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