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Matter, Antimatter and CP violation. Aurelio Bay Institut de Physique des Hautes Energies. Séminaire Uni Neuchâtel 27-I-2003. ELECTRON. m. 1. m. 10. -5. QUARKS. The Cosmic Onion. PROTON. NEUTRON. m. -15. 10. }. NOYAU. ATOM. m. 10. -10. m. 10. 7. m. 1. m. 10. 11. - PowerPoint PPT Presentation
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Aurelio BayInstitut de Physiquedes Hautes Energies
Matter, Antimatter and
CP violation
Séminaire Uni Neuchâtel 27-I-2003
The Cosmic Onion
ELECTRON
PROTONNEUTRON
NOYAU
} m
QUARKS
ATOM
m
m m
The cosmic onion 2
.
Universe
m
m
m
m
m
Matter Antimatter and CP violation
The Standard Model of particles (and antiparticles)Symmetries
Parity (P),Charge Conjugation (C) and Time reversal (T)
P and C violationBaryogenesisCP & T violationExperimentsConclusion
The Standard
Model
e
e
u c t
d s bQuarks
Strong : gluons
E.M. : photon
Weak : W+ W Z
INTERACTIONSMATTERCharge [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 L× ()U YQCD - Electro weak Theory
3
do not forgetantiparticles... !
Spin 1/2 Spin 1
Antiparticles
(iγμ∂μ −m)Ψ =0
Paul A. M. Dirac theory of relativisticquantum mechanics in 1927
describes spin 1/2 particle & antiparticle
Oppenheimer, Stückelberg, Feynman suggestto replace E<0 particles with other(anti)particles of opposite charge and E>0
correctly describes spin 1/2 particlebut with a "double" of negative energy...
Positrons observation
Positrons were observed at CAL-Tech byC. D. Anderson in 1932.
B
e e
Pair creation
Symmetries
Amalie (Emmy) Noether
In 1915 she links the invarianceproperties of a Lagrangian toconservation laws
Translation Momentum conserved
Gauge Charge conserved
Invariance under:
Rotation Angular mom. conserved
Symmetries in particle physicsNon-observables symmetry transformations conservation law
/ selection rulesdifference between permutation B.E. / F.D. statis. identical particlesabsolute position r r + p conservedabsolute time t r + E conservedabsolute spatial direction rotation r r' J conservedabsolute velocity Lorentz transf. generators L. groupabsolute right (or left) r r Paritysign of electric charge q q Charge conjugationrelative phase between states with different charge q eiq charge conserved different baryon nbr B eiB B conserved different lepton nbr L eiL L conserveddifference between coherent mixture of (p,n) isospin
€
p
n
⎛
⎝ ⎜
⎞
⎠ ⎟→ U
p
n
⎛
⎝ ⎜
⎞
⎠ ⎟
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
Discrete symmetries P, C,...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
e.m. interactionsare P & C invariant
€
VCoulomb(r r ) ~
qQr r
P : VCoulomb(r r ) a VCoulomb(−
r r ) = VCoulomb(
r r )
C : VCoulomb(r r ) a VCoulomb(
r r )
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 −t
T :r p a −
r p
T :r J a −
r J
Ok with electrodynamics:
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
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.
100% P violation in DNA
Too much symmetry...
LL RR
LR
? Bacchus, Arianna ?
QuickTime™ et un décompresseurCinepak sont requis pour visualiser
cette image.
MUSEE ROMAIN DE NYON
P conserved in e.m. and strong1924 O. Laporte classified the wavefunctions of an atom aseither even or odd, parity or .In e.m. atomic transitions a photon of parity 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.
Parity in weak interactions
6 Fermi, 1949 model of W interactions: P conservation assumed
6 C.F. Powell,... observation of two apparently identical particles "tau" and "theta" weakly decaying tau 3 pions theta 2 pionswhich indicates P(tau) = and P(theta) =If Parity holds "tau" and "theta" cannot be the same particle.
6 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.
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)
Co 601956 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
152 Sm
Eu + e−Z=63A= +Sm +γ6
Polarimeter: selects γ of defined helicity
152Sm γNaI
Counter
Result: neutrinos are only left-handed
Measurement of neutrino helicity
(Goldhaber et al. 1958)
Parity P and neutrino helicity
right
left
P
P symmetry violated at (NLNR)/(NLNR) = 100%
Charge conjugation C
left
C
left
C symmetry violated at 100%
C transforms particles antiparticle
CPLast chance: combine C and P !
gauche ν droit_
P C
left right
Is our UniverseCP symmetric ?
(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
Baryo genesis
I
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 planet. 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
QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.
sensitivity (0.5 - 20 GeV):
He/He ~10
C/C ~10
AMS
Baryo genesis
II
Today (age of Univers 10-20 109 years),
no antimatter around:
the visible Universe contains essentially
protons, electrons and photons.The N of photons is very large compared to p and e :
N ( ) = 412 photons/cm 33
kTch
22
matter =0.1C =1 10-6 GeV/cm3 10-6 p/cm3
Nprotons
Nphotons
This suggests a Big Bang annihilation phasein which matter + antimatter was transformedinto photons...
Baryo genesis
III
N(q)
N(q)≈
3×+
3×
/ , To get the correct baryon photon ratio we need an :asymmetry of the order
annihilationgives photons
Hydrogenplus photons
quarksantiquarkse+ et e−
time
:Scenario ,At a certain point of the history of the Big Bang :we need the following conditions
( )> ( )N quarks N antiquarksand (N e-)> (N e+)
Baryogenesis
IV1) 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
OK : Universe expands.
Starting from a perfectly symmetric Universe: 3 rules to induce asymmetryduring evolution
Andrej Sakarov 1967
B(t=0) = 0 B(today)>0
Baryogenesis V
Prob(Xqq) = Prob(Xqe-) = (1---Prob(Xqq) = Prob(Xqe+) = (1-
Requirement:
q q ouq e+
q q ouq e
X
X
1027°K
... forbidden by CP symmetry !
=
{
Xqq
--- XqqCP
CPmirror
CP violation
K0L
e
e MIRROR CP{
CP symmetry implies identical rates. Instead...
K0L 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 + %
providesan absolutedefinition
of + charge
CP violation experiment
K0SCollimators
≈
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
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 factory in Frascati, ...
NA48 decay channel
The Kaon decay channel of the NA48 experiment at CERN - the latest study to provide a precision measurement of CP violation.
CPTSchwinger-Lüders-Pauli show in the '50 that a theory with
locality,Lorentz invariancespins-statistics
is also CPT invariant.
Consequences:
* Consider particle at rest. Its mass is related to:
€
H0 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,...
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
Electric Dipole Moments
Energy shift for a particle with EDM d in a weak electric field Eis linear in E: E = 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
E D M 2
expt [e cm] SM prediction
proton ( 4 6 ) 103 103 neutron < 0.63 10 ( 95% CL) 103
electron ( 0.07 0.07 ) 106 103
muon ( 3.7 3.4 ) 10103
129-Xe <1027
199-Hg <1028
muon measurement in future "neutrino factories" 10
No signal of T violation "beyond the Standard Model" so far !
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...
production of(4s) (10.58GeV/c2)γ = 0.425(4s) B0 B0
B+ B
BaBar (SLAC) and Belle (KEK)in 2001: observation of CP violation in the B mesonsystem, using "asymmetric collider" B factories.KEKB machine:
8 GeVelectrons
3.5GeV positron
BaBar and Belle
Study of the time dependent asymmetry in decay rates ofB0 and anti-B0
m = mass difference of "mass eigenstates" ~ 0.49 1012 h/s
€
ACP(t) =N(B 0 → J /Ψ KS) − N(B0 → J /Ψ KS)
+(t) = S sin Δm t( )
CP violated S ≠ 0
CP measurements at BelleDifficult: B0 mean life 1.54 10 sΔz cβγΔt ~ 200 m at Belle
(4s)
zz1 z2
z
J/Ks
fCP
B0 and anti-B0 oscillate coherently (QM untangled state).When the first decays, the other is known to be of the oppositeflavour use the other side to infer the flavour, B0 or anti-B0,of the fCP parent
e
D
€
e+ → B0
e− → B 0 ⎧ ⎨ ⎩
region of B0 & B0
coherentevolution
Belle
ACC
Silicon Vertex Detector SVD Impact parameter resolution 55m for p=1GeV/c at normal incidenceCentral Drift Chamber CDC (Pt/Pt)2 = (0.0019 Pt)2 + (0.0030)2 K/ separation : dE/dx in CDC dE/dx =6.9% TOF TOF = 95ps Aerogel Cerenkov ACC Efficiency = ~90%, Fake rate = ~6% 3.5GeV/cγ, e : CsI crystals ECL E/E ~ 1.8% @ E=1GeV e : efficiency > 90% ~0.3% fake for p > 1GeV/cKL and : KLM (RPC) : efficiency > 90% <2% fake at p > 1GeV/c
~ 8 m
€
Ldt =∫ 103 fb
108 B pairs
Belle micro-vertex detector
spatial resolution Blepton + X
z (lepton) ~ 100 m
Belle event
CP is violated in
the B0 system
€
ACP(t) =N(B 0 → J /Ψ KS) − N(B0 → J /Ψ KS)
+(t) = S sin Δm t( )
CP
Origin of CP violationHamiltonian 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 real
CP violation is associated to the existence of phases in thehamiltonian.
Standard Model and CP violationThe transitions quark(i) quark(j)
are described by parameters Vij , introduced by N. Cabibbo for i,j=u, d, s
s
u
W
Vus
In the '60 only u, d, s quarks were known. c was introduced in1970 (Glashow, Iliopoulos, Maiani), discovered in 1974.In 1972 Kobayashi & Maskawa show that, in order to generateCP violation, V must be (at least) a 3x3 matrix
they predict the three quark families of the SM:
(u, d), (c, s), (t, b)
The last quark, t, was observed 25 years later !
... try to get some of the Vij to be complex !
II
III
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 = 3
Down type quarkspinor field
Q = 3 but SM doesnot predict theseparameters...
... and there is another (cosmic) problem...!
CP violation inthe K and B meson decays
can be "explained" by the Standard Model.
CP violation inthe Universe
(baryogenesis)cannot
NBNB
NBNB
_
_ =~ Universe:
NBNB
NBNB
_
_ =~ SM provides:
New source for CP beyond the Standard Model?
New source(s) of CP violation ?
X
q
q
complex couplingconstant
X: Super Symmetric Particles, Multi-Higgs doublets, etc.
Complex coupling CP violation
Search for unexpected effects in CP violation,study rare decays (<106)
in Bu, Bd, Bs, Bc and b-baryons...
14 TeV
At LHC over-constrain the SM parameters
p7 TeV
p7 TeV
LHCb detector
B mesons production rate ~100 times largerthan in B factories high precision in CPand door open to study rare decays
Rate(bb) 105 sec1 !
L = 2 1032 cms
bb=500 b
The experiment
N scientists ~560N Institutions 47Cost ~ 76 MCHF
vertexing
particleidentification
€
B0 → π +π− 27k
B0 → K+π− 115k
Bs0 → Ds
−π + 72k
Bs0 → J ψ φ 130k
1y yield
Underground experimental hall
POINT 8 - UX85 - Headwall
Pillar Pillar
March 2002
(ex DELPHI area)
ConclusionCP & T violation has been observed in the K and B systems.SM parameterizes CP violation but cannot explain its origin.The amount of CP violation in SM cannot describe baryogenesis.
High precision studies of discrete symmetries violationneeded to probe the physics beyond the Standard Modeland to understand the Big Bang.
The domain is under heavy theoretical and experimental attack:K and B factories, EDM measurements, anti-H, neutrinos,double beta, g2, ...
LHC will provide a huge statistics of B's (and other particles) to shed light on this domain of fundamental physics and cosmology,
"curiosity driven".
Bibliography
I.I. Bigi and A. I. Sanda: CP violationCambridge U. Press, 2000
G. C. Branco, L.Lavoura, J.P. Silva: CP violationOxford U. Press, 1999
T. Nakada: CP Violation, status and future prospectXXXth ITEP Winter school of physicswww-iphe.unil.ch IPHE 2002-011