hl-1 may 2, 2006kernfysica: quarks, nucleonen en kernen1 outline lecture (hl-1) particle production...

HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 1

Outline lecture (HL-1)Particle Production

Particle production in e+e- collisions•Detection techniques•Lepton pair production•Resonances•Non-resonant hadron production•Gluon emission, jets

Literature: Povh/Rith chapter 9 (particle production) Burcham/Jobes Chapter 2 (exp. techniques)


particle production in e+e- collisionselectromagnetic and weak processesspace time momentum

),(p 11 pE

),(p 22 pE e

e

f

f

ee

ff

EmcEmcs

Eccs

22

2221

for 2 : targetfixed

4)pp( :collider

pointn interactio

aroundcylinder type-shellonion :detectors

22210 :energy LEP max. 2cmEGeVs f

ee

ff

Z0


L3 detector at LEP )210( GeVs


2-jet event in ALEPH detector at LEP


excursion to planned experiments at GSI Darmstadt (D)

detector for 1.5 – 15 GeV/c reactions full solid angle, excellent energy and angle resolution for , K,

pp


Simulated event in “Straw Tube Tracker”

pp

gas discharge in 5 mm strawsfrom Al-mylar foil,26 m walls,20 m sense wires

(ca. 3 kV /cm)


“oldfashioned” scintillator detectors with modern crystals and advanced photodiode readout Flash ADC


from leptons to heavy quarks

production threshold)(in discovery

,,

(2001) /2.2

13

6

109.2

102.2

2

e

e

e

ceVm

es

es

e


lepton threshold production

)(

)(

ee

xXeee

3.55s GeV

sharp increase of production ratio due to pair production

20

2

/865.1))((

/869.1))((

cGeVucDm

cGeVdcDm

2255.3 cmGeVs what is the mass of the ?


e+ e- annihilation cross sectionpointlike (re <10-3 fm) spin=1/2 fermions f, Q2=s=4E2

with Nc colors, charge ezf , CM velocity , mfc2<<E

)sin)1(cos1()(4

)sin)1(cos1(

22222

2

222

2

42

cs

zN

cm2 Q

EezeN

d

d

fc

f

fc

2

22

222

)/(9.86)(

3

4

)cos1()(4

GeVs

nbarnc

s

csd

d

ee

ff

ee


e+ e- annihilation measurement

)()( lepton universality

QED prediction


hadronic states coupling to photon (JP=1-)

e+, + -, e-+ -

e- e+

e+e-

e- e+

e- e+

intermediatehadron state

timelike process spacelike process

interference

02 q02 sq

e+e- scattering

dominant process fore+e- production

interference analysis for + -

spin-parity analysis of resonances


hadron resonances J/ production

Breit-Wigner resonance cross section

4/)12(

)(22

2

msJ

s

c fif

low energy resonances ( , , ):4 150 MeV typical hadronic lifetimes:

scfm 231016/501

interpreted as bound states (JP=1-) qq eeee

hadronsee

ee

J/ resonance: e== 4.8 keV, h = 59 keV (lepton universality) = 69 keV

e

h


non-resonant hadron production

)()( 2 eezNqqee fcff

primary qf looses energy bysecondary formation:hadronisation process (1fm/c)

ff qq

hadron jets

primary production forf flavours, Nc colours:

ff qq

)( ff qqee


evidence for 6 quark flavourshadron production ratio

fn

ffz

ee

hadronseeR

1

23)(

)(

R must increase when passing f threshold


hadron 3-jets: existence of gluonsbesides 2-jets from hadronisation:higher order processes

Sg

gqqee

lungbremsstrah

3-jet rate decreases with s=Q2 because of running of S

)/ln()233(

12)(

222

QnQ

fS


Summary lecture (HL-1)Particle production in e+e- collisions

discovery•lepton universality•photon-hadron coupling•hadron resonances•quark flavours•existence of gluons

Literature: Povh/Rith chapter 9 (particle production) Burcham/Jobes Chapter 2 (exp. techniques)


Outline lecture (HL-1b)Weak Interaction

Particle production in e+e- collisions•Lepton pair production•Resonances•Non-resonant hadron production•Gluon emission, jets

Phenomenology of the weak interaction•Lepton families•Types of weak interaction•Coupling strength of charged current•Quark families•Parity violation

Literature: Povh/Rith chapter 10


Weak Interactionnuclear decayshort-range interactionheavy gauge bosons: m(W) = 80.4 GeV/c2, m(Z0) = 91.2 GeV/c2 P (parity) violation, CP (charge conjugation & parity) violation: lepton number conservationwhy 3 families?why mass hierarchy?CKM quark mixing matrix

)(),( 0000 BBKK


parity violation in nuclear decay

because yield depends onspin orientation of nucleus:key experiment on 60Co(Mme. Wu , 1958)

helicity h changes under P operation:

0

ps

psh


types of weak interactions

ee

W-

2q 1q

W- W

leptonic semi-leptonic non-leptonic charged-current interactions

1q 2q

4q3q

non-leptonic decays of strange hadrons:

u

u d

d

s

d

u

u

W-

n

0udu

u d

d

s

W-

p

-u


coupling strength (weak charge g)W boson couples to weak charge g: transition matrix element:

42

20

422

21cMcMQ

MW

Q

Wfi

ggg

very short-range interaction:

fmfmGeVMeV

cMc

W

32 105.2

80197

point interaction (Fermi Ansatz) strength GF (Fermi constant)

convenient definition: 42

3

2

)(e2

:cM

cG

WF

2g

GF to be determined from decay width:

522 )( cmGFe W-

e e

g

g


universality of weak interaction

decay width and lifetime:

s

s

mm

du

mme

e

eud

e

eee

ude

13

13

5

5

10)031.0956.2.(exp

101.3

)/(55 lifetime

3;

;

)/(;

(if universal)


weak charge universalityweak coupling to quarks from semi-leptonic hadron decays:GF appears 4% smaller GF appears X20 smaller

W-

g g cosC

d

u W-

g g sinC

s

u

Cabibbo’s mixing hypothesis (1963), now in quark picture:

b

t

s

c

d

uW+ W-

mixing of partner flavour eigenstates,Cabibbo angle C for 2 families

s

d

s

d

CC

CC

cossin

sincos

'

'

exp. from semi-leptonic or hadronic decays: sinC 0.22


Change of decay rates by Cabibbo angle

transition ratio 20sin

cos

)(

)(22

22

2

2

C

C

usA

udA

g

g


Cabibbo-Kobayashi-Maskawa (CKM) matrix

generalization to 3 quark families

b

sd

VVV

VVV

VVV

b

sd

tbtstd

cbcscd

ubusud

'

'' W

q

q’

gVqq’

Vqq’ correlated through unitarity: unitary triangle 3 real mixing angles, 1 phase factor (KM phase) = f(123)

KM phase to be determined from CP violation in B-decays (b u)

jkiktcui

ij VV

*

,,


helicity suppressed decay

semi-leptonic weak decay of -

eBR

BR

e

4102.1

1

(phase space 3.5 times larger!)

-

J=0 s = 1/2s = -1/2

h = +1 (?) h = +1 (!)

h = +1 forbidden for lefthanded massless leptons!helicity only lorentzinvariant for massless particles :with mass: lefthanded component 1- 2.6 10-5 for e 0.72 for

why so strong?


Summary lecture (HL-1b)Particle production in e+e- collisions

discovery•lepton universality•photon-hadron coupling•hadron resonances•quark flavours•existence of gluons

Phenomenology of the weak interaction•parity violation• weak charge universality•quark mixing matrix

hl-1 may 2, 2006kernfysica: quarks, nucleonen en kernen1 outline lecture (hl-1) particle production...

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