Quantum Diaries

As has been communicated quite well by many of my colleagues here on Quantum Diaries we are officially in a VERY exciting time in particle physics. The Large Hadron Collider has had its first collisions marking a very significant milestone in what has been a long and hard journey of a new accelerator and the many experiments that will be receiving data for many years to come.

While I am not currently at CERN and I continue to spend most of my days slugging it out with the data here at Fermilab, I can’t help but be caught up in the amazing images of the first collisions and while I am sure many people have already seen these I wanted to make sure I had them up on my blog as well.

Display of first collisons at CMS

These images and data that are first coming off of the CMS detector are really captivating and profound. They are but a snapshot of the work of thousands tirelessly giving to the cause of building what is sure to become a triumph of modern science and engineering. All with the hopes that these experiments will allow us to unlock the deep mysteries of the universe.

However, it is with some ironic nostalgia that I received the news of the first collisions at the LHC and saw pictures of the scientists toasting in the control room and producing these high quality images of the first events. I say ironic nostalgia because I was given cause to pause and ponder…”what was the first collisions like at the Tevatron and CDF?” So after some chatting with the people here at Fermilab and my adviser I unearthed some old images of what it was like here.

CDF Logbook (that is right they used to acutally write in a book) the night of first collisions...how large do you suppose CMS's book would be?

Please remember that 24 years, 1 month, and 10 days ago when CDF saw their first collisions I was 4.5 years old. I barely knew the difference between a dog and a cat…little alone a proton and a anti-proton. But when I was looking through these images what I found was many of the same people that I’ve gotten to know and love here at Fermilab and in the particle physics community at large were not only here for the first collisions, but are also involved at CERN as well. So in the span of my lifetime while I’ve been figuring out what animal goes “woof” and what animal goes “meow” These people have seen two energy frontiers and have been at the forefront of both! I am humbled and excited to see what will happen during the next 24 years and where I’ll show up in the old photo logs! Many of these images can be found here and you can keep up with the latest and greatest stuff from CMS and the LHC here

Steve and Dee Hahn at CDF first collisions...and still here keeping the ship afloat

First Collision at CDF...not quite as beautiful graphics rendering as they have nowadays

So, after 20 years of hard work, the LHC is finally a Large Hadron Collider, officially. The experiments will all get a fair few more of these lovely events before the year is out, to give us a first look at our detectors’ potential. So what comes next, after this momentous threshold has been passed? Of course, the incredible machine is capable of much more powerful things. 900 GeV collisions are relatively puny compared with where it is headed.

Now, there’s the testing challenge of repeating what was done last year – the careful raising of acceleration, the “ramping up” of the supercool magnets, to keep much much faster protons contained in the beam and under control. A lot of work is still to be done before we all go home for Christmas. If things go well, we may have collisions at over a TeV.

The next big step for the LHC will be to collide protons at energies never before seen. This will really make history, and those of us lucky enough to work on the experiments, the simulation, or on the theoretical side, will have the opportunity to analyse and interpret the absolutely brand new. Unseen by the human eye.You can’t get more exciting than that!

As the months go by, the LHC will edge closer and closer to its full potential. The ultimate goal, of course, is 14 TeV collisions. With energy this high, the accelerator will be pushed to its limits to show us an area of the world that challenges our current understanding. Science as we know it will be rewritten with those collisions.

And as if that wasn’t enough, the LHC’s progress will eventually continue, to make the same gradual push into the unknown with collisions of Lead ions. The behavior of matter at trillions of degrees, as far as we can tell so far, is not only incredibly difficult to produce, but highly unusual to say the least. Because our universe began as a small blob of the molten, broken-down soup we call “quark-gluon plasma”, we feel it is our duty as scientists to properly unravel the mysteries of this exciting phase transition. The LHC will take us, for an unfathomably short length of time, much hotter and much closer to the conditions of the early “soupy” universe than ever before. With the ALICE detector’s powerful particle identification, we should be able to make impressive sense of such a brief glimpse at the earliest point in our universe’s history.

The LHC has made history already, but over the coming years, it will help scientists learn so much about our world, and the baffling puzzles in it. The brilliantly powerful “Standard Model” of fundamental particles and forces, as it currently stands, may have some of the few missing puzzle pieces fitted, or perhaps illuminate some ill-placed ones…in any case, we will have a better clue to the whole picture – no matter what it finds, the LHC will change our understanding of the universe forever.

OK, so my last update was a little vague because we weren’t allowed to make an announcement before CERN. However, I am now allowed to say that yes, LHC collided protons this evening !

ALICE caught some of these events, some time around 5pm, and they were reconstructed and put up on the big screen in the control room – after the rising noise of discussions from the sardine-like density of people, as soon as the first collision was seen, a silence fell. Followed by a united awe-struck gasp, followed by lots and lots of cheering. Then the Champagne was popped and the tense atmosphere turned to one of celebration. Every single face was smiling intensely. Even me, as I managed, after a night shift and 25 hours of being awake, to stick around long enough to watch it.

This is a fantastic day for everyone – a historical moment we are all glad we caught. There will be a gathering of photos and as soon as they are on the web I will post the link.

Now, however, after my brief sleep, it is time to return to the control room for a third shift. I can’t wait!

UPDATE, 0:20am:

ALICE has already put some videos on youtube – the visualisation of the first event:

http://www.youtube.com/watch?v=UlhV7LFjloQ

and a video just after it, showing the atmosphere of the control room:

http://www.youtube.com/watch?v=ZOJvgatf2VY

I’m the girl with the red cardigan near the back!

Now on with the usual shift leader business Things are a little quieter here tonight, and luckily the coffee machine is working again so I think I’ll survive!

参加科学会议，最大的收获往往不在会场上，而在会场外。如果只听在会场上报告的内容，现在网上往往能找到演讲者相似的报告，提问题呢，局限于时间与环境，也很难得到多少东西。场外讨论就深入、自由得多。因此，办好一个科学会议，创造一个好的场外条件很重要（比如吃吃喝喝^_^）。如果大家都是来走过场，报告完就走人，那起不到什么交流作用。

在去会场的路上，跟吕军光老师了解了点碘化铯的知识。我担心不容易找到低本底的PMT来做低本底探测器，日本滨松卖给日本的一个实验的PMT可以做到1mBq，肯定是挑过的，大概就不会这么卖给我们了。BESIII的碘化铯用光电二极管读出，但是阈值大约对应400个光电子。用雪崩管能做到10个光电子，我们探测弱光，需要单光电子，看来还得用PMT。为了跟PMT配合，吕建议我们用碘化铯（钠），不要用碘化铯（铊）。兰州近物所也可以生产碘化铯晶体，从德国进口原料，但不知道能不能生产碘化铯（钠），能不能搞到低本底的原料。正好后来开会时近物所的李占奎报告，我问了这两个问题。感觉近物所快变成我们的探测器上游而不是平行了。后来聊了点地下实验。以前我们所在门头沟做过钙48的无中微子双beta衰变实验，从长春光机所借的氟化钙晶体，从防化所借的铅砖。这倒不错，省了很多经费，一个基金委面上项目就做成了个实验。当然精度跟现在国际上动辄上百M$的没法比。我们做透紫外容器时用过氟化钙，不过我没想到它的光产额也这么高，接近碘化钠的一半。钙48的天然丰度只有0.7%。离心或者激光浓缩同位素的代价都极其高昂。alpha粒子轰击？放到反应堆里去炼？大概都不靠谱。所以现在还找不到低成本的无中微子双beta衰变实验。

The first rule of *what just happened* is that you are not supposed to talk about it
The second rule of *what just happened* is that you are NOT supposed to talk about it.

More information and official “actually talking about what just happened” stuff to come.

Suffice to say, it’s a beautiful thing……and it looks like the world has not been destroyed

First collisions in the LHC are looking very very imminent. If you want constant updates keep your eye on the comments of this blog!

Tonight has seen further achievement for the LHC, and the anticlockwise beam seems to have been their main focus through the past 24 hours. Our Silicon Pixel detector triggered on a few beam-gas events from it, and there have been a few important timing measurements made for ALICE. Mostly though, we are waiting with baited breath for collisions. Which, looking at the incredible progress, could come very soon indeed…a Champagne bottle is waiting in the coffee room. We are all very excited! Watch this space…