Radiative and Electroweak Penguin B-Decays with the Babar … · 2003. 12. 22. · Penguin B-Decays with the Babar Detector Fabio Bellini ... •No tree-levelcontribution within SM

Roma 19/12/03 Fabio Bellini 1

Radiative and ElectroweakPenguin B-Decays

with the Babar Detector

Fabio BelliniUniversità di Roma “La Sapienza” & INFN Roma I


2XWOLQH

¾Radiative decays:E��!�Vγ and E��!�Gγ�%��!�;Vγ�%�. ��γ�%�ω�ρ�γ

¾Electroweak decays:E��!�VO�O�

�%��!�.O�O�

�%��!�. O�O�

�%��!�;VO�O�

¾Challenging modes with neutrino and/or helicity suppression:�%��!�O�O�

�%��!�.νν


,QWURGXFWLRQ

¾Rare processes involvingFlavour Changing Neutral Current

=> Breaking Flavour Symmetryof the SM

•No tree-levelcontribution within SM

•Dominated by short-distancedynamics

precise test of flavour dynamics sensitivity to New Physics

Roma 19/12/03 Fabio Bellini 4,VLGRUL

6HQVLWLYLW\�WR�1HZ�3K\VLFV�

G.Isidori

Λ: New Phisycs Scale


E��!�Vγ proceeds via flavour changing neutral current

leading order: penguin diagram

7effc

¾E��!�Vγ�%U(E�!Vγ) ≈ ��•�� QRW�VR�UDUH�DFWXDOO\�•Direct Charge Asymmetry ACP very small in SM: ≈ 0.6%•New Physics could change Br and enhanceACP through heavy particles(H,,χχ ) entering theloop

¾Tool for B meson dynamics:•Photon Energy spectrum handle forVub

E�!Vγ

((χχ))


E�!VO�O�

E��!�VO�O� proceeds via flavour changing neutral current

SHQJXLQ

�

ER[

%U�E�!VO�O��∼ αem⋅%U�E�!Vγ� ≈ ��

¾E��!�VO�O�

•Z penguin & box diagrams contribute at leading order. •More dimensions to explore: Minv(l+l-)=q2 & lepton forward-backward asymmetry AFB

=> Ideal testing ground for SM and extensions(2HDM, MSSM, GUT, …?)


E�!GO�O� �E�!GγE��!�GO�O� & E��!�Gγ suppressed by |Vtd/ Vts|2

SHQJXLQ

�

ER[

d d

Vtd VtdVtbVtb

�%5�E�!Gγ� ≈�� : Not seen yet.•Annihilation diagram contributesto %+ �!�ρ+γ

E��!�GO�O�

d

Vtb Vtd

E��!�Gγ


HHII

∼ ∑��

L � &L�µ�OOL�µ�

/RZ�(QHUJ\�(II��+DPLOWRQLDQ

2: matrix element=>long distance&� Wilson coeffcient=>short distanceµ: factorization scale

Operator Product Expansion: separation of long & short distance contributions

• C: encodes information on heavy degrees of freedom(t, W, Z)=> sensitive to NPNLO,NNLO calculations

• O: Exclusive decays => hadronic form factors=>large uncertanties=> σ(Br) ~ 30%, $)% �$&3 more reliable σ~15%

Inclusive decays=> HQE+duality (Γ(B→Xs γ)~Γ(b→s γ))=> non-perturbative contributions under control=> σ(Br) ~ 10%


/RZ�(QHUJ\�(II��+DPLOWRQLDQ

¾Γ�E�!Vγ� ∼ _9 WV9WE_� _&�_

� ��PE�F FRUUHFWLRQ�

•Interesting observables� %U� $&3� γ VSHFWUXP•NLO calculation: %U(%�!;Vγ) =(��±�� •��

(Gambino & Misiak Nucl.Phys. B 611, 2001)

¾Γ�E�!VO�O��GV ∼ _9

WV9WE_� 2�T��P�

E �_&�_��_&

�_��_&

��_��&

� 5H�&

�� PE�F

FRUU��•Interesting observables� %U� $)%� GΓ�GT� GLVWULEXWLRQ•NNLO calculation: (large non perturbative effect in cc resonance region)

%U(%�!;VO�O�): (��±�� •�� T� �� *H9

(��±�� •�� T� !�� *H9�

�Ghinculov, Hurth, Isidori & Yao, 2003)


$QDO\VLV�WHFKQLTXHV¾Exclusive:e,K, µ,γ,π PID and mass and energy constraints: mES, ∆Etheories are not so reliable

¾Inclusive•Semi-Inclusive(e.g. B -> Xsγ with X s =K+n(π))large model dependence•Fully Inclusive(e.g. the γ only in B -> Xsγ)very huge background

∆E =E*B -E*beam

( )22BbeamES PEm −=

e+e- →Υ(4S) → BB


11

Exploit the B-decay isotropy vs the “jet-like” topology of qq eventsUse B properties and shape variables: decay angle, ∆z, cosθThrust, energy flow,ThrustCuts on combination of variables (Fisher Discriminant or Neural Network). :

&RQWLQXXP�EDFNJURXQG�UHMHFWLRQ

NN output:Κ∗γ analysis


12

VE

γE

;V

%γ

% �! ;Vγ %%

TT

%�!;Vγmonochromatic spectrum (Eγ~mb/2) smearead by b-s interaction & confinement =>Fermi motion

mb 4.65mb 4.80mb 4.95

Huge bkgd=> (Á FXW

ODUJH WKHR� HUURU

Eγ(GeV)


Br(B�Xsγ) = (3.88 ± 0.36 (stat) ± 0.37 (syst)+0.43 (model))·10-4

)XOO\�,QFOXVLYH�%�;Vγ

-0.23

13

Data

BB expected events

Integrated to obtainBranching Fraction

Preliminary High energy photon: Emc shower profile consistent withγ hyp., π0 and η veto , lepton tag on other B

Signal region: Εγ [2.1; 2.7] GeV

Dominant Stat error due to ~6fb-1 off-resonance used for continuum subtraction

Dominant Syst error from BB subtraction :(π0 and η from B decays can fake γ)

Β��Xdγ events subtracted using theory prediction: (4.0±1.6)%

hep-ex/0207076

54.4 fb-1


,QFOXVLYH�%�;Vγ ZLWK�VLQJOH�%�EHDP

ee--DD**

ππ

ee++

BBrecoreco

BBrecoilrecoil

XsXs

γγ

Novel technique: reconstruct one B in a fully hadronic decay

¾Advantages:• Breco (recoil) kinematicswell known

⇒Eγ studied in theB rest frame⇒better resolutionon Eγ(no B boost smearing)

• mES distribution on Breco used for a side-band subtraction⇒ no need to use off-resonancedata for continuum bkgd

•Charge & flavour separation•Clean environment =>Eγ lower cut: 1.9 GeV

• Reconstruction efficiency ~ 2.3•10-3

Only B-factoriescould explore this technique


sigtag

alltag

selBreco

sig

S N

NXBBr

εε

εγ ⋅

⋅=→ )(

,QFOXVLYH�%�;Vγ ZLWK�VLQJOH�%�EHDP•Analysis performed in B rest frame

•Photon selection like Fully Incl. analysis +Fisher for continuum suppressionρ veto for BB background

•Signal extracted from a χ2 fit to the Eγ spectrum-bkgd and signalshapetaken from MC-bkgd Normalization fixed in a side-bandregion: E*<1.9 GeV & extrapolated in signal region:

Very Low model dependence ~5%•More statistics =>precision measurement=>Eγshape & ACP

Br(B�Xsγ) = (3.82 ± 0.98 (stat) ± 0.65 (syst)+0.23-0.20 (model))·10-4

Εγ [1.9; 2.7] GeV

81.9 fb-1

Preliminary


&RPELQDWRULDO�ENJG�VXEWUDFWLRQ

•Samples divided in bins of E.•mES distribution of the fully reconstructed B is fitted in each binto properly subtract combinatorial bkgd

carichi e nuetri

MESdistribution for MC bkgd sample


%�;Vγ EUDQFKLQJ IUDFWLRQV

%U�%�;Vγ )∗10−4

no deviations from SM so far:consraints on new physics

Br in particular MSSM scenario Carena et Al. PLB499, 411

BaBar Breco SM prediction: Br(3.73±.0.30)*10-4Gambino &Misiak Nucl.Phys. B 611

No deviations so far: constraints on NP“The most effective NP Killer” G. Isidori

tanβ


%��!�. γ• K ∗+

�Κ+π0 , ΚS0π+ , Κ∗0

�Κ+π−, ΚS0π0

• isolated high energy γ: 1.5 < E*γ < 4.25 GeV

• π0/η veto,

• π,K PID

• K*(892) reconstructed in 4 final states:

0.8 < M(Kπ) < 1 GeV/c2

• BKG suppression against e+e- -> qq(g) ->NN

• Signal extraction : 2-D UML fit to ∆E and mES

E (GeV)∆-0.3 -0.2 -0.1 0 0.1 0.2 0.3

Even

ts /

( 0.0

12 G

eV )

0

10

20

30

40

50

E (GeV)∆-0.3 -0.2 -0.1 0 0.1 0.2 0.3

Even

ts /

( 0.0

12 G

eV )

0

10

20

30

40

50

E"∆A RooPlot of "

(GeV)ESm5.2 5.21 5.22 5.23 5.24 5.25 5.26 5.27 5.28 5.29 5.3

Even

ts /

( 0.0

02 G

eV )

0

10

20

30

40

50

60

70

80

90

(GeV)ESm5.2 5.21 5.22 5.23 5.24 5.25 5.26 5.27 5.28 5.29 5.3

Even

ts /

( 0.0

02 G

eV )

0

10

20

30

40

50

60

70

80

90

"ESA RooPlot of "m

∆∆( ( PP(6(6

––SignalSignal––Generic B Generic B BkgBkg..––Continuum Continuum BkgBkg

.. � �→→..��ππ��

Br ( B0 -> K*0 γ) =(39.2 ± 2.0 ± 2.2) (⋅10-6)

Br( B+ -> K*+ γ ) =(38.7 ± 2.8 ± 2.4) (⋅10-6)

81.9 fb-1

Preliminary

K ∗+� ΚS

0π+


$,6�%��!�. γ �

,QYHVWLJDWH�,VRVSLQ DV\PPHWU\�EHWZHHQ�%� DQG�%��

UHODWHG�WR VLJQ�&��&��

∆�� ± ��± ��%D%DU��IE��

∆�� ± ��± ��%HOOH��IE��)3&3��

60�SUHGLFWV��∆0+ = (8.0 +2.1 −3.2) %

∆�� %5�%��!. �γ��² %5�%��!. �γ�

%5�%��!. �γ��%5�%��!. �γ�τ%�

τ%�

τ%�τ%�

τ%�τ%� �� ± �� >3'*��@

Kagan and NeubertPhys. Lett. B539 227 (2002)

81.9 fb-1

Preliminary


%D%DU6WDWXV�RI�E�!Vγ

%HOOH

Channel BR (⋅10-6) ∫Ldt

===================================================

B -> Xs γ 388 ± 36 ± 37 +43/-23 54.6 fb-1

B0 -> K*0 γ 39.2± 2.0± 2.2 81.9 fb-1

B+ -> K*+ γ 38.7± 2.8± 2.4 81.9 fb-1

B0 -> K*02(1430) γ 12.2 ± 2.5 ± 1.1 81.9 fb-1

B+ -> K*+2(1430) γ 14.4 ± 4.0 ± 1.3 81.9 fb-1

===================================================

B -> Xs γ 336 ± 53 ± 42 +50/-54 6 fb-1

B0 -> K*0 γ 40.9 ± 2.1 ± 1.9 78 fb-1

B+ -> K*+ γ 44.0 ± 3.3 ± 2.4 78 fb-1

B0 -> K*2(1430) γ 13 ± 5 ± 1 29 fb-1

B+ -> φ K + γ 3.4 ± 0.9 ± 0.4 90 fb-1

B+ -> K+π+π− γ 24 ± 5 +4/-2 29 fb-1


% �! . �� γ ��

% �! . �� γ ��

% �! . π γ ��

% �! . ρ γ ��

% �! . φ γ ��

� .πQγ �Q! �� %DU\RQV��γ �≤�� 0RGH�ZLWK�UHVRQDQFHV�H�J��η��η·

� ...πQγ �≠.φγ�� «

6WDWXV�RI�E�!Vγ

��RI�E�!Vγhas been measured exclusively


'LUHFW�&3�YLRODWLRQ�$&3

•Same (Excl. & Semi-Incl Br) analysis: mixed-flavour modes discarded

SM: small ACP (~ 0.6%) , sensitive to non-SM extra contributionsthat might cause CP-violating charge asymmetries as high as 20%

→+→

→−→=

γγ

γγ

KBNKBN

KBNKBNACP **

**

Babar (81.9 fb-1 ) Belle (78 fb-1 ) FCPP03

ACP( B0 -> K*0 γ) -0.069 ± 0.046 ± 0.011 -0.029± 0.054 ± 0.011

ACP ( B+ -> K*+ γ ) 0.074 ± 0.059 ± 0.006 0.054 ± 0.076 ± 0.014

Preliminary

Babar (113 fb-1 ) Belle (140 fb-1 )

ACP 0.025 ± 0.050± 0.015 -0.004± 0.051 ± 0.038

K* γ

Sem-Incl


B�ρ/ω γ

23

B0��ρ0γ, ρ0

��π+π-

B±��ρ±γ, ρ±

��π+π0

B0��ωγ, ω��π+π-π0

78 fb-1

¾Low Br ~1 x 10-6

¾Reco modes:ρ0��π+π-,, ρ + ��π+π0, , ω ��π+ π- π0,

¾520(760)<Mππ(π). <1020(805) MeV

¾Lar ge B background from K * γ ,2% kaon fake at 80% pion efficiency

¾ A 2(3)-UML fit is used to extract signal yields: ∆E , mES, (mρ)

No Evidence of signal, upper limits are set:

B(B0��ρ0γ) < 1.2·10-6 @ 90%CL

B(B±��ρ±γ) < 2.1·10-6 @ 90% CL

B(B0��ωγ) < 1.0·10-6 @ 90% CL

(hep-ex/0306038 submitted to PRL)


B�ρ/ω γ Upper /LPLWV @ 90% CLBaBar BELLE CLEO Theory

(Ali&Parkomenko)

B(B0��ρ0γ) < 1.2·10-6 < 2.6·10-6 < 17·10-6 = (0.49±0.18)·10-6

B(B±��ρ±γ) < 2.1·10-6 < 2.7·10-6 < 13·10-6 = (0.90±0.34)·10-6

B(B0��ωγ) < 1.0·10-6 < 4.4·10-6 < 9.2·10-6 = (0.49±0.18)·10-6

24

Preliminary Preliminary

Assuming (isospin symmetry)A(B��ργ) = A(B±��ρ±γ) = sqrt(2) x (B0

�� ρ 0γ) Combined the upper limit obtainedBr(B�� ρ γ ) < 1.9 10-6

Using (Ali & Parkhomenko Eur. Phys. J. C.23, 89 (2002))Br(B�� ρ γ )/Br(B��K * γ ) =

|Vtd/Vts|2 z2 |1+∆R| (1-mr2/MB

2)3/(1-mK*2/MB

2)3

with z=0.76±0.10, ∆R=0.0±0.2

|Vtd|/|Vts|<0.34 @ 90% CL

-1 -0 .5 0 0 .5 10

0 .2

0 .4

0 .6

0 .8

1

Μ

ρ

η

ksψa

∆MB d

Β∆

s

VubVc b

εkR

(

/ K

)∗

ργγ

ksψa


(OHFWURZHDN�GHFD\V�E�!VO�O�


E�!VO�O��SUHGLFWLRQV

q2

AF

B

¾BF: αεµ⋅%5�E�!Vγ� ≈ �� but much less bkgd than E�!Vγ¾interplay between Z and γ => q2 dependence

• Forward-backward lepton asymmetry AFB(q2) sensitive to non SM effecteven if rates agree(E�!V�OO�γ)

•AFB(q2) needed in addition to Br to disentangle C7 , C9 , C10 contributions

q2SM nonres

*B K µ µ+ −→ J/ψΚ

ψ(2S)K

dΓΓ/d

q2

SUSY models

Ali et al. ‘01


%�Æ .� � O� O�

Reconstruct K +, KsÆÆ π +π-, K*0ÆÆ K + π−, K *+ ÆÆ Ks π+

•Tight lepton ID for: e+e- with p(e) > 0.5 GeV/c,brems recoveryµ+ µ - with p(µ ) > 1.0 GeV/c

•Photon conversionsare vetoed M(ll)>0.2 GeV•Continuum suppressed by Fisher: event shape variables•BB background suppressed by Emiss, cosθB , vertexing•J/ψ and ψ’ veto•Background from lepton miss-identification B ÆÆ h+h- K (*)

vetoed if M(h-K (*)) consistent with D mass

J/ψψ veto ψψ’ veto

Mll [Gev/c2] Mll [Gev/c2]

∆E [G

eV]

∆E [G

eV]

113 fb-1


Signal yield:2-D UML fit tomES & ∆E

%�Æ .�� O� O�

Br= (6.5 +1.4-1.3 ± 0.4 ) ⋅10-7

Submitted to PRL, hepSubmitted to PRL, hep--ex/0308042ex/0308042

8.4σ

113 fb-1

Signal yield:3-D UML fit tomES & ∆E, mKπ

Br= (8.8 +3.3-2.9 ± 1.0 ) 10-7

K*ee = 1.33 K*µµ assumed to compensate q2 =0 pole

3.3σ


4.6

2.2

4.0

significance(σ)

41.4 ± 10.3Sum

12.4 ± 6.2Xs µ+ µ -

29.0 ± 8.3Xs e+e-

yield(± stat)Mode

Br(B → Xs e+e−) = (6.6 ± 1.9 ± 1.91.6) 10−6

Br(B → Xs µ+µ−) = (5.7 ± 2.8 ± 1.71.4) 10−6

Br(B → Xs l+l−) = (6.3 ± 1.6 ± 1.81.5) 10−6

%�Æ ;6 O� O� 5HVXOWV�%DEDU�

•unbinned maximum LH fit to mES

•signal is seen in electron mode

81.9 fb-1

Preliminary

Reconstruct XS as: (K+,Ks) +0-2 π (up to 1 π ο ) (75% of signal)


0

10

20

30

40(a) Xse

+e- (b) Xsµ+µ-

5.2 5.22 5.24 5.26 5.280

20

40

60

(c) Xsl+l-

5.2 5.22 5.24 5.26 5.28

(d) Xse+µ- + c.c.

Mbc (GeV/c2)

Entri

es /

(2.5

MeV

/c2 )

• Published: PRL 90, 2180• signal is seen in both electron

and muonmode • XS :(82% of signal)

5.460.1 ± 14 sum

4.737.3 ±9.7 XS µ µ

3.425.5 ± 11.2 XS e e

significance(σ)yield (± stat)

%�Æ ;6 O� O� 5HVXOWV��%HOOH�

Br(B → Xs e+e−) = (5.0 ± 2.3 ± 1.31.1) 10−6

Br(B → Xs µ+µ−) = (7.9 ± 2.1 ± 2.11.5) 10−6

Br(B → Xs l+l−) = (6.1 ± 1.4 ± 1.41.1) 10−6

60 fb-1


0OO DQG�0;V LQ�%�Æ ;6 O� O�

0�1DNDR /3��

•from a bin by bin fi tto M ES

•no deviation in M(l-l+)•more data => measure AFB


• C9 and C10 can be constrained from Br(BÆÆXs l+ l-)– Ci

NP = Ci - CiSM

– (0,0) if the SM holds. Dots show Extended-MFV model– Strong constraint on C9 and C10 but sgn(C7) is not determined

yet.

C10

NP

C9NPC9

NP

C10

NP

&RQVWUDLQW�RQ�&� DQG�&��

0�1DNDR /3��


%D%DU

%HOOH

6WDWXV�RI�E �!�V�O�O�

&KDQQHO %U �⋅�� ∫LGW

% �! ;VO�O� �� ± �� IE��

% �! .O�O� �� ± �� IE��

% �! . O�O� �� ± �� IE��

��

% �! ;VO�O� �� ± �� IE��

% �! .O�O� �� ± �� ± �� IE��

% �! . O�O� �� ± �� ± �� IE��

Br(% �! . O�O� ) = (�� ± �� ⋅�� ODUJH HUURU GXH WR IRUP IDFWRUV�

Br(% �! . O�O� ) = (�� ± �� ⋅�� $OL HW $O� �� 11/2

Br(% �! ;VO�O� ) = (�� ± �� ⋅�� σ RII� HUURU VWLOO ODUJH�


'HFD\V�ZLWK�neutrino and/or helicity suppression


Hadronic tag: %��!'� �;KDG Semileptonic Tag: %��!'�Oν(π,γ)

%� Æ .νν •Theoretically cleaner than B -> K*ll because of no cc resonance effect•Only one K in the final state( require p*>1.25GeV)• 2 umeasured ν’s ⇒ Reconstruct one B& look for signal in the recoil side

Eextra

tagging efficiency:~2 · 10-3 tagging efficiency:~5·10-3

D0 =>K-π+, K-π+ π+ π-, K-π+ πo

Remaining neutral Energy (GeV)mES (GeV)


80.7 fb-1 :Br < 1.05 x10-4 @ 90% CL

Combined limit @ 90% CL < 7.0 x 10Combined limit @ 90% CL < 7.0 x 10--55 hephep--ex 0304020ex 0304020

50.7 fb-1: Br< 9.4x10-5 @ 90% CL

SM Expectation: (3.8 +1.2 -0.6) x 10-6 (Buchalla, Isidori,2000)

%� Æ .νν Semileptonic B tag

M(D

0 )-M

(D0

PD

G)

σM

(D)

Hadronic B tag

PP(6(6

signal box

side-band

mES (GeV)Remaining neutral Energy (GeV)


!�)&1&��+HOLFLW\ VXSSUHVVHG��ERG\�GHFD\�LQ�60

�

%5�LQ�60� %�!τ+τ− ≈ ��⋅ ��

%�!µ+µ− ≈ ��

%�!H+H− ≈ � ⋅ ��

%�!Hµ IRUELGGHQ LQ 60� EXW SRVVLEOH LQ 686< RU /HSWR�4XDUN PRGHOV�

1RW REVHUYDEOH� EXW HQKDQFHPHQW E\ �� RUGHUV RIPDJQLWXGH LQ �+'0 RU = PHGLDWHG )&1& PRGHOV�

%� Æ O��O�


%� Æ O��O� �%DEDU��%HOOH�

[GeV]ES

m5.2 5.22 5.24 5.26 5.28 5.3

E [GeV]

∆

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

BABAR

Β e e+ −

[GeV]ES

m5.2 5.22 5.24 5.26 5.28 5.3

E [GeV]

∆

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

BABAR

Β µ µ+ −

[GeV]ES

m5.2 5.22 5.24 5.26 5.28 5.3

E [GeV]

∆

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

BABAR

Β e µ+ +−−

e+e- µ+µ− e+µ−

Both Belle(78 fb -1) and Babar (54.4 fb -1) observe no events

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

5.2 5.22 5.24 5.26 5.28 5.3

ee

Mbc(GeV/c2)

∆E(G

eV)

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

5.2 5.22 5.24 5.26 5.28 5.3

eµ

Mbc(GeV/c2)

∆E(G

eV)

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

5.2 5.22 5.24 5.26 5.28 5.3

µµ

Mbc(GeV/c2)

∆E(G

eV)

•Tight lepton ID•pmis and multiplicity cut•continumm bkgd=>event shape•bkgd:leptons in cc eventsπ−µ mis-id (µ- µ+ )2γ processes (e+e-& e+µ)-

•bkgd estimated on datasidebands & extrapolated in the signal mES box

Belle

Babar


6WDWXV�RI�%�→ O�O�

%D%DU

%HOOH

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%�!H�H� � �� ⋅ �� IE�� %DEDU

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