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Neutrino Mass Upper Limit Estimated by Galactic Distribution
利用银河系分布估计出中微子质量上限

"Six thousand billion of them are going through your body every second." That's physicist Lawrence Krauss on neutrinos, on the June 15th weekly Science Talk podcast. "Neutrinos are the lightest elementary particles we know of. The name comes from the fact that they had to be neutral because we couldn't see them in detectors. But they had to be light. So Enrico Fermi called them "a little neutron," in Italian is neutrino. So they were baby neutrons, which were the only other neutral particles at the time that were known."
“每秒钟有6万亿个这种物质穿过你的身体。”这是物理学家劳伦斯•克劳斯在6月15 日的每周《科学讲座》播客上对中微子的描述。他说：“中微子是我们所知的基本粒子当中最轻的一个。之所以叫它中微子是源于它的中性特质，因为我们在检测器里无法观测到它们。而毫无疑问，它们必然很轻。因此，恩里科•费米把它们叫做‘小中子’，在意大利语中就是中微子的意思。综上，中微子就是极小的中子，是它被发现以来除中子外唯一的中性粒子。”

Now astrophysicists have put a best-guess upper limit on the mass of the neutrino. The research is being reported this week at the Weizmann U.K. conference at University College London and will appear in an upcoming issue of Physical Review Letters.
现在，天天物理学家对中微子的质量上限作出了一个最佳测定。研究结果将于本周在魏茨曼英国伦敦大学会议上作出报道，并发表于即将出版的《物理评论通讯》上。

The work took advantage of the huge 3-D galaxy map called Mega Z. Because there are so many neutrinos, their tiny masses add up to influence the overall distribution of galaxies. And the researchers say the galactic map depends on a neutrino's mass being no more than 0.28 electron volts, less than a billionth of the mass of an atom of hydrogen, the lightest element. "These are the most interesting particles in nature."
这项研究利用了Mega Z这个巨大的三维星图。原因在于，星系中有众多的中微子，而当这些微不足道的质量加在一起时，其总和就会影响整个星系的分布。研究人员还说，银河系的构成取决于中微子的质量，由此推断出中微子质量的最小上限：不超过0.28电子伏特，该数值还不到一个氢原子质量的十亿分之一。“这可真是一种最有意思的粒子！”

—Steve Mirsky

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