Dark Matter Detective Work: XENONnT's Insights
Scientists use advanced detectors to find signs of dark matter.
XENON Collaboration, E. Aprile, J. Aalbers, K. Abe, S. Ahmed Maouloud, L. Althueser, B. Andrieu, E. Angelino, D. Ant, F. Arneodo, L. Baudis, M. Bazyk, L. Bellagamba, R. Biondi, A. Bismark, K. Boese, A. Brown, G. Bruno, R. Budnik, C. Cai, C. Capelli, J. M. R. Cardoso, A. P. Cimental Ch, A. P. Colijn, J. Conrad, J. J. Cuenca-Garc, V. D'Andrea, L. C. Daniel Garcia, M. P. Decowski, A. Deisting, C. Di Donato, P. Di Gangi, S. Diglio, K. Eitel, S. el Morabit, A. Elykov, A. D. Ferella, C. Ferrari, H. Fischer, T. Flehmke, M. Flierman, W. Fulgione, C. Fuselli, P. Gaemers, R. Gaior, M. Galloway, F. Gao, S. Ghosh, R. Giacomobono, R. Glade-Beucke, L. Grandi, J. Grigat, H. Guan, M. Guida, P. Gyorgy, R. Hammann, A. Higuera, C. Hils, L. Hoetzsch, N. F. Hood, M. Iacovacci, Y. Itow, J. Jakob, F. Joerg, Y. Kaminaga, M. Kara, P. Kavrigin, S. Kazama, P. Kharbanda, M. Kobayashi, D. Koke, A. Kopec, H. Landsman, R. F. Lang, L. Levinson, I. Li, S. Li, S. Liang, Z. Liang, Y. -T. Lin, S. Lindemann, M. Lindner, K. Liu, M. Liu, J. Loizeau, F. Lombardi, J. Long, J. A. M. Lopes, T. Luce, Y. Ma, C. Macolino, J. Mahlstedt, A. Mancuso, L. Manenti, F. Marignetti, T. Marrod, K. Martens, J. Masbou, E. Masson, S. Mastroianni, A. Melchiorre, J. Merz, M. Messina, A. Michael, K. Miuchi, A. Molinario, S. Moriyama, K. Mor, Y. Mosbacher, M. Murra, J. M, K. Ni, U. Oberlack, B. Paetsch, Y. Pan, Q. Pellegrini, R. Peres, C. Peters, J. Pienaar, M. Pierre, G. Plante, T. R. Pollmann, L. Principe, J. Qi, J. Qin, D. Ram, M. Rajado, R. Singh, L. Sanchez, J. M. F. dos Santos, I. Sarnoff, G. Sartorelli, J. Schreiner, P. Schulte, H. Schulze Eißing, M. Schumann, L. Scotto Lavina, M. Selvi, F. Semeria, P. Shagin, S. Shi, J. Shi, M. Silva, H. Simgen, C. Szyszka, A. Takeda, Y. Takeuchi, P. -L. Tan, D. Thers, F. Toschi, G. Trinchero, C. D. Tunnell, F. T, K. Valerius, S. Vecchi, S. Vetter, F. I. Villazon Solar, G. Volta, C. Weinheimer, M. Weiss, D. Wenz, C. Wittweg, V. H. S. Wu, Y. Xing, D. Xu, Z. Xu, M. Yamashita, L. Yang, J. Ye, L. Yuan, G. Zavattini, M. Zhong
― 5 min read
Table of Contents
In the realm of physics, especially when dealing with the mysterious and elusive dark matter, scientists are constantly on the lookout for clever ways to detect it. Imagine a world where the invisible rules everything around us, hiding just out of reach. It's like a magic trick that scientists are trying to figure out. Well, that’s what dark matter is—it's believed to make up about 27% of the universe, yet we have no idea what it actually is.
One of the tools in this great cosmic detective work is a special detector named XENONnT. This device is designed to catch the hints of dark matter interacting with ordinary matter (that's us!). But there’s a catch: these interactions involve very weak signals, especially when we talk about low-energy events. This is where the excitement truly begins.
What is XENONnT?
XENONnT is an advanced experiment that uses a large tank filled with liquid xenon—a rare, noble gas. It uses this gas to look for signs of dark matter, specifically weakly interacting massive particles, also known as WIMPs. These particles are theorized to be very heavy and to interact very weakly with regular matter. To catch a glimpse of these WIMPs, XENONnT is designed to detect scintillation light and ionization electrons that are produced when particles interact with the xenon.
The Challenge of Low-Energy Events
Detecting low-energy Nuclear Recoils is crucial for the success of dark matter detectors like XENONnT. These recoils occur when dark matter particles hit a nucleus in the xenon atom, causing it to move—much like a pool ball being struck by a cue ball. The energy from these interactions can be very low, often around 0.5 keV to 5 keV, making them difficult to spot.
Think of it this way: it’s akin to searching for a needle in a haystack, but the needle is invisible, and the haystack is also filled with various bits of junk that can confuse your search.
Enter the Yttrium-Beryllium Photoneutron Source
To better understand these soft whispers of dark matter, researchers turned to a clever tool called a Yttrium-Beryllium (YBe) photoneutron source. This device can produce neutrons with a specific energy that mimics the conditions of a dark matter interaction. By using these neutrons, scientists can calibrate the XENONnT detector to ensure it can accurately measure the low-energy events it is designed to detect.
This calibration process is essential. Without it, the detector's readings could be as reliable as a weather forecast in a tornado. Scientists need to know exactly how the detector will respond to different energies to separate the true signals from background noise.
How Does It Work?
The YBe source works by producing quasi-monoenergetic neutrons through a process called photodisintegration. In layman's terms, this means it uses gamma rays from Yttrium decays to break apart Beryllium atoms, releasing neutrons in the process. These neutrons then enter the XENONnT detector to calibrate its response to low-energy recoils.
During an experiment, scientists placed the YBe source near the detector and counted how many interactions occurred. They were on the lookout for two types of signals: scintillation light (which happens during an interaction) and ionization electrons (which drift upwards in the liquid xenon).
The Events
During their data collection, scientists amassed a whopping 474 events from 183 hours of watching the detector work. Of these events, they had to carefully sift through the data to find the meaningful signals among the accidental coincidences that would arise from background noise.
It’s like trying to find a good song on the radio while someone is continuously changing the station. Frustrating, but when you find that one good track, it makes it all worthwhile!
The Process of Selection
After gathering data, the tricky part began. Researchers had to filter through the events to pick out the nuclear recoils caused by the neutrons. They used a combination of techniques, including modeling the expected background events and employing a boosted decision tree classifier, which is a fancy term for a method that helps distinguish between different types of signals based on certain characteristics.
This classifier acts like a really smart bouncer at a party. It lets in the good guests (the nuclear recoils) while turning away those who don’t belong (the background noise). The result was a refined selection of events that accurately represented the nuclear recoils they were looking for.
The Results
The results from this massive undertaking led to the extraction of important calibration values, specifically the light yield (how many photons are produced) and the charge yield (how many electrons are produced) per keV of energy deposition in liquid xenon. These yield values are crucial for interpreting future data collected by the XENONnT detector regarding possible dark matter interactions.
The researchers were happy to find that their measurements lined up with existing models used in other experiments, showing consistency and confirming that their calibration process worked effectively. It was as if they had found the right key to unlock a door they had been trying to open for years.
Conclusion: A Bright Future
The calibration carried out using the YBe source allowed the XENONnT team to measure low-energy recoils down to about 0.5 keV. This achievement is significant; it paves the way for future discoveries in the field of dark matter and opens doors to understanding other rare low-energy interactions.
As the scientific community continues to probe the depths of dark matter, techniques like this calibration will be indispensable. Who knows? With each step, we might be getting closer to unveiling some of the universe’s biggest secrets, all thanks to clever experiments and a little bit of neutron magic.
So, the next time you hear chatter about dark matter, just remember—behind the scenes, scientists like to play with photons, neutrons, and a little bit of wizardry, all in the quest to understand the universe better. And who wouldn't want to be part of that adventure?
Original Source
Title: Low-Energy Nuclear Recoil Calibration of XENONnT with a $^{88}$YBe Photoneutron Source
Abstract: Characterizing low-energy (O(1keV)) nuclear recoils near the detector threshold is one of the major challenges for large direct dark matter detectors. To that end, we have successfully used a Yttrium-Beryllium photoneutron source that emits 152 keV neutrons for the calibration of the light and charge yields of the XENONnT experiment for the first time. After data selection, we accumulated 474 events from 183 hours of exposure with this source. The expected background was $55 \pm 12$ accidental coincidence events, estimated using a dedicated 152 hour background calibration run with a Yttrium-PVC gamma-only source and data-driven modeling. From these calibrations, we extracted the light yield and charge yield for liquid xenon at our field strength of 23 V/cm between 0.5 keV$_{\rm NR}$ and 5.0 keV$_{\rm NR}$ (nuclear recoil energy in keV). This calibration is crucial for accurately measuring the solar $^8$B neutrino coherent elastic neutrino-nucleus scattering and searching for light dark matter particles with masses below 12 GeV/c$^2$.
Authors: XENON Collaboration, E. Aprile, J. Aalbers, K. Abe, S. Ahmed Maouloud, L. Althueser, B. Andrieu, E. Angelino, D. Ant, F. Arneodo, L. Baudis, M. Bazyk, L. Bellagamba, R. Biondi, A. Bismark, K. Boese, A. Brown, G. Bruno, R. Budnik, C. Cai, C. Capelli, J. M. R. Cardoso, A. P. Cimental Ch, A. P. Colijn, J. Conrad, J. J. Cuenca-Garc, V. D'Andrea, L. C. Daniel Garcia, M. P. Decowski, A. Deisting, C. Di Donato, P. Di Gangi, S. Diglio, K. Eitel, S. el Morabit, A. Elykov, A. D. Ferella, C. Ferrari, H. Fischer, T. Flehmke, M. Flierman, W. Fulgione, C. Fuselli, P. Gaemers, R. Gaior, M. Galloway, F. Gao, S. Ghosh, R. Giacomobono, R. Glade-Beucke, L. Grandi, J. Grigat, H. Guan, M. Guida, P. Gyorgy, R. Hammann, A. Higuera, C. Hils, L. Hoetzsch, N. F. Hood, M. Iacovacci, Y. Itow, J. Jakob, F. Joerg, Y. Kaminaga, M. Kara, P. Kavrigin, S. Kazama, P. Kharbanda, M. Kobayashi, D. Koke, A. Kopec, H. Landsman, R. F. Lang, L. Levinson, I. Li, S. Li, S. Liang, Z. Liang, Y. -T. Lin, S. Lindemann, M. Lindner, K. Liu, M. Liu, J. Loizeau, F. Lombardi, J. Long, J. A. M. Lopes, T. Luce, Y. Ma, C. Macolino, J. Mahlstedt, A. Mancuso, L. Manenti, F. Marignetti, T. Marrod, K. Martens, J. Masbou, E. Masson, S. Mastroianni, A. Melchiorre, J. Merz, M. Messina, A. Michael, K. Miuchi, A. Molinario, S. Moriyama, K. Mor, Y. Mosbacher, M. Murra, J. M, K. Ni, U. Oberlack, B. Paetsch, Y. Pan, Q. Pellegrini, R. Peres, C. Peters, J. Pienaar, M. Pierre, G. Plante, T. R. Pollmann, L. Principe, J. Qi, J. Qin, D. Ram, M. Rajado, R. Singh, L. Sanchez, J. M. F. dos Santos, I. Sarnoff, G. Sartorelli, J. Schreiner, P. Schulte, H. Schulze Eißing, M. Schumann, L. Scotto Lavina, M. Selvi, F. Semeria, P. Shagin, S. Shi, J. Shi, M. Silva, H. Simgen, C. Szyszka, A. Takeda, Y. Takeuchi, P. -L. Tan, D. Thers, F. Toschi, G. Trinchero, C. D. Tunnell, F. T, K. Valerius, S. Vecchi, S. Vetter, F. I. Villazon Solar, G. Volta, C. Weinheimer, M. Weiss, D. Wenz, C. Wittweg, V. H. S. Wu, Y. Xing, D. Xu, Z. Xu, M. Yamashita, L. Yang, J. Ye, L. Yuan, G. Zavattini, M. Zhong
Last Update: 2024-12-11 00:00:00
Language: English
Source URL: https://arxiv.org/abs/2412.10451
Source PDF: https://arxiv.org/pdf/2412.10451
Licence: https://creativecommons.org/licenses/by/4.0/
Changes: This summary was created with assistance from AI and may have inaccuracies. For accurate information, please refer to the original source documents linked here.
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