The Higgs - the conceptual framework
The Higgs field
The Higgs field is named after one of the physicists who first postulated its existence in 1964 as means of explaining inconsistencies in the Standard Model, specifically, why some of the elementary particles such as quarks and electrons have mass, when they don’t really need it. As we have seen, such a field may also explain how the photon, whose rest mass is zero, and which mediates the electromagnetic force, differs from the W and Z bosons - particles with mass that mediate the weak interaction.
The Higgs field is not a force. It cannot accelerate particles and it doesn't transfer energy. However, it is conjectured that it interacts universally with all particles (except those without mass), thereby endowing them with their mass. We can't see or touch the Higgs field. The only way to know if it's there is to create a disturbance in it, like making a sound in air. This disturbance shows up as a particle - the Higgs boson[0]. Although the Higgs field has not yet been identified experimentally, something consistent with its particle is thought to have been discovered following trillions of high energy collisions between subatomic particles in the Large Hadron Collider (LHC) operated by the European Organisation for Nuclear Research (CERN) on the French-Swiss border.
Bosons are one of two elementary particles that quantum theory says make up the universe. By virtue of their specific characteristic of spin (the angle of a particle’s rotational axis), they permeate space, the best known example being the photon. The other classification of elementary particle is the fermion – quarks and electrons – which are the stuff of which matter is composed. By virtue of what is known as the Pauli exclusion principle, unlike bosons they are precluded from occupying the same space at the same time as other particles[1].
According to the Standard Model of particle physics which currently explains electromagnetism and the strong and weak nuclear forces, all the gauge bosons (particles mediating the interaction of elementary particles) should have zero mass. This is true for photons and gluons which mediate electromagnetism and the strong force. However, the W+, W-, and Z bosons, which mediate the weak force (responsible for nuclear decay), have lots of mass when they don’t really need it. In fact, they weigh in at about 80 and 90 gigaelectronvolts[2] (GeV), almost 100 times more than the proton This requires explanation, and since 1964 the current prevailing hypothesis comes under the umbrella of the so-called Higgs mechanism, which confers mass on other elementary particles by converting some of their energy into mass. The discovery of the gluon in 1979 and the W boson in 1983 were therefore necessary precursors to the identification of the Higgs particle over three decades later.
Like the four fundamental forces, the Higgs can also be visualised as a field, except that it occupies every part of the entire universe all the time and doesn't have a source. Also, just like the four forces, it comes with its own particle, but one which, instead of mediating a force, is thought to mediate mass[3]. The Higgs boson may therefore be described as a massive scalar[4] elementary particle with no intrinsic spin, which is why it is classified as a boson (gauge bosons have integer spin).
When physicists say that a force is mediated by a particle, they mean that the particle in question by its very interaction with other particles transfers information describing telling these other particles what to do. An electron in and of itself doesn't know that it's supposed to act in a certain way as described by electromagnetic theory, but a photon, by interacting with it, “tells it so” and that's what is meant by saying that photons mediate the electromagnetic force. So in a slightly different sense the Higgs boson mediates the Higgs field. Like all other particles, the Higgs gets its mass by interacting with ("swimming in") the Higgs field, and the Higgs field is the theoretical means by which all particles, the Higgs included, acquire their mass. The Higgs particle can be thought of as a dense spot in the Higgs field, which can travel like any other particle. It can be considered as being “like a drop of water in water vapor”[5], so the Higgs’ mass is such that it must interact with itself.
Every particle in the universe "swims" through this Higgs field, thereby acquiring their mass, and different particles interact with the Higgs field with different strengths. Some particles are heavier (have larger mass) than others. Our own bodies are composed of protons, neutrons, quarks and electrons, all of which have different masses, and the Higgs boson may well be the explanation. One commentator uses the analogy of walking through a field in which the air is saturated with pollen. “If you're wearing fleece, the pollen will readily attach itself to your clothes. However, if you're wearing a raincoat, the pollen won't attach itself to you quite as easily. That's how particles interact with the Higgs field. If the particles couple with the Higgs field, they'll acquire mass. If they don't, they won't”[6].
Another analogy, frequently used, is that of a popular celebrity who enters a room containing a throng of people who mill around her making it difficult for her to move through. If she were a particle and the throng the Higgs field, she would be interacting with it. If on the other hand, a nobody poked his nose into the room, no one would take any notice leaving him free to move through the assembled multitude at will. He would be said not to be interacting with the field. Thus, particles with no mass such as the photon don't interact with the Higgs field at all.
* Source for header: http://scienceblogs.com/startswithabang/2012/07/04/how-the-higgs-gives-mass-to-the-universe/
[0] Source: Science Museum London's LHC exhibition on display at the Powerhouse Museum, Sydney, August-October 2016.
[1] Proposed in 1925 by the Austrian physicist Wolfgang Pauli to account for the observed patterns of light emission from atoms. The exclusion principle subsequently has been generalized to include a whole class of particles of which the electron is only one member: http://www.britannica.com/EBchecked/topic/447124/Pauli-exclusion-principle
[2] GeV or gigaelectronvolt is a unit of energy equal to a billion electron volts.
[3] http://www.brighthub.com/science/space/articles/84188.aspx
[4] Having only magnitude, not direction.
[5] “Higgs Boson”: http://www.fnal.gov/pub/inquiring/questions/higgs_boson.html
[6] “What is a Higgs boson?” http://wiki.answers.com/Q/What_is_a_Higgs_boson
The Higgs field is named after one of the physicists who first postulated its existence in 1964 as means of explaining inconsistencies in the Standard Model, specifically, why some of the elementary particles such as quarks and electrons have mass, when they don’t really need it. As we have seen, such a field may also explain how the photon, whose rest mass is zero, and which mediates the electromagnetic force, differs from the W and Z bosons - particles with mass that mediate the weak interaction.
The Higgs field is not a force. It cannot accelerate particles and it doesn't transfer energy. However, it is conjectured that it interacts universally with all particles (except those without mass), thereby endowing them with their mass. We can't see or touch the Higgs field. The only way to know if it's there is to create a disturbance in it, like making a sound in air. This disturbance shows up as a particle - the Higgs boson[0]. Although the Higgs field has not yet been identified experimentally, something consistent with its particle is thought to have been discovered following trillions of high energy collisions between subatomic particles in the Large Hadron Collider (LHC) operated by the European Organisation for Nuclear Research (CERN) on the French-Swiss border.
Bosons are one of two elementary particles that quantum theory says make up the universe. By virtue of their specific characteristic of spin (the angle of a particle’s rotational axis), they permeate space, the best known example being the photon. The other classification of elementary particle is the fermion – quarks and electrons – which are the stuff of which matter is composed. By virtue of what is known as the Pauli exclusion principle, unlike bosons they are precluded from occupying the same space at the same time as other particles[1].
According to the Standard Model of particle physics which currently explains electromagnetism and the strong and weak nuclear forces, all the gauge bosons (particles mediating the interaction of elementary particles) should have zero mass. This is true for photons and gluons which mediate electromagnetism and the strong force. However, the W+, W-, and Z bosons, which mediate the weak force (responsible for nuclear decay), have lots of mass when they don’t really need it. In fact, they weigh in at about 80 and 90 gigaelectronvolts[2] (GeV), almost 100 times more than the proton This requires explanation, and since 1964 the current prevailing hypothesis comes under the umbrella of the so-called Higgs mechanism, which confers mass on other elementary particles by converting some of their energy into mass. The discovery of the gluon in 1979 and the W boson in 1983 were therefore necessary precursors to the identification of the Higgs particle over three decades later.
Like the four fundamental forces, the Higgs can also be visualised as a field, except that it occupies every part of the entire universe all the time and doesn't have a source. Also, just like the four forces, it comes with its own particle, but one which, instead of mediating a force, is thought to mediate mass[3]. The Higgs boson may therefore be described as a massive scalar[4] elementary particle with no intrinsic spin, which is why it is classified as a boson (gauge bosons have integer spin).
When physicists say that a force is mediated by a particle, they mean that the particle in question by its very interaction with other particles transfers information describing telling these other particles what to do. An electron in and of itself doesn't know that it's supposed to act in a certain way as described by electromagnetic theory, but a photon, by interacting with it, “tells it so” and that's what is meant by saying that photons mediate the electromagnetic force. So in a slightly different sense the Higgs boson mediates the Higgs field. Like all other particles, the Higgs gets its mass by interacting with ("swimming in") the Higgs field, and the Higgs field is the theoretical means by which all particles, the Higgs included, acquire their mass. The Higgs particle can be thought of as a dense spot in the Higgs field, which can travel like any other particle. It can be considered as being “like a drop of water in water vapor”[5], so the Higgs’ mass is such that it must interact with itself.
Every particle in the universe "swims" through this Higgs field, thereby acquiring their mass, and different particles interact with the Higgs field with different strengths. Some particles are heavier (have larger mass) than others. Our own bodies are composed of protons, neutrons, quarks and electrons, all of which have different masses, and the Higgs boson may well be the explanation. One commentator uses the analogy of walking through a field in which the air is saturated with pollen. “If you're wearing fleece, the pollen will readily attach itself to your clothes. However, if you're wearing a raincoat, the pollen won't attach itself to you quite as easily. That's how particles interact with the Higgs field. If the particles couple with the Higgs field, they'll acquire mass. If they don't, they won't”[6].
Another analogy, frequently used, is that of a popular celebrity who enters a room containing a throng of people who mill around her making it difficult for her to move through. If she were a particle and the throng the Higgs field, she would be interacting with it. If on the other hand, a nobody poked his nose into the room, no one would take any notice leaving him free to move through the assembled multitude at will. He would be said not to be interacting with the field. Thus, particles with no mass such as the photon don't interact with the Higgs field at all.
* Source for header: http://scienceblogs.com/startswithabang/2012/07/04/how-the-higgs-gives-mass-to-the-universe/
[0] Source: Science Museum London's LHC exhibition on display at the Powerhouse Museum, Sydney, August-October 2016.
[1] Proposed in 1925 by the Austrian physicist Wolfgang Pauli to account for the observed patterns of light emission from atoms. The exclusion principle subsequently has been generalized to include a whole class of particles of which the electron is only one member: http://www.britannica.com/EBchecked/topic/447124/Pauli-exclusion-principle
[2] GeV or gigaelectronvolt is a unit of energy equal to a billion electron volts.
[3] http://www.brighthub.com/science/space/articles/84188.aspx
[4] Having only magnitude, not direction.
[5] “Higgs Boson”: http://www.fnal.gov/pub/inquiring/questions/higgs_boson.html
[6] “What is a Higgs boson?” http://wiki.answers.com/Q/What_is_a_Higgs_boson