Introduction : CP violation in the SM, constraints/consistency Asymmetric B factories : KEKB/BELLE,...
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Transcript of Introduction : CP violation in the SM, constraints/consistency Asymmetric B factories : KEKB/BELLE,...
• Introduction : CP violation in the SM, constraints/consistency• Asymmetric B factories : KEKB/BELLE , PEPII/BABAR
• The experimental path to CP violation • First results• Prospects
Roy ALEKSANCEA Saclay, DAPNIA/[email protected]
CMS Workshop on B and Physics Helsinki, Finland
May 30-June 1 , 2002
CP Violation at Asymmetric e+e- collidersA new era has started ...
As far as one looks, the univers seems to be made of matter (NB/N10-10)
What is the mechanism that lead to this situation ?
In 1967 Sakharov Suggested that theorigin might be due to• B • CPin a universe in thermal non-equilibrium
Is there any interaction distinguishing matter from antimatter ?
Is it a fundamental property ?
?
Why do we care about CP Violation ?
XB1
B2
f
1-f
XB1
B2
f
1-f
])1([])1([ 2121 BBBBXX ffff
B1 = - B1 B2 = - B2
Since antiparticles have opposite quantum numbers
)BB()( 21 ffIf XTo get NB 0
B1-B2 0 and f-f 0B CP
Unitarity Triangle Determination
C(0,0) B(1,0)
A()
cb
udub
V
VV
cb
tdtb
V
VV
*
0
)(0
)( sdsd BB Bd0 , ,
,,/ )()(0 DDKJB sd B D K
B D K
s s0
0
( ) ( )
( )
,
,
B c D
B D D
, ,
,
( )
( ) ( )
B u
B
, ,
,
0VVVVVV tdtbcdcbudub
4
23
22
32
112
1
21
O
AiA
A
iA
tbtstd
cbcscd
ubusud
CKM
VVV
VVV
VVV
V
B physics0
V
VV1
V
VV
cb
tdtb
cb
udub
from K decays
If is removed, triangle could be flat or upside down !!!
Most of the uncertaintiesare due to theoreticaluncertainties
Note
Present knowledge on the Unitarity Triangle
Without using CPViolation measurements
in B physics
8234γ
5.01α2sin
89.047.0β2sin
The comprehensive study of CP violation requires the angle measurements
3 ways to produce CP violation in the SM
Interference of 2 direct decay amplitudes DIRECT CP VIOLATION
Interference of 2 mixing amplitude T violation
Interference of a direct decay and a mixing induced decay amplitude
W
B+
K+
0b
us
uuu
gt,c,u
B+
b
u
W
0uu
K+su
00 :ex KBKB
Asym M1 M2 sin(s) sin(W)No major exp. difficulties … but ratesDifficult to extract CKM Phase ... except for some cases
Bd0
W+
-b
u
ddu
d
Bd0
b
d
b
t,c,u tc,u, +u
d
-du
b
d
b
t xd
-
c
Bd0
b
d
b
xd
-
c
t c ,u c u,
)BBBB( 0000
NN:ex2
B
B
1
)(4
Asym
Very small Asymmetry (<1%)Rates OK … but experimentaldifficulty to control systematics
0d
0d BB :ex
At (4S) Asym(t) sin(W)sin(mBt)Clean extraction of CKM phase … but penguin pollution in some cases Need tagging of initial B flavorat (4S) need Dt time measurement
Bd0
Mixing + decay
Mixing Direct CP
***Clean
*Limited by
syst. and theory
*Limited by stat.
and theory
**Limited by stat.
or theory
*Limited by stat.
and theory
**Clean but stat. very limited
**Clean but stat. very limited
Qualitative quideline for measuring the angles of the Unitarity Triangle
ATLAS
2006
BTEVBTEV
CLEO 3BBAABBARAR
2005
1999 2000
2001
BELLE1999
2000
The World Quest for CP Violation in the B SystemThe World Quest for CP Violation in the B System
Primary Goal :Primary Goal :Primary Goal :Primary Goal :1) Carry a comprehensive study of CP violation in the b quark system2) Test the consistency of the Standard Model in the CKM sector and probe the origin of CP violation
Main Parameters of the asymmetric e+e- colliders
Achieving the nominal parameters is one of the challenge !!!… but full success of the physics program requires
Factory Operation
PEPII KEKB
HER LER HER LER
Ebeam (GeV) 9.0 (9.0) 3.1 (3.1) 8.0 (8.0) 3.5 (3.5)
Ibeam (A) 0.75 (0.92) 2.1 (1.7) 1.1 (0.9) 2.6 (1.4)
Nbunch 1658 (830) 2700 (1224)
Lifetime (mn) 600 250 300 200
Luminosity (cm-2 s-1) 3x1033 (4.3x1033) 1034 (7.2x1033)
Nominal values(present achievements)
L=76.0fb-1
KEKBPEPII
Operation and Luminosity of KEKB and PEPII
Both KEKB and PEPII are working very well in factory mode
KEKB and PEPII will run at least until next summer
Samples ofFully-Reconstructed B Decays
Cabbibo-favored hadronic decays “Open Charm” decays e.g.
Charmonium Decays
e.g.
Semileptonic decays
e.g.
ducb
s)cc(b
1)(0 /a/ρπDB
K/JB
DB0
Flavor eigenstates for mixing and lifetime measurements
)(cb
Reconstruction of B final states
2
,1
2
2
nii
cmB p
Em
2,1
cm
nii
EEE
2 main variables to identify B
~21000 signalPurity: 85%
Neutral Neutral BB Mesons Mesons
BBAABBARARBBAABBARAR
Charged Charged BB Mesons Mesons
~20000 signalPurity: 85%
Measurements of
B0
J/KS
B0 K-
D
General requirements for studying CP violation
also jet charge, partial D ’s, ...
d
z
Needed information to measure CP violation
1) Identify a reconstructed B0 (ex: J/KS
2) Measure t12 z
3) Identify the flavor of B0 at t0 using 2nd B
(i.e. tagging)
t0 t1 t2
tmef dt sin2sin1
)(/
)(
CPCP0BP
or ,
with
149.0 psmd
S0 KB :ex J
<z>=260m at PEPII<z>=200m at KEKB
Start the clockAt (4S) Factories
Btag=B000tag BB
)7.02(sin
CP Violation in mixingDileptons allow to test whether
)Prob()Prob( 0000 BBBB
24
4
1
e4
/1
/1
)()(
)()()(
B
BTA
pq
pq
NN
NNt
AT = (0.5 1.2 1.4)%
*tdVtbV
*tdV tbV
b
b
t
t
d
d
0B0B
CKM3-
tdtb
tdtbcbcd
m
mG
2t
2c
12
10-1
VV
VVVV1mm
M2W
2t
sin
Im21Im
21
1 212
qp
43 101101 TA
CL%90at005.01e2
BB
BABAR : Measurement of sin2
CP-1
sin2=0.76±0.10 ±0.04 sin2=0.73±0.19 ±0.07
BBAABBARARBBAABBARAR
raw asymmetry
sin2=0.75±0.09 (stat) ±0.04 (syst))
NBN
B
NB+
NB
NBN
B
NB+
NB
sin21 = 0.82 0.12 (stat) 0.05 (sys)
BELLE : Measurement of sin2 (=sin2
1
1
sin2=0.78±0.08
Where do we stand ?
CP Violation established in the B sector
Measurements compatible with SM
H.Lacker et al.
At present, B Physics alone allows to establish a non flat UT and its orientation
With all available information,
8234
5012sin
8905902sin
γ
.α
..β
Essentially no change on the constraints for sin2 and
These measurements are nowof prime importance to probe the
CKM sector of the SM
CP asymmetry in D*+D*- and D*+D-
D*D*
Ntag = 76Purity = 80%
D*DNtag = 85Purity = 52%
BBAABBARARBBAABBARAR
56 fb-1
)]tmcos(C)tmsin(S1[4
e)t(f dfdf
)/t(
b d
d
Wu,c,t
B0
g c
gluonic penguins
b cd d
W
B0
tree diagram c
dc
d
D(*)+
D(*)-
D(*)+
D(*)-
Less clean than “golden modes”as penguins may interfere witha new weak phase
Further complications:
In D* D* , final states has in principle both CP+ and CP- contentSf is dilutedIn D* D , 2 interfering amplitudes AD*D and ADD* may have different magnitudes(note: if one uses HQET+factorization AD*D ADD* and SD*D = SDD* sin2)
Direct CP violation sinsins
Decay x mixing “sin2”
no s quarkinvolves
D*+D-
S+- = -0.43 1.41 0.20 C+- = 0.53 0.74 0.13 D*-D+
S-+ = 0.38 0.88 0.05 C-+ = 0.30 0.50 0.08
… Expect 10-fold increase in statistics over the next 4 years
BABAR : RBABAR : Rtt = 0.22 = 0.22 0.18 0.18 0.03 0.03 S S 0.56 x “sin2 0.56 x “sin2” ” ((neglecting penguins)
An angular analysis allows one to measures the CP odd width in D*D*
D*D*
S = -0.05 0.45 0.05 C = 0.12 0.30 0.05 BABARBABAR
No sensitivity yet for observing CP violation but …
Measurements of
C 0 Direct CP violationS = sin2eff sin2
need to relateasymmetry to
via model
Decay distributions f+(f-) when tag = B0(B0)
1
||1
||1
||1
)Im(2
22
2
2
2
ff
f
f
CS
C
S
For additional weak phase
Measurement of “sin2”
b d
d
Wu,c,t
B0
g u
gluonic penguins
b ud d
W
B0
tree diagram
u
du
d
+
-
+
-
)]tmcos(C)tmsin(S1[4
e)t(f dfdf
)/t(
i2f
)(i2f
f
f eeAA
pq
C 0, S = sin2
12
icb
iub
icb
iubi
eAeA
eAeAe
For single weak phase
BBNS
Charmless B decays needed
Results from B0 (with 55fb-1)
“sin2”= -0.01 ±0.37(stat) ±0.07 (syst))Other modes studiedas well e.g. B->
CL%90
0.480.54,- 0.07(syst) 0.29(stat)0.02- )C(
0.620.66,- 0.07(syst) 0.37(stat)0.01- )S(-
-
ππB0
~83 B+-
πKB0
~356 BK+-
Preliminary Results
(~83 candidates) before tag
“sin2”= -0.01 ±0.37(stat) ±0.07 (syst))
S = [-0.63,+0.60]
coscos
sinsin222
cbubcbub
cbub
AAAA
AAC
)22sin( penguinS
BBNS
To extract sin2 either :
Isospin analysis using B 0 and B0 00
or
requires using theory
CL%95
1.0.30, 0.09(syst) (stat)0.94 )C(
0.391.,- (syst) (stat)1.21- )S(0.25
0.31--
0.160.13-
0.380.27-
-
“sin2”= -1.21 +0.38-0.27
(stat) +0.16-0.13
(syst))
BELLE results on B0 (with
41.8fb-1)
Observe large difference in B0 and B0 ratesand times dependence
(73.513.8 candidates) before tag
Direct and mixing induced CP
Comments on B0
BABAR results compatible with factorization (BBNS …)
BELLE at ~1.4 from S2+C2 < 1 bound C large (may be first evidence of Direct CP violation in B system but requires - very large penguins P/T 1 ( should be seen soon) - large strong phase (not so compatible with BBNS)
Both results marginally compatible (C and S each at ~2
… definitely more statistics is needed, first Rendez Vous this summer
Direct CP Violation ?
sinsin
sinsin
No Evidence forDirect CP violation … yet!
~pure penguinmodes
Summary
The B factories KEKB and PEPII have started remarkably well with luminosity surpassing design values
The detector BABAR and BELLE are working well and have established CPviolation the the B meson sector
sin2=0.78±0.08BABAR + BELLE
not enough statistics to do the comprehensive study of CP violation yet… but near future prospects looks very promising
However, a lot remains to do : Measuring the other angles of the UT Direct CP violation still to be seen errors on T violation need to be reduced
Many other measurements on Vcb, Vub, Vtd to come as well as searching for supersymmetry in rare B decays (e.g. b->s …)
What ’s next ?
BABAR has already ~85 fb-1 (i.e. x1.3 the statistics presented this winter)and will continue until end June 2002 ( ~100 fb-1 on+off resonance).BELLE has very similar plans and goals (i.e ~ 100 fb-1 on+off this summer)
0S
0 KB
sssb DDB0
dccb
Increase statistics in Golden modes 12sin fb10008.0 for
12sin fb10008.0 for
Many other CP modes can potentially provide independent measurement of sin2
different quark processes various penguin contributions angular analyses for VV modes
New charmonium modes will added (e.g. cKs …)
*0 DD,DDB 0S
0S
0 K,KB
Perspectives for sin2 ?
Perspectives for sin2 ?
with increased statistics onlywith10025.0 1"2sin" for fba onlywith10025.0 1"2sin" for fba
should be observed and isospin analysis may start to be possible
Other modes such as should come into the game with similar sensitivities as
Perspectives for measuring D* decays to extract sin(2)
CPV in mixing/decay clean theoretically,
pure tree amplitudes – no penguin pollution …but time-dependent CP asymmetries at the few % level
D*K decays to extract interference with
(DCS) πDBπDB ** 00
Original construction by Gronau & Wiler +
Dunietz
CP00 fD,D
Both methods are Extremely challenging
experimentally!
22s
07.008.000
00
24.016.0)()(
)()(
KDBBrKDBBr
KDBBrKDBBrA
CPCP
CPCPCP
04.024.022.0
05.026.029.0
)()(
)()(00
00
KDBBrKDBBr
KDBBrKDBBrA
KDB 0 KDB 0
BABARBABAR
BELLEBELLE
BELLE (29 fb-1)
Mode B(x10-5)
GeVρ γ ρ
GeVπ γ(892)π
(1430)γ
(892)γ
(892)γ
inclusive γ
0.2)(7.15.6
0.2)(9.01.16.5
10.066.026.1
46.083.3
36.043.4
2.43.56.33
1.12.1
**
*2
0
*
0*0
0.54.5
KmKB
KmKB
KB
KB
KB
XB S
Radiative B decays Penguin loop for non-SM
particles Probe for new physics BELLEBELLE
<BaBar+Belle+PDG>
BELLEBELLE
Inclusive B Xs one energetic photon E> 2 GeV
Xs : one K or KS plus 1 to 4 pions
BABARBABAR
Electroweak Penguin decays
Very interesting to search for new physics possibly leading to large CP violation effect
In SM, Br is expectedin the (0.2-0.5)x10-6 range for Kllin the (0.8-2.2)x10-6 range for K*ll
New Ali et al. predictions are lower!
BELLE (29.1 fb-
1)BELLE (29.1 fb-
1)
Mode Yield Signif. B(x10-6) Theory
6.7-5.7μμ
2.38.4ee
1.9-1.0μμ
0.6-0.3μμ
2.3-1.4ee
0.6-0.3ee
9.197.24.11
2.100.3
0.38.2
99.08.45.9
1.51.25.5
2.16.2
1.58.4
9.43.4
9.21.2
*
13.039.015.032.0
7.31.3
7.30.3
*
7.20.2
S
S
XB
XB
KB
KB
KB
KB
CL%90at108.3)(B
10)26.094.1()(B
10)08.084.0()(B
6
611.174.0
631.025.0
K
K
K
B i.e.BB
625.021.0 10)09.075.0()(B
KB
B+ K+ +–
B0 KS +–
Combined
Electroweak Penguin decays (cont’d)
619.016.0 10)09.079.0(
)(B
BELLEBABAR
KBBABAR (54.6 fb-1)BABAR (54.6 fb-1)
CL)%90(101.2)(B
CL)%90(101.2)(B
CL)%90(103.3)(B
7
7
7
e
ee
BBB
NoteAlso :
Luminosity projections and prospects for KEKB and PEPII
Luminosity projection (baseline)
0
200
400
600
800
1000
1200
1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009
Year
Inte
gra
ted
Lu
min
os
ity
(/f
b)
Luminosity
PEPIIPEPII
Upgrade toward 1035 under consideration
KEKBKEKB
KEKBKEKB
650 fb-1 in 2007
Similar studies going on for PEPII
CP Reach extrapolations at BABAR
Conclusion
CP Violation is now established in the B sector and sin2= 0.78 0.08… it is consistent so far with the prediction of the SM
The Challenge of the Asymmetric B Factories has been met.Both machines and detectors are operating beautifully, surpassingthe anticipated performance
Most results on B physics are more precise than the world averagei.e. the comprehensive study of the CKM sector has started
Still a lot of work ahead of us but very exciting time both for experimentalists and theorists for getting new ideas as it becomes possible to probe them now
with the hope that it will unravel inconsistencies of the SM andpoint toward new physics as CP in the SM is unable to account quantitatively for Baryon Asymmetry of the Universe