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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)
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 2
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
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 3
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 4
L3 detector at LEP )210( GeVs
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 5
2-jet event in ALEPH detector at LEP
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 6
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
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 7
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)
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 8
“oldfashioned” scintillator detectors with modern crystals and advanced photodiode readout Flash ADC
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 9
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
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 10
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 ?
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 11
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
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 12
e+ e- annihilation measurement
)()( lepton universality
QED prediction
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 13
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
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 14
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
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 15
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
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 16
evidence for 6 quark flavourshadron production ratio
fn
ffz
ee
hadronseeR
1
23)(
)(
R must increase when passing f threshold
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 17
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
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 18
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)
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 19
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
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 20
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
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 21
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
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 22
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
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 23
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
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 24
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)
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 25
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
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 26
Change of decay rates by Cabibbo angle
transition ratio 20sin
cos
)(
)(22
22
2
2
C
C
usA
udA
g
g
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 27
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
*
,,
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 28
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?
HL-1 May 2, 2006 Kernfysica: quarks, nucleonen en kernen 29
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
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