Lepton Photon 2001 Concluding Remarks

9 Pages·0.22 MB·English

by  Nicola Cabibbo

For Publisher’s use
CONCLUDING REMARKS
NICOLA CABIBBO
Dipartimento di Fisica, Universit di Roma - La Sapienza
INFN, Sezione di Roma
2
E-mail: [email protected]
0
0
2
Importantnewresultshavebeenpresentedatthisconference. ThedirectviolationofCP inK0→π+π

n hasbeenfirmlyestablishedintwoindependent experiments,NA48atCERNandKTeVatFermilab.
a Both Babar at SLAC and Belle at KeK have determined the CP violation in B0−B¯0 oscillations
d d
J through the study of the golden KS +Ψ decay mode. The observed CP violation agrees with the

1 expectations of the Standard model, based on the quark-mixing phenomenon. The first results of
2 theSudburyNeutrinoObservatory,SNO,suggestthatthelong-lastingsolarneutrinopuzzlehasbeen
finallysolvedintermsofneutrinooscillations. Resultsappearedaftertheconferencewhichmodifythe

2 theoretical prediction of the muon anomaly. This new result, if confirmed, would drastically reduce
v thesignificanceofthediscrepancybetweenthetheoreticallyexpectedvalueforthemuonanomalyand
7 therecentressultsoftheBrookhavenexperiment.
4
1 1 Introduction the cross section for charged current events,
1
e → ν, is many orders of magnitude smaller
0
2 than that for neutral current events, e → e,
0 One of the pleasures of this conference has dominated by e.m. interactions; at high Q2
/ been the chance to meet Alberto Sirlin after
h thetwocrosssectionsinchcloserandbecome
p many years. He reminded me of a recipe for proportional, as predicted by the standard
- theperfectclosinglectureIofferedhimmany
p model.
e (30+) years ago: “You have to mention ev- The Hera groups have presented a de-
h erybody who gave a talk!”
tailed determination of the scaling violation
:
v I am glad to have the recipe back after in deep inelastic scattering, allowing an ex-
i such a long time, but I will not be able to
X tensive check on the predictions obtained
follow it. This meeting is rich with impor-
r fromperturbative QCD,and anaccuratede-
a tant results, among which two new examples
termination of α (M ). With the advent of
s Z
of CP violation, the possible solution of the
more accurate (NNLO) calculations the new
solarneutrinopuzzleintermsofneutrinoos-
experimentalresultswillallowa1%precision
cillationsandapossiblediscrepancybetween
in this important parameter.
therecentmeasurementofthemuonanomaly
and theoretical predictions. I will concen-
trate my attention on these subjects.
2 CP Violation
The discussion of these very hot argu-
ments should not however make us forget
2.1 Quark mixing and CP Violation
manyotherexcellentresultspresentedatthe
conference; the field is indeed progressing on The charged-current weak interactions of
a very wide front. hadrons are described by the unitary
Among the many experimental results matrix1,2 V (V†V = 1). With only two
presentedattheconferenceIwasparticularly families, e.g. in a world without beauty (or
impressed by those obtained at Hera by the t quarks), V can always be reduced to a real
ZEUS and H1 collaborations, which graph- form, so that CP is necessarily conserved.
ically demonstrate the unification of weak With three families the matrix V canbe
and electromagnetic interactions: at low Q2 expressed in terms of four parameters:
For Publisher’s use
The form of the unitarity triangle can
a be determined by measurements of CP con-
r +ih 1-r -ih serving quantities. The oscillation of B0
d
mesonsaredominatedbygraphswithvirtual
g b
top quarks, so that the mass difference ∆m
d
1
is proportional to |1 − ρ − iη|2, the length
Figure2. TheUnitaritytriangleinthe ρ–η plane. squared of one of the upper sides of the tri-
angle. The length of the other side, |ρ+iη|,
canbeextractedfromadeterminationofV ,
ub
e.g from a determination of the rates of the
(cid:12) (cid:12)
(cid:12)Vud Vus Vub(cid:12) forbidden b → u leptonic transitions. These
(cid:12) (cid:12)
V=(cid:12)Vcd Vcs Vcb(cid:12)≈ determinations point to a non-flat triangle,
(cid:12) (cid:12)
(cid:12)Vtd Vts Vtb(cid:12) i.e. tothepresenceofacertainamountofCP
(cid:12)(cid:12) 1−λ2/2 λ Aλ3(ρ−iη)(cid:12)(cid:12) violation. Asafirstcheckthevaluesofρ,ηso
(cid:12)(cid:12) −λ 1−λ2/2 Aλ2 (cid:12)(cid:12)(1) obtained agree well with the observed value
(cid:12)(cid:12)Aλ3(1−ρ−iη) −Aλ2 1 (cid:12)(cid:12) of the CP violating ǫ parameter in K0−K¯0
mixing. These different constraints on ρ and
where I have used the Wolfenstein 3 η are displayed in figure 1, and lead to the
parametrization. Anon-vanishingvalueforη following estimates for ρ and η:
leadstotheviolationofCP symmetry. With
three quarks CP conservation, η = 0, is an
ρ=0.224±0.038, η =0.317±0.040 (5)
exceptional case; CP violation is the norm,
obtained for any non-zero value of η. What is perhaps more relevant is the fitted
Two of the parameters, λ and A are value for sin(2β),
knownwithgoodprecisions: λ=sinθ,where
θ is my original mixing angle, is determined
sin(2β)=0.698±0.066, (6)
by K decays,
l3
since this parameter is directly accessible
λ=sinθ =0.2237±0.0033 (2) through a study of CP violation in the
“golden decay mode” 5 of B0 mesons,
The rates of the allowedB decayslead a
determination of the A parameter. From the
analysis by Ciuchini et al. 4 we have: (B0 orB¯0)→K +Ψ (7)
d d S
Aλ2 =V =(41.0±1.6)×10−3. (3) In his presentationto this conference, C.
cb
Sachrajda has emphasized the central role of
The problem of determining the two re- Lattice QCD simulations in the determina-
maining parameters, ρ and η, is best seen in tions of the CKM parameters. Lattice QCD
the light of the unitarity relation was used for evaluating the B parameter for
K mesons, needed in the prediction of ǫ in
V V∗ +V V∗ +V V∗ =0 (4)
ud ub cd cb td tb
terms of ρ and η, and again for determining
which can be represented as a triangular re- thedecayandmixingparametersf andB
B B
lation in the complex plane. The unitar- for both the B and B mesons, parameters
d s
ity relation is automatically satisfied in the whichareneededforthedeterminationofthe
parametrizationof Eq. (1), where it reduces, two mass differences ∆m and ∆m . The
d s
uptotermsO(λ2),tothetriangleoffigure2. present simulations are executed within the
Sincetheareaoftheunitaritytriangleisη/2, quenched approximation, due to the limited
a non-flat triangle implies CP violation. computer power available today, while more
For Publisher’s use
1
_ D m
h d
0.8 D m/D m
s d
e
0.6
K
|Vub|
0.4
|Vcb|
0.2
0
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
_
r
Figure1. Constraintsonρ,η arisingfromVub,ǫ—theCP violatingparameterinK0−K¯0 mixing,andthe
Bd0−B¯d0 mixingparameter∆md.
accuratesimulationswillbepossiblewiththe the decays of Eq. (7) can be directly inter-
advent of teraflop class computers. pretedasameasurementoftheβ angleinthe
unitarity triangle of figure 2.
The situation in B0−B¯0 mixing is very
d d
2.2 New results on CP violation in B0 differentfromthatinK0−K¯0 mixing,which
decays
is dominated by a CP conserving diagram,
CP violation arising from a second smaller
Results on CP violation in the “golden
diagram. Contrary to B0 case, obtaining
mode”ofEq. (7)havebeenpresentedatthis d
information on the mixing matrix from the
conference both by the Babar experiment at
measurement of CP violation in K0 mixing
SLACandtheBelleexperimentatKeK.The
(theǫparameter)requiresacomplextheoret-
results are in reasonable agreement among
ical analysis and one must, as noted above,
themselves and lead to a value of sin(2β)
recurtolatticeQCDsimulationstoobtainan
which is in good agreement with the predic-
estimate of one of the required parameters.
tion of Eq. (6), a remarkableconfirmationof
The values of sin(2β) presented here by
thehypothesisthatCP violationphenomena
the two experimental groups6,7 are:
arisefromcomplexelementsoftheVmatrix.
The “golden” characterof B0 →K +Ψ de-
d S
rivesfromthefactthatthefinalstateisaCP sin(2β)=0.59±0.14 ±0.05 (Babar)
stat syst
eigenstate,andthatthisdecaymodeisdomi-
sin(2β)=0.99±0.14 ±0.06 (Belle)
stat syst
natedbyaCP conservingtreediagram. Any
(8)
CP violation observedin this mode must, to
an excellent approximation, be attributed to These are impressive results: each of them
B0−B¯0 mixing. by itself establishes the existence of CP vio-
d d
The interpretation of CP violation in lationinB0decaystomanyσ’s. Itisremark-
B0 − B¯0 mixing is uniquely simple, since able that two rather different experiments at
d d
this mixingisdominatedbyasinglediagram different accelerators and in different Labo-
whose phase is easily seen to be exp(2iβ). ratories were able to obtain results of com-
The measurement of CP violation effects in parable accuracy within a few days of each
For Publisher’s use
other. problem is that the direct violation of CP
Threepreviousmeasurementsofsin(2β), in K0 → ππ decays involves “penguin di-
obtainedbyCDFatFermilab8,andbyAleph agrams” which are at present very hard to
and Opal at CERN9, have larger errors but evaluate in Lattice QCD. Progress is ex-
are generally compatible with the new re- pected in this direction with the advent on
sults,whichhoweversupersedeearlierprelim- the one side of new high-performance paral-
inaryresultsbythesamegroups. Combining lel computers and on the other of new algo-
the five extant results Ahmed Alia obtains rithmsforthesimulationoflow-massquarks.
the “world average”
3 Neutrino oscillation: the Solar
sin(2β)=0.79±0.12, (9) neutrino puzzle solved?
in excellent agreement with the theoretical
The solar neutrino puzzle has been with us
prediction in Eq. (6).
foroverthirty years,since the Davis chlorine
experiment 12 detected only about a third of
2.3 Direct CP Violation in K0 →ππ;
the neutrinos expected on the basis of the
ǫ′/ǫ
current solar model 13.
Twoexperimentalgroups,NA4810 atCERN Thedeficitofsolarneutrinoshasoverthe
andKTeV11atFermilab,havepresentednew yearsbeenconfirmedbytheKamiokandeand
determinations of the direct violation of CP Super-Kamiokande water detectors, and by
in the decays K0 → π+π−, K0 → π0π0, the gallium experiments, GALLEX, SAGE
through a measurement of Re(ǫ′/ǫ): and GNO. At the same time the solar model
hasbeenrefined,andtightenedwiththehelp
of data on heliosismography, so that we can
Re(ǫ′/ǫ)=(15.3±2.6)10−4 NA48
exclude that the neutrino deficit can find its
Re(ǫ′/ǫ)=(20.7±2.8)10−4 KTeV (10) explanation in some modification of the so-
lar model itself. We can refer the reader to
The two new results are in good agreement,
therecentreview15byBahcall,Pinsonneault
and each of them is many σ’s away from
Re(ǫ′/ǫ) = 0, so that the presence of direct and Basu.
CP violations in K0 decays is firmly estab- Already in 1968 Bruno Pontecorvo 14
proposed that a deficit in solar neutrinos
lished. The new results are in rough agree-
could signal the presence of neutrino oscilla-
ment with the previous result by NA31 at
tions. Animportanttheoreticaldevelopment
CERN and with that obtained by he E731
was the realization that the coherent inter-
experiment at Fermilab (which was however
compatible with ǫ′ =0). action with the solar matter can modify the
neutrinooscillations16,andthatthiscangive
The new world averageis
riseto resonanttransformationbetweenneu-
Re(ǫ′/ǫ)=(17.2±1.8)10−4 (11) trino species evenfor small mixing angles 17.
The coeherent interaction of solar neutrinos
This is in general agreement with the theo-
with the bulk matter of earth could give rise
reticalevaluations,whicharehowevernotex-
to day-night effects which could be explored
cessively precise. They are normally quoted
as “from a few 10−4 to ≈ 2 ×10−3”. The by real-time detectors such as Kamland or
Borexino.
a I am grateful to dr. Ali for providing this result. Many questions remained open: are os-
Hecommented: “thechisquareofthefitis5.2tobe
cillations real? are the oscillations confined
compared with the expected χ = 4. The chi-square
isnotgreatbutacceptable.” totheknownneutrinoflavours,ordotheyin-
For Publisher’s use
volve also new flavours (called sterile neutri- In the next few years we expect impor-
nos) which do not partake of neutral current tantresultsfrombothSuperKamiokandeand
interactions, and do not therefore contribute SNO. Two new experiments will give impor-
to the Z0 width? tant contributions to the unravelling of the
Results obtained at the Sudbury Neu- solar neutrino problem:
trinoObservatory(SNO)18,presentedatthis
• KamLand will study oscillations in re-
conference, seem to give a positive answer to
actor neutrinos with a sensitivity suffi-
thistwoquestions: Thesolarneutrinoswhich
cient to confirm or exclude the — now
arriveatthe Earthbehaveasamixture ofν
e favoured—LMsolutionforneutrinoos-
and other active neutrinos, i.e. ν and ν .
µ τ cillations.
The principle of the SNO experiment is
to compare the rate of charged current in- • Borexino will be able to observe in real
versebeta decayevents,whichcanonlyarise timethefluxofthelow-energyBe7 solar
fromν ’s,andofneutrino-electronscattering neutrinos. Thiswillallowrefinedstudies
e
events, to which also ν ’s and ν ’s can con- of day/night and seasonal effects.
µ τ
tribute. The ratio of the two type of events, The new SNO data favour 20,21 large
CC νe mixing angle oscillation solutions, which
∝ (12)
ES νe+0.14(νµ+ντ) opens the way to the possibility of CP and
can be used to deduce the total number of T violation in neutrino oscillations:
neutrinos, which can than be comparedwith
the solar model prediction. The SNO collab-
CP :(ν →ν )↔(ν¯ →ν¯ )
1 2 1 2
oration has obtained an accurate determina-
T :(ν →ν )↔(ν →ν )
1 2 2 1
tion of the CC rate, while their determina-
tion of the ES rate is not accurate enough Disappearenceexperiments(ν1 →ν1)cannot
to establishthe existence,in the solarflux at display CP or T violations
the Earth, of a fraction of ν and ν . They ExploringCP orT violationsrequiressu-
µ τ
canhoweverusethedeterminationoftheES perbeams,orbetteradedicatedneutrinofac-
rateobtained19 atSuper-Kamiokandewhich tory, which is also the first step for a muon
hastherequiredprecision. Thetwomeasure- collider. Both possibilities have been dis-
mentsaremainlysensitivetoneutrinosinthe cussed during this conference.
same energy band, the B8 neutrinos, so that I cannot resist quoting from a paper I
their combination is meaningful. The neu- wrote in 1978 22:
trino fluxes determined through CC and ES “maximal neutrino mixing requires CP
eventsdifferbymorethanthreestandardde- violation”
viations,thus givingastrongsupportforthe By maximal I mean that all matrix elements
existence of neutrino oscillations: of the lepton mixing matrix VL should have
equal size.
ΦES −ΦCC =(0.57±0.17)106cm−2s−1
S−K SNO Since VL is unitary, the requirement of
(13)
maximal mixing has essentially a unique so-
The two measurements, together with Eq.
lution which is necessarily complex:
(12), determine the total flux of B8 neutri-
nos, (cid:12)(cid:12)1 x x2(cid:12)(cid:12)
Φ=(5.44±0.99)106cm−2s−1, (14) VL =(cid:12)(cid:12)x x2 1(cid:12)(cid:12); x=exp(2πi)
(cid:12) (cid:12) 3
(cid:12)x2 1 x(cid:12)
whichisinexcellentagreementwiththesolar
model predictions. The solar neutrino gap We are probably far from this solution,
seems to have closed. but perhaps not very far.
For Publisher’s use
4 The muon anomaly: signal for and diagrams which include virtual hadrons,
new physics? further divided in α2 and α3 diagrams
whichinclude hadroncorrectionsto the pho-
James Miller presented here the recent re- ton propagator (PP), and diagrams with
sults of the Brookhaven measurement 23 of hadronic light by light (LL) subdiagrams.
the muon magnetic anomaly. The new world These diagrams are the main sources of the
average, theoretical error,
aExp =(1165920.3±1.5)×10−9 (15) PP; α2 6924(62) ×10−11 (21)
µ
disagrees with the theoretical prediction 24 PP; α3 −100(6)×10−11 (22)
by nearly three standard deviations. LL; α3 −85(25) ×10−11 (23)
aTh =(1165915.96±.67)×10−9 (16) The numbers reported in eqs. (19 – 23) are
µ
thoseusedbytheBrookhavencollaboratinin
aExp−aTh =(4.3±1.6)×10−9 (17)
µ µ
their analysis.
The Brookhaven collaboration expects to be The hadron corrections to the photon
able to decrease the experimental error by propagator can be related to the total cross
nearly a factor three in the near future. Al- section for hadron production in electron
ready in its present state the discrepancy positron collisions 25; their contribution to
seems serious and has stimulated a multi- the muon anomaly can then be expressed as
tudeoftheoreticalpaperswhichexaminedif- an integral, with a suitable kernel, over the
ferent possible implications of this discrep- crosssectionfore+e− →hadrons. Themost
ancy,whichwouldclearlybe asignalfornew importantpartofthiscontributionandofits
physics. errorarisesfromthelowenergy(≤1GeV)re-
The interesting aspect is that the dis- gion. As an alternative to low energy e+e−
crepancy is relatively large; by comparison data one canuse, via the CVC relation,data
the contribution to the muon anomaly of on the τ decay into hadrons, which are at
electroweak effects — diagrams with virtual present more accurate 26. A number of eval-
Z0,W± bosons contribute a correction uations of the hadronic photon propagator
contribution to the muon anomaly have ap-
δEWa =(1.51±0.04)×10−9 (18)
µ pearedinrecenttimes,withslightlydifferent
In order to explain a discrepancy of (4.3± results27 andslightlydifferentevaluationsof
1.6)×10−9onewouldneednewphysicsatrel- the error.
atively low energies, in other words this dis- Since the hadron correction to the pho-
crepancylooksasexcellentnewsfortheforth- ton propagator is safely anchored to experi-
coming LHC experiments. It is also clear mentaldata one+e− collisionsandτ decays,
that in view of the importance of a possi- the error on this contribution to the muon
blediscrepancyboththeexperimentalanaly- anomaly will improve in the next few years.
sisandthe theoreticalcomputationsmustbe Particularly promising is the advent of the
submitted to to the most careful scrutiny. KLOE experiment at the DAΦNE φ factory,
The theoretical prediction of the muon whichshouldprovideanewstandardofaccu-
anomaly is the sum of diagrams with vir- racyfore+e− crosssectionsinthelowenergy
tualleptons,photonsandintermediatevector region.
bosons, The situation of the light by light (LL)
hadronic contribution is very different, as we
QED 116584706(3) ×10−11 (19)
have not found in this case a way to evade
EW 151(4)×10−11 (20) thecomplexitiesofhadronphysicsbyrelating
For Publisher’s use
this contribution to other measurable phe- periment, the hadronic light by light contri-
nomena. Waiting for a frontal attack on this butions must be carefully re-evaluated. The
contributionusinglatticeQCD(noteasy)we forthcoming measurements of hadron pro-
mustbesatisfiedwithmodelswhoseaccuracy duction in low energy electron-positron col-
is difficult to estimate. lisionsshouldleadtoanimprovedevaluation
The current evaluations of the hadronic ofthecontributionofhadroniccorrectionsto
light by light contributions to the muon the photon propagator.
anomaly28,29arebasedonmodelsofthelight
pseudoscalarmesonsandtheirinteractionsat
5 We are not alone!
lowenergy-chiralperturbationtheoryorthe
extended Nambu - Jona Lasinio model. The
While all this has being going on, cosmolo-
dominanthadronicLLcontributionturnsout
gists ...
to be the one mediated by a single interme-
We heard in the talks by Halzen and
diate neutral pion.
Turner of the exciting progress our neigh-
After the LP01 conference was con-
bours are making in Cosmology and Astro-
cluded, a new calculation of the π0 contri-
physics. With the recent results on the cos-
bution 30,31 to the muon anomaly reached a
mic background anisotropy cosmologists are
verysuprisingconclusion: whilepreviouscal-
confirming their own Standard Model.
culations had found a negative sign, the new
The new results on the cosmic back-
result, recently confirmed by an independent
ground arise from a serendipitous use of the
computation 32, found a positive sign. The
antartic winds which circulate around the
authors of the two complete evaluations of
South Pole: a balloon released from an an-
the LL contributions 28,29 have been able to
tartic station comes back close to the same
identify the origin of what they now see as a
spot in obout a month. A balloon circling
sign error in the previous computations and
the South Pole can be very competitive with
have presented new evaluations for the over-
asatellite: thelaunchisbyfarlessexpensive,
all LL contributions, which are respectively
and the payload does not need to meet the
33,34 (89±16)×10−11and(83±32)×10−11.
high standards and associated cost in both
The effect of this sign change is a reduction
moneyandtimethataspacelaunchrequires.
ofthediscrepancytolessthan2standardde-
In the Boomerang flights the cosmic
viations.
background has been studied with unprece-
Quite apart from the question of sign of
dented resolution. The angular resolution of
the π0 contribution, which only arose after
the recentdata correspondsto sphericalhar-
the conference,wemustnote adetailedcriti-
monics of ≈ 1000. In this range three peaks
cism 35 by K. Melnikov,who argues that the
are evident in the power spectrum, which fit
contribution of quark-looplight by light dia-
verywelltheexpectationforaBig-Banguni-
grams has been underestimated in ref. 28,29
verse at Ω = 1, i.e. a flat universe, whose
In referring the interested reader to Mel-
energy density is much larger than the “ob-
nikov’spaper for the details ofhis argument,
served” baryon density which would corre-
I note thatthis wouldfurtherreduce the dis-
spond to Ω ≈ 0.05. This offers futher ev-
crepancybetweentheoreticalevaluationsand
idence for the conclusion that most of the
the experimental result. Although the au-
matterintheuniverseis“darkmatter”,most
thors of ref. 29 do not agree with this argu-
probably“colddarkmatter”,i.e. mattercon-
ment,itisclearthat,inordertocalculatethe
stituted of relatively heavy particles, which
muon anomaly with a precision comparable
have decoupled from “normal” matter early
with that expected from the Brookhavenex-
in the history of the universe.
For Publisher’s use
Whileitisclearlythetaskofastronomers and Borexino.
and cosmologist to ascertain the geometry The new results by SNO reinforce the
and history of the universe, the task of at- proposal that neutrino oscillations are char-
temptingthedetectionoftheseslowparticles acterized by large mixing angles, and this
coastingalonginthepresentuniversefallsto opens up a very exciting possibility of de-
the high energy community. Many experi- tecting CP violation effects in neutrino os-
ments are now underway for the detection of cillations. The detection of these effects will
the weak interacting cold matter, and might howeverrequirenewneutrinobeamfacilities,
bear fruit in the coming years. which have been discussed during LP01. A
first attempt could be carried out with su-
perbeamswhilemoredetailedstudieswillre-
6 Conclusions and
quiretheavailabilityoffull—flegdedneutrino
acknowledgements
factories.
Thesuccessofthisconferenceiscertainly
This conference has been enlivened by many
the merit of the many research groups who
exciting results. Will the next one be even
have contributed important new results, and
better? Itisatallorder,butbeautifulthings
of the many physicists who have contributed
are brewing.
wellpreparedandwelldocumentedpresenta-
After decadesinwhichCP violationwas
tions of the new data, but LP01 would not
established in a single process, the K0−K¯0
have succeeded without the efforts of the or-
oscillations, we now have two more well es-
ganizers and of the many young people who
tablished examples, the first in B0 −B¯0 os-
have devoted so much time and efforts to its
cillationsandthe secondadirectviolationin
success.
K0 → ππ. The first is important for the
I am particularly grateful to Juliet Lee
light it sheds on quark mixing and the Stan-
Franzini and Paolo Franzini, who invited me
dard Model in general, while the measure-
to give these concluding remarks to a very
ment of ǫ′/ǫ has a very special impact be-
exciting conference whch has turned out to
cause, apart from it being in general agree-
be a realturning point in the kind of physics
ment with the still imprecise expectations of
I have been working on for many years.
theStandardModel,itdefinitelyexcludesthe
To everybody who participated in the
“Superweak” models of CP violation.
conference I would like to present my best
We can look forward to new results on
wishesthatwemayallbeworkingveryhard,
CP violation: BabarandBelleshouldbeable
and be ready to surprise each other when
to establish new examples of direct violation
we meet in 2003 for the next Lepton Photon
in B decays and the KLOE experiment at
Conference.
DAΦNE should offer a determination of ǫ′/ǫ
whichislogicallyindependentfromthosepre-
sented by the NA48 and KTeV experiments. References
The other very exciting development
comes fro the SNO results which corrobo- 1. N. Cabibbo, Phys. Rev. Lett. 10, 531
rate the conclusion that the solar neutrino (1963)
puzzle will find its solution in neutrino os- 2. M. Kobayashi and T. Maskawa, Prog.
cillations. Here we expect important re- Theor. Phys. 49, 652 (1973).
sults in the near future from both SNO 3. L. Wolfenstein, Phys. Rev. Lett. 51,
andSuper-Kamiokande,butalsofromexper- 1945 (1983).
iments which are now approaching the data- 4. M. Ciuchini, G. D’Agostini, E. Franco,
taking phase, in the first instance Kamland V. Lubicz, G. Martinelli, F. Parodi, P.
For Publisher’s use
Roudeau and A. Stocchi JHEP 0107, 23. H. N. Brown et al (Muon g-2 collabora-
013 (2001). tion), Phys. Rev. Lett. 86, 2227 (2001).
5. I.Y. Bigi, A.I. Sanda Nucl.Phys. B 281, 24. A. Czarnecki and W. J. Marciano,Phys.
41 (1987). Rev. D 64, 013014 (2001).
6. B. Aubert, et al (The BABAR Collabo- 25. N. Cabibbo and R. Gatto, Phys. Rev.
ration), Phys. Rev. Lett. 86, 2515-2522 124, 1577 (1961)
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