Radiative and EW Penguin B Decays: Experimental Results · FPCP, Pasadena, June 2016 John Walsh,...

John WalshINFN, Sezione di PisaBABAR Collaboration

Radiative and EW Penguin B Decays: Experimental Results

FPCP, Pasadena, June 2016 John Walsh, INFN Pisa

Outline

• Introduction

• Radiative penguins

- B→Kππγ at BaBar- Search for B0→φγ at Belle - B0→K*ee at LHCb

• Electroweak penguins

- B→Kττ at BaBar- B→K*μμ: results from LHCb, BaBar, Belle, CMS

• Outlook

2

Many other results not presented

for lack of time. Sorry!


Introduction

• Flavour-changing neutral current process: prohibited at tree level in the Standard Model (SM) → New Physics (NP) contributions enter at same order as SM physics

• In many NP models, the SM particles in the loops are replaced by new heavy particles, new masses, new couplings → modify quantities that we can measure

- Branching Fractions, CP and Isospin asymmetries, observables from angular distributions

3

T. Blake

Exploring FCNC processes• Flavour changing neutral current transitions only occur at loop order

(and beyond) in the SM.

!

!

!• New particles can contribute at loop or tree level:

!

!

!

• Enhancing/suppressing decay rates, introducing new sources of CP violation or modifying the angular distribution of the final-state particles

2

b s

µ+

µ−ν

W− W+

tb s

µ+

µ−

t

γ, Z0

W−

b s

µ+

µ−ν

H− H+

tb s

µ+

µ−

di

γ, Z0

χ0 b s

µ+

µ−

di

H0

g b s

µ+

µ−Z ′

SM diagrams involve the charged current interaction.


Introducing Wilson coefficients...

• Effective Hamiltonian:

• Relevant operators for this physics:

• The Ci are the Wilson coefficients, which are calculable perturbatively in SM and NP models

• C7: also measured experimentally: |C7| determined by B(B→Xsγ)

• C7, C9, C10 all affected by b→sl+l-

4

Chirality-flipped, highly suppressed in SM

Radiative penguin decays: b→sγ• B→Kππγ at BaBar• Search for B0→φγ at Belle• B0→K*ee at LHCb

5


B→Kππγ overview [PRD 93, 052013 (2016)]

• In the Standard Model: left-handed quarks, right-handed anti-quarks produce left-handed photons

6

• CP violation via interference in mixing is suppressed: after mixing decay is to photon of “wrong” polarisation

• NP, can enhance right-handed photons, causing significant CP violation in the time-dependent CP asymmetry of a CP eigenstate

Standard Model:

471 x 106 BB pairs

This analysis: measure in SfCP B0 ! K0S⇢

0�


B→Kππγ overview

• Difficulty lies in isolating the CP state from the other (non-CP) B0→KS0π+π-γ final states

• Solution: measure and calculate theoretically deviation from

• Dilution factor [Hebinger, Kou, Yu: LAL-15-75 (2015)]:

• This requires an amplitude analysis,

• Performed on the isospin state B+→K+π+π-γ, which benefits from higher statistics

7

SK0S⇡⇡�

SK0S⇢0�


• Extract mKππ spectrum (sPlot technique) and perform amplitude analysis to resonant contributions to B→K+resγ: consider 5 resonances: K1(1270), K1(1400), K*(1410), K*(1680),K2*(1430).

• Use mKπ spectrum, along with Kres fractions from previous fit, to determine Kρ and K*π contributions to final state.

- Model contributions from K*0, ρ0 and (Kπ)0 s-wave (LASS parametrisation)

• We can now calculate the dilution factor:

8

m(Kππ)

m(Kπ)

471 x 106 BB pairs

B+→K+π+π-γ amplitude analysis


€

π +

€

ρ0

€

π −

€

γ

B0→Ks0π+π-γ time-dependent analysis• Add flavour tagging and Δt measurement

to usual mES fit

• Event yields and CP parameters are extracted simultaneously

• We find 243 +- 24 +- 20 signal events, yielding a total BF:

• with CP parameters:

• Applying the dilution factor, one obtains (in agreement with the SM):

9

fraction uncertainties taken from Ref. [18]. For the cat-egories describing a sum of modes, the fraction of eachmode is varied according to the relative branching fractionuncertainties taken from Ref. [18]. The misreconstructedsignal fractions are varied according to the uncertaintiesdue to the sample size of the simulated events and the signalbranching fraction uncertainties in Ref. [18]. The fixedyields of B0B0 and BþB− generic B backgrounds, describ-ing a sum of several small contributions from variousB-background modes, are varied according to the uncer-tainties due to the sample size of the simulated events. Thefixed parameters of the Δt PDFs are varied according to theuncertainties that are either taken from other BABAR

measurements or are extracted from simulated event dis-tributions. Using the method described in Ref. [36] andassuming no correlations among the fixed parameters, wecombine each of the negative (positive) difference betweenthe new fit value and nominal fit value of each of the time-dependent CP -asymmetry parameters, and take the result-ing values as negatively (positively) signed uncertainties.The corresponding values are given in Table XVI. Note thatthese uncertainties are small compared to the statisticaluncertainties.

2. Branching fraction

We take the same sources of systematic uncertainties asdescribed in Sec. IV D 3 when applicable. A few sources,which are described below, differ from the analysis ofBþ → Kþπ−πþγ decays.From the procedure described in Sec. V E 1, and assum-

ing no correlations among the fixed parameters, wecombine each of the negative (positive) difference betweenthe new fit value and nominal fit value of each of the totalsignal yield and take the resulting values as negatively(positively) signed uncertainties.

TABLE XVI. Systematic uncertainties on the time-dependentCP -asymmetry parameters resulting from the fixed parameters inthe fit to mES, ΔE, F and Δt.

Parameter þ signed deviation − signed deviation

SK0Sπ

þπ−γ 0.025 0.027CK0

Sπþπ−γ 0.027 0.022

)2 (GeV/cESm5.2 5.21 5.22 5.23 5.24 5.25 5.26 5.27 5.28 5.29

)2E

vent

s/(0

.002

3 G

eV/c

0

20

40

60

80

100

E (GeV)∆0.2− 0.15− 0.1− 0.05− 0 0.05 0.1 0.15 0.2

Eve

nts/

(0.0

4 G

eV)

0

20

40

60

80

100

Fisher Discriminant0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Eve

nts/

(0.1

)

0

20

40

60

80

100DataCorrectly-reconstructed signalMis-reconstructed signalContinuum

γs±X

γ+πS0K Generic±Bγs

0X Generic0B

γ0πS0K

γ-π+K

t (ps)∆8− 6− 4− 2− 0 2 4 6 8

Eve

nts/

(0.5

33 p

s)

0

10

20

30

40

50

60

FIG. 8. Distributions ofmES (top left), ΔE (top right), the Fisher discriminant (bottom left), and Δt (bottom right), showing the resultsof the fit to the B0 → K0

Sπ−πþγ data sample. The distributions have their signal/background ratio enhanced by means of the following

requirements: −0.15 ≤ ΔE ≤ 0.10 GeV (mES);mES > 5.27 GeV=c2 (ΔE);mES > 5.27 GeV=c2, −0.15 ≤ ΔE ≤ 0.10 GeV (Fisher andΔt). Points with error bars show the data. The projection of the fit result is represented by stacked histograms, where the shaded areasrepresent the background contributions, as described in the legend. Some of the contributions are hardly visible due to their smallfractions. Note that the same order is used for the various contributions in both the stacked histograms and the corresponding legend.

P. DEL AMO SANCHEZ et al. PHYSICAL REVIEW D 93, 052013 (2016)

052013-24

Δt

Flavour tagging

Signal B

�t ⇡ �z

��c

fraction uncertainties taken from Ref. [18]. For the cat-egories describing a sum of modes, the fraction of eachmode is varied according to the relative branching fractionuncertainties taken from Ref. [18]. The misreconstructedsignal fractions are varied according to the uncertaintiesdue to the sample size of the simulated events and the signalbranching fraction uncertainties in Ref. [18]. The fixedyields of B0B0 and BþB− generic B backgrounds, describ-ing a sum of several small contributions from variousB-background modes, are varied according to the uncer-tainties due to the sample size of the simulated events. Thefixed parameters of the Δt PDFs are varied according to theuncertainties that are either taken from other BABAR

measurements or are extracted from simulated event dis-tributions. Using the method described in Ref. [36] andassuming no correlations among the fixed parameters, wecombine each of the negative (positive) difference betweenthe new fit value and nominal fit value of each of the time-dependent CP -asymmetry parameters, and take the result-ing values as negatively (positively) signed uncertainties.The corresponding values are given in Table XVI. Note thatthese uncertainties are small compared to the statisticaluncertainties.

2. Branching fraction

We take the same sources of systematic uncertainties asdescribed in Sec. IV D 3 when applicable. A few sources,which are described below, differ from the analysis ofBþ → Kþπ−πþγ decays.From the procedure described in Sec. V E 1, and assum-

ing no correlations among the fixed parameters, wecombine each of the negative (positive) difference betweenthe new fit value and nominal fit value of each of the totalsignal yield and take the resulting values as negatively(positively) signed uncertainties.

TABLE XVI. Systematic uncertainties on the time-dependentCP -asymmetry parameters resulting from the fixed parameters inthe fit to mES, ΔE, F and Δt.

Parameter þ signed deviation − signed deviation

SK0Sπ

þπ−γ 0.025 0.027CK0

Sπþπ−γ 0.027 0.022

)2 (GeV/cESm5.2 5.21 5.22 5.23 5.24 5.25 5.26 5.27 5.28 5.29

)2E

vent

s/(0

.002

3 G

eV/c

0

20

40

60

80

100

E (GeV)∆0.2− 0.15− 0.1− 0.05− 0 0.05 0.1 0.15 0.2

Eve

nts/

(0.0

4 G

eV)

0

20

40

60

80

100

Fisher Discriminant0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Eve

nts/

(0.1

)

0

20

40

60

80

100DataCorrectly-reconstructed signalMis-reconstructed signalContinuum

γs±X

γ+πS0K Generic±Bγs

0X Generic0B

γ0πS0K

γ-π+K

t (ps)∆8− 6− 4− 2− 0 2 4 6 8

Eve

nts/

(0.5

33 p

s)

0

10

20

30

40

50

60

FIG. 8. Distributions ofmES (top left), ΔE (top right), the Fisher discriminant (bottom left), and Δt (bottom right), showing the resultsof the fit to the B0 → K0

Sπ−πþγ data sample. The distributions have their signal/background ratio enhanced by means of the following

requirements: −0.15 ≤ ΔE ≤ 0.10 GeV (mES);mES > 5.27 GeV=c2 (ΔE);mES > 5.27 GeV=c2, −0.15 ≤ ΔE ≤ 0.10 GeV (Fisher andΔt). Points with error bars show the data. The projection of the fit result is represented by stacked histograms, where the shaded areasrepresent the background contributions, as described in the legend. Some of the contributions are hardly visible due to their smallfractions. Note that the same order is used for the various contributions in both the stacked histograms and the corresponding legend.

P. DEL AMO SANCHEZ et al. PHYSICAL REVIEW D 93, 052013 (2016)

052013-24

the other shape parameters are fixed to the values deter-mined from a fit to the off-resonance data.The mES, ΔE and F PDFs for all the categories of B-

background events, given in Table XIV, are described byparametric functions, except for the Bþ → K0

SπþγB back-

ground mES and ΔE PDFs, for which significant correla-tions are present. These correlations are taken into accountthrough a nonparametric two-dimensional PDF, defined asa histogram constructed from a mixture of Bþ → K"þð→K0

SπþÞγ and Bþ → Xsuð→ K0

SπþÞγ simulated events. All

shape parameters of the B-background PDFs are fixed tovalues determined from simulation.No significant correlations were found among the fit

variables for the other event species in the fit.

3. Branching fraction determination

The branching fraction to the K0Sπ

þπ−γ final state isdetermined from the fitted yield of the correctly recon-structed signal event category, NCR

sig ¼ Nsig × fCR, theweighted signal efficiency hϵ0i, and the number of neutralB events NB0 :

BðB0 → K0Sπ

þπ−γÞ ¼NCR

sig

hϵ0i × NB0

; ð43Þ

where hϵ0i ¼ 0.0553þ0.0010−0.0009 is obtained from Eq. (14)

replacing the efficiencies ϵþk by those of the neutral kaonicresonances listed in Table XV and, assuming isospinsymmetry, using the FFs listed in Table V. The small valueof hϵ0i compared to that of hϵþi is due to the additionalrequirements on mππ and mKπ (see Sec. V B). The termfCR ¼ 0.728& 0.004 is the fraction of correctly recon-structed signal events. The term NB0 is obtained from thetotal number of BB pairs in the full BABAR data set, NBB,and the corresponding ϒð4SÞ branching fraction takenfrom Ref. [18]:

NB0 ¼ 2 × NBB × Bðϒð4SÞ → B0B0Þ¼ ð458.7& 6.3Þ × 106: ð44Þ

D. Results

Requiring mK0Sππ

≤ 1.8 GeV=c2, the unbinned maxi-mum-likelihood fit to the data for the B0 → K0

Sπ−πþγ

decay mode yields Nsig ¼ 243& 24þ21−17 events and in turn a

branching fraction of

BðB0 → K0πþπ−γÞ ¼ ð20.5& 2.0þ2.6−2.2Þ × 10−6; ð45Þ

where the first uncertainty is statistical and the second issystematic. This result is in good agreement with theprevious world average [18]. The same convention holdsfor results in Eqs. (46)–(48). The systematic uncertaintiesare discussed in detail in Sec. V E 2. To check the presenceof biases on the parameters of interest, 351 pseudoexperi-ments were generated with embedded signal events drawnfrom fully simulated MC samples and analyzed. Nosignificant biases were found. Figure 8 shows signal-enhanced distributions of the four discriminating variablesin the fit: ΔE, mES, F , and Δt. The result of the fit to thedata for the time-dependent CP violation parameters insignal events is

SK0Sπ

þπ−γ ¼ 0.14& 0.25& 0.03; ð46Þ

CK0Sπ

þπ−γ ¼ −0.39& 0.20þ0.03−0.02 : ð47Þ

To obtain the value of SK0Sργ

, we divide SK0Sπ

þπ−γ by thedilution factor given in Eq. (34) and obtain

SK0Sργ

¼ −0.18& 0.32þ0.06−0.05 : ð48Þ

Table XVII shows the correlation matrix for the stat-istical uncertainty obtained from the fit to the data.

E. Systematic uncertainties

1. CP asymmetry parameters

In order to assign systematic uncertainties due to thefixed parameters in the fit to mES, ΔE, F and Δt, we varyeach of the fixed parameters within its uncertainty, whichare taken from different sources that are detailed below, andreperform the fit. The fixed shape parameters of mES, ΔEand F PDFs are varied according to the uncertaintiesobtained in the fit to the simulated event samples fromwhich they are extracted. Since the mES-ΔE distribution ofBþ → K"þð→ K0

SπþÞγ þ Bþ → Xsuð→ K0

SπþÞγ back-

ground events is described by a two-dimensional histo-gram, we fluctuate the bin contents using the sameprocedure as described in Sec. IV D. The fixed yieldsare varied according to the corresponding branching

TABLE XV. Efficiencies ϵ0k for correctly reconstructed signalcandidates for each kaonic resonance from simulations withoutthe applied requirement mKππ < 1.8 GeV=c2. The efficiencies inthe neutral mode are significantly smaller to the ones in thecharged mode (see Table III) due to the additional requirementson mππ and mKπ . The difference between the ϵ0 values is due tothe difference in branching fractions of each kaonic resonance tothe K"ð892Þþπ− and K0

Sρð770Þ0 decay modes.

Kres ϵ0k

K1ð1270Þ0 0.0631& 0.0003K1ð1400Þ0 0.0335& 0.0003K"ð1410Þ0 0.0318& 0.0005K"

2ð1430Þ0 0.0471& 0.0002K"ð1680Þ0 0.0742& 0.0004

TIME-DEPENDENT ANALYSIS OF … PHYSICAL REVIEW D 93, 052013 (2016)

052013-23

the other shape parameters are fixed to the values deter-mined from a fit to the off-resonance data.The mES, ΔE and F PDFs for all the categories of B-

background events, given in Table XIV, are described byparametric functions, except for the Bþ → K0

SπþγB back-

ground mES and ΔE PDFs, for which significant correla-tions are present. These correlations are taken into accountthrough a nonparametric two-dimensional PDF, defined asa histogram constructed from a mixture of Bþ → K"þð→K0

SπþÞγ and Bþ → Xsuð→ K0

SπþÞγ simulated events. All

shape parameters of the B-background PDFs are fixed tovalues determined from simulation.No significant correlations were found among the fit

variables for the other event species in the fit.

3. Branching fraction determination

The branching fraction to the K0Sπ

þπ−γ final state isdetermined from the fitted yield of the correctly recon-structed signal event category, NCR

sig ¼ Nsig × fCR, theweighted signal efficiency hϵ0i, and the number of neutralB events NB0 :

BðB0 → K0Sπ

þπ−γÞ ¼NCR

sig

hϵ0i × NB0

; ð43Þ

where hϵ0i ¼ 0.0553þ0.0010−0.0009 is obtained from Eq. (14)

replacing the efficiencies ϵþk by those of the neutral kaonicresonances listed in Table XV and, assuming isospinsymmetry, using the FFs listed in Table V. The small valueof hϵ0i compared to that of hϵþi is due to the additionalrequirements on mππ and mKπ (see Sec. V B). The termfCR ¼ 0.728& 0.004 is the fraction of correctly recon-structed signal events. The term NB0 is obtained from thetotal number of BB pairs in the full BABAR data set, NBB,and the corresponding ϒð4SÞ branching fraction takenfrom Ref. [18]:

NB0 ¼ 2 × NBB × Bðϒð4SÞ → B0B0Þ¼ ð458.7& 6.3Þ × 106: ð44Þ

D. Results

Requiring mK0Sππ

≤ 1.8 GeV=c2, the unbinned maxi-mum-likelihood fit to the data for the B0 → K0

Sπ−πþγ

decay mode yields Nsig ¼ 243& 24þ21−17 events and in turn a

branching fraction of

BðB0 → K0πþπ−γÞ ¼ ð20.5& 2.0þ2.6−2.2Þ × 10−6; ð45Þ

where the first uncertainty is statistical and the second issystematic. This result is in good agreement with theprevious world average [18]. The same convention holdsfor results in Eqs. (46)–(48). The systematic uncertaintiesare discussed in detail in Sec. V E 2. To check the presenceof biases on the parameters of interest, 351 pseudoexperi-ments were generated with embedded signal events drawnfrom fully simulated MC samples and analyzed. Nosignificant biases were found. Figure 8 shows signal-enhanced distributions of the four discriminating variablesin the fit: ΔE, mES, F , and Δt. The result of the fit to thedata for the time-dependent CP violation parameters insignal events is

SK0Sπ

þπ−γ ¼ 0.14& 0.25& 0.03; ð46Þ

CK0Sπ

þπ−γ ¼ −0.39& 0.20þ0.03−0.02 : ð47Þ

To obtain the value of SK0Sργ

, we divide SK0Sπ

þπ−γ by thedilution factor given in Eq. (34) and obtain

SK0Sργ

¼ −0.18& 0.32þ0.06−0.05 : ð48Þ

Table XVII shows the correlation matrix for the stat-istical uncertainty obtained from the fit to the data.

E. Systematic uncertainties

1. CP asymmetry parameters

In order to assign systematic uncertainties due to thefixed parameters in the fit to mES, ΔE, F and Δt, we varyeach of the fixed parameters within its uncertainty, whichare taken from different sources that are detailed below, andreperform the fit. The fixed shape parameters of mES, ΔEand F PDFs are varied according to the uncertaintiesobtained in the fit to the simulated event samples fromwhich they are extracted. Since the mES-ΔE distribution ofBþ → K"þð→ K0

SπþÞγ þ Bþ → Xsuð→ K0

SπþÞγ back-

ground events is described by a two-dimensional histo-gram, we fluctuate the bin contents using the sameprocedure as described in Sec. IV D. The fixed yieldsare varied according to the corresponding branching

TABLE XV. Efficiencies ϵ0k for correctly reconstructed signalcandidates for each kaonic resonance from simulations withoutthe applied requirement mKππ < 1.8 GeV=c2. The efficiencies inthe neutral mode are significantly smaller to the ones in thecharged mode (see Table III) due to the additional requirementson mππ and mKπ . The difference between the ϵ0 values is due tothe difference in branching fractions of each kaonic resonance tothe K"ð892Þþπ− and K0

Sρð770Þ0 decay modes.

Kres ϵ0k

K1ð1270Þ0 0.0631& 0.0003K1ð1400Þ0 0.0335& 0.0003K"ð1410Þ0 0.0318& 0.0005K"

2ð1430Þ0 0.0471& 0.0002K"ð1680Þ0 0.0742& 0.0004

TIME-DEPENDENT ANALYSIS OF … PHYSICAL REVIEW D 93, 052013 (2016)

052013-23

471 x 106 BB pairs[PRD 93, 052013 (2016)]


Search for B0→φγ [arxiv:1603.06546]

• Proceeds via b→d FCNC transition

• Very rare in SM: B(B0→φγ) ~ [10-12,10-11]

• NP could cause enhancements to up factor 1000

• Selection:

• high energy photon: E* > 2 GeV

• 1.000 < mKK < 1.039

• explicit vetoes on π0 and η decays

• continuum background rejection with neural net: CNN

• Signal yield measured with 4D fit to: Mbc, ΔE, CNN and helicity angle:

10

Mbc

preliminary


Search for B0→φγ [arxiv:1603.06546]

• Fit projections:

• No signal observed

• Upper limit:

• Improves on previous best limit (8.5 x 10-7 from BaBar) by ~ order of magnitude

11

772 x 106 BB pairs

preliminary


B0→K*0e+e- [JHEP 04 (2015) 064]

• Analysis of low-q2 region [0.002,1.120]: virtual photon contribution dominates, giving access to photon polarisation

• Allows search for right-handed currents in NP scenarios: C7, C7’

• Very different physics from B0→K*0μ+μ-, which is more sensitive to C9 and C10

• More challenging experimentally:

- excellent muon trigger not applicable

- bremsstrahlung degrades mass resolution

12

differential decay rate (cartoon)

L = 3 fb-1


size [14], the B0! K⇤0e+e� angular distribution reads as

1

d(�+ �)/dq2d4(�+ �)

dq2 dcos ✓`

dcos ✓K

d�=

9

16⇡

3

4(1 � FL) sin

2 ✓K

+ FL cos2 ✓

K

+

✓1

4(1 � FL) sin

2 ✓K

� FL cos2 ✓

K

◆cos 2✓

`

+

1

2(1 � FL)A

(2)T sin2 ✓

K

sin2 ✓`

cos 2� +

(1 � FL)AReT sin2 ✓

K

cos ✓`

+

1

2(1 � FL)A

ImT sin2 ✓

K

sin2 ✓`

sin 2�

�.

(1)

The four angular observables FL, A(2)T , ARe

T and AImT are related to the transversity

amplitudes through [2]

FL =|A0|2

|A0|2 + |A|||2 + |A?|2

A(2)T =

|A?|2 � |A|||2

|A?|2 + |A|||2

AReT =

2Re(A||LA⇤?L

+ A||RA⇤?R

)

|A|||2 + |A?|2

AImT =

2Im(A||LA⇤?L

+ A||RA⇤?R

)

|A|||2 + |A?|2 ,

(2)

where |A0|2 = |A0L|2 + |A0R|2, |A?|2 = |A?L

|2 + |A?R

|2 and |A|||2 = |A||L|2 + |A||R|2. Theamplitudes A0, A|| and A? correspond to di↵erent polarisation states of the K⇤0 in thedecay. The labels L and R refer to the left and right chirality of the dielectron system.

Given the definition of �, the observable A(2)T is averaged between B0 and B0 decays,

while AImT corresponds to a CP asymmetry [15]. The observable FL is the longitudinal

polarisation of the K⇤0 and is expected to be small at low q2, since the virtual photonis then quasi-real and therefore transversely polarised. The observable ARe

T is related tothe forward-backward asymmetry AFB by ARe

T = 43AFB/(1 � FL) [2]. The observables

A(2)T and AIm

T , in the limit q2 ! 0, can be expressed as simple functions of the C7 and C 07

coe�cients [2]

A(2)T (q2 ! 0) =

2Re(C7C0⇤7 )

|C7|2 + |C 07|2

and AImT (q2 ! 0) =

2Im(C7C0⇤7 )

|C7|2 + |C 07|2

. (3)

These measurements therefore provide information on photon polarisation amplitudes,similar to that obtained by the CP asymmetry measured through time-dependent analysesin B0! K⇤0(! K0

S⇡0)� decays [16, 17].

This paper presents measurements of FL, A(2)T , AIm

T and AReT of the B0 ! K⇤0e+e�

decay in the bin corresponding to a reconstructed q2 from 0.0004 to 1GeV2/c4.

3

B0→K*0e+e- [JHEP 04 (2015) 064]

• Differential decay rate:

• Determine four quantities from the angular distributions:

- FL: K* longitudinal polarisation, expected small since photon is quasi-real

- : related to FB asymmetry

- Two quantities sensitive to photon polarisation:

13

fold φ→φ+π, for φ<0

AReT =

4

3AFB/(1� FL)

Angular analysis of B0 Ñ K ˚e`e´ at low-q2

The simplified angular expression for B0 Ñ K˚e`e´:

1

dp� ` �q{dq2

d4p� ` �qdq2d cos ✓l d cos ✓Kd�

“ 9

16⇡r 34

p1 ´ FLq sin2 ✓K ` FL cos2 ✓K

` p 14

p1 ´ FLq sin2 ✓K ´ FL cos2 ✓K q cos 2✓l

` 1

2p1 ´ FLqAp2q

T sin2 ✓K sin2 ✓l cos 2� ` p1 ´ FLqAReT sin2 ✓K cos ✓l

` 1

2p1 ´ FLqAIm

T sin2 ✓K sin2 ✓l sin 2�s

fold � Ñ � “ � ` ⇡ for � † 0

Four observables:Ap2q

T and AImT in low q2

are linked to photon polarisation

Ap2qT pq2 Ñ 0q “ 2RepC7C

17

˚q|C7|2 ` |C 1

7|2 AImT pq2 Ñ 0q “ 2ImpC7C

17

˚q|C7|2 ` |C 1

7|2

FL: longitudinal polarisation

AReT “ 4

3AFB{p1 ´ FLq: related to forward-backward asymmetry

10 / 15


B0→K*0e+e- [JHEP 04 (2015) 064]

• 4D fit to invariant mass and 3 decay angles

• Background from K*γ + photon conversion reduced with lower mass cut, residual 4%

• Angular efficiency maps derived from simulation

• Results (corrected for K*γ background):

14

compatible with SM expectationsC7’/C7 compatible with zero

first measurements for this q2 range

L = 3 fb-1

Electroweak penguin decays: b→sl+l-

• B+→K+τ+τ- at BaBar• B0→K*0μ+μ- results from

LHCb (and elsewhere)

15


Search for B+ ➝ K+τ+τ- [arXiv:1605.09637]

• Third family equivalent of B→Kl+l- where l = e or μ

• Potential contribution of neutral Higgs boson due to large mass of τ

• Recent tension in

• Challenging experimentally!

- multiple neutrinos in final state

- few kinematic handles

• Use hadronic tagging to tag “other” B in the event: fully reconstruct a hadronic decay

• τ decay modes: leptonic modes

16

RK = B(B!Kµµ)B(B!Kee)

3

B+ → K+τ+τ–: overview

Tag

Signal

Phys.Rev.D53,4964,1996

e

τ

● Heavy τ mass impose upper limit on kaon momentum (~1.5 GeV/c) → no long distance contribution

● Hadronic Btag

reconstruction Btag

→ DX, D=D(*)0, D(*)±,

Ds

*± or J/ψ, X=combination of up to 5 π and/or K's

● Three different final states considered here:

- Electron: τ+ →e+ νe ν

τ , τ– → e– ν

e ν

τ

- Muon: τ+ →μ+ νμν

τ , τ– → μ– ν

μν

τ

- Mixed: τ+ →e+ νe ν

τ , τ– → μ– ν

μν

τ (+ CC)

● Cut and count analysis

Hadronic Reconstruction (ϵ ~ 0.3%)D = {D,D*,Ds,J/ψ}

X = 1-5 {K,π}

3

B+ → K+τ+τ–: overview

Tag

Signal

Phys.Rev.D53,4964,1996

e

τ

● Heavy τ mass impose upper limit on kaon momentum (~1.5 GeV/c) → no long distance contribution

● Hadronic Btag

reconstruction Btag

→ DX, D=D(*)0, D(*)±,

Ds

*± or J/ψ, X=combination of up to 5 π and/or K's

● Three different final states considered here:

- Electron: τ+ →e+ νe ν

τ , τ– → e– ν

e ν

τ

- Muon: τ+ →μ+ νμν

τ , τ– → μ– ν

μν

τ

- Mixed: τ+ →e+ νe ν

τ , τ– → μ– ν

μν

τ (+ CC)

● Cut and count analysis

Signal side


Search for B+ ➝ K+τ+τ- [arXiv:1605.09637]

• Selection:

- exactly 3 tracks + particle ID

- Emiss > 0

- mES > 5.27, |ΔE| < 0.12 GeV

- vetoes: J/ψ, D0, π0

• Peaking background with same final state particles:

• Suppress with multi-layer perceptron (MLP) with 7 inputs

• Results:

• eμ channel shows 3.7σ excess. Total significance for 3 channels < 2σ: quote upper limit only

17

B ! D(! K`⌫)`⌫

ter clusters not explicitly associated with B

tag

daughter173

particles may originate from other low-energy particles174

in background events. We therefore define E

⇤extra

to be175

the energy sum of all neutral clusters with individual en-176

ergy greater than 50 MeV that are not used in the B

tag

177

reconstruction.178

The normalized squared mass of the ⌧

+

⌧

� pair is given179

by sB = (pBsig � pK)2/m

2

B , where pBsig and pK are the180

four-momentum vectors of B

sig

and of the kaon, respec-181

tively, in the laboratory frame. The large mass of the ⌧182

leptons in signal events kinematically limits the sB dis-183

tribution to large values. A requirement of sB > 0.45 is184

applied.185

At this point in the selection, remaining backgrounds186

are primarily BB events in which a properly recon-187

structed B

tag

is accompanied by B

sig

! D

(⇤)

`⌫`, with188

D

(⇤) ! K`

0⌫`0 and thus have the same detected final-189

state particles as signal events. A multi-layer perceptron190

(MLP) neural network [27], with seven input variables191

and one hidden layer, is employed to suppress this back-192

ground. The input variables are: the angle between the193

kaon and the oppositely charged lepton, the angle be-194

tween the two leptons, and the momentum of the lep-195

ton with charge opposite to the K, all in the ⌧

+

⌧

�196

rest frame, which is calculated as p

Bsig � pK ; the an-197

gle between the B

sig

and the oppositely charged lepton,198

the angle between the K and the low-momentum lep-199

ton, and the invariant mass of the K

+

`

� pair, all in the200

CM frame. Furthermore, the final input variables to the201

neural network are E

⇤extra

and the residual energy, E

res

,202

which here is e↵ectively the missing energy associated203

with the ⌧

+

⌧

� pair and is calculated as the energy com-204

ponent of p

⌧residual

= p

⌧Bsig

� p

⌧K � p

⌧`+`� , where p

⌧Bsig

,205

p

⌧K and p

⌧`+`� are the four-momenta vectors in the ⌧

+

⌧

�206

rest frame of the B

sig

, K, and lepton pair in the event,207

respectively. E

res

has, in general, higher values for sig-208

nal events than generic BB and continuum events due209

to the higher neutrino multiplicity. A neural network is210

trained and tested using randomly split dedicated signal211

MC and B

+

B

� background events, for each of the three212

channels: e

+

e

�, µ

+

µ

�, and e

+

µ

�. The results are shown213

in Fig. 2 for the three modes combined. The last step in214

the signal selection is to require that the output of the215

neural network is > 0.70 for the e

+

e

� and µ

+

µ

� chan-216

nels and > 0.75 for the e

+

µ

� channel. This requirement217

is optimized to yield the most stringent upper limit in218

the absence of a signal.219

The branching fraction for each of the signal modes, i,is calculated as:

Bi =N

iobs

� N

ibkg

✏

isig

NBB

, (2)

where NBB = 471 ⇥ 106 is the total number of BB pairs220

in the data sample, assuming equal production of B

+

B

�221

and B

0

B

0 pairs in ⌥ (4S) decays, and N

iobs

is the number222

MLP output

-0.4 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

En

trie

s/0

.04

0

50

100

150

200

250

300

FIG. 2: (color online) MLP output distribution for the threesignal channels combined. The B+ ! K+⌧+⌧� signal MCdistribution is shown (dashed) with arbitrary normalization.The data (points) are overlaid on the expected combinatorial(shaded) plus m

ES

-peaking (solid) background contributions.

of data events passing the signal selection. The signal ef-223

ficiency, ✏

isig

, and the background estimate, N

ibkg

, are de-224

termined for each mode from the signal and background225

MC yields after all selection requirements.226

For each mode, N

bkg

consists of two components:227

background events that have a properly reconstructed228

B

tag

and thus produce a distribution in m

ES

which229

peaks at the B mass, and combinatorial background230

events composed of continuum and BB events with mis-231

reconstructed B

tag

candidates which do not produce a232

peaking structure in the m

ES

signal region. After the233

MLP output requirement, peaking background events234

comprise more than 92% of the total N

bkg

for all three235

modes. To reduce the dependence on MC simulation, the236

combinatorial background is extrapolated directly from237

the yield of data events in the m

ES

“sideband” region238

(5.20 < m

ES

< 5.26 GeV/c

2), after the full signal selec-239

tion. Sideband data events are scaled to the correct nor-240

malization of the combinatorial background in the m

ES

241

signal region.242

The peaking background is determined using B

+

B

�243

background MC, while data in the final signal region244

is kept blinded to avoid experimentalist bias. Because245

of the large uncertainties on the branching fractions of246

many of the B

tag

decay modes as well as their associ-247

ated reconstruction e↵ects, there is a discrepancy in the248

B

tag

yield of approximately 10% between MC and data,249

independent of the signal selection. A B

tag

yield correc-250

tion is therefore determined by calculating the ratio of251

data to B

+

B

� MC events after the sB requirement. The252

data sample after this requirement contains a su�ciently253

large background contribution after the sB requirement,254

which consists mainly of B

+

B

� events (> 96%) according255

to MC simulation, to allow for a data-driven correction256

without unblinding the final signal-region. This correc-257

tion factor is determined to be 0.913 ± 0.020 and is ap-258

5

Signal MC (arb. scale)Peaking backgroundComb. background

2 GeV/c+π

-Km

1.8 1.81 1.82 1.83 1.84 1.85 1.86 1.87 1.88 1.89 1.9

)2

Entr

ies(

/20 M

eV

/c

0

20

40

60

80

100

120

140

160

180

FIG. 3: (color online) Invariant-mass distribution of theK�`+ pair in the B+ ! D0`+⌫`, D

0 ! K�⇡+ samples af-ter all signal selection criteria are applied, except for the fi-nal requirement on the MLP output. The data (points) areoverlaid on the expected combinatorial (shaded) plus m

ES

-peaking (solid) background contributions.

plied to the MC reconstruction e�ciency for both signal259

and background events.260

The B

tag

yield is also cross-checked using a B

+ !261

D

0

`

+

⌫`, D

0 ! K

�⇡

+ control sample, which is selected262

using the same signal selection discussed above, but with263

requiring one track to satisfy pion instead of lepton PID264

and reversing the D

0 veto, such that 1.80 < mK�⇡+<265

1.90 GeV/c

2. These criteria are also applied to the full266

background MC and the resulting sample is found to con-267

sist mainly of peaking B

+

B

� events, which the MLP neu-268

ral network is trained to classify as background. Before269

the MLP requirement, good agreement between data and270

MC is found in all the distributions of the input variables271

of the B

+ ! D

0

`

+

⌫`, D0 ! K

�⇡

+ samples, as shown272

in Fig. 3 for the mK�⇡+ distribution. These samples are273

then run through the MLP neural network and a detailed274

comparison of the MLP output and the input variables,275

after the full signal selection, is performed.276

The results for each signal channel are then combined277

to determine B(B+ ! K

+

⌧

+

⌧

�). This is done using a278

frequentist approach by finding the value of B that maxi-279

mizes the product of the Poisson likelihoods of observing280

N

iobs

in each of the signal channels. Branching fraction281

uncertainties and limits are determined using the method282

described in Ref. [28], taking into account the statistical283

and systematic uncertainties on N

bkg

and ✏

sig

.284

Systematic uncertainties associated with the level of285

data-MC agreement are determined for most of the vari-286

ables used in the signal selection. The determination287

of the B

tag

yield correction is anti-correlated with the288

extrapolation of the combinatorial background from the289

m

ES

sideband, as both use the combinatorial background290

shape from MC. Therefore, only one systematic uncer-291

tainty on the B

tag

yield and combinatorial background292

estimate is evaluated, using a simulated MC sample com-293

e+e� µ+µ� e+ µ�

N ibkg

49.4±2.4±2.9 45.8±2.4 ±3.2 59.2±2.8 ±3.5✏isig

(⇥10�5) 1.1 ±0.2±0.1 1.3±0.2±0.1 2.1±0.2±0.2N i

obs

45 39 92Significance (�) -0.6 -0.9 3.7

TABLE I: Expected background yields, N ibkg

, signal e�cien-cies, ✏i

sig

, number of observed data events, N iobs

, and signedsignificance for each signal mode. Quoted uncertainties arestatistical and systematic.

posed of background events with the same luminosity as294

the data sample. Accounting for the anti-correlation, the295

e↵ect of varying the value of the B

tag

yield correction on296

the final signal e�ciency and background estimate is de-297

termined to be 1.2% and 1.6%, respectively. The uncer-298

tainty associated with the theoretical model is evaluated299

by reweighting the sB distribution of the dedicated sig-300

nal MC sample to the LCSR [23] theoretical model and301

to that of Ref. [29] and determining the di↵erence in sig-302

nal e�ciency, which is calculated to be 3.0%. Additional303

uncertainties on ✏

sig

and N

bkg

arise due to the model-304

ing of PID selectors (4.8% for e

+

e

�, 7.0% for µ

+

µ

�,305

and 5.0% for e

+

µ

�) and the ⇡

0 veto (3.0%). The level306

of agreement between data and MC is evaluated using307

the B

+ ! D

0

`

+

⌫`, D0 ! K

�⇡

+ control sample before308

and after the MLP requirement. Comparison of both309

the overall yields as well as the distributions of the input310

and output variable results in a systematic uncertainty of311

2.6%. Other potential sources of systematic uncertainties312

have been investigated, including those associated with313

the assumption that charged and neutral B candidates314

are produced at equal rates, the continuum likelihood315

suppression, B

tag

purity, track multiplicity, E

miss

and sB316

selection criteria, and are all implicitly accounted for in317

the B

tag

yield correction uncertainty. Correlations be-318

tween the signal e�ciency and the background estimate319

due to common systematic errors are included, but are320

found to have a negligible e↵ect on the final branching321

fraction results.322

The final signal e�ciencies, background estimates and323

observed yields of each signal mode are shown in Ta-324

ble I, with the associated branching fraction significance.325

The yields in the e

+

e

� and µ

+

µ

� channels show con-326

sistency with the expected background estimate. The327

yields in the e

+

µ

� channel consist of 40 e

+

µ

� and 52328

e

�µ

+ events, which corresponds to an excess of 3.7�329

over the background expectation. Examination of kine-330

matic distributions in the e

+

µ

� channel does not give331

any clear indication either of signal-like behavior or of332

systematic problems with background modeling. When333

combined with the e

+

e

� and µ

+

µ

� modes, the overall334

significance of the B

+ ! K

+

⌧

+

⌧

� signal is less than 2�,335

and hence we do not interpret this as evidence of signal.336

6

B(B+ ! K+⌧+⌧�) < 2.25⇥ 10�3

90% CL

471 x 106 BB pairs

MLP cut

preliminary


B0→K*0μ+μ- angular analysis• Angular analysis provides many observables

that are sensitive to NP

• Fit to m(Kπμμ), m(Kπ) and three angles, in bins of q2 = mμμ2

• Exploit optimised variables to reduce FF uncertainty: e.g. P5’

• Possible S-wave component included in fit for first time

• Full Run 1 dataset: 3/fb

18

for q2 < 1GeV2/c

4 and are therefore adopted for the full q2 range. The S1c observablecorresponds to the fraction of longitudinal polarisation of the K

⇤0 meson and is thereforemore commonly referred to as FL, with

FL = S1c =|AL

0 |2 + |AR0 |2

|AL0 |2 + |AR

0 |2 + |ALk |2 + |AR

k |2 + |AL?|2 + |AR

?|2. (3)

It is also conventional to replace S6s by the forward-backward asymmetry of the dimuon sys-tem AFB, with AFB = 3

4S6s. The CP -averaged angular distribution of the B

0! K

⇤0µ

+µ

�

decay can then be written as

1

d(�+ �)/dq2d4(�+ �)

dq2 d~⌦=

9

32⇡

h34(1� FL) sin

2✓

K

+ FL cos2✓

K

+14(1� FL) sin

2✓

K

cos 2✓l

�FL cos2✓

K

cos 2✓l

+ S3 sin2✓

K

sin2✓

l

cos 2�

+S4 sin 2✓K sin 2✓l

cos�+ S5 sin 2✓K sin ✓l

cos�

+43AFB sin2

✓

K

cos ✓l

+ S7 sin 2✓K sin ✓l

sin�

+S8 sin 2✓K sin 2✓l

sin�+ S9 sin2✓

K

sin2✓

l

sin 2�i.

(4)

Additional sets of observables, for which the leading B0 ! K

⇤0 form-factor uncertaintiescancel, can be built from FL and S3–S9. Examples of such optimised observables includethe transverse asymmetry A

(2)T [23], where A

(2)T = 2S3/(1 � FL), and the P

(0)i

series ofobservables [24]. In this paper the notation used is

P1 =2S3

(1� FL)= A

(2)T ,

P2 =2

3

AFB

(1� FL),

P3 =�S9

(1� FL),

P

04,5,8 =

S4,5,8pFL(1� FL)

,

P

06 =

S7pFL(1� FL)

.

(5)

The definition of the P

0i

observables di↵ers from that of Ref. [24], but is consistent withthe notation used in the LHCb analysis of Ref. [8].

In addition to the resonant P-wave K

⇤0 contribution to the K

+⇡

�µ

+µ

� final state,the K

+⇡

� system can also be in an S-wave configuration. The addition of an S-wavecomponent introduces two new complex amplitudes, AL,R

S , and results in the six additional

3

]2c) [MeV/−µ+µ−π+K(m5200 5400 5600

2 cC

andi

date

s / 1

1 M

eV/

0

50

100310×

LHCb*0Kψ/J → 0B

]2c) [MeV/−µ+µ−π+K(m5200 5400 5600

2 cC

andi

date

s / 1

1 M

eV/

0

200

400

600

LHCb−µ+µ*0K → 0B

Figure 3: Invariant mass m(K+⇡�µ+µ�) for (left) the control decay B0! J/ K⇤0 and (right)the signal decay B0! K⇤0µ+µ�, integrated over the full q2 range (see text). Overlaid are theprojections of the total fitted distribution (black line) and the signal and background components.The signal is shown by the blue shaded area and the background by the red hatched area.

Sec. 2. The angular distribution of the signal is described using Eq. (6). The backgroundangular distribution is modelled with second order polynomials in cos ✓

l

, cos ✓K

and �,the parameters of which are left free in the fit. The angular distribution is assumed tofactorise in the three decay angles. This assumption has been validated in the upper masssideband.

In order to describe the signal angular distribution, the angular acceptance discussedin Sec. 5 must be accounted for. The acceptance is treated in one of two ways, dependingon the q

2 range being fitted. In the narrow q

2 bins, the acceptance is treated as beingconstant across each bin and is included in the fit by multiplying Eq. (6) by the acceptancefunction evaluated at the bin centre. In the wider 1.1 < q

2< 6.0GeV2

/c

4 and 15.0 < q

2<

19.0GeV2/c

4 bins, the shape of the acceptance can vary significantly across the bin. Inthis case, the candidates are weighted in the likelihood fit by the inverse of their e�ciency.The event weights are scaled such that this pseudo-likelihood fit has confidence intervalswith the correct coverage.

The K+⇡

�µ

+µ

� invariant mass is included in the fit to separate signal from background.The signal and background mass distributions are parameterised as described in Sec. 6.In order to better constrain the S-wave fraction, a simultaneous fit of the m(K+

⇡

�)distribution is performed using the parameterisation described in Sec. 6. The signal fractionand FS are common parameters in the simultaneous fits to the m(K+

⇡

�) distributionand to the angular and m(K+

⇡

�µ

+µ

�) distributions. Figure 4 shows the projectionsof the fitted probability density function on the angular and mass distributions for the1.1 < q

2< 6.0GeV2

/c

4q

2 bin. Good agreement of the fitted function with the data isobserved. Projections for the other q2 bins are provided in Appendix B.

The P

(0)i

observables introduced in Sec. 2 are determined by reparameterising Eq. (4)using a basis comprising FL, P1,2,3 and P

04,5,6,8. The CP asymmetries are determined by

modifying the angular convention, introducing a relative sign between the angular terms

12

Signal: 2398±57

all q2

T. Blake

Exploring FCNC processes• Flavour changing neutral current transitions only occur at loop order

(and beyond) in the SM.

!

!

!• New particles can contribute at loop or tree level:

!

!

!

• Enhancing/suppressing decay rates, introducing new sources of CP violation or modifying the angular distribution of the final-state particles

2

b s

µ+

µ−ν

W− W+

tb s

µ+

µ−

t

γ, Z0

W−

b s

µ+

µ−ν

H− H+

tb s

µ+

µ−

di

γ, Z0

χ0 b s

µ+

µ−

di

H0

g b s

µ+

µ−Z ′

SM diagrams involve the charged current interaction.

L = 3 fb-1


B0→K*0μ+μ- angular analysis

• All results compatible with SM expectation, except…

• P5’ shows 2.8σ and 3.0σ discrepancy from SM

• Many other results to be found in JHEP 02 (2016) 104

19

]4c/2 [GeV2q0 5 10 15

1P

-2

-1

0

1

2LHCb

SM from DHMV

]4c/2 [GeV2q0 5 10 15

2P

-2

-1

0

1

2LHCb

SM from DHMV

]4c/2 [GeV2q0 5 10 15

3P

-2

-1

0

1

2LHCb

SM from DHMV

]4c/2 [GeV2q0 5 10 15

4'P

-2

-1

0

1

2LHCb

SM from DHMV

]4c/2 [GeV2q0 5 10 15

5'P

-2

-1

0

1

2LHCb

SM from DHMV

]4c/2 [GeV2q0 5 10 15

6'P

-2

-1

0

1

2LHCb

SM from DHMV

]4c/2 [GeV2q0 5 10 15

8'P

-2

-1

0

1

2LHCb

SM from DHMV

Figure 8: The optimised angular observables in bins of q2, determined from a maximum likelihoodfit to the data. The shaded boxes show the SM prediction taken from Ref. [14].

24

]4c/2 [GeV2q0 5 10 15

LF

0

0.2

0.4

0.6

0.8

1

LHCbSM from ABSZ

]4c/2 [GeV2q0 5 10 15

FBA

-0.5

0

0.5

LHCbSM from ABSZ

]4c/2 [GeV2q0 5 10 15

3S

-0.5

0

0.5LHCb

SM from ABSZ

]4c/2 [GeV2q0 5 10 15

4S

-0.5

0

0.5LHCb

SM from ABSZ

]4c/2 [GeV2q0 5 10 15

5S

-0.5

0

0.5LHCb

SM from ABSZ

]4c/2 [GeV2q0 5 10 15

7S

-0.5

0

0.5LHCb

]4c/2 [GeV2q0 5 10 15

8S

-0.5

0

0.5LHCb

]4c/2 [GeV2q0 5 10 15

9S

-0.5

0

0.5LHCb

Figure 6: The CP -averaged observables in bins of q2, determined from a maximum likelihood fitto the data. The shaded boxes show the SM predictions based on the prescription of Ref. [19].

22

P0

5 =S5p

FL(1� FL)

L = 3 fb-1


• Lower statistics, but…

• B→K*ee final state

• B+ modes

• These aspects will be more fully explored at Belle2

20

12

(a)Result for P 04

(b)Result for P 05

(c)Result for P 06

(d)Result for P 08

FIG. 5. Result for the P 0 observables compared to SM predictions from various sources described in Section X. Results fromLHCb [1, 17] are shown for comparison.

physics/0402093.[9] M. Feindt, F. Keller, M. Kreps, T. Kuhr, S. Neubauer,

et al., Nucl.Instrum.Meth. A654, 432 (2011),arXiv:1102.3876 [hep-ex].

[10] S. H. Lee, K. Suzuki, K. Abe, K. Abe, T. Abe, andI. . Adachi (Belle Collaboration), Phys. Rev. Lett. 91,261801 (2003).

[11] T. Skwarnicki, DESY-F31-86-02.[12] H. Albrecht, Physics Letters B 340, 217 (1994).[13] R. Aaij et al. (LHCb), JHEP 08, 131 (2013),

arXiv:1304.6325.[14] W. Altmannshofer, P. Ball, A. Bharucha, A. J. Buras,

D. M. Straub, and M. Wick, JHEP 01, 019 (2009),arXiv:0811.1214 [hep-ph].

[15] S. Descotes-Genon, J. Matias, M. Ramon, and J. Virto,JHEP 01, 048 (2013), arXiv:1207.2753 [hep-ph].

[16] S. Descotes-Genon, T. Hurth, J. Matias, and J. Virto,JHEP 1305, 137 (2013), arXiv:1303.5794 [hep-ph].

[17] R. Aaij et al. (LHCb Collaboration), Phys. Rev. Lett.111, 191801 (2013).

[18] M. D. Cian, Track Reconstruction E�ciency and Analy-sis of B0 ! K⇤0µ+µ� at the LHCb Experiment, Ph.D.thesis, University of Zurich (2013).

[19] V. Blobel, Statistische und Numerische Methoden derDatenanalyse (1998).

[20] S. Descotes-Genon, L. Hofer, J. Matias, and J. Virto,JHEP 12, 125 (2014), arXiv:1407.8526 [hep-ph].

[21] A. Bharucha, D. M. Straub, and R. Zwicky, (2015),arXiv:1503.05534 [hep-ph].

[22] S. Jager and J. M. Camalich, JHEP 05, 043 (2013),arXiv:1212.2263 [hep-ph].

[23] S. Jager and J. M. Camalich, Phys. Rev. D93, 014028(2016), arXiv:1412.3183 [hep-ph].

• Angular fit results: (numerical values in back up)

FL

2q0 2 4 6 8 10 12 14 16 18

LF

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

BelleCDFLHCbCMSATLASBabar K*

0Babar K*+Babar K*

J/' '(2S)

2q0 2 4 6 8 10 12 14 16 18

FBA

-0.4

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0

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1


0Babar K*+Babar K*

AFB

2q0 2 4 6 8 10 12 14 16 18

LF

-0.4

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0Babar K*+Babar K*

2q0 2 4 6 8 10 12 14 16 18

LF

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0Babar K*+Babar K*

2q0 2 4 6 8 10 12 14 16 18

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0Babar K*+Babar K*

2q0 2 4 6 8 10 12 14 16 18

LF

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0Babar K*+Babar K*

2q0 2 4 6 8 10 12 14 16 18

LF

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0Babar K*+Babar K*

2q0 2 4 6 8 10 12 14 16 18

LF

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0Babar K*+Babar K*

q2 [GeV2/c4]

q2

q2

q2 [GeV2/c4]

2q0 2 4 6 8 10 12 14 16 18

LF

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0Babar K*+Babar K*

2q0 2 4 6 8 10 12 14 16 18

LF

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0Babar K*+Babar K*

Angular analysis of B → K *!�!− decays

Simon Akar 16

PRD 93, 052015 (2016)

BEAUTY 16' - Radiative/EWP B decays @ B-factories

SM from DHMV*

[JHEP, 05 (2013) 137] * central values only

BaBar

BaBar

• Angular fit results: (numerical values in back up)

FL

2q0 2 4 6 8 10 12 14 16 18

LF

-0.4

-0.2

0

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0Babar K*+Babar K*

J/' '(2S)

2q0 2 4 6 8 10 12 14 16 18

FBA

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0Babar K*+Babar K*

AFB

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LF

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0Babar K*+Babar K*

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0Babar K*+Babar K*

q2 [GeV2/c4]

q2

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q2 [GeV2/c4]

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LF

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0Babar K*+Babar K*


Simon Akar 16

PRD 93, 052015 (2016)


SM from DHMV*

[JHEP, 05 (2013) 137] * central values only

BaBar

BaBar

FL

AFB

q2 (GeV2)

• Angular fit results: (numerical values in back up) ‣ Results in the q0

2 bin: [1, 6] GeV2/c4

‣ Tension appears in FL for the charged mode results (first measurement) with both SM prediction and neutral mode result!

‣ AFB in good agreement with previous results and SM predictions


Simon Akar 17

PRD 93, 052015 (2016)


LF0 0.2 0.4 0.6 0.8

0ATLAS K*

0CMS K*

0LHCb K*

0CDF K*

0,+Belle K*

0,+Babar K*

0Babar K*

+Babar K*

FBA-0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6

0ATLAS K*

0CMS K*

0LHCb K*

0CDF K*

0,+Belle K*

0,+Babar K*

0Babar K*

+Babar K*

FBA-0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6

0ATLAS K*

0CMS K*

0LHCb K*

0CDF K*

0,+Belle K*

0,+Babar K*

0Babar K*

+Babar K* BaBarBaBar

q2 [GeV2/c4]q2 [GeV2/c4]FL AFB

Tension in FL for K*+?

471 x 106 BB pairs

772 x 106 BB pairsB→K*l+l- from B-factories

arXiv:1604.04042

PRD 93, 052015 (2016)


B0→K*0μ+μ- from CMS [PLB 753 (2016) 424]

• Lower signal yield than LHCb ⇒ simpler analysis

• But still interesting measurements of FL and AFB

21

11

)2 (GeV2q2 4 6 8 10 12 14 16 18

LF

00.10.20.30.40.50.60.70.80.9

1

Data⟩ SM, LCSR ⟨⟩ SM, Lattice ⟨

CMS (8 TeV)1−20.5 fb

)2 (GeV2q2 4 6 8 10 12 14 16 18

FBA

-1-0.8-0.6-0.4-0.2

00.20.40.60.8

1 Data⟩ SM, LCSR ⟨⟩ SM, Lattice ⟨


)2 (GeV2q2 4 6 8 10 12 14 16 18

)2− G

eV× 8−

(10

2 q /

dΒd

0

2

4

6

8

10

12Data

⟩ SM, LCSR ⟨⟩ SM, Lattice ⟨


Figure 4: Measured values of FL, AFB, and dB/dq2 versus q2 for B0 ! K⇤0µ+µ�. The statisticaluncertainty is shown by the inner vertical bars, while the outer vertical bars give the totaluncertainty. The horizontal bars show the bin widths. The vertical shaded regions correspondto the J/y and y0 resonances. The other shaded regions show the two SM predictions after rateaveraging across the q2 bins to provide a direct comparison to the data. Controlled theoreticalpredictions are not available near the J/y and y0 resonances.

9

) (GeV)−µ+µ−π+

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2 2.00 GeV−: 1.00 2q11±Signal yield: 84

DataTotal fitCorr. tag sig.Mistag sig.Background


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CMS (8 TeV)1−20.5 fb2 4.30 GeV−: 2.00 2q16±Signal yield: 145



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CMS (8 TeV)1−20.5 fb2 6.00 GeV−: 4.30 2q

15±Signal yield: 117 DataTotal fitCorr. tag sig.Mistag sig.Background


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CMS (8 TeV)1−20.5 fb2 12.86 GeV−: 10.09 2q



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Figure 2: The K+p�µ+µ� invariant mass distributions for the seven signal q2 bins and thecombined 1 < q2 < 6 GeV2 bin. Overlaid on each is the projection of the results for the total fit,as well as the three components: correctly tagged signal, mistagged signal, and background.The vertical bars give the statistical uncertainties, the horizontal bars the bin widths.

1 < q2 < 6 GeV2

L = 20.5 fb-1


Global fits to b→sll and b→sγ• Recent results on b→s transitions have generated a lot of theoretical activity.

• Global fits: combine many flavour measurements in input and fit for best value of Wilson coefficients

• Best fits to NP contributions to C9, C9’ and C10

22

See also: Altmannshofer, et al: 1503.06199 Ciuchini, et al: 1512.07157 Hurth, et al: 1603.00865

B Æ KmmB Æ K*mmBs Æ fmm

All

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1

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3

C9NP

C 9'NP


All

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C 10NP


All

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C9NP = -C9'

NP

C 10NP=

C 10'NP


All

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1

2

3

C9NP = -C9'

NP

C 10NP=-

C 10'NP

Figure 8: For 4 favoured scenarios, we show the 3 � regions allowed by B ! Kµµ

observables only (dashed green), by B ! K⇤µµ observables only (long-dashed blue), by

Bs ! �µµ observables only (dot-dashed purple) and by considering all data (red, with

1,2,3 � contours). Same conventions for the constraints as in Fig. 7.

only in C9 or (C9, C90) since both sides of the equation vanish trivially. On the other hand,

if one wants to switch on NP in all four coe�cients and preserve some simple pattern

among them, there are four options that may agree with a Z 0 interpretation:

• (CNP9 = �CNP

90 , CNP10 = �CNP

100 ), with a large pull for the b ! sµµ reference fit, but

giving RK = 1 by construction,

• (CNP9 = CNP

10 , CNP90 = CNP

100 ), disfavoured by the data on Bs ! µµ, which prefer a SM

30

from Descotes-Genon, et al: 1510.04239

NP contribution to C9 is favoured

see talk by Sebastien Descotes-Genon


Outlook

• Excellent physics results on b→sγ and b→sl+l- have been coming from LHC and the B-factories.

- probing right-handed currents via photon polarisation

- impressively comprehensive analysis of B0→K*0μ+μ- (and related decays)

- some tension with the SM (P5’) to keep everybody busy

• LHCb is busy accumulating more data in Run 2: after a relatively small increase in statistics in 2015, a doubling of the data sample is expected by 2018.

• The B-factory experiments are still producing impressive results, several years after completion of data-taking. Significant further progress on the e+e- front is not that far off: Belle II expects to take data for physics in 2018.

23

Backups

24


B+→K+π+π-γ analysis

• Fit mES, ΔE, Fisher discr to extract K+π+π-γ signal: 2441 +- 91 +- 50 signal events

• Extract mKππ spectrum (sPlot technique) and perform amplitude analysis to resonant contributions to B→K+resγ: consider 5 resonances: K1(1270), K1(1400), K*(1410), K*(1680),K2*(1430).

• Results of fit to mKππ spectrum:

25


B+→K+π+π-γ analysis • Use mKπ spectrum, along

with Kres fractions from previous fit, to determine Kρ and K*π contributions to final state.

• Model contributions from K*+, ρ0 and (Kπ)0 s-wave (LASS parametrisation)

• From these results, we determine the dilution factor:

26

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