Elementarpartikel

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En elementarpartikel er en partikel der ikke kan deles i mindre bestanddele. Grundet udviklingen i vores forståelse af naturen har betydningen ændret sig gennem historien. I dag omfatter elementarpartikler kvarker/antikvarker, leptoner/antileptoner, samt en række kraftformidlende elementarpartikler (se nedenfor). De tidligere partikler, der tidligere opfattedes som elementarpartikler, kan således opbygges af de ovennævnte elementarpartikler. Ligeledes er det muligt, at ny forskning vil afsløre endnu mindre byggesten end de nuværende elementarpartikler.

Fra den græske oldtid (antikken) havde man en ide om, at alt stof bestod af noget udeleligt, som på græsk kaldes atomos - heraf navnet atom. De blev da, i princippet, klassificeret som elementarpartikler. Den første subatomare partikel der blev opdaget, var elektronen (1897). Protonen og neutronen blev først fundet i 1918, henholdsvis 1932.

Partikelfysikken beskriver i dag elementarpartiklerne og deres vekselvirkninger i en teori der kaldes Standardmodellen. I Standardmodellen består stof af 6 kvarker, 6 antikvarker, 6 leptoner og 6 antileptoner. Disse 24 partikler antages i dag at være stofs fundamentale byggesten. Herudover eksisterer der også en række kraftformidlende elementarpartikler: gravitoner, fotoner, W-bosoner, Z-bosoner, gluoner og Higgs-partikler. Gravitonen og Higgs-partiklen er hypotetiske partikler, da de endnu ikke er eksperimentelt påvist.

Elementarpartikler kan klassificeres i:

• Elementarpartikel
  • Fermioner, stofpartikler (Har spin 1/2, 3/2, 5/2,...).
    • baryoner (kan "føle" den stærke kernekraft).
      • Kvarker: up-kvark, down-kvark, charm-kvark, strange-kvark, top-kvark, bottom-kvark og deres antipartikler.
    • leptoner (kan ikke "føle" den stærke kernekraft).
      • elektron, myon, tauon, elektronneutrino, myonneutrino, tauonneutrino og deres antipartikler.
  • Bosoner, kraftpartikler (Kraftformidlere)
    • Har spin 1, 2,...).
      • gravitoner, fotoner, W-bosoner, Z-bosoner, gluoner, mesoner.
    • Har spin 0.
      • Higgs-partikel.

[redigér] Stofpartikeltabel

Udover tabellens, findes der også 12 antipartikler:

Familie	partikel	Masse·c2	el.lad./|e|	Baryontal	Vekselvirkning
1. Familie	Elektron (e)	511 keV	-1	0	Gr., em., svage
	Elektron-Neutrino (νe)	<2 eV	0	0	Gr., svage
	Up-kvark (u)	4 MeV	2/3	1/3	Gr., em., svage, stærke
	Down-kvark (d)	7 MeV	-1/3	1/3	Gr., em., svage, stærke
2. Familie	Myon (μ)	0,1 GeV	-1	0	Gr., em., svage
	Myon-Neutrino (νμ)	<0,2 MeV	0	0	Gr., svage
	Charm-kvark (c)	1,5 GeV	2/3	1/3	Gr., em., svage, stærke
	Strange-kvark (s)	0,15 GeV	-1/3	1/3	Gr., em., svage, stærke
3. Familie	Tau (τ)	1,8 GeV	-1	0	Gr., em., svage
	Tau-Neutrino (ντ)	<0,02 GeV	0	0	Gr., svage
	Top-kvark (t)	174,0 GeV	2/3	1/3	Gr., em., svage, stærke
	Bottom-kvark (b)	4,7 GeV	-1/3	1/3	Gr., em., svage, stærke

[redigér] Kraftpartikeltabel

(I parentes: Formodede partikler, som endnu ikke er eksperimentielt påvist):

Partikel	Masse·c2	Spin/(h/2π)	el.lad./|e|	formidlet vekselvirkning
Foton	0	1	0	elektromagnetiske kraft
Z0	ca. 91 GeV	1	0	svage
W+	ca. 80 GeV	1	1
W-	ca. 80 GeV	1	-1
Gluon	0	1	0	stærke (Farvekraft)
(Graviton)	0	2	0	Gravitation
(Higgs)	mellem ca. 60 GeV og ca. 540GeV	0	0	-----

[redigér] Se også

• Subatomar partikel
• Stof
• Antistof
• Partikelfysik
• Rumtid
• Kvantemekanik
• Sparticle

[redigér] Eksterne henvisninger

• particleadventure.org: The Standard Model, Unsolved Mysteries. Beyond The Standard Model, What is the World Made of? The Naming of Quarks (God populær fremstilling på engelsk).
• quarkdance.org ("Nuttede" dansende kvarker med musik)
• University of California: Particle Data Group
• particleadventure.org: Particle chart
• 2005-02-17, Sciencedaily: New Measurement Undermines Physicists' Theories For Nature's Hidden 'Particle-force' Collaboration Citat: "...For some reason, which physicists are still puzzling over, the weak force only ever affects left-handed particles...The theories are really a last ditch effort to make do with the fundamentally flawed Standard Model of physics. If these theories keep getting disproved, we're going to have to go on to an entirely new model of the universe's workings..."
• CERNCourier: Season of Higgs and melodrama
• 6 December, 2001, BBCNews: 'God particle may not exist Citat: "...its giant accelerator which should have shown up the presence of the Higgs found absolutely nothing - and this could mean particle physics having to revisit some of its most cherished ideas..."
  • 10 March, 2004, BBC News: 'God particle' may have been seen Citat: "...If correct, Dr Renton's assessment would place the elusive particle's mass at about 115 gigaelectronvolts...However, there is a 9% probability that the signal could be background "noise"..."
• Milo Wolff: The Physical Origin of Electron Spin - using quantum wave particle structure Citat: "...The electron's structure, as well as its spin, had been a mystery. Providing a physical origin of spin for the first time is the purpose of this paper....note that spin, and other properties, are attributes of the underlying quantum space rather than of the individual particle. This is why spin, like charge, has only one value for all particles...This structure settles a century old paradox of whether particles are waves or point-like bits of matter. They are wave structures in space. There is nothing but space. As Clifford speculated 100 years ago, matter is simply, "undulations in the fabric of space". ..."
• Robert Rutkiewicz: Explaining Particle Spin
• Robert Rutkiewicz: Defining Mass Citat: "...The value of mass is not being redefined. But the concept of mass being a fundamental property is reviewed...A new physical law is postulated: All known particles are elements of momentum moving at a velocity c...This extension is based on special relativity and uses SR equation for mass..."
• The Physical Origin of Electron Spin - using quantum wave particle structure Citat: "...note that spin, and other properties, are attributes of the underlying quantum space rather than of the individual particle. This is why spin, like charge, has only one value for all particles...."
• Glimpses of a new paradigm. K.V.K. Nehru Citat: "...Dewey B. Larson introduces the new paradigm that motion is the basic and sole constituent of the physical universe, and space-time is the content—not the container—of the universe...", Dewey B. Larson (1898-1990)
• 8 January 2004, PhysicsWeb: Muons continue to defy Standard Model Citat: "..."The fact that our measurement continues to deviate from theory may be an indication that we are seeing new physics beyond the Standard Model," said Lee Roberts of Boston University..."