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WHAT LIES AHEAD?

. P ossz ble fzLture direction ofBDK

A. I. Sanda

Department of Physics, Nagoya University Chikusa ku Nagoya 464-Ol, Japan

1 Introduction Physics is a discipline which attemps to understand laws of nature through experiments. Findings of experiments are put into a theoretical framework, which, in turn, leads to further predictions of experimental results. Every at one ' physicist, stage or another, have been impressed with the beauty ofnature displayed in its theoretical framework. Often, one is tempted to use the mathematical beauty as the criterion for constructing theories. While there is nothing wrong with this approach, its over emphasis leads to developement of mathematicians, not physicists. This is a world wide problem. I think, however, it is paticularly severe in Japan. In the future, there should be an effort, at the national level, to develope "physicists" by encouraging more students to attend this type of workshops. The program should also be constructed with this goal in mind.

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2 What lies ahead2

Here, I wish to review physics topics which might be very relevant in the next 10 to 20 years. Developement of physics depends on new experimental results. We thus list existing and anticipated experimental facilities.

Existing facilities and their main activities

TEVATROIV FAIAL topsearchetc.

SPS CERIV neutrino physics

LEP' CE]RIV precisioncheck

of the standard model ' CESR CORAI ,E]LL B de cays ARGUS DESY Bdecays SLC SLAC B,-B,mixing? HZ!]RA DESY deep inelastic scattering KAMIOKAIVDE KAMIOKA udetection (1)

Anticipated facilities and their expected results

SSC SSCL higgs, technicolor?, SUSY? Kfactory FRASCATI CPviotatingKdecays, rare decays, eta decays, etc. B factory KEK origin of CP violation, rare B decays, etc, SUPERKAMJOKA KAMJOKA vmass, mixing, etc. (2) Now, what are the realistic expectation for the next 20 years?

SSC: At the present rate of funding, there is a good chance that SSC will be delayed for a few years. If so, it will be a 15 year project rather than a 10 year project.

B factory: There is good chance that the KEK B factory will be operating before the end of the 90s.

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rl"he K faetory; Frascati K fa£ tory may go in operation in a few years.

Super Kamioka: will be in operation in 1995.

JLC: It is too early to state when it may come in operation.

So, B and K factories, as well as several neutrino laboratories will be in operation during the next 5 to 10 years. Thus, study of CP vio]ation, quark masses, rare decays both in B and K decays should yield exciting results. Same can be said for study of neutrino mixing and neutrino mass problems. Information on Higgs particle, SUSY, GUTS, etc. to come in during the next 10-20 years.

3 Quark and lepton masses

In this workshop, there have been many talks on quark mass matricies. The fact that quark masses and the origin of CP violation are the two things that are least understood in the standard model may not be an accident. They may both originate from the same dynamics at the GUT scale. Thus, understanding the quark mass matrix, as well as CP violation, may lead to a better understanding of the GUT physics. We might start looking at the quark and lepton mass matricies in various GUT models. For exainple, the 27 representation of Eb looks paticularly attractive:

H,Ei.', O [2 71 = [(:) uf, df, D,Ci Dt, N, (3) ,, (Z),eCuC,()i(Hrr-)],,

where i runs over the 3 color indecies, and L stands for the left handed helicity. Another noteworthy feature of the GUT theories is the relationship be- tween quark and lepton masses. For example, in SU(5) GUT,

md=mei ms=mpi mb == rnr (4)

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which can be traced to the SU(4) symmetry after SU(5) is brocken with oooov

< ip5 >., (5)

These mass relations hold at the GUT scale, and the renormalization group equation must be used to infere its implications at a £ cessible energies. At the electroweak energy sca}e (Mw), it predicts

md m, mb 5 =-., = 'Vs (6) IE I;

Whi}e this is excellent for the third generation, it is not very desiable for the first two generations. To remedy this situation, Georgi and Jarlskog [1] introduced 45 Higgs boson ip2b which also breaks SU(5). It satisfies the fbllowing properties:

5 ip:b=mip2a; 2ip25=o. (7) a=1

These properties require: 100 oooooo OIO

< dig5 >., O O 1 ' (8) ooo -3 Ooo ' ooo

where the the equality of the first gonal elements follows from the SU(3)cot.. symmetry, the vanishing of the 1ast diagonal element follows from

antisymmetry, and finally, -3 fdllows from the trace condition. The ammus- ing point is that the vacuum expectation value of ¢ g5 }eads to:

1 Mr=Mb M"=3Ms Me=sMd (9) or

'-gliit'･ llii'i=9iilt'i illl (io)

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These are in fairly good agreement with experiments. Progress in physics often comes with this type of trial aRd error procee- dure. This is an exainple of a novel approach which attempts to understand the physics of GUT scale using Iow energy experimental data, Recently, this has been extended to a program which derives the mass matricies of up, and down quarks, as well as that ef charged leptons[2]. They start with three mass matricies:

O Fei¢ O O F O U=oco COB Fe'idi E O F -3EJ O OBAiD= O OD;E= O O D. (11) They show that A, ..., F can, in generaJ, be chosen real. These 7 pa- rameters and the ratio of vacuum expectation value < ipl'5 > 1 < ips > aie determinedby the masses of e, ps, T, c, b, IT!Zbl, ;:t', II'Zdl･ Then the other parameters

! m,, md,m,, l;l {,,Zb1,e,,e, (12) are determeined. They are in good agreement with experimental data, and they predict mt=176-190GeVl (13) I strongly encourage approaches of this type. Eventually some one wil} stumble across some scheme which is the key to understanding the quark mass problem. This may also fix the GUT theory and solve the CP problem.

4 Chiral symetry

Low energy pion dynamics is governed by current algebra, or chiral pertur- bation theory. This approa,ch is not often applicable to K meson decays. Here, the problem of SU(3) breaking as well as the large K meson mass make the chiral purterbation approach less reliable. I believe that a lagrangian whic h includes pseudoscalar, scalar, vector, and axial vector mesons can be constructed such that it is consistent with all low energy phenomena. This will enab}e us to compute al1 hadronic matrix elements of K decays. So, in the future, K decay may yield much more precise va}ues of the KM matrix elements,

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5 Heavy quark decays and chiral symmetry

In the leptonic decays ofB meson, we can choose the lepton energy so that the invariant mass of the hadrons in the final state is small (S IGeV). Then we can use chiral lagrangian mentioned above to compute the hadronic matrix elements. Thus we should be able to mate the heavy quark theory with chiral perturbation theory.

6 Baryon asymmetry of the universe

The bigbang cosmology creats matter and antimatter equally. Yet, there is no antimatter in the universe. The most atractive feature of GUT is that this

matter-antimatter asymmetry can be explained by introducing CP violation at the GUT scale. This leads to an interesting problem. We should be able to understand the re}ationship between the baryon asymmetry and the CP violation observed in K decays. This is the ultimate puzzle which motivates construction of the B factory. As well defined as it seems, there is a hitch. Namely, the sphereon solution to the electroweak theory can wash out the baryon asymmetry created at the GUT sc&le. Thus, inorder to solve the baryon aymmetry problem, we must understand the sphereon dynamics.'This is a nonperturbative dynamics and it is very difficult. I hope some one will bring the sphereon problem to its conclusion so that further progress on the baryon asymmetry can be made.

7 Summary

KEK has chosen the B factory as the next project. It is very important that the project has a ful} theoretical support. At the same time, it is an opertunity to understand the real origin of CP violtion. This will certainly lead us to the physics beyond the standard model. BDK should design its activities so that it can stimulate the physics community along this line, and also educate students in doing real physics. I only covered few topics which should be of great interest for the next 10 r-v 20 years. I am encouraged that there is already the BDK group which attempts to hold regular workshops on this type of physics.

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One last suggestion: Perhaps the name should be changed to BDKL group to include leptons.

References

[1] H. Georgi, and C. Jarlskog Phys. Lett. B86 297 (1979)

[2] S. Dimopoulos, L. Ha[Ll, S, Raby Ohio State DOE-ER-O1545-567 (1991).

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