which a thermal dark matter annihilating to standard model neutrinos via the neutrino portal. We derive existing constraints and future projections from direct detection experiments, colliders, rare meson and tau decays, electroweak precision tests, and small scale structure observations. Finally, we evaluate the sensitivities of the High Luminosity (HL) and High Energy (HE) upgrades of the LHC to gluinos and stops, decaying through the simplified topologies. Our HL-LHC analyses improve on existing experimental projections by optimizing the acceptance of kinematic variables

Comparing the early function and complications between fluoroscopic guidance and blindly insertion of permanent hemodialysis catheter

Objective: Chronic kidney disease (CKD) is a complicated kidney defect causing permanent failure in renal function in progressive stages. Hemodialysis is the most accepted treatment to maintain body’s fluid/electrolyte homeostasis at the terminal stages of the disease. Permanent hemodialysis catheter (permicath) may be inserted blindly or by fluoroscopic guidance. This study aimed to compare the early function and complications between fluoroscopic guidance and blindly insertion of permanent hemodialysis catheter. Methods: This prospective randomized clinical trial was undertaken in the emergency department of Modarres hospital in Tehran, Iran during 2014 and 2015. Patients who needed catheter due to renal failure entered the study. Patients who needed emergency dialysis and those who could not wait for permicath were excluded. Patients were randomly assigned into 2 groups, under fluoroscopic guidance and blindly catheter insertion. Data were collected using a questionnaire and a checklist related to function (after 24 hours and 1 month), a need to exchange the catheter and the early adverse effects such as pneumothorax, hemothorax, and vascular injury. Results: A total of 101 patients were enrolled in this trial. Early dysfunction (blind group= 5), a need for catheter exchange (blind group= 2), pneumothorax (blind group=2), vascular injury (blind group=1) were recorded but the difference between the two groups was not statistically significant (P>0.05). Conclusion: We did not observe a significant difference between the placement of permicath by fluoroscopic or blind method. However, more studies with larger groups are recommended. Keywords: Permanent hemodialysis catheter, Fluoroscopic guidance, Blindly insertio

Dark Matter production during Warm Inflation via Freeze-In

We present a novel perspective on the role of inflation in the production of Dark Matter (DM). Specifically, we explore the DM production during Warm Inflation via ultraviolet Freeze-In (WIFI). We demonstrate that in a Warm Inflation (WI) setting the persistent thermal bath, sustained by the dissipative interactions with the inflaton field, can source a sizable DM abundance via the non-renormalizable interactions that connect the DM with the bath. Compared to the (conventional) radiation-dominated (RD) UV freeze-in scenario for the same reheat temperature (after inflation), the resulting DM yield in WIFI is always enhanced, showing a strongly positive dependence on the mass dimension of the non-renormalizable operator. Of particular interest, for a sufficiently large mass dimension of the operator, the entirety of the DM abundance of the Universe can be created during the inflationary phase. For the specific models we study, we find an enhancement in DM yield of up to 30 orders of magnitude relative to RD UV freeze-in for the same reheat temperature. Our findings also suggest a broader applicability for producing other cosmological relics, which may have a substantial impact on the evolution of the early Universe.Comment: 7 pages, 4 figure

The Primordial Black Holes that Disappeared: Connections to Dark Matter and MHz-GHz Gravitational Waves

In the post-LIGO era, there has been a lot of focus on primordial black holes (PBHs) heavier than $\sim 10^{15}$g as potential dark matter (DM) candidates. We point out that the branch of the PBH family that disappeared - PBHs lighter than $\sim 10^9$g that ostensibly Hawking evaporated away in the early Universe - also constitute an interesting frontier for DM physics. Hawking evaporation itself serves as a portal through which such PBHs can illuminate new physics, for example by emitting dark sector particles. Taking a simple DM scalar singlet model as a template, we compute the abundance and mass of PBHs that could have provided, by Hawking evaporation, the correct DM relic density. We consider two classes of such PBHs: those originating from curvature perturbations generated by inflation, and those originating from false vacuum collapse during a first-order phase transition. For PBHs of both origins we compute the gravitational wave (GW) signals emanating from their formation stage: from second-order effects in the case of curvature perturbations, and from sound waves in the case of phase transitions. The GW signals have peak frequencies in the MHz-GHz range typical of such light PBHs. We compute the strength of such GWs compatible with the observed DM relic density, and find that the GW signal morphology can in principle allow one to distinguish between the two PBH formation histories.Comment: 23 pages + references, 8 figure

Recycled Dark Matter

We outline a new production mechanism for dark matter that we dub "recycling": dark sector particles are kinematically trapped in the false vacuum during a dark phase transition; the false pockets collapse into primordial black holes (PBHs), which ultimately evaporate before Big Bang Nucleosynthesis (BBN) to reproduce the dark sector particles. The requirement that all PBHs evaporate prior to BBN necessitates high scale phase transitions and hence high scale masses for the dark sector particles in the true vacuum. Our mechanism is therefore particularly suited for the production of ultra heavy dark matter (UHDM) with masses above $\sim 10^{12}\,{\rm GeV}$. The correct relic density of UHDM is obtained because of the exponential suppression of the false pocket number density. Recycled UHDM has several novel features: the dark sector today consists of multiple decoupled species that were once in thermal equilibrium and the PBH formation stage has extended mass functions whose shape can be controlled by IR operators coupling the dark and visible sectors.Comment: 23 pages, 7 figures; v2: Lifetime of scalar updated. Conclusions unchange