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李淼的博客

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两个新闻  

2009-12-21 15:00:33|  分类: 默认分类 |  标签: |举报 |字号 订阅

  下载LOFTER 我的照片书  |

第一个新闻,其实已经有点老了,就是CDMS发现了暗物质粒子的迹象。(其实还有第三个新闻,这第三个是理论新闻,我正在看,留作以后的话题吧)

我用迹象,是说这个结果还不能算发现。在粒子物理中,发现必须有5sigma以上的证据,而此次结果,只有一个sigma左右。

CDMS的论文已经在arXiv贴出,但估计要下礼拜一或礼拜二才能看到。摘要为:

We report results from a blind analysis of the nal data taken with the Cryogenic Dark Matter
Search experiment (CDMS II) at the Soudan Underground Laboratory, Minnesota, USA. A total
raw exposure of 612 kg-days was analyzed for this work. We observed two events in the signal region;
based on our background estimate, the probability of observing two or more background events is
23%. These data set an upper limit on the Weakly Interacting Massive Particle (WIMP)-nucleon
elastic-scattering spin-independent cross-section of 7:0 × 10..44 cm 2 for a WIMP of mass 70 GeV/c2
at the 90% con dence level. Combining this result with all previous CDMS II data gives an upper
limit on the WIMP-nucleon spin-independent cross-section of 3:8 × 10..44 cm 2 for a WIMP of mass
70 GeV/c2 . We also exclude new parameter space in recently proposed inelastic dark matter models.

文章:Results from the Final Exposure of the CDMS II Experiment

科学集体博客Cosmic Variance的JoAnne有个博文,是她和Risa参加一个CDMS学术报告的现场报道。CDMS同时在SLAC和Fermilab做报告。这篇博 文中最有趣的一句话是” Rumors are spreading that at least 3 groups of theorists have papers ready to submit to the ArXiv after the seminars are concluded. The era of data has begun!”

可见理论家们实在等不及了。

博文的全文:Dark Matter Detected, or Not? Live Blogging the Seminar

第二个新闻,LHC有了第一批物理结果!

Tommaso Dorigo在他的博文中说,虽然这些结果没有新物理,但说明LHC机器和研究人员都在完美的工作状态。

Dorigo自己来自意大利的Padova,他们小组在过去的两周中寻找phi介子,所以他的博文主要谈他们的结果。Dorigo解释道,

I was especially pleased to see that the effort of the small group of physicists from Padova and Cyprus which my colleague Franco and I have managed to put together has not been vain. We have been working day and night in the last two weeks, in order to produce an approved signal of thephi meson. The phi is a electrically neutral hadron, composed of a strange-antistrange quark pair. It is a very well-known particle; it was discovered in the fifties and we know everything about it, but it is worthwhile to search its decay: it is a very good calibration line on which to test the detector performance, for a couple of reasons.

Dorigo的全文:First LHC Results!

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