Jinlong ZhangBy Louise Lerner • February 5, 2012
Argonne physicist Jinlong Zhang received an Early Career Research Award to design and build instruments to measure particle collisions at the Large Hadron Collider (LHC) in Switzerland.
Do you remember when you first got interested in science as a kid?
Oh, well, that can go back to when I was about nine years old or ten years old. I was born in China, I’m Chinese, so my parents are very traditional Chinese; they’re busy, but they’re trying to teach me everything. Around that time you might know T.D. Lee and C.N. Yang, famous particle physicists in China. In our field they are very famous, so they got the Nobel Prize in Physics in 1974, I think. That was an icon for me for many, many years. That’s basically when I learned that when I went to college, my first choice would be physics. I did not, you know, go to others on principle [laughs]. And it was theoretical physics.
But the school I went to actually was not as strong in particle physics. They only have a couple of professors there that left the school when I was in my second year. So after that, I decided well, I’ll go to see a little bit more, and I’ll go to Beijing. There’s a particle physics institution called the Institute of High Energy Physics in Beijing.
How did you decide to come to the United States?
Well, that was actually an obvious choice because, you know, when I finished getting my Master's degree, there was really no other place to do particle physics [laughs]. Yeah, you basically have to come to the U.S. And that time wasn't a good time because the Superconducting Super Collider got cancelled. You probably know the SSC Project. It was the big collider physics project planned in Texas. But we did have a small project at SLAC at Stanford that started. And I knew one professor at Colorado State—he has a connection at Beijing, and I knew him there. We collaborated a little bit on a project, so I just followed him to the US.
What did you do after coming here?
Well, when I was at SLAC, that's in Silicon Valley; at that time, computing software was very popular. And with particle physics, you always need to learn a lot of computing technique before you can really do anything. Our software is very complicated. Probably more than 50% of my time I do computing, actually, and less than 50% I do physics.
So I’d say that once I got my PhD, in case I couldn’t survive in the field, I can go to Silicon Valley. That was one of my Plan Bs [laughs]. And you know, lucky, right after that, I was getting my PhD degree and the whole IT boom went down to the bottom [laughs].
What do you like about your work?
Well, in this field, there’s always lots of interesting things; computing software, the different technology, and of course, physics itself is really a frontier in principle. And you know, many advances happen in this field first; then later they become applications in medical physics or biology.
Really? What's an example?
Like some methods for treating cancer, using a small accelerator. You can find lots of that stuff in the modern hospital, and those technologies come from our field. And you may know that anytime you search on the Web, you use "www", right? That came from our field. Web searching technology started at CERN. It’s always www dot something; and this technology protocol started in our field.
So yeah, it’s a really interesting field. Of course, you learn a lot, and you work hard, because generally, the Ph.D. takes at least five years. It’s long, but you learn a lot.
Can you tell me a little bit about the work that you got the award for?
Ah, okay. So what we are doing at CERN—the real experiment at Geneva—is colliding the protons, high-energy protons. When the protons collide they create a tiny volume with very high energy. So basically, we’re trying to reproduce the Big Bang conditions of our universe. When they cool down, then you can find lots of interesting stuff. Like black holes—that caused a little bit of a story a year or two ago.
We are trying to find why every particle has mass. Where does the mass really come from? It’s one of our fundamental questions. Basically, we need to find the God particle. (Actually it's called the Higgs particle, but people like to call it the God particle because that particle gives every other particle mass.)
This is really interesting physics. But finding this stuff is really rare. Recording all of the collisions is a problem. Say we record all of the data that the LHC produces: you'd be producing hundreds of thousands of CDs per second.
But you really need two years of good data taking to find probably a few hundred special events. So it’s really rare. How do we find the rare stuff in that huge amount of stuff we call background? That means you want to throw away the junk as soon as possible, and keep the good stuff.
The strategy we are doing is taking the 100,000 CDs of data per second but we only record roughly twenty CDs' worth per minute.
That is a big reduction.
Right. But you do not want to throw away the good stuff, right? That means you want to really see what you are producing.
So what I’m working on is basically developing hardware, a piece of equipment to give you the ability to examine this stuff at the very fast rate. Say your machine produces an event. You want to see what that event looks like because it’s really complicated. So you want to find the information and then, decide to keep it or not. This is the whole project I’m working on. It’s a piece of special hardware, like a memory. The technology behind it is a piece of memory. If you put in an address, you return a piece of data, right? That’s how the modern memory works. With this special technology your input is not an address. It’s another piece of data. The input data and the different piece of data do a pattern match. And so you give some information and the computer says “Okay, that’s an interesting pattern. I'll keep that”—because you do a fast pattern matching. That’s the technology behind this piece of equipment.
It will be a big difference. With hardware you'd get at least three orders of magnitude difference.
What is the big challenge in your field?
Well, we do not know what we will find. Of course that’s always a good thing or a bad thing, right? You do not know what you will find, but you just do your best to make sure you do not produce anything biased. That’s very important because we are looking for something really rare in a huge background.
So you really need to make sure you produce a solid physics result that’s accurate. That's really a challenge. You can make sure every step you did your best and make sure you do not throw away good things; then later on you do the software fitting, do the analysis and make sure they’re real. You do not want to apply any selection criteria with bias. So at every step we have to get three thousand people in the collaboration working together, while making sure that we got solid results.
We may see a surprise in a couple of months or a couple of years. This is a completely new energy area, so we do not know exactly what we will find. We have a rough idea; good theory gives us some predictions, but they may be right, and they may be wrong.
Did you have any role models when you were going through school?
Well, Fermi was one of the best physicists, I always thought. That’s because he wasn't just good at theory; he was one of the unique particle physicists—he was both good at theory and also good at experiments. And he—how do I say this?—he could use a simple method to demonstrate a complicated problem. That’s always amazing to me.
I think Fermi is the best physicist model for myself because I’m an experimentalist. Of course, I’m biased [laughs]. Everybody thinks Einstein's the best physicist, of course, but for me, it's that you not only predict something, but you can do experiments to find that by yourself. That’s important for me.