The Origin of Matter
Tsutomu T. Yanagida (IPMU , Tokyo)
台湾大学 ３月８日、２０１６年
Energy Content of the Universe
いいい
From Wikipedia ＦＦ
Ｆ
Galaxy and Cluster of galaxies
No antimatter is present
Observations have ruled out the presence of
antimatter in the Universe up to the scale of
clusters of galaxies ( ). Most significant
upper limits are given by annihilation gamma
rays:
Upper bounds of antimatter fraction
G. Steigman (2008)
The universe is composed of only matter and
not antimatter
However, antimatter could have been
equally present in our universe, since there is no difference between particles and
antiparticles except for their charges.
In fact, Paul A.M. Dirac proposed a matter-
antimatter symmetric universe in his Nobel
Lecture in 1933.
If we accept the view of complete symmetry between positive and negative electric charge so far as concerns the fundamental laws of Nature, we must regard it rather as an accident that the Earth (and presumably whole solar
system), contains a preponderance of negative electrons and positive protons.
It is quite possible that for some of the stars it is the other way about, these stars being built up mainly of positrons and negative protons. In fact, there may be half the stars of each kind. The two kinds of stars would both show exactly the same spectra, and there would be no way of distinguishing them by present astronomical methods.
The symmetric Universe
was proposed by Paul Dirac
In 1933.
I. Why is the present universe NOT symmetric?
How much asymmetric ?
Matter = Atoms Matter Abundance = Numbers of Protons and Neutrons
The baryon asymmetry
The baryon asymmetry
Spergel et al (WMAP) Tegmark et al
Kirkman et al
Very small !!!
Our universe may have begun symmetric
If our universe began baryon symmetric,
those tiny imbalances in numbers of baryons and antibaryons must be generated by some physical processes in the early universe.
What are the processes ?
The present particle physics may answer to this fundamental question
(If the universe had been symmetric, baryons and antibaryons started to annihilate each others when the temperature became well below the nucleon mass. The number of post-annihilation nucleons would be a billion times less abundant than observed today.)
Ｇｅｎｅｒａｔｉｏｎ ｏｆ the baryon asymmetry
A.D.Sakharov (1966)
The theory of the expanding universe, which presupposes a superdense initial state of matter, apparently excludes the possibility of macroscopic separation of matter from antimatter; it must therefore be assumed that there are no antimatter bodies in nature, i.e., the universe is asymmetrical with respect to the number of particles and antiparticles (C asymmetry)…..
We wish to point out a possible explanation of C asymmetry in the hot model of the expanding universe by making use of effects of CP invariance violation (see [2])……...
The discovery of CMB in 1964
The discovery of CP Violation in 1964
in the decays of neutral kaons
A. A. Penzias and R. W. Wilson
J. Cronin, V. Fitch
Three conditions must be satisfied to produce an imbalance of baryons and antibaryons
I. Violation of baryon number conservation II. Violation of C and CP invariance
III. Out-of-thermal equilibrium process
II. Baryogenesis in the standard theory
C violation was discovered in 1957
CP violation was discovered in 1964 J. Cronin, V. Fitch C.-S. Wu
The second condition is satisfied
Is the first condition of baryon number
violation also satisfied ?
Baryon number violation in the standard theory
G. ‘t Hooft (1976)
The baryon number is not conserved at quantum level
The weak instanton induces baryon number violation, but the amplitude is suppressed by
The proton decay is suppressed as
Saddle-point solution in the standard theory (Weinberg-Salam Model)
N.S. Manton (1983)
F.R. Klinkhamer , N.S. Manton (1984)
E
0 1
-1 ===========> Q (A,H)
instanton
●
sphaleron
1/2
（ＷＫＢ）
Unsuppressed baryon number violation in the early universe
V.A. Kuzmin, V.A. Rubakov, M.E. Shaposhnikov (1985)
The rate baryon number violation :
It exceeds the expansion rate of the universe above
The first condition is satisfied
P. Arnold, L. McLerran
The third condition may be satisfied if the electro- weak phase transition is the first order
This requires the Higgs boson mass,
But, it is excluded by LEP experiments
The condition III is not satisfied !!!
The standard theory is unable to explain the baryon number asymmetry
I. No out-of-thermal equilibrium process II. Too small CP violation
Ｊａｒｌｓｋｏｇ ｄｅｔｅｒｍｉｎａｎｔ
cf. cold electroweak baryogenesis
The Nobel Prize in Physics 2015 was awarded for the discovery of neutrino oscillations, which show that neutrinos have small masses
The presence of small neutrino masses may
give us a natural mechanism for creating the
observed baryon asymmetry in the Universe!!!
III. Discovery of neutrino oscillation
The solar neutrino problem
Raymond Davis
Davis found only one-third of the neutrinos predicted by the standard solar theories
John Bahcall
Yoji Totsuka
Superkamiokande confirmed the result of Davis in 1998 Superkamiokand dicovered the oscillation of
the atmospheric neutrinos in 1998
(1964-1996 at Homestake)
Masses and mixing angles for neutrinos
The recent global analysis gives
T. Schwetz, M. Tortola, J.W.F. Valle (2011)
cf.
Why are neutrino masses so small ?
Introduction of right-handed neutrinos
neutrino mass term :
The standard theory
cf. top-quark mass term :
So small !!!
Seesaw mechanism
T. Yanagida (1979)
Gell-Mann, Ramond, Slansky (1979) P. Minkowski (1977)
is singlet and has no charge. Thus it may have a large Majorana mass
neutrino mass matrix :
Pauli-Gursey transformation: Weyl fermion Majorana fermion
Two mass eighen values :
The observed small neutrino masses strongly suggest the presence of super heavy Majorana neutrinos N
Out-of-thermal equilibrium processes may be easily realized around the threshold of the super heavy neutrinos N
The Yukawa coupling constants can be a new source of CP violation
GUT Baryogenesis
M. Yoshimura (1978)
Ignatiev, Krosnikov, Kuzmin, Tvkhelidze (1978)
Delayed decay of heavy colored Higgs boson
S. Weinberg (1979)
Baryon asymmetry can be produced in the decay processes But, we have two serious problems:
I. It predicts proton decay, but the decay was NOT observed II. The produced B asymmetry is washed out by the sphaleron
processes
Sphaleron
If , the B asymmetry is washed out by the sphaleron processes. The generation of B-L asymmetry is necessary
B-L is conserved !!!
However, the GUT preserves the B-L and hence the B-L asymmetry is not generated
IV. Leptogenesis
M. Fukugita, T. Yanagida (DESY 1986)
Decay of the super heavy Majorana neutrino N :
If CP is broken, the lepton asymmetry is generated in the delayed decay of N in the early universe
Two decay channels
The lepton asymmetry is converted to baryon asymmetry by the sphaleron processes
J.A. Harvey, M.S. Turner (1990)
The first detailed calculation for the baryon asymmetry
M. Plumacher (1997)
Asymmetry parameter:
Assume decay is most important
for the maximal CP violation
+
……...
(neglecting the flavor effects)
In the early universe , the heavy Majorana were
produced by the scattering processes in the thermal bath. As the temperature went down , the started to decay and produced the lepton asymmetry. This lepton
asymmetry was converted to the baryon asymmetry.
The out-of equilibrium decay condition (delayed decay)
!!!
The washing out effects ;
We have the upper bound
Very consistent with the observed neutrino masses !!!
W. Buchmuller, P. Di Bari, M. Plumacher (2004)
The baryon asymmetry in the present universe
can be explained for and
G.F. Giudice et al (2004)
The produced B-L asymmetry is calculated by solving the Boltzmann equations;
accounts for decays and inversed decays represents the scattering
is the total washout term of B-L asymmetry
Produced lepton asymmetry for ,
Buchmuller, Bari, Plumacher (2002)
V. Summary
In particular,
Very consistent with observation :
(pre-existing B-L may be washed out)
Test of the Leptogenesis
The standard theory + right-handed neutrinos
It explains two fundamental parameters simultaneously:
I. Small neutrino masses
II. Universe’s baryon asymmetry
Very Consistent !!
Can we test the leptogenesis ?
A robust prediction is
It may be impossible to test this prediction The leptogenesis has two testable predictions
I. CP violation in neutrino oscillations
II. Neutrinoless double beta decays
T2K experiments (2011)
We will see it in future
N N’
e e
W.H. Furry (1939)
CP violation in neutrino oscillations
!!!
T2K experiments
What is the Next ?
The neutrino masses observed in neutrino oscillation experiments strongly support the leptogenesis
See my talk at NCU
“The Seesaw Mechanism --- 37 Years Later ---”
