Elementary particle

Elementary particles are the smallest well-known components of the subject. Elementary particle without each internal structure (and in this sense absolutely indivisibly) marksone as fundamental particle. There are however also elementary particles with internal structure (it consist of quarks); also these particles are indivisible (in the extended sense), since they cannot be divided into individual quarks (see Confinement). Indivisibility stands therebynot in the contradiction for the decay of these particles into other particles, since it concerns thereby in reality processes of transformation.

After the atomic theory of the Demokrit itself by the development of chemistry in 18. Century confirmed, was considered the atoms as “elementary” particles.Beginning 20. Century discovered one that atoms from an atomic nucleus (consisting of nucleons, thus protons and neutrons) and a covering (consisting of electrons) are developed. The neutron is not a sturdy elementary particle, there it outside of the atomic nucleus radioactively disintegrates. Protons and electrons are considered as stable.

After the discovery of the particles, which develop the atom, - first mainly in the cosmic radiation - a multiplicity of further particles (Myon, pion , became Kaon,…) as well as Antiparticle discovers. The moreover one encountered the quarks a substructure of the nucleons .

In the result followed the development of the standard model elementary particle physics. It contains all particles, which are considered from today's viewpoint as elementary particles.

Table of contents 1 organization of the elementary particles 1,1 organization according to function 1,2 organization according to reciprocal effect 1,3 elementary particles and compound particles 1,4 organization according to spin 1,5 organization - summary 2 acquaintance elementary particle 2,1 leptons and quark 2,2 calibration bosons 2,3 the Higgs boson 2,4 Mesonen (selection) 2,5 baryons (selection) 3 Sources and Web on the left of

organization of the elementary particles

elementary particles have a set of characteristics (mass, different charges, spin), which generally with terms from our everyday life be described cannot, there elementary particles due to their smallObey size of quantum-mechanical regularities. Such characteristics permit an organization of the well-known elementary particles.

organization according to function

three of the basic forces of physics are relevant for the elementary particles:

• The strong reciprocal effect
• the weak reciprocal effect
• the electromagnetic reciprocal effect

these reciprocal effects becomein Quantenfeldtheorien (quantum chromodynamics, Glashow vineyard Salam model of the electricalweak reciprocal effect, quantum electrodynamics) described. One , due to its relatively small strength, can neglect the gravitation in the effect area of the inside of an atom.

Depending upon the reciprocal effect, to which an elementary particle is subject, it one becomesCharge (strong charge (or color charge), weak charge, electrical charge) assigned. The reciprocal effect within each of these three types is obtained calibration bosons so by reciprocal effect-specific exchange particles or messenger particle , mentioned. These, also intermediate bosons mentioned, particle always drawby an integral spin out.

With respect to this sense one differentiates between the actual components of the subject and the elementary particles mediating between these components.

Examples of first are atomic components (proton, neutron, electron). A treatment in more detail follows further down.

The calibration bosons thatthree reciprocal effects are the gluon (strong reciprocal effect), Z and W-bosons (weak reciprocal effect) and the photon (electromagnetic reciprocal effect).

Interestingly enough the gluons themselves carry again a strong charge, so that they are not only carriers of the strong reciprocal effect, but it alsoare subject. The W-bosons of the weak reciprocal effect carry an electrical charge and interact therefore also electromagnetically.

organization according to reciprocal effect

the smallest components of the subject can be divided most simply into two groups: Particles, which are subject to the strong reciprocal effect,and particles, which are not subject to the strong reciprocal effect.

Particles, which are subject to the strong reciprocal effect, are called hadrons. According to the theory of quantum chromodynamics they are compound from elementary quarks, which by the carriers of the strong reciprocal effect, which gluons are held together.

To that extent quarks are the fundamental strongly interacting subject components; they possess the spin ½ and belong thereby to the group of the fermions . Hadrons further divided into Mesonen (to consist of a quark and an antiquark ( the antiparticle of a quark)) and baryons(Consist of three quarks, (and/or. Anti-baryons from in each case three antiquarks)). Only baryons can form atomic nuclei. Well-known baryons are the proton and the neutron.

Particles, which are not subject to the strong reciprocal effect, are called leptons. The theory of the electricalweak reciprocal effecttreats the leptons as elementary particles.

Well-known leptons are the electron, the Myon and the neutrinos. All leptons possess the spin ½ and belong thereby to the group of the fermions.

elementary particles and compound particles

all observedElementary particles are either even fundamentally (therefore without internal structure), or as connection condition of such fundamental particles were understood. One regards today quarks, leptons as well as calibration bosons as fundamental. Quarks and leptons have all a spin of ½; all calibration bosons possess oneSpin of 1 (the hypothetical graviton would have a spin of 2).

Compound particles develop from the combination of three quarks (baryon, spin ½ or 1 ½) or from the combination of a quark with an antiquark (Meson, spin 0or 1). The proton and the neutron are baryons, the pion and the Kaon are Mesonen.

There are however also notes for connections with more than 3 quarks: A stable connection condition of 5 quarks (Pentaquark) became 1997 theoreticallypredicted; 2003 was found first experimental referring to its existence. Since the Pentaquark is however not seen in all experiments, it is not considered at present still as experimentally secured. Likewise 2003 discovered the Japanese bark - experiment a new particle, the discoverybecame shortly thereafter by the American CDF - experiment confirms. Under the name X (3872) led particles after past results as 4-Quark connection condition is interpreted at present (2 quarks and 2 antiquarks). To beginning 2006 still six further became, so far of barkunknown particles discovers, whose theoretical and experimental investigation still persists.

organization according to spin

of systems of elementary particles show different (statistic) behavior, according to whether they possess half or integral spin.

Elementary particles with integral spin (calibration bosons, Mesonen) become asBosons designates. Elementarteilchen mit halbzahligem Spin (Leptonen, Baryonen) werden als Fermionen bezeichnet.

organization - summary

exchange particle		… are bosons
leptons		… are fermions
hadrons	Mesonen	… are bosons
	baryons	… are fermions

the Quantenfeldtheorien describe the reciprocal effectthe fundamental particles (quark, leptons) by exchange particle (photon, gluon, Z-boson, W-boson). Within the Quantenfeldtheorien elementary particles can be converted according to certain rules (preservation of energy, charge, spin) into one another.

acquaintance elementary particle

leptons and quark

family	particle		Mass< math> \ cdot c^2< /math>	Life span	electrical charge	baryon number	of reciprocal effects
					in elementary charges		electrical magnetically	strongly	weakly
1. Family	electron	e	511 keV	stably	−1	0		no
	electron neutrinos	ν e	<3 eV	neutrino oscillation	0	0	no	no
	UP quark	u	1,5 to 4.5 MeV	freely not existence	2/3	1/3
	down quark	D	5 to 8.5 MeV	freely not existence	−1/3	1/3
2. Family	Myon	μ	0.106 GeV	<math> 2 {,} 2 \ cdot 10^ {- 6} s< /math>	−1	0		no
	Myon neutrinos	ν μ	< 0.3 MeV	neutrino oscillation	0	0	no	no
	Charm quark	C	1.0 to 1.4 GeV	freely not existence	2/3	1/3
	strand quark	s	80 to 155 MeV	freely not existence	−1/3	1/3
3. Family	rope	τ	1.777 GeV	<math> 3 \ cdot 10^ {- 13} s< /math>	−1	0		no
	rope neutrinos	ν τ	<30 MeV	neutrino oscillation	0	0	no	no
	Top quark	t	169 to 179 GeV	freely not existence	2/3	1/3
	Bottom quark	b	4.0 to 4.5 GeV	freely not existence	−1/3	1/3

<math> C< /math> thereby the speed of light is in the vacuum.

The quarks specified above occur in in each case three kinds, which differ by the color charge: in each casered, blue and green (the color charge nothing has with the visible color to do). Since quarks never separate freely only in connection with other quarks than Mesonen or baryons arise (see Confinement), are the quark masses only very inaccurately certainly.For top and bottom quark were also the names truth and beauty quark common.

To everyone of the fermions specified above there is an antiparticle, which is generally marked by the placed in front syllable anti. For historical reasons the antiparticle of the electron carries thoseDesignation positron.

calibration bosons

(in parentheses: Particle assumes, not yet found)

particle	mass·C 2	spin	charge	obtained reciprocal effect
photon	0	1	0	electromagnetic Kraft
Z 0	approx. 91 GeV	1	0	weak Kraft
W +	approx. 80GeV	1	1
W −	approx. 80 GeV	1	-1
gluon	0	1	0	strong Kraft (color intensity)
(graviton)	0	2	0	gives

to gravitation altogether 8 gluons, which carry in each case combinations of two color charges, and which reciprocal effect between theseboth color charges mediate. They did not get individual names, in contrast to the 3 bosons, which obtain the weak reciprocal effect: W ⁺, W ⁻ and the neutral Z-boson. The electromagnetic reciprocal effect is arranged for the photon by only 1 boson ,.

the Higgs boson

the Higgs boson is so far a not proven, hypothetical elementary particle. It is forecast due to theoretical considerations by the standard model of elementary particle physics. In order to be consistent with past experimental data, one expects a mass of approximately110 to 250 GeV. The Higgs boson (or Verallgemeinerungen of the same in extended theories) is a necessary component today accepted theories, since by the reciprocal effect with the Higgs boson the mass (in the theory originally massless) of the leptons and quarks is only generated.

Mesonen (selection)

Mesonen are connection conditions from quark and antiquark, and are therefore no fundamental particles.

Particle		quark	mass·C ²	middle life span	charge	Strangeness	antiparticle
of positive pion	π +	u D	139 MeV	2,6·10 −8 s	+ 1	0	Negative pion
of negative pion	π −	u D			− 1	0	of positive pion
neutral pion	π 0	u u +d D	135 MeV	8,3·10 −17 s	0	0
of positive Kaon	K +	u s	494 MeV	1,2·10 −8 s	+ 1	+ 1	negative Kaon
of negative Kaon	K −	u s			− 1	− 1	positive Kaon
neutral Kaon	K 0	D s	498 MeV	5,2·10 −8 s and 8,9·10 −11 s	0	+ 1	anti- Kaon
anti- Kaon	K 0	D s			0	− 1	neutral Kaon
Jot psi	J/Ψ	C C	3097 MeV	0,8·10 −20 s	0	0
Upsilon	Y	b b	9460 MeV	1,3·10 −20 s	0	0

in the column quarks are re-painted over antiquarks and represented red. Ingeneral can occur quantum-mechanical overlays of different quark combinations, like for example with the neutral pion or Kaon. With the latter the experimentally observable conditions are not Kaon and Antikaon, but the overlays <math> K_L< /math> and <math> K_S< /math>, which differ in their life span strongly.

Neutral pion, Jot psi and Upsilon are in each case their own antiparticle.

baryons (selection)

baryons are connection conditions from three quarks (similar to anti-baryons from three antiquarks), and are therefore no fundamental particles.

Particle		quark	mass·C ²	middle life span	spin	charge	Strangeness	Charm
proton	p	uud	938.3 MeV	stably or > 10 32 years	½	+ 1	0	0
neutron	n	udd	939.6 MeV	887 s (as free neutron)	½	0	0	0
Lambda	Λ	uds	1116 MeV	2,6·10 −10 s	½	0	− 1	0
delta plus pluses	Δ ++	uuu	1232 MeV	6·10 −24 s	1 ½	+ 2	0	0
delta pluses	Δ +	uud	1232 MeV	6·10 −24 s	1 ½	+ 1	0	0
delta zero	Δ 0	udd	1232 MeV	6·10 −24 s	1 ½	0	0	0
delta minus	Δ −	ddd	1232 MeV	6·10 −24 s	1 ½	− 1	0	0
sigma pluses	Σ +	uus	1189 MeV	0,8·10 −10 s	½	+ 1	− 1	0
sigma zero	Σ 0	uds	1192 MeV	5,8·10 −20 s	½	0	− 1	0
sigma minus	Σ −	dds	1197 MeV	1,5·10 −10 s	½	− 1	− 1	0
Xi-zero	Ξ 0	uss	1315 MeV	2,9·10 −10 s	½	0	− 2	0
Xi-minus	Ξ −	dss	1321 MeV	1,6·10 −10 s	½	− 1	− 2	0
omega minus	Ω −	sss	1671 MeV	0,9·10 −10 s	1 ½	− 1	− 3	0
Lambda C pluses	Λ C +	udc	2282 MeV	2,3·10 −13 s	½	+ 1	0	+ 1

sources and Web on the left of

• data source to leptons and quark, calibration bosons:
  • Masses to a large extent from http://www.teilchenphysik.org/temp_tpthemen_elementart.htm

• data sources to Mesonen, baryons:
  • Small encyclopedia physics, Leipzig, 1986, ISBN 3-323-00011-0
  • dtv Atlas to physics2, Munich, 1988, ISBN 3-423-03227-8
  • Harald Fritzsch: Quark, Munich, 2001, ISBN 3-492-21655-2
  • KworkQuark - DESYs particle-physics-on-line

• English-language data sources:
  • Particle DATA Group

• further one Web on the left of:
  • Bases of particle physics
  • German particle physics Outreach and info. sides
  • Austrian particle physics Outreach sides ( the Austrian physical society)
  • Victory mouth Brandt: On the search for the smallest things
  • nuclear research center CERN