Outlook: The Next Twenty Years Page: 3 of 19
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The second category is the vertical questions.
W 1 al y m *CLa11 U UL V -m UCJ jJy.7SE7. .L aly a.7 ,
TeV is the key.
L(1, 2, -1),
Table 1. The quantum
don't understand. Here,
handed chirality states.
Figure 3. The table of particles in the Standard Model.1 Ver-
tical Questions are concerned with particles in a single gen-
eration, while Horizontal Questions refer to the relationship
sideways in the table.
de sF be
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Figure 4. The mass spectrum of quarks and leptons we don't
ing physics topics must once go through the study of
the TeV scale before they reach their own destina-
tions. It is a hub where everybody has to transfer to
Why do I think so? To see this, let me start
enumerating the big questions in our field. I broke
them down to four categories.
The first category is what I call the horizon-
tal questions. They are about relationships between
the three families of elementary particles (Fig. 3).
Why are there three generations and no more?
What physics determines their masses and mixings
(Fig. 4)? What is the energy scale of that physics?
Why do neutrinos have mass and yet they are so
light? What is the origin of CP-violation? What
is the origin of the matter-antimatter asymmetry in
u(, 1, 2)
numbers of quarks and leptons we
all particles are shown in their left-
They concern properties within each family of par-
ticles (Fig. 3). Why are there three unrelated gauge
forces? Why is the strong interaction strong? Why
are all electric charges quantized in the same unit?
What physics guarantees the seemingly miraculous
anomaly cancellation? What physics explains the
quantum numbers of quarks and leptons we see (Ta-
ble 1)? Is there a unified description of all forces?
Why is mw < MPIanck? (Hierarchy Problem.)
Recently, we added many questions from the
heaven (Fig. 5). What is Dark Matter? What is Dark
Energy? Why are we at the special moment when the
energy densities of Dark Matter and Dark Energy are
the same within a factor of two? ("Why now?" prob-
lem.) What exactly was the Big Bang? Why is the
Universe so big? (Flatness problem, horizon prob-
lem.) How were galaxies and stars (and eventually
If there are questions from the heaven, there
are also questions from the hell. To the best of
the collective knowledge of Homo sapiens, we live
at the bottom of a strange potential with a wine
bottle shape: that's the hell we are in (Fig. 6). Be-
cause of this potential, the Bose Einstein condensate
(BEC) of the Higgs boson is supposed to be present
in our Universe, and we are swimming in this BEC.
What is this Higgs boson thing? Why does it have
this strange potential with a negative mass-squared?
Why is there only one scalar particle in the Standard
Model, designed to do its most mysterious part? Is
it elementary or composite? Is it really condensed in
We do not have the right to expect that any of
these questions can be answered within our lifetime
(or ever). Nonetheless there is a good potential for us
to answer some or many of them. How exactly do we
do it? I will refer to Supersymmetry as an example
many times in my talk, but I expect similar stories
(large angle MSW)
Here’s what’s next.
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Murayama, Hitoshi. Outlook: The Next Twenty Years, article, December 7, 2003; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc934465/m1/3/: accessed August 15, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.