BNL Physics Department Videos

Physics Colloquium of 11 July 2017
"Anomalies in Reactor Neutrinos"
Chao Zhang, BNL

Nuclear reactors are one of the most intense, pure, controllable, cost-effective and well-understood sources of neutrinos. Reactor neutrinos have played a major role in the discovery of neutrinos and neutrino oscillations. However, recently there emerged a few anomalies from reactor neutrino experiments when compared with state-of-the-art model predictions. The anomalies include a 5.5% deficit of the integrated antineutrino flux, a discrepancy in the antineutrino prompt energy spectrum around 5 MeV, and a 7.8% deficit in the 235U antineutrino flux from the new fuel evolution analysis in the Daya Bay Experiment. In this talk, those anomalies and their implications will be discussed. A new reactor neutrino experiment, PROSPECT, is aiming to resolve the anomalies by precisely measuring the 235U antineutrino spectrum at a very short baseline. The status of the PROSPECT experiment will also be reported.

URL of online video: https://bluejeans.com/s/ebmGE/

Physics Colloquium of 16 May 2017
"Direct Detection of sub-GeV Dark Matter"
Rouven Essig, Stony Brook University

Dark matter makes up 85% of the matter in our Universe, but we have yet to learn its identity. A broad array of search strategies are needed to probe for non-gravitational interactions between dark matter and ordinary matter. While most searches focus on Weakly Interacting Massive Particles (WIMPs) with masses between 1 GeV and 1 TeV, it is imperative to also consider other motivated dark matter candidates. In this talk, I will discuss dark matter with MeV-to-GeV masses, which is a theoretically and phenomenologically appealing possibility and presents a new frontier in the search for dark matter. I will highlight novel dark matter direct-detection strategies that can probe this under-explored mass range. I will describe how XENON10 data already probes dark matter with masses as low as a few MeV, and discuss improvements expected from new experiments using semiconductors or scintillators. This includes SENSEI, a new ultra-low-threshold silicon CCD detector, which is poised to probe vast new regions of parameter space in the next few years. I will also present a few simple benchmark models of MeV-to-GeV dark matter, and contrast direct-detection probes with searches at colliders and fixed-target experiments.

URL of online video: https://bluejeans.com/s/DWSlU/

Physics Colloquium of 25 April 2017
"Current Status of Neutrinoless Double Beta Decay Research"
Bob McKeown, Jefferson Lab

The observation of neutrinoless double beta decay would establish that neutrinos are Majorana fermions and would represent a discovery of profound importance: that lepton number is not conserved. There is currently a worldwide effort to search for neutrinoless double beta decay, using a variety of candidate isotopes and detector technologies. A subcommittee of the Nuclear Science Advisory Committee (NSAC) recently surveyed the field and the associated research and development needs. Based on the information provided to this subcommittee, I will present an overview of the present activity in this field and the prospects for the future.

URL of online video: https://bluejeans.com/s/Orxtu/

Physics Colloquium of 28 March 2017
"Physics in the complex domain"
Carl Bender, Washington University

The theory of complex variables is extremely useful because it helps to explain the mathematical behavior of functions of a real variable. Complex variable theory also provides insight into the nature of physical theories. For example, it provides a simple and beautiful picture of quantization and it explains the underlying reason for the divergence of perturbation theory. By using complex-variable methods one can generalize conventional Hermitian quantum theories into the complex domain. The result is a new class of parity-time-symmetric (PT-symmetric) theories whose remarkable physical properties have been studied and verified in many recent laboratory experiments.

URL of online video: https://bluejeans.com/s/paDiJ/

Physics Colloquium of 7 March 2017
"Snapping pictures of the proton with heavy ions"
Bjoern Schenke, BNL

I will present an overview of recent theoretical developments related to the science program at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory and the Large Hadron Collider at CERN. Beginning from heavy ion collisions and the creation of the quark gluon plasma, the most perfect and hottest fluid every created on earth, I will proceed to discuss smaller collision systems, like proton+lead collisions. The experimental data from these show strikingly similar features to heavy ion collisions and I will discuss their possible origins. If the physics in these small systems is also dominated by the fluid dynamic behavior of the created matter, experimental measurements combined with theoretical models give us unprecedented access to the fluctuating shape of the proton.

URL of online video: https://bluejeans.com/s/8LYQI/

Physics Colloquium of 28 February 2017
"The Experimental Challenge of 21 cm Cosmology"
Miguel Morales, University of Washington

URL of online video: https://bluejeans.com/s/NbgwK/

Physics Colloquium of 14 February 2017
"Thermalization and hydrodynamization in heavy-ion collisions at high energies"
Aleksi Kurkela, CERN and Univ. of Stavenger

Describing heavy-ion collisions as hydrodynamical explosions of liquid of quarks and gluons has been a tremendous phenomenological success. A major uncertainty in such modeling arises from what happens during the first 1fm/c of the evolution during which the system is far from local thermal equilibrium. I will describe how the postcollision debris start behaving hydrodynamically, and how the phenomenological modeling of the prehydrodynamical evolution can be improved.

URL of online video: https://bluejeans.com/s/cG3S2/

Physics Colloquium of 17 January 2017
"And yet they attract: superconductivity in the presence of strong repulsion"
Andre-Marie Tremblay, University of Sherbrooke, Quebec, Canada

Band theory and the BCS theory of superconductivity are two pillars of the quantum theory of solids. High-temperature superconductors belong to a family of materials where both of these, band theory and BCS, fail. Layered organic materials of the BEDT family are another example of materials that are hard to understand within conventional approaches. The root cause of these failures can be traced to strong electronic repulsion. I will start from the simplest model that takes into account the competition between kinetic and potential energy, the Hubbard model. I will show how cluster generalizations of dynamical mean-field theory for this model shed light on these problems. The interaction-induced metal-insulator transition (Mott transition) can serve as an organizing principle for the phase diagrams.

URL of online video: https://bluejeans.com/s/cQzjz/

Other Listings

Colloquium Note

Colloquia can generally be viewed live by going to
https://bluejeans.com/308299597
Colloquia usually occur on Tuesday's at 3:30 pm.

Notes

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