6/4/2004 1
Particle Physics 2004Birmingham5th-7th April
Adrian Bevan
Physics at the B-factories
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• Current generation of B-factories
• CP Violation Studies: , ,
• Rare Decays
• New Particle Searches
• Physics
• Conclusions
Talk Outline
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The B-factories• PEP-II and KEK-B at SLAC and KEK, respectively• Collide e+ and e- with a 10.58 GeV CM energy• Detectors: BaBar and Belle• Started data taking in 1999
•9GeV e- on 3.1GeV e+ (4S) boost: =0.56
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)MeV(ME )S4(CM (4S) decays into B+B- or B0B0
•Cross Sections at (4S): 1.1
1.3
, 0.3
1.4
bb nb
cc nb
dd ss nb
uu nb
“continuum background”
thresholdBB
(4S)
off-peak
0 0
( (4 ) )1.04 0.07 ( 2003)
( (4 ) )
BF S B BPDG
BF S B B
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BaBar
SVT
DCH
DIRC
EMCIFR
SOLENOID
e+
e-
Belle
The Detectors
Differences between BaBarand Belle are small
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Peak Lumi: 8.16×1033 cm-2 sec-1
Number of B pairs approx: 200×106
run
1
run
2
run
3
run
4
Peak Lumi: 12×1033 cm-2 sec-1
Number of B pairs approx: 220×106
Data Samples
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Why is CP Violation so important?• Matter/anti-matter asymmetry in the universe requires CP Violation
known level of CPV is 109 times too small for cosmology
• Standard Model describes all CPV with a single complex phase
need to test
• Flavour physics BSM has many parameterscan search indirectly for new physics and try to
(further) constrain models before the LHC
CP Violation Studies:
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The couplings, Vij, form a 3×3 matrix: The CKM Matrix;
CP Violation in meson decay
32
2 2
23
4
(1 / 2 )
(1 1)
1 / 2 ( )
A i
i
V A
AA
O
Understanding Standard Model CP Violationmeans accurate measurements of and
V , ,iq u c t
, ,jq d s b
W
ijV
~ 0.22
~ 0.8
~ 0.2 0.27
~ 0.28 0.37
A
Wolfenstein Parameterisation:
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| |
| |
itd td
iub ub
V V e
V V e
mixing0 0B B
* * * 0ud cd cub tdb tbV V V VV V
(1,0)(0,0)
(,) *
*td tb
tcd cb
V VR
V V*
*ub ud
bcd cb
V VR
V V
* , ,
,...
B D DK
K
, ,B
0
* *
/ ,
, ,...
SB J K
D D K
The Unitarity Triangle
SM Predicts a closed triangle withtwo independent phase angles: &
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• Three observable interference effects:
– CP violation in mixing:
– (direct) CP violation in decay
– CP violation in interference of mixing and decay (Im ≠ 0)
0 0 0 0Pr( ) Pr( )B B B B time dependent effect
time dependent effect – relevant formeasuring CKM angles!
CP violation at the (4S)
0 0Pr( ) Pr( )B f B f time integrated effect – number counting
0B
0B
f
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00
0 0
( ( ) ) ( ( ) )( )
( ( ) ) ( ( ) )
sin( ) cos( )
physphysCP
phys phys
B t f B t fA t
B t
S m t C m
B f
t
f t
Analyse time evolution of BB system (assume ):
Indirect CP violation S ≠ 0
Direct CP violation C ≠ 0
00
4
( / / , )
1 sin( ) cos( )
phys
td d
f B B f f t
e n m t nCS m t
0 01( 1) for ( )n B B
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(1,0)(0,0)
(,)
* , ...B D DK
,B
0
0 0 0
/ ,
, ...
S
S
B J K
K f K
Measurements Related to the angles of the Unitarity Triangle
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The CKM Angle :
Precision measurement of from bccs Perfect agreement with the SM Prediction
Alternate measurements of probe NP at TeV
scale
sin 2 0.736 0.049 (Belle & BaBar)
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B0 K0The CKM Angle :
• Rare Decay
• loop or “pure penguin”
• sensitive to new physics
• measured in this mode should agree with
• So in SM:
0( / )Sb ccs J K
sin 2 , 0s sK KS C
[sin 2 ( ) 0.736 0.049]b ccs
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( )b sss
106 candidates
(from 152×106 B pairs)PRL. 91 (2003) 261602
B0 K0S
0.96 0.50 0.10
0.15 0.29 0.07
S
C
3.5 deviation for S in KS
Belle Claim “evidence for new physics”
SM=+0.74
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B0 → K0
120 M BB
BaBar Result consistent with SM
Preliminary
hep-ex/0403026, submitted to PRL
B0 → KL
B0 → KS
0.320.360.47 ( ) 0.06( )
0.01 0.33( ) 0.10( )K
K
S stat syst
C stat syst
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The CKM Angle :
ccs
new hep-ex
new result
new result
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The CKM Angle :
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CP Violation in B→hhh
0
sin(2 )
C
S
Tree Level: +Loops (penguins)
u,c,t
W
2eff
sin( )
1 sin(2 )
C
S C
measure eff
need to bound |eff-| (shift from loops) different |Penguin/Tree| for different decays
:tdV
* :tdV
:ubV
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0.40 0.22 0.03
0.19 0.19 0.05
0.107 0.041 0.013K
S
C
A
Presented at LP ‘03 results for S and C124×106 B pairs
0B
0B
266 signal events
-A= -0.58 0.15 0.07 = CS= 1.00 0.21 0.07
LR
0B0B
Observation of CPVEvidence for DCPV
152×106 B pairs372 signal events
preliminaryhep-ex/0401029
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Isospin Analysis: need B+-, +0 and 00 limiting factor is B→
• Small signal BR• qq and background
Significance including
systematic errors = 4.2
0 0
1413
0 0 0 6
46 3
( ) (2.1 0.6 0.3) 10
N
BR B
PRL 91 (2003) 241801
124×106 B pairs
0| | 48
(90% . .)
eff
C L
Can’t do Isospin analysis in without a super B factory
Stuck with model dep. interpretation in
6/4/2004 22
B
0
6
(30 4 5) 10
(BaBar)
0.99 0.03 0.04L
B
BF
f
run 1+2
0 0
6
0.050.07
(26.4 6.4) 10
(Belle & B
0.96
aBar)
L
B
BF
f
0 0 0
6
(Ba
2.1 10 (90% . .
r)
)
BaB
BF C L
| | 13 (68% )eff CL Penguins are small in B
No observation published prior to last year now have measurements of all modes
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Preliminary Result
96 10 4 13stat syst theory
Isospin analysis gives:
0.19 0.33 0.11
0.23 0.24 0.14
long stat syst
long stat syst
S
C
run 1+2+3B
0B
0B
• ~113/fb• 314 signal events
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The CKM Angle :
2 of many methods under study: Full & Partial reconstruction of BD(*): sin(2+)
5207 ± 87 signal
4746 ± 78 signal
Full Reconstruction
82/fb
using 78/fbOnly consider D* with l or K in other B
O(50%) purityuse hard pion from B decay and soft pion from D* decay.No low efficiency from D0 reconstruction
hep-ex/0308048 & hep-ex/0310037 (BaBar)hep-ex/0308048 (Belle)
Partial Reconstruction
High Purity Lower Statistics
lepton kaon
6400 signal 25160 signal
Preliminary
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sin(2+) > 0.87 (68% CL)
sin(2+) > 0.58 (95% CL)
Combining results of both BaBar methods
Preliminary
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Direct CP Violation• Interference of diagrams with different strong and weak phases• ’ in kaon system only observed manifestation
Only hint from Belle’s +-
Need More Data
( ) ( )
( ) ( )CP
Br B f Br B fA
Br B f Br B f
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Measurements Related toSides of the Unitarity Triangle
(1,0)(0,0)
(,) *
*tb
tc
td
cd bV
VVR
V*
*ud
bc
ub
cd bV
VVR
V
b s
semi-leptonic B decays
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Use model from Gambino and UraltsevMeasurement of Vcb from semileptonic B decays
8 parameter fit includes: |Vcb|, BR(XCe), mb and mc
GeVGeVm
GeVGeVm
eXBBr
V
c
b
c
cb s
)02.006.007.018.1()1(
)02.004.005.061.4()1(
)%06.016.061.10()(
10)6.02.04.04.04.41(||
s
s
SL
HQEexp
HQEexp
HQEexp
3HQEexp
B(B→Xclν), |Vcb| and mb determined with
precision of 2% or better!
hep-ex/0403031, hep-ex/0403030Thanks to Henning Flaecher Preliminary
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B → K*• Acp ≤1% in SM.
• SUSY can enhance to ~20%
Reconstruct ~1150 signal in: ss KKKKK ,,, 00
88×106 B pairs
*K K CPA
preliminary
e.g. MSSM constrainthep-ph/0303043
(Ellis et al)
*B K WMAP
excluded by th.
Preliminary
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Non CP/UT physics from BaBar
Too much physics activity to do justice to all areas: We have work published/under study in many areas including:
• New Particle Searches• Rare B decays• Direct CP Violation Searches • physics
lots more areas under study that I don’t have time to discuss.
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New Particle Searches• Last Spring from BaBar:
discovery of cs state: DsJ(2317)evidence for Ds(2458)
• Ongoing work searching for Pentaquarks
revitalised charm meson spectroscopyBelle and CLEO confirmed this discovery
led to improvement in theoretical models State was found below DK threshold (previously assumed to be above threshold)
Now have many BDsJX branching fractions
See: 2317: Phys.Rev.Lett. 90 (2003) 242001 105 citations! 2458: Phys.Rev. D69 (2004) 031101
0SD K K
SD K K
data favour JP=0+
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Belle Observe BXSll, XS=K, KSfrom Iwasaki’s talk at
http://moriond.in2p3.fr/EW/2004/
• 72 Signal Events• 6.2 significance• 140/fb, 152×106 B pairs
*B K llAlso study where BF~7×10-7
• Rare Decay (FCNC)• Sensitive to NP
(results available from both expts)
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Physics: Overview
= 290.8 ± 1.5stat ± 1.6syst fs lifetime: 30/fb
LFV decay searches: 91.5/fb
6( ) 2.0 10 (90% C.L.)BF
Rare decays
6(56 10 pairs)
signalbox
Preliminary
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• BaBar has first measurement of from B
• Belle Observes CPV in B & sees hint of Direct CPV
• Starting to test closure of the Unitarity triangle
• Everything measured so far consistent with SM
• Searching for New Physics at higher order: looking closely at bs penguins: new measurements of
• Will have ~200-250/fb per experiment for ICHEP ’04 (approx ×2-3 increase in stats over results shown)
Conclusions
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sin(2 )
cos(2 )
sin(2 )
Knowledge of , from direct measurementssin(2 )
B b ccs
(*)B D
/ *B J K
Constraints from:
CPV from B system is consistent with SM
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Additional Material:
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B0 → f0 K0 (CP even decay)0B
0B
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/ * (cos 2 )B J K
/ * is a VV decay - has both CP even and CP odd partsB J K• cos(2) comes from interference between helicity states
104 tagged events (KS0)
0.760.96cos 2 3.32 ( ) 0.27( )
sin 2 0.10 0.57
stat syst
0.500.79
With WA sin 2
cos 2 2.72 0.27
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b lsl• Rare Decay (FCNC)• Sensitive to NP
SM BF~7(1)×10-6 (ee) ~4(1)×10-6 ()
Ali: PRD 66 034002 (2002)Ali: hep-ph/0210183
peaking BG component from charmonium and hadronic B decays
0 or SK K
or e e
c.f. 0.02(0.20) in SMESM
Preliminary
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Isospin Analysis
)Br()Br(2
)Br()Br()Br(cos
0
00210
| |eff
0 0 0
2
0
Bsin ( )
Beff
Br
Br
Grossman Quinn bound
Also see Charles, GLSS, Buchalla et al…
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0| |/(1 ) ( )sin ( )cosX
CPt
XB X XXXf t e SA Cm t C m tS
related to
direct CPV
K is self tagging
CK, SK, SK =0, CK =-1 •large expected:
ACP() & ACP(K)
6
1.3 61.2
( ) (22.6 1.8 2.2) 10
( ) (7.3 1.3) 10
B B
B B K
0 / : Not A CP EigenstateB K
BF From Winter ’03 (82/fb)
804.2 ±49.2signal events
doing analysis in region near Dalitz Plot analysis goal
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cos( ) sin( )C m t S m t
~123106 B pairsLP ‘03 result (113 /fb)
2.4
A
A Difficult to relate to without DP analysis
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*B K ll
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0
0
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The whole picture for B-meson decay:
CP Violation in mixing: • so this is small
Direct CP Violation:• So far only seen in kaon decays• this can be a large effect in rare B decay
- Belle claim ‘evidence for’ in decay
Indirect CP Violation – CPV in interference• Need to measure the unitarity triangle angles
, ,
0 0
0 0
Pr( )1
Pr( )
B B
B B