When building a physical theory must have a foundation to build on. A theory of everything, for everyone. It was as particle physicists created his “periodic table”, the so-called standard model.
When Mendeleyev designed Periodic Table of the Elements, he noticed that it was possible to predict the properties of the elements missing in the system, those who no one had yet seen. In the same way it is with the standard model, it is taken here and there – there are holes to fill.
Pang! Two protons Collide (inset simulation) in the middle of the Atlas detector at CERN with the power of two mosquitoes that run together at the speed of light. The devastation is total. Splitter of mosquitoes can be detected by several tons of iron. Please note that no detector elements are mounted in this picture. The large tubes are the eight superconducting toroidal magnets to bend the particles. The rest is the case.
One of the holes has been filled in with the Higgs boson, or the Higgs particle as it is known. It was just to prove it, and it made Man on 4 July 2012.
The standard model is by no means complete after that date. There are many gaps to fill in, with many hypothetical particles and symmetries, but this article can unfortunately not go so deep that a full explanation would require. Nor can we go into the general theory of quarks and other subatomic particles.
How Higgs particle found know Sarah Strandberg, senior lecturer in elementary particle physics at Stockholm University, who works with the ATLAS experiment at the LHC at CERN.
– The experiment is on to collide protons in frontal collisions at nearly the speed of light 40 million times a second, and see what comes out of the collisions, she says .
– The protons will in bundles of billions of protons in each, they can rather be likened galaxies. Mainly father galaxies across each other, but about twenty particles collide each time and spread lots of particle shrapnel. If the crash is good enough, in the sense that the protons not only be broken without the collision energy also creates new, high-energy particles, occurs a trigger situation. In that case, you save all the data about the crash for further treatment, but in most cases you forget everything.
Output from “shrapnel” sensors are Atlas filtered in three steps with increasingly stringent criteria, levels 1, 2 and 3.
– Level 1, or first- nivåstriggern, is a study of the energies deposited in the Atlas energy meter, calorimeter, and the energy is too low, nothing is saved. Level 3, or event filter, giving despite careful screening an output frequency of 400 collisions per second, where all data is stored on magnetic tape. Of these contains roughly a readout per day data on a Higgs particle, says Sara Strandberg.
The innermost detector , the pixel detector, has 80 megapixels, consisting of reverse biased diodes, which leaves a voltage pulse each time the traversed by a charged particle. All these 80 megapixel can not be output at all times, but they are stored in a FIFO queue that is 2.5 microseconds long. The system takes 2.5 micro seconds to make a decision and if it gets the thumbs up, fed the 80 million pixels out. Otherwise, subject to the.
The pixel detector is a rolled-in digital camera with 80 megapixel resolution, in which the image sensor turns inward. Proton beams meet in the center hole and particles jets through detector cards, small stacked circuit boards around the detector walls. All conductors carrying out image information. Picture: CERN
– After storage and calibration of the signals – which occur in a data farm called Tier 0 – sent data to all the 38 participating countries for further processing – via data farms Tier 1 and Tier 2 – because it requires too much computing power to a single organization to manage it, says Sarah Strandberg.
Return to the standard model. As early as 1964, long before they knew the mass of the Higgs particle has, namely 125 gigaelektronvolt, scientists had predicted the particle’s other properties in the standard model. It also foretold that the standard model would collapse like the idea of not one particle Higgs particle exist. But before they had understood the Higgs mechanism, that explains why some particles had mass while others did not, could not say what the Higgs particle consisted of and how it would disintegrate, and thus do not know how to detect it.
Higgs particle is not inside the proton and just lies there and thrive, but it is created in the moment of collision. One way to get a Higgs particle is to collide a quark and an antiquark. In everyday language we say that ordinary protons consist only of ordinary quarks, but in fact they consist of this and a whole hodgepodge of quark-antiquark pairs that constantly created and annihilated under the Heisenberg uncertainty relationship. With some probability, therefore, a quark from a proton and an antiquark from another proton collide and create a Higgs particle. The most common is that two gluons, thus the strong nuclear budbärarpartikel and that holds together protons, collide and create a Higgs particle.
When a quark and an antiquark annihileras they meet, is fully converted to energy, and this energy from the new particles can be created with certain given probabilities, namely anti-particles, electrons, Higgs particles and so on. The Higgs particle is created then as a result of the collision quark-antiquark with some probability – but that’s only half the story.
The whole world is built up of quantum fields. Higgs field is everywhere in the universe. When one adds energy to the field by colliding two protons with enough energy, excited field, and there arises a ripple in it. The Higgs particle is an excitation of the field. Sounds tricky do you think?
Higgs field is not one of those blue luminescent force field that they have in the “Star Trek”. Consider an electric field that exists between two electrodes. It does nothing, it’s just there and represents energy. In order to set an electron in the field, it interacts with the field, get a piece of the field’s energy, converts energy into motion and accelerated towards the positive electrode. For it into a neutron in the same field, it interacts not at all because it is neutral, and have no energy at all of the field. The neutron continues straight ahead.
Higgs field represents the self-energizing that is everywhere in the universe, and a particle that interacts with the field can get a Some of viloenergin and convert it into mass – since energy and mass are the same thing. Other particles, such as photons do not interact with the Higgs field, and receives no mass, no rushing the speed of light.
Electrons, which may their mass from field, plays a crucial role in atoms and molecules to be formed and stick together. If the Higgs field suddenly disappeared, would all matter collapsing when massless electrons went off with the speed of light, impossible to be captured into atoms and molecules. Nothing we know would exist, much less ourselves.
A Higgs particle can decompose to various other particles, with the highest preference (56 percent of the time) to two bottom quarks, but in rare cases, to two photons, two gluons (8.5 percent chance), two tau or two Z bosons (3 percent), which in turn becomes example four muons. All of these, Atlas measure accurately.
The second most common decay (23 percent), however, two W-bosons, which turn decays to each example, an electron and a neutrino. The final permit includes two neutrinos, which are difficult to measure along, and then we can no longer reconstruct the mass of the Higgs particle, but only end up in the order of 120 gigaelektronvolt.
In addition to this squirt it around lots of other particles in the detector constantly from others, simultaneous collisions that create a bakgrundskvark- noise that makes it difficult to precisely detect the Higgs particle. This broad spectrum of outcomes and low resolution, in the case of neutrinos has made the evaluation difficult. But it went.
What has nature for the benefit of the Higgs particles? None at all. These are not present in the free state. The nature has the benefit of the Higgs field that gives things, ie particles their mass. Different particles are different heavy depending on how strongly they interact with the Higgs field, in much the same way as a logdörr interact more with air than an arrow shot from a bow. But do not pull the analogy too far – the Higgs field against sits not moving, it does not constitute “syrup” that makes particles to slow down. Both the arrow and the barn door fall to the ground after a while, to be blamed on gravity. It is as yet unknown how it works, but it is yet another interesting, not yet filled a hole in the standard model.
What can scientists do with the Higgs particles? Nothing at all, except to cough into a number of Nobel prizes. The particle acts only as an intermediary, a proof that the Standard Model is the way towards the great overall theory of everything, the Grand Unified Theory of Everything.
What will happen when you now soon cranks up the CERN large particle accelerator facility LHC to 2 times 6.5 Tera electron volts? Perhaps particle physicist Anna Davour she wanted in my previous article on dark matter (see Tech World 6/2014 or tinytw.se/morkmateria ). With luck, says Sarah Strandberg, maybe you can create wimp particles in the LHC. Maybe they are already in existing data. Wimp: s is another of the holes in the standard model may need to be filled in. In this case, they finally find out how the dark matter is created and can be put into better methods to find it in the universe.
Now: More detail on the particle discovered!
(Click the images below larger versions.)
A terrible blow
Image 1 shows a crash in detail. The Higgs particle is not at all inside the protons that collide, but is formed in the actual moment of collision. A free Higgs particle only live in .0000000000000000000001 seconds and time in that time only travel .00000000000003 meters. It can then decay into two Z bosons, which lives in 0.0000000000000000000000001 seconds. Each.
Do you understand what terrible bang it gets? On one attosecond is destroyed nature’s innermost constituents of a violent crash and become shrapnel that can penetrate rock.
But nature itself is much worse. Cosmic rays are much higher energies than that, and can go through the whole earth.
Atlas detector is built like a barrel, and inside it is different detectors in layers, wrapped around the jet pipe in the middle where the protons collide. Figure 2 shows a wedge of detector .
Deep seated trace detector that very deep down has a pixel detector 80 megapixels in several layers, a few centimeters from the collision point.
The reason for the high resolution is that you want to reproduce sönderfallspartiklarnas track in three dimensions, to to find out exactly where, therefore, from the collision they came, or if they came from a secondary decay a bit from the collision, or possibly from the cosmos in the form of cosmic rays. The Higgs particle is too short lifespan to be detected in this way. One must focus on its decay products.
The further out you come from beamline, the lower the resolution has detector elements, but the heavier particles can absorb and measure the energy of. By using different, heavier substances such as lead or steel, interspersed with detectors, one can find out which types of particles absorbed.
Exactly what type of particle is about, is determined by the detectors are activated. A photon (eg X-ray) will deposit all their energy in the electromagnetic calorimeter, but it leaves no trace in the inner detector, because a photon is electrically neutral.
A electron will also to deposit all their energy in the electromagnetic calorimeter, but it also leaves a trail in the inner detector.
Other, heavier particles, as protons and neutrons, will continue right up to the hadroniska calorimeter dump their energy there. The very tricky thing particles that we know today is muons, which reacts very little with calorimeters. They stopped anyway to last in myonspektrometern furthest out. Myonsystemet created enkomt to find the Higgs particle, for example, can fall apart into four muons, if no other system would suffice to find the particle.
You want to be able aggregating the energy from the collision all the particles, so that you know you found all the fragments. However, there are particles that can not be measured directly, as neutrinos. Since the kinetic energy of the collision must be preserved, according to the laws of physics, can still with the ordinary subtraction conclude that a neutrino must have formed and the direction it had gone.
To determine the energies contains detector of magnetic system, which bends the particle paths, so you can see how high energies they have. Low energy particles are deflected more strongly than highly energetic and anti particles deflected in the opposite direction towards the matter.
Deep sits a sol with the entire 2 tesla magnetic field along the particle beam, which bends of the particles in orbit around the beamline. The magnetic field is provided with a direct current of 7600 amps. If the particles are sufficiently energetic to slip out solenoidfältet hits on the toroidal field of 3.9 tesla which bends them in the front-back direction. Field is accomplished by 8 toroidal coils with a drive current of 20,500 amps!
Figure 3 show how the collision looks in “reality”, with an example at the bottom of 21 collisions in about natural size. The different colored lines are the decay particles of different type and energy. Most particles represent uninteresting, known physics. The two thick yellow lines are muons created out of a Higgs particle. The particle itself or its route is not visible in this scale, only the result of its decay. How do we know that the two interesting particles came precisely from the collision point? The coarse red lines in myondetektorerna (gray tiles extremely) represents the trigger conditions. After the ATLAS detector provided a trigger signal regard to all the data from all detector of the collision, and simulates all the particles the way back to the center.
The yellow line happened to meet in the collision point number four from the left, along with some other low energetic debris (red) that takes off in other directions. The two yellow and 11 red lines will together represent as much energy as the two component, destroyed protons, namely 7 Tera electron volts.
The two yellow lines represent along an energy of 125 gigaelektronvolt which adoption is the Higgs particle energy. When you have enough events that can be traced to a particle of 125 gigaelektronvolt that have fallen apart, they have found what you are looking for. Probably. It’s just statistics, but with enough events are statistics to proof.
The malfunctions arises when a particle strikes through one of about 100 million pieces of detectors ( Figure 4 ), A / Domvandlas and sent into a shift register which is mounted inside the detector unit, where data is clocked forward synchronously with particle packages.
The total flow into all shift registers are about one petabyte per second. There is more data than all of Europe combined telecom traffic.
Picture shows after treatment of data in four levels, thus Tier 0-3. Tier 5 is the scientists’ brains – as with all other research, the final answers from the ultimate computer brain, when scientists got together and encounter wet and ideas with one another. Read more about it in the article “Second time lucky for the LHC” ( tinytw.se/andralhc ).
Curve on Image 5 shows statistics from measurements of one of the decay types, namely the Higgs particle into two photons (H → γγ). The x-axis shows the total energy (mass mγγ in gigaelektronvolt) of two simultaneously detected photons.
If you get enough many events where you register two photons together represents 125 gigaelektronvolt they have been created from the same type of event: a previously unknown, decays particle.
The top y-axis indicates the number of events in this measurement, about 5000 in the area of interest. If you remove the background noise get the lower curve, where you see the incident at 125 gigaelektronvolt is 400 times higher than the background.
Image 6 When you add up the probability curves for all sorts of decay – photons, Z bosons, W-bosons, four muons, and so on – all point to 125 gigaelektronvolt with a security of 6 sigma or a billion times more likely than chance. There we have our DELINQUENT!
7: All countries with and counts on data from the Atlas Tier 1 is orange on the map.
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