XENON Collaboration Research Articles

A NodeJS application for XENON collaboration member management

The Big Science projects common of multi-institute particle-physics collaborations generates unique needs for member management, including paper authorship tracking, shift assignments, subscription to mailing lists and access to 3rd party applications such as Github and Slack. For smaller collaborations under 200 people, often no facility for centralized member management is available and these needs are usually manually handled by long-term members despite the management becoming untenable as collaborations grow. To automate many of these tasks for the expanding XENON collaboration, we developed the XENONnT User Management Website, a web application that stores and updates data related to the collaboration members through the use of Node.js and MongoDB. We found that web frameworks are so mature and approachable such that a student can develop a good system to meet the unique needs of the collaboration. The application allows for the scheduling of shifts for members to coordinate between institutes. User manipulation of 3rd party applications are implemented using REST API integration. The XENONnT User Management Website is open source and is a show case of quick implementation of utility application using the web framework, which demonstrated the utility of web-based approaches for solving specific problems to aid the logistics of running Big Science collaborations.

An approximate likelihood for nuclear recoil searches with XENON1T data

The XENON collaboration has published stringent limits on specific dark matter – nucleon recoil spectra from dark matter recoiling on the liquid xenon detector target. In this paper, we present an approximate likelihood for the XENON1T 1 t-year nuclear recoil search applicable to any nuclear recoil spectrum. Alongside this paper, we publish data and code to compute upper limits using the method we present. The approximate likelihood is constructed in bins of reconstructed energy, profiled along the signal expectation in each bin. This approach can be used to compute an approximate likelihood and therefore most statistical results for any nuclear recoil spectrum. Computing approximate results with this method is approximately three orders of magnitude faster than the likelihood used in the original publications of XENON1T, where limits were set for specific families of recoil spectra. Using this same method, we include toy Monte Carlo simulation-derived binwise likelihoods for the upcoming XENONnT experiment that can similarly be used to assess the sensitivity to arbitrary nuclear recoil signatures in its eventual 20 t-year exposure.

Boosted dark matter from diffuse supernova neutrinos

The XENON collaboration recently reported an excess of electron recoil events in the low energy region with a significance of around $3.3\ensuremath{\sigma}$. An explanation of this excess in terms of thermal dark matter seems challenging. We propose a scenario where dark matter in the Milky Way halo gets boosted as a result of scattering with the diffuse supernova neutrino background. This interaction can accelerate the dark-matter to semi-relativistic velocities, and this flux, in turn, can scatter with the electrons in the detector, thereby providing a much better fit to the data. We identify regions in the parameter space of dark-matter mass and interaction cross section which satisfy the excess. Furthermore, considering the data only hypothesis, we also impose bounds on the dark-matter scattering cross section, which are competitive with bounds from other experiments.

Dark matter and the XENON1T electron recoil excess

We show that the electron recoil excess around 2 keV claimed by the Xenon collaboration can be fitted by DM or DM-like particles having a fast component with velocity of order $\sim 0.1$. Those particles cannot be part of the cold DM halo of our Galaxy, so we speculate about their possible nature and origin, such as fast moving DM sub-haloes, semi-annihilations of DM and relativistic axions produced by a nearby axion star. Feasible new physics scenarios must accommodate exotic DM dynamics and unusual DM properties.

Convolutional neural networks for direct detection of dark matter

The XENON1T experiment uses a time projection chamber (TPC) with liquid xenon to search for weakly interacting massive particles (WIMPs), a proposed dark matter particle, via direct detection. As this experiment relies on capturing rare events, the focus is on achieving a high recall of WIMP events. Hence the ability to distinguish between WIMP and the background is extremely important. To accomplish this, we suggest using convolutional neural networks (CNNs); a machine learning procedure mainly used in image recognition tasks. To explore this technique we use XENON collaboration open-source software to simulate the TPC graphical output of dark matter signals and main backgrounds. A CNN turns out to be a suitable tool for this purpose, as it can identify features in the images that differentiate the two types of events without the need to manipulate or remove data in order to focus on a particular region of the detector. We find that the CNN can distinguish between the dominant background events (ER) and 500 GeV WIMP events with a recall of 93.4%, precision of 81.2% and an accuracy of 87.2%.

Constraints on light dark matter

Writing in Physical Review Letters the XENON collaboration reports how it is pushing the limits of the XENON1T experiment, further constraining the regions where light dark matter could be lurking.

The XENON Dark Matter project: from XENON100 to XENON1T

The XENON Collaboration is searching for Dark Matter interactions in a liquid xenon target. The XENON100 detector, a dual phase xenon Time Projection Chamber employing 161 kg of liquid xenon, started the first science run at the Laboratori Nazionali del Gran Sasso in Italy in 2009. It provided limits on the spin-independent and spin-dependent interaction cross sections of Weakly Interacting Massive Particles (WIMPs), and the couplings of solar axions and galactic axion-like particles. We present these results and the status of the successor experiment, XENON1T. The new detector, currently under construction and starting data taking in 2015, will employ 3.3 tons of liquid xenon, reaching a sensitivity to spin-independent WIMP-nucleon cross section of the order of 10−47cm2.

Lowering the radioactivity of the photomultiplier tubes for the XENON1T dark matter experiment

The low-background, VUV-sensitive 3-inch diameter photomultiplier tube R11410 has been developed by Hamamatsu for dark matter direct detection experiments using liquid xenon as the target material. We present the results from the joint effort between the XENON collaboration and the Hamamatsu company to produce a highly radio-pure photosensor (version R11410-21) for the XENON1T dark matter experiment. After introducing the photosensor and its components, we show the methods and results of the radioactive contamination measurements of the individual materials employed in the photomultiplier production. We then discuss the adopted strategies to reduce the radioactivity of the various PMT versions. Finally, we detail the results from screening 216 tubes with ultra-low background germanium detectors, as well as their implications for the expected electronic and nuclear recoil background of the XENON1T experiment.

A cryogenic distillation column for the XENON1T experiment

The XENON collaboration aims for the direct detection of cold dark matter in form of weakly interacting massive particles (WIMPs). A dual phase time projection chamber filled with liquid xenon is used to detect the WIMP-nucleon interaction. For the next generation experiment XENON1T with an active target mass of 1 ton of xenon, a new distillation column to remove krypton out of xenon to a concentration of < 5 × 10−13 (0.5 ppt) natural krypton in xenon is designed and tested at the Institut für Kernphysik, Universitat Munster. The experimental setup together with two diagnostic tools is presented, as well as one stability test of a 11 hour distillation run at the designed flowrate of 3 kg per hour.

Unification of dynamical determination and bare minimal phenomenological constraints in no-scaleF−SU(5)

We revisit the construction of the viable parameter space of No-Scale $\mathcal{F}\ensuremath{-}SU(5)$, a model built on the $\mathcal{F}$-lipped $SU(5)\ifmmode\times\else\texttimes\fi{}U(1{)}_{\mathrm{X}}$ gauge group, supplemented by a pair of $\mathcal{F}$-theory derived vectorlike multiplets at the TeV scale, and the dynamically established boundary conditions of No-Scale Supergravity. Employing an updated numerical algorithm and a substantially upgraded computational engine, we significantly enhance the scope, detail and accuracy of our prior study. We sequentially apply a set of ``bare-minimal'' phenomenological constraints, consisting of i) the dynamically established boundary conditions of No-Scale Supergravity, ii) consistent radiative electroweak symmetry breaking, iii) precision LEP constraints on the light supersymmetric mass content, iv) the world average top-quark mass, and v) a light neutralino satisfying the 7-year WMAP cold dark-matter relic density measurement. The overlap of the viable parameter space with key rare-process limits on the branching ratio for $b\ensuremath{\rightarrow}s\ensuremath{\gamma}$ and the muon anomalous magnetic moment is identified as the ``golden strip'' of $\mathcal{F}\ensuremath{-}SU(5)$. A cross check for top-down theoretical consistency is provided by application of the ``Super No-Scale'' condition, which dynamically selects a pair of undetermined model parameters in a manner that is virtually identical to the corresponding phenomenological (driven primarily by the relic density) selection. The predicted vectorlike particles are candidates for production at the future LHC, which is furthermore sensitive to a distinctive signal of ultrahigh multiplicity hadronic jets. The lightest CP-even Higgs boson mass is predicted to be ${120}_{\ensuremath{-}1}^{+3.5}\text{ }\text{ }\mathrm{GeV}$, with an additional 3--4 GeV upward shift possible from radiative loops in the vectorlike multiplets. The predominantly bino flavored lightest neutralino is suitable for direct detection by the Xenon collaboration.

The XENON dark matter experiment

We report on progress of the XENON collaboration, which is developing a liquid xenon time projection chamber technology for use in a very-large-mass dark matter experiment. The collaboration is working towards demonstration of simultaneous ionization and scintillation measurement to provide strong background rejection. A 100 kg module will powerfully probe WIMP rates predicted by supersymmetry.