Exotic Dark Matter Detector Deep in an Italian Mountainside Picks Up Unexplained New Signal

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XENON1T Detector

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(Click image for complete view.) The XENON1T detector, tucked into an Italian mountainside to look for indications of a mystical compound called dark matter, got an unanticipated signal that might be proof of brand-new physics—or a radioactive impurity. Credit: XENON Collaboration

XENON1T information might be either proof of brand-new particle physics or unforeseen impurity.

The XENON1T detector, tucked into an Italian mountainside to look for indications of a mystical compound in deep space called dark matter, has actually gotten a brand-new bump in the information that cannot be described by existing designs.

“Dark matter makes up the vast majority of matter in the universe, but scientists still do not know the nature of this exotic material.”

An analysis of this excess signal, led by physicists from the University of Chicago, the University of California, San Diego, and the University of Zurich and vetted by the whole XENON partnership, recommends that it might be proof of brand-new physics—or an unanticipated radioactive impurity. The outcomes were revealed in a workshop on June 17, 2020.

“An excess signal is always something exciting! Sometimes you discover that the excess is just due to an unknown background, or it may be a sign of a fundamental new discovery about our universe,” stated Assoc. Prof. Luca Grandi, a research study co-author. “What we see is a solid and significant excess above our expectations; however, XENON1T is not sensitive enough to discriminate between the various potential origins.”

The XENON task is a cooperation of over 160 researchers from around the world who look for to uncover the secrets of dark matter. The group is hard at work constructing the next generation of the detector, called XENONnT. When the more delicate detector starts gathering information—possibly by the end of this year—the researchers wish to find out which of their hypotheses is accountable for the excess signal at low energies.

XENON’s look for brand-new physics

Dark matter comprises the large bulk of matter in deep space, however researchers still do not understand the nature of this unique product. It does not obstruct or release light and hardly ever connects with the normal matter that comprises whatever we can see in deep space.

To attempt to look this evasive product, researchers in the XENON partnership developed the world’s most delicate dark matter detector, XENON1T. This substantial detector, filled with over 3 lots of liquid xenon, is safeguarded from radiation by a three-story-tall tank of ultra-pure water and housed in an underground lab below a mountain at Gran Sasso National Laboratory in Italy.

Luca Grandi and Jacques Pienaar

Physicists Luca Grandi (left) and Jacques Pienaar help with the building and construction of the XENONnT, an ingenious upgrade to the world’s most delicate dark matter detector. Credit: XENON Collaboration

Within this distinctively beautiful environment, an instrument called a time forecast chamber keeps an eye on signals of light and electrical charge that are set off whenever a subatomic particle connects with the swimming pool of xenon. If a particle of dark matter run into a xenon atom, it must in theory appear in the information. Though the chamber, developed and preserved with the assistance of UChicago researchers, is exceptionally delicate, these interaction occasions are exceptionally unusual—it takes almost a year to gather adequate information for a comprehensive research study.

XENON1T’s xenon-filled chamber is made from exceptionally high pureness products, however there is still an inevitable level of background radiation from the products that comprise the detector itself.

“We do a ton of analysis to predict what backgrounds are present in the detector, along with their expected rates and energies,” stated UChicago college student Evan Shockley, among 3 matching authors of the research study.  “Then we can compare these predictions with the data and see if they agree.”

But upon mindful factor to consider of the information, Shockley and his associates concluded the signal was above the anticipated background at low energies and might not be described by any existing designs or recognized sources of contamination.

There were 53 unusual occasions over the year-long experiment—adequate to be considerable, however insufficient to compare a background impurity or a physics advancement.

“When you push to the edge of your detector’s sensitivity in the search for these elusive particles you sometime bump into unexpected backgrounds that you hadn’t previously accounted for,” stated Grandi. “XENONnT, the larger detector that we are preparing for operation, should shed some light on this and help us discriminate among the various explanations.”

The possible prospects

The XENON1T detector was developed mainly to look for signals that might suggest the presence of among the leading prospects for what dark matter may appear like—big, heavy particles, referred to as weakly connecting enormous particles (Pushovers).

Physicist Luca Grandi

Grandi operates in ultra-clean conditions to finish the building and construction of the XENONnT’s time forecast chamber. Credit: XENON Collaboration

But this ultra-sensitive detector might likewise get other signals that might teach us about deep space. Two possibilities for the signal they saw would be a theoretical particle from the sun called a solar axion; or particles called neutrinos likewise originating from the sun, however with unforeseen magnetic attributes. If this measurement does represent either of these unique particles, it would be an innovative finding and address a few of the most popular concerns about the physics of our universe.

“Our data supports the solar axion hypothesis most strongly. However, if we did indeed observe solar axion interactions, the properties of the axions we observed would be in contrast with results from astrophysical observations,” stated Grandi.

But another possibility is that the signal is really connected to an unanticipated impurity in the detector. The excess signal, Shockley described, looks comparable to the energy pattern developed by the radioactive decay of tritium. “Tritium is a hydrogen atom with two neutrons,” he stated. “It’s not very common. But since our detector is so sensitive, the presence of even a few tritium atoms in the detector could result in an excess like the one we observed.” (He and his fellow scientists had not formerly searched for tritium contamination, due to the fact that tritium is so unusual that it was believed not likely to exist in their ultrapure products.)

It’s too near inform which one it is with the existing information, however Grandi and his group might get conclusive responses when the XENON partnership’s most recent dark matter detector, XENONnT, ends up being functional later on this year.

XENONnT upgrade for greater level of sensitivity

At the minute, XENON1T is currently the world’s most delicate dark matter detector. To press its abilities even further, Grandi’s group and UChicago research study engineer supervisor Ben Stillwell developed enhancements to the detector that will add to a boost in its level of sensitivity by an aspect of 10. The updated XENONnT detector will finish measurements quicker and with much better signal quality.

“To increase the sensitivity, we have increased the size of the detector to allow for three times more xenon. We’ve also done a lot of work to carefully select the materials that we use and further refined the detector design to reduce the background,” described Jacques Pienaar, UChicago postdoc and the analysis organizer for XENON1T and XENONnT.

Pienaar and Grandi invested the early part of 2020 at Gran Sasso leading the building and construction of XENONnT’s time forecast chamber. With the risk of COVID-19 growing in Italy, they handled to finish the building and construction of the brand-new detector simply a couple of days into the quarantine lockdown. The detector is now in a steady, tidy condition and the last preparations will happen later on this year.

Reference: “Observation of Excess Electronic Recoil Events in XENON1T” by E. Aprile, J. Aalbers, F. Agostini, M. Alfonsi, L. Althueser, F. D. Amaro, V. C. Antochi, E. Angelino, J. R. Angevaare, F. Arneodo, D. Barge, L. Baudis, B. Bauermeister, L. Bellagamba, M. L. Benabderrahmane, T. Berger, A. Brown, E. Brown, S. Bruenner, G. Bruno, R. Budnik, C. Capelli, J. M. R. Cardoso, D. Cichon, B. Cimmino, M. Clark, D. Coderre, A. P. Colijn, J. Conrad, J. P. Cussonneau, M. P. Decowski, A. Depoian, P. Di Gangi, A. Di Giovanni, R. Di Stefano, S. Diglio, A. Elykov, G. Eurin, A. D. Ferella, W. Fulgione, P. Gaemers, R. Gaior, M. Galloway, F. Gao, L. Grandi, C. Hasterok, C. Hils, K. Hiraide, L. Hoetzsch, J. Howlett, M. Iacovacci, Y. Itow, F. Joerg, N. Kato, S. Kazama, M. Kobayashi, G. Koltman, A. Kopec, H. Landsman, R. F. Lang, L. Levinson, Q. Lin, S. Lindemann, M. Lindner, F. Lombardi, J. Long, J. A. M. Lopes, E. Lopez Fune, C.Macolino, J. Mahlstedt, A. Mancuso, L. Manenti, A. Manfredini, F. Marignetti, T. Marrodan Undagoitia, K. Martens, J. Masbou, D. Masson, S. Mastroianni, M. Messina, K. Miuchi, K. Mizukoshi, A. Molinario, K. Mora, S. Moriyama, Y. Mosbacher, M. Murra, J. Naganoma, K. Ni, U. Oberlack, K. Odgers, J. Palacio, B. Pelssers, R. Peres, J. Pienaar, V. Pizzella, G. Plante, J. Qin, H. Qiu, D. Ramirez Garcia, S. Reichard, A. Rocchetti, N. Rupp, J. M. F. dos Santos, G. Sartorelli, N. Sarcevic, M. Scheibelhut, J. Schreiner, D. Schulte, M. Schumann, L. Scotto Lavina, M. Selvi, F. Semeria, P. Shagin, E. Shockley, M. Silva, H. Simgen, A. Takeda, C. Therreau, D. Thers, F. Toschi, G. Trinchero, C. Tunnell, M. Vargas, G. Volta, H. Wang, Y. Wei, C. Weinheimer, M. Weiss, D. Wenz, C. Wittweg, Z. Xu, M. Yamashita, J. Ye, G. Zavattini, Y. Zhang, T. Zhu, and J. P. Zopounidis (XENON Collaboration) and X. Mougeot, 17 June 2020.
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