Jun 29, 2018 is your question what types of early universe effects you need to consider if there are additional sterile neutrinos. In fact, very heavy sterile neutrinos might even be dark matter, though this is probably not the case. Thermalisation of light sterile neutrinos thomas tram department of physics and astronomy, aarhus university, ny munkegade 120, dk8000 aarhus c. The early universe represents an important environment to test the neutrino proprieties. Is your question what types of early universe effects you need to consider if there are additional sterile neutrinos. Daya bay collaboration measured the antineutrino energy spectrum, and found that antineutrinos at an energy of around. Nov 28, 20 considering the dodelsonwidrow and thermal models for the statistical cosmological distribution of sterile neutrinos, we found that in the dodelsonwidrow model there is a slightly better compatibility between cosmological and shortbaseline neutrino oscillations data and the required suppression of the production of sterile neutrinos in the. Sterile neutrino in cosmo logy dissertation for doctoral degree. We consider the history of the universe from the inflationary era through today and demonstrate that most of the observed phenomena beyond the standard model. Daya bay collaboration measured the antineutrino energy spectrum, and found that anti neutrinos at an energy of around 5 mev are in excess relative to theoretical expectations. Light sterile neutrinos the socalled shortbaseline sbl neutrino oscillation anomalies see e. N eff3 but the spectrum of active neutrinos is distorted direct effect of e and anti e on bbn.
Once the answers to these questions are at hand, we will have. Reconciling cosmology and shortbaseline experiments with invisible decay of light sterile neutrinos. We calculate the thermalisation process of light, sterile neutrinos in the early universe for a range of mixing angles and massdi erences. These anomalies require the presence of a light sterile neutrino at ev scale having nontrivial mixing with the active neutrinos as presented in the global. If some of the singlet fermions are light, the sterile neutrinos appear in the lowenergy effective theory. A relic neutrino background pervading the universe the cosmic neutrino background, c. N eff4 if oscillations are effective after decoupling. In particular, sterile neutrinos with masses of several kev can account for cosmological dark matter, which can be relatively warm or cold, depending on the production mechanism. Tantalizing cosmological and terrestrial evidence suggests the number of light neutrinos may be greater than 3, motivating a careful. Light sterile neutrinos and icecube jj cherry virginia tech alex friedland slac blv conference, case western reserve university, may 2017 ian shoemaker. How does it fit with the current cosmological bound for neutrinos. Sterile neutrinos are natural extensions to the standard model of particle physics in neutrino mass generation mechanisms. On the one hand 1 additional degree of freedom is excluded by bbn and cmb observations.
Extended models with light sterile neutrinos, light thermal axions or other light relics sometimes referred to as dark radiation. They can play an important role in astrophysics and cosmology. Status of light sterile neutrino searches sciencedirect. Daya bay has also searched for a light sterile neutrino and excluded some mass regions. Sterile neutrinos are also candidates for dark radiation. Particles and fields 878 january 20 with 47 reads how we measure reads. Considering the dodelsonwidrow and thermal models for the statistical cosmological distribution of sterile neutrinos, we found that in the dodelsonwidrow model there is a slightly better compatibility between cosmological and shortbaseline neutrino oscillations data and the required suppression of the production of sterile neutrinos in the. Light sterile neutrinos in cosmology and shortbaseline oscillation experiments. Smallscale crisis in cosmology sterile neutrinos to the.
Big bang nucleosynthesis constrains the number of relativisti. Additional light sterile neutrinos and cosmology arizona. If they are relatively light, less than approximately 10 kev, they can alter cosmology significantly, from the early universe to the matter and radiation energy density today. Smallscale crisis in cosmology sterile neutrinos to the rescue. It is through this subtle effect that we hope to find sterile. Even though it may not prove the existence of the fourth neutrino type, the project sheds light on the. While the effects we investigate here could play a role, we nevertheless find that two additional light sterile neutrinos species cannot fit all the data at the 95% confidence level. Recent results by microboone seems to give support to old lsnd experiment in favor of a fourth neutrino sterile. Extended models with light sterile neutrinos, light thermal axions or other light relics sometimes referred to as dark radiation would produce e. Tantalizing cosmological and terrestrial evidence suggests the number of light neutrinos. At first order, cosmology is sensitive to the total neutrino mass, but is blind to. Additional light particle n dark radiation charged under u1x. Rasmus sloth hansen department of physics and astronomy, aarhus university january 30, 2015.
Cosmic strings as emitters of extremely high energy neutrinos. The indications in favor of the existence of light sterile neutrinos at the ev scale found in. There is another reason to consider additional relativistic particles such as light sterile neutrinos in cosmology, independent of the anomalous. Light sterile neutrinos and pseudoscalar interactions in. The answer to that question depends on its mass and mixing with the active neutrinos as well as what epoch of the early universe you are considering. In this work, the methods of quantum optics, quantum. Seeking sterile neutrinos in finslerian cosmology pdf. If neutrinos are mixed and massive, additional sterile neutrinos could be abundantly produced in the early universe. Reconciling cosmology and shortbaseline experiments with.
Bounds on light sterile neutrino mass and mixing from. Sterile neutrinos in cosmology light sterile neutrinos can have important effects in big bang nucleosynthesis bbn, the process thought responsible for generating the light isotopes 4he, 3he, d, and 7li. This mechanism works assuming the initial population of this sterile sector to be. Wong rwth aachen launch, heidelberg, november 912, 2009.
The role of sterile neutrinos in cosmology and astrophysics. We present a comprehensive overview of an extension of the standard model that contains three righthanded sterile neutrinos with masses below the electroweak scale the neutrino minimal standard model. The existence of light sterile neutrino have deep consequences in cosmology in the nucleosynthesis, cosmic microwave background and large scale structure formation. At the moment, such extensions are, however, not required by the cosmological data at any signi.
Neutrinos in cosm ology and particle physics jun wu, phd university of pittsburgh, 2011 this thesis discusses two independent research topics. Additional light sterile neutrinos and cosmology core. Apart from these reactor and accelerator based experiments, there were initial hints from cosmology as well, suggesting the presence of one additional. Pdf additional light sterile neutrinos and cosmology. At the ew scale all of the sm degrees of freedom are thermally coupled to the universe. Sterile neutrinos in cosmology inspire inspire hep. Recently, various models of neutrino selfinteractions 6 have been proposed to reconcile sterile neutrinos in cosmology, by preventing additional neutrinos. Tantalizing cosmological and terrestrial evidence suggests the number of light neutrinos may be greater than 3, motivating a careful reexamination of cosmological bounds on extra light species. In deed big bang nucleosynthesis, cosmic microwave background. These effects of an additional relativistic sterile neutrino can be partially compensated if other cosmological parameters are simultaneously. Constraining light sterile neutrino mass with the bicep2keck array. Prepared for submission to jcap bounds on light sterile neutrino mass and mixing from cosmology and laboratory searches ste.
Neutrino cosmology the role that neutrinos have played in the evolution of the universe is one of the most fascinating research areas that has stemmed from the interplays between cosmology, astrophysics and particle physics. Bounds on light sterile neutrino mass and mixing from cosmology. Extended models with light sterile neutrinos, light thermal axions or other light relics. Light sterile neutrino limits from cosmology inspire.
Light neutrinos in cosmology neutrinos and primordial nucleosynthesis neutrino oscillations in the early universe 1st lecture. Mysterious particle that shouldnt exist may demand new physics. What if additional, light sterile neutrino species are mixed with the flavour neutrinos. Light neutrinos cannot be the only dark matter component max. Is there evidence for additional neutrino species from cosmology. Pdf cosmological constraints on a light nonthermal sterile neutrino. In the avor basis the three standard active avor neutrinos e. Results from planck 4 are compatible with three lightest neutrinos and with the total mass of neutrinos p. While the effects we investigate here could play a role, we nevertheless find that two additional light sterile neutrinos species cannot fit all the data at the 95%. Home anu research anu scholarly output anu research publications additional light sterile neutrinos and cosmology additional light sterile neutrinos and cosmology. Sterile neutrino, in addition to providing neutrino mass generation, depending on its mass scale, may have many important cosmological implications. The number of s indicates how much i know about the experiments that are supposed to address these issues.
Light sterile neutrinos and pseudoscalar interactions in cosmology stefano gariazzo 1. For the first time, to search for sterile neutrinos in the framework of finler geometry, we constrain four cosmological models using the most stringent constraint we can provide so far. From experiments, it is known that there are at least at most three neutrinos families and from lep data the number of light. Topics in neutrino physics and cosmology louis anthony lello, phd university of pittsburgh, 2016 this thesis focuses on timely issues in particle physics of neutrino phenomenology and cosmology.
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