Latest XENON1T results at ICHEP2018 in Seoul

The XXXIX International Conference on High Energy Physics (ICHEP2018) was taking place from July 4 – 11, 2018 in Seoul, Korea. After a warm welcome in this modern and traditional metropolis with over 10 million citizens, I was invited to present the recent results from XENON1T in a Dark Matter parallel session.

Here is one slide of my talk visualizing the spatial distribution of the unblinded and de-salted events.

Spatial distribution of unblinded and de-salted data.

The left plot shows the X- and Y- distribution, while the right plot indicates the radius R versus depth Z for the same set of data. The enlarged fiducial volume of 1.3 tons with respect to the first result, is highlighted by the pink line. For the analysis, a core volume (green line) was defined to distinguish WIMP-like events over neutron-like background events. The different events are visualized by pie charts, where the color code resembles the relative probability from each background component assigned by the best-fit. The larger a pie is, the more “WIMPy” it is. As you can see, only a few “WIMPy” events were found that are comparable to the background model expectations. From this, we derived the most stringent limits on spin-independent WIMP-nucleon cross sections.

At the end of my talk,  I also reported on the status of XENONnT, which will feature a 10x higher sensitivity than XENON1T. One main task is radon mitigation, one of the dominant backgrounds, which is visualized in this slide.

Radon mitigation for XENONnT

In a first step, a careful material selection needs to be made to avoid radon emanation from the start. Then, a new high throughput radon distillation column is under development to further reduce the radon contribution. Additionally, a new custom-made radon-free magnetically-coupled piston pump was built and installed at XENON1T in June 2018. With that, the radon budget in XENON1T was reduced by almost half (45%), which is an important step for the future XENONnT experiment.

The full talk is publicly available here.

XENON talk at Patras Workshop

A talk on the XENON project was given at the 15th Patras Workshop on Axions, WIMPs and WISPs, which was held in Freiburg (Germany) in the first week of June. Andrea Molinario from the Gran Sasso Science Institute and Laboratori Nazionali del Gran Sasso presented the most recent results from the data analysis of XENON1T, in particular the search for WIMP-nucleon spin-dependent and spin-independent interactions. The sensitivity of this search will be much-improved upon by the upcoming XENONnT phase of the experiment.

The first observation of 124Xe double electron capture and the measurement of the half-life of the process were also shown (this topic had a dedicated talk by Sebastian Lindemann). In the second part of his talk, Andrea gave an update on the status of XENONnT. The presentation is available here.

XENON1T talk at Low Radioactivity Technique 2019

Our latest XENON1T paper on details of our analysis was presented at the Low Radioactivity Techniques, a conference focused on low background experiments. In the talk (that you can find here), the response model of the detector, the challenges of background modeling, as well as the used techniques were described. In a low background experiment is often hard to asses the expected distribution of events due to lack of statistics and to many subtle effects. In the talk a novel technique was described to introduce a well-motivated systematic uncertainty to the background model based on a calibration sample, which can be relevant to other low background experiments.

XENON on skis

XENON was present at the ALPS conference in Austria. Chiara Capelli from University of Zurich gave a talk on behalf of the XENON collaboration. The talk focused on the latest XENON1T results on spin-independent and spin-dependent WIMPs, and on the newest results on two-neutrinos double electron capture, with a final status on the XENONnT upgrade. The talk is available here.

On March 8, 2019, Shigetaka Moriyama presented the status of the XENONnT experiment at the international symposium on “Revealing the history of the Universe with underground particle and nuclear research” in Sendai, Japan. The symposium is held by a Japanese research community working on underground experiments and developing low background techniques. Its members are interested in the physics goals of XENONnT as well as its radon reduction technique and will enhance the experiment with Super-Kamiokande’s water Cherenkov technology developed in Kamioka, Japan, for the SK-Gd project. Super-Kamiokande developed this technology to measure the diffuse relic neutrino flux from past supernovae.

At the Sendai meeting, this community is summarizing its achievements over last five years and aims to secure new funding for the next five years by expanding its activity through internationalization and the inclusion of new physics topics such as history of stars, galaxies, and the origin of the heavy elements in the Universe.

Its HP is here and the slides are available here.

Outline the XENONnT Computing Scheme at the 2nd Rucio Community Workshop in Oslo

Oslo welcomed all 66 participants of the second Rucio Community Workshop with pleasant weather and a venue which offered an astonishing view about the capital of Norway.
The opensource and contribution model of the Rucio data management tool captures more and more attention from numerous fields. Therefore, 21 communities reported this year about the implementation of Rucio in their current data workflows, discussed with the Rucio developing team possible improvements and chatted among each other during the coffee breaks to learn from others experiences. Among the various communities were presentations given by the DUNE experiment, Belle-2 and LSST. The XENON Dark Matter Collaboration presented the computing scheme of the upcoming XENONnT experiment. Two keynote talks from Richard Hughes-Jones (University of Maryland) and Gundmund Høst (NeIC) highlighted the concepts of the upcoming generation of academic networks and the Nordic e-Infrastructure Collaboration.

After the successful XENON1T stage with two major science runs, a world-leading limit for spin-indepenent Dark Matter interactions with nucleons and further publications, the XENON1T experiment stopped data taking in December 2018. We aim for two major updates for the successor stage of XENONnT: a larger time projection chamber (TPC) which holds ~8,000 kg of liquid xenon with 496 PMTs for signal readout and an additional neutron veto detector based on Gadolinium doped water in our water tank. That requires upgrades in our current data management and processing scheme, which was presented last year at the first Rucio Community Workshop. Fundamental change is the new data processor STRAX which allows us much faster data processing. Based on the recorded raw data, the final data product will be available at distinct intermediate processing stages which depend on each other. Therefore, we stop using our “classical” data scheme of raw data, processed data and minitrees, and instead aim for a more flexible data structure. Nevertheless, all stages of the data are distributed with Rucio to connected grid computing facilities. STRAX will be able to process data from the TPC, the MuonVeto and the NeutronVeto together to allow coincident analysis.

The data flow of the XENONnT experiment

The data flow of the XENONnT experiment. A first set data is processed already at the LNGS. All data kinds are distributed with Rucio to the analysts.

Reprocessing campaigns are planed ahead with HTCondor and DAGMan jobs at EGI and OSG similar to the setup of XENON1T. Due to the faster data processor, it becomes necessary to outline a well-established read and write routine with Rucio to guarantee quick data access.
Another major update in the XENONnT computing scheme becomes the tape backup location. Because of the increased number of disks and tape allocations in the Rucio catalogue, we will abandon the Rucio independent tape backup in Stockholm and use dedicated Rucio storage elements for storing the raw data. The XENON1T experiment collected ~780 TB of (raw) data during its life time which are all managed by Rucio. The XENON Collaboration is looking forward to continuing this success story with XENONnT

XENON1T at Lake Louise

Physics meets winter sports at the Lake Louise Winter Institute, a particle physics conference held annually in the beautiful Canadian Rockies. On February 12, 2019, Evan Shockley from University of Chicago presented at the conference on behalf of the XENON collaboration. The talk focused on the latest, world-leading WIMP results, and included a status update on XENON1T and its imminent upgrade, XENONnT. The talk is available here.

XENONnT will feature a larger detector and even lower background than XENON1T, making it ~10 times more sensitive to interactions from dark matter and other rare processes. With installation coming later this year, it’s an exciting time for the XENON collaboration and the field of dark matter research!


XENON1T at the annual meeting of the Swiss Physical Society, 2018

Two members of the University of Zurich group gave talks on XENON1T at the annual meeting of the Swiss Physical Society in Lausanne, Switzerland. Chiara Capelli presented the latest news from the experiment and in particular the recently presented limit on spin-independent WIMP-nucleon cross-section, while Adam Brown spoke about the ongoing work searching for the inelastic scattering of WIMPs.

One of the key slides from Chiara’s talk is below. In the top-right you can see the WIMP-search data pre-unblinding, and in the bottom-right the efficiency for detecting nuclear recoils which happen in our fiducial volume. In the full talk, which is available here, she also presented the final limit and then gave a update on the preparations for the detector upgrade to XENONnT which are ongoing at the University of Zurich.

Adam’s talk focussed instead on an alternative possibility of searching for WIMPs via their inelastic scattering off xenon nuclei. During the interaction the nucleus is excited, and so the usual nuclear recoil signal would be observed in coincidence with the 39.6 keV gamma ray from the de-excitation of the nucleus. One of the attractions of this search channel, which is however less sensitive than elastic scattering, is that it distinguishes between spin-dependent and spin-independent WIMP interactions: a spin-dependent interaction is needed to change the nuclear spin state during its excitation. Again, the full talk is available online here.

XENON1T At Dark Matter Summer School 2018

Some of our young collaboration members attended a Dark Matter Summer School at the University of Albany from July 16th through the 20th.

XENON1T at DMSS 2018Featured from left to right: Kelly Odgers, Chloé Therreau, Amanda Depoian, Abigail Kopec, Dr. Ethan Brown, Arianna Rocchetti, Matthew Bernstein, and Leaf Swordy.

They obtained a broader understanding of the current state of Dark Matter research; especially cosmological and astrophysical evidence for Dark Matter; the best-motivated theoretical dark matter particle models; and various detection techniques. It was also an opportunity for them to meet and connect with their colleagues in the field and hone presentation skills. More information and uploaded talk slides can be found at

XENON1T Talk at NDM 2018

On July 2nd, 2018, Kaixuan Ni of UC San Diego presented the recent results and the current status of the XENON1T experiment at the 6th Symposium on Neutrinos and Dark Matter in Nuclear Physics (NDM 2018) in Daejeon, Korea. The recent released results from XENON1T set the world’s most stringent limits on the WIMP-nucleon spin-independent interactions for all WIMP masses above 6 GeV. The detector currently keeps taking dark matter search data with improved detector performance and with reduced background. An upgrade of the detector to XENONnT is scheduled in 2019. With a total of 8-tonnes of liquid xenon, XENONnT will boost the dark matter search sensitivity by a factor of 10 and is targeting at dark matter candidates from the supersymmetric models.