Transcript ZZY2015_YiLiang_ready08x

赵忠尧奖学金申请答辩
中国科学院大学物理学院
申请人：梁翼
2015-05-23
Outline
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Education history
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Previous study
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Current interest and future research plan
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Summary
Education history
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MSc, 2007~2009, at McMater University,
with Dr. R. Bhaduri
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PhD, 2009~2014, at University of Alberta,
with Dr. A. Czarnecki
Previous study
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Photon-photon scattering
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Higgs decay
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Anomalous magnetic moment of the
positronium ion
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Muon decay spin asymmetry
Scattering of photons on photons
Heisenberg & Euler (1936):
Fujita & Kanda (2011):
Reason of the wrong result
They incorrectly treated divergent integrals
Singularities need to be
taken care of properly.
The same mistake: Gastmans et al. (2011):
New expression was proposed based on a similar argument. Can. J. Phys., 2012, Vol. 90, No. 1 : pp. 11-16
Yi Liang, Andrzej Czarnecki
(Best Paper Award)
Higgs decay to two photons
Expansion by regions
…
hard
Soft or
Ultra soft
Calculation with DR
We proved in two ways that even a very heavy Higgs can decay into two photons.
collinear
Magnetic moment of Positronium Ion
The Ps- ion does not have any excited states in the discrete spectrum so one cannot study its spectroscopy in
the traditional sense. G factor is a new observable for the Ps- ion which is likely to be experimentally accessible.
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Chraplyvy
transformation
Chraplyvy
transformation
for three body
Phys. Rev. A, 2015, Vol. 91, 012514
Andrzej Czarnecki, Yi Liang
New. J. Phys, 2014, Vol. 16, 063045
Yi Liang, Andrzej Czarnecki
The purpose is to determine to what extent the interaction of the positron with the two electrons modifies the magnetic moment of the ion. This
effect is expected to be analogous to that in hydrogen-like atoms and ions, where the nuclear electric field modifies the g factor of an electron.
Magnetic moment of Positronium Ion
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New. J. Phys, 2014, Vol. 16, 063045, Yi Liang, Andrzej Czarnecki
Phys. Rev. A, 2015, Vol. 91, 012514, Andrzej Czarnecki, Yi Liang
Muon decay spin asymmetry
signal
eg
background
  e gnn
(radiative decay)
e+ + g
+
e+
e-
Muon decay spin asymmetry：
-
+
e+
Phys. Rev. D, 2014, Vol. 90, 053004, Fabrizio Caola, Andrzej Czarnecki,
Yi Liang, Kirill Melnikov, Robert Szafron
Charged lepton flavor violation (cLFV)
  e g
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Not too heavy
Not too light, more sensitive to New Physics
Only one decay mode: electron and neutrinos
Long lifetime
PSI 质子加速
器
Charged lepton flavor violation (cLFV)
cLFV decays in the SM is radiatively induced by neutrino masses.
At a negligible level
MEG sets
All SM extensions enhance the rate through mixing in the high energy sector of the theory
• Clear evidence for physics beyond the SM
• Restrict parameter space of SM extensions
Charged lepton flavor violation (cLFV)
signal
eg
background
  e gnn
(radiative decay)
e+ + g
+
e+
e-
Muon decay spin asymmetry：
The two-loop correction to the
asymmetry is the first QED
effect that may explain a small
deviation of Pξ from 1.
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+
e+
Phys. Rev. D, 2014, Vol. 90, 053004, Fabrizio Caola, Andrzej Czarnecki,
Yi Liang, Kirill Melnikov, Robert Szafron
EFT analysis on the 1-loop cLFV
EFT analysis on the 1
loop correction to cLFV
eg
JHEP, 2014, Vol. 10, 014,
Giovanni Marco Pruna, Adrian Signer
Extended Lagrangian
Constraints on the Wilson coefficients
Status and plan
What we can do:
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 
e gnn
A full calculation in SMEFT for the cLFV at 1-loop
Higher-order corrections to RMD
(radiative decay)
Computation at the higher-order RMD in SMEFT.
This analysis can be used to any observable for which there are strong experimental
constraints (Higgs physics, B physics, tau decay etc.).
EFT & numerical calculation of the standard LFV muon decay at one-loop
Expect at least 1 paper
Two-loop corrections of the polarized RMD in SM and analysis in SMEFT.
2 to 3 papers
Apply the same procedure to other process (tau decay for example)
1 to ? papers
Summary
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PhD study achievements
Extensive experiences in loop diagram calculation.
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Research plan
Higher-order correction of process in collider
physics (RMD for example), loop calculation plus SMEFT.
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Result estimation
Thank you
Cross section
Total squared
amplitude:
Summation of the square of different terms with particular polarizations
Visible light in space
Planck's law:
Mean free path:
Heisenberg
& Euler :
Fujita &
Kanda:
Ward identity & Dimensional regularization
Scattering amplitude:
WI
CC
GI:
Dimensional regularization:
Higgs decay to two photons
Expansion by regions
Hard region:
Soft region:
Ultra-soft region:
Collinear region:
Integral by regions
Calculation with DR
Cut on triangular loop
Calculation with DR
W boson triangular loop
Deformation of the contour
Magnetic moment of positronium ion
The Dirac equation should be decoupled in order to derive the Schrödinger equation
Chraplyvy
transformation
Foldy
Chraplyvy
transformation
for three body
Wouthuysen
FW reduction
The purpose is to determine to what extent the interaction of the positron with the two electrons modifies the magnetic moment of the ion. This
effect is expected to be analogous to that in hydrogen-like atoms and ions, where the nuclear electric field modifies the g factor of an electron.
Magnetic moment of Positronium Ion
>
>
Phys. Rev. A, 2015, Vol. 91, 012514, Andrzej Czarnecki, Yi Liang
New. J. Phys, 2014, Vol. 16, 063045, Yi Liang, Andrzej Czarnecki
Chraplyvy
transformation
Chraplyvy
transformation
for three body
Charge conjugation parity:
Charge conjugation is conserved under electromagnetic interactions, this is because laws
of electrodynamics are invariant under the interchange of particle and antiparticle pairs.
Positronium Ion
Trial wave function
3
1
2
Possible measurement scheme
B
A possible scenario of a measurement could be as follows. An ion with a known initial polarization could be subjected to the
magnetic field, where its polarization would precess. | The annihilation process occurs predominantly within a spin-singlet
electron-positron pair, so that the total spin direction of the ion is preserved by the surviving electron, and can be detected.
Hamiltonian constructed by two parts
Krajcik-Foldy transformation
KF transformation
Galilean
transformation
Muon decay spin asymmetry
LO
NLO
A deviation of the measured value of
from unity may be interpreted as the effect
of higher order QED corrections or effects
of physics beyond the Standard Model.
There is a parity violating
asymmetry of the electron
distribution with respect to
the muon spin, favoring the
production of high energy
electrons in the direction
counter to the muon spin.
Jet algorithm
NNLO
Dependence on y
EFT analysis of RMD
Full QED
EFT analysis on the 1
loop correction to cLFV
eg
Hard 
matching
NRQED
Soft 
matching
pNRQED
Ultrasoft 
Limits on the Wilson coefficients are the most direct information on possible BSM models
that can be obtained from the cLFV decay in an EFT framework.