Transcript Latest Results from NA48 on KL & KS CP Violating Related Rare

40 Years after Discovery of
Strangeness, Parity and CP
violations – Why are we still
working on Kaon Physics?
Mayda M.Velasco
Northwestern University
Oct. 1, 2004
From the biased point of view from a member of NA48@CERN
In order to put the subject in context,
let’s look at the main question of the
particle physics community…
●
●
●
●
●
●
Where did the anti-matter go? … What caused
the matter-antimatter asymmetry of the
Universe?
Can we explain the matter and energy
composition of the Universe?
Why are there so many particles? … What
causes their masses to be so different?
Where does mass come from?
Do all known forces unify as some large E
scale?
Are there extra dimensions of space?
2
Nevertheless we have a successful
Model
Puzzles brought &
answered by strange
Kaon
qqq
qq & Hyperon
physics has revealed
many aspects of
“TODAY’s”
Standard Model of
Particle Physics
 More to come… 3
Original Puzzles from Kaon
decays
●
1944-47: Strangeness  quark model
4
Puzzle #1 -- Strange particles
observed:
Long lifetimes
& Heavy
Strangeness
- produced by strong
interaction
   p  0  K 0 - conserved by strong
interactions  these strange
particles produced in pairs
d
u
u
u
d
g
s
s
5
Original Puzzles from Kaon
decays
●
●
1944-47: Strangeness  quark model
 Basis for QCD  gluon
1956: Parity violation
6
Invariance under Lorentz
transformation implies
 CPT invariance
Therefore… big impact on the foundation of the theory, if
interactions behave in different ways under:
• Charge conjugation(C): reverses the electric charge & all the
internal quantum numbers.
• Parity (P): space inversion; reversal of the space coordinates.
• Time reversal (T): replacing t by -t. This reverses time
derivatives like momentum and angular momentum.
Particles and antiparticles have identical masses and lifetimes.
This arises from CPT invariance of physical theories and is used
experimentally to test CPT.
7
Puzzle #2 – Parity violating Decays:
V-A Theory of Weak Interactions (WI)
●
Kaons are mesons (Spin = 0; Parity = -1):
K0 = d s
K0 = d s
●
K+  +0
 +-+
K+ = u s
K- = u s
S = +1
S = -1
P=(-1)(-1)
Even
P=(-1)(-1)(-1)
Odd
t  q Puzzle
•Strangeness not conserved WI
Extra confidence in the V-A theory
(Spin-Flip)
 BR = 63%
Helicity suppressed due to low mass
of e+
 BR = 0.0015%
8
Puzzels
from
Kaon
Original Puzzles
from
Kaon
decays
decays
●
●
●
1944-47: Strangeness  quark model
 Basis for QCD
1956: Parity violation
 Chiral nature of weak interactions
1964: Suppression of FCNC
9


Puzzle #3 – Low rate of KLm m :
Predicts no mixing with Z0 boson
& existence of Charm Quark
If possible should represent
~ 60% of the decays
 Not Observed
Consistent with observed rate ~10-5
d
KL
_
s

u
d
KL
_
s
FCNC not allowed
W
W

c
W
W
mnm
m
m-
nm
m
Extra u like quark needed to
get proper rate Charm
10
Original Puzzles from Kaon
decays
1944-47: Strangeness  quark model
 Basis for QCD
● 1956: Parity violation
 Chiral nature of weak interactions
● 1964: Suppression of FCNC
 Properties of the weak neutral currents
 Suggested charm quark
● 1964: CP violation
●
11
Puzzle #4 – CP violating Decays (CP):
K0 reveals a more intricate picture
•Flavor Eigenstate
K0 - K 0
0
K
0
d
_
s
d
K _
s
oscillations
s

u, c, t

W
W
W
u, c, t
_ __
u, c, t
u, c, t
W
_
d
s
_
d

0
K
0

K
12
K0 - K0 Oscillation quantified from
leptonic decay
Get positron:
Or electron:
Kaon Interferometry
G >> G
G  m
13
Puzzle #4 – CP violating Decays (CP):
K0 reveals a more intricate picture
•Flavor Eigenstate
K0 - K 0
•CP Eigenstate
K1oo
K1+K2+-o
K2ooo
0
K
CP=+1
0
d
_
s
oscillations
s

u, c, t
d

CP=-1 K _
s
W
W
W
u, c, t
_ __
u, c, t
u, c, t
W
_
d
s
_
d

0
K
0

K
•Mass Eigenstate  Before observation of CP violation
Ks
KL


1
 K1 
K0  K0
2
1
 K2 
K0  K0
2


t = 0.9 x 10-10 s
t = 5.2 x 10-8 s
14
Puzzle #4 – CP …Continues
KL  observed!  Violation of CP
st
1 :Indirect
2nd:Direct
1-2 per mil effect
NA48/KTEV
g,
– 1964
q
0
q
Re(e’/e)
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Puzzle #4 -- CP: clasification
MIXING or INDIRECT
DIRECT
CP eigenstates ≠
mass eigenstates
CP violation in the
decay amplitute
INTERFERENCE
DIRECT CP firmly
established after
more than 30
years
Re(e’/e) =
(16.7±2.3)x10-4
CP violation from
interference of
“DIRECT and MIXING”
e
Re(e’/e)(10-3)
Re(e’/e)
16
Original Puzzles from Kaon
decays
●
●
●
●
1944-47: Strangeness  quark model
 Basis for QCD
1956: Parity violation
 Chiral nature of weak interactions
1964: Suppression of FCNC
 Suggested charm quark
 Properties of the neutral currents
1964: CP violation
 Subtle connection to 3-generation
structure of matter
17
rd
in
Kaons
required
a
3
CP
generation of quarks to maintain
Unitarity
3X3 a complex phase possible
Without giving up Unitarity
Vud Vus

 Vcd Vcs
V V
ts
 td
2
3

Vub 
1 λ / 2
λ
Aλ  ρ  iη 

 
2
2
Vcb   
λ
1 λ / 2
Aλ



3
2

Vtb   Aλ 1  ρ  iη   Aλ
1

  0.2
If V*tdVts is complex CP is violated..
In shorthand:
A2  0.04
A (    )  0.004
3
2
2
V V  t  A  (1     )
*
ts td
2 5
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Summary of “s” puzzles and
their contribution to the SM
●
●
●
●
1944-47: Strangeness  quark model
 Basis for QCD
1956: Parity violation
 Chiral nature of weak interactions
1964: Suppression of FCNC
 Suggested charm quark
 Properties of the neutral currents
1964: CP violation
 Subtle connection to 3-generation
structure of matter
 Absolute matter-antimatter asymmetry… 19
Why Puzzle #4 was so interesting?
Potential Solution to the Baryon
Asymmetry in the Early Universe
q
+
10,000,000,001
q

2g
10,000,000,000
q
q
q
 They basically have all annihilated away
except a tiny difference between them
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Baryon Asymmetry in the
Current Universe
us
1
…This is us TODAY!!!
… After 30 years of studying CP-violation in the quark sector:
Now we know that the effect is too small to be source of the
Baryon Asymmetry
21
Summary of “s” puzzles and
their contribution to the SM
●
●
●
●
1944-47: Strangeness  quark model
 Basis for QCD > 30 Years Later
1956: Parity violation
 Chiral nature of weak interactions
1964: Suppression of FCNC
 Suggested charm quark
 Properties of the neutral currents
1964: CP violation > 30 Years Later
 Absolute matter-antimatter asymmetry…
 Subtle connection to 3-generation
22
structure of matter
So…What is
currently going on
in Kaon physics?
 Let’s use NA48@CERN as
an example
23
Basics of Kaon Experiments like
NA48
p
450 GeV protons from the
CERN SPS hit a Be-target to
produce the particles from
which we make our beam line.
p (n)  X1,X2,X3,X4,…
Neutral particles – not much
can be done without
destroying them.
Charged particles – can be
momentum selected,
transported and accelerated,
if needed.
@ NA48 we study the decay of both neutrals and charged Kaons 24
Is there anything interesting in our
NA48 neutral kaon beam lines?
Bent
Crystal
25
Beam instrumentation
development based on
aligned crystals
Apyan,Velasco
•Our NA59-Northwestern
group used coherent
phenomena & birefringence in
aligned crystals to make:
– polarimeters
– /4 plates for 100 GeV g
–Polarized positron sources
26
Relevant Beam lines in 2002 &
2003-4
K beam line
S
K± beam line
27
Decay region:
Join HE Physics & you might find
your self doing “archeological”
work
Our decay tank is not
a passive device
Northwestern:
measure unexpected
magnetic fields inside
this vacuum tank
Remember the
Gargamelle experiment?
 The ghost is still in our
experimental hall
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and stay fit…while fixing the
reconstruction of the charged
tracks
Gargamelle
magnet was
around this
location!
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NA48 Detector
Muon system:
s(t)  350 ps
M(00) ~ 2.5 MeV
M(+-) ~ 2.5 MeV
Spectrometer:
pT kick ~250 MeV/c
(P)/P  0.48%  0.009 P[GeV/c]%
LKr Calorimeter:
(E)/E  3.2%/√E  9%/E  0.42%
s(t)  265 ps for 50 GeV e-
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Liquid Krypton
Calorimeter (LKr)
> 13,000 cells of 2X2 cm2 filled
with ~10 m3 of liquid Krypton
Northwestern responsibility
- readout
- calibration
- corresponding trigger
Electron / pion separation:
E(LKr)/Momentum track
(spectrometer)
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So… What are the new puzzles &
what are we doing to understand
them?
●
Anomalous B decay rates
–
Enhance weak penguins? Physics beyond the
SM
 Teresa’s thesis (NA48 data 2002, KS)
●
Violation of unitarity?
–
More than 3 generations  Physics beyond the SM
 Anne’s Thesis (NA48 data 2003, K±)
●
Anomalous  0ene rate
–
Tensor interactions  Physics beyond the SM
 NA48 took special data sample this summer…
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(new students welcome !)
Note on penguin diagrams
g,
q
q
Z, (g)
?
Z,
(g)
???
n, l-)
n, l+)
n, l-)
n, l+)
Example, KL 
Not a good mode to look
for New Physics… gluon
hard to calculate!
Example, KL n n
 mm
 e+eZ0 penguin diagrams well
understood, therefore a
better mode to look for
deviations from the SM.
33
st
1
puzzle: New Physics(NP) in
0
KL ll ?
Not only Knn ! NP sensitivity
of KL0ll system :
Buras,Fleisher,Recksiegel,
Schwab : hep-ph/0402112
Based on our
Teresa’s results
34
S → 
must be measured
before looking for NP in L → 
0ll
0ll
J=2: Br(KL0ee) < 3x10-12
CPC
J=0: Br(KL0mm ~ 5.2x10-
Indirect CPV
12
Direct
CPV
Br(KL0ee) = 5x10-12
Br(KL0mm) = 1x10-12
35
Teresa’s thesis: First observation
[PLB576 (2003)]
of KS 0 l +l - CERN-PH-EP/2004-025
KS0m+m-
Mgg(GeV)
MK(GeV)
KS0e+e-
7 signal
events
6 signal
events
Mgg(GeV)
Mmm(GeV)
BR(KS  0 ee) =
(5.82.8
2.3
BR(KS  0 m m  =
(2.91.4
1.2
stat
stat
 0.8syst ) x 109
 0.2syst ) x 109
36
Implications for KL  
0 l l
Constructive
BR(KL 0 l l)CPV × 1012
BR(KL 0 l l)CPV × 1012
BR(KL  0 e e )CPV × 1012 =
Destructive
BR(KL0 e+ e-)SM x 1011 = (3.1 or 1.3) ±1.0
BR(KL0 m+ m-)SM x 1011 = (1.8 or 1.2) ±0.3
37
So can we look for NP in L → 
0ll?
CPC
Indirect CPV
OK!
OK!
Direct
CPV
Now we check for
NP in the EW
Penguins
38
Recent rearches for KL
st
 Answer 1 puzzle
0l+l-
?
Accessible from data currently
being taken in Japan
KTeV results
BR(KL → 0 ee )
< 2.8 × 10-10 @ 90%CL
1 event (1 expected
background)
BR(KL→ 0 mm)
< 3.8 × 10-10 @90%CL
Interf (-)
Interf (+)
2 event (0.87 expected
background)
39
nd
2
Puzzle: CKM matrix – Unitary
Problem?
• Unitarity of CKM matrix requires:
|Vud|2 +|Vus|2+ |Vub|2 = 1
• PDG 2004 data:
|Vud| = 0.9738 ± 0.0005 - Neutron b-decay
|Vub| = (3.67 ± 0.47).10-3 - ( |Vub|2 ≈ 10-5 negligible)
• SM prediction
|Vus1
| =%
0.2274
± 0.0021
Measurement
needed
• Experimental value (begining 2003)
(limited
|Vus| = 0.2200
± 0.0026by theory)
 |Vus| = 0.0074 ± 0.0033 ~2.2  discrepancy
40
Anne’s Thesis: Precise measurement
of Vus
|Vus| |f+(0)| =
16 π3/2 Γ(Ke3)1/2
————————
GF MK5/2 SEW1/2 I1/2
Ke3 Br measurement:
• Normalize Ke3 events to π ±π0
events
Br(π ±π0) = 0.2113±0.0014
• Selected Events:
Ke3+ ..... 59k
Ke3- ..... 33k
π ±π0 .... 468k π ±π0....260k
Conference Summary
ICHEP 2004, Beijing -- John Ellis
Anne’s
Thesis
Vus x f+(0)
New Determinations of Vus
2nd Analysis
Also from
NU
Michal Szleper
•PDG02
CKM unitarity ‘crisis’ has disappeared
42
So what was wrong?
Radiative Corrections
Ginsberg (Phys. Rev. 162, 1570 (1967) Phys. Rev. 187, 2280 (1969))
Data/MC
Without radiative
corrections
Data/MC
With
correction
43
Physics misconceptions cleared…
EXAMPLE BASED ON NEUTRAL KAONS – T. Andre
Ke3
Ke3g
Km3
Km3g
44
Fine!
Kaon Physics is
still producing
interesting results…
What is next?
45
Original list  new era to
open up with the LHC
program
●
●
●
●
●
●
Where did the anti-matter go? … What
caused the matter-antimatter
asymmetry of the Universe?
Can we explain the matter and energy
composition of the Universe?
Why are there so many particles? …
What causes their masses to be so
different?
Where does mass come from?
Do all known forces unify as some
large E scale?
Are there extra dimensions of space?
46
We are already getting ready for
the
Large Hadron Collider (LHC)
In LEP/LHC tunnel
(circonf. 26.7 km)
PP collisions at
s = 14 TeV
4 experiments
25 ns bunch spacing
 2835 bunches
1011 p/bunch
Design Luminosity:
1033cm-2s-1 (1034cm-2s-1)
10 (100) fb-1/year
23 inelastic events
per bunch crossing
Planned Startup in April 2007
47
However the LHC program will
probably will not be enough…
Rocky Kolb:
"physicists have long known that "empty" space is not empty;
it is filled by a field that gives quarks and leptons their mass.
In the Standard Model, this field is called the Higgs... Dark
energy may have relationships to both supersymmetry and
the Higgs sector, implying a new emphasis on the quantum
consistency of Higgs physics, including Higgs
self-interactions."
Cosmologies
 abundance
Particle Physics  properties
We will probably need a Multi-TeV e+e- ASAP 2015
48
CLIC Dual beam scheme – Only
viable multi-TeV Technology
With superconducting cavities:
Requires 33 km for 0.5 TeV
Cannot go beyond 0.8 TeV
CLIC150 MV/m
3TeV vs 0.5TeV
CLIC vs TESLA
49
Aiming at having a
design by 2008-10
50
Exotics...One example only
(TeV Machines)
Desert
New Physics at~TeV
extra dimensions could bring MPl down to TeV
51
Why do not see extra dimensions?
Only gravity propagates
Through this large extra
dimension
 MS
52
Light-by-Light Scattering
Graviton
Spin-2
Tensor
53
X-sections in presence
of gravitons
54
Conclusions…
Future is:
Plenty of fundamental questions to be answered
 So… let’s go back to work!!!
55
Backup for CLIC
New Preliminary NA48/2 Br(Ke3)
Br(Ke3) = (5.14 ± 0.02 stat ± 0.06 syst)%
57
Ks
 
0
 e e
 Backgrounds
Signal region
Physical: g conversions (mee> 0.165 GeV/c2)
< 0.01 (KS
KL
eegg (irreducible)
0.08
 0 decays (momentum asymmetry cut) negligible
Accidental: Study of out of time events
D0 D0 )
0.07
Total bckg events
in signal region:

0
.1
0
0
.1
5

0
.0
4
58
Ks 
 
0
m m 
Backgrounds
Signal region
Physical: KL
     0 (cut on KS ct )
KL
m  m  g g (irreducible)
 0 decays (Momentum asymmetry cut)
negligible
0.04
negligible
Accidental: Study of out of time events
0.18
Total bckg events
in signal region:

0
.1
9
0
.2
2

0
.1
2
59