Aurelio Bay Institut de Physique des Hautes Energies Matter, Antimatter and CP violation Séminaire Uni Neuchâtel 27-I-2003

The Cosmic Onion ELECTRON PROTON NEUTRON 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 violation Baryogenesis CP & T violation Experiments Conclusion

The Standard Model e   e      u c t d s b Quarks Strong : gluons E.M. : photon Weak : W + W  Z INTERACTIONSMATTER Charge [e] 0  1 2/3  1/3 The SM incorporates: QED: photon exchange between charged particles Weak (Flavour-Dynamics): exchange of W  and Z QCD: gluon exchange between quarks do not forget antiparticles... ! Spin 1/2 Spin 1

Antiparticles Paul A. M. Dirac theory of relativistic quantum mechanics in 1927  describes spin 1/2 particle & antiparticle Oppenheimer, Stückelberg, Feynman suggest to replace E<0 particles with other (anti)particles of opposite charge and E>0 correctly describes spin 1/2 particle but with a "double" of negative energy...

Positrons observation Positrons were observed at CAL-Tech by C. D. Anderson in B e  e  Pair creation

Symmetries

Amalie (Emmy) Noether In 1915 she links the invariance properties of a L agrangian to conservation laws Translation Momentum conserved Gauge Charge conserved Invariance under: RotationAngular mom. conserved

Symmetries in particle physics Non-observablessymmetry transformationsconservation law / selection rules difference between permutationB.E. / F.D. statis. identical particles absolute position r  r +  p conserved absolute time t  r +  E conserved absolute spatial directionrotation r  r' J conserved absolute velocityLorentz transf. generators L. group absolute right (or left)r   r Parity sign of electric chargeq   qCharge conjugation relative phase between states with different charge q   e iq   charge conserved different baryon nbr B   e iB   B conserved different lepton nbr L   e iL   L conserved difference between coherent mixture of (p,n)isospin

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. e.m. interactions are P & C invariant

What about T ? If x(t) is solution of F = m d 2 x/dt 2 then x(-t) is also a solution (ex.: billiard balls) Ok with electrodynamics:

Parity: (x,y,z)  (-x,-y,-z) 1848 L. Pasteur discovers the property of optical isomerism. The synthesis of the lactic acid in the lab gives a "racemic" mixture: N left molecules = N right molecules (within statistic fluctuations) This reflects the fact that e.m. interaction is M (and P) invariant Mirror symmetry Asymmetry =

Parity violation in biology Humans are mostly right handed: Asymmetry  A = (N R  N L )/(N R +N L ) ≈ 0.9  “90% Parity violation" snif Lemmon and orange flavours are produced by the two "enantiomers" of the same molecule.

100% P violation in DNA

Too much symmetry... LLRR LR

? Bacchus, Arianna ? MUSEE ROMAIN DE NYON

P conserved in e.m. and strong 1924 O. Laporte classified the wavefunctions of an atom as either even or odd, parity  or . In e.m. atomic transitions a photon of parity  is emitted. The atomic wavefunction must change to keep the overall symmetry 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 pions which 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 Yang suggest 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 violated in weak interactions.

Parity in weak interactions.2 Lee and Yang make a careful study of all known experiments involving weak interactions. They conclude "Past experiments on the weak interactions had actually no bearing on the question of parity conservation" Question of Parity Conservation in Weak Interactions T. D. Lee Columbia University, New York, New York C. N. Yang Brookhaven National Laboratory, Upton, New York The question of parity conservation in beta decays and in hyperon and meson decays is examined. Possible experiments are suggested which might test parity conservation in these interactions. Phys. Rev. 104, 254–258 (1956)

Co C. S. Wu et al. execute one of the experiments proposed by Lee and Yang. Observables: a "vector" : momentum p of beta particles an "axial-vector" : spin J of nucleus (from B). Compute m = In a P reversed Word: P: Jp   Jp P symmetry implies m = 0 Co60 at 0.01 K in a B field. m was found  0  P is violated Co Jp p J

152 Sm Polarimeter: selects  of defined helicity 152 Sm  NaI 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 (N L  N R )/(N L  N R ) = 100%

Charge conjugation C left C left  C symmetry violated at 100% C transforms particles  antiparticle

CP Last chance: combine C and P ! left right Is our Universe CP symmetric ?

(A)symmetry in the Universe matter antimatter Big Bang produced an equal amount of matter and antimatter Today: we live in a matter dominated Universe 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 in the Univers ! e + e  annihilation in the Galaxy

sensitivity ( GeV): He/He ~10  C/C ~10  AMS

Baryo genesis II Today (age of Univers 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 3 3 kT cc 2  2  matter =0.1  C = GeV/cm 3  p/cm 3 N protons N photons      This suggests a Big Bang annihilation phase in which matter + antimatter was transformed into photons...

Baryo genesis III

Baryo genesis IV 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 OK : Universe expands. Starting from a perfectly symmetric Universe: 3 rules to induce asymmetry during evolution Andrej Sakarov 1967 B(t=0) = 0 B(today)>0

Baryogenesis V Prob(X  qq) =  Prob(X  qe - ) = (1  Prob(X  qq) =  Prob(X  qe + ) = (1  - Requirement:  q ou q e + q ou q e  X X °K... forbidden by CP symmetry !  { X  qq X  qq CP mirror

CP violation K 0 L    e      e   MIRROR CP { CP symmetry implies identical rates. Instead... K 0 L is its own antiparticle K 0 L 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 K 0 mesons !!!    e   N    e   N     e   N    e   N +    % provides an absolute definition of + charge

CP violation experiment

K0K0 K0K0 Processes should be identical but CPLear finds that neutral kaon decay 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.

CPT Schwinger-Lüders-Pauli show in the '50 that a theory with locality, Lorentz invariance spins-statistics is also CPT invariant. Consequences: * Consider particle  at rest. Its mass is related to:  particle and antiparticle have same mass (and also same life time, charge and magnetic moment) * If a system violates CP  T must be violated,...

0 T from CPLear (6.6  1.6)10  oscillations s d K0K0 K0K0 s d t t WW

Electric Dipole Moments Energy shift for a particle with EDM d in a weak electric field E is linear in E:  E = E d. d can be calculated from d =  r i q i which is left unchanged by T: q  q T: r  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 J Under time reversal T: J   J This implies k = 0 if T is a good symmetry:  d = 0

E D M 2 expt [e cm]SM prediction proton(  4  6 ) 10  10  neutron<  ( 95% CL) 10  electron( 0.07  0.07 ) 10  10  muon( 3.7  3.4 ) 10  10  129-Xe<10  Hg<10  28 muon measurement in future "neutrino factories"  10  No signal of T violation "beyond the Standard Model" so far !

CP & T violation only in K 0 system ??? Since 1964, CP and or T violation was searched for in other systems than K 0, other particles decays, EDM... No other signal until

 production of  (4s) (10.58GeV/c 2 )  =  (4s)  B 0 B 0  B + B  BaBar (SLAC) and Belle (KEK) in 2001: observation of CP violation in the B meson system, using "asymmetric collider" B factories. KEKB machine: 8 GeV electrons 3.5GeV positron

BaBar and Belle Study of the time dependent asymmetry in decay rates of B 0 and anti-B 0  m = mass difference of "mass eigenstates" ~  /s CP violated  S ≠ 0

CP measurements at Belle Difficult: B 0 mean life  s Δz  cβγΔt ~ 200  m at Belle  (4s) z z1z1 z2z2 zz J/  Ks f CP B 0 and anti-B 0 oscillate coherently (QM untangled state). When the first decays, the other is known to be of the opposite flavour  use the other side to infer the flavour, B 0 or anti-B 0, of the f CP parent e D region of B 0 & B 0 coherent evolution

BelleBelle ACC Silicon Vertex Detector SVD Impact parameter resolution  55  m for p=1GeV/c at normal incidence Central Drift Chamber CDC (  Pt/Pt) 2 = ( 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/c , e  : CsI crystals ECL  E/E ~ E=1GeV e  : efficiency > 90% ~0.3% fake for p > 1GeV/c KL and   : KLM (RPC)   : efficiency > 90% 1GeV/c ~ 8 m 103 fb  10 8 B pairs

Belle micro-vertex detector spatial resolution B  lepton + X  z (lepton) ~ 100  m

Belle event

CP is violated in the B 0 system CP

Origin of CP violation Hamiltonian H = H 0 + H CP with H CP responsible for CP violation. Let's take H CP = 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 H CP CP † = CP (gH + g*H † ) CP † = gH † + g*H CP invariance : H CP = CP H CP 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 the hamiltonian.

Standard Model and CP violation The transitions quark(i)  quark(j) are described by parameters V ij, introduced by N. Cabibbo for i,j=u, d, s s u W V us In the '60 only u, d, s quarks were known. c was introduced in 1970 (Glashow, Iliopoulos, Maiani), discovered in In 1972 Kobayashi & Maskawa show that, in order to generate CP 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 V ij to be complex !

II III I CP violation and SM SM with 3 families can accommodate CP violation in the weak interactions through the complex Cabibbo-Kobayashi-Maskawa quark mixing matrix V CKM, with 4 parameters. uctuct dsbdsb Up type quark spinor field Q =  Down type quark spinor field Q =  but SM does not predict these parameters...

... and there is another (cosmic) problem...! CP violation in the K and B meson decays can be "explained" by the Standard Model. CP violation in the Universe (baryogenesis) cannot N B  N B N B  N B _ _   ~   Universe: N B  N B N B  N B _ _  ~   SM provides: New source for CP beyond the Standard Model?

New source(s) of CP violation ? X q q complex coupling constant X : Super Symmetric Particles, Multi-Higgs doublets, etc. Complex coupling  CP violation Search for unexpected effects in CP violation, study rare decays (<10  ) in B u, B d, B s, B c and b-baryons...

14 TeV At LHC over-constrain the SM parameters p 7 TeV p 7 TeV LHCb detector B mesons production rate ~100 times larger than in B factories  high precision in CP and door open to study rare decays Rate(bb)  10 5 sec  1 ! L = cm  s   bb =500  b

The experiment N scientists ~560 N Institutions 47 Cost ~ 76 MCHF vertexing particle identification 1y yield

Underground experimental hall POINT 8 - UX85 - Headwall Pillar March 2002 (ex DELPHI area)

Conclusion CP & 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 violation needed to probe the physics beyond the Standard Model and 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, g  2,... 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 violation Cambridge U. Press, 2000 G. C. Branco, L.Lavoura, J.P. Silva: CP violation Oxford U. Press, 1999 T. Nakada: CP Violation, status and future prospect XXXth ITEP Winter school of physics www-iphe.unil.ch IPHE