Summary of the Lepton Flavor Violation Session
Tomáš Blažek Comenius University Bratislava
15 June 2012 Theory bottom-up approach: non-unitarity tests and LFV constraints
. Note: for Quark Flavor Violation we have become spoiled and got used to unitarity for the
2x2 light quark block in the CKM matrix: Vud ~1, Vus ~0.2, Vcd ~ -0.2, Vcs ~1 ... This comes from hierarchy in the complete 3x3 CKM matrix and is highly non- standard... it may not repeat in the Lepton Flavor Violating PMNS matrix
.
Theory LFV in top-down approach: a tool to distinguish among models
Muon to Electron Conversion • Neutrinoless conversion of a muon to an electron in the near field of a nucleus N e N
• Example of Charge Lepton Flavor Violation • Signal is certain indication of new physics • Complementary to other cLFV reactions, e.g. e e • Two experimental programs are under development: Mu2e at Fermilab and COMET at JPARC, each with the goal to improve on the current limit by 4 orders of magnitude, 6x10-17. COMET Phase I will go for 2 orders of magnitude. • May be channel most capable to get ultimate sensitivity- 10-18 at Project X with proton, muon and detector upgrades
Note Watch out for dimensionless numbers: Mu to e conversion is normalised to the muon capture rate. Mu to e gamma is normalised to the muon decay width. Sensitivity btw the two can be roughly compared by dividing the Mu to e gamma number by a factor of 100. Thus they are approximately equally sensitive / competitive to the LFV form factors. Mu2e Muon Beam Line at Fermilab • Re-purpose existing rings and beam lines at Fermilab as much as possible to save costs • Goal 6x10-17 @ 90 % CL (x10000 improvement over current) • Just had DOE CD1 review last week, went well, decision shortly • Begin construction 2013, data-taking 2019 • Three superconducting solenoids in series Will deliver – Production Solenoid (PS), 4m long ~0.002 stopped – Transport Solenoid (TS), 13 m long muons per 8 GeV – Detector Solenoid (DS), 11 m long – Warm bore, evacuated to 10-4 Torr proton Production Solenoid protons Detector Solenoid
Transport Solenoid Jim Miller, Boston University 10 COMET staging plan
Phase1 Phase2
Pion Capture Section Pion Capture Section At J-PARC A section to capture pions with a large A section to capture pions with a large solid angle under a high solenoidal solid angle under a high solenoidal
magnetic field by superconducting magnetic field by superconducting Pion Capture Section Production maget Production maget Target A section to capture pions with a large Target solid angle under a high solenoidal magnetic field by superconducting Production maget Target
Detector Section Detector Section
A detector to search for A detector to search for muon-to-electron conver- muon-to-electron conver-
sion processes. sion processes. Detector Section Stopping A detector to search for Stopping cylindricalT arget muon-to -electron conver- Target sion processes.
Stopping detector Target
Pion-Decay and Pion-Decay and Muon-Transport Section Muon-Transport Section
A section to collect muons from A section to collect muons from decay of pions underPhase a solenoi- I decay of pions under a solenoi- dal magnetic field. Pion-Decay and dal magnetic field. Muon-Transport Section • Begin construction 2013 A section to collect muons from decay of pions under a solenoi- dal magnetic field. • Commence data taking in 2017-
B(μ+Al→e+Al)<7x102018-15 @ 90%CL B(μ+Al→e+Al)<6x10-16 @ 90%CL
• But with reduced sensitivity Beam and background study 15
B( Al e Al ) 7 10 @ 90% CL
• Also serves as background study
for phase 2
Akira SATO, - Motivation for Proton Measurement, COMET - 8 11 Jim Miller, Boston University
Concluding Remarks
charged Lepton Flavor Violation:
• experiment constantly pushing its way down to orders of magnitude lower limits
• not guaranteed to find LFV in processes involving charged leptons
• certainly well motivated and worth trying, the signal could be discovered any time
• huge potential to learn about Physics Beyond the Standard Model