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 High Energy Wednesday, January 18, 2017 3:30 PM Physics Building, Room 204 RESERVED - See Colloquia Schedule [Host: Peter Arnold] High Energy Wednesday, January 25, 2017 3:30 PM Physics Building, Room 204 Available High Energy Wednesday, February 1, 2017 3:30 PM Physics Building, Room 204 Reserved - Please see the Colloquia Schedule [Host: Peter Arnold] High Energy Wednesday, February 8, 2017 3:30 PM Physics Building, Room 204 Available [Host: ] High Energy Wednesday, February 15, 2017 3:30 PM Physics Building, Room 204 Reserved - Please see the Colloquia Schedule [Host: Peter Arnold] High Energy Wednesday, February 22, 2017 3:30 PM Physics Building, Room 204 Reserved - Please see the Colloquia Schedule [Host: Peter Arnold] High Energy Wednesday, March 1, 2017 3:30 PM Physics Building, Room 204 Reserved - Please see the Colloquia Schedule [Host: Peter Arnold] High Energy Wednesday, March 15, 2017 3:30 PM Physics Building, Room 204 Available Joint Nuclear-High Energy Seminar Wednesday, March 22, 2017 3:30 PM Physics Building, Room 204 Camillo Mariani [Host: Donal Day] Virginia Tech "Status and prospective of the SoLid/CHANDLER experiment"   Slideshow (PDF) ABSTRACT:The SoLid/CHANDLER experiment aims to make a measurement of very short baseline neutrino oscillations using reactor anti-neutrinos. For this purpose, a highly segmented detector was build out of PVT cubes lined with a 6LiF:ZnS(Ag)layer. Unlike neutrino experiments conducted deep underground, neutrino detectors used in a reactor environment need to operate in high levels of background radiation with very low shielding. Therefore, a reliable distinction between the neutrons produced in inverse beta decay events and signals caused by other background interaction is crucial. The composite of scintillation materials with different time constants enables the efficient use of pulse-shape analysis to discriminate against electromagnetic signals. In this talk I will present the SoLid detector, the signal identification with few example of inverse beta decays events that were collected during the first data taking of the first SoLid module and the future program that involves the use of the CHANDLER technology to increase the energy resolution of the SoLid detector. SLIDESHOW: High Energy Wednesday, March 29, 2017 3:30 PM Physics Building, Room 204 Keith Olive [Host: Peter Arnold] University of Minnesota "The status of Supersymmetric Dark Matter after LHC Run I and alternatives from Grand Unification"   Slideshow (PDF) SLIDESHOW: High Energy Wednesday, April 5, 2017 3:30 PM Physics Building, Room 204 RESERVED High Energy Wednesday, April 12, 2017 3:30 PM Physics Building, Room 204 RESERVED High Energy Wednesday, April 19, 2017 3:30 PM Physics Building, Room 204 Marco Harrendorf [Host: Chris Neu] KIT "Searching for the ttH(Hbb) and ttbb signal with novel techniques at CMS" ABSTRACT:In the last ten years we have experienced the start and the first triumphs of the Large Hadron Collider (LHC) located at CERN in Geneva, Switzerland. Surely, the discovery of a Standard Model-like Higgs boson in 2012 stands out within this context. But even though, that further major findings like Physics beyond the Standard Model eluded us so far, the quest for understanding our elementary nature is ongoing under full steam. One of the outstanding important checks is the determination if the Higgs boson is really the Higgs boson predicted by the Standard Model. An important puzzle piece in this aspect will be the discovery of the ttH signal process providing us with a direct measurement of the Top-Higgs-Yukawa coupling. The search for ttH in the bbar decay channel benefits from the large branching fraction of 58% for the Higgs to bbar decay. At the same time, the large irreducible tt+bb background poses a major challenge and requires the use of advanced analysis techniques. A further crucial ingredient is the estimation and modelling of the tt+bb background via MC event generators which is still afflicted with large theoretical uncertainties. This talk will discuss the work on the upcoming ttH(Hbb) analysis covering the 2016 LHC data set and ongoing work to reduce the uncertainties related to the tt+bb background. Furthermore, the talk will deliver a glimpse in the future of experimental particle physics by interspersing examples of novel techniques used in the analysis, e.g. the application of Neural Networks as a classifier, Continuous integration as an improvement of the analysis workflow, and NLO event generation for obtaining more accurate simulation data. Condensed Matter Seminar Wednesday, April 26, 2017 3:30 PM Physics Building, Room 204 Arun Paramekanti [Host: Israel Klich ] University of Toronto "TBA" Condensed Matter Seminar Thursday, April 27, 2017 1:00 PM Physics Building, Room 313 Note special date. Note special time. Note special room. Tianran Chen [Host: Seunghun Lee] UVA- Department of Physics "Origin of Long Lifetime of Band-Edge Charge Carriers in Organic-Inorganic Lead Iodide Perovskites" ABSTRACT:Long carrier lifetime is what makes hybrid organic-inorganic perovskites high performance photovoltaic materials. Several microscopic mechanisms behind the unusually long carrier lifetime have been proposed, such as formation of large polarons, Rashba effect, ferroelectric domains, and photon recycling. Here, we show that the screening of band-edge charge carriers by rotation of organic cation molecules can be a major contribution to the prolonged carrier lifetime. Our results reveal that the band-edge carrier lifetime increases when the system enters from a phase with lower rotational entropy to another phase with higher entropy. These results imply that the recombination of the photo-excited electrons and holes is suppressed by the screening, leading to the formation of polarons and thereby extending the lifetime. Thus, searching for organic-inorganic perovskites with high rotational entropy over a wide range of temperature may be a key to achieve superior solar cell performance. High Energy Wednesday, May 3, 2017 3:30 PM Physics Building, Room 204 Michael Baird [Host: Craig Group] UVA-Department of Physics "Second Numu Disappearance Results from the NOvA Experiment" ABSTRACT:In light of the Nobel Prize awarded for neutrino oscillations in 2015, it is an exciting time to be a part of a long-baseline neutrino oscillation experiment. NOvA is one such experiment based out of Fermilab National Accelerator Laboratory, which uses two liquid scintillator detectors, one at Fermilab (the near" detector) and a second 14 kton detector in northern Minnesota (the far" detector.) The primary physics goals of the NOvA experiment are to measure neutrino mixing parameters through both the numu disappearance and nue appearance channels using neutrinos from the newly upgraded NuMI beam line. This talk will present a summary of the NOvA experiment and the numu disappearance results, focusing on the implications for non-maximal mixing.