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Theory of flavour physics

27.03.2008

Svjetlana Fajfer

Physics Department, University of Ljubljana and

Institute J. Stefan, Ljubljana, Slovenia

Physics in Ljubljana July 17-24 2011, Ljubljana,

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Quarks, leptons and gauge bosons behave as a point-like particles.

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Why do we need accelerators? Heisenbergs uncertainty principle (1927):

Units

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Large Hadron Collider (LHC) ‏

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CDF 

D0 

Fermi National Accelerator Laboratory

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Fermi National Accelerator Laboratory

10!18 GeVfundamental fermions: point-like on the scale

Interactions

electromagnetic

strong

weak

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Quarks

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Nucleus

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Quantum electrodynamics (QED)‏

Fine structure constant

Low energies

High energies

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Screening the electric charge

Fine structure coupling changes with the energy !

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Pauli’s principle: two fermions cannot occupy the same state

One more reason for the colour existence :

QED and QCD

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Feynman’s diagrams

Richer structure of QCD than QED

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Quantum chromodynamics

“+”sign number of quarks

Asymptotic freedom SD = Shirt Distance (Perturbation Theory)

Quantum Field Theory: RG = Renormalization Group Effects

LD = Long Distance (Non-Perturbative Physics )

Weak interactions

Long lifetime, Small cross sections

Weak currents:

-  charged -  neutral

W±

Z0

mW± = 80.4 GeVmZ0 = 80.4 GeV

Fermi theory complete theory

Comparison weak and electromagnetic interactiopns

Parity violation in weak interactions

Leptons Quarks

Cabibbo mixing

!c = 130experimentally

CKM mixing

Cabibbo-Kobayashi-Maskawa

Unification : weak + electromagnetic

Example:

In the unification first we start with massless gauge bosons

physical fields

Only three parameters are free! We know everything about electroweak interactions if these Parameters are known!

Basic properties in the Standard Model

1.  Charged current Interactions only with left-handed quarks

2.  Quark mixing (weak eigenstates ≠ mass eigenstates

weak eigenstates CKM unitary matrix mass eigenstates

3. GIM mechanism – natural suppression of FCNC

GIM mechanism

All three quarks in the loop contribute making the decay width very suppressed!

There are no tree level processes in which the neutral currents change flavour!

BR(KL ! µ+µ!) = 6.84" 10!19

CP violation within CKM

CP Violation arises from a single phase in W± interactions of quarks !

Wolfenstein parametrization

Unitarity triangle

One of goals of particle physics!

Tree Level Decays

Loop induced processes

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Strong interactions contribute in the weak processes

Standard Model

gives masses to all elementary fermions and gauge boson

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Masses are created due to the spin 0 Higgs boson!

Most wanted at LHC!

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Why we are not satisfied with Standard Model?

  Hierarchy problem;

  Neutrino masses- neutrino oscillations;

  Does not include gravity;

  Does not explain astrophysical results:

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Within SM quantum corrections to fermion masses would depend only logarithmically on scale Λ (“mass is protected”):

δmf ~ mflnΛ 

QED – electron self energy!

Hierarchy problem of SM

The elementary Higgs sector exhibit following feature: corresponding quantum corrections to scalar particle (Higgs) would exhibit a quadratic dependence on scale Λ. This means that Higgs mass is extremly sensitive to the scale of the NEW physics!

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Gauge hierarchy problem (naturalness problem)

within Standard Model these quadratic divergences cannot be cancelled!

FINE TUNING PROBLEM in SM !

In order to have stable mass of the Higgs boson we expect new physics ~ 1 TeV!

quadra0c divergences : 

The cutoff above which  enters physics beyond SM. 

Search for new physics

Direct search:

l q q

l

g ~ q ~ l ~ χ02

~ χ01 ~

p p

Indirect search at low energies:

Instead of SM in the loops new physics particles

Flavour theory

Basic questions of the flavour theory

Georgi-Glashow (1974) proposed

Matter fields are in representation

Proton might decay: Current experimental limit

years

GUT theories

Experimental situation:

In order to realize unification there are plenty of proposals: -  Introduction of new particles which modify unification -  Super- symmetry (one of most favorable scenarios of new physics)

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Most popular scenarios for the gauge hierarchy problem

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SUPERSYMMETRY (a space-time symmetry) - postulates existence of bosonic matter particles, and fermionic carriers of interactions, not exact, since supersymmetric partners must be heavy as they have not been observed; for every known particle there should be a supersymmetric partner

Supersymmetry

Svjetlana Fajfer Borut Bajc Bojan Golli Jernej Fesel Kamenik Rajmund Krivec Matej Pavšič Saša Prelovšek Komelj Jure Zupan

full professor (FMF +IJS) senior research associate (IJS) associate professor (PEF +IJS) postdoctoral associate (IJS) research advisor (IJS) research advisor (IJS) assistant professor (FMF +IJS) assistant professor (FMF +IJS)

THEORY OF NUCLEUS, ELEMENTARY PARTICLES

AND FIELDS

Miha Nemevšek, posdoc. (ISTP, Trieste +IJS) Nejc Košnik, posdoc. (LAL,Orsay, +IJS)

PhD students: Jure Drobnak, 2008č Timon Mede, 2009 Vasja Susič, 2010, Ivan Nišandžić, Ivana Mustać

Theoretical predictions of the group are included in measurement projects of laboratories Belle, Ba Bar, Fermilab (FOCUS and CDF) and future LHC collider.

Grand Unified Theories: ICTP Trieste; Laboratori Nazionali Gran Sasso

Flavour physics: Technion, Haifa; CERN theory division, University of Oslo; Ecole Polytechnique Paris; University Paris-Sud, Orsay; PMF Zagreb; Cornell; Carnegie Mellon ; Frascati Laboratory, Univ. Torino, Univ. of Cincinaty,

BP

Underlined: Bilateral projects Members of FLAVIANET

Lattice chromodynamics: Collaboration RIKEN-Brookhaven-Columbia, Bern Graz Regensburg Collaboration

Nuclei and elementary particles (FMF, UL) S. Fajfer Physics (FKKT, UL) S. Fajfer, S. Prelovsek

Field theory (FMF – graduate course, UL) B. Bajc

Theory of particles and nuclei (FMF – graduate course, UL ) S. Fajfer, J.F. Kamenik

Modern physics (FMF, UL) S. Fajfer

Mathematical physics (PEF, UL) B. Golli

Experiments in physics (PEF, UL) B. Golli

Standard Model (ICTP) B. Bajc

A short introduction to supersymmetry (Odense, Denmark) B. Bajc

Exercises at Physics Department, UL: S. Prelovšek, J.F.Kamenik, T. Mede, J. Drobnsak

S. Prelovšek Scalar meson puzzle: - first dynamical simulation with good chiral properties gives mass of lowest qq with I=1 close to a0(1450). - this indicates that a0(980) may not be qq, but tetraquark - first simulation of sigma meson with dynamical u,d and s quarks; finding mass about 700 MeV, close to observed value - analytical prediction for effects of lattice artifacts on scalar correlators, which agree with lattice data very well Excited meson spectra: - challenging determination of first and second excited state of pion and rho mesons, close to observed masses

  discretization of space-time,   path integrals and

  fast computers

Future projects:

- simulation of tetraquarks

- spectra of hadrons that can decay on the lattice

- study of hadron decays on the lattice

Fajfer, Zupan, Kamenik, Košnik, Drobnak, Nišanđić, Mustać ,

FLAVOUR PHYSICS

Top quark physics: - production ob t bar t, - single top production, - top at hadronic colliders, - weak decays within SM and NP;

New physics in charm meson rare decays;

B meson physics: SM and NP -  B meson oscillations, -  FCNC decays, Leptonic and nonleptonic decays;

hints of New Physics?

ELECTROWEAK CONSTRAINTS FROM B PHYSICS

developed method used for first tree level CKM phase determination

LHC and low and high energy

constraints from flavor physics

flavor physics@LHC:

GRAND UNIFICATION B. Bajc, I. Doršner, M. Nemevšek, students T. Mede, V. Susic