Seminars and Colloquia

Title Speaker Location Abstract Material
Developing Cyclotron Radiation Emission Spectroscopy, a novel technique for nuclear physics Ben LaRoque (University of California at Santa Barbara) CENPA Conference Room NPL-178

Cyclotron Radiation Emission Spectroscopy is a new approach to measuring electron energies being actively developed by the Project 8 collaboration. The technique determines the energy of individual electrons by observing the changes in their cyclotron frequency resulting from their relativistic mass shifts. Our first demonstration of the methodology was made in 2014 and we have been working since then to evaluate and enhance the performance. Here I will review the principles of CRES and the experimental milestones achieved thus far. I will also briefly discuss progress towards using CRES for nuclear physics applications and specifically direct neutrino mass measurement in Project 8.

Development of low background detectors for high sensitivity measurements. Elena Sala CENPA Conference Room NPL-178

In the field of rare physics events experiments the background reduction plays an important role to distinguish the feeble signal under study above the background. Low level counting techniques are continuously under development to improve the measurement sensitivity. In my presentation I will summarise my contribution in the development and optimisation of both detectors and methods for high sensitivity measurements. I will focus on three main projects I have finalised during my career up to now using germanium detectors. The projects have different purposes spacing from material screening and selection for rare events experiments, to the investigation on natural and artificial radioactivity until the rare decay searches. They are a gamma-gamma coincidence spectrometer, the optimisation of a BEGe detector and the development of a HPGe Array. I will then present the duties and the achievements I reached during my current researcher position.

Measuring g-2 of the electron and positron to test the Standard Model’s most precise prediction. Elise Novitski (Harvard University) CENPA Conference Room NPL-178
Identification of Single Barium Atoms for the nEXO Neutrinoless Double Beta Decay Experiment Scott W. Kravitz (Stanford University) CENPA Conference Room NPL-178

nEXO is a next-generation experiment designed to search for neutrinoless double beta decay of xenon-136 in a liquid xenon time projection chamber. Positive observation of this decay would determine the neutrino to be a Majorana particle, as well as measure the absolute neutrino mass scale. In order to greatly reduce background contributions to this search, the collaboration is developing several "barium tagging'' techniques to recover and identify the decay daughter, barium-136. Barium tagging may be available for a second phase of nEXO operation, allowing for neutrino mass sensitivity beyond the inverted mass hierarchy. Tagging methods for this phase include barium-ion capture on a probe with identification by resonance ionization laser spectroscopy (RIS). An apparatus has been built to deposit barium atoms onto a surface and recover them using infrared laser desorption followed by RIS, with the resulting ions passing through a time-of-flight mass spectrometer for further identification. Recent results from this system will be presented, including those from incorporating an argon ion gun which allows for improved cleaning and preparation of the barium deposition substrate.

Electric Dipole Moment Measurements at Storage Rings Jörg Pretz, RWTH Aachen University & Forschungszentrum Jülich CENPA Conference Room NPL-178

The Electric Dipole Moment (EDM) of elementary particles, including hadrons, is considered as one of the most powerful tools to study the combined violation of charge conjugation (C) and parity (P) symmetry beyond the Standard Model. Such CP violating mechanisms are required to explain the dominance of matter over anti-matter in our universe.

Up to now experiments concentrated on neutral systems, namely neutron, atoms and molecules. Storage rings offer the possibility to measure EDMs of charged particles by observing the influence of the EDM on the spin motion. The Cooler Synchrotron COSY at the Forschungszentrum Jülich provides polarized protons and deuterons up to a momentum of 3.7 GeV/c making it an ideal starting point for such an experimental programme. Plans for measurements of charged hadron EDMs and results of first test measurements will be presented.

Preparing for Advanced LIGO's second observation run and beyond Jenne Driggers from the LIGO Hanford Observatory CENPA Conference Room NPL-178

<p>Advanced LIGO made the first direct detection of gravitational waves during its first observation period, which ended in January 2016. Since then, the interferometers have been undergoing a series of upgrades to improve their sensitivity to various potential gravitational wave sources. I will describe several of these improvements, and how they will enhance our sensitivity to events such as massive black holes at lower frequencies and mergers involving neutron stars at higher frequencies, as well as facilitate tests of general relativity with higher signal-to-noise ratio detections. I will conclude with an outlook on future upgrades that may be added after the next observing run, to further improve our ability to detect gravitational waves.</p>

Search for low-mass dark matter with the CRESST experiment Michael Willers, Technical University of Munich CENPA Conference Room NPL-178

The CRESST (Cryogenic Rare Event Search with Superconducting Thermometers) experiment, located in the Gran Sasso underground laboratory (LNGS, Italy) aims at the direct detection of dark matter (DM) particles. Scintillating CaWO4 crystals operated as cryogenic detectors are used as target material for DM-nucleus scattering. The simultaneous measurement of the phonon signal from the CaWO4 crystal and the emitted scintillation light in a separate cryogenic light detector is used to discriminate backgrounds from a possible dark matter signal. Since cryogenic detectors are very sensitive to small energy deposits induced, e.g., by the interactions of light DM particles, the experiment is able probe the low-mass region of the parameter space for spin-independent DM-nucleus scattering with high sensitivity.

Recent results from the CRESST-II experiment — obtained using a 300 g detector with a nuclear recoil energy threshold of 307 eV — provide the world best limit for masses below 1.7 GeV/c^2. The CRESST-III experiment aims to significantly improve the sensitivity for low-mass DM particles by using dedicated detector modules. Each such module consists of a ~24 g CaWO4 target crystal and a 20x20 mm^2 Silicon-on-Sapphire light detector and will allow us to reach a nuclear recoil energy threshold of ~100 eV.

Phase 1 of the CRESST-III experiment, where 10 detector modules with a total target mass of 240 g will be operated, recently started its commissioning phase and data taking is expected to start in the summer of 2016. In this talk I will present the most recent results from the CRESST-II experiment as well as the status and future perspectives of the CRESST-III experiment.

Ultra Light Dark Matter and How to Detect It William Terrano, Technical University of Munich CENPA Conference Room NPL-178

<p>Recent theoretical advances show that the parameter space of well-motivated dark matter candidates is much larger than previously thought. I will discuss the nature of these very light dark matter fields and the physical effects it would produce. These effects suggest new techniques are needed to detect this class of dark matter. Promising technologies range from torsion balances to atomic-clocks, co-magnetometers and resonant-cavities.</p>