Thesis Defense |
Events During the Week of August 21st through August 28th, 2022
Monday, August 22nd, 2022
- No events scheduled
Tuesday, August 23rd, 2022
- Sterile Neutrino Search with the NOvA Detectors
- Time: 9:00 am
- Place: Chamberlin 4274
- Speaker: Harry Hausner , Physics PhD Graduate Student
- Abstract: NOvA is a two detector experiment designed to observe neutrino oscillations from $\nu\mu$ to $\nu_e$ flavor states. Additionally, the location of the NOvA Near Detector is well situated to additionally observe short baseline oscillations to sterile neutrino states. We expand upon previous NOvA sterile neutrino searches by using a covariance matrix fitting technique. This analysis is the first with NOvA to directly include neutrino interactions in the Near Detector while fitting the data. The NOvA Near Detector's greater statistics to better constrain our Far Detector uncertainties in addition to increasing the range of $\Delta m^2{41}$ to which we are sensitive.
- Host: Brian Rebel
Wednesday, August 24th, 2022
- Measuring the Atmospheric Neutrino Oscillation Parameters with IceCube DeepCore
- Time: 2:00 pm - 6:00 pm
- Place: Chamberlin 4274
- Speaker: Kayla DeHolton , Physics PhD Graduate Student
- Abstract: The discovery of neutrino oscillations (and consequently the implication that neutrinos have mass) is one of the only confirmed pieces of evidence of physics beyond the Standard Model. Since this discovery, there has been a worldwide effort to measure the model parameters that describe these oscillations. The DeepCore sub-array within the IceCube Neutrino Observatory is a densely instrumented detector embedded in the Antarctic ice at the South Pole and detects Cherenkov light from the interactions of atmospheric neutrinos with energies down to 5 GeV. At these energies, Earth-crossing muon neutrinos have a high chance of oscillating to tau neutrinos. DeepCore is able to measure these oscillations with precision comparable to accelerator-based experiments, but it is also complementary to accelerator measurements because it probes longer distance scales and higher energies, peaking above the tau lepton production threshold. This dissertation presents the effort involved in curating one of the largest neutrino oscillation datasets in the world, with over 200,000 events spanning almost 10 years and a neutrino purity of over 99%. The nearly unprecedented level of statistics also requires unprecedented precision in the treatment of systematic uncertainties and other analysis techniques. I will present the status of an analysis to measure the atmospheric neutrino oscillation parameters using the full dataset, as well as the unblinded results of a measurement performed with a sub-sample containing 20% of the full dataset.
- Host: Francis Halzen
Thursday, August 25th, 2022
- A Few New Techniques for Probing IceCube Data and a Search for High Energy Atmospheric Neutrinos
- Time: 2:00 pm - 6:00 pm
- Place:
- Speaker: Bunheng Ty, Physics PhD Graduate Student
- Abstract: The idea of characterizing an IceCube event by its location and magnitude of maximum photon density is proven useful. A complete set of new filter tools built around this idea is successfully developed and used to detect high-energy neutrino interactions inside IceCube. The two key features to search for are: a highly localized deposit of photoelectrons, and a lack of a veto track leading up to it. The first is achieved reliably by counting photoelectrons making up the most photon-dense region of the event. The second is achieved with moving cylinders (160 m radius, 240 m half-height, 0.3 m/ns speed), one at each possible direction from the sky, collecting any DOM forming a muon track pattern with the region. In addition to the traditional true starting events, this new approach allows, for the first time, a direct search for the self-veto events of the atmospheric neutrinos. The no-veto condition is loosened to allow up to a very small veto, just enough to be still outside the region of the atmopsheric muon background. The final selection consists of 23 events, one of which is a self-veto event of 134 TeV Millipede reconstructed energy. This data, though limited, shows a measurable contribution of the atmospheric component to the neutrino flux at the high energies. A lower bound estimate is given for the atmospheric contribution to IceCube’s HESE sample to be at least at the level of 1 percent.
- Host: Kael Hanson
Friday, August 26th, 2022
- Constructing an Extended TFT from an A-infinity Algebra
- Time: 11:00 am
- Place:
- Speaker: Weng-Him Cheung , Physics PhD Graduate Student
- Abstract: It is known that the category of 2-dimensional topological (quantum) field theories is equivalent to the category of commutative Frobenius algebras. Costello extended this equivalence to cyclic A-infinity algebras by introducing what he called topological conformal field theories, though he did not provide a construction. Kontsevich and Soibelman later sketched a formula for constructing a positive-boundary 2-dimensional topological field theory from a cyclic A-infinity algebra, but they only provided rough ideas. Following their work, we present the explicit construction in full detail. In particular, we describe a procedure for computing the correct signs, which had previously not been discussed.
- Host: Andrei Caldararu