stephen l. olsen seoul national university
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Stephen L. Olsen Seoul National University. From: http://luchins.com/what-were-they-thinking/ insanely-bad-science /. 2008 Nobel Physics Prize. - PowerPoint PPT PresentationTRANSCRIPT
Stephen L. OlsenSeoul National University
From: http://luchins.com/what-were-they-thinking/insanely-bad-science/
2008 Nobel Physics Prize
Kobayashi & Maskawa explained CP violation within the framework of the Standard Model, but required that the Model be extended to three doublets of quarks. These predicted, hypothetical new quarks have recently appeared in physics experiments. As late as 2001, the two particle detectors BaBar at Stanford, USA and Belle at Tsukuba, Japan, both detected CP violations independently of each other. The results were exactly as Kobayashi and Maskawa had predicted almost three decades earlier.
Kobayashi Maskawa
Thread of this talk
CP violation
three doublets of
quarks
B mesons(BaBar & Belle experiments)
Stockholm
What is it?
Why three?
Why B mesons?
CP Violations
Differences between matter & antimatterantimatter
P+
e-
P-
e+
hydrogen antihydrogenDifferent?
Dilemma
Laws of physics are very symmetric between matter & antimatter
Nature is very asymmetric between matter & antimatter
no antimatter here
Then:a“no-hair” Universematter = antimatter
Now: people
Big-Bang Cosmology
no antipeople
Only mass, electric charge & angular momentum
Where are the antipeople?
Need to study violations of “CP” symmetry
P = Parity(x,y,z) (-x,-y,-z)
Field (& rules) of footballare parity symmetric
Rules of baseball arenot parity symmetric
Parity violation in physics-a nano history-
Parity Conservation in QM
1927: Nature is Parity symmetric Laporte rule = Parity conservation
Otto Laporte1902-1971
Eugene Wigner1902-1995
1924: Atomic Wave functions are either even or odd.
Laporte rule: dipole transitions connect evenodd (& not eveneven or oddodd)
q-t puzzle
q+ p+p0
mq ≈ mp/2G.D. Rochester & C.C.Butler,Nature 160, 855 (1947)
q+
p+
cloud chamber
p has odd parity: P(p) = -p
P(q+) =+ q+
q has even parityP(t+) = -t+t has odd parity
same mass,same lifetime,
opposite P
t+ p+p+p-
mt = 970 me (495 MeV)R.Brown et al., Nature 163, 47,82 (1949)
photographic emulsion
1947 1949
Lee and Yang
C.N.Yang
T.D.Lee
Phys Rev 104, 254 (1956)
The q+ and t+ are the same particle,and its decays violate Parity.
(now known as the K+ meson)
Parity violation discoveredCo60 Ni60 e- nmore electrons are emittedopposite to the nuclear spindirection than along it
WU, Chien Shiung1912-97
The mirror image, where electrons are emittedparallel to the spin, doesn’t occur in Nature.
J J
C. S. Wu et al., Phys. Rev. 105 (1957), 1415.
_
1957 Nobel Prize
Lee, Tsung-DaoYang, Chen-NingWU, Chien Shiung
P-violations in m- & m+ decay
m-
e-
m- e-n n decays:e- emission opposite tospin direction preferred
m+
e+
m+ e+n n decays:e+ emission parallel tospin direction preferred
C is violated
ParticleAntiparticle operator
Phys. Rev. 105, 1415 (1957)R L Garwin, L M Lederman and M Weinrich
_
_
C x P in m decay
m-
e-
m+
e+
CPMirrored antimatter
case does occur in Nature
“charge conjugate”mirror
CP symmetry is OKViolated
Violated
CP in the neutral K meson system
00
21
002
1
KKK
KKK
CPodd
CPeven
-
+0
0
K
K
“Flavor”eigenstates
CP (Hamiltonian?) eigenstates
d s
s d
-+
-+
ppp
pp0
CPodd
CPeven
K
K-+
-+
pp
ppp
CPodd
CPeven
K
K 0
Violate CP
Short life-timeKShort
Long life-timeKLong
-+
-+
ppp
pp0
Long
Short
K
K
Christenson-Cronin-Fitch-Turlay Experiment (1964)
Long-livedneutral Kaons
p+
p-
Search for long-lived neutral kaon p+p-
Long-lived neutral Kp+p-
(~2 parts in 103)
Small CP violation(2x10-3) is seen
J. H. Christenson et al.,PRL 13 (1964), 138.
No prizes for Christenson or Turlay
1980 Nobel Prize
Incorporating CPV into QM
A A’Particle process
amplitude = Aantiparticle process
amplitude = A’
CPT theorem: |A|2 = |A’|2
A & can differ at most by a complex phaseA ‘
It‘s difficult to generate matter-antimatter differences in QM
Time-re
versa
l
(t-t)
A
+fCP
-fCP
In QM, processes are |Amp|2
Still no matter-antimatter difference(even though there is a CPV phase)A’
|A |2 = |A’|2
A
A’
+fCP
-fCP
Phase measurement needs interference(a second way to get to the same final state)
X
Still no matter-antimatter difference(even though there is a CPV phase
& an interfering process)
A
+ X
A’
|A + X|2 = | +X|2
A’+ X
A
A’
+fCP
-fCP
X must have a “common” phasesame phase for particle & antiparticle
XFinally an matter-antimatter difference
A + X
+ X
A’
|A + X|2 = | +X|2
A’d
Matter-antimatter differences in QM
• Amplitude needs a complex phase– Opposite sign for matter & antimatter
• Need an interfering amplitude– Competing process same final state
• Interfering amplitude needs a “common” phase– Same sign for matter & antimatter
Incorporating a CPV phase into the Standard Model for Particle Physics
Quark mixing
In the late 1973, there were 3 known quarks (u,d,s):
duq=+2/3
q=-1/3
K & M were convinced of the existence of a 4th quark: the hypothesized “charmed” quark (c):
scsc
In the Weak Int. the s & d quarks mix
Mass (& flavor) eigenstates
-
sd
sd
-
sdsd
sd
quark-flavor-mixingMatrix
Weak-interaction eigenstates
The weak interaction quark doublets
+ sdu
+- sd
c
The CPV KLongp+p- decayscorrespond to this transition
Incorporate CP violation by making complex?
d
s
d
udu
KLong
p -
p +
: Not so simple
a 2x2 matrix has 8 parameters
unitarity: 4 conditions
4 quark fields: 3 free phases
# of irreducible parameters: 1 Cabibboangle
1001
**
**
d
d
- CC
CC
cossinsincos
N.CabibboCabibbo 1st proposed quark flavor-mixing in 1963
Phys.Rev.Lett.10:531-533,1963
A complex phase cannot be includedin a 4-quark mixing matrix
Kobayashi-Maskawa paper (1973)Prog. of Theor. Phys. Vol. 49 Feb. 2, 1973
1 CP-violating phase3 “Euler” angles
4 irreducible parameters
a 3x3 matrix has 18 parameters
unitarity: 9 conditions
6 quark fields: 5 free phases
# of irreducible parameters: 4
100010001
***
***
***
d
d
Why were K&M so sure of the c quark?In 1972, they both were in Nagoya,where Kiyoshi Niu was on theExpt’l Particle Physics Faculty
2mm
2009: mD=1.87 GeV, mLc=2.29 GeV
K.Niu
HistoryNovember 1974: Charmed (4th) quark “discovered”@ Brookhaven & SLAC
1976 Nobel prize
Sam Ting Burt Richter
Phys.Rev.Lett.33:1404-1406,1974.Phys.Rev.Lett.33:1406-1408,1974
ppJ/y + X; J/ye+e-
M(e+e-) Ecm(e+e-)
e+e- hadrons
J/y = c c
Kiyoshi Niu
More History
November 1977: Bottom (5th) quark discovered@ Fermilab
February 1995: Top (5th) quark discovered@ Fermilab
Phys.Rev.Lett.39:252-255,1977. CDF: Phys.Rev.Lett.74:2626-2631,1995D0: Phys.Rev.Lett.74:2632-2637,1995
= b bpp t t X_ _
ℓ+n
bc_
Now there are 6 quarksas required by Kobayashi-Maskawa CPV mechanism
du
sc
bt
d
u
s
c
b
tWeak-interaction
eigenstatesMass (& flavor)
eigenstates
Related by a 3x3mixing matrix
Cabibbo-Kobayashi-Maskawa 6-quark mixing matrix
bsd
VVVVVVVVV
bsd
tbtstd
cbcscd
ubusud
'''
CKM
V
d s b
u
c
t
Nearly (but not exactly) diagonal
du
sc
bt
V≈1
du
sc
bt
V≈0.2
du
sc
bt
V≈0.04
du
sc
bt
V≈0.004
CKM hierarchy
The KM phases are in the corners
bsd
VVVVVVVVV
bsd
tbtstd
cbcscd
ubusud
'''
f3
t
d
W+
Vtd
b
u
W+
Vub
f1
The experimental challenge
bVub
W+
*
td
W+
Vtd
Measure a complex phase for bu
u
or, even better, both
or in td
Use B mesonsi.e. mesons containing the b- (5th) quark
B0 = B0 = b dd b
B0/B0 similar to K0/K0
Why B mesons?
1) B0 B0 mixing is strong
_
N(B
) – N
(B)
--
------
------
------
------
------
N(B
) + N
(B) _ _
If you start with a B0, it changes to a B0 (& vice versa) with a ¼-period (1/Dm≈2ps) that is comparable to the B0 lifetime (≈1.5ps)
_
2) b quarks are sensitive to CPV phases - they probe the corners of the CKM matrix
2 ps
B0
B0_
B0_
B0B0
eiDmt
B0
td+
td
B0
Vtb
V*
Vcb
KS
J/y
J/y
KS
V*2
Vtb
V*td
td
Vcb
B0B0
Sanda, Bigi , Carter technique for f1
+sin2f1
eiDmt
mixing provides the “common” phase
Phys.Rev.D23:1567,1981Nucl.Phys.B193:85,1981
Interfere BfCP with BBfCP _
What do we measure?
t Dz/c
“Flavor-tag” decay(B0 or B0 ?)
J/y
KS
B - B B + B
e- e+
more B tags
more B tags
Dz
t=0
fCP
(tags)
sin2f1
This is for fCP=+1; for fCP=-1, the asymmetry is opposite
Asymmetric energies
_B0 & B 0 in an “entangled”
quantum state
_
t
The Belle experiment at KEK
KEK laboratory in JapanTsukuba Mountain
KEK laboratory
KEKB Collider
elle
A magnetic spectrometer based on a huge superconducting solenoid
Find B0(B0?)J/y KS decays
B0(B0?) J/y Ks event
Tracking chamber onlym+m-
p+p-
_
Check the other tracks to see if the accompanying meson is a B0 or a B0
?
?
??
??
The K- in the remaining tracks means the other meson is (probably) a B0
(not a B0)
p-
p- p-
p+
K-p+
B D K-
&B D K+
are dominantdecay chains
_
Check the other tracks to see if the accompanying meson is a B0 or a B0
_
Determine the time sequence of the 2 decaysSilicon micro-vertex detector m+ track
tracks from accompanying B meson
m- track
Resolution ≈ 150mm
BJ/y KS decay occurs before the tag decay
Make the plot & fit itBelle 2007
sin2f1 = 0.681 ± 0.025
CP=+1 CP=-1
f1 = 21.50 ± 1.00 Similar results from the BaBar experiment at SLAC
Belle, Phys.Rev.Lett.87:091802,2001
BaBar, Phys.Rev.Lett.87:091801,2001
~7500 evts ~6500 evtsPRL 98: 003802 (2007) B0 tag
B0 tag_
B0 tag
B0 tag_
Compare with KM theory constraints from other processes
-
---
f
1tan
1
1 A
iViV
td
ub
f1
Nobel committee:“The results were exactly as Kobayashi and Maskawa had predicted…”
|
BaBar & Bellemeasurement
Vtd
Vcb
_
Stockholm, December 2008
Does this explain why there are no antipeople?
CP violation in the early Universe dueto the KM mechanism is too small
No! Not by more than10 orders-of-magnitude!
There must be another CPV source-one that’s not in the current Standard Model for particle physics-
Fourth generation of quarks?
New particles -- SUSY?, Technicolor?...
CPV in the neutrino sector?
…
How to find New Physics particles:1) Produce them in very high energy collisions
Go to CERN LHCworld’s highest energies
Join a 2000 physicist team Look for signs of NP particlesburied in very complex events
Or2) Look for effects of Virtual NP particles in B decays
(also: ’, K+K-, etc.)
For example BKf:virtual heavy NP particles could
contribute to the loop
so-called “Penguin processes”
, x
,YVtb Vts
*
Sensitivity
b st
Vtb Vts* HSM
VtbVts
Mt2
0.04Mt
2
*SM bs “penguin”
structure of the CKMmatrix suppresses FCNC
X= heavy NP particle
b sX
g g
heaviest of allknown particles
HNP |g|2
MX2
For “generic” NP (i.e. g 1): MX ≈ 5Mt can produce O (1) deviations from SM predictions
1 TeV, the largest mass accessible at LHC
example: sin2f1 with SM bs penguins
Vtb& Vts: no SM CPV phases in B0Kf ,…
SM prediction: sin2f1 = sin2f1 from BJ/y K0
Any difference new particles in the loop
penguin
Vtd
Vtd
+
f1
B0 B0
, ’, K+K-
f1
, ’, K+K-
*
*
Interfere with B0B0Kf, …_
Same measurement that we did for B0J/y K0
-except now the decays are much less common-
Vtb Vts*
sin2f1 from B0 → K0f & K0’penguin
sin2f1penguin
=0.67±0.22 sin2f1penguin
=0.64±0.11
sin2f1 = 0.681 ± 0.025 very near SM expectation of:
Belle, PRL 98: 003802 (2007)
~200 evts ~1400 evts
BaBar, PRD 79, 052003 (2009)BaBar, arXiv 0808.0700
~2000 evts~200evts
No evidence yet for new heavy particles
Different penguindecay modes
SM expectation
sin2f1
No O(1) NP effects: MX > 1TeV (g2)
What’s next?
Super-KEKB & Belle II50x increase in data
Make these error regions
as small as this one
Sensitivity for new physics increases to 10TeV or higher
well beyond the reach of the LHC
sin2f1
?
Summary1927: Nature is Left-Right symmetric Parity is an important symmetry
1956: Weak Interactions violate Parity, but CP symmetry is preserved
1964: CP is violated too
1973: CP violations require 6 quark flavors
20??: New non-SM CPV source found in B decays?
Laporte Wigner
Yang Lee
Kobayashi Maskawa
Cronin Fitch
Thank you감사합니다