After years of working on accelerator-based experiments at Fermilab and Brookhaven, in 2008 I moved to particle physics by other means.  I am currently working on two projects: the HUNTER search for sterile neutrinos, and the DarkSide direct search for dark matter.

I am currently ramping up my efforts on HUNTER.  HUNTER will search for “sterile neutrinos” which would be a new form of matter.  We start with ¹³¹Cs atoms captured in a magneto-optical trap and laser cooled to sub milliKelvin temperatures, a bit of atomic physics magic provided by our collaborators at UCLA.  ¹³¹Cs decays by electron capture.  We will look for evidence of a heavy (30-300 keV/c²) component in the emitted electron neutrino by measuring the vector momenta of all the visible particles (recoiling Xe ion, x-rays, electrons) and reconstructing the missing neutrino mass.  I am working with the Temple University group on the charged-particle spectrometers needed for this.  Assembly of the HUNTER apparatus should begin around Summer 2020.  I am looking for Princeton undergraduates to work on HUNTER this summer – please contact me.  There are also opportunities for Princeton graduate students looking to their Experimental Project.

For the past decade, I have been working with the Princeton Particle Astrophysics group (Profs. Calaprice and Galbiati) and others developing liquid argon Time Projection Chambers to detect the very-low-energy nuclear recoils from the elastic scattering of “Weakly Interacting Massive Particles” (WIMPs), a (once) promising model for the Dark Matter.  We built DarkSide-50, a 50-kg detector that has been running at LNGS since 2013.  I was in charge of the design and fabrication of the TPC, the heart of the experiment.  We found no evidence for WIMPS from 50 days of running with atmospheric argon or from 532 days of running with underground argon (which has reduced levels of ³⁹Ar, a major background).  Though designed to look for WIMPs of ~100 GeV/c² mass, we surprised everyone (including ourselves) by producing what is still the most sensitive search for dark matter particles with masses around 1 GeV/c².  Though DarkSide will continue with a much larger TPC, I am winding down my efforts on it.

Before DarkSide, I worked on the MiniBooNE, a medium-baseline neutrino experiment at Fermilab.  The Princeton group led the design and construction of this detector in 2001. You can see how the construction proceeded here.  In 2007, we reported our first oscillation results, which saw no evidence for the oscillations reported by LSND. The published analysis was the one developed by the Princeton group. In this analysis, there was an excess of electron-like events at low energies for which there is still no convincing explanation.  The experiment continued running (without our active involvement) until 2019.

Selected publications

·        "First results from the DarkSide-50 dark matter experiment at Laboratori Nazionali del Gran Sasso", P. Agnes et al., Phys. Lett. B 743, 456 (2015).  arXiv:1410.0653.

·        “DarkSide-50 532-day dark matter search with low-radioactivity argon”, P. Agnes et al., Phys. Rev. D 98, 102006 (2018).

·        “Low-Mass Dark Matter Search with the DarkSide-50 Experiment”, P. Agnes et al., Phys. Rev. Lett. 121, 081307 (2018).

·        "A Search for Electron Neutrino Appearance at the Delta m²~1 eV² Scale", A. A. Aguilar-Arevalo et al., Phys. Rev. Lett. 98, 231801 (2007). arXiv:0704.1500 [hep-ex].

·        "The MiniBooNE Detector", A.A. Aguilar-Arevalo et al.,  Nucl. Instr. Meth. A599, 28 (2009). arXiv:0806.4201 [hep-ex].