To make it simple… we search for dark matter!
Well, the story is complicated. Observations of the cosmic microwave background fluctuation, large-scale galaxy surveys and studies of large-scale structure formation indicate that a huge fraction of the matter in the Universe is not visible. An exotic and not yet discovered species of elementary particle would explain all these observations. Several experiments have been built in last two decades to prove the existence of these elusive particles but their detection is challenging and we do not have yet a clear picture of what they are and if they really exist.
You are right! That's what makes this field so fascinating, it is fundamental physics. Dark matter puzzle is a cutting edge science topic: 95% of the matter is dark and it is waiting for physicists to shed some light over it. Of course all this is risky but "nothing ventured, nothing gained!".
We build specialized, low-background detectors designed to identify rare and low-energy interactions, possibly induced by dark matter interacting with ordinary matter. We have been doing this by contributing to two major experimental efforts in the field: XENON1T (2015-now) and DarkSide-50 (2008-2015), respectively featuring ultrapure xenon and argon as targets for dark matter detection. Both detectors employ the so-called two-phase (gas/liquid) Time Projection Chamber (TPC) technology that allows to simultaneously detect ionization and excitation produced by even tiny energy depositions in the sensitive liquid volume.
Absolutely not! It is really challenging since the dark matter signal is expected to be really wimpy and the experimental technologies should be pushed to their edges to reach the needed sensitivities. That's why, together with the main experiments, we are running a set of smaller scale detectors that we use to study in great detail the noble liquid properties and the detection technology we are developing. These studies will play a crucial role for the interpretation of data acquired from the actual dark matter detectors.
The XENON1T two-phase xenon Time Projection Chamber (TPC) is presently deployed at Laboratori Nazionali del Gran Sasso (LNGS) and expected to be commissioned during the first few months of 2016. Thanks to its design, large fiducial mass (1 tonne fiducial), and ultra-low background, the XENON1T experiment will soon after start probing properties of dark matter in yet unexplored regions and will “open” a second phase of dark matter searches with multi-ton noble liquid detectors.
The group activities within the XENON1T program have been initially focused on the preparation and assembly of the two-phase Time Projection Chamber and on the development of the US data-processing/analysis hub - a Tier 1 Center in LHC jargon - hosted by the UChicago Research Computing Center. The XENON1T detector is presently operating within the Water Cherenkov Detector in Hall B of LNGS. The focus of the group has now switched towards data analysis with major contributions to few papers in preparation.
"Constraining the spin-dependent WIMP-nucleon cross sections with XENON1T ", E. Aprile et al. (XENON Collaboration), arXiv:1902.03234, submitted to Phys. Rev. Lett.
"First results on the scalar WIMP-pion coupling, using the XENON1T experiment", E. Aprile et al. (XENON Collaboration), arXiv:1811.12482, Accepted by Phys. Rev. Lett.
"Dark Matter Search Results from a One Ton-Year Exposure of XENON1T", E. Aprile et al. (XENON Collaboration), Phys. Rev. Lett. 121, 111302.
"First Dark Matter Search Results from the XENON1T Experiment", E. Aprile et al. (XENON Collaboration), Phys. Rev. Lett. 119, 181301.
"The XENON1T Dark Matter Experiment", E.Aprile et al. (XENON Collaboration), Eur. Phys. J. C (2017) 77: 881.
"Material radioassay and selection for the XENON1T dark matter experiment", E.Aprile et al., submitted to Eur. Phys. J. C (2017)
"Removing krypton from xenon by cryogenic distillation to the ppq level", E.Aprile et al., Eur. Phys. J. C (2017) 77: 275.
"Online 222Rn removal by cryogenic distillation in the XENON100 experiment", E.Aprile et al., Eur.Phys.J. C77 (2017) 77: 358.
"Results from a Calibration of XENON100 Using a Source of Dissolved Radon-220", E.Aprile et al., Phys. Rev. D 95, 072008 (2017)
Our research, focused on the development and operation of the dark matter detectors, is complemented by R&D activities and auxiliary measurements, designed to test new ideas for next generation detectors as well as inform analyses of presently running dark matter searches. This is accomplished by means of small experimental setups operated in our lab or on neutron beam facilities like ISNAP at Notre Dame University and TUNL at Duke University.
"Model Independent Approach to the Single Photoelectron Calibration of Photomultiplier Tubes", R.Saldanha et al., Nucl.Instrum.Meth. A863 (2017) 35-46.
"Measurement of scintillation and ionization yield and scintillation pulse shape from nuclear recoils in liquid argon", H.Cao et al., Phys.Rev. D91 (2015) 092007
"Observation of the dependence on drift field of scintillation from nuclear recoils in liquid argon", T.Alexander et al., Phys.Rev. D88 (2013) 9, 092006
We contributed to the design, operation and data analysis of the DarkSide-50 detector since its inception. DarkSide-50 is a two-phase argon Time Projection Chamber (TPC). The detector, filled with special low-radioactivity argon extracted from ancient underground gas-reservoir, has operated at LNGS since October 2013, setting strong foundations for the potential exploitation of the technique in future, large multi-ton detectors.
Phys.Rev. D93 (2016) 081101
JINST 11 (2016) P03016
Phys.Lett. B743 (2015) 456-466
Astropart.Phys. 49 (2013) 44-51
JINST 5 (2010) P05003
Nucl.Instrum.Meth. A587 (2008) 46-51
Astropart.Phys. 28 (2008) 495-507
Nucl.Instrum.Meth. A574 (2007) 83-88
@ Kavli Institute for Cosmological Physics,
@ Enrico Fermi Institute,
@ UChicago Physics Department
Research Associate @ KICP
(XENON1T, XENONnT, Noble Liquid R&D)
UChicago Graduate Student
(XENON1T, XENONnT, Noble Liquid R&D)
UChicago Graduate Student
(XENON1T, Noble Liquid R&D)
UChicago Master Student
(Noble Liquid R&D)
Senior Scientist at PNNL