Particle Physics in a Nutshell Part 1: Going Elementary2. ELEMENTARYPARTICLES
Particlesareballsthatmakeupstuffcalledmatter.Matteris
allaroundyou.Itisyourself,yourbook,yourpencil,oreven
fire.Onethingthatmatterisn’tisenergy,whichisalsostuff
aroundyouexceptitmovesmatter.Withoutenergyallthings
wouldn’texist.Thinkofgrammarforthesetwocommoneveryday
things.Energyistheverbwhilematteristhenoun.
Letmegetthisstraight,matterisNOTtrueenergy.Matter
carriesenergyandgoesthroughreactionstoreleaseenergyout
ofmatteritself,sometimesbytransferenceofenergytoother
formsofenergythroughreactionsandsometimesoftransference
ofmasstoenergyintheE=mc2
equation.Furthermore,itisthe
energymovingthroughmatterinawavenotmattermovingthrough
energy.Thisisanimportantruleforlearningaboutparticle
physics.
Nowbacktoparticles.Youmightknowathingortwoabout
theatomorthemolecule.Theymakeupmatterlikeyourclothing
andstuff.Atomscomefromthegreekwordatomosmeaning
somethingtoosmallbedivided.Atomsthoughcanstillbe
divided.Atomsareparticlesmadeupofotherparticles.
Anotherthingyoumightwanttoknowaboutparticlesis
charge.Forcharge,there’snegative,positiveandneutral.You
canalsoexpresschargeinnumberslike-⅔,like+⅓,orlike0.
Neutralparticlesareprettystablebythemselvesandcanrarely
bedetectedforthistypeofcharge.Positiveandnegativeones
attract.Particlesalsohaveotherdistinctcharacteristicssuch
astheirownspin.Nowletmetellyou,allparticleshavean
eviltwinwithoppositechargecalledantiparticles.Particles
andtheireviltwinbombardandthenKABLOOIE!
Assaidbeforeatomsaremadeupofotherparticles.These
arecalledsubatomicparticles.Theeverydayatomyouseeismade
upofthesesubatomicparticlescalledtheproton,neutron,and
electron.Theseparticlesareevenfurtherdividedinto
categoriescalledelementaryandcompositeparticles.Elementary
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7. ELEMENTARYPARTICLES
Thereare3basicforcesthattheycarry.Theseforcesgive
outlight,holdparticlestogetherandformsabetaradioactive
decay.Theyarethephotons,thegluons,andthewandzbosons.
Thephotonisaparticleyoumightalreadyknowbeing
massless,spin-1,andneutralincharge.Theforceitcarriesis
theelectromagneticforce,aforceinwhichmakeslight.Itis
oneofthe4fundamentalforcesoftheuniverse.Allthereal
gaugebosonscarrythosefundamentalforcesexceptgravity.Well
gravityishypotheticallycarriedbythehypotheticalparticles
ofgravitons.
Anotherforceisthestrongforce.Thestrongforceisthe
strongestforceintheentireuniverseinuncountableamountsof
powertheorizedbyEnricoFermi.Itbindsneutronsandprotons
togethersoitisimportantforfusion.Thecarrierofthisforce
isthegluon.Thegluonhasthesamepropertiesofphotonsexcept
force.Anotherpropertyofthegluonisthatitcombineswith
quarkstoformararestateofmattercalledquark-gluonplasma.
Okay,letustalkaboutanotherforcecalledgravitation
eventhoughitsforcecarrierisonlytheoreticalbutthe
higgs-bosonwasalsooncetheoreticalandnowreal.Right?
Dependentonmassoftheobject(notthebosons),gravitypulls.
Gravitationiscarriedbygravitons.InSeptemberof2015,we,
humans,detectedtwomassiveblackholessuckingthemselves
apart.Theyreleasedwhatareknownasgravitywaves.This
supportsbyahugelotforgravitonsbutdoesn’tcompletelyprove
existencebeingmorelikethreelegsonachairandthegraviton
sittingontop.Thechairmightfallandbeforgotten.Ifthe
chairstands,gravitonswouldbetheonlymasslessspin-2gauge
bosonthatisneutrallycharged.
We’reonthelastforce,theweakforce.Tounderstandthe
weakforceyoumustknowaboutbetadecays.Betadecayisin
whichradiationtransformsneutronsinatomicnucleitoprotons,
positrons,andelectronneutrinos.Positronsarethe
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8. ELEMENTARYPARTICLES
antiparticlesofelectrons.Therearenotonebuttwobosons
namestheWandZbosons.Theyhavemassunlikemostoftheother
gaugebosons.
Withthesebosons,thereisanothertheory.Itiscalledthe
GrandUnifiedTheory.TheGUTstatesthatatthebeginningofthe
universetherewasonceatimewhenthe3forceswerecombined
intoonesingletypeforce.Therewerealso2particlesthatwere
hypothesizedtocarrytheforce,XandYbosons.Ifexisting,
theywouldbothhave1-spinandbegauge.Unliketheother
bosons,theyhavecharge.Xhas+1⅓andYhas+⅓.
Higgs Boson
WhyamIeventalkingabouttheHiggsBoson.Wasn’titsupposed
tobetalkedaboutinthelastchapter?Ifitwas,thenthe
chapterwillbecomesuperlongbecausethehiggsbosonismore
complicatedthantheothers.Forstartersyoumustknowaboutthe
QuantumFieldTheory(QFT)andhowparticlesbehaveinfields.
Fieldsinphysicsarewhatforcescreate.Youmightknowthe
magneticfieldforinstance.Amagnetismadeupofspecialatoms
withconditionsjustrighttodospecialstuffwithphotonsand
attractstuff.Thisstuffstuffisn’tsciencebutinanutshell.
Anyways,asiron,nickel,orcobaltbasedstuffgetscloser,the
attractiongrowsexponentiallyhigherandwithbeingmuchcloser
morephotonstoo.
InQFTparticlesarecalledfieldquanta,thingswithlots
ofenergywheninafield.Inthismagneticfieldforexample
reactingwiththephotonsmakesthingsexcited.Thefieldslike
thatseemnon-constant.Theyhaveseveralupanddownsof
attractionunlikethisfieldthatI’mgoingtotalkabout.
Thishiggsbosonisgeneratedbythehiggsfieldandcarries
thehiggsmechanism,theforceinwhichgeneratesthehiggs
field.Thehiggsfieldisconstantandisascalartypefield.
Scalarisatypeofforcefield.Therearefourbasictypesof
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