In particle physics, an elementary particle or fundamental particle is a particle not known to have substructure; that is, it is not known to be made up of smaller particles. Particle physics is a branch of Physics that studies the elementary constituents of Matter and Radiation, and the interactions between them If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which all other particles are made. The Universe is defined as everything that Physically Exists: the entirety of Space and Time, all forms of Matter, Energy In the Standard Model, the quarks, leptons, and gauge bosons are elementary particles. The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. Leptons are a family of fundamental Subatomic particles comprising the Electron, the Muon, and the Tauon (or tau particle as well as their In Particle physics, gauge bosons are Bosonic particles that act as carriers of the fundamental forces of nature [1][2]

## Overview

All elementary particles are either bosons or fermions (depending on their spin). In Particle physics, bosons are particles which obey Bose-Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein In Particle physics, fermions are particles which obey Fermi-Dirac statistics; they are named after Enrico Fermi. In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin The spin-statistics theorem identifies the resulting quantum statistics that differentiates fermions from bosons. The spin-statistics theorem in Quantum mechanics relates the spin of a particle to the statistics obeyed by that particle Particle statistics refers to the particular description of particles in Statistical mechanics. According to this methodology: particles normally associated with matter are fermions, having half-integer spin; they are divided into twelve flavours. Matter is commonly defined as being anything that has mass and that takes up space. In Particle physics, fermions are particles which obey Fermi-Dirac statistics; they are named after Enrico Fermi. In Mathematics, a half-integer is a Number of the form n + 1/2 where n is an Integer. In Particle physics, flavour or flavor (see spelling differences) is a Quantum number of Elementary particles related to their Particles associated with fundamental forces are bosons, having integer spin. In Physics, a fundamental interaction or fundamental force is a mechanism by which particles interact with each other and which cannot be explained in terms In Particle physics, bosons are particles which obey Bose-Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein The integers (from the Latin integer, literally "untouched" hence "whole" the word entire comes from the same origin but via French [3]

Quarksup, down, charm, strange, top, bottom
Leptonselectron neutrino, electron, muon neutrino, muon, tau neutrino, tau
Gauge bosonsgluon, W and Z bosons, photon
Other bosons — Higgs boson, graviton

## Standard Model

Main article: Standard Model

The Standard Model of particle physics contains 12 flavours of elementary fermions, plus their corresponding antiparticles, as well as elementary bosons that mediate the forces and the still undiscovered Higgs boson. In Particle physics, fermions are particles which obey Fermi-Dirac statistics; they are named after Enrico Fermi. In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. The up quark is a particle described by the Standard Model theory of Physics. The down quark is a first-generation Quark with a charge of -(1/3 e. The charm Quark is a second-generation quark with an electric charge of +(2/3 e. The strange quark is a second- generation Quark with a charge of &minus(1/3 e and a strangeness of &minus1 The top quark is the third- generation up-type Quark with a charge of +(2/3 e. The bottom quark is a third-generation Quark with a charge of − e. Leptons are a family of fundamental Subatomic particles comprising the Electron, the Muon, and the Tauon (or tau particle as well as their Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost The muon (from the letter mu (μ--used to represent it is an Elementary particle with negative Electric charge and a spin of 1/2 Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost The tau lepton (often called the tau, tau particle, or occasionally the tauon; symbol) is a negatively charged Elementary particle with In Particle physics, bosons are particles which obey Bose-Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein In Particle physics, gauge bosons are Bosonic particles that act as carriers of the fundamental forces of nature Gluons ( Glue and the suffix -on) are Elementary particles that cause Quarks to interact and are indirectly responsible for the The W and Z bosons are the Elementary particles that mediate the Weak force. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena The Higgs Boson is a hypothetical massive scalar Elementary particle predicted to exist by the Standard Model of Particle physics In Physics, the graviton is a hypothetical Elementary particle, a Boson to be exact that mediates the force of Gravity in the framework The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles In Particle physics, fermions are particles which obey Fermi-Dirac statistics; they are named after Enrico Fermi. to most kinds of particles, there is an associated antiparticle with the same Mass and opposite Electric charge. In Particle physics, bosons are particles which obey Bose-Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein The Higgs Boson is a hypothetical massive scalar Elementary particle predicted to exist by the Standard Model of Particle physics However, the Standard Model is widely considered to be a provisional theory rather than a truly fundamental one, since it is fundamentally incompatible with Einstein's general relativity. Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 There are likely to be hypothetical elementary particles not described by the Standard Model, such as the graviton, the particle that would carry the gravitational force or the sparticles, supersymmetric partners of the ordinary particles. In Physics, the graviton is a hypothetical Elementary particle, a Boson to be exact that mediates the force of Gravity in the framework Gravitation is a natural Phenomenon by which objects with Mass attract one another " Sparticle " is a merging of the words supersymmetric and particle. In Particle physics, supersymmetry (often abbreviated SUSY) is a Symmetry that relates elementary particles of one spin to another particle that

### Fundamental fermions

Main article: fermion

The 12 fundamental fermionic flavours are divided into three generations of four particles each. In Particle physics, fermions are particles which obey Fermi-Dirac statistics; they are named after Enrico Fermi. In Particle physics, a generation is a division of the Elementary particles Between generations particles differ only by their Mass. Six of the particles are quarks. In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. The remaining six are leptons, three of which are neutrinos, and the remaining three of which have an electric charge of −1: the electron and its two cousins, the muon and the tau lepton. Leptons are a family of fundamental Subatomic particles comprising the Electron, the Muon, and the Tauon (or tau particle as well as their Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost The muon (from the letter mu (μ--used to represent it is an Elementary particle with negative Electric charge and a spin of 1/2 The tau lepton (often called the tau, tau particle, or occasionally the tauon; symbol) is a negatively charged Elementary particle with

 First generationelectron: e−electron-neutrino: νeup quark: udown quark: d Second generationmuon: μ−muon-neutrino: νμcharm quark: cstrange quark: s Third generationtau: τ−tau-neutrino: ντtop quark: tbottom quark: b

#### Antiparticles

Main article: antimatter

There are also 12 fundamental fermionic antiparticles which correspond to these 12 particles. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost The up quark is a particle described by the Standard Model theory of Physics. The down quark is a first-generation Quark with a charge of -(1/3 e. The muon (from the letter mu (μ--used to represent it is an Elementary particle with negative Electric charge and a spin of 1/2 Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost The charm Quark is a second-generation quark with an electric charge of +(2/3 e. The strange quark is a second- generation Quark with a charge of &minus(1/3 e and a strangeness of &minus1 The tau lepton (often called the tau, tau particle, or occasionally the tauon; symbol) is a negatively charged Elementary particle with Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost The top quark is the third- generation up-type Quark with a charge of +(2/3 e. The bottom quark is a third-generation Quark with a charge of − e. In Particle physics and Quantum chemistry, antimatter is the extension of the concept of the Antiparticle to Matter, where antimatter is composed The positron e+ corresponds to the electron and has an electric charge of +1 and so on:

 First generationpositron: e+electron-antineutrino: $\bar{\nu}_e$up antiquark: $\bar{u}$down antiquark: $\bar{d}$ Second generationpositive muon: μ+muon-antineutrino: $\bar{\nu}_\mu$charm antiquark: $\bar{c}$strange antiquark: $\bar{s}$ Third generationpositive tau: τ+tau-antineutrino: $\bar{\nu}_\tau$top antiquark: $\bar{t}$bottom antiquark: $\bar{b}$

#### Quarks

Main article: quark

Quarks and antiquarks have never been detected to be isolated, a fact explained by confinement. The positrons or antielectron is the Antiparticle or the Antimatter counterpart of the Electron. The positrons or antielectron is the Antiparticle or the Antimatter counterpart of the Electron. In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. Color confinement, often called just confinement, is the Physics phenomenon that Color charged particles (such as Quarks cannot be isolated singularly Every quark carries one of three color charges of the strong interaction; antiquarks similarly carry anticolor. In Particle physics, color charge is a property of Quarks and Gluons which are related to their Strong interactions in the context of Quantum In particle physics the strong interaction, or strong force, or color force, holds Quarks and Gluons together to form Protons and Color charged particles interact via gluon exchange in the same way that charged particles interact via photon exchange. Gluons ( Glue and the suffix -on) are Elementary particles that cause Quarks to interact and are indirectly responsible for the In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena However, gluons are themselves color charged, resulting in an amplification of the strong force as color charged particles are separated. Unlike the electromagnetic force which diminishes as charged particles separate, color charged particles feel increasing force. Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of

However, color charged particles may combine to form color neutral composite particles called hadrons. In Physics, a bound state is a composite of two or more building blocks ( particles or bodies) that behaves as a single object In Particle physics, a hadron ( from the ἁδρός hadrós, " stout, thick " ( A quark may pair up to an antiquark: the quark has a color and the antiquark has the corresponding anticolor. The color and anticolor cancel out, forming a color neutral meson. In Particle physics, a meson is a strongly interacting Boson &mdashthat is a Hadron with integer spin. Alternatively, three quarks can exist together, one quark being "red", another "blue", another "green". These three colored quarks together form a color-neutral baryon. Baryons are the family of Subatomic particles with a Baryon number of 1 Symmetrically, three antiquarks with the colors "antired", "antiblue" and "antigreen" can form a color-neutral antibaryon. Baryons are the family of Subatomic particles with a Baryon number of 1

Quarks also carry fractional electric charges, but since they are confined within hadrons whose charges are all integral, fractional charges have never been isolated. Electric charge is a fundamental conserved property of some Subatomic particles which determines their Electromagnetic interaction. Note that quarks have electric charges of either +2/3 or −1/3, whereas antiquarks have corresponding electric charges of either −2/3 or +1/3.

Evidence for the existence of quarks comes from deep inelastic scattering: firing electrons at nuclei to determine the distribution of charge within nucleons (which are baryons). Deep inelastic scattering is the name given to a process used to probe the insides of Hadrons (particularly the Baryons, such as Protons and Neutrons The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom In Physics a nucleon is a collective name for two Baryons the Neutron and the Proton. If the charge is uniform, the electric field around the proton should be uniform and the electron should scatter elastically. In Physics, the space surrounding an Electric charge or in the presence of a time-varying Magnetic field has a property called an electric field (that can Low-energy electrons do scatter in this way, but above a particular energy, the protons deflect some electrons through large angles. The recoiling electron has much less energy and a jet of particles is emitted. A jet is a narrow cone of Hadrons and other particles produced by the Hadronization of a Quark or Gluon in a Particle physics This inelastic scattering suggests that the charge in the proton is not uniform but split among smaller charged particles: quarks.

### Fundamental bosons

Main article: boson

In the Standard Model, vector (spin-1) bosons (gluons, photons, and the W and Z bosons) mediate forces, while the Higgs boson (spin-0) is responsible for particles having intrinsic mass. In Particle physics, bosons are particles which obey Bose-Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin Gluons ( Glue and the suffix -on) are Elementary particles that cause Quarks to interact and are indirectly responsible for the In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena The W and Z bosons are the Elementary particles that mediate the Weak force. The Higgs Boson is a hypothetical massive scalar Elementary particle predicted to exist by the Standard Model of Particle physics Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object

#### Gluons

Main article: gluon

Gluons are the mediators of the strong interaction and carry both colour and anticolour. Gluons ( Glue and the suffix -on) are Elementary particles that cause Quarks to interact and are indirectly responsible for the In particle physics the strong interaction, or strong force, or color force, holds Quarks and Gluons together to form Protons and In Particle physics, color charge is a property of Quarks and Gluons which are related to their Strong interactions in the context of Quantum Although gluons are massless, they are never observed in detectors due to colour confinement; rather, they produce jets of hadrons, similar to single quarks. In experimental and applied Particle physics and Nuclear engineering, a particle detector, also known as a radiation detector, is a device used to Color confinement, often called just confinement, is the Physics phenomenon that Color charged particles (such as Quarks cannot be isolated singularly A jet is a narrow cone of Hadrons and other particles produced by the Hadronization of a Quark or Gluon in a Particle physics In Particle physics, a hadron ( from the ἁδρός hadrós, " stout, thick " ( In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. The first evidence for gluons came from annihilations of electrons and positrons at high energies which sometimes produced three jets — a quark, an antiquark, and a gluon. In Particle physics, a three-jet event is an event with many particles in final state that appear to be clustered in three jets A single jet consists

#### Electroweak bosons

Main article: W and Z bosons

There are three weak gauge bosons: W+, W, and Z0; these mediate the weak interaction. The W and Z bosons are the Elementary particles that mediate the Weak force. The W and Z bosons are the Elementary particles that mediate the Weak force. The weak interaction (often called the weak force or sometimes the weak nuclear force) is one of the four Fundamental interactions of nature The massless photon mediates the electromagnetic interaction. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of

#### Higgs boson

Main article: Higgs boson

Although the weak and electromagnetic forces appear quite different to us at everyday energies, the two forces are theorized to unify as a single electroweak force at high energies. The Higgs Boson is a hypothetical massive scalar Elementary particle predicted to exist by the Standard Model of Particle physics In Particle physics, the electroweak interaction is the unified description of two of the four Fundamental interactions of nature Electromagnetism and the This prediction was clearly confirmed by measurements of cross-sections for high-energy electron-proton scattering at the HERA collider at DESY. HERA ( Hadron-Elektron-Ringanlage, or Hadron-Electron Ring Accelerator was a Particle accelerator at DESY in Hamburg. The DESY ( D eutsches E lektronen Sy nchrotron "German Electron Synchrotron" is the biggest German research center for Particle physics The differences at low energies is a consequence of the high masses of the W and Z bosons, which in turn are a consequence of the Higgs mechanism. The Higgs mechanism is Spontaneous symmetry breaking in a Gauge theory. Through the process of spontaneous symmetry breaking, the Higgs selects a special direction in electroweak space that causes three electroweak particles to become very heavy (the weak bosons) and one to remain massless (the photon). In Physics, spontaneous symmetry breaking occurs when a system that is symmetric with respect to some Symmetry group goes into a Vacuum state Although the Higgs mechanism has become an accepted part of the Standard Model, the Higgs boson itself has not yet been observed in detectors. The Higgs Boson is a hypothetical massive scalar Elementary particle predicted to exist by the Standard Model of Particle physics Indirect evidence for the Higgs boson suggests its mass lies below 200-250 GeV. [4] In this case, the LHC experiments may be able to discover this last missing piece of the Standard Model.

## Beyond the Standard Model

Although all experimental evidence confirms the predictions of the Standard Model, many physicists find this model to be unsatisfactory due to its many undetermined parameters, many fundamental particles, the non-observation of the Higgs boson and other more theoretical considerations such as the hierarchy problem. The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles The Higgs Boson is a hypothetical massive scalar Elementary particle predicted to exist by the Standard Model of Particle physics In Theoretical physics, a hierarchy problem occurs when the fundamental parameters ( couplings or masses of some Lagrangian are vastly different (usually There are many speculative theories beyond the Standard Model which attempt to rectify these deficiencies.

### Grand unification

One extension of the Standard Model attempts to combine the electroweak interaction with the strong interaction into a single 'grand unified theory' (GUT). Grand Unification, grand unified theory, or GUT refers to any of several very similar unified field theories or models in Physics that In Particle physics, the electroweak interaction is the unified description of two of the four Fundamental interactions of nature Electromagnetism and the In particle physics the strong interaction, or strong force, or color force, holds Quarks and Gluons together to form Protons and Such a force would be spontaneously broken into the three forces by a Higgs-like mechanism. In Physics, spontaneous symmetry breaking occurs when a system that is symmetric with respect to some Symmetry group goes into a Vacuum state The Higgs mechanism is Spontaneous symmetry breaking in a Gauge theory. The most dramatic prediction of grand unification is the existence of X and Y bosons, which cause proton decay. In Particle physics, the X and Y bosons are hypothetical Elementary particles analogous to the W and Z bosons, but corresponding to a new type of force In Particle physics, proton decay is a hypothetical form of Radioactive decay in which the Proton decays into lighter Subatomic particles However, the non-observation of proton decay at Super-Kamiokande rules out the simplest GUTs, including SU(5) and SO(10). Super-Kamiokande, or Super-K for short is a neutrino observatory in the city of Hida, Gifu Prefecture, Japan.

### Supersymmetry

Main article: supersymmetry

Supersymmetry extends the Standard Model by adding an additional class of symmetries to the Lagrangian. In Particle physics, supersymmetry (often abbreviated SUSY) is a Symmetry that relates elementary particles of one spin to another particle that The Lagrangian, L of a Dynamical system is a function that summarizes the dynamics of the system These symmetries exchange fermionic particles with bosonic ones. In Particle physics, fermions are particles which obey Fermi-Dirac statistics; they are named after Enrico Fermi. In Particle physics, bosons are particles which obey Bose-Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein Such a symmetry predicts the existence of supersymmetric particles, abbreviated as sparticles, which include the sleptons, squarks, neutralinos and charginos. " Sparticle " is a merging of the words supersymmetric and particle. In Particle physics, a sfermion is any of the class of spin -0 Superpartners of ordinary Fermions appearing in supersymmetric extensions In Particle physics, a sfermion is any of the class of spin -0 Superpartners of ordinary Fermions appearing in supersymmetric extensions In Particle physics, the neutralino is a hypothetical particle part of the doubling of the menagerie of particles predicted by supersymmetric theories The chargino is a hypothetical Supersymmetric particle. It refers to the mass Eigenstates of a charged Superpartner, i Each particle in the Standard Model would have a superpartner whose spin differs by 1/2 from the ordinary particle. In Quantum mechanics, spin is a fundamental property of atomic nuclei, Hadrons and Elementary particles For particles with non-zero spin Due to the breaking of supersymmetry, the sparticles are much heavier than their ordinary counterparts; they are so heavy that existing particle colliders would not be powerful enough to produce them. In Particle physics, supersymmetry breaking is the process to obtain a seemingly non- Supersymmetric physics from a supersymmetric theory which is a necessary step A collider is a type of a Particle accelerator involving directed beams of particles. However, some physicists believe that sparticles will be detected when the Large Hadron Collider at CERN begins running. The European Organization for Nuclear Research (Organisation Européenne pour la Recherche Nucléaire known as CERN

### String theory

Main article: string theory

String Theory is a theory of physics where all "particles" that make up matter and energy are comprised of strings (measuring at the Planck length) that exist in an 11-dimensional (according to M-theory, the leading version) universe. String theory is a still-developing scientific approach to Theoretical physics, whose original building blocks are one-dimensional extended objects called strings In Theoretical physics, M-theory is a new limit of String theory in which 11 dimensions of Spacetime may be identified These strings vibrate at different frequencies which determine mass, electric charge, color charge, and spin. A string can be open (a line) or closed in a loop (a one-dimensional sphere, like a circle). As a string moves through space it sweeps out something called a world sheet. String theory predicts 1- to 10-branes (a 1-brane being a string and a 10-brane being a 10-dimensional object) which prevent tears in the "fabric" of space using the uncertainty principle (e. In Theoretical physics, a membrane, brane, or p -brane is a spatially extended mathematical concept that appears in String theory In Quantum physics, the Heisenberg uncertainty principle states that locating a particle in a small region of space makes the Momentum of the particle uncertain g. the electron orbiting a hydrogen atom has the probability, albeit small, that it could be anywhere else in the universe at any given moment).

String theory posits that our universe is merely a 4-brane, inside which exist the 3 space dimensions and the 1 time dimension that we observe. The remaining 6 theoretical dimensions are either very tiny and curled up (and too small to affect our universe in any way) or simply do not/cannot exist in our universe (because they exist in a grander scheme called the "multiverse" outside our known universe).

One particularly interesting prediction of string theory is the existence of extremely massive counterparts of ordinary particles due to vibrational excitations of the fundamental string. Another important prediction is the existence of a massless spin-2 particle behaving like the graviton. In Physics, the graviton is a hypothetical Elementary particle, a Boson to be exact that mediates the force of Gravity in the framework

### Preon theory

Main article: preon

According to preon theory there are one or more orders of particles more fundamental than those (or most of those) found in the Standard Model. In Particle physics, preons are postulated "point-like" particles conceived to be subcomponents of Quarks and Leptons The word was coined The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles The most fundamental of these are normally called preons, which is derived from "pre-quarks". In essence, preon theory tries to do for the Standard Model what the Standard Model did for the particle zoo that came before it. The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles In Particle physics, the term particle zoo is used colloquially to describe a relatively extensive list of the known elementary particles that almost look like hundreds of species Most models assume that almost everything in the Standard Model can be explained in terms of three to half a dozen more fundamental particles and the rules that govern their interactions. Interest in preons has waned since the simplest models were experimentally ruled out in the 1980s.