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Heavy Quarks
In this section we will cover the followin to!ics"
# $he %har& Quark
# $he 'otto& Quark
# $he (atio (
# $he $o! Quark
# )ny *ore Quarks+
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The Charm Quark
! to 1./ there were 3 uarks u2 dand s
)t S)%4SPE)( e+eStorae (in5
e+ e
7 hadronse+ e7 + e+ e7 e+ e
8ery narrowresonance
4s&all width 5 with a lare
&ass of 391 :e8;c,
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J/Particle
)lso at 'rookhaven< 30 :e8!roton
synchrotron
! 'e7 e+ e anythin
=ne rou! called it - the other J< now known as J/
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J/Width
)ctual widths are s&aller than o>served >ecause of&easure&ent errors and the s!read of the >ea& enery
$he true width ? 0906/ *e8;c,< verynarrow
width @ lifeti&e ? c9f9 Et?
I&!lies lon lifeti&e < soðin inhi>itsthe decay9 Aould
eB!ect soðin this heavy to decay very ra!idly to !ions
via Stron Interaction
Cew uark flavour < char&
*ass of char& uark? 19D :e8;c,
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J/Decay
$he &ost o>vious decay of the J/is a direct decay
to two char&ed &esons2 D+
and D
%har&ed &esons
'ut we now know the &ass of the Dis 19F/ :e8;c,
$he &ass of the J/is 3910 :e8;c,i9e9 less than twice the G&ass
J/ D+ D
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J/Decay
$he other !ossi>ility is a wei su!!ressed decay to !ions
$his is inhi>ited >y the 3 luon cou!lin
7 lon lifeti&e 7 narrow width
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Other States
$here is also a first eBcited state which is also narrow9
Hiher states with hiher &ass are wide as they can decay to D+ D
( nor&alised
cross section
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Charmed Hadrons
$he 4J
P
5 char&ed &esonsare"
D+ cd D cd
D0 cu D0 cu
DS+ cs DS
cs
)lso eBcited states
D!7 G etc
%har&ed >aryons"C
+ cudetc
Since the char&uantu&
nu&>er is conservedin
stron interactions2 the
!redo&inant decays are viathe weak interaction
G07 J- "+
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The #ottom Quark
In 1.// at Ker&ila> 4KC)5 saw narrowstructure in +&ass s!ectru& in &ass
reion near 10 :e8;c,in reaction
! nucleus7 + anythin
'e2 %u2 9 9 9
Carrow structure
%ontinuous >ackround
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The $%silon
Since then !recise eB!eri&ents at e+e&achines4G=(IS2 Ha&>ur2 %ES(2 %ornell CY5
!silon && *ass of >uark ? D :e8;c,
Ka&ily of ' &esonsand > >aryonsfound"
#+ &u # &d #s &s &
&ud
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The Char'e o( the & Quark
$he chare of the >uark of -eis
confir&ed >y &easurin the ratio ("
as a function of %* 4e+e5 enery
$he rates are deter&ined >y the
strenths of the E* cou!lins at
the two vertices iven >y the
chares of the !articles
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The )atio )
Su& over allcontri>utin uarks
%hare of
L @ so&e threshold
kine&atics factorsM
)s uarks co&e in 3 colours"
$he fact that the factor of 3 is necessary is very stron
evidence in su!!ort of the colour hy!othesis
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The )atio )
*lavour u d s c & t
Char'e, -., -., -., -., -., -.,
*or EC01 , 2e3have uu4 dd4 ss
5 )6 7 -8/9 + :/9 + :/9. 6 ,
*or EC01 ; 2e3have uu4 dd4 ss4 cc
5 )6 7 -8/9 + :/9 + :/9 + 8/9. 6 7
*or EC01 :: 2e3have uu4 dd4 ss4 cc4 &&
5 )6 7 -8/9 + :/9 + :/9 + 8/9 + :/9. 6 7
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The )atio )
u d s 7 ,
u d s c 7 393
u d s c > 7 39/
colour factor of 3
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The To% Quark
)fter 1.// we had"
Quarks
u c
d s >
e!tons
e
e
=>viously one&issin to! t
)lso ood theoretical
reasons for co&!lete
dou>lets
Searched in vain at e+e&achines2 PE$()2 PEP2 EP etc< rulin out any new uarks at their eneries 7 to! &ass
N D :e8;c,4half EP1 enery5
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=Hints= o( the To% Quark
In early 1..0s < !recise &easure&ents of 0decayat EP suest
that the to! &ass ? 1/0 :e8;c,
$hese involve su>tle corrections to >decay !ara&eters due to virtual to!
uark corrections
$hese ive a sliht chane to the
>decay width which de!endson the to! &ass
Kirst order
%orrection
%orrection
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The Discovery o( the To% Quark
In 1.. ru&ours that to! &ay have >een discovered at Ker&ila>
4near %hicao5
In *arch 1..D >oth %GKand G0
%olla>orations clai& < =>servation of the
$o! Quark
$hese are realAs"
A7 e
A7 A7 ?
$he sinaturesare"
e Oets eOets
e eOets Oets
Oets
$a>Oets >y reuirin
a finite decay distance$o! &ass 1/ D :e8;c,
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The Discovery o( To% Quark
G0 EB!eri&ent
%GK EB!eri&ent
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The Discovery o( To% Quark
Gata !oints
Ahat it would
look like
without to!
uarks
Esti&ated to!
uark
contri>ution
)ree&ent
>etween data
and theory for
different to!
&asses
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The To% Quark
$o! Quark %andidate
in )$)S
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@ny 0ore QuarksA
Ae have 3full enerations9 Ae only need one 4u2 d2 e2 e5 for everyday life
So if 3 why not &ore+ Since it is not understood why there are 3
enerations there is no theoretical reason why there shouldnt >e &ore
4Periodic $a>le aain+5
However2 eB!eri&ental evidence now suests only 3
In early 1..0s EP &easured the width of the >to very hih!recision9 $he >can decay into any fer&ion !airs with a co&>ined&ass less than the >&ass 4?.0 :e8;c,5
f u2 d2 s2 c2 >2 e2 2 2 e2 2
$he &ore ways the >can decay2 theshorterits lifeti&eand the larerits
width4@ ? 5
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@ny 0ore QuarksA
:eneration
1 , 3 9 9 9
u c t h 9 9 9
d s > l 9 9 9
e 9 9 9
e B 9 9 9
$he >can decay into all these
> ttsince*>R ,*t
$he >would decay into anynew neutrinos assu&in they
were &assless 4or liht
co&!ared with *>5
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Each of theuuetc
are know as !artial
widths
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The Width o( the >
Ae know how &uch each uark;le!ton !air contri>utes to >
>6 uu+ dd + ss+ cc+ &&
+ e+e+ ++ +
+ is euivalent to &easurinthe nu&>er of neutrino s!ecies er of enerations
(esult fro& EP" ut they cannot >e too
heavy or they would contri>ute too &uch &ass to the niverse 7
)stro!hysical constraint on neutrino &asses
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The Width o( the >
Gata !oints
$he red curve 4
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