Neutrinos may be the key to finally solving a mystery of the origins of our matter-dominated universe, 并准备了两大, billion-dollar experiments are underway to reveal the particles' secrets.
现在, 一组核物理学家, including recent 最靠谱的网赌软件 graduate student Mariana Khachatryan, have turned to the electron to provide insight for how these experiments can better prepare to capture critical information. 他们的研究是在美国国立卫生研究院进行的.S. Department of Energy's Thomas Jefferson National Accelerator Facility and 最近发表在《网上十大网赌娱乐大全》杂志上, reveals that major updates to neutrino models are needed for the experiments to achieve high-precision results.
Neutrinos are ubiquitous, generated in copious numbers by stars throughout our universe. But these particles rarely interact with matter, making them difficult to study.
"There is this phenomenon of neutrinos changing from one type to another, 这种现象被称为中微子振荡. 研究这种现象很有趣, 因为它还没有被很好地理解,哈查特里安说, a co-lead author on the study who was a member of Professor and Eminent Scholar Larry Weinstein's research group when she contributed to the research. She is now a postdoctoral research associate at Florida 国际 University.
研究中微子振荡的一种方法是建造巨大的, 超灵敏的探测器来测量地下深处的中微子. The detectors typically contain dense materials with large nuclei, 所以中微子更有可能与它们相互作用. Such interactions trigger a cascade of other particles that are recorded by the detectors. Physicists can use that data to tease out information about the neutrinos.
“探测器是由重核组成的, and the interactions of neutrinos with these nuclei are actually very complicated interactions,阿迪·阿什肯纳兹说, the study's contact author who worked on this project as a research scholar in Professor Or Hen's team at the 麻省理工学院. 她现在是特拉维夫大学的高级讲师. "Those neutrino energy reconstruction methods are still very challenging, and it is our work to improve the models we use to describe them."
These methods include modeling the interactions with a theoretical simulation called GENIE, allowing physicists to infer the energies of the incoming neutrinos. GENIE is an amalgam of many models that each help physicists reproduce certain aspects of interactions between neutrinos and nuclei. 因为我们对中微子知之甚少, it's difficult to directly test GENIE to ensure it will produce both accurate and high-precision results from the new data that will be provided by future neutrino experiments.
To test GENIE, the team turned to a particle nuclear physicists know a lot more about: the electron.
“这利用了电子和中微子之间的相似性. We are using electron studies to validate neutrino-nucleus interaction models,“Khachatryan said.
中微子和电子有许多共同之处. They both belong to the subatomic particle family called leptons, so they are both elementary particles that aren't affected by the strong force.
在这项研究中, 该团队使用了电子散射版本的GENIE, 被称为e-GENIE, to test the same incoming energy reconstruction algorithms that neutrino researchers will use. 他们没有使用中微子，而是使用了最近的电子结果.
The input data for the study came from experiments conducted with CLAS探测器 at 杰佛逊实验室's Continuous Electron Beam Accelerator Facility (CEBAF), 一个能源部的用户设施. CEBAF is the world's most advanced electron accelerator for probing the nature of matter. The team used data that mirrored the simplest case to be studied in neutrino experiments: interactions that produced an electron and a proton (vs. 一个介子和一个质子)来自氦、碳和铁的原子核. These nuclei are similar to materials used in neutrino experiment detectors.
进一步, the group worked to ensure that the electron version of GENIE was as parallel as possible to the neutrino version.
"We used the exact same simulation as used by neutrino experiments, 我们用了同样的修正,Afroditi Papadopoulou解释道, co-lead author on the study and a graduate student at MIT who is also in Hen's research group. “如果这个模型不适用于电子, 我们讨论的是最简化的情况, 它对中微子永远不起作用."
即使在这个最简单的例子中, 准确的建模至关重要, because raw data from electron-nucleus interactions typically reconstruct to the correct incoming electron beam energy less than half the time. 一个好的模型可以解释这种影响并修正数据.
However, when GENIE was used to model these data events, it performed even worse.
"The result is actually to point out that there are aspects of these energy reconstruction methods and models that need to be improved,“Khachatryan. said "It also shows a pathway to achieve this for future experiments."
The next step for this research is to test specific target nuclei of interest to neutrino researchers and at a broader spectrum of incoming electron energies. Having these specific results for direct comparison will assist neutrino researchers in fine-tuning their models.
根据研究小组的说法, 其目的是在数据和模型之间达成广泛的一致, which will help ensure future neutrino experiments can achieve their expected high-precision results.
要了解更多关于实验的信息，请访问 杰佛逊实验室.