News about India-based Neutrino Observatory
Several days ago I occasionally glanced at a rolling news on CCTV News Channel “…… will build the largest neutrino observatory”. I was shocked by my ignorance. Then I stood there for almost 10 minutes to wait it showing up again. Actually it is “India plans to build the largest fundamental scientific project —— neutrino observatory”. Many Chinese media reported this news. Generally it reads: “Indian scientist Mondal told media on Oct. 10 that India plans to start the construction of the Neutrino Observatory in 2012. The location is in Tamil Nadu in south India. He said, Indian scientists hope to collaborate with western countries, make neutrino beam with the accelerator in US or Europe and aim at the planned neutrino observatory in India.”
There was a workshop on neutrino factory on Oct. 12 in India. Prof. Mondal said above to media right before this workshop. The India-based Neutrino Observatory (INO) was proposed around 2000. The laboratory will be built 1300 meters underground. It uses 50 kton iron as target, interlaced with glass resistance plate chamber (RPC) as active detectors. It can be used to study atmospheric neutrinos as Super-K does, and can also serve as the far detector of a long baseline accelerator neutrino experiment.
There are many proposals and R&D on the next generation long baseline neutrino beam, such as beta beam and muon accelerator. It is generally believed that we need wait reactor neutrino experiment, such as Daya Bay, to give a clue on the mixing angle theta13, before determining which way we should go.
前几天偶然从CCTV新闻频道看到一行滚动新闻“… … 将建造最大的中微子观测站”。我被自己的孤陋寡闻吓了一跳，硬是站在电视前等了十分钟，等它再次滚出来，原来是“印度计划建造全国最大的基础科学工程——中微子观测站”。网上各大媒体也纷纷转载，原文大致是：
印度科学家蒙达尔教授１０日对媒体说，印度计划于２０１２年开始建造中微子观测站，地址初步定在南部泰米尔纳德邦。他说，印度科学家希望与西方国家展开合作，使美国或欧洲有关国家的粒子加速器产生的中微子束穿透地球、抵达印度计划建造的中微子观测站，以便观测。
印度大约在2000年的时候提出了这个实验计划（INO），在地下1300米建立一个地下实验室，采用5万吨铁做介质，用玻璃阻性板探测器（RPC）与铁板一层一层交错叠起来，并加磁场，用以探测中微子反应产生的带电粒子。其探测器类似于美国正在进行的MINOS实验。MINOS实验的探测器是塑料闪烁体，将塑料闪烁体换成RPC，造价可便宜不少，同样的经费可以做得比较大，但是RPC需要通气体，维护比塑料闪烁体难，噪声也比较大。这样的观测站可以研究大气中微子，也可以做为加速器中微子实验的远端探测器。如果用来测量大气中微子，MINOS已经比较大地提高了日本超级神岗实验的精度，Nova和T2K也可以做，INO的精度跟它们差不多。如果做加速器中微子实验，则需要有人愿意把束流对准它，探测器的朝向也不同。出现这个报道的起因是10月12日要在印度开一个关于中微子工厂的国际研讨会。印度希望在CERN建中微子工厂，然后把束流送过来。
2005年我在意大利开会时碰到这个蒙达尔，盛情地邀请中国参加INO。我说我们首先要做大亚湾实验，大亚湾实验做好以前不会谈任何其它中微子计划。实际上，等MINOS，Nova，T2K做完，INO探测大气中微子已经没有太大的意义，探测长基线中微子则是没谱的事。beta beam和muon加速器（中微子工厂）不仅造价昂贵，远远高于INO的造价，关键技术也还没有解决，值不值得修建还要看theta13的大小，要等大亚湾实验的物理结果出来以后才知道。
趁此机会到维基百科上查了一下INO的介绍，很有意思的是大部分篇幅都在讲环保问题。INO选的点在动物保护区内，环评仍在争论中。
