Higgs boson

Candidate Higgs boson events from collisions between protons in the LHC. The top event in the CMS experiment shows a decay into two photons (dashed yellow lines and green towers). The lower event in the ATLAS experiment shows a decay into four muons (red tracks).[a]
Composition	Elementary particle
Statistics	Bosonic
Symbol	H0
Theorised	R. Brout, F. Englert, P. Higgs, G. S. Guralnik, C. R. Hagen, and T. W. B. Kibble (1964)
Discovered	Large Hadron Collider (2011–2013)
Mass	125.11±0.11 GeV/c2[1]
Mean lifetime	1.56×10−22 s[b] (predicted) 1.2 ~ 4.6×10−22 s (tentatively measured at 3.2 sigma (1 in 1000) significance)[3][4]
Decays into	Bottom–antibottom pair (observed)[5][6] Two W bosons (observed) Two gluons (predicted) Tau–antitau pair (observed) Two Z bosons (observed) Two photons (observed) Two leptons and a photon (Dalitz decay via virtual photon) (tentatively observed at sigma 3.2 (1 in 1000) significance)[4] Muon–antimuon pair (predicted) Various other decays (predicted)
Electric charge	0 e
Colour charge	0
Spin	0 ħ[7][8]
Weak isospin	−1/2
Weak hypercharge	+1
Parity	+1[7][8]

The Higgs boson, sometimes called the Higgs particle,^[9][10] is an elementary particle in the Standard Model of particle physics produced by the quantum excitation of the Higgs field,^[11][12] one of the fields in particle physics theory.^[12] In the Standard Model, the Higgs particle is a massive scalar boson with zero spin, even (positive) parity, no electric charge, and no colour charge that couples to (interacts with) mass.^[13] It is also very unstable, decaying into other particles almost immediately upon generation.

The Higgs field is a scalar field with two neutral and two electrically charged components that form a complex doublet of the weak isospin SU(2) symmetry. Its "Sombrero potential" leads it to take a nonzero value everywhere (including otherwise empty space), which breaks the weak isospin symmetry of the electroweak interaction and, via the Higgs mechanism, gives a rest mass to all massive elementary particles of the Standard Model, including the Higgs boson itself.

Both the field and the boson are named after physicist Peter Higgs, who in 1964, along with five other scientists in three teams, proposed the Higgs mechanism, a way for some particles to acquire mass. (All fundamental particles known at the time^[c] should be massless at very high energies, but fully explaining how some particles gain mass at lower energies had been extremely difficult.) If these ideas were correct, a particle known as a scalar boson should also exist (with certain properties). This particle was called the Higgs boson and could be used to test whether the Higgs field was the correct explanation.

After a 40-year search, a subatomic particle with the expected properties was discovered in 2012 by the ATLAS and CMS experiments at the Large Hadron Collider (LHC) at CERN near Geneva, Switzerland. The new particle was subsequently confirmed to match the expected properties of a Higgs boson. Physicists from two of the three teams, Peter Higgs and François Englert, were awarded the Nobel Prize in Physics in 2013 for their theoretical predictions. Although Higgs's name has come to be associated with this theory, several researchers between about 1960 and 1972 independently developed different parts of it.

In the media, the Higgs boson has often been called the "God particle" after the 1993 book The God Particle by Nobel Laureate Leon Lederman.^[14] The name has been criticised by physicists,^[15][16] including Higgs.^[17]

Introduction

Standard Model of particle physics
Elementary particles of the Standard Model
Background Particle physics Standard Model Quantum field theory Gauge theory Spontaneous symmetry breaking Higgs mechanism
Constituents Electroweak interaction Quantum chromodynamics CKM matrix Standard Model mathematics
Limitations Strong CP problem Hierarchy problem Neutrino oscillations Physics beyond the Standard Model
Scientists Rutherford Thomson Chadwick Bose Sudarshan Davis Jr Anderson Fermi Dirac Feynman Rubbia Gell-Mann Kendall Taylor Friedman Powell Anderson Glashow Iliopoulos Lederman Maiani Meer Cowan Nambu Chamberlain Cabibbo Schwartz Perl Majorana Weinberg Lee Ward Salam Kobayashi Maskawa Mills Yang Yukawa 't Hooft Veltman Gross Pais Pauli Politzer Reines Schwinger Wilczek Cronin Fitch Vleck Higgs Englert Brout Hagen Guralnik Kibble de Mayolo Lattes Zweig
v t e

Standard Model

Physicists explain the fundamental particles and forces of our universe in terms of the Standard Model – a widely accepted framework based on quantum field theory that predicts almost all known particles and forces aside from gravity with great accuracy. (A separate theory, general relativity, is used for gravity.) In the Standard Model, the particles and forces in nature (aside from gravity) arise from properties of quantum fields known as gauge invariance and symmetries. Forces in the Standard Model are transmitted by particles known as gauge bosons.^[18][19]

Gauge invariant theories and symmetries

"It is only slightly overstating the case to say that physics is the study of symmetry" – Philip Anderson, Nobel Prize Physics^[20]

Gauge invariant theories are theories which have a useful feature; some kinds of changes to the value of certain items do not make any difference to the outcomes or the measurements we make. An example: changing voltages in an electromagnet by +100 volts does not cause any change to the magnetic field it produces. Similarly, measuring the speed of light in vacuum seems to give the identical result, whatever the location in time and space, and whatever the local gravitational field.

In these kinds of theories, the gauge is an item whose value we can change. The fact that some changes leave the results we measure unchanged means it is a gauge invariant theory, and symmetries are the specific kinds of changes to the gauge which have the effect of leaving measurements unchanged. Symmetries of this kind are powerful tools for a deep understanding of the fundamental forces and particles of our physical world. Gauge invariance is therefore an important property within particle physics theory. They are closely connected to conservation laws and are described mathematically using group theory. Quantum field theory and the Standard Model are both gauge invariant theories – meaning they focus on properties of our universe, demonstrating this property of gauge invariance and the symmetries which are involved.

Gauge boson (rest) mass problem

Quantum field theories based on gauge invariance had been used with great success in understanding the electromagnetic and strong forces, but by around 1960, all attempts to create a gauge invariant theory for the weak force (and its combination with the electromagnetic force, known together as the electroweak interaction) had consistently failed. As a result of these failures, gauge theories began to fall into disrepute. The problem was symmetry requirements for these two forces incorrectly predicted the weak force's gauge bosons (W and Z) would have "zero mass" (in the specialized terminology of particle physics, "mass" refers specifically to a particle's rest mass). But experiments showed the W and Z gauge bosons had non-zero (rest) mass.^[21]

Further, many promising solutions seemed to require the existence of extra particles known as Goldstone bosons. But evidence suggested these did not exist either. This meant either gauge invariance was an incorrect approach, or something unknown was giving the weak force's W and Z bosons their mass, and doing it in a way that did not create Goldstone bosons. By the late 1950s and early 1960s, physicists were at a loss as to how to resolve these issues, or how to create a comprehensive theory for particle physics.

Symmetry breaking

In the late 1950s, Yoichiro Nambu recognised that spontaneous symmetry breaking, a process where a symmetric system becomes asymmetric, could occur under certain conditions.^[d] Zdroj:https://en.wikipedia.org?pojem=Higgs_boson
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