nuclear seminar

Confronting Anomalies at Reactor Antineutrino Experiments

Date: 
Thursday, September 12, 2019 - 2:00pm to 3:00pm
Location: 
CP 179
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Speed of Gravitational Waves as a New Probe of Ultra-light Dark Matter

There exists a class of ultralight Dark Matter (DM) models which could form a Bose-Einstein condensate (BEC) in the early universe and behave as a single coherent wave instead of individual particles in galaxies. We show that a generic BEC DM halo intervening along the line of sight of a gravitational wave (GW) signal could induce an observable change in the speed of GW, with the effective refractive index depending only on the mass and self-interaction of the constituent DM particles and the GW frequency. Hence, we propose to use the deviation in the speed of GW as a new probe of the BEC DM parameter space. With a multi-messenger approach to GW astronomy and/or with extended sensitivity to lower GW frequencies, the entire BEC DM parameter space can be effectively probed by our new method in the near future.
Date: 
Tuesday, March 6, 2018 - 11:00am to 12:00pm
Location: 
CP 179
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Baryogenesis, Dark Matter, Neutron-Antineutron Oscillation and Collider Signals

We will discuss a simple model of low-energy baryon number violation in order to simultaneously explain the observed matter-antimatter asymmetry and dark matter relic density in the universe. The stability of dark matter is related to the stability of the proton. The model predicts a sizeable rate for the neutron-antineutron oscillation at low energy and a new type of monojet signal at the LHC. There exists an interesting complementarity between the observed baryon asymmetry, ratio of dark matter and baryon abundances, neutron-antineutron oscillation lifetime and the LHC monojet signal. 
Date: 
Monday, March 5, 2018 - 2:00pm to 3:00pm
Location: 
CP 179
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The measurement of neutron beta decay observables with the Nab spectrometer


Nab, an experiment that allows studying unpolarized neutron beta decay at the Spallation Neutron Source at Oak Ridge National Lab, aims to determine a, the neutrino-electron correlation coefficient, and b, the Fierz interference term, with high precision. Such measurements provide opportunities to search for evidence of extensions to the Standard Model. Nab is presently being constructed. The spectrometer magnet is supposed to arrive in the week I am giving this seminar. Beam readiness planned for end of summer 2018. I will discuss the experiment’s motivation and design, the planned modes of operation, and the performance of its components.
Date: 
Thursday, February 22, 2018 - 2:00pm to 3:00pm
Location: 
CP 179
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Nuclear Seminar: Taming the nuclear beta decay Hydra: One theoretical head at a time

The study of nuclear beta decay has been at the forefront of our current understanding of the physical landscape, 
and continues to play an essential role in the search for beyond Standard Model physics. In order to separate the 
wheat from the chaff of the myriad possible theoretical extensions, a reliable estimate of the Standard Model 
contribution is indispensable. Recently, the description of the allowed beta spectrum shape was revisited and 
extended in order to tackle these challenges. Besides the study of the fundamental nature of the weak interaction, 
the beta spectrum shape is an essential ingredient in several outstanding problems in particle physics, such as 
the reactor antineutrino anomaly. We will provide an overview of the current state-of-the-art and its challenges, 
and discuss its implications on the reactor anomaly.
Date: 
Thursday, November 2, 2017 - 2:00pm to 3:00pm
Location: 
CP 179
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Nuclear Seminar: Neutron lifetime with a cold neutron beam at NIST

Date: 
Thursday, October 19, 2017 - 2:00pm to 3:00pm
Location: 
CP 179
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Nuclear Seminar: The Qweak Experiment - Direct Measurement of the Weak Charge of the Proton

The Qweak experiment at Jefferson Laboratory made the first direct determination of the proton’s weak charge via a measurement of the parity-violating asymmetry in elastic electron-proton scattering at low four-momentum transfer. A longitudinally polarized electron beam was scattered off a liquid hydrogen target and detected in eight azimuthally symmetric fused silica detectors. The parity violation asymmetry was measured by observing the difference in rates seen in the detectors when the helicity of the electron beam was rapidly reversed. The commissioning run result was published in 2013, with a measured asymmetry of − 279 ± 35 ( stat ) ± 31 ( syst ) ppb. When combined with previous parity-violating electron scattering (PVES) data, we obtained a value for weak charge of proton, 0.064 ± 0.012, which agrees well with the prediction of Standard Model.
Date: 
Thursday, October 12, 2017 - 2:00pm to 4:00pm
Location: 
CP 179
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Nuclear Seminar: Hidden Sectors and How to Find Them

Over the past several years, “hidden sectors” have attracted a surge of interest in the particle physics community. I’ll summarize the underlying physics motivation and give an update on various search strategies. Most of the talk will focus on new bounds on dark sector models, emphasizing where Standard Model uncertainties still play a big part. In particular, we’ll examine bounds on "dark photons" from Supernova 1987A, where we have incorporated finite-temperature effects on the production and trapping for the first time, utilized a realistic model of the high-mixing parameter space, and shown the effect of systematic uncertainties from stellar progenitor models. Other hidden sector scenarios will be addressed as time permits.

Date: 
Thursday, April 6, 2017 - 2:00pm to 3:00pm
Location: 
CP179
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Joint Nuclear/High Energy Seminar: Effective Theory for Dark Matter Direct Detection

The existence of dark matter is one of the few solid hints for physics beyond the standard model. If dark matter has indeed particle nature, then direct detection via scattering on atomic nuclei is one of the most promising discovery channels. In order to connect this nonrelativistic process with astrophysical and collider searches, as well as UV model building, a consistent setup of effective field theories for the different energy scales is necessary.

After an introduction to the physics of dark matter, I will present our work on the explicit connection between these energy scales, from the UV down to the nuclear scale, including a systematic error estimate. I will, in particular, discuss the effects of higher-order chiral and electroweak corrections.

Date: 
Monday, March 20, 2017 - 2:00pm to 3:00pm
Location: 
CP179
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Nuclear Seminar: What is time, and how do you know?

Many of the Air Force Research Laboratory’s experimental efforts are focused on precision navigation and timing. The establishment and testing of an optical frequency standard is useful for numerous terrestrial and space based applications. Therefore, an optical atomic clock based upon a 778 nm two-photon transition in rubidium, is an excellent candidate to meet GPS-III frequency stability requirements, as commercial off-the-shelf components allow for a simple set-up that supports 7 x 10-13 at 1 second.

Date: 
Thursday, March 30, 2017 - 2:00pm to 3:00pm
Location: 
CP179
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