WEBVTT 00:00:01.000 --> 00:00:21.000 I'm not jotty, you may have noticed, but yeah, they are away at the moment, so it's myself and Deborah hosting today. We are very lucky to have Ben with us. Ben's an associate professor at the University of Plymouth in theoretical physics and is working on laser particle stuff and is here to talk to us today about that 00:00:21.000 --> 00:00:37.000 So yeah, over to you. Hi, everybody. Thanks to the organizers for inviting me here. Although I've been kind of associated with the Central Asia facility for a long time, the theories I've never actually been around before, because it's very exciting to me 00:00:37.000 --> 00:00:53.000 So, I'm going to talk about science goals and laser particle interaction. So this is a bit of a synergy between particle physics and physics. And I noticed, we just sit in the cafe 00:00:53.000 --> 00:01:00.000 The cafe sits between the particle physics building, which is attached to the central laser facility. 00:01:00.000 --> 00:01:03.000 This is the perfect place to begin this kind of a talk. 00:01:03.000 --> 00:01:19.000 Okay, so we begin with some sort of kind of some key concepts in strong field electrodynamics. That's going to be the fundamental theory that's going to describe what's happening in those interactions between charges and wave forces 00:01:19.000 --> 00:01:30.000 And then we spent a little bit of time talking about charge field coupling in Tensor electronic backgrounds. I think that's something kind of unique to mathematical pivoted before, so it might be interesting 00:01:30.000 --> 00:01:34.000 And then the second half, a little bit about kind of 00:01:34.000 --> 00:01:44.000 Measurements that you want to make at different experiments and science schools of these things. And then finally talk about the Hp 00:01:44.000 --> 00:01:55.000 Okay, so just going with some basics then. So we have the scattering paradigm in particle physics of having two bunches of particles in our instate, which is well-defined and understood 00:01:55.000 --> 00:02:02.000 We collide them, and we infer from measurements of the skeptical particles that physics that occur during that expansion 00:02:02.000 --> 00:02:18.000 Now, before we consider is our dying where we replace one of the themes of particles with an intense laser pulse. So we have a probe beam, the electrons or positrons are completely photons, and we have an intense laser 00:02:18.000 --> 00:02:25.000 Now we should perform the same kind of scattering experiments where we tend to measure is what happens to the protein 00:02:25.000 --> 00:02:32.000 And so from that coordinate collision has the charges propagated in the X 00:02:32.000 --> 00:02:47.000 Different to the public normally tend to measure what happens to the laser force because with this in high intensities, high intensity laser pulses are highly focused, which means that the shock-to-shock reproducibility is quite low. Instead, it's maybe the protein at the low 00:02:47.000 --> 00:02:49.000 It's slightly different, but there's some kind of similar to 00:02:49.000 --> 00:03:00.000 So, talked about intense electromagnetic fields by saying that, electromagnetic field is intense. I'm intrinsically saying that the field is coherent 00:03:00.000 --> 00:03:17.000 So interesting coherence electromagnetic fields are quite important. So some examples are slowly varying magnetic fields, so in cavity experiments, PV mass or ELFs. The fields inside are crystals with a high degree of symmetry 00:03:17.000 --> 00:03:27.000 Well, in that case, you've essentially got lots of Coulomb centers, but if you have a charge which is colliding with that, all those Coulomb centers in the rest frame, the charge appear as a coherence field. 00:03:27.000 --> 00:03:44.000 So for the QD, I'll talk about can we use describe bacter physics. Beam scattering. So beam strolling, apply particle energy is an example of a magnetic field. And what I'll talk about mainly from this laser pulses. So this could be optical laser pulses or X-ray electrical lasers 00:03:44.000 --> 00:03:59.000 Coherence implies that the average expectation value of the electric field is 0. A count, for example, would be incoherent fields like blackbody radiation and strong or radiant dust jets where there's not a well-defined phase relationship between photons with these are different 00:03:59.000 --> 00:04:04.000 So incoherent fields like this, we expect that the 00:04:04.000 --> 00:04:08.000 The expected field strength is operation is up to 0. 00:04:08.000 --> 00:04:23.000 So I mentioned strong field, what do we mean by strong fields? We can come up with a QED field strength scale by taking some of the fundamental parameters from QED. So the electron mass, the positive charge 00:04:23.000 --> 00:04:30.000 Thanks, Custom. Put them all together using dimension analysis to come up with a field strength, and you get this formula here. 00:04:30.000 --> 00:04:49.000 So this is sometimes referred to as the Schringer limits or crystal clear. These are really bad names, because first of all, it wasn't Schringer who first came up with this more than a decades before. I didn't know what we're talking about. This technique's not lit. As you can see, we can go beyond this critical theory is also a bad name. There's no crystal phase transition that happens here 00:04:49.000 --> 00:04:54.000 But people use these names, so I'm going to refer to them. But the field strength as the strength level 00:04:54.000 --> 00:05:04.000 What's the kind of physics that can occur in a field of this strength? Imagine you've got a constant homogeneous electric field of this strength. 00:05:04.000 --> 00:05:09.000 You can work out the, work done by the sealed home and electron, same as yield 00:05:09.000 --> 00:05:24.000 They charge the electron, fuel strength, and for the dimension of the electron, we take its quantum wavelength. And the work done by a few of we could make one that was this intense would be the rest energy of the electrons. We expect that when we have 00:05:24.000 --> 00:05:31.000 Order will secure the effects like creation of electron 00:05:31.000 --> 00:05:45.000 Can we see this in nature? We have this strong in astrophysics, it seems like we can. So this is just a plot from this review of strongly magnified neutron stars, and what magnetic field strength they have 00:05:45.000 --> 00:06:02.000 So you can see from the top right there, the QED field strength scale, the Schwinger limit to the magnetic fields is around 10 to 13 Gauss, and we can see lots of data points beyond 10 to 13 Gauss compared to 10 to 14 to 15, which tends to be things like an almost electrical pulsars. 00:06:02.000 --> 00:06:04.000 So in nature, we can 00:06:04.000 --> 00:06:13.000 Albeit the magnetic field's not letting 00:06:13.000 --> 00:06:24.000 Can we see in the lab? Fortunately, with high power lasers, we're not quite at the level where we can produce these label about three orders of magnitude away from machine learnings with lasers 00:06:24.000 --> 00:06:35.000 So why are we talking about QED with lasers? Well, we use a standard trick, which is we consider gliding charges like electrons or positrons with a laser. 00:06:35.000 --> 00:06:44.000 Then, in the rest frame of those charges, the field seen is lines boosted, like the L factor 00:06:44.000 --> 00:06:55.000 So the faster the electron is that you can write the laser, the larger the field strength in the rest frame. And this is just a nice cartoon from 00:06:55.000 --> 00:07:07.000 From Jackson, this is, the cool field lines on an isolated charge, and this is what happened to any Lorenzo in the horizontal direction. You have a bunching up the field lines that indicate the enhancement of the industry 00:07:07.000 --> 00:07:19.000 So how do we quantify this? I'm going to introduce a parameter chi to occur quite a lot in the talk. So spend some time defining it properly. So chi is the strong field parameter. 00:07:19.000 --> 00:07:29.000 It's just a projection of the virtual momentum on the field strength tensor normalized by the rest energy and the unique field strength scale. 00:07:29.000 --> 00:07:43.000 So what does that mean physically? Well, if we choose our fields, our background field to be a plane wave, and we're going to be interested in lasers so it makes sense to model a lasers and a plane wave 00:07:43.000 --> 00:07:50.000 Now, in this parameter is exactly the field seen in an electron rest frame in units of that strong limits 00:07:50.000 --> 00:07:52.000 So 00:07:52.000 --> 00:08:07.000 We can again say, I want those physics does I occur to? What does that correspond to? We calculate the work done by this plane over here in the respiratory electron. And what we get is that this is chi times MC squared. So obviously, when chi is order one. 00:08:07.000 --> 00:08:12.000 That reason we call it. 00:08:12.000 --> 00:08:19.000 So getting to try order one experiment would be great. I'd be kind of take the odds and later part of the experiment 00:08:19.000 --> 00:08:24.000 There are suggestions for getting into much higher values of the software parameter 00:08:24.000 --> 00:08:40.000 I'll just give an example. So this is our URL a few years ago where they did a simulation of beam scrolling for two cervical electron beams colliding with 125 Gb, and from their simulation, you can see here on the right, these regions of 00:08:40.000 --> 00:08:47.000 Red correspond to chi which as we'll see later in the talk is a significant part of it. 00:08:47.000 --> 00:08:51.000 So, next-generation linear colliders 00:08:51.000 --> 00:08:57.000 strong acute effects or whatever process you want to study 00:08:57.000 --> 00:09:06.000 Okay, so that's a little bit about what we mean by strong fields. I want to talk a little bit about the interaction between a charge and a laser 00:09:06.000 --> 00:09:11.000 I'm going to specify for a plane wave just because it's easier to explain. 00:09:11.000 --> 00:09:15.000 So, this is a little bit theory. Hopefully it's 00:09:15.000 --> 00:09:19.000 So this is the gate potential for the background. 00:09:19.000 --> 00:09:35.000 All right, so it's the only important thing is sorry. So energy electron mass is the organizational background. This is just the shape of the laser pulse. Psi is something called the intensity character. The more intensity the laser pulse is the higher the magnific 00:09:35.000 --> 00:09:40.000 So what is… sorry, what's it correspond to physically 00:09:40.000 --> 00:09:49.000 So we consider a standard QD process. I picked up the example of a photon flying with a laser to use electron positron pair 00:09:49.000 --> 00:09:58.000 I only can calculate the interaction of the pair with background with the laser 00:09:58.000 --> 00:10:07.000 For example, Bobby, one interaction with the laser represented by dashed lines, or having two interactions with the laser and interactions, etc. We find that the amplitude scales with excise the power n 00:10:07.000 --> 00:10:16.000 That's kind of interesting because normally in QD vertices scales with the standard QV document charge 00:10:16.000 --> 00:10:34.000 But here, that's being replaced with the laser intensity. So the more intense we make the laser, the stronger, in some ways, we're binding the electron protons to the laser force. So actually, it looks like maybe more intensity actually changing the nature of the 00:10:34.000 --> 00:10:42.000 There are other ways to understand this parameter. If we would look at, yeah, processes 00:10:42.000 --> 00:10:55.000 With N trucking to the laser. The probability scale is like this square, so I to n for nether photons, or in other words, psi squared to the power n 00:10:55.000 --> 00:11:01.000 So what is psi squares? Well, we can write it in terms of alpha qed 00:11:01.000 --> 00:11:12.000 Volumes are 3 volumes with the laser wavelength and the quantum wavelength, and a total number of density in the laser. So the very hand way the square of the intensity parameter 00:11:12.000 --> 00:11:17.000 Is we find the number of interacting photons 00:11:17.000 --> 00:11:24.000 So the more intelligent look later, the higher the number of photons in the laser interacting with the electron at any given time 00:11:24.000 --> 00:11:27.000 In exchange we can make signal to one 00:11:27.000 --> 00:11:42.000 perturbation series anymore. And you have to include all orders of interactions between the laser and the background. And so you would have this sum this 00:11:42.000 --> 00:11:51.000 So we refer to this as a non-performative interaction between the laser and the charge. So this is a prediction of quantum field theory, which we can principal tests and experiments. 00:11:51.000 --> 00:11:58.000 Something like the comparison with neural saturation with small geographs 00:11:58.000 --> 00:12:10.000 The analogy is because they require the number of charge is getting photons, but essentially number of targets that the electron has when it interacts with laser force gets large 00:12:10.000 --> 00:12:18.000 Yes, I mean, it's important calculations. We have to resolve this. And 00:12:18.000 --> 00:12:31.000 So my background is as a theorist, I think most of your background is maybe an experiment or simulation. So I have one side of theories to explain how we do the calculation on one slide. But if you have any questions, then just drop me in. 00:12:31.000 --> 00:12:34.000 So how do we do this 00:12:34.000 --> 00:12:38.000 Well, we don't do it 00:12:38.000 --> 00:12:50.000 He said, what we do is we we split our vector potential for the waves into two parts. For the vector into two parts 00:12:50.000 --> 00:13:05.000 One part is a laser, it's gonna get classical yog, because the laser is close to being a coherent state. And the other part is the radiated field to an electron radiates photons, or maybe there's some loop effects to do with electromagnetic field. That's a quantized part 00:13:05.000 --> 00:13:21.000 We take the standard version of QED. So it's the three parts. This is the three fields, the electromagnetic field. This is the three fermions, and this is the interaction. And now we split into two parts. We've got an interaction between 00:13:21.000 --> 00:13:29.000 And between the elements and the quantized field of the radiation field 00:13:29.000 --> 00:13:30.000 I would just rearrange this 00:13:30.000 --> 00:13:43.000 Remove the introduction of the laser into the free particle theory, and the consequence of that is that the equation of motion that we have to solve for the electrical electrons, i.e. the Dirac equation, is modified 00:13:43.000 --> 00:13:48.000 By placing the potential of the data inside the verification 00:13:48.000 --> 00:13:53.000 And that's the thing I could solve for in order to introduce this interaction into laser tunnel 00:13:53.000 --> 00:14:01.000 Now, we don't have many closed form solutions of the Dirk equation in a given background, but one of 00:14:01.000 --> 00:14:16.000 We can solve for the recreation pool is plane life. Using the plane wave to have to model a laser. You might argue that a laser focus laser isn't a plane wave. That's right. But we're going to use these solutions in a circular realm that we want to describe 00:14:16.000 --> 00:14:30.000 Okay, so the leading process that we have is just that single vertex. This is an example not content scattering. The lecture comes in, collides with the laser, produces a hard 00:14:30.000 --> 00:14:40.000 The double line represents the part that we're using this solution to the equation of the plane wave. These are all costs, it's a Volkov, the Volkov electron 00:14:40.000 --> 00:14:47.000 And if we wanted to, we could expand this double line in interactions with the laser and look at what happened to it 00:14:47.000 --> 00:15:01.000 What interaction related to interactions related, etc. But we don't typically do that because first of all kinds of water, so we need wall orders, and secondly, we have the all order solution. So there's no reason to objectively fund it 00:15:01.000 --> 00:15:05.000 So this is normal content scattering 00:15:05.000 --> 00:15:12.000 It might seem strange that the leading order process is this throughput function. So normally in QED 00:15:12.000 --> 00:15:24.000 I'm also like this is kinematically is one of the two vertices here because we've got a laser field interacting with the electrons 00:15:24.000 --> 00:15:37.000 That's able to donate energy, momentum or absorb energy momentum from this interaction. So that changes the usual kinematics. So that means there's a regional phase space where this collagen 00:15:37.000 --> 00:15:41.000 That's why legal order process is just a single vertex 00:15:41.000 --> 00:15:46.000 So this is not encounter scattering. We already saw pegation 00:15:46.000 --> 00:15:59.000 I've become there. So we may even use the word nonlinear to describe these to differentiate them from all standard QED processes because of the nonlinear interaction between the laser background and the charge 00:15:59.000 --> 00:16:08.000 Before we also have at least proposes like one photo annihilation or photo adsorption, but we don't tend to 00:16:08.000 --> 00:16:19.000 Okay, mainly because it's difficult in a laser port to bring electrolyte photon, and the outgoing phase space was smaller for these 00:16:19.000 --> 00:16:23.000 So typically, these are the ones most interesting experiment. 00:16:23.000 --> 00:16:33.000 We also have signals from loop processes, like, mass operator, you can use your QED. It just contributes to the mass renormalization of the electron. But now people 00:16:33.000 --> 00:16:50.000 the laser there this experimental signal. So one of the signals of this this interaction, for example, is the spin of the electrons as it collides with the laser flip in a non-radiated way. So there's no virtual photon here, slipping flip. That's something 00:16:50.000 --> 00:17:08.000 who measured in experiments, polarization operator, another example of a loop process where we have an experimental signal here and signal price similar. So it's a photon interacting with a virtual electron positron pair, which is polarized by the laser. The signal there is a change of the polarization of the photon 00:17:08.000 --> 00:17:22.000 So it might have a vacuum biorefringent, that's essentially the process that they're trying to measure in experiments like to be that sort of high therefore helps. And then we have a matrix operator, which is less well studied because it's got three vertices, so it's a higher order. 00:17:22.000 --> 00:17:26.000 But principle, we do have some 00:17:26.000 --> 00:17:36.000 Okay, so that's a little bit about the background. I wanted to talk a bit about what people are looking for in experiments, because I think that's more accessible 00:17:36.000 --> 00:17:49.000 So two experiments refer to the texture again, experiments are going to differentiate themselves by a different source for the strong field or a different source for the high field. So the strong field 00:17:49.000 --> 00:17:52.000 Sorry for high-pile facilities 00:17:52.000 --> 00:17:58.000 my optical focus beam, so energies of a few EV at the interaction point. 00:17:58.000 --> 00:18:04.000 strong fields 00:18:04.000 --> 00:18:20.000 Studies around kev, poly to crystals. So the Na63 experiment 7, for example, takes the electrons from all the SDS, lies them over into crystals, and they enter crystalline field there actively known field 00:18:20.000 --> 00:18:28.000 Also, Google fields. So splitting of photons in Coulomb fields or the change, the scaffolding of photons in Coulomb fields 00:18:28.000 --> 00:18:39.000 As an example being so long, we talked about as well, and such a visual context. So that's kind of the different strong fields that we could consider. In terms of the pro beams 00:18:39.000 --> 00:18:55.000 Doing experiments at high-mile facilities, you want to have some vascular beam. Unfortunately, typically a Linac is not co-located with that mobile laser facility, so acceleration of electrons needs to happen on the surface. And so that's normally done by laser weight cube acceleration 00:18:55.000 --> 00:18:59.000 Josh Jets. 00:18:59.000 --> 00:19:13.000 That's our electron probe, a photon probe, you might combine them with a target to give a restore on sort of photons, or use a secondary week later to produce quantum scattered source or use crystal, or even thermal emission 00:19:13.000 --> 00:19:28.000 If you've not seen that, well, if you've seen Laserpoint before, you have definitely seen a plot like this. Every laser podcast I have one in, which is explaining why people are interested in using lasers to produce the sound field. So on the horizontal axis, we've got the decades 00:19:28.000 --> 00:19:43.000 And then the vertical axis, we've got the maximum intensity produced in a laser in that decade. So obviously lasers were invented around the 1960s and various inventions have allowed to get to higher intensities, higher intensities allow us 00:19:43.000 --> 00:20:00.000 More and more of these lasers. OPCPA was the innovation that led to the Nobel Prize in 2018. And this part is actually slightly outdated now, but there'll be other data points here. So the point is that 00:20:00.000 --> 00:20:18.000 What the investment is going into high-partless facility because to be able to reach high intensity allows to do more interesting experiments. And so I was trying to make the argument in talks like this that high-powered facilities are a great place to do fundamental physics 00:20:18.000 --> 00:20:36.000 Okay, this is another thought, which is similar, different laying facilities by decade. The only thing I want to point out here is the most recent laser facilities around here are accessing intensities where QED is the dominant effect in experiments. So we've 00:20:36.000 --> 00:20:47.000 Dynamics which are dominated by visual pathodes. Here we've got avalanche type cascades, acutely cascades producing photons at all these pairs. 00:20:47.000 --> 00:21:03.000 Okay, I want to give an example of all optical experiment before I talk about particle physics side of things. And I realized being here, I should really have talked about Gemini since it's not very far away, but when I made slides different later. So 00:21:03.000 --> 00:21:06.000 If you're doing that. 00:21:06.000 --> 00:21:17.000 The, one example of the whole experiment is a recent start at the facility, the Center for Relative Laser Science in Gangzhou in South Korea 00:21:17.000 --> 00:21:34.000 So this is kind of typical setup. You have your main laser beam collides with a gas jet or a gas cell to ionize particles to liberate electrons, which are then accelerated by acceleration apart from that main beam being is then peeled 00:21:34.000 --> 00:21:36.000 I refocused the interruption point 00:21:36.000 --> 00:21:38.000 The acceleration 00:21:38.000 --> 00:21:54.000 And so here, this is the gliding laser, this is the tane wave that was on the previous slides, and you have the electron beam being coming in, and this is… in this case, they measured nonlinear Compton scattering. They matched the electron being downstream using Linac screens 00:21:54.000 --> 00:22:06.000 And they separate products for the reaction using magnets and later for the photons they need to iso screen, which is a bit like acting like a 00:22:06.000 --> 00:22:18.000 This is an example of a laser matriot accelerated spectrum. So typically it has a narrow peak at energet 00:22:18.000 --> 00:22:35.000 Which is, of course, very good. The problem is there's quite a tail here, so the if you want to do anything with precision with laser weight, you have to take into account the fact that you've got this long tail, and that's not just a matter of force 00:22:35.000 --> 00:22:42.000 The advantage of using lighter weight acceleration is that you can do acceleration on a very small scale. So you don't say you don't need to do much. 00:22:42.000 --> 00:22:45.000 Sorry, I should consider 00:22:45.000 --> 00:22:55.000 But the short-to-shot reduce diversity is quite poor in general, although it's getting better. So if you want to build up statistics with collisions, it's difficult, said simply you choose collisions which 00:22:55.000 --> 00:23:00.000 overlapped really well, and then you analyze those. 00:23:00.000 --> 00:23:05.000 So the car was experimenting, they measured electron spectrum, so that's kind of the idea 00:23:05.000 --> 00:23:12.000 So they've got agreement with pollution from QED, just by way of 00:23:12.000 --> 00:23:22.000 referring to the premises, the intensity parameter 10 and the strong QED parameter is not one, but it's 0.1.3. I think the best that they got 0.4 00:23:22.000 --> 00:23:31.000 So, it's spectrum down the tail of the agreement gets a little bit more detail. 00:23:31.000 --> 00:23:43.000 This is some parameter space for different experiments among the Hampton scattering in the horizontal plexus, we've got the intensity parameter. So that's the charge field 00:23:43.000 --> 00:23:50.000 The Creek towards the strong field towards the diagonal line, and we get to higher strong field effects that we get over here 00:23:50.000 --> 00:24:00.000 Medical access is the energy parameter. So it's to do with the center of mass energy. It's only of the order about 0.1, 0.01 for these experiments 00:24:00.000 --> 00:24:08.000 So you've got these series of experiments that are being performed for the lasers where you go into higher and higher nonlinearities, it's charge 00:24:08.000 --> 00:24:20.000 And then various experiments, they're actually being commissioned or take notes, which will really push this to much higher values of the synthesis. So really looking at really highly nonlinear interactions of the background 00:24:20.000 --> 00:24:30.000 In contrast, what are these experiments here. So these OC stock at the problem from the other side. They don't start with high power latency. They start with that 00:24:30.000 --> 00:24:35.000 Then they use a moderatorizer in order to 00:24:35.000 --> 00:24:46.000 What's that? Thank you for the slack and Luxies requires that phase and I'll talk a bit more about Luxy in a second 00:24:46.000 --> 00:24:58.000 So they have the advantage that they can go to higher energy, but the sample rate is less so they can't probe this nonlinear function as much, but I'm going to make the argument that's fine 00:24:58.000 --> 00:25:04.000 Also, because they're using a laptop, they've got narrow about source of electrons, so they can 00:25:04.000 --> 00:25:09.000 Reproduction is good, so you can build sophisticated. 00:25:09.000 --> 00:25:20.000 Just by way of interest, this kind of overlap between particle physics and laser physics, I think, is something that's attracting more and more people. Last year, we participated in this 00:25:20.000 --> 00:25:30.000 Exercise run by certain every five years to solicit inputs to the European strategy for particle physics. We run for QED, such as things and 00:25:30.000 --> 00:25:47.000 The heads of groups at different places in Europe, and we had some guest authors from outside of Europe some of these high powers, some of these countries. Laser physics is not quite as established, but particle physics, obviously laser emotions colliders 00:25:47.000 --> 00:25:51.000 It's slowly starting to consolidate into larger and larger groups. 00:25:51.000 --> 00:26:07.000 So I want to talk about this lips experiment because it's maybe more interesting for the particle side, but also UK is quite well represented. So look see stands for laser on axial experiment and it 00:26:07.000 --> 00:26:09.000 That's right. 00:26:09.000 --> 00:26:27.000 institutions from the Uk. We've got Manchester, and Plymouth. And the idea here is to use the electron beam that drives the EU Xfel. So that's a 16.5 Gb electron 00:26:27.000 --> 00:26:39.000 And it's a similar kind of sound to what we saw in the Carlos experiment 00:26:39.000 --> 00:26:44.000 It's just separate parts of the reaction and 00:26:44.000 --> 00:26:48.000 Separate them from the hydrogen 00:26:48.000 --> 00:26:55.000 What is an example of what I think this can bring to this field 00:26:55.000 --> 00:27:03.000 And that's associated by this ugly photon spectrum in the quantum schedule 00:27:03.000 --> 00:27:08.000 By having a Linac behind this, we have 00:27:08.000 --> 00:27:23.000 Bush now programming, which means that we can measure what's happening in our scattered total spectrum to a higher precision just by a bit of statistics, but also by knowing what's the nature of the collision 00:27:23.000 --> 00:27:33.000 Here's an example. So, this is a log plot of the number of photons produced by crossing of the electron beam, and the laser mostly 00:27:33.000 --> 00:27:36.000 These are different intensity paraches 00:27:36.000 --> 00:27:49.000 What we see is for site order one, we see a parbonic edge to do the edge of the first harmonic interaction with the laser. As we increase the intensity, this harmonic edge gets washed out and it's redshifted 00:27:49.000 --> 00:27:58.000 I learn the values of precisely what I want, we see a very strong signal. By having a higher precision 00:27:58.000 --> 00:28:06.000 Probing, we can measure the position of this edge, which is much better access to what's going on in the physics than just terms of yields. 00:28:06.000 --> 00:28:14.000 The position of this content, as it's called, is in both formulas. It's basically just a fraction of the photon energy 00:28:14.000 --> 00:28:20.000 By the natural attitude. So people have actually been with the electron energy sciences. 00:28:20.000 --> 00:28:24.000 Each has this energy process, not so important point to 00:28:24.000 --> 00:28:30.000 The interesting thing is where the intensity happens. Remember, the psi parameter is the charge for your cup 00:28:30.000 --> 00:28:42.000 Which are comparative linear TV. Linear QD, we factor out positions where are eventually formula that's calculation 00:28:42.000 --> 00:28:46.000 The presence of the laser is introducing these nonlinear corrections 00:28:46.000 --> 00:28:53.000 As we increase the intensity parameter, we're picking up more than interaction with laser higher and higher order 00:28:53.000 --> 00:28:59.000 So weight size of order one, then we can't truncate this series anymore 00:28:59.000 --> 00:29:13.000 And it says we have to include this interaction to all audits. So measuring the position of this edge as we change the intensity uses an experimental probe into this all order interaction predicted by our computer theory 00:29:13.000 --> 00:29:18.000 An interaction between the elections will be delays. 00:29:18.000 --> 00:29:24.000 We could essentially say, oh, okay, let's not look at emotional community, let's look at the production of classical electrodynamics 00:29:24.000 --> 00:29:26.000 They'll be more than a constant scattering 00:29:26.000 --> 00:29:42.000 And then you can see the picture of the latest quality edge is of how it changes as we change the intensity. So it's a leading order, which is that here. I factorize how a factor of H bar from this ether parameter to show that as we change the intensity 00:29:42.000 --> 00:29:48.000 We're picking up and becoming more and more quantum, if you like. And 00:29:48.000 --> 00:29:57.000 So one of the things about this here is people really care about the difference between classical and quantum physics. So as you change intensity, you're in more and more quantum corrections 00:29:57.000 --> 00:30:05.000 And so you can block whether content edges as you change it, what the energy is, as a function of f 00:30:05.000 --> 00:30:18.000 If site is small, very, very small, it's just an issue. If psi is too large, as you can see, if psi is too large, it's just nonlinear classical physics. The interesting thing is happening around time orbit plane 00:30:18.000 --> 00:30:25.000 prediction from standard linear community 00:30:25.000 --> 00:30:31.000 So my message for stuff like this is we really want higher precision over power 00:30:31.000 --> 00:30:38.000 Detroit's not really powerful methods at least, but using magnificent particle physics, higher precision 00:30:38.000 --> 00:30:44.000 This allows us to actually have a much better probe of dictionary 00:30:44.000 --> 00:30:53.000 So we have a measure electrolytic collisions. We also want to measure photonic collisions. So we do generate a photon beam electronizing an electron 00:30:53.000 --> 00:31:11.000 being a solid target, there's rent strong ponds. Or you can also get off part of laser to have a confidence gathered source of photons, which has the advantage that we have quite a high polarization grade, which allows us to do more specific theory 00:31:11.000 --> 00:31:18.000 We'll be at the cost that we have much lower energy. Also considering using a crystal radiator 00:31:18.000 --> 00:31:22.000 structure target, essentially, gives us 00:31:22.000 --> 00:31:29.000 kind of narrowbandish sorts of protons, achieve them, ICS source 00:31:29.000 --> 00:31:36.000 So what's the signal for tokenized collision? So we've seen already is pair creation 00:31:36.000 --> 00:31:47.000 So thinking about this process of tag creation is if you take a single laser protocol and you take the high energy photons that we produce from that source, the the mass energy is too low to create a pair 00:31:47.000 --> 00:31:54.000 You have to answer quite a large number of license before you get to the threshold where you create a pair. 00:31:54.000 --> 00:31:56.000 So if it looks like on the 11 protocols. 00:31:56.000 --> 00:32:05.000 That means an alternative signal, leading order and lead signal. Scales with size of power 32. 00:32:05.000 --> 00:32:11.000 The yield of pairs, the photons is colliding with the laser. If we just had 00:32:11.000 --> 00:32:17.000 But doing all the QA with this this kind of 00:32:17.000 --> 00:32:29.000 But as we increase psi, we have to include higher and higher orders because obviously this is a series of size model, including all orders. And the result of that is there's actually a suppression of pair creation 00:32:29.000 --> 00:32:42.000 And this can have here, and this totally is the curve away from the interpretive but highly nonlinear prediction is our signal of all order interaction between the charts in the background. 00:32:42.000 --> 00:32:50.000 albeit now. Figration, which is a fully quantum process 00:32:50.000 --> 00:33:02.000 Okay, so even just reading all the processes, we also want to look at high order processes. For example, cotton showers, you can imagine your electron being close to the laser and more than one photon 00:33:02.000 --> 00:33:20.000 Now, something's a bit different in interaction with laser pulses than possible beams. Pascal beams, if you have two energetic beams colliding from a rest frame of one beam, it looks like the other beam is relativistically pancake, right? Longitudinal 00:33:20.000 --> 00:33:27.000 But here we go home with training focused, which doesn't run as a contract. 00:33:27.000 --> 00:33:35.000 So the consequence of that is that the longitudinal scale of the lighter bolts allows for much higher order dimension 00:33:35.000 --> 00:33:45.000 And if you consider a higher basis like this, the propagator has a virtual part and real parts 00:33:45.000 --> 00:33:48.000 Just by the integrity relation with virtual power can't propagate very far 00:33:48.000 --> 00:34:00.000 So that means that higher order processes like this are dominated by the propagated real. So here, for example, an electron making a photon renal propagates like a normal electron. 00:34:00.000 --> 00:34:07.000 This is kind of a silent approximation that we use to calculate higher order processes 00:34:07.000 --> 00:34:09.000 So here's just an example 00:34:09.000 --> 00:34:24.000 This is for 8 of the electrons of scimetha, or we can have it, a bit lower than what energy we have, let's see. And this is using the Tarnigan open source simulation code, which is being developed by Tom Blackburn at the University of Gothenberg. 00:34:24.000 --> 00:34:35.000 So we see is chi of two, time a naught used by different groups of people doing the same thing. Chi of 2 for electrons around 00:34:35.000 --> 00:34:40.000 average, most expected thing to happen is that they don't make any changes in their life, basically 00:34:40.000 --> 00:34:46.000 As we increase time, for example, 7.5, it's most likely that neutral electron emits an average declining 00:34:46.000 --> 00:34:55.000 So even though the second order processing is more promptful than the leading order process, it still preservatively 00:34:55.000 --> 00:34:57.000 However. 00:34:57.000 --> 00:35:03.000 It's been a while that there's an exception to this. And this happens if we 00:35:03.000 --> 00:35:08.000 Imagine that we have this length of the prompt set. Imagine we can make it really large 00:35:08.000 --> 00:35:18.000 And what happens to these three-level processes like longer, is that in the large chi limit, they scale as ubiquity has taken over two-thirds. 00:35:18.000 --> 00:35:31.000 Now, this is significant because you can ask the question, well, what if we could reduce I of order 1,000? We solve the process for doing that already in the lab. What would that mean about this unit fraction 00:35:31.000 --> 00:35:36.000 Well, if I was in other countries, that's all the 00:35:36.000 --> 00:35:48.000 What that means is that this kind of conservative series here is not something that we can pronate. We could have the situation where we could just say, oh, we just stop our 6 functions 00:35:48.000 --> 00:35:58.000 Instead, we have such an intense backgrounds so large, that would mean we'd have to include all interaction, not just in the laser, but also all orders I measure 00:35:58.000 --> 00:36:01.000 So somebody will say that QE 00:36:01.000 --> 00:36:05.000 when we have such an intensity of 00:36:05.000 --> 00:36:17.000 Now it's not just country level diagrams, it's also loops. So polisation operator and electron mass operators go like alpha chi 00:36:17.000 --> 00:36:20.000 Typically, in calculations, we don't really include 00:36:20.000 --> 00:36:25.000 Right at the corrections, because as we saw, things are dominated by things being real 00:36:25.000 --> 00:36:31.000 So if we had other kinds of two-thirds, not only would we have to include them, but again, we'd have to completely 00:36:31.000 --> 00:36:49.000 There's a nice series of experts in the 70s and 80s where they calculated leaves a higher order, domain with commuters and morality. And they go all the way up to three loop and they found that the divergence with Chi's strongest 00:36:49.000 --> 00:36:53.000 Chains of organizational operations have reported 00:36:53.000 --> 00:37:03.000 And so there's a conjecture called the Rocky conjecture that if we have a very intense field, so if the field is locally constant, and it's plain wave in nature 00:37:03.000 --> 00:37:09.000 The true expansion of beauty is an opportunity, but it's held by kind of two-thirds 00:37:09.000 --> 00:37:20.000 Okay, so just to kind of underlying that fact, because I think it's kind of interesting maybe not so long, it's not a QED, we've got a process of n vertices that goes, like, upper QD to the power n to the probability 00:37:20.000 --> 00:37:33.000 We get more and more accurate tests, we include radiative corrections, so loops, a high value times alpha. And this particular series is the thing that's been tested really well when people say that QUD is the best 00:37:33.000 --> 00:37:39.000 That's this one very 00:37:39.000 --> 00:37:48.000 Well, I'm mainly talking about is when we have an attached laser pulse. These functions that have been functions of the intensity parameter and as they just made more intense 00:37:48.000 --> 00:37:57.000 This shifts the importance of this parameters specifically, the leading process that's going to be dominant 00:37:57.000 --> 00:38:11.000 What we're saying now with this objection is the high value regime, you don't know what, but we can't expand like this for many corrections. We have to include all orders of this. So we want to be able to write down. So I think it's quite compelling that 00:38:11.000 --> 00:38:18.000 There's a region of Qd. Where we get absolute calculations. So we really need impact 00:38:18.000 --> 00:38:21.000 Library is a final topic called radiation reaction 00:38:21.000 --> 00:38:30.000 So radiation reaction is a very old topic going all the way back to like Lawrence and Abraham and 00:38:30.000 --> 00:38:40.000 But it's a general question of what do you do and feel so intense that the radiation affects the trajectory of your charges. 00:38:40.000 --> 00:38:45.000 So I'm going to provide plasticity first, and then 00:38:45.000 --> 00:38:52.000 So, if asked you to calculate the radiation piece by electron and it collides for laser. 00:38:52.000 --> 00:39:03.000 How do you do that? Well, an undergraduate at some point you can solve the Lorenz equation. This is the Lorentz equation by Brandon with a potential 00:39:03.000 --> 00:39:09.000 But we use that to get trajectory, and then using trajectory currents which we use the wave motion to get to the radiation. 00:39:09.000 --> 00:39:20.000 But I need to see a problem that to solve the first line for the trajectory, we need to know the radiation, the flow of the radiation trajectory 00:39:20.000 --> 00:39:32.000 So pretty much this couple set of higher order groups. What we learned in undergraduate physics. 00:39:32.000 --> 00:39:39.000 The potential is the laser, or the propagation fuel, just classically as well. 00:39:39.000 --> 00:39:47.000 The laser interaction isn't E, so this faculty is being absorbed in case you think I have to go on the factor of E there 00:39:47.000 --> 00:39:58.000 Then you purchase the token, you say, oh, the light's really intense, the radiation is going weak, so 00:39:58.000 --> 00:40:09.000 we put the laser into the explosion, we've solved for the trajectory of the electron and laser, and then we use that trajectory in the equation to calculate what radiation the electron uses. 00:40:09.000 --> 00:40:19.000 So it just rolls over. Okay, good. 00:40:19.000 --> 00:40:28.000 I was so confused with my computer, and that's what the upside here, but I'm sure. Okay, thanks for the explanation. So 00:40:28.000 --> 00:40:50.000 Yeah, so much do that fine, but imagine now that the radiation reduced is intense, or there's not there, or this information happens for a very long time. Then usually at the high order, so you can take that radiated field, and then you can plug it back into the equation of motion for the Lorentz equation, and you just solve for the new trajectory, take into account the fact that the radi 00:40:50.000 --> 00:41:06.000 Has effects on the trajectory of the electron. So that's new trajectory, and then you put that into your weight equation, you get a benefit correction for the radiation, and you continue doing this until you have a ton of equations. And if this effect was very strong, you have to include all of these 00:41:06.000 --> 00:41:17.000 Now, I'll go through that. If you do not leave summation procedure, you end up with something called the blind state of Han Derek equation 00:41:17.000 --> 00:41:23.000 We're either to talk about approximation plan that we use describe what happens with electrons 00:41:23.000 --> 00:41:28.000 Starting with my malicious question. 00:41:28.000 --> 00:41:45.000 So here we have the Lorentz equation gain over and this is the part that's classical radiation reaction. So we see it's nonlinear in the laser field, and it's nonlinear of the electron, and it's got our radiation reaction parameter 00:41:45.000 --> 00:41:55.000 Okay, so we solve this in place form, not always, but we can solve it in a framework background, and that's great because you want to look at lasers. 00:41:55.000 --> 00:42:02.000 And one of the predictions of that is the following. If you calculate the 00:42:02.000 --> 00:42:07.000 So, the measure of the electron after it scatters with laser in the same way 00:42:07.000 --> 00:42:19.000 a fraction of the incoming of anxi. If it's a plane wave, that ratio is exactly 1. That's the Wilson-Woodloop theorem. Plane waves come up, accelerate electrons 00:42:19.000 --> 00:42:28.000 But I think with radiation, that's not the case. And because radiation parameter here, which depends in a nonlinear way on the density of Bernard plates 00:42:28.000 --> 00:42:33.000 Okay, so that's the classical case, but we're obviously interested in QD 00:42:33.000 --> 00:42:45.000 Quantum radiation reactions is a general question about what happens. It's not… obviously, we don't think photons, that's photons create pairs, maybe there are loops. There's a much broader question in general 00:42:45.000 --> 00:42:54.000 However, you can make a connection between QD and classical prediction by meaning in the gradient theory 00:42:54.000 --> 00:43:11.000 And what diagrams are important? Well, of course, contour staffing, you know, all that goes in emits a photon, you know, recalling the electron, that's clearly an effect of radiation reaction. But also, in order to recover the cluster prediction, you need to at least 00:43:11.000 --> 00:43:20.000 So it's kind of interesting that it looks reassess with quantum stuff, but actually that's the limit we've got this. So Luke's really important in our 00:43:20.000 --> 00:43:28.000 So, we understand how to calculate, at least for leading orbit and QED, but the general problem is unsolved 00:43:28.000 --> 00:43:44.000 Very successful, that showed a method of radiation reaction and a recent paper showing that there can differentiate the QD 00:43:44.000 --> 00:44:04.000 radiation reaction form factor radiation reactions. But I think that we can do better. And one example of where we might be able to do better is in the following setup. So accelerate and dance 00:44:04.000 --> 00:44:15.000 So again, as I've been trying to extol the virtues of Linux and properties of electron beams in this talk, this is about an energy standard around 1%. 00:44:15.000 --> 00:44:17.000 And it's also a 00:44:17.000 --> 00:44:20.000 And there's very much 00:44:20.000 --> 00:44:26.000 Which highlights around 10, even a nonlinear regime 00:44:26.000 --> 00:44:43.000 The strong field route is small, but the radiation reaction parameter is over a few percent. and the plane here is that by using the precision that you get from a mining methods from particles and accelerated physics, always nice physics, we can find signals of radiation actually not in the 00:44:43.000 --> 00:44:46.000 But totally you're getting spectrum 00:44:46.000 --> 00:44:48.000 I'll give some examples 00:44:48.000 --> 00:44:51.000 simulations that we perform. So 00:44:51.000 --> 00:45:03.000 This is an example of what happens to the electron beam energies after the collision. So there's no radiation reaction to the purple dashed line here, nothing happens. 00:45:03.000 --> 00:45:17.000 Before the radiation reaction were classical, then what happened to this electron beam energies that they all get shifted there, in this case by about 10. All the electrons interact with the laser classically and they all radiate continuously 00:45:17.000 --> 00:45:21.000 Contrast that with prediction 00:45:21.000 --> 00:45:29.000 Not seen, but the expectation value of this GUI turns about the same, but the variance of the training is very spread out, it's 00:45:29.000 --> 00:45:40.000 And that's because one of the features of radiation emission in QD is it's stochastic. So you could have an electron pass through the laser without emitting once. It's another one known as quenching 00:45:40.000 --> 00:45:53.000 Or it lines the electron theorem might get to higher regions of the intensity of the laser beam, because it only makes stochastically than it does classically 00:45:53.000 --> 00:46:00.000 So we have quantum effects which contribute to potentially the 00:46:00.000 --> 00:46:03.000 Spreading the electron emission 00:46:03.000 --> 00:46:12.000 When is that starting to occur? So this… this is kind of transverse momentum distribution along the electric field direction for laser 00:46:12.000 --> 00:46:14.000 And you see that in the 00:46:14.000 --> 00:46:19.000 No radiation case that's most readily learned in the quantum case there is 00:46:19.000 --> 00:46:34.000 two dimensions like this. So this, you can see obviously the altitude goes down in the concentration center will spread in the transverse distribution. So the idea would be to be able to measure something in the tails 00:46:34.000 --> 00:46:42.000 To differentiate quantum from classical radiation reaction unambiguously. You can also rotate the polarization plan for later 00:46:42.000 --> 00:46:46.000 It should be around depending on what polisation plan is about 00:46:46.000 --> 00:46:52.000 Sorry. So the collaboration form at the moment, obviously in difficult times between 00:46:52.000 --> 00:47:03.000 So hopefully we'll have more to report in the future. I thought it was a nice demonstration of collaboration between 00:47:03.000 --> 00:47:05.000 Okay, so 00:47:05.000 --> 00:47:07.000 That's my summary. 00:47:07.000 --> 00:47:23.000 I recommend seeing that you can do some really nice things with fundamental physics on high-power lasers. I only talked about QED because I think there's a lot of interesting things happening there. We can do things with lasers and natural reprocesses and DSM, but I decided to focus on QB for this talk. 00:47:23.000 --> 00:47:34.000 The interaction between the charging fields is a non-preservative prediction of quantum field theory, which we could test in experiment. We don't have many of those typically non-preservative predictions that we have require 00:47:34.000 --> 00:47:45.000 large providers are not difficult to get at, but in the interaction between lasers and electrons, this should be easy to access 00:47:45.000 --> 00:47:52.000 I think it's a growing synergy between native effects, which is the engineering experimental prospects, and definitely developments in simulation theory 00:47:52.000 --> 00:48:08.000 And this is including regime to my uni clearly becomes uncoupled with no methods to calculate this at the moment. So we definitely need impactful experiments. And I think that using precision, crucial precision 00:48:08.000 --> 00:48:13.000 Rather than going to High Laser house for your attention. 00:48:13.000 --> 00:48:25.000 Thank you