Download - Rare Hadronic B Decays
1
Rare Hadronic B Decays
John Fry
Lepton Photon 2003
John Fry Lepton Photon 2003 2
Scope of Talk
• To present updated branching fractions (BF) and CP asymmetries (ACP) for rare (charmless) B decay modes
• To show how BF and ACP are used with theoretical models to put constraints on the Standard Model and to search for New Physics.
NB: All results are preliminary unless referenced.
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How Good is the Standard Model?
A. Hööcker et al, Eur. Phys. Jour.
C21 (2001) 225, [hep-ph/0104062]
K [K] and B sectors [md,Vub , Vtd , Sin (2)]consistent with each other and SM (theory)
LEP Coupling Constants
CPLEAR• T consistent with CP• Tight CPT constraint
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Motivation for Rare Decays
• SM is a very good approximation to reality
Hence
• Need to consider processes where is small in order to be sensitive to new physics.
• Hence processes dominated by penguin loops, or CKM - suppressed decays
NPSMCommon AA
SMA
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Procedure
• Compare nature (precise, experimental measurements) with SM (theoretical models) for sensitive quantities.
• Agreement gives an alternative route to (, ) and additional constraints on the unitarity triangle.
• Disagreement means:– New Physics …. OR
– Refinements needed to theoretical calculations … ….AND Model-independent calculations needed
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The (theoretical) Problem
BM1
M2
How to go from here …
to branching fractions and CP asymmetry
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Classes of theoretical calculations
• QCD Factorisation (mb >> QCD)
Amps factorise to LO ( / mb), all orders S
Naïve factorisation recovered in LO
• PhenomenologyAmplitudes of dominant processes related to
measured BF and each other via SU(3)
• Model “Independent”Isospin & minimal dynamical assumptions
bounds on deviations from SM
Beneke, Buchalla, Neubert & SachrajdaNucl Phys B606 (2001) 245Beneka & Neubert Hep-ph / 0308039
Chiang, Rosner Phys Rev D65 074035Chiang et al Hep-ph / 0307395Lipkin Phys Lett B254 (1991) 247
Grossman, Ligeti, Nir, QuinnHep-ph / 0303171
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Visualising QCD Factorisation
+B
m
M
B
M
m
<MmQB> = FBm T * fM M + FBM T * fm m + T fB B * fM M * fm m
TTF
BM
m
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Pictorial Phenomenology
+B
m
M
B
M
m
TTF
+
Leading Order – Naive Factorisation
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Direct CP ViolationCP asymmetry occurs if the decay B f ( and its charge conjugate) is mediated by two amplitudes with different strong and weak phases:
)cos()cos(2
)sin()sin(2
12122122
21
12122122
22
)(2
)(1
)(2
)(1
2211
2211
aaaa
aa
aa
aaA
eaeaa
eaeaa
ff
ff
CP
iif
iif : strong phase CP-even
: weak phase CP-odd
Naïve Expectation:ACP small for K (0+) Dominant penguin (tree)ACP large for -+ Unless dynamically suppressed
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Overview of B Production and Decay
z
ee
S4
K
0recB
Inclusive Reconstruction B-Flavor Tagging
Exclusive B Meson Reconstruction
CP eigenstates
Flavor eigenstates
PEP-2 (SLAC)
0tagB
Flavor eigenstates Resolution function and Tagging
Signal: Branching fraction; ACP; CP Analysisflavrec BB
Signalrec BB
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Signal Selection
2*2beamES
*BpEm *
beam* EEE B
(mES) 2.6 MeV/c2 (E) 20 MeV
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Discrimination of B and Continuum
Combine into a Fisher (or NN)
Signalu,d,s,cbackground
Fisher Discriminant
Arb
itra
ry U
nit
sMonte Carlo
B produced (almost) at rest in Y(4S) frame
Isotropic B Jetty Continuum
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Search for B0 → p pbar @ BaBar
p
K e
Use the DIRC to reject K, , e,
C.L.) %90( 107.2)(r 70 ppBSmallest upper-limit BF in B0/Bdecays!
C.L.) %90( 5.7
syst)(stat)(3.0 0.12.1
1.30.2
SN
Signal Eff = 91%Background Eff = 3%
Total signal efficiency = 37%
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Summary of BF (10-6) for K, and KKMode BaBar Belle CLEO Average
K+ - 17.9 0.9 0.7
18.5 1.0 0.7 18.0 2.3 1.2 18.1 0.8
K0 + 17.5 1.8 1.3
22.0 1.9 1.1 18.8 3.7 2.1 19.6 1.5
K+ 0 12.8 1.2 1.0
12.8 1.4 1.2 12.9 2.4 1.2 12.8 1.1
K0 0 10.4 1.5 0.8
12.6 2.4 1.4 12.8 4.0 1.7 11.2 1.4
+ - 4.7 0.6 0.2 4.4 0.6 0.3 4.5 1.4 0.5 4.6 0.4
+ 0 5.5 1.0 0.6 5.3 1.3 0.5 4.6 1.8 0.7 5.3 0.8
0 0 2.1 0.6 0.3 1.7 0.6 0.3 < 4.4 1.90 0.47
K+ K- < 0.6 < 0.7 < 0.8 < 0.6
K+ K0 < 1.3 < 3.4 < 3.3 < 1.3
K0 K0 < 1.6 < 3.2 < 3.3 < 3.2
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HFAGJ Smith (Colorado)J Alexander (Cornell)
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Belle
Belle
Belle152 106 BB140 fb-1
Signal 3.4 25.6
BF (10-6)1.7 ± 0.6 ± 0.2
+9.3 -8.4
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BaBar 0 0
Sub to PRL
BaBar124 106 BB113 fb-1
Signal 4.2 46 ± 13 ± 3
BF (10-6)2.1 ± 0.6 ± 0.3
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BBNS NPB606 (2001) 245
Inconsistent ?
Data (2001)
Data (2003)
QCD_F: Ratios of & K BF’s
0.42 ± 0.11
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Comparison of BF and ACP with Theory‡
Mode BFExp
(10-6)
BF pQCD
(10-6)
ACP Expt
(%)
ACP pQCD
(%)
ACP QCDF
(%)
K+- 18.2 ± 0.8 13 – 19 -9 ± 3† -13 – -22 +5 ± 10
K0+ 19.6 ± 1.5 14 – 26 -1 ± 6 -0.6 – -1.5 0 ± 1
K+0 12.8 ± 1.1 8 – 14 0 ± 7 -10 – -17 +7 ± 10
K00 11.2 ± 1.4 8 – 14 3 ± 37 -3 ± 4
+- 4.55 ± 0.44 6 – 11 16 – 30 -6 ± 13
+0 5.3 ± 0.8 2.7 – 4.8 -7 ± 14 0 -2 ± 5
00 1.90 ± 0.47 0.33 – 0.65 45 ± 60
† Belle: -8.8 ± 3.5 ± 1.8 BaBar -10.7 ± 4.1 ± 1.2
‡ Keum and Sanda hep-ph/0306004Beneke and Neubert hep-ph/0308039
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Belle
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Disentangling the Bh+h- contributions (I)
B h+h- from hadronic triggerIncludes Bd BsKK, BsK ,
and Bd K
Monte-Carlo plot below shows:Bd Bs K+K- Bs K± ±,
& Bd K± ± (From Monte-Carlo)all pile up in the same region
Must disentangle contributions from each mode To do this we use:-Kinematical variable separation M vs =(1-p1/p2)q1
-dE/dx based K and identification
CDF
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Disentangling the Bh+h- contributions (II)
M vs a for each Bh+h- mode dE/dx calibration using D*± D0, D0 K±± ( from D* unambiguously distinguishes K, from D0)
Sanity check: Measure Ratio of Branching RatiosCDF : (Bd -)/(Bd K+-) = 0.26 ±0.11±0.055, PDG: 0.13 0.010.29
0.12 0.02
Yield for each mode:Bd Bd K± ±Bs K± ±Bs K+K- (stat) (stat)First observation !
Method works ! Confirmed by Sanity check against ratio of branching ratiosHave first observation of Bs K+K-Its a CP Eigenstate: Can use thisTo measure s as well !!
CDF
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Disentangling the Bh+h- contributions
(Blessed CDF results)
• ACP(BdK = 0.02 ± 0.15(stat) ± 0.017(syst)
• BR(Bd/BR(BdK=
0.26 ± 0.11(stat) ± 0.055(syst)
• fs X BR(BsKK)/fd X BR(BdK) =
0.74 ± 0.20(stat) ± 0.22(syst)
•Yield of BsKK = 90 ±17(stat) ±17(syst) events
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Is Rescattering Important?
• Could modify branching fractions and CP asymmetries in and K decays, complicating extraction of and
• KK decays are more sensitive to rescattering– Could have significant enhancement through (for example) DD
or intermediate states
0K
K0 u
u
su
sd
u
d
BaBar P_QCD*
K+K- <0.6 0.05
K+K0 <2.2 1.7
K0K0 <1.6 1.8
BF(10-6)
No sign of rescattering (FSI) yet
*Chen and Li, Phys. Rev D63, 014003 (2000)
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BF & ACP for B , K, , KMode BF (10-6)
(BaBar)BF (10-6) (Belle)
ACP % (BaBar)
ACP % (Belle)
B0 → ρ+ π- 22.6 2.8 29.1 6.4 -11 7 -38 21
B0 → ρ+ K- 7.3 1.8 15.1 4.1 19 18 22 23
B0 → ρ0 π0 < 2.5 6.0 3.1
B+ → ρ+ π0 11.0 2.7 23 17
B+ → ρ0 π+ 9.3 1.3 8.0 2.3 -17 11
B+ → ρ0 K+ < 6.2 < 12
B0 → ω K0 5.3 1.4 < 7.6
B+ → ω K+ 5.0 1.1 6.7 1.4 -5 16 6 20
B0 → ω π0 < 3
B+ → ω π+ 5.4 1.1 5.9 1.5 4 17 48 23
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Belle B , K
K+
+
KS
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BaBar: B K Dalitz Plot
B+ K*0(892)+, K*0K+ -
10.3±1.2+1.0
B+ f0(980)K+, f0 + 9.2±1.2+2.1
B+ c0 K+, c0 + 1.46±0.35±0.12
B+ D0+, D0 K+ - 184.6±3.2±9.7
B+higher K*0+, K*0K+-
25.1±2.0+11.0
B+ 0(770)K+, 0 + < 6.2
B+ K+ - + (non resonant) < 17
B+ higher fK+, f + <12
-5.7
-2.6
-2.7
K*0(892)K*0(higher)D0
ρ0
f0(980)
c0
56.4 fb-1
Branching Fractions 10 -6
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Belle: Dalitz Plot Amplitude Analysis140 fb-1 B+ K+K+K- (Signal 1400) and K++ - (Signal 2584)
Resonances: K++ - K*(890), K*(1430), (770), c0(3400), f0(980), X(1350)K+K+K- (1020), C0(3400), X(1500)
Background parameterisation – fitted with large (7*) sideband sample
)()( * BWKBWeAk
skBG
ij
Signal parameterisation – fix masses, widths except X, f0
sNon
ppR
iRSignal e
s
ae
s
aeaA R
Re23
2
12
1 21
Fit to signal + background and determine amplitudes and phases
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Belle DP Mass and Helicity Projections K
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Belle Branching Fractions from Dalitz Plot
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HFAGJ Smith (Colorado)J Alexander (Cornell)
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Longitudinal Polarisation B → V V
fL = L /
100% Pol CP evenExpect: fL ~ 1 – O(M2
V/M2B)
B0 + -
NS = 93 ±22±9BaBar [> 5]
Cos(1) MES
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BelleB + 0
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B → ρ ρ and ρ K* [BaBar & Belle]
(Errors approximated)
BF (10-6) ACP % Long. Poln %
B0→ ρ0 ρ0 < 2.1 (90 % CL)
B0→ ρ+ ρ- 27 ± 7 ± 6 99 ± 7 ± 3
B+→ ρ+ ρ0
Belle
22.5 ± 5.7 ± 5.8
31.7 ± 7.1 ± 6.7
-19 ± 23 ± 3
0 ± 22 ± 3
97 ± 7 ± 4
95 ± 11 ± 2
B+→ ρ0 K*+ 10.6 ± 3.0 ± 2.4 20 ± 32 ± 4 96 ± 15 ± 4
• CP asymmetries consistent with zero
• Polarisation in agreement with expectation
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Why we need Theorists
K0++0
3* ~ udubVV2* ~ cscbVV
Mode CKM (fdecay)2 Ratio Exp Ratio BF (10-6)
K0+ 1 1 1 1 19.6
K*0+ 1 1.85 1.85 0.65 12.7
+0 2 0.66 0.03 0.27 5.3
+0 2 1.71 0.085 0.46 9.1
+0 2 2.9 0.145 1.35 26.4
The VPSTE effect (Form factor corrections at 40% level)
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The unique decays B 0 0 and 0 0
Grossman Quinn boundPRD 58 (1998) 017504
BF give model-independentlimits to the CP angle
)(
)(;
)(
)()(sin
0
000
0
0002
BBF
BBFor
BBF
BBFEff
)%90(55.045.055.4
45.09.1)(sin 2 CLEff
)%90(10.0827
1.2)(sin 2 CLEff
| - Eff| < 50o () and < 20o () at 90% CL
+ - is dominantly longitudinal polarised, CP-even final state
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B K(*) BaBar & Belle
q
q
s
s
u u
B+,0
K(*)
Mode BF (10-6) ACP (%) Polarisation %
K0 7.6 ± 1.4 9.0 ± 2.2
K+ 10.0 ± 1.0 9.4 ± 1.3 4 ± 9 1 ± 13
K*0 11.2 ± 1.5 10.0 ± 1.8 4 ± 12 7 ± 16 65 ± 7 43 ± 10
K*+ 12.7 ± 2.4 6.7 ± 2.2 16 ± 17 -13 ± 31 46 ± 12
• Expect similar BF all modes
• BF(+) < 4 10-7 [90% CL]No indication for rescattering – as KK
•Polarisation unexpectedly small
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Belle
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BR(B±K±) at CDF
• BR(B±K±) /BR(B±J/K±) = 0.0068 ±0.0021 (stat.) ± 0.0007 (syst.)
Using PDG 2002 for BR(B±J/K±):
• BR(B±K±) = (6.9 ± 2.1 (stat.) ± 0.8 (syst.)) x 10-6
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B (')K(*) and ('), BaBar and Belle
Mode BF (10-6)
Belle BaBar
K+ 5.3 ± 1.9 2.8 ± 0.8
K0 < 4.6
' K+ 78 ± 11 76.9 ± 5.6
' K0 68 ± 13 55.4 ± 6.6
+ 5.4 ± 2.1 4.2 ± 1.0
' + < 7 2.8 ± 1.33.4
0 < 5.5
Mode BF (10-6)
Belle BaBar
K*+ 26.5 ± 8.4 25.7 ± 4.2
K*0 16.5 ± 4.8 19.0 ± 2.6
' K*+ < 90 < 12
' K*0 < 20 < 6.4
+ < 6.2 10.5 ± 3.44.8
' + 14.0 ± 5.43.8
' 0 < 14
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Theoretical background: (') K, K * modes
Similarly for K 0, K *0 except no external tree
K, K*enhanced
K, K*suppressed
Interference
Flavour singlet diagram:
Also important for K*
CKM suppressed
H Lipkin Phys Lett B254 (1991) 247
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B (')K(*) and , BaBar and Belle
Mode ACP (%)
Belle BaBar
K+ -32 ± 22
K0
' K+ -2 ± 7 4 ± 5
' K0
+ -51 ± 20
Mode ACP (%)
Belle BaBar
K*+ 15 ± 14
K*0 3 ± 11
' K*+
' K*0
+ 6 ± 29
Large asymmetry predicted for + , small for +
Chiang, Gronau, Luo, Rosner and Suprun [hep-ph/0307395]
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HFAGJ Smith (Colorado)J Alexander (Cornell)
John Fry Lepton Photon 2003 49
HFAGJ Smith (Colorado)J Alexander (Cornell)
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How does theory stack up?
• Good phenomenological understanding of Branching Fractions for 2-body PP and PV decays
[Chiang et al hep-ph/0307395; Beneke et al hep-ph/0308039; Keum et al hep-ph/0306004]
• Factorisation models give insight into dynamics, but:– BF for 0 0 looks to be in disagreement with all predictions– BF for K, ' K, K* final states underestimated in QCDF[Annihilation contribution may be too large Aleksan et al, hep-ph/0301165]
• Asymmetry data is not yet precise enough to test models
• There is still a considerable role for model-independent theoretical calculations
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When is it safe to claim New Physics?
For B0 KS, 'KS, K+K-KS we expect to measure:
S = sin(2) + , C = , where = O (2)
If S and C are measured precisely (S, C << 2 = 0.05)
Claim new physics if: |C| > 5, or |S- sin(2)| > 5
might be enhanced: Grossman bounds using isospin
u, cb s
)( 2*
*
Oa
a
VV
VVc
u
cscb
usub
relations and ratios of BFs.(K+K-KS) 0.2, ('KS) 0.5
GLNQ Hep-ph / 0303171
Must measure 20 BFs preciselyto improver the limit on !u-amplitude might be large
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Summary – What have we learned?
• Precision measurements of branching fractions are testing factorisation models – to destruction??
• Precise measts of ACP will enable further tests of models. Is there a hint of a signal in K+- ?
• B K, K*,'K, 'K* are now almost understood, but polarisation << 100% in K* is a puzzle
• Measuring the BF for 0 0 is a triumph, but the value is surprisingly high. Increased focus on 00 for | - eff|
• Measurement of many more decay modes is needed to make model-independent tests of NP meaningful
• The expected increase in luminosity of the B Factories promises a continuing, rich harvest of physics