chapter 10 - folk.uio.nofolk.uio.no/farido/fys3510/highenergyinteractionsdynamicquarkmodel10.pdf ·...

$: Chapter 10 - folk.uio.nofolk.uio.no/farido/fys3510/HighEnergyInteractionsDynamicQuarkModel10.pdf · ¡ Stage 1 § almost elastic l-q collision § q carries fraction x of proton momentum$
Chapter10

¡ 

¡  Deepinelasticscatteringbetweenleptonsandnucleons§  Confirmquarksaremorethanmathematicalobjects§  Highmomentumtransferfromleptonstohadronconstituents§  QCDpredictssmallcouplingbetweenquarksandgluonsatlarge

momenta§  HighpTprocessescomputablewithperturbationmethods

28/04/16 F. Ould-Saada 3

¡  Reviewofhadron-hadroninteractions§  Largecross-sections§  LowpTprocessesformostcollisions§  Involvementofhadronsaswhole,notonlyconstituents§  NouseofperturbationtheoryforlowpTprocesses§  Variousphenomenologicalmodels

¡  DIS§  Informationaboutstructureofnucleon§  l+Nàl’+X§  Nucleonmadeofpartons

▪  Valencequarks▪  Seaofquarksandantiquarks▪  gluons

¡  DIS§  Highmomentum

transferQ2vsshortdistances

§  40000GeV2(HERA)à10-18m

¡  Stage1§  almostelasticl-qcollision§  qcarriesfractionxofprotonmomentumP§  virtualbosonabsorbedbyquark§  structurefunctionF(x)describesmomentumdistributionofconstituentswithin

proton▪  νNscatteringdependson3SFsrelatedto3helicitystatesofWbosons

▪  eNdependson2SFsrelatedto2helicitystatesofγ

¡  Stage2§  Partonfragmentationintotwojetsofhadrons:

▪  Hadronisation“dresses”nakedquarkstoformfinalstatehadrons▪  1stjetstemsfrompartoninteractingwithlepton–high-ptatlargeangle▪  2ndspectatorjet(ortargetjet)comesfromspectatorpartons–low-ptindirectionofincidentparton

§  FragmentationfunctionD(z,Q2))–probabilitythatagivenhadroncarriesafractionzofinteractingpartonenergy


Proton P0 =M!0

⎛

⎝⎜

⎞

⎠⎟ ; electron P =

E!p⎛

⎝⎜⎞

⎠⎟ ; P ' =

E '!p '⎛

⎝⎜

⎞

⎠⎟

Photon q =ν = E −E '!q = !p− !p '⎛

⎝⎜

⎞

⎠⎟ ; Hadronic system W =

E '0!p '0

⎛

⎝⎜

⎞

⎠⎟

4−momentum transfer t = q2 = P −P '( )2= E −E '( )2

−!p− !p '( )2

= 2me2 − 2EE´+2pp´cosθ ≈ −4EE 'sin2 (θ / 2) = −Q2

high energy and small angles

p´≈ p , sinθ ≈θ ⇒ t = q2 ≈ −p2θ 2

4-momentum transfer to proton

t = q2 = M −E '0( )2−!0− !p '0( )

2= 2M 2 − 2ME '0 = −2MTp

centre of mass energy

s = P +P0( )2= P2 +P2

0 + 2PP0 =me2 +M 2 + 2EM ≈ M 2 + 2EM

condition for elastic scattering

P0 ⋅q =Mν =M (E −E ')

Work out details

¡  Scattering§  Elastic:q2<0à

space-like§  Annihilationprocess:

q2>0àtime-like

Laboratory system

dσdΩ"

#$

%

&'M

=dσdΩ"

#$

%

&'R

1−β 2 sin2 θ2"

#$%

&'

)

*+

,

-. ≈

dσdΩ"

#$

%

&'R

cos2 θ2"

#$%

&'

¡  Elasticscatteringofspin-0point-likeelectron(me,-e)byafixedpoint-likenucleus(M,Ze)àRutherford

¡  ElectronspinthroughDiracequation–noprotonspinàMott§  Backscattering(θ=π)forbidden§  EMconserveshelicityàanisotropyàangular

dependency¡  Recoiloftarget–protonwithfinitemassà

E’/Eterm§  MàinfinityèNSàM

¡  Protonwithspin


dσdΩ"

#$

%

&'NS

=dσdΩ"

#$

%

&'M

1

1+ (2E0 /M )sin2 θ2"

#$%

&'

dσdΩ"

#$

%

&'exp t

=dσdΩ"

#$

%

&' F(!q)2

2¡  Spatialextensionofnucleus

§  àformfactorF

§  àExperimentalcrosssection

dσdΩ"

#$

%

&'=

dσdΩ"

#$

%

&'NS

1+ q2

4M 2 2(1+κ )2() *+tan2 θ2"

#$%

&'+κ 2,

-.

/01

µN = (1+κ )µ0 µ0 = e! / 2M (Dirac point-like)

¡  AtHEàmagneticmomentoftargetinadditiontoelectriccharge

dσdΩ"

#$

%

&'=

dσdΩ"

#$

%

&'NS

1+ q2

2M 2 tan2 θ2"

#$%

&'

(

)*

+

,-

dσdΩ"

#$

%

&'R

=Z 2α 2

4E 20 sin

4 θ2"

#$%

&'

¡  Spatialformfactor§  toremovepointlike

approximation§  describeelectriccharge

spatialdistribution

¡  F(q)isFouriertransformoff(r)–f(r)inmomentumspace

ρ(r) = e f (r) = dqdV ; f (r)dV =1∫ ⇔ ρ(r)dV = e∫

F(!q) ≡ 1Ze

ei!q⋅!x f (r)d3x∫


F1p(0) = F2

p(0) = F2n (0) =1 ; F1

n (0) = 0

dσdΩ"

#$

%

&'=

dσdΩ"

#$

%

&'NS

F1(q2 )+ q2

4M 2 2(F1(q2 )+κF2 (q

2 ))2() *+tan2 θ2"

#$%

&'+κ 2F2

2 (q2 ),-.

/01

¡  FormFactors,ElectricchargedistributionandMagnetisation

¡  Moreconvenient,LinearcombinationsàElectricandMagneticFormFactors(normalised)§  distributionsofelectriccharge

andmagneticdipolemoment

GEp,n (q2 ) = F1

p,n (q2 )− q2

4M 2 κF2p,n (q2 )

GMp,n (q2 ) = F1

p,n (q2 )+κF2p,n (q2 )

GEp(0) =1; GM

p(0) = +2.79; GEn (0) = 0; GM

n (0) = −1.91

dσdΩ"

#$

%

&'Ros

=dσdΩ"

#$

%

&'NS

GE2 +

q2

4M 2 GM2

1+ q2

4M 2

+q2

2M 2 GM2 tan2 θ

2"

#$%

&'

(

)*

+*

,

-*

.*

¡  Rosenbluthformulaforepscattering§  Nointerference

betweenelectricandmagneticformfactors

Read more in book + study slides

¡  Lowq2à

¡  Summary§  epscattering§  FromRutherford

toRosenbluth


¡  Parameterisation:lineardependencyforconstantq2

¡  Parameterisation-Scalinglaw

G(q2 ) = 1

1+q2 (GeV / c)2!" #$

0.71

%

&

''''

(

)

****

2

dσdΩ"

#$

%

&'Ros

/ dσdΩ"

#$

%

&'NS

= A(q2 )+B(q2 ) tan2 θ2"

#$%

&'

¡  ExperimentalproofthatScatteringmediatedbysinglephotonexchange§  Figurenextslide§  MeasurementofprotonandneutronForm

Factors

G(q2 ) =GEp(q2 ) = GM

p(q2 )µp

=GM

n (q2 )µn

GEn (q2 ) = 0

!

"#

$#

¡  Parameterisation-Dipoleformula


¡  Electricandmagneticformfactorsoftheprotonandmagneticformfactoroftheneutron.

f (r)dipole = 3.06 e−4.25r

small momentum transfer →

GEp(q2 ) ≈ f (0) 1− 1

6q2 r2$

%&&

'

()) ; r2 = 0.81 fm

¡  f(r)-FouriertransformofG¡  HE:elasticFFverysmall,inelastic

scatteringmuchmorelikely!

¡  W:invariantmassfinal-statehadrons>M

¡  Q2:squaredenergy-momentumtransfer


2Mν ≡W 2 +Q2 −M 2 ; x ≡ Q2

2MνIS : 2Mν >Q2 ; x <1ES : W 2 =M 2 ; 2Mν =Q2; x =1DIS : Q2 >>M 2 ; ν = E −E ' >>M

Proton P0 =M!0

⎛

⎝⎜

⎞

⎠⎟ ; Photon q =

ν = E −E '!q = !p− !p '⎛

⎝⎜

⎞

⎠⎟

W 2 = P0 + q( )2=M 2 + 2P0 ⋅q+ q

2 =M 2 + 2M ⋅ν −Q2 >M 2

¡  2independentvariables§  Q2, ν OR x,ν

d 2σdQ2dν!

"#

$

%&IS

=4πα 2

Q4E 'Ecos2 θ

2!

"#$

%& W2 (Q

2,ν )+ 2W1(Q2,ν )tan2 θ

2!

"#$

%&

'

()

*

+,

d 2σdQ2dν⎛

⎝⎜

⎞

⎠⎟ES

=4πα 2

Q4E 'Ecos2 θ

2⎛

⎝⎜⎞

⎠⎟ 1+ 2

Q2

4m2 tan2 θ2⎛

⎝⎜⎞

⎠⎟

⎡

⎣⎢

⎤

⎦⎥δ ν −

Q2

2m⎛

⎝⎜

⎞

⎠⎟

¡  Compareelastic(ES)e-parton(m)andinelastic(IS)scatteringe-Proton(M)§  W1,W2:structurefunctions

¡  Comparinge-Pande-pàConditiononstructurefunctions(SFs):


W2 (Q2,ν )→ 1

νδ ν −

Q2

2m⎛

⎝⎜

⎞

⎠⎟ ; W1(Q

2,ν )→ Q2

4m2νδ ν −

Q2

2m⎛

⎝⎜

⎞

⎠⎟

¡  Bjorken,1967§  InDIS,SFsdependondimensionlessvariables§  haveonlyveryweakdependenceonQ2,onνandonnucleonsize,asinEScase

¡  Bjorkenscalinglaw

Q2,ν→∞⇒ x ≡ Q2

2Mν finite

Q2 = 2mν (elastic scattering)

⎫

⎬⎪

⎭⎪⇒ x =m /M

νW2 (x,Q2 ) Q2 ,ν→∞⎯ →⎯⎯⎯ F2 (x) ; MW1(Q

2,ν ) Q2 ,ν→∞⎯ →⎯⎯⎯ F1(x)

§  x:fractionofnucleonmasscarriedbypartoninteractingwithlepton§  èstructurefunctiononlydependsonx,notonQ2andν

¡  SLAC,1968§  Linearaccelerator,3km§  Ee=20GeVonHandDtargets§  MeasureE’andθ

E ',θ ⇒Q2,ν,Wd 2σdΩdE '

= f (W )¡  Data

§  ElasticpeakW=M(removed)§  W~1.2-1.8GeV:excitationofbaryonicresonances(Δ(1230MeV)§  W>1.8GeV:continuumwithnoresonances

¡  AtfixedW–§  CrosssectiondecreasesrapidlywithincreasingQ2(Formfactor–figureslide12)§  InelasticScattering~constantforQ2>1àBjorkenscaling

¡  e-Pinteraction§  ratiobetweenelastic(solid

curve)andinelasticcross-sections(points)andMottcross-section(onapoint-likeandspin-lesstarget)asafunctionQ2

§  ISincreasinglymoreimportantthanES:Q2>1

¡  AtfixedW§  IS~constantforQ2>1§  Bjorkenscaling


¡  AsFouriertransformofasphericallysymmetricpoint-likedistributionisaconstant§  àprotonhasasub-structure

ofpoint-likechargeconstituents▪  Moreinchap14

¡  Atfixedx,structurefunctionsF1,2haveveryweakdependenceonQ2asshownbydataforQ2from2to18GeV2

§  àScalingbehaviour

–  (a) λγ >> dN:thephoton"sees"apoint-likenucleon

–  (b) λγ ~ dN:thecrosssectiondependsonq2throughaformfactor,F(q2/M2

N),correspondingtothechargedensityofthenucleon.Tokeeptheformfactordimensionless,amassscaleisnecessary,takentobethemassofthenucleon,MN.

–  (c) λγ << dN:thephotoninteractsdirectlywithaparton,independentlyontherestofthenucleon.Thecrosssectionbecomessimpler.


dσdΩ"

#$

%

&'=

dσdΩ"

#$

%

&'NS

1+ 2τ tan2 θ2"

#$%

&'

(

)*

+

,- ; τ =

Q2

4m2

d 2σdΩdE'

=dσdΩ"

#$

%

&'NS

W2 (Q2 ,ν )+ 2W1(Q

2 ,ν ) tan2 θ2"

#$%

&'

(

)*

+

,-

.

/

00

1

00

⇒2W1

W2

= 2τ

¡  e-scatteringonspin½particlem=xM

¡  e-Pwithstructure


F1(x,Q2 )=0 ⇒spin = 0

2xF1(x,Q2 ) = F2 (x,Q

2 ) ⇒spin = 12

W1→F1M

; W2 →F2ν

"

#$%

&'⇒

νM

F1F2=Q2

4m2

Q2 = 2mν ⇒ m =Q2

2ν= xM

)

*++

,++

⇒ 2xF1 = F2 Callan-Grossrelation

¡  Infinite(nucleon)momentumreferenceframe:|p|>>M§  Neglectmassesandtransversemomenta§  Nucleonconsistsofpoint-likeparticles,

partons§  4-momentumP0ofnucleondistributed

amongpartons

x = Q2

2Mν→

dxdν

=xν→

ddx

=xνddν

d 2σdQ2dx

=xν

d 2σdQ2dν

=4πα 2

Q4E 'E1xcos2 θ

2"

#$%

&' νW2 (Q

2 ,ν )+ 2νW1(Q2 ,ν ) tan2 θ

2"

#$%

&'

(

)*

+

,-

= 4πα2

Q4E 'E1xcos2 θ

2"

#$%

&' F2 (x)+ 2

νMF1(x) tan

2 θ2"

#$%

&'

(

)*

+

,-

F2 (x) = 2xF1(x)⇒d 2σdQ2dx

=4πα 2

Q4E 'EF2 (x)x

cos2 θ2"

#$%

&' 1+

Q2

4M 2x2tan2 θ

2"

#$%

&'

(

)*

+

,-

¡  ISwith(Q2,ν)resultofESonpartonof4-p=xP0§  4-momentumP0ofnucleondistributed

amongpartons¡  StructureFunctionF2(x)/xisdistribution

functionofpartonsinnucleon

d 2σdQ2dx

=4πα 2

Q4E 'E1xcos2 θ

2!

"#$

%& F2 (x)+ 2xF1(x)

Q2

4M 2x2tan2 θ

2!

"#$

%&

'

()

*

+,Work out details in book

¡  Interpretationofscalingsimplestinareferenceframewheretargetismovingwithveryhighvelocity(InfiniteRF)§  pTandrestmassesofconstituents

(partons)maybeneglected


P = p, !p( ) ; p =!p (M ≈ 0)

xP + q( )2 = x2P2 + 2xP ⋅q+ q2( ) =m2c2 ≈ 0

If x2P2 = x2M 2c2 <<Q2 ⇒ x = − q2

2P ⋅q=

Q2

2Mν

Invariant P.q evaluated in lab

¡  PartonModel(partons=quarks+gluons)§  Targetnucleon=streamofpartonswith4-momentumxP§  x=fractionofnucleon3-momentumcarriedbypartonininfiniteRF§  Ifoneparton(mass:m)scatteredbyphoton(4-momentum:q)

¡  x=fractionofnucleon3-momentumcarriedbypartonininfiniteRF¡  EquivalenttopartonofmassmstationaryinlabSystem,withelasticrelation

¡  x=fractionofnucleonmasscarriedbystruckparton

€

x =Q2

2Mν

Mm

MνQxcMQifmQ ==⇒>>=2

;22

2222 ν

¡  Toidentifyconstituentpartonswithquarks,needtoknowspinandelectriccharge

q+ xP0( )2 = −Q2 + 2xM ⋅ν0

! "## $## + x2M 2 =m2 <<W 2

¡  Parton4-momentumaftertheinteraction

¡  qf(x):quarkdensities/momentumdistributionofquarkofflavourf¡  qf(x)dx:probabilityoffindinginanucleonaquarkofflavourfwithmomentum

fractioninintervalxtox+dx¡  Nucleon=valencequarks(carryobservedquantumnumbers)+seaquarks(q-qbar

pairsfromradiatedgluons)


€

F2(x)= x e f2

f∑ qf (x) + q f (x)[ ]

F2lp (x)= x

19

d p + d p( ) +49

up + u p( ) +19

sp + s p( )#

$ % &

' (

F2ln (x)= x

19

dn + d n( ) +49

un + u n( ) +19

sn + s n( )#

$ % &

' (

€

Isospin symmetry :u↔ d⇒n↔ p

⇒ up (x) = dn (x) ≡ u(x) ; d p (x) = un (x) ≡ d(x) ; sp (x) = sn (x) ≡ s(x)Isoscalar target :N p = Nn

F2lN (x) =

12

F2lp (x) + F2

ln (x)[ ] =518

x q(x) + q (x)[ ]q =u,d∑ +

19

x s(x) + s (x)[ ]

FeN2 (x)x∫ = ef

2

f∑

F2lN (x) = xqf (x)ef

2

f =1,Nq

∑


F2ν p(x)= x q(x)+ q(x)[ ]

q=u,d∑

⇒ F2νN (x) ≤ 18

5F2lN (x)

Data⇒ 185F2lN (x) ≅ F2

νN (x)%

&'(

)*

⇒ Parton Charges:+ 23

and − 13

F2 (x)= x ef2

f∑ qf (x)+ qf (x)"# $%

F2lN (x) = 5

18x q(x)+ q(x)[ ]q=u,d∑

+ 19x s(x)+ s (x)[ ] FeN

2 (x) ≅ 0.14→ x q(x)+ q(x)[ ]0

1∫∫ dx ≅ 18

5⋅0.14 ≅ (0.50± 0.05)

¡  Weakcrosssection(GFinsteadofαQED)§  3structurefunctions

F1,F2,F3,§  F3takesintoaccount

ParityviolationinWI

d 2σdQ2dx

=4πα 2

Q4E 'E1xcos2 θ

2!

"#$

%& F2 (x)+ 2xF1(x)

Q2

4M 2x2tan2 θ

2!

"#$

%&

'

()

*

+,

d 2σ ν ,ν

dxdy=GF2MEν

π1− y− Mxy

2Eν

⎛

⎝⎜

⎞

⎠⎟F2 (x)+ xy

2F1(x)∓ xy 1−y2

⎛

⎝⎜

⎞

⎠⎟F3(x)

⎡

⎣⎢

⎤

⎦⎥

Eν >>M ⇒Mxy2Eν

≈ 0

d 2σ ν ,ν

dxdy=σ 0

2Eν F2 (x)∓ xF3(x)( )(1− y)2 + F2 (x)± xF3(x)( )⎡⎣ ⎤⎦

d 2σdxdy

= A(x)+ (1− y)2 + B(x)

x = Q2

2Mν

y = νE=

Q2

2MxE

y =Eµ

Mx(1− cosθ )

dQ2 = 2MExdyd 2σdxdy

= 2MEx d 2σdxdQ2

σ 0 =GF2F2Mπ

=1.58 ⋅10−38cm2GeV −1

Work out details in book

¡  Purelyleptonicprocesses§  J=0àisotropy§  J=1àangular

dependency

dσdΩ

(νee− ) = GF

2s4π 2

dσdΩ

(νee− )∝ GF

2s4π 2

1+ cosθ2

$

%&

'

()2

−− → evev ee

−− → evev ee

§  Scatteringthrough180oforbidden

§  amplitudewithfactor(1+cosθ)

HE : ECM2 ≈ 2mec

2Eν

⇒σ tot (νee− ) = 1

3σ tot (νee

− )

dσdy

=GF2sπ

dσdy

=GF2sπ

1− y( )2dydΩ

=14π

¡  CompareνeandνN§  J=0àisotropy§  J=1àangular

dependency§  Valenceandseaquarks

innucleon!

d 2σ ν ,ν

dxdy=σ 0

2Eν F2 (x)∓ xF3(x)( )(1− y)2 + F2 (x)± xF3(x)( )"# $%

vµ d→ µ−u J = 0

vµ d → µ+u J = 0

vµ u→ µ−d J =1

vµ u→ µ+d J =1

dσ νe

dy=GF2sπ

dσ νe

dy=GF2sπ

1− y( )2

d 2σ νN

dx dy=2GF

2MEνπ

xq(x)+ xq(x) 1− y( )2"#

$%

d 2σ νN

dx dy=2GF

2MEνπ

xq(x) 1− y( )2 + xq(x)"#

$%

12Fν2 (x)− xF

ν3(x)( ) = 2xq(x)

12Fν2 (x)+ xF

ν3(x)( ) = 2xq(x)

"

#$$

%$$

⇒Fν2 (x) = 2x q(x)+ q(x)( )

xFν3(x) = 2x q(x)− q(x)( )

'($

)$

Work out details in book

(25)

¡  Possibleinteractions§  u,d,ands§  F2dependsonvalenceandsea

quarks§  F3dependsonvalencequarks

only

Fν p2 (x) = 2x d(x)+u(x)( )

xFν p3 (x) = 2x d(x)−u(x)( )

Fν p2 (x) = 2x u(x)+ d (x)( )

xFν p3 (x) = 2x u(x)− d (x)( )

FνN2 (x) = F

νN2 (x) = x u(x)+u(x)+ d(x)+ d (x)+ s(x)+ s (x)( )

xFνN3 (x) = F

νN3 (x) = x u(x)+ d(x)+ s(x)−u(x)− d (x)− s (x)( ) = x uv (x)+ dv (x)( )

§  Isoscalartarget

Fν2 (x) = 2x q(x)+ q(x)( )

xFν3(x) = 2x q(x)− q(x)( )

⎧⎨⎪

⎩⎪

§  MeasurementofF2&F3èextractdistributionfunctions

¡  Numberofvalencequarksinthenucleon:3

nv =xFνN

3 (x)x0

1∫ dx= uv (x)+ dv (x)[ ]

0

1∫ dx ≅ 2.8± 0.5

F2νN (x)

0

1∫ dx ≅ 18

5F2lN (x)dx = 0.49± 0.06

0

1∫

ns = x s(x)+ s (x)[ ] 0

1∫ dx = 9F2

lN −52F2νN (x)

#

$%&

'(0

1∫ dx = 0.05± 0.18

nsea = x u(x)+ d (x)!" #$ 0

1∫ dx = F2

νN + xF3νN (x)!" #$0

1∫ dx = 0.02± 0.03

¡  Seaquarkscarrynoprotonmomentum

¡  Nostrangenessinnucleon

¡  50%ofnucleonmomentumcarriedbynonEWparticles–gluons

¡  IntegralofPDFs¡  Extractionfromcombinationofcrosssections

¡  Inproton,u&dquarkshavelargestprobabilitydensityatlargex§  residualmemoryofx~1/3forvalence

quarks§  reductionduetogluonemission

¡  Gluonsand“sea”anti-quarkshavelargeprobabilityatlowx.§  gluonscarry~50%ofprotonmomentum

¡  Makeuseofexperimentalvaluesofpreviousslidetoestimateratioofcrosssections

σ ∝E

σ (νN )σ (νN )

≈ 2

1σ 0Eν

d 2σ νN

dx dydxdy∫ = xq(x)+ xq(x) 1− y( )2#

$%&∫ dxdy = 0.3+ 0.06 / 3= 0.32

1σ 0Eν

d 2σ νN

dx dydxdy∫ = xq(x) 1− y( )2 + xq(x)#

$%&∫ dxdy = 0.3 / 3+ 0.006 = 0.16

¡  Q2dependenceofStructureFunctions¡  Freequarks¡  Gluonexchange¡  Gluonemission

¡  Scalingisapproximatelycorrectbutnotexact

¡  DeviationsfromscalingduetoQCDcorrectionstoQuarkPartonModel§  Quarkcanradiategluon§  Gluoncansplitintoqqbaror

gg


¡  AnalysisofdatawithQCDcorrectionsàαsandΛ

¡  QCDnicelyexplainsdata

¡  Cross-sectionmeasurementsinppandppbarcollisions§  dataincludehighenergycosmicrayinteractions

¡  Transversemomentum§  Highpt:rapidincreasewiths,lowcrosssections,

perturbativemethods(QCD)

§  Lowpt:ln(s)increase,highcrosssections,non-perturbativemethods(αstoolarge)▪  Phenomenologicalmodelsbasedonmany-bodyQCD

pomeron,apseudo-particlewiththequantumnumbersofthevacuum

¡  Schematicrepresentationofthestatusoftwohadronsbeforecollisionfor§  (a)peripheraland§  (b)centralcollisions.Duetorelativisticeffects,thetwohadronscontractalongthedirectionofmotion.§  (c)Sketchoftheincreasewithenergy

ofthehadronsizeandopacity–protondarker

(relativisticcontractionnotshown)§  Opacity:

¡  Exampleofmeasurementsenteringmodelbuilding

¡  HEnucleus-nucleus(A-A)collisionsstudiedsinceendof1980susingionbeams8O,16S,82Pb§  at15GeV/nucleonatBrookhaven§  at200(158for82Pb)GeV/nucleonattheCERNSPS

¡  ResultsshowthattheA-Acollisioncanbeexplainedasaseriesofhadron–nucleuscollisions(superpositionmodel).§  Onlyfewnucleonsoftheprojectile(ortarget)interactinelastically,producinga

heavynuclearfragment,somelightfragmentsandseveralspectatornucleons.§  About20%ofthesenucleonsreinteractsinsidethetargetnucleus.§  Thehadron–nucleusinteractionisthusconsideredasasuperpositionofhadron-

hadroninteractions.¡  OneofthemostusedmodelsinMonteCarlosimulationsofA-A

interactions:Glaubermodelofmultiplenuclearscattering:§  ahadroncrossinganucleuscanundergomultipleinteractions§  ineachinteraction,hadronsareproducedwhichmayinturninteractwithinthe

samenucleus,givingrisetoaintra-nuclearcascade.¡  A-AinteractionsareimportantinthestudyofcascadesinducedbyHE

cosmicrays(p,Heandheaviernuclei)withnucleiintheupperatmosphere

¡  HEA-Acollisionsusedtosearchforpossiblestateofmatterdenoted-QGP¡  Theveryhightemperaturesanddensitiesachievedinthecollisionsshould,

foraveryshorttime,allowquarksandgluonstoexistinafreestate,i.e.,nolongerconfinedinhadrons,inakindof“soup”orplasma.

¡  Stateofmattermighthaveexistedaround10-6safterBigBang.§  PredictedbyQCD

¡  TheBrookhavenRelativisticHeavyIonCollider(RHIC),2000,devotedtothesestudies§  goldionswhichcollidingat56–130GeV/nucleon.§  RHICmayhaveindicationsforaQGPbehavingmorelikealiquidthanagas.

¡  AtLHC,ALICE(aswellasATLASandCMS)studiesindetail82Pbioninteractionsupto5.5TeV/nucleon.

¡  ThestudyofthepropertiesofQGP§  canhelptounderstandtheoriginofparticles(p,n)§  mayalsohaveimportantimplicationsforourunderstandingofcosmology.

¡  10.9§  ReadtheSlidespresentedatCERNonheavyioncollisionsandALICE

¡  10.10TheLHCandtheSearchfortheHiggs§  Readthissectioninthebook–wealreadydiscussedtheHiggsinthe

previouschapter§  ReadtheSlidespresentedatCERNonATLAS,Higgsandother

searches▪  InparticularitisimportanttoknowhowtheHiggsisproducedine+e-and

hadroncolliders,howitdecaysdependingofitsmassandhowitisdiscovered!

¡  Solveproblems§  10.2,10.3§  10.6,10.7

chapter 10 - folk.uio.nofolk.uio.no/farido/fys3510/highenergyinteractionsdynamicquarkmodel10.pdf ·...

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