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Palm tree and CKM. Beauty in the Standard Model and Beyond. Gabriella Sciolla (MIT). CIPANP 2006 - Puerto Rico - May 30 - June 3, 2006. Palm tree and CKM. Beauty in the Standard Model and Beyond. Gabriella Sciolla (MIT). CIPANP 2006 - Puerto Rico - May 30 - June 3, 2006. - PowerPoint PPT Presentation
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G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 1
Palm tree and CKM Beauty in the Standard Model and Beyond
Gabriella Sciolla (MIT)
CIPANP 2006 - Puerto Rico - May 30 - June 3, 2006
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 2
Palm tree and CKMBeauty in the Standard Model and Beyond
Gabriella Sciolla (MIT)
CIPANP 2006 - Puerto Rico - May 30 - June 3, 2006
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 3
Outline
The beauty of B physics CP violation in the B system and the Unitarity Triangle
Standard Model measurements Sensitivity to New Physics
Measurements of CP violation in B decays The experiments Measurement of the angles and sides of the Unitarity
Triangle
What have we learned? Summary and conclusion
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 4
CP violation What is CP?
Why is CP violation interesting? Crucial ingredient to explain the matter-dominated universe
A. Sakharov (1967) CP violation is expected in the Standard Model
Until recently, one of the least tested aspect of the theory Many new sources of CP violation Beyond the Standard Model
Sensitive to New Physics
C: Charge ConjugationParticle Anti-particle
P: ParityInverts space coordinates
CP = C × P
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 5
CP violation in the Standard Model Discovered by Fitch and Cronin in 1964 in KL decays Introduced in Standard Model in 1973 by Kobayashi and
Maskawa In KM mechanism, CP violation originates from a complex
phase in the quark mixing matrix (CKM matrix)
)(
1)1(2
11
)(2
11
6
23
22
32
O
AiA
A
iA
VVV
VVV
VVV
V
tbtstd
cbcscd
ubusud
b c
W-cbV
A, (Cabibbo angle): very well measured: poorly known until recentlyFirst goal of CP violation studies:
Precise determination of the parameters and
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 6
Pros and Cons of CKMPros:
Elegant and simple explanation of CPV in SM It is very predictive: only one CPV phase It accommodates all experimental results
Indirect CP violation in K and KLl Direct CP violation in K CP violation in the B system
Cons: nB/n predicted by CKM « observed value
…by orders of magnitude!
New sources of CPV must exist besides CKM!
.
CP violation as a probe for New Physics:Measure CP violation in channels theoretically well understood
and look for deviations w.r.t. SM expectations
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 7
Unitarity of CKM implies: V†V = 1 6 unitarity conditions Of particular interest:
All sides are ~ O(1) possible to measure both sides and angles! CP asymmetries in B meson decays measure and Sides from semileptonic B decays, B mixing, rare B decays
The Unitarity Triangle
0VVVVVV *tbtd
*cbcd
*ubud
*
*ub ud
cd cb
V V
V V
*
*tb td
cd cb
V V
V V
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 8
Standard Model or New Physics?
Two ways of looking for New Physics: Compare measurement of sides and angles
2 measurements define the apex; >2 test Standard Model All pieces of the puzzle must fit: inconsistencies mean New
Physics Measure same quantity in channels with different
sensitivity to NP E.g.: measure in modes mediated by different decay
diagrams
Precision and redundancy are essential!
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 9
The experiments: B factories BaBar (SLAC) and Belle (KEK)
e+e- asymmetric collisions . (4S) resonance
Advantages of the B factories No need for bb trigger
Very clean environment:
High luminosity Peak luminosity > 1034 cm-2s-1
Integrated luminosity 350/600 fb-1 (BaBar/Belle)
10.58 GeVs
+ -e e (4s) BB
bb : ~ 1 : 4 qq
350/600 fb-1 (BaBar/Belle)
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 10
The experiments: Tevatron experiments CDF and D0 at Fermilab
.
Challenges of the Tevatran Special trigger necessary for B events
High multiplicity events Advantages of the Tevatron
Large number of B produced
L~1032 cm-2s-1 but high x-sections
Integrated luminosity: >1 fb-1
All b hadrons are produced BS , b , BC ,…
pp collisions at s ~ 2 TeV
bb : ~ 1 : 1000 inelastic
Complementary to B factories
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 11
The measurements
*
*ub ud
cd cb
V V
V V
*
*tb td
cd cb
V V
V V
The angle
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 12
BfCP exclusivereconstruction
How to measure the CP asymmetry
.
e-
Flavor taggingQ=(30.5 0.5)%
(4S)
B0
B0
e-
+
-
e+
+
-
Precise t determination
z~ c t
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 13
CP violation at the B factories
0 0
0 0
( ( ) ) ( ( ) )( )
( ( ) ) ( ( ) )
sin( ) cos( )
CP CPCP
CP CP
ff
N B t f N B t fA t
N B t f N B t f
S mt C mt
2
2
1
1
f
f
f
C
2
2Im
1
f
f
f
S ff
f
Aqλ
p A
i2e~
0B
0B
CPf
mixin
g
decay
0t t
CPfA
CPfA
(f
)
When only one diagram contributes to the final state, ||=1
0
Imf
f
C
S
ACP(t) = ± Im sin(mt)
(CP violation in interference between mixing and decays in B0 )
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 14
CP violation in B0 decays: sin2For some modes, Im is directly and simply
related to the angles of the Unitarity Triangle.
Example: B0J/KS: the “golden mode”
Theoretically clean Experimentally clean Relatively large BF (~10-4)
ACP(t) = sin2 sinmt
0 0
* * *2
* * *
mix mix
itb td cs cb cd cs
tb td cs cb cd csB decay K
V V V V V Ve
V V V V V V
0B
/J
SK
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 15
The golden mode for sin2: sin2 in B0 J/ KS
Belle 386 fb-1
mES [GeV/c2]
sin(2) = 0.685 ± 0.032 WA EPS
2005
Belle 386 fb-1
B0J/ KS Belle 386 fb-1
t [ps]
t [ps]
sin(2)= 0.652 ± 0.039 ± 0.020
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 16
Unitarity Triangle constraints
sin2 vs indirect UT constraints: very good agreement!
New Physics does not show up in the golden mode SM reference Compare with sin2 in independent modes with different sensitivity to NP
CKM mechanism is the dominant source of CPV at low energies
95% CL from sides
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 17
The key to New Physics:
The Penguin Modes
Decays dominated by gluonic penguin diagrams The typical example: B0KS
No tree level contributions: theoretically clean SM predicts: ACP(t) = sin2sin(mt)
Impact of New Physics could be significant New particles could participate in the loop new CPV phases
Low branching fractions (10-5) Measure ACP in as many bsqq penguins as possible!
φ K0, K+ K− KS, η′ KS, KS π0, KS KS KS, ω KS, f0(980) KS
d d
SM NP
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 18
The golden penguin: B0 K0
N(Ks)=180 ± 16Belle 386 fb-1
Belle 386 fb-1
Belle 386 fb-1 B0KS
B0KL
0
0
0.44±0.27±0.05
-0.14±0.17±0.07K
K
S
CBelle 386 fb-1
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 19
The silver penguin: B0 ’KS
Larger BF ~ 6 x 10-5 but theoretically slightly less clean than KS
Sη′Ks = 0.30 ± 0.14 ± 0.02
Cη′Ks = −0.21 ± 0.10 ± 0.02
' 804 40SKN
BaBar 210 fb-
1
BaBar 210 fb-
1
BaBar 210 fb-
1
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 20
“sin2” in penguins
A trend is visible although each
measurement is compatible with J/KS…
Most significant shift in ’KS ~2.1
Naïve average: 0.50±0.06 ~2.5
… statistical errors still large…
BaBar + Belle average
Penguin modes
Golden mode
J/KS
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 21
The measurements
*
*ud ub
cd cb
V V
V V
*
*td tb
cd cb
V V
V V
The angle
ubud
tbtdargVV
VV
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 22
sin2in Tree diagram dominates
Relatively large Branching Fraction (B0 → ) = (25.2 ± 3.7 )×106
Penguin contribution small (B0 → ) < 1.1×106 (90%C.L.)
Vector-vector final state: is CP defined? In principle admixture of CP+ and CP- eigentastes…
ACP(t) = sin2 sinmt
*
*
*
*
)1(ubud
ubud
tdtb
tdtb
VV
VV
VV
VV
b du
u
W
gtbV *
tdV
Penguin
ubud
tbtdargVV
VV
b uu
d
W
ubV
Tree
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 23
Is CP defined in ? Vector-vector final state
3 possible L states
Measure fraction of longitudinal polarization in angular analysis
021.0 029.0 014.0978.0
LfBaBar 210 fb-
1
S wave (L=0, CP even)
P wave (L=1, CP odd), only transverse polarization
D wave (L=2, CP even)
~ 100% longitudinally polarized CP even eigenstate
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 24
CP asymmetry in B0 →
09.018.003.0
024.033.0 008.0 014.0
C
S
BaBar 210 fb-
1
0 tagsB
0 tagsB
BaBar 210 fb-
1
BaBar 210 fb-
1
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 25
Combined constraints on
Average of BaBar and Belle +15
-9 = 105 °cfr: CKM fit
+5-16 = 97 °
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 26
The measurements
*
*ud ub
cd cb
V V
V V
*
*td tb
cd cb
V V
V V
The angle
cbcd
ubudargVV
VV
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 27
The angle .
0
+ 0 + + 0 +
0
Use interference between and with both
D and D decaying
B D K B D K
same final stto t athe e f
Cabibbo allowed Cabibbo and color suppressed
cbcd
ubudargVV
VV
NB: only tree diagrams: 100% Standard Model
B
B
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 28
from B → DK GWL (Gronau, Wyler, London)
D CP eigenstate Theoretically clean Small interference: needs more data
ADS (Atwood, Dunietz, Soni) is doubly Cabibbo suppressed
Larger interference Needs more data
Dalitz method (Giri, Grossman, Soffer, Zupan) Exploits interference pattern in Dalitz plot in DKS
Combines many modes statistical advantage Small systematics due to Dalitz model Currently
most sensitive
( )A D f
D0KS+-
See talk by M. Verderi
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 29
Summary of measurements Direct measurement on
BaBar + Belle, all methods combined
Indirect constraints:
65 20 deg
61.1 4.5 degUTFit
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 30
The left side: Rb
*
*ub ud
cd cb
V V
V V
*
*tb td
cd cb
V V
V Vubb
cb
VR
V
1.31.221.7 degrees
NB: is the best measured quantity in the Unitarity Triangle
precise measurement of Rb is needed for accurate tests of SM
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 31
Semileptonic B Decays
Sensitive to hadronic effects Theory error not negligible
Prob(bc)/Prob(bu)~50 Vcb precisely measured (2%) Vub is the challenge
b
,u c
, cub bV V
Parton level
W l
22 5
2( )
192F
ub b
Gb u V m
22 5
2( )
192F
ub b
Gb u V m
B
uX
b
u
ubVB
, cuX X
Hadron level
l
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 32
Two approaches to Vub
Inclusive B Xul Hadronic final state is not
specified
bc l background is suppressed using kinematical variables
Partial rate is measured
theoretical uncertainties ~5%
Inclusive B Xu l
B
uXubV
Exclusive B l
B
W
ubV
Exclusive B l Better S/B but lower branching
fraction (10-4)
Needs form factor calculation from Lattice QCD
uncertainty of ~ 12%
l- ll-
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 33
|Vub| from Inclusive B Xu l
Close collaboration between theorists and experimentalists led to
c.f.r.: precision on : 5.5%
World Average 4.45 0.33
2/dof = 5.5/6
Precision on Vub: 7.4%
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 34
The last side of the triangle: Rt
*
*ub ud
cd cb
V V
V V|| *
*
cbcd
tdtb
VV
VV tdt
ts
VR
V
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 35
The measurement of Rt
Bs/Bd oscillations
Theory error <5% md is precisely measured But Bs mixing is very hard…
1 tdt
ts
VR
V
( )td sV
( )td sV
b
b
( )d s
( )d s
t
t
W0( )d sB 0
( )d sBW
2
d td
s ts
m V
m V
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 36
History of BS mixing 6 experiments, > 10 years of work
Then early this Spring… D0: double sided limit on mS
CDF: first observation of BS mixing
Dec 2005
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 37
BS mixing at the Tevatron
. .
. .
Reconstruction of BS decay in hadronic or SL modes
Flavor taggingQSST~4%QOST~1%
Time reconstruction(ct)~26-70 m
Talk on Fri by Matthew Jones
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 38
D0 result
. .
. .
BsμDs: 5601±102
ms < 21 ps-1 @ 90% CL assuming Gaussian errors
Most probable value of ms = 19 ps-1
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 39
CDF result
Probability of random fluctuation: ~0.5%
0.42 0.008td0.007
ts
-10.2117.33 0.07 ps
V 0.208
VSm
3,700 events
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 40
Impact of mS on Unitarity
Triangle
G. Sciolla – M.I.T.Beauty in the Standard Model and
Beyond 41
Conclusion Standard Model: precision
Tremendous improvement in and Precision ~ 0.05
First quantitative test of CPV in SM CKM is the dominant source of CPV
New Physics: redundancy Sides vs angles in agreement with SM First signs of NP in sin2 in penguins?
More statistics will help: Analyzed: ~500 fb-1 Available: ~1 ab-1
By 2008: > 2 ab-1 .
BaBar+BelleCP-violating
measurements
CP-conserving measurements