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Fundamental Symmetries
Satoshi MIHARA KEK/J-PARC
IUPAP WG.9 Nuclear Science Symposium, Tokyo 29/Aug/2017
Outline• Introduction
• Experimental “searches” for symmetry violations
• CP symmetry
• T symmetry
• Matter-antimatter balance
• Summary
Left-Right Symmetry
Photo from http://s-park.wao.ne.jp/archives/1443
Symmetries in particle physics
• Charge conjugation: C
• Parity inversion: P
• Time reversal: T
• I will try to summarize experimental quests to understand fundamental symmetries in particle/nuclear physics
• CP experiments & T experiments
CP Experiments
• Hadron experiments
• Neutrino experiments
Hadron
Kaon Experiments
• Indirect & Direct CP violations
AGS
KTeV
NA48
J-PARC KOTO Experiment• KL →π0νν̅
• Signature: 2γ+nothing
• Calorimeter and Hermetic veto detectors
• Kinematic feature (missing P)
• Reconstruct Zvtx and transverse momentum of π0
CP- CP+
KOTO Detector New photon veto installed
in April 2016
KOTO Detector New photon veto installed
in April 2016
K+ Experiments• BNL E787+E949
• Search for K+→π+νν̅
• Found 7 events
• BR = (1.73+1.15-1.05) ×10-10
Search for K+→π+νν̅ at NA62
with K+ ID
RICH particle ID
• 45 events/ year with 10 BG expectation
• Started 2016, runs in 2017 & 2018 to collect O(100) events
• http://www.lnf.infn.it/wg/vus/content/Krare.html Standard Model
by K+ decay →KL decay Isospin rotation
Standard Model• Br(K+→π+νν̅)=(8.22+0.74
-0.65±0.29)×10-11
• Br(KL→π0νν̅)=(2.57+0.38-0.36±0.04)×10-11
• Brod et al., 1009.0947
ρ
η
KL→π0νν̅K+→π+νν̅
Buras “Kaon Theory News”
Any deviation from the SM prediction is a sign of new physics
B Factory Experiments
•BaBar •Belle ( and Belle II ) •LHCb
• CP violations only in the kaon system before B factory Exps. started
• Hadronic uncertainties
• These uncertainties reduced thanks to much larger mass of B
• Numerous measurements of CP violation by Babar, Belle and LHCb
• And better precision in Belle II and future LHCb
CP violation at B factories
B̅0 B0
CP odd CP even
CP Violation in the baryon sector
• LHCb new result
• Λ0b , Λ̅0b
• 3.3σ deviation
• More statistics for confirmation
Nature DOI: 10.1038/NPHYS4021
Comparison of K and B Results
ρ
ηK
B
New Physics!T. Yamanaka
Neutrino
Long Baseline Neutrino Experiments
•T2K in Japan •NOvA in the US
T2K
NOvA
Neutrino CP• Mixing matrix in standard 3-neutrino mixing framework:
• Under the CP symmetry, we expect
Accessible through neutrino oscillations Majorana phases
Not same if δCP≠0
New Result from T2K• E-like observation vs. prediction
• Excess in neutrino mode (top)
• Deficit in anti-neutrino mode (bottom)
M. Hartz, KEK Colloquium, Aug 2017
New Result from T2K• Fit without the reactor constraint: closed contour in δCP at 90%CL
• Adding the reactor constraint improve the constraint on δCP
M. Hartz, KEK Colloquium, Aug 2017δCP=0, π outside of the 2σ CL intervals
Time Reversal
• Stringent limit by neutron EDM experiments
• Test of time reversal symmetry using polarized beam
Neutron EDM• Existence of EDM implies violation of Time Reversal Invariance
• Standard Model EDMs are due to CP phase in CKM, but extremely small → Sensitive to new physics!
• Current best limit: < 3.0×10-26 e・cm from ILL
Experimental Technique
• ILL-Grenoble experiment
• Trapped Ultra-Cold Neutrons (UCN) with NUCN = 0.5 UCN/cc
• |E| = 5 - 10 kV/cm
• 100 sec storage time
Harris et al. Phys. Rev. Lett. 82, 904 (1999)
Baker et al. Phys. Rev. Lett. 97, 131801 (2006) σd<3×10-26 e・cm
P. Schmidt-Wellenburg
Sensitivity to New Physics
Pendlebury & Hinds, NIMA 2000More nEDM results in near future!
P. Schmidt-Wellenburg
Time Reversal Test using Polarized Beam
• MTV at TRIUMF-ISAC, 8Li beam
• Test of time-reversal symmetry in polarized nuclear beta decay by measuring a triple correlation
• J: parent nuclear, σ: electron polarizations
• Electron polarization examined by utilizing the analyzing power of Mott scattering
• DAQ in progress in 2016-2017 to reach R≃O(10-4)
Matter-antimatter imbalance
Matter-antimatter imbalance
• Non-zero baryon number in the current universe
• The universe is made mainly of matter
• Sakharov conditions should be satisfied
• Violate baryon number symmetry
• Violate both C and CP symmetries
• Depart from thermal equilibrium
• Electroweak baryogengesis / Leptogenesis
PDG
Planck 2015
Leptogenesis
• How can we (experimentalist) confirm “Leptogenesis” ?
• M. Fukukita IPMU news
cLFV and MR
• Type-I SeesawR. Alonso et al, JHEP01 (2013)118
Br(μ→e)/Br(μ→eγ)
Br(μ→e)/Br(μ→eee)
Summary
• Fundamental symmetries have provided important information for us to understand the physics
• Understanding broken symmetries, or how the symmetry is broken, is more interesting than finding a new symmetry
Symmetry Breaking !
Symmetry Breaking !Cherry tree in Sion
Cherry tree in Nagano