Gornji kvark

Gornji kvark
Kompozicija	Elementarna čestica
Statistike	Fermioni
Generacija	Prva
Interakcije	jaka, slaba, elektromagnetna, gravitacija
Simbol	u
Antičestica	Gornji antikvark (u)
Teorije	Mari Gel-Man (1964); Džordž Cvejg (1964)
Otkriven	SLAC (1968)
Masa	2,2+0,5; −0,4 MeV/c2
Raspad u	Stabilan, ili donji kvark + pozitron + elektronski neutrino
Naelektrisanje	+2/3 e
Boja naboja	Da
Spin	1/2
Slabi izospin	LH: +1/2, RH: 0
Slabi hipernaboj	LH: +1/3, RH: +4/3

Standardni model elementarnih čestica, s baždarnim i Higsovim bozonom.

Gornji kvark ili u kvark je jedan od elementarnih čestica od kojih se sastoji materija. Najlakši je od svih kvarkova. Zajedno sa donjim kvarkom čini neutrone (1 gornji kvark i 2 donja kvarka) te protone (2 gornja kvarka i 1 donji kvark) koji su deo atomskih jezgara. Čini prvu porodicu čestica prema standardnom modelu. Ima naboj od +2/3 e i masu između 7000220000000000000♠2,2+0,5
−0,4 MeV/c².^[1] Kao i svi kvarkovi spada u grupu fermiona sa spinom od 1/2. Na njega deluju sva 4 osnovna međudelovanja: gravitaciono, elektromagnetno, slabo i jako. Antičestica gornjem kvarku je gornji antikvark.

Njegovo postojanje (zajedno sa donjim i čudnim kvarkovima) postulirali su 1964. godine Mari Gel-Man i Džordž Cvejg da bi objasnili klasifikacionu šemu Osmostrukog puta hadrona. Gornji kvark je prvi put uočen u eksperimentima u Stanfordskom linearno akceleratorskom centru 1968. godine.

Istorija

Na počecima fizike čestica (prva polovina 20. veka), za hadrone poput protona, neutrona i piona se smatralo da su elementarne čestice. Međutim, kako su otkriveni novi hadroni, kolekcija čestica se uvećala sa od nekoliko čestica ranih 1930-ih i 1940-ih do nekoliko desetina tokom 1950-ih. Odnosi između svake od njih bili su nejasni do 1961. godine, kada su Mari Gel-Man^[2] i Juval Neman^[3] (nezavisno jedan od drugog) predložili šemu klasifikacije hadrona pod nazivom Osmostruki put, ili u tehničkom smislu SU(3) simetrija ukusa.

Ova klasifikaciona šema organizovala je hadrone u izospinske multiplete, mada fizička osnova koja stoji iza toga još uvek nije jasna. Godine 1964. godine, Gel-Man^[4] i Džordž Cvejg^[5]^[6] (nezavisno jedni od drugih) predložili su model kvarka, koji se tada sastojao samo od gornjeg, donjeg i stranog kvarka.^[7] Međutim, mada je model kvarka objašnjavao Osmostruki put, direktni dokazi o postojanju kvarkova nisu pronađeni do 1968. godine u Stanfordskom linearnom akceleratorskom centru.^[8]^[9] Eksperimenti dubokog neelastičnog rasipanja pokazali su da protoni imaju podstrukturu, i da protoni napravljeni od tri temeljnije čestice objašnjavaju podatke (čime potvrđuju model kvarka).^[10]

U početku tri tela opisivana kao kvarkovi, već je korišten Ričard Fejnmanov opis partona,^[11]^[12]^[13] ali vremenom je teorija kvarkova postala prihvaćena (pogledajte Novembarsku revoluciju).^[14]

Masa

Uprkos tome što je izuzetno čest, masa gornjeg kvarka nije jasno utvrđena, već se smatra da verovatno leži između 1,8 i 7000300000000000000♠3,0 MeV/c².^[15] Proračuni QCD rešetke daju precizniju vrednost: 7000200999999999999♠2,01±0,14 MeV/c².^[16]

Kada se nađu u mezonima (čestice od jednog kvarka i jedan antikvark) ili barionima (čestice od tri kvarka), ’fektivna masa’ (ili ’odevena’ masa) kvarkova postaje veća zbog energije vezivanja uzrokovane gluonskim poljem između svakog kvarka (videti ekvivalenciju mase i energije). Gola masa kvarkova je toliko mala da se ne može direktno izračunati, jer se moraju uzeti u obzir relativistički efekti.

Референце

^ ^а ^б M. Tanabashi et al. (Particle Data Group) (2018). „Review of Particle Physics”. Physical Review D. 98 (3): 1—708. Bibcode:2018PhRvD..98c0001T. PMID 10020536. doi:10.1103/PhysRevD.98.030001 .
^ M. Gell-Mann (2000) [1964]. „The Eightfold Way: A theory of strong interaction symmetry”. Ур.: M. Gell-Mann, Y. Ne'eman. The Eightfold Way. Westview Press. стр. 11. ISBN 978-0-7382-0299-0.
Original: M. Gell-Mann (1961). „The Eightfold Way: A theory of strong interaction symmetry”. Synchrotron Laboratory Report CTSL-20. California Institute of Technology.
^ Y. Ne'eman (2000) [1964]. „Derivation of strong interactions from gauge invariance”. Ур.: M. Gell-Mann, Y. Ne'eman. The Eightfold Way. Westview Press. ISBN 978-0-7382-0299-0.
Original Y. Ne'eman (1961). „Derivation of strong interactions from gauge invariance”. Nuclear Physics. 26 (2): 222—229. Bibcode:1961NucPh..26..222N. doi:10.1016/0029-5582(61)90134-1.
^ M. Gell-Mann (1964). „A Schematic Model of Baryons and Mesons”. Physics Letters. 8 (3): 214—215. Bibcode:1964PhL.....8..214G. doi:10.1016/S0031-9163(64)92001-3.
^ G. Zweig (1964). „An SU(3) Model for Strong Interaction Symmetry and its Breaking”. CERN Report No.8181/Th 8419.
^ G. Zweig (1964). „An SU(3) Model for Strong Interaction Symmetry and its Breaking: II”. CERN Report No.8419/Th 8412.
^ B. Carithers, P. Grannis (1995). „Discovery of the Top Quark” (PDF). Beam Line. 25 (3): 4—16. Приступљено 2008-09-23.
^ Bloom, E. D.; Coward, D.; Destaebler, H.; Drees, J.; Miller, G.; Mo, L.; Taylor, R.; Breidenbach, M.; et al. (1969). „High-Energy Inelastic e–p Scattering at 6° and 10°”. Physical Review Letters. 23 (16): 930—934. Bibcode:1969PhRvL..23..930B. doi:10.1103/PhysRevLett.23.930 .
^ M. Breidenbach; Friedman, J.; Kendall, H.; Bloom, E.; Coward, D.; Destaebler, H.; Drees, J.; Mo, L.; Taylor, R.; et al. (1969). „Observed Behavior of Highly Inelastic Electron–Proton Scattering”. Physical Review Letters. 23 (16): 935—939. Bibcode:1969PhRvL..23..935B. OSTI 1444731. doi:10.1103/PhysRevLett.23.935.
^ J. I. Friedman. „The Road to the Nobel Prize”. Hue University. Архивирано из оригинала 2008-12-25. г. Приступљено 2008-09-29.
^ R. P. Feynman (1969). „Very High-Energy Collisions of Hadrons” (PDF). Physical Review Letters. 23 (24): 1415—1417. Bibcode:1969PhRvL..23.1415F. doi:10.1103/PhysRevLett.23.1415.
^ S. Kretzer; Lai, H.; Olness, Fredrick; Tung, W.; et al. (2004). „CTEQ6 Parton Distributions with Heavy Quark Mass Effects”. Physical Review D. 69 (11): 114005. Bibcode:2004PhRvD..69k4005K. S2CID 119379329. arXiv:hep-ph/0307022 . doi:10.1103/PhysRevD.69.114005.
^ D. J. Griffiths (1987). Introduction to Elementary Particles. John Wiley & Sons. стр. 42. ISBN 978-0-471-60386-3.
^ M. E. Peskin, D. V. Schroeder (1995). An introduction to quantum field theory. Addison–Wesley. стр. 556. ISBN 978-0-201-50397-5.
^ J. Beringer (Particle Data Group); et al. (2012). „PDGLive Particle Summary 'Quarks (u, d, s, c, b, t, b', t', Free)'” (PDF). Particle Data Group. Приступљено 2013-02-21.
^ Cho, Adrian (април 2010). „Mass of the Common Quark Finally Nailed Down”. Science Magazine.

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Spoljašnje veze

Quantum Physics Made Relatively Simple

[PDG2018-1] а ^б M. Tanabashi et al. (Particle Data Group) (2018). „Review of Particle Physics”. Physical Review D. 98 (3): 1—708. Bibcode:2018PhRvD..98c0001T. PMID 10020536. doi:10.1103/PhysRevD.98.030001 .

[2] M. Gell-Mann (2000) [1964]. „The Eightfold Way: A theory of strong interaction symmetry”. Ур.: M. Gell-Mann, Y. Ne'eman. The Eightfold Way. Westview Press. стр. 11. ISBN 978-0-7382-0299-0.
Original: M. Gell-Mann (1961). „The Eightfold Way: A theory of strong interaction symmetry”. Synchrotron Laboratory Report CTSL-20. California Institute of Technology.

[3] Y. Ne'eman (2000) [1964]. „Derivation of strong interactions from gauge invariance”. Ур.: M. Gell-Mann, Y. Ne'eman. The Eightfold Way. Westview Press. ISBN 978-0-7382-0299-0.
Original Y. Ne'eman (1961). „Derivation of strong interactions from gauge invariance”. Nuclear Physics. 26 (2): 222—229. Bibcode:1961NucPh..26..222N. doi:10.1016/0029-5582(61)90134-1.

[Gell-Man1964-4] M. Gell-Mann (1964). „A Schematic Model of Baryons and Mesons”. Physics Letters. 8 (3): 214—215. Bibcode:1964PhL.....8..214G. doi:10.1016/S0031-9163(64)92001-3.

[Zweig1964a-5] G. Zweig (1964). „An SU(3) Model for Strong Interaction Symmetry and its Breaking”. CERN Report No.8181/Th 8419.

[Zweig1964b-6] G. Zweig (1964). „An SU(3) Model for Strong Interaction Symmetry and its Breaking: II”. CERN Report No.8419/Th 8412.

[Carithers-7] B. Carithers, P. Grannis (1995). „Discovery of the Top Quark” (PDF). Beam Line. 25 (3): 4—16. Приступљено 2008-09-23.

[Bloom-8] Bloom, E. D.; Coward, D.; Destaebler, H.; Drees, J.; Miller, G.; Mo, L.; Taylor, R.; Breidenbach, M.; et al. (1969). „High-Energy Inelastic e–p Scattering at 6° and 10°”. Physical Review Letters. 23 (16): 930—934. Bibcode:1969PhRvL..23..930B. doi:10.1103/PhysRevLett.23.930 .

[Breidenbach-9] M. Breidenbach; Friedman, J.; Kendall, H.; Bloom, E.; Coward, D.; Destaebler, H.; Drees, J.; Mo, L.; Taylor, R.; et al. (1969). „Observed Behavior of Highly Inelastic Electron–Proton Scattering”. Physical Review Letters. 23 (16): 935—939. Bibcode:1969PhRvL..23..935B. OSTI 1444731. doi:10.1103/PhysRevLett.23.935.

[10] J. I. Friedman. „The Road to the Nobel Prize”. Hue University. Архивирано из оригинала 2008-12-25. г. Приступљено 2008-09-29.

[11] R. P. Feynman (1969). „Very High-Energy Collisions of Hadrons” (PDF). Physical Review Letters. 23 (24): 1415—1417. Bibcode:1969PhRvL..23.1415F. doi:10.1103/PhysRevLett.23.1415.

[12] S. Kretzer; Lai, H.; Olness, Fredrick; Tung, W.; et al. (2004). „CTEQ6 Parton Distributions with Heavy Quark Mass Effects”. Physical Review D. 69 (11): 114005. Bibcode:2004PhRvD..69k4005K. S2CID 119379329. arXiv:hep-ph/0307022 . doi:10.1103/PhysRevD.69.114005.

[Griffiths-13] D. J. Griffiths (1987). Introduction to Elementary Particles. John Wiley & Sons. стр. 42. ISBN 978-0-471-60386-3.

[14] M. E. Peskin, D. V. Schroeder (1995). An introduction to quantum field theory. Addison–Wesley. стр. 556. ISBN 978-0-201-50397-5.

[PDG2012-15] J. Beringer (Particle Data Group); et al. (2012). „PDGLive Particle Summary 'Quarks (u, d, s, c, b, t, b', t', Free)'” (PDF). Particle Data Group. Приступљено 2013-02-21.

[lqcd-16] Cho, Adrian (април 2010). „Mass of the Common Quark Finally Nailed Down”. Science Magazine.

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