고에너지 물리 특강
DESCRIPTION
고에너지 물리 특강. Lecture 1: Experimental Tools for HEP - Accelerators & Detectors - Observation of fundamental particles Lecture 2: Some recent/future HEP experiments - Belle for heavy-flavor physics and CP violation - COREA for UHECR. Experiments of High-Energy Physics. - PowerPoint PPT PresentationTRANSCRIPT
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고에너지 물리 특강Experiments of High-Energy Experiments of High-Energy
PhysicsPhysicsLecture 1: Experimental Tools for HEP
- Accelerators & Detectors - Observation of fundamental particles
Lecture 2: Some recent/future HEP experiments- Belle for heavy-flavor physics and CP violation- COREA for UHECR
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High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.) 2
theory
physicalobservables
QFT
calculate
experimentwith any necessary
approximations
Theory vs. Experiment
,L
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3High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Experimental tools Particle Accelerators
Particle interactions inside matter
Particle detectors
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4High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Particle Accelerators
“precision instruments constructed on a gigantic scale” particles are traversing ~106 km for a few seconds
while maintaining the path within ~m “modern accelerators are like great Gothic cathedrals
of mediaeval Europe…” (R. Wilson) Why accelerate?
the more energy, the deeper structure we can prober p ħ/2
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5High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Why not use high-E particles
in the cosmic ray? low flux ; energies cannot be controlled
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6High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
T = qVlimited to ~ 1 MeV voltage breakdown & discharge
Electrostatic Accelerators
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7High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
potential difference b/w the ends of drift tubes the fields oscillate, but the particles are protected (from decelerating
phase) by the metallic drift tube the distance b/w gap increases but soon saturates
an everyday proof of special relativity!
Linear Accelerator
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8High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
An example: Stanford Linear
Accelerator Center
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9High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
SLAC linear acc.
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10High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
cyclotron
Circular Accelerators
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11High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Cyclotron
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12High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Cyclotron[Ex] a cyclotron, with extraction radius R = 0.4 m & B = 1.5T fAC = ? Tmax = ? (for p)
fAC = fc = qB/2m = 22.9 MHz
Tmax = (qBR)2/2m = 17 MeV
As we increase the energy, relativity must be considered. fixed freq. cyclotron would not work for very high E synchronous acceleration is needed!
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13High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Synchrotron
Consider we already attained the desired energy (= constant)and the particle goes through a circular orbit under B
f or B (or both) should be changed synchronously with the particle velocity; hence it is called a “synchrotron”
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14High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
a “magic formula” for charged particles
Then, for v c,
and we obtain a very useful formula
B
p
3.0
(GeV)
[Ex] p = 3 GeV/c, B = 2T; R = ?
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15High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
SynchrotronIf we build a cyclotron-style machine, too much steel (and cost!) is needed…hence, a new design!
The beam particles take many turns to achieve the design energy.Q: is it possible to maintain the beam size (within the vac. chamber) for so many turns? beam stability ??
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16High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Focusing of beams
Phase stability edge focusing
Strong focusing - FODO lattice
F O D O
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17High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
focusing with quadrupole magnet
flux return steel
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18High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Collider vs. fixed target
How to derive ?
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19High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Livingston Plot
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20High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Colliders
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21High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Particle Detectors
Detector system: an overview Particle interaction inside matter
– dE/dx
– Multiple Coulomb scattering
– photon interaction inside matter Charged particle detection : Neutral particle detection : Detector system for real experiment
ppxx ,
EExx ,
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22High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
On experimental resolution
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23High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Detector System What do we want to measure in a detector system?
positionposition ; event topology, intermediate particle state momentummomentum ; need “tracking” energyenergy ; deposited in a localized place ; “calorimetry” massmass ; i.e. particle identification (PID) chargecharge ; from the curve orientation in the tracking chamber
px
Constructing (E, ) 4-vector for each particle: charged : tracking & PID => , m => E=(p2+m2) neutral : (E, , ) => is deduced by assuming m and origin
p
p
p
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24High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
How a detector system works
For colliding beam experiments
For fixed-target experiments
Pt=0.3BR
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25High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
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26High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Particle interaction inside matter
Energy loss of charged particle– Before a particle can be detected,
it must first undergo some sort of interaction in the material of a detector.
– EM interaction is the most important Energy loss as a function of travel distance
dE/dx
0.000
2.000
4.000
6.000
8.000
10.000
12.000
14.000
0.000 2.000 4.000 6.000 8.000 10.000 12.000
232
ln1
~/ vv
dxdE vs./ dxdE
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27High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
dE/dx (brief derivation) Coulomb interaction b/w incident charged particle &
another charged particle in the detector material by transverse p
TE
22
221
2
bmv
)z2(z
2m
ΔpΔE m = target mass
Then, in the Lab. frame, (t=0 @ r=b)
dtEqp T
(Jackson)
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28High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
[Ex] energy loss due to bound electrons vs. nuclei
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29High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
dE/dx (brief derivation) For dE/dx,
count the number of interacting particles in the target!
dxdbbnN e 2
min
max2
221
max
min 22
221 ln
)()(/
b
b
mv
ZZdb
b
b
mv
ZZdxdE
b
b
bmin and bmax ?
A
NZnZn A
atome
22
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30High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
bmax for dE/dx consider interaction w/ free electron
only if motion orbitalcollision Tt
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31High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
bmin for dE/dx E cannot exceed the max. allowed energy transfer
for a head-on collision
(let Z2 = 1)
2
1
23
2
421 ln
4/
eZ
mv
mv
eZndxdE e
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32High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Bethe-Bloch formula dE/dx calculation with quantum correction
2
23
2
421 2
ln4
/ I
mv
mv
eZndxdE e
I = ionization potential
For small v,
For large v,“relativistic rise”
minimum ionization
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33High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Particle ID by dE/dx
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34High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Additional tools for charged particle ID
• Time of flightvxt /
p from trackingmass
• Cherenkov radiation
p
I K p
n
c
vc
1cos
Mass (GeV)
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35High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Multiple Coulomb scattering
energy loss in Coulomb collision with nuclei is small
Note: Rutherford scattering formula
as / dd
ping-pong ball bowling ball
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36High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Multiple Coulomb scattering
In any given layer of material,the net scattering is the result ofa large # of small-angle deviations (indep. of one another)
=> “ Multiple Scattering ”
ddP
2
2
2exp
2)(
a Gaussian distribution
for details, see “Intro. to Exp. P.P.” by R. Fernow, Sec.2-7
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37High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Multiple Coulomb scattering
In a layer of thickness
deflection angle
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38High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Multiple Coulomb scattering
Ec = “critical energy”
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39High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Multiple Coulomb scattering
In practice, multiple scattering limits the precision of p
[ex] determine inside of a solenoidp
B
if no scattering, pc = BeR (Gaussian unit)
or p = BeR (SI unit)
Traversing a distance x, the angular deflection is
p
Bxx
cp
Be
R
xB
300
)(
[ p(MeV/c), x(m), B(T) ]
619
819
10106.1)GeV(
)m/s(100.3)m()C(106.1)(
pc
xTB
B
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40High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Tracking error due to multiple scattering
Compare with scat B
0
rmsscat
1
2
21
2
X
x
pv
where
why 1/2 ? consider only projection onto the plane of the trajectory
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41High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Energy loss via radiation
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42High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
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43High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Photon interactions in matter
C Pb
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44High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Pair production
In the high energy limit (E>>2me),
the mean distance a photon will travel before pair producing is
Note: Why are XP and X0 similar?=> because bremsstrahlung and pair production are simply time and space rearrangements of the same process
0)7/9(~ XX P“conversion length”
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Photon interactions in matter
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46High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Calorimetry Most calorimeters measure the ionization energy
deposited by all the charged particles in the "showers" produced as the particle is absorbed. – EM shower– Hadronic shower
The scale length– EM: radiation length, X0 (~2cm in Fe);
relevant for both bremsstrahlung & pair production
– Hadronic: mean hadronic interaction length, I (0.2m in Fe).
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47High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Scintillation detectors
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48High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
PhotoMultiplier Tube
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49High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Belle EM Calorimeter
Tower structure projected to the vicinity of IP. 30 cm long (16.2 X0),
8736 CsI(Tl) crystals (6624 in barrel). 12< < 155 (lab frame)
Inner radius – 1250 mm
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50High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
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51High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
How to detect a charged track?
E ~ 10 kV/cmcharge amplification ~ 105
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52High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Ionization and detectionsensitive medium +V
V
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53High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Multi-Wire Proportional Chamber
Charpak, 1992 Nobel physics prize
x ~ O(wire spacing)
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54High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
MWPC
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55High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Drift Chamber
in each cell, the combination of (+) and () HV wiresprovides a relatively uniform E (= V/x)in a direction to normal incdidence
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56High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
drift distance measurement
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57High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Drift Chamber
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58High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Field lines inside Drift Chamber
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59High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Precision Vertex Detection
Particles with c (charm) or b (bottom) quarks have lifetimes ~ 10-12 s
[Ex] In the Belle experiment, e+ (3.5GeV) and e (8 GeV) beams are collided and a pair of B mesons (mB = 5.28 GeV/c2) are produced.
(1) Find for each B meson?
(2) How far will it travel before it decays?
(3) spatial resolution to measure B meson decay position?
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60High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Precision Vertex Detection
To detect heavy-flavor particles (c or b), we need a position measurement of ~ 100 m resolution or better
Near the collision point, the density of particle tracks is very high
Surround the collision point with a high-resolution silicon sensors
Why silicon?
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61High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Silicon Vertex Detector To create a electron-hole pair in a semiconductor (e.g.
Si or Ge), only ~ 3 eV is needed large signals with very little energy deposition
Very thin wafer (~ 0.3 mm) is enough to achieve good signals
Conducting electrodes are implanted in separated stripes, orthogonally for p and n sides HV
n
p
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62High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
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63High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Track finding & fitting
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64High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Detector System What do we want to measure in a detector system?
positionposition ; event topology, intermediate particle state momentummomentum ; need “tracking” energyenergy ; deposited in a localized place ; “calorimetry” massmass ; i.e. particle identification (PID) chargecharge ; from the curve orientation in the tracking chamber
px
Constructing (E, ) 4-vector for each particle: charged : tracking & PID => , m => E=(p2+m2) neutral : (E, , ) => is deduced by assuming m and origin
p
p
p
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65High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
putting things together…
quiz time!
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66High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
The Belle Detector
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67High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Particle Flavor Q/|e| e –1
leptons e 0
u c t +2/3 quarks
d s b –1/3
The fundamental fermions
1st 2nd 3rdgenerations
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68High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Heavy quarks ( c, b, t )
As of 1974…
sdu
e
e
?
GIM mechanism predicted the 4-th quark
which was named “charm”
because it did some good things…
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69High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
November, 1974!
SLACB. Richter
MITS. Ting
ffee Xeep Be
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70High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
J/ - the quantum #?
Interference with a photon
same quantum # as photon
interference
After heated discussion among theorists, it was concluded that J/ is a bound state.cc
The 4-th quark was discovered!
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71High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
' : 1st radial excitation of J/
)1(/)2( SJS
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72High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
One amazing feature about J/ was its long lifetime
(J/875 keV
(150 MeV
But the partial decay width to e+e was similar to other vector (JP = 1) mesons
Lifetime of J/
keV )32.077.6()(keV )37.026.5()/(
eeeeJ
Something special about J/ hadronic decays?– OZI suppression!
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73High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
OZI suppression in J/ decays
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74High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
4 quarks & 4 leptons - are we happy?
af
Reines & Cowan (1950’s)
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75High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Leptons and their mystery
so similar?
But, then why do we not see ewhile seeing plenty of ? ee
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76High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
The 3rd charged lepton
)missing( eeeWhat could this be?
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77High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
The 3rd charged lepton
)missing( eee What could this be?
eeee
Martin Perl (1975)
??
sc
du
e
e
So, in less than a year...
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78High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Upsilon resonances
anythingPt Cu, Be, pLederman (1977)
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79High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Upsilon resonanceswith better resolutions
2mB
BBS )4(
OZI suppression -> narrow resonances
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80High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
What about the 6th quark?
bsc
du
e
e
?
Indirect evidences of “top” quark
Vtd
Vtd ARGUS (1987)
(1) B mixing
1.0)(
)(
XB
XB
(2) Kane-Peskin limit (1982)
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81High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Double pendulum as a mechanical analog of flavor-
mixing
-1.500
-1.000
-0.500
0.000
0.500
1.000
1.500
0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0
Pendulum 1
Pendulum 2
1 2
k
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82High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
The 6th quarkCDF & D0 (both at Fermilab) in 1995
How to see the top quark?
LLLbt
sc
du
''' W
t b'
W+
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83High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
How to see “top” quarks?
Xttpp
or '
qqW
bWt
or '
qqW
bWt
and
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84High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
CDF DetectorCDF Detector
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85High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
“top” quark event : one lepton + 4 jets
CDF
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86High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
“top” quark event : di-lepton + 2 jets
CDF
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87High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
Mass of top quark
CDF, PRL (1998)
Each top candidate is fit to obtain Mrec
kinematical constraints tob-jets and light-q-jets
missing transverse energy for neutrino max. likelihood fit to obtain mass
from a sample of candidate events
1.53.174
(GeV) 3.58.49.175)(
tm
world average
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88High-Energy Physics / Experimental Tools Mar.15, 2005 Youngjoon Kwon (Yonsei Univ.)
How about gauge bosons?
WWee 0Zee