# Events at Physics

<< Summer 2022 Fall 2022 Spring 2023 >>

### Monday, August 22nd, 2022

Theory Seminar (High Energy/Cosmology)
Interesting Aspects of Nearly Extremal Black Holes
Time: 12:00 pm
Place: Chamberlin 5280
Speaker: Upamanyu Moitra, ICTP
Abstract: I will discuss some very interesting aspects of physics one can learn from studying nearly extremal black holes, especially the near-horizon AdS_2 region.
Host: George Wojcik

### Tuesday, August 23rd, 2022

Thesis Defense
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

Theory Seminar (High Energy/Cosmology)
Two problems for strong CP: Topological quantization and the first postulate of quantum mechanics
Time: 12:00 pm
Place: Chamberlin 5280
Speaker: Bjorn Garbrecht, Munich Tech. U.
Abstract: In the path integral quantization of Yang-Mills theory, integer topological sectors follow only when Euclidean time is taken to infinity. This implies that the spacetime volume must be taken to infinity before interfering among the sectors. On the other hand, in canonical quantization, the standard theta-vacua are not properly normalizable without further ado. We revisit the well-known analogy with a point particle on a circle. It is sometimes argued that continuous energy bands corresponding to Bloch states exist for this problem. We show however that the states in these bands exhibit an inconsistent time evolution, unless narrowing the energy band to just one allowed state. From either perspective one can understand why no CP violation is seen in the strong interactions.
Host: George Wojcik
Physics Summer Fun
Weekly Recess
Time: 12:30 pm
Place: Bascom Hill or 5310 Chamberlin Hall
Speaker: Sharon Kahn
Abstract: We hope you’ll take a 20-30 minute break on (some/all) Wednesdays this summer (12:30-1pm) to come play together! For nice days, we’ve arranged to borrow some lawn games from the L&S dean’s office and will likely bring along a frisbee and/or a hackeysack, too. Meet us on Bascom Hill (between Birge/South Hall).
In case of rain, we’ll meet indoors (5310 CH) for board games. Feel free to come play or just hang out!
Thesis Defense
Measuring the Atmospheric Neutrino Oscillation Parameters with IceCube DeepCore
Time: 2:00 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

Thesis Defense
A Few New Techniques for Probing IceCube Data and a Search for High Energy Atmospheric Neutrinos
Time: 2:00 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

Thesis Defense
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
Time: 4:00 pm