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Cao Jun | Institute of High Energy Physics | P.R. China

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My Daughter

Sunday, May 24th, 2009

keke

My daughter is 1.12 years old.

She likes books and reads aloud. But it is not easy to understand. Each sentence has 3-5 words. Probably she is speaking Korean.

She knows to say thanks. But it seems she doesn’t know who should say, the person receives something or the person gives. She often makes me awkward by giving me something and saying thanks.

Sleeping is an action, not a process. When I said “Keke, sleep”, she was docile enough to grovel on her pillow. After 3 seconds, she got up and continued to play. Yeah, sleeping is done.

Once she understand something is bad, not allowed to do, she will do it repeatedly, and smile evilly.

我女儿现在1.12岁了。

很喜欢翻着书大声朗读,不过听不太懂,三五个字一句,可能是韩语。

她知道说“谢谢”,但好像不清楚是拿东西的人应该说还是给东西的人说,经常递给我一件东西,然说说“谢谢”,弄得我很尴尬。

一旦她明白一件事是坏事,不许干的,她就会反复干,带着一脸贼笑。比如掰茶几的护角,在地板上撒水。

尿尿知道蹲下,叫人,或指尿盆。但帮助不大,因为经常谎报军情,有事没事蹲下嘴里“嘘嘘”。以后一定要多给她讲“狼来了”的故事。

睡觉是一个动作,不是一个过程。“柯柯,趴下睡觉”,她就很听话地趴到她的枕头上睡觉,三秒钟后爬起来接着玩,因为睡觉的指令已经执行完了。

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Public Science Day at IHEP

Sunday, May 24th, 2009

高能所公众科学日

上周末是中科院的公众科学日,高能所除了开放实验室供参观外,还安排了对撞机漫谈,探月工程, 高能物理中的超级计算机、中微子振荡与宇宙的物质-反物质不对称等四个讲座。两年前我曾在公众科学日做过一次关于中微子的讲座。虽然水平有待提高,对科普工作我一向是很热心的,宣传科学也是每个科学家的社会责任之一。现代科学离老百姓的生活太远,因此各种伪科学、反科学大行其道。俗话说,牛屎铺[1]这块阵地,无产阶级不去占领,资产阶级就一定会去占领。此次代表无产阶级前去占领阵地的是邢志忠。之前我还纳闷这个报告是谁去做的,问了大亚湾实验的几个人,都说不是。海报上没有说报告人,报告完了网上也找不到演示文件,说明这个宣传还不够到位,刚占领阵地又撤了下来。

[1]牛屎铺是网络史前用语,newsgroup的中文翻译,现在用google搜都不大容易找得到了。

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Dark Matter Signal Disappeared

Friday, May 15th, 2009

I mentioned ATIC experiment in my blog last month. Many people has been excited by the possible dark matter evidence implicated by it for a while. Coming in May, HESS and Fermi/GLAST confuted it with higher precision data.

Have a rough count, there are quite a lot similar things in my no so long scientific career, such as lepto-quark, pendaquark, Heidelberg-Moscow neutrinoless double beta decay results, and many more. Most of them are based on serious analyses, just extend a little bit further with bold creativity. Some other analyses just like a joke.

Some experiments were suspectful at the beginning, e.g. Ray Davis’ solar neutrino experiment. The poor guy repeated his experiment for 30 years. Finally he became the oldest one when wining Nobel Prize. Some experiments lie between, e.g. the discovery of neutrino by Reines and Cowan. People believe they did observe neutrino. The measured cross section agreed with theoretical prediction very well, in 5%. In the next year, Lee and Yang revealed the parity nonconservation. Thus the theoretical prediction of the neutrino cross section was wrong. The actual value is twice larger. So they analyzed the data again, and the measured cross section was doubled, agreed with the new prediction very well again. Such an important discovery was not awarded Nobel Prize until 40 years later. The poorer Cowan couldn’t wait so long. For this reason, Zhizhong Xing often reminds us, “you should try to live long if you have done an important work.”

Science always advances in such debating of true or false. Kandice Carter wrote a review on the pendaquark, said “Even though the pentaquark seems to be illusory, at least in the form physicists have pursued so far, the alley leading toward it has been full of interesting revelations.”

暗物质信号又没了

上个月我在博客里提到了ATIC实验。不少人很是为它看到的可能是暗物质信号的结构激动了一阵。转眼进入五月,HESS和Fermi/GLAST两个实验就用更精确的数据否定了ATIC结果。
稍微数一数,在我短短的十几年研究生涯里,类似的事情已经不少:lepto-quark, 五夸克态, Heidelberg-Moscow的无中微子双贝塔衰变,还有不少。大部分还是基于严肃的数据分析,只是在解释上大胆地发挥了一下现象力。有些数据分析则像是开玩笑。

有的实验刚开始没人相信是对的,例如Ray Davis的太阳中微子实验,可怜的家伙就一直做了三十年,终于熬成了获奖时年龄最大的诺贝尔奖获得者。也有的实验介于两者之间,例如Reines和Cowan发现中微子的实验。大家相信他们发现了中微子,测得的反应截面也与理论符合得很好,只差5%。第二年,李杨发现宇称不守恒,这样原来的理论值不对,截面大了整整一倍。于是他们又重新分析了数据,测得的反应截面也大了一倍,又符合得很好。这么重要的发现,居然等了四十年才想起来发个奖。比Davis更可怜的Cowan终于没能熬过岁月,等到发奖的那一天。因此,邢志忠经常好心地提醒大家,假如你做出了重要的工作,一定要活得长。

科学总是在这些真真假假的争论中发展。Kandice Carter写过一篇五夸克态的回顾,说“尽管五夸克态看上去是个错觉,科学家行进的小巷里总是充满有趣的发现”。

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God could not be everywhere

Sunday, May 3rd, 2009

Today I saw the personalized signature of my sister on QQ (the most popular instant messenger in China), saying “God could not be everywhere and therefore he made mothers.” Obviously she cites this Jewish Proverb for the coming Mother’s day. So I said, if God stays absolutely at rest, his location is totally uncertain according to the Quantum Theory. Therefore he could be everywhere. This is Uncertainty Principle introduced by Heisenberg, whose epitaph reads “He lies here, somewhere”.

“But God could not appear everywhere at the same time, could he?”

“Eh~, that’s true. If you see God somewhere, to keep unitarity, he can not be elsewhere. But before you see God, he could be everywhere”

上帝不能到处都在

今天看到我妹妹在QQ个性签名上用英语写着“上帝不能到处都在,所以他创造了母亲”。显然是为了迎接母亲节引用的一句犹太格言。我跟她开玩笑说,如果上帝保持绝对静止的,根据量子力学,他的位置完全不可确定,在任何地方都有出现的几率。提出这个“测不准原理”的人叫海森堡,他的墓碑上写着“他长眠于此处,某个(不确定的)地方”。

“那上帝不能同时出现在所有的地方吧?”

“那倒是!如果你看见了上帝,那么根据幺正性,他不会同时出现在别的地方。不过在你看到上帝之前,他还是到处都在。”

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Ultra-high energy particles floating like dust

Saturday, April 18th, 2009

I have thought that ultra-high energy cosmic particles always move straight forward. At most, they deflect a little bit under the giant gravity. However, a more accurate picture is that those particles, moving at almost light speed, float in the vast and violent universe like dust in sunlight, and diffuse all around without specified direction.

Recently I invited Prof. Hongbo Hu to give a seminar to the Daya Bay students, on the excess of cosmic ray electrons at 300-800 GeV observed by ATIC above the South Pole. Those excess could possibly be explained as an evidence of dark matter annihilation. Hongbo provides another possible explanation with the pair production in the remnant of supernova. My question is, supernova explosion in short distance happen 3 times every century in average. Each explosion lasts several days. So the excess should be short-lived. The answer is, 1) the supernova explosion lasts only several days but the remnant can exist for hundreds years. The mechanism for the pair production is still valid. 2) the high energy electrons will not fly to the Earth directly. They can be easily trapped by the strong magnetic field in the galaxy, circling there for million years. The propagation to the Earth is more like diffusion.

Some physicists could read the implications behind the complex mathematical expressions. Seems I am not good at it. I prefer to have a simple and straightforward physical picture at first. The excess of the electrons haven’t enough evidences to draw an exclusive conclusion now. It is not important to say it is due to dark matter or pair production. What’s important to me is that I have a more accurate picture on the propagation of cosmic ray particles in the universe.

像灰尘一样飞舞的超高能粒子

我总以为超高能的宇宙线粒子总是直线前进的,最多,在巨大星体的引力下稍微偏转一下。然而更加正确的图像是,这些几乎以光速前进的粒子,在浩渺狂暴的宇宙中,如阳光下的灰尘般飘飘荡荡,没有明确方向地四处扩散。

不久前请胡红波教授为大亚湾的学生做了一个关于南极高能电子(300-800GeV)超出现象的讲座。这些电子超出可能被解释为暗物质湮灭产生的信号,因此激发了新的暗物质研究的热情。红波提出了另一种可能的解释,即超新星遗迹中的对产生。我的问题是,近距离的超新星爆发平均一百年才三个,每次持续不过几天,那我们看到的高能电子超出应该是短暂的,稍纵即逝的现象。得到的回答是,1)超新星爆发只持续几天,但超新星遗迹可以存在数百年,仍能提供对产生需要的环境;2)产生出的超高能电子并不是直线飞到地球上,很容易被星系中的强磁场俘获,盘旋亿万年,因此电子飞到地球上更像是一种扩散过程。

有些人能够从数学表达式中得到隐藏的物理,我似乎不擅长这一点,而更喜欢首先建立一个简单直观的物理图像。南极电子超出现象还没有足够的证据做出排他性的解释,到底是暗物质还是对产生,对我来说并不重要,重要的是我对宇宙间粒子的飞行有了一个更正确的图像。

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With Telescope, human become cleverer.

Thursday, April 16th, 2009

Several days ago, I served as a committee member of the interviews of new graduate students. Although most students are motivated to study high energy physics, quite a lot are not familiar with what they will engaged in. Too many students expressed their wishes to do physical analysis, as if the analysis is more physical. Very few wish to work on hardware. Actually, physics is essentially an experimental science. Technology of detector is the foundation of physics research. It could be more important than the data analysis itself.

Telescope is a good example. 2009 is Internal Year of Astronomy by UNESCO, to memorize Galileo’s first observation of the sky with telescope 400 years ago. In 1608, a glasses producer in Holland invented telescope. The next year, Galileo made a telescope himself and used it to investigate stars. In the following 400 years, telescope changed entirely our view on the universe. To name a few, we observed the tiny advance of Mercury perihelion, which is the first evidence of Einstein’s General Relativity. We know the Universe was born 15 billion years ago with a “Big Bang”, keeping inflating, and full of black holes. We know the normal stars are only several percent of the total mass of the universe. Others are mysterious dark energy and dark matter. As we build larger and larger neutrino detectors deep underground, in the sea, or in the ice, they can serve as neutrino telescope to observe the universe, totally different from the telescope detecting electromagnetic waves including light.

In Chinese, 聪明means clever, wise, or bright. It is consisted of two characters. The first one, 聪, means good hearing. And the second, 明, means good sight. The left part of 聪 is an ear. The top right part is two eyes. The middle right is a mouth. And the bottom right is heart, which ancient Chinese believe to be in charge of thinking. Physical thoughts won’t be created without reason. It is inspired by the information we get from the ear, eye, and mouth, and finally analyzed by the heart. Telescope greatly enlarged our view, thus human become cleverer. In high energy physics, detectors are our eyes.

有了望远镜,人变聪明了

前几天参加了高能所的研究生面试。尽管有志于从事高能物理研究工作,但相当多的学生对将来要从事的工作性质并不是特别了解。过于多的学生希望做物理分析工作,似乎这样更像物理研究,很少提出做硬件。实际上,物理本质上是一门实验科学,探测技术的发展是物理研究的基础,往往比数据分析具有更重要的意义。

望远镜是一个很好的例子。2009年是联合国定的国际天文年,以纪念伽利略首次用望远镜观测天体400年。1608年,一个荷兰眼镜商发明了第一架小望远镜。次年,伽利略用自制的望远镜第一次观测星球。400年来,望远镜技术的发展彻底改写了人们的宇宙观。例如,我们知道了微小的火星进动,必须由广义相对论来解释;我们知道了宇宙诞生在150亿年前,在不断膨胀,知道了宇宙中遍布着黑洞,知道了常规的星体只占宇宙质量的百分之几,其余则是神秘暗能量和暗物质。随着中微子探测技术的发展,人们在地下、海底、南极冰层中建立了巨大的中微子望远镜。

在汉语中,“聪明”一词大约来源于“耳聪目明”。耳朵尖,眼睛亮,就是聪明。特别是“聪”字,左边一个耳,上面两只眼,中间是口,然后由心做分析。物理思想不会凭空产生,往往由耳朵听到的,眼睛看到的,嘴巴交谈的,然后在心里激发出新的想法。望远镜拓展了人的视野,人也因此变成更加“聪明”。对高能物理来说,探测器就是我们的眼睛。

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Italy visit in March

Tuesday, March 31st, 2009

Quantum Diaries starts again. At its first start in 2005, my friend Zhizhong Xing, a neutrino theorist, contributed a lot of interesting articles. After the Quantum Diaries paused, Zhizhong moves to a Chinese scientists’ blog site, http://www.sciencenet.cn/u/xingzz, keep spreading all kinds of fancy news.

It is said that this restart is more or less motivated by the upcoming release of the movie “Angels and Demons”. I am very impressed by this novel. “Angles and Demons” is written by Dan Brown. A physicist at CERN created anti-matter, which could be used as a MDW (Mass Destruction Weapon), which we failed to search out in Iraq. The anti-matter was stolen and hidden in Vatican to threaten the on-going Pope election. When I heard the news that Quantum Diaries will be restarted, I am preparing for a workshop in Venice, Italy, Neutrino Telescope 2009. Last time I visited Italy was in 2005, soon after I read this novel. I went to Frascatti in suburb of Roma for the Neutrino Factory Workshop. I have been in Roma once in 2000, as a tourist. But I haven’t any impression on the metaphor of the buildings described in Dan’s novel. After the meeting, I came to Roma in the early morning by train. My flight was in the evening. I had one day to investigate these great buildings. The left-baggage office at the train station was crowded incredibly with a 2-hour long queue. Thus I had a very special experience, with a backpack and a luggage, walking along the route in Dan’s novel, up to the Castle Santa Angelo.

Back to the Venice meeting. Venice in March is very beautiful. Italian food and wine are excellent. Of course, the talks and discussions are identically interesting. For example, Prof. Minakata from Tokyo Metropolitan University gave a talk titled “Neutrino non-standard Interactions: Another eel under a willow?”. Actually he means “another loach under a willow”, a Japanese proverb. Loaches like to live under willow trees. This proverb means that just because you caught a loach under the willow tree once, it doesn’t necessarily mean that there will always be a loach there. He asked the audience if they know loach. I am surprised that nobody responded yes. Probably that’s why Minakata San changed the loach to eel. I am no longer a theorist for long time, thus have difficulties to catch point from a bunch of formula in this talk. But I know loach very well. It is common in rice-planting area. Well, there is a famous Chinese dish, called loach in Tofu.

量子日记又重新跟大家见面了。2005年量子日记启动的时候,我的朋友、中微子理论家邢志忠教授曾为大家贡献了不少有趣的文章。量子日记暂停后,志忠又转战科学网博客,坚持不懈,孜孜不倦地提供各种小道消息。

据说这次重新启动与《天使与魔鬼》电影5月15日公映活动有关。《天使与魔鬼》是丹•布朗写的小说,《达•芬奇密码》的姊妹篇。小说的背景是欧洲核子研究中心的科学家维特勒研制出了蕴含着极其强大能量的反物质,结果被人杀害,反物质被人窃取,藏到了梵帝冈,用以要挟即将进行的教皇选举。接到量子日记重新启动的消息的时候,我正在准备去意大利参加“中微子望远镜2009”研讨会。上一次去意大利是2005年,我刚看完《天使与魔鬼》不久,到罗马郊区的Frascatti参加“中微子工厂”研讨会。2000年时候,我曾经到罗马走马观花地旅游过一次,但对书中建筑的种种隐喻完全没有印象。开完会后,第二天清晨坐火车来到罗马。飞机要很晚才起飞,我有将近一天的时间重新看一看。罗马火车站行李寄存处生意兴隆,排了至少两小时的长龙。于是我背着包,拖着行李箱,沿着丹•布朗的路线,一直走到天使堡。

威尼斯的三月非常漂亮,意大利饭和红酒非常好,当然,会议报告也同样有意思。例如,来自东京都立大学的Minakata教授做了一个报告叫“中微子非标准相互作用:柳树下的又一条鳗鱼?”。出处来自日本的一条谚语“柳树下的又一条泥鳅”。泥鳅据说喜欢呆在柳树下,你曾经在柳树下找到了一条泥鳅,但并不意味着在同一个地方还能抓到一条。他问“你们知道泥鳅吗?”,与会的大部分西方人没有反应。我想这也是他题目中把泥鳅改成鳗鱼的原因。我已长久不关心理论物理,因此无法在报告内容的一大堆符号中抓住关键。不过我很熟悉泥鳅,它在适宜种植水稻的水乡是非常常见的。还有一道名菜叫“泥鳅豆腐”。

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