Schöning/Rodejohann 1 Standard Model of Particle Physics SS 2013
Lecture:
Standard Model of Particle Physics
Heidelberg SS 2013
Flavour Physics I + II
Schöning/Rodejohann 2 Standard Model of Particle Physics SS 2013
ContentsPART I
Determination of the CKM Matrix
CP Violation in Kaon system
CP violation in the B-system
PART II
Search for Flavor Violating Neutral Currents (Lepton Flavor Violation)
Search for Lepton/Baryon Number Violation
Schöning/Rodejohann 3 Standard Model of Particle Physics SS 2013
Flavour Changing Neutral Currents...are forbidden in the SM at tree level (GIM mechanism)
d
b
γ, Z
μ-
γ, Z
μ+
branching ratio=0
d
b
γ, Z
μ-
γ, Z
μ+
t
W
W
penguin diagram
branching ratio enhanced by new physics!
arXiv:1112.3564
Schöning/Rodejohann 4 Standard Model of Particle Physics SS 2013
Recent Results from LHCBSearch for
Bs → μ+μ
−
(95% CL) SM expected 1.1 x 10-10
SM expected 3.2 x 10-9
well compatible with SM expectation
not much room for physics beyond the SM
ATLAS and CMS also looking into this channel
Schöning/Rodejohann 5 Standard Model of Particle Physics SS 2013
Lepton Flavor Violation (FCNC)...also forbidden in the SM at tree level (GIM mechanism)
γ, Z
μ-
γ, Z
μ+
branching ratio=0
γ, Z
μ-
γ, Z
μ+W
W
penguin diagram
branching ratio largely enhanced by new physics (40 orders of magnitude)!
μ-
τ+
μ-
τ+
ν(Δmν
2)2
mW4 ≈ 10−50
suppressed
Schöning/Rodejohann 6 Standard Model of Particle Physics SS 2013
● Neutrino Oscillations: solar neutrinos reactor neutrinos atmospheric neutrinos neutrino beams
P =sin22sin21.27m2 LE
μ
W W
l
ν1ν
2
Discovery of Neutrino OscillationsDiscovery of Neutrino Oscillations
Schöning/Rodejohann 7 Standard Model of Particle Physics SS 2013
Cabibbo Kobayashi Maskawa (CKM) Pontecorvo Maki Nakagawa Sakata (PMNS)
Quarks Leptons
d 's 'b ' =
V ud V us V ub
V cd V cs V cb
V td V ts V tbdsb
e
=
V e1 V e2 V e3
V 1 V 2 V 3
V 1 V 2 V 3
1
2
3
Fermion MixingFermion Mixing
● W bosons smell different flavors!● other gauge bosons (γ, Z, g) do not (→ no FCNC)
Schöning/Rodejohann 8 Standard Model of Particle Physics SS 2013
Cabibbo Kobayashi Maskawa (CKM) Pontecorvo Maki Nakagawa Sakata (PMNS)
Quarks Leptons
d 's 'b ' =
0.974 0.225 0.0030.225 0.973 0.0410.009 0.040 0.999
dsb
e
≈0.816 0.577 0.2
0.408 0.577 0.7070.408 0.577 0.707
1
2
3
● W bosons smell different flavors!● other gauge bosons (γ, Z, g) do not (→ no FCNC)
Fermion MixingFermion Mixing
Schöning/Rodejohann 9 Standard Model of Particle Physics SS 2013
quark flavor not conserved(family number changes)
lepton flavor not conservedbut difficult to observe!
(concept of families right?)
Family Number ViolationFamily Number Violation Flavor Changing neutral currents are forbidden!
Lepton Flavor Number in Charged Currents is an “adhoc” concept
light andsmall mass splitting
Schöning/Rodejohann 10 Standard Model of Particle Physics SS 2013
Lepton Decays:
μ→ e γ μ→ eee
τ→ e(μ) γ τ→ l l l (l=e,μ) τ→ l h
Conversion (μ-Capture):
μ N → e N
Fixed Target Experiments:
μ N → τ N e N → μ(τ) N
Collider Experiments:
e p → μ(τ) X
Z' → l l'χ0,± → l l' X
Meson Decays: Φ, K → ll' D, J/ψ → ll' B, Υ → ll'
LFV
proposedproposed
LHC
HERA
Overview LFV ExperimentsOverview LFV Experiments
Schöning/Rodejohann 11 Standard Model of Particle Physics SS 2013
But (Charged) Lepton Flavor Violation not seen:
The SM prediction for Lepton Flavor Violating (LFV) Processes is negligible (GIM-like suppression)
Any sign of LFV would manifestNew Physics
Charged Lepton Flavour Violation Leptons mix in a similar way as quarks (→ PMNS matrix, W.R next week)
Lepton mixing discovered in neutrino oscillations
muon to electron conversion experiments
Schöning/Rodejohann 12 Standard Model of Particle Physics SS 2013
Muon-Electron Conversion
μ
μ N → e N conversion
muon capture in nucleons muon decays in orbit
Schöning/Rodejohann 13 Standard Model of Particle Physics SS 2013
SINDRUM II Result
no sign of a signal!
μ N → e N conversion
electron receives kineticenergy from muon mass minus nuclear recoil energy
μ- N
e- N
Schöning/Rodejohann 14 Standard Model of Particle Physics SS 2013
But (Charged) Lepton Flavor Violation not seen:
The SM prediction for Lepton Flavor Violating (LFV) Processes is negligible (GIM-like suppression)
Any sign of LFV would manifestNew Physics
Charged Lepton Flavour Violation Leptons mix in a similar way as quarks (→ PMNS matrix, W.R next week)
Lepton mixing discovered in neutrino oscillations
muon to electron conversion experiments
Schöning/Rodejohann 15 Standard Model of Particle Physics SS 2013
Limitation: accidental background
better space resolutionimprove tracking
current limit: BR(μ+ → e+ γ) < 5.7 x 10 – 13
MEGstart 2007 (MEGA: 10 - 1 1)
The MEG ExperimentThe MEG Experiment
still taking data upgrade planned starting next year
LFV decay: μ+ → e+ γ
Schöning/Rodejohann 16 Standard Model of Particle Physics SS 2013
Mu3e ExperimentSearch for the decay: μ→ eee SM prediction: B(μ→ eee)≪10−50
current limit B(μ→ eee)< 10−12
Design and construction: Heidelberg
planned sensitivity: B(μ→ eee)< 10−16
will be performed at the Paul Scherrer Institute (PSI) in 2014+
e-
X
μ+
e-
e+
Schöning/Rodejohann 17 Standard Model of Particle Physics SS 2013
Baryon and Lepton Number ViolationProton is stable: τ > 1031−1033 years
p→π0 e+
No observation of Baryon or Lepton Number Violation!
π + → e+ γ
Not seen:
p→π+ γ
However, baryon or lepton number violating processes are required to explainmatter antimatter asymmetry in universe
The fact the humans and life exists on earth (no radiation damage) excludesalready BSM scenarios!
New BSM Physics is required!
Super Kamiokande
Schöning/Rodejohann 18 Standard Model of Particle Physics SS 2013