AUSTRALIAN FRONTIERS OF SCIENCE, 2005

Walter and Eliza Hall Institute of Medical Research, Melbourne, 12-13 April

Session 8: Discussion

Question –  What are dangers of having such a collider? Are there issues with that?

Elisabetta Barberio – Yes, there are issues, but not really for the people that live around the collider. For 14 years I have been living in Geneva and my house was very close to the ring.

The risks are for the people like me and like the others that work on the machine, and in fact there is very strict access. One of the reasons why we do all the simulation and all this work in understanding how we can use the detectors for 10 years without touching them is that after a little bit of this collision they become radioactive and [inaudible] activated. So you are not allowed to go down in that cavern and access the detectors easily. For example, some of the detectors will require at least three months of cooling down before you can do any operation. And some of them will never be touched.

Our detector should be keeping a lot of things inside the activation comes from the fact that we have particles that go through matter and are starting activation of material. But as soon as you go out of the cavern it is different. I’ve been living on the ring for 14 years and I’m still alive.

Question – I have a Dorothy Dixer. Elisabetta quite rightly concentrated on the challenges of the future, but there have been some very important questions that have been already answered, and you in particular I know have made contribution to the big question of what happened to all the anti-matter that occurred straight after the Big Bang.

Elisabetta Barberio – Yes. This is the other experiment we are doing in Japan; I didn’t have time to mention it. At the beginning of the Big Bang, an equal amount of matter and anti-matter was created, and at a certain point in time, very early on, somehow the anti-matter disappeared. And so we have a universe that is matter.

We have started understanding a little bit about this. We understand at least why 5 per cent of this anti-matter disappeared; it is due to the fact that one thing we thought was conserved together in particles, like the charge parity, is violated. So when we have an equal amount of matter and anti-matter, some of the anti-matter will not stay anti-matter, but these heavy particles have a short lifetime and somehow they transform themselves into matter. So we are starting to understand.

The full answer we still do not have, but part of it we are starting to shed light on.

Question –  Lyle, given that your energy hasn’t been probed by accelerators before, do you have uncertainties in the particle physics that impact on your simulations?

Lyle Winton – One of the uncertainties is that we really don’t know that much about the Higgs, I suppose, and so I think what needs to happen is that a lot of simulation needs to be done in various different ranges in order to try and predict what we will see if there is one, one way or the other. So that adds to the computing power, I suppose.

Elisabetta Barberio – What we really will know is how particles interact with matter, these kinds of things that will also have medical applications. We don’t know, when we look at this event in all those other messy things, how much really of these messy things we have. This is where the real uncertainty comes from. And the first month or year of the data taking will be to understand our background.