summary
DESCRIPTION
Summary. 1. Some history 2. Antiparticles 3. Standard Model of Particles (SM ) Discrete symmetries, CP violation, Connection with Cosmology Fermionic mass generation mechanism, Why do we think that the SM is not the final word ?. The Standard Model. e.m. charge [e]. - PowerPoint PPT PresentationTRANSCRIPT
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A. Bay Beijing October 2005 1
Summary
1. Some history2. Antiparticles3. Standard Model of Particles (SM) Discrete symmetries, CP violation, Connection with Cosmology Fermionic mass generation mechanism, Why do we think that the SM is not the final word ?
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The Standard
Model
e
e
u c t
d s bQuarks
Strong : gluons
E.M. : photon
Weak : W+ W Z
INTERACTIONSMATTERe.m. charge [e]
0
1
2/3
1/3
The SM incorporates:QED: photon exchange between charged particlesWeak (Flavour-Dynamics): exchange of W and Z QCD: gluon exchange between quarks
123SM is based on the gauge group: SU(3)c ×SU(2)L×U(1)YQCD ElecroweakTheory
123
do not forgetantiparticles... !
Spin 1/2 Spin 1
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Discrete symmetries
Parity: left
Charge particle antiparticleconjugation
Temporal inversionright
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symmetry violation
... suddenly we discover that we can observe a "non - observable".
A is discovered.
Some symmetries might have a deep reason to exist ... other not.
The Right-Left symmetry (Parity) was considered an
exact symmetry 1956
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Discrete symmetries P and C
e.m. interactionsare P & C invariant
€
VCoulomb(r r ) ~ qQ
r r
P : VCoulomb(r r ) a VCoulomb(−
r r ) = VCoulomb(
r r )
C : VCoulomb(r r ) a VCoulomb(
r r )
P: (x,y,z) -> (-x,-y,-z).
C: charge -> charge.
€
C :r x a
r x
C : e a −e
C :r A ,V a −
r A ,−V
€
P :r x a −
r x
P :r p a −
r p
P :r J a
r J
angularmomentum,spin.
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What about T ?
If x(t) is solution of F = m d2x/dt2 then x(-t) is also a solution (ex.: billiard balls)
€
T :r E a
r E T :
r B a −
r B
r F = q(
r E +
r v ×
r B ) ⇒ T :
r F a
r F
€
T :r x a
r x
T : t a −tT :
r p a −
r p
T :r J a −
r J
Ok with electrodynamics:
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Parity: (x,y,z) (-x,-y,-z)1848 L. Pasteur discovers the property of optical isomerism.
H3C COOH
H
OHH3C
H
COOH
OH
M
The synthesis of the lactic acid in the lab gives a "racemic" mixture: Nleft molecules = Nright molecules (within statistic fluctuations)
This reflects the fact that e.m. interaction is M (and P) invariant
Mirror symmetry
Asymmetry =
€
N right − N left
N right + N left
= 0
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Parity violation in biology
Humans are mostly right handed:
Asymmetry A = (NRNL)/(NR+NL) ≈ 0.9
“90% Parity violation"
snif snif
Lemmon and orange flavoursare produced by thetwo "enantiomers" of the same molecule.
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100% P violation in DNA
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Too much symmetry...
LL RRLR
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Partial R-L symmetry in Rome
QuickTime™ et un décompresseurCinepak sont requis pour visualisercette image.
MUSEE ROMAIN DE NYON
? Bacchus, Arianna ?
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Some asymmetry introduces more dynamics
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P conserved in e.m. and strong interacctions
1924 O. Laporte classified the wavefunctions of an atom aseither even or odd, parity 1 or 1.In e.m. atomic transitions a photon of parity 1 is emitted.The atomic wavefunction must change to keep the overallsymmetry constant (Eugene Wigner, 1927) : Parity is conserved in e.m. transitions
This is also true for e.m. nuclear or sub-nuclear processes(within uncertainties).
H(strong) and H(e.m.) are considered parity conserving.
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Parity in weak interactions
* E. Fermi, 1949 model of W interactions: P conservation assumed
* C.F. Powell,... observation of two apparently identical particles "tau" and "theta" weakly decaying tau 3 pions theta 2 pionswhich indicates P(tau) = 1 and P(theta) =1If Parity holds "tau" and "theta" cannot be the same particle.
* HEP conf. Rochester 1956 Tsung Dao Lee and Chen Ning Yangsuggest that some particles can appear as parity doublets.Feynman brought up the question of non-conservation of parity(but bets 50 $ that P is conserved). Wigner suggests P is violatedin weak interactions.
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Parity in weak interactions .2
Lee and Yang make a careful study of all known experimentsinvolving weak interactions. They conclude
"Past experiments on the weak interactions hadactually no bearing on the question of parity conservation"
Question of Parity Conservation in Weak InteractionsT. D. Lee Columbia University, New York, New YorkC. N. Yang Brookhaven National Laboratory, Upton, New YorkThe question of parity conservation in beta decays and in hyperon and mesondecays is examined. Possible experiments are suggested which might testparity conservation in these interactions. Phys. Rev. 104, 254–258 (1956)
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Co 60
1956 C. S. Wu et al. execute one of the experiments proposed by Lee and Yang.
Observables:a "vector" : momentum p of beta particlesan "axial-vector" : spin J of nucleus (from B).Compute m = <Jp>
In a P reversed Word: P: Jp a JpP symmetry implies m = 0
Co60 at 0.01 K in a B field.
m was found 0 P is violated
Co
J p
p
J
Co
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152 Sm
Eu + e−Z=63A=152 Sγ62
152
Polarimeter: selects γ of defined helicity
152Sm γNaI
Counter
Result: neutrinos are only left-handed
Measurement of neutrino helicity(Goldhaber et al. 1958)
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Parity P and neutrino helicity
right
left
P
P symmetry violated at (NLNR)/(NLNR) = 100%
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Charge conjugation C
left
C
left
C symmetry violated at 100%
C transforms particles antiparticle
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CPLast chance: combine C and P !
gauche ν droit_
P C
left right
Is our UniverseCP symmetric ?
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(A)symmetry in the Universe
matter
antimatter
Big Bang produced anequal amount of matter and antimatter
Today: we livein a matter dominatedUniverse
time
Big Bang
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Baryo genesis
Big Bang models are matter/antimatter symmetric
Where is ANTIMATTER today?1) Anti-Hydrogen has been produced at CERN: antimatter can exist. 2) Moon is made with matter. Idem for the Sun and all the planets. 3) In cosmics we observe e+ and antiprotons, but
rate is compatible with secondary production.4) No sign of significant of e+e annihilation in
Local Cluster.5) Assuming Big Bang models OK, statistical
fluctuations cannot be invoked to justify observations. No known mechanism to
separate matter and antimatter at very large scale
e+e annihilation in the Galaxy
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QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.
sensitivity (0.5 - 20 GeV):
He/He ~10
C/C ~10
AMS
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Baryogenesis .2 Today (age of Univers 10-20 109 years):
no significant amount of antimatter has been observed.
The visible Universe is maid of
protons, electrons and photonsThe N of photons is very large compared to p and e
rmatter =0.1rC =1 10-6 GeV/cm3 10-6 p/cm3
Nprotons
Nphotons 2511 51
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Baryogenesis .3
N2 122 ( ) = 412 photons/cm 33kT
ch22
This suggests a Big Bang annihilation phasein which matter + antimatter was transformedinto photons...
Sky T observed by COBE~ 2.7K
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Baryogenesis.4
N(q)N(q)
≈3×111
3×11
Toγehecorrecbaryo/hooraio,weeedaasyeryofheorder:
aihilaioγiveshoos
Hydroγelushoos
quarksaiquarkseee−
ie
Sceario:AaceraioiofhehisoryofheBiγBaγ,weeedhefollowiγcodiios:N(quarks)>N(aiquarks)adN(e)>N(e)
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Baryogenesis
.5
1) processes which violate baryonic number conservation:
B violation is unavoidable in GUT.
2) Interactions must violate C and CP.
C violated in Weak Interactions.CP violation observed in K and B decays.
3) System must be out of thermal equilibrium
Universe expands (but was the change fast enough ?)
Starting from a perfectly symmetric Universe: 3 rules to induce asymmetryduring evolution
Andrej Sakarov 1967
B(t=0) = 0 B(today)>0
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Baryogenesis .6
Prob(Xqq) = b Prob(Xqe-) = (1b)---Prob(Xqq) = a Prob(Xqe+) = (1a)-
Requirement: a>b
q q ouq e+
q q ouq e
X
X
1027°K
... forbidden by CP symmetry !
a=b
{
Xqq
--- XqqCP
CPmirror
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CP violation
K0L
e
e MIRROR CP{
CP symmetry implies identical rates. Instead...K0
L is its own antiparticle
K0L
S. Bennet, D. Nygren, H. Saal, J. Steinberg, J. Sunderland (1967):
July 1964: J. H. Christenson, J. W. Cronin, V. L. Fitch et R. Turlay
find a small CP violation with K0 mesons !!!
e Ne N e Ne N + 3%
providesan absolutedefinition
of + charge
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CP violation experiment
K0SCollimators
≈2
Protons
Target
Magnet for neutralparticle selection
Helium
K0L
Magnetic spectrometer
ν
Vacuum
π and electronIDentification
π
e
production and measurement of the decay in
π± , e• and neutrino
K0L
N(e+) − N(e−)N(e+) + N(e−)
δ= S. Bennet et al (1967): (2.37±0.42) 10−3
C. Geweniger et al (1974): (3.41±0.18) 10−3
(Cherenkov)
€
,em
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K0
K0
€
K0 → π +π−
CP b
K 0 → π +π−
Processes should beidentical but CPLearfinds that
neutral kaondecay time distribution
anti-neutral kaon
decay time distribution
CPLear
Other experiments: NA48, KTeV, KLOE f factory in Frascati, ...
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NA48 decay channel
The Kaon decay channel of the NA48 experiment at CERN - the latest study to provide a precision measurement of CP violation.
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CPTSchwinger-Lüders-Pauli show in the '50 that a theory with
locality,Lorentz invariancespins-statistics
is also CPT invariant.
Consequences:
* Consider particle y at rest. Its mass is related to:
€
yH0 ψ = ψ CPT( )+H0 CPT( ) ψ = anti − ψ H0 anti − ψ
particle and antiparticle have same mass (andalso same life time, charge and magnetic moment)
* If a system violates CP T must be violated,...
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0
T from CPLear
€
AT (t) =K 0 → K0( ) − K0 → K 0( )
+(t)
(6.61.6)103
€
pp → K0K−π + K0 → e+π−ν
pp → K 0K+π− K 0 → e−π +ν
€
K0
−K 0 oscillations
s
d
K0 K0
s
dt
t
W W
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Electric Dipole Moments
Energy shift for a particle with EDM d in a weak electric field Eis linear in E: DE = E d . d can be calculated from
d = ri qi
which is left unchanged by T: q a q T: r a r
Consider a neutron at rest.The only vector which characterize the neutron is its spin J.If a non-zero EDM exists in the neutron: d = k JUnder time reversal T: J a JThis implies k = 0 if T is a good symmetry: d = 0
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E D M 2
expt [e cm] SM prediction
proton ( 4 6 ) 1023 1031 neutron < 0.63 1025 ( 95% CL) 1031electron ( 0.07 0.07 ) 1026 103muon ( 3.7 3.4 ) 1011035129-Xe <1027
199-Hg <1028
muon measurement in future "neutrino factories" 102
No signal of T violation "beyond the Standard Model" so far !
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CP & T violation only in K0 system ???
Since 1964, CP and or T violation was searched for in othersystems than K0, other particles decays, EDM...
No other signal until 2001. In 2001 Babar at SLAC and Belleat KEK observe a large CP vioaltion in the B0-B0bar system
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Origin of CP violation
Hamiltonian H = H0 + HCP with HCP responsible for CP violation.Let's take HCP = gH + g*H† where g is some coupling.The second term is required by hermiticity.
If under CP: H H† that is CP H CP† = H† then
CP HCP CP† = CP (gH + g*H†) CP† = gH† + g*H
CP invariance : HCP = CP HCP CP† gH + g*H† = gH† + g*H
The conclusion is that CP is violated if g g* i.e. g non realCP violation is associated to the existence of phases in thehamiltonian.
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IIIII
I
CP violation and SM SM with 3 families canaccommodate CP violation
in the weak interactionsthrough the complex
Cabibbo-Kobayashi-Maskawa quark mixing matrix VCKM,
with 4 parameters.
uct
dsb
Up type quarkspinor field
Q = 2/3
Down type quarkspinor field
Q = 1/3 SM doesnot predict theseparameters...
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In the '60 ...
Parameters Vij are used to calculate the transitions quark(i) quark(j)first introduced by N. Cabibbo for i,j=u, d, s
VCabibbo is real, while CPV implies that some of the Vij complex !
s
uW
Vus
€
Vud Vus
Vcd Vcs
⎛ ⎝ ⎜
⎞ ⎠ ⎟=
cosθ sinθ−sinθ cosθ ⎛ ⎝ ⎜
⎞ ⎠ ⎟≈
0.97 0.220.22 0.97 ⎛ ⎝ ⎜
⎞ ⎠ ⎟VCabibbo=
The quark c was introduced in 1970 (GIM), discovered in 1974.
qcabibbo ~ 12°
In the 1970 the "flavour mixing" matrix was
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CKM matrix
CPV implies that some of the Vij complex.
In 1972 Kobayashi & Maskawa show that,in order to generate CP violation(i.e. to get a complex phase),V must be (at least) 3x3 this is a prediction of the three quark families of the SM: (u, d), (c, s), (t, b)
€
VCKMVCKM† =
1 0 00 1 00 0 1
⎛
⎝ ⎜
⎞
⎠ ⎟
€
Vud Vus Vub
Vcd Vcs Vcb
Vtd Vts Vtb
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
VCKM=In the SM, with 3 and only 3 families of quarks, the matrix must be unitary
The last quark, t, was observed 25 years later !
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CKM matrix in the SM
L = L W,Z + L H + L Fermions + L interaction
L Fermions contains the (Yukawa) mass terms:
€
Hvev
u L c L t L( )MU
uR
cR
tR
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
+ d L s L b L( )MD
dR
sR
bR
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
⎡
⎣
⎢ ⎢ ⎢
⎤
⎦
⎥ ⎥ ⎥
MU and MD complex matrices, diagonalized by a couple ofnon-singular matrices, to get the physical mass values:
€
ALMUAR−1 =
mu
mc
mt
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
€
BLMDBR−1 =
md
ms
mb
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
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CKM matrix .2
€
uR
cR
tR
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟→ AR
−1
uR
cR
t R
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
uL
cL
tL
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟→ AL
−1
uL
cL
tL
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
After the transformation
(idem for D quarks)
e.m. and neutral currents unaffected. The charged currents are modified:
€
Jμch arg ed ∝ d L s L b L( )γμBLA R
−1
uL
cL
tL
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟= d L s L b L( )γμ V
uL
cL
tL
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
"mixing matrix" V unitary
s
uW
Vus
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CKM matrix .3
down strange beauty up 0.97 0.22 0.002charm 0.22 0.97 0.03 top 0.004 0.03 1
€
Vud Vus Vub
Vcd Vcs Vcb
Vtd Vts Vtb
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟≈
1− λ2 /2 λ Aλ3 ρ − iη( )−λ 1− λ2 /2 Aλ2
Aλ3 1− ρ − iη( ) −Aλ2 1
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟+ O(l4)
l= sin(qCabibbo) =0.224A=0.83±0.02
phase: changesign under CP
parametrized by 4 real numbers (not predicted by the SM).Need to measure them.
Magnitude ~
Wolfestein (1983)
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CKM matrix .4
down strange beauty up 0.1% 1% 17%charm 7% 15% 5% top 20% ?% 29%
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Vud Vus Vub
Vcd Vcs Vcb
Vtd Vts Vtb
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
s(Vij)/Vij ~
Today precision from direct measurements, no unitarity imposed:
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CKM matrix .5
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Vud Vus Vub
Vcd Vcs Vcb
Vtd Vts Vtb
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟≈
1− λ2 /2 λ Aλ3 ρ − iη( )−λ 1− λ2 /2 Aλ2
Aλ3 1− ρ − iη( ) −Aλ2 1
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
+ O(l4)
down strange beauty up 0 0 115°charm 0 0 0 top 25° 0 0
Phase ~ down strange beauty
up 0 0 115°charm 0 0 0 top 25° 0 0
Wolfestein (1983)
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€
Vud Vus Vub
Vcd Vcs Vcb
Vtd Vts Vtb
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
CKM Matrix and the Unitary Triangle(s)
SM Unitarity Vji*Vjk=dik VudVub + VcdVcb
+ VtdVtb = 0
V udV ub
Vtd V
tb *
VcdVcb*
*
b(f1)
a(f2)
γ(f3)
The UnitaryThe Unitary TriangleTriangle
Re
Im
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b(f1)
a(f2)
γ(f3)
Re
Imh
1r
CKM Matrix and the Unitary Triangle(s) .2
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Vud Vus Vub
Vcd Vcs Vcb
Vtd Vts Vtb
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟≈
1− λ2 /2 λ Aλ3 ρ − iη( )−λ 1− λ2 /2 Aλ2
Aλ3 1− ρ − iη( ) −Aλ2 1
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟ + O(l4)
SM Unitarity Vji*Vjk=dik VudVub + VcdVcb
+ VtdVtb = 0
The UnitaryThe Unitary TriangleTriangle
afternormalization byVcdVcb*=Al3
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arg(Vtd ) = −β
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arg(Vub) = −γ
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Experimental program: measure sides and angles
* CP violated in the SM => the area of triangle 0* Any inconsistency could be a signal of the existence of phenomena not included in the SM
b
a
γ
~Vub ~Vtd
~Vcb
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Vud Vus Vub
Vcd Vcs Vcb
Vtd Vts Vtb
⎛
⎝
⎜ ⎜ ⎜
⎞
⎠
⎟ ⎟ ⎟
Use B mesonsphenomenology
t quark
oscillations
CP asymmetries
b quark
decays
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Why do we expect some NEW PHYSICS ?* SM has 18 free parameters (more with massive neutrini),in particular masses and CKM parameters are free.* Some of the neutrinos have masses>0* Why the electric charge is quantized ?* The choice of SU(2)U(1) is arbitrary.* Gravitation is absent.
* Problems in Cosmology: What is the nature of dark matter and dark energy ? Baryogenesis does not work in the SM:
The SM amount of CP violation is too lowThe requirement of non-equilibrium cannot be obtainedwith heavy Higgs => new light scalar must exist
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CosmicsCosmics
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masses & mixings
In the SM, CPV is related to the mass generation mechanismfor the fermions. The fermionic system is far from being understood.
Is there any "periodicity" in the mass spectrum?Similar question for the mixing matrices.
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Any horizontal symmetry ?
CPV, mix., baryogenesis: hep-ph/0108216v2 * Neutrino mix and CPV in B: hep-ph/0205111v2Bs-Bs mixing in SO(10) SUSY GUT linked to mix. hep-ph/0312145
A. Buras, J. Ellis, M.K. Gaillard and D.V. Nanopoulos, Nucl. Phys. B135 (1978) 66Lepton-quark mass relations first (?) discussed by
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u c td s b ⎛ ⎝ ⎜
⎞ ⎠ ⎟e μ τν ν ν ⎛ ⎝ ⎜
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SU(3)C ⊗ SU(2)L ⊗U(1)Y ⊗ SU(x)H
V
H
(CKM)(NMS)
?
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Models beyond the SMSM is believed to be a low-energy effective theory of a more fundamental theory at a higher energy scale (compare situation of classical mechanics and relativistic). Grand Unified Theory (GUT) theories have beensuggested to cope with (some of) the SM problems. Theypredicts that the coupling constants meet at EGUT~1015-16 GeV
EW SSB: SU(2)LU(1)YU(1)em
gGUT
you arehere
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SUSY
particle superparticle
The Minimal Supersymmetric extension of the SM (MSSM) with gauge coupling unification at EGUT = 1016 GeV predictsthe EW mixing parameter:sin2qW= 0.2336 ± 0.0017to be compared withthe experiemental valuesin2qW= 0.23120±0.00015.
The model predictsthe existence ofnew particles.
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How to detect New Physics ?Direct searches:
search for new particles, for instance the supersymmetricpartners of particles.
New phenomenologies, indirect effects:ex.1: proton decay
ex.2: EDM measurement ex.3: Hadronic flavour physics very powerful (think to KM prediction of 3 quark families). It can in principle probe veryhigh energies (think to the Z was "seen" in low energy experiments, as an interference effect).Problem: very often complex underlying theory, with large errors.
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Introducing the B mesons family & processes
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B 0 = bd B− = bu B s
0 = bs Bc− = bc + antiparticles
M (B) ≈ M (B0) ≈ ≈ 5279 MeV/c2
lifetime ≈ 1.5 1012 s
mixing/oscillation
b s,d
u,c,t
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B0 B0
d
b
u,c,tW W
b
d
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l
W
b u,c
direct decay
loop decay
B factories
u,c,t
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Where New Physics can show up ?...may modify rates and inject new phases in the processes.For instance:
d
b
W W
b
d
d
b
b
dNew
FCNC
VtsVtb*
B0bd
s
s
d K0
fs
W
t
??????b
d
s
sd K0
fs
c
squark+?
+?
( The MSSM has 43 additional CP violating phases ! )