Rare B and decays and searches for New Physics Roger Barlow Manchester University and New (preliminary) results, mostly but not entirely from the B factory

Rare B and decays and searches for New Physics

Roger BarlowManchester University and

New (preliminary) results, mostly but not entirely from the B factory experiments

Belle and BaBar.

Roger Barlow: Rare B and tau Decays and New Physics

Slide 2

Why look for Rare Decays?

Our chance to see them is when the Standard Model

amplitudes are small:

Rare decaysu

bH+ +

If new particles are to appear on-shell at high energy

colliders, they must appear in virtual loops and affect

amplitudes


Slide 3

What made it possible?

Measuring Branching ratios of ~10-6 needs millions of events

Physics progress possible thanks to machine physicists at SLAC and KEK

• designed and built B factories operating in a new high-current regime,

• continually faced and overcame new problems and challenges.

• design luminosities met and exceeded.


Slide 4

Huge backgrounds from other Bs

and e+e- qq

Use of E=EB-Ei

and MES=EB2-(pi)2

“Blind Analysis”

Tune cuts without looking in the MES-E ‘signal box’

Use data sidebands

(rather than Monte Carlo) to estimate background

“Finding a needle in haystack.”

MES(GeV/c2)

E(G

eV)

(taken from Sekula’s talk. One

of many)


Slide 5

Continuum suppression from

combined information from shape variables

“Single-B beam” technique:

Reconstruct one “tag” B in a common decay mode

(hadronic or semileptonic). Remaining particles must

also form a B

Limits from N= S + b

N small

Uncertainties on , b

Other Experimental techniques


Slide 6

Contents• B decays

– Leptonic– Radiative

• bs and bs l + l - • bd and bd l + l -

– Hadronic Charmless• Branching Fractions• Charge Asymmetries• Polarisation

• Tau decays


Slide 7

B Decays to leptons

Proceeds through one or two weak bosons with strong CKM suppression – door open for NP particles to contribute

Free of hadronic uncertainties in final state

u

bH+ +

+

-

b

d,s

u

bW+ +

~

b

d,sW

W

u,c,t

-

+

Plus many other

diagrams


Slide 8

B CP, Rare decays, CKM V

Browder (Belle)Sekula (BaBar)

Important as W (suppressed by Vub) can be replaced by charged

Higgs, etc

Difficult due to neutrinos in the final state

SM prediction (1.59 0.40) x 10-4 (depends on fB and Vub)

tag with fully reconstructed B mesons (180 channels)

Tag with BD(*)l


Slide 9

B

Identify possible

in common decay mode

Look at extra calorimeter energy

(validate with for D*l)

H+?

CP, Rare decays, CKM V Browder (Belle)Sekula (BaBar)

5.34.717.2

Extra E(GeV)

Extra E(GeV)


Slide 10

Results

439.056.046.049.0 10)79.1()(BF

B

Belle and BaBar results are similar. Agree within errors

Can be combined (R. Faccini) to give

(1.36 0.48)x10-4

(new)BF(B++)= (0.88 0.11) x10-4

BR< 1.80 10-4 @ 90%CL

(revised). 3.5 significance

+0.68-0.67

BF(B++)


Slide 11

ImpactLimits on e.g. 2 Higgs

doublet model: W.S.Hou, PRD 48, 2342 (1993)

SM prediction enhanced/reduced by factor rH

CP, Rare decays, CKM V

Browder (Belle)

Or: Within the SM, use the value of BF(B++) to give a

measurement of fB


Slide 12

B and e

Helicity Suppressed

Use hadronic tags: B fully reconstructed as B to D(*) X

Lepton is monoenergetic in signal-B rest frame

Limits (@ 90% CL)

<7.9 x10-6 for e (SM ~ 10-12)

<6.2 x10-6 for (SM ~ 10-7)


Sekula (BaBar)

Lepton momentum in B frame (GeV/)


Slide 13

B0 to l l

FCNC and helicity suppressed, but an initial state photon allows helicity flip

SM predictions of order 10-10

(10-15, 10-11 respectively without the )See 0 events for e, 3 events for (but

compatible with background)Limits (at 90% CL)BR(Bee)< 0.7 x 10-7

BR(B)< 3.4 x 10-7

(simulated)


Sekula (BaBar)


Slide 14

B K*

Tag on other BIdentify K*Look for extra energySM prediction ~1.3 x 10-5

Signal is BK* + missing mass. (Could be light dark matter particle: publications by M. Pospelov et al.)

0 *0 4( ) 3.4 10B B K


Browder (Belle)

(at 90% C.L)

Extra Calorimeter Energy (GeV)


Slide 15

B0 +-

Expected BG 0.88 1.86

Events seen 1 2

BF (95% CL) <1.0x10-7 <3.0x10-8

B0s +- B0

d +-

CP, Rare decays, CKM IV-V

Farrington (CDF)

Strauss (DØ)

Sivoklokov (ATLAS)

Langenegger (CMS)

Ruf (LHCb)

DØ analysis not yet complete. Combines Bs and Bd. Expect limit ~ 2 10-7

Have result on BR( B ) BR < 4.1 x10-6 @ 95%

LHC experiments will do this very

precisely

SM predicts

Bs:(3.40.5)x10-9 Bd:(1.00.1)x10-10

NP can boost this by ~100


Slide 16

Radiative B decays

FCNC process suppressed in SM: sensitive to new particles in loops

bs Inclusive and many exclusive measurements

bsl+l -: More information from kinematics

bd : strongly suppressed but open to different physics

bd l+l -: on the way


Slide 17

B s inclusive

‘Fully Inclusive’ and ‘sum of exclusives’ (38 modes)

Heavy Quark Physics I &III

Hurth (Theory)

Convery (BaBar)

NLO calculation (3.61 ) x10-4

result: (E >1.9GeV) = (3.67 0.29 0.34 0.29) x10-4

HFAG average

(3.55 0.24 0.03) x10-4 +0.09-0.10

+0.37 -0.49

Branching Fraction now well measured. Theory and experimental error similar

Not much room for New Physics here

Constrains model builders


Slide 18

B s exclusive

• Lots of channels – Branching Fractions measured – CP violating asymmetries measured If nonzero these would be a signature of New Physics

Heavy Quark Physics III Limosami (Belle)

Example: B K0s0

t(ps)


Slide 19

B Kl l B K*l l

Standard Model Amplitudes have 3 parts with different kinematics. Check out each

separately through Wilson Coefficients:

Photon C7

Vector EW C9

Axial EW C10

Dilepton mass q2

CKM factors x Ci(q2) x local operators

CP, Rare decays, CKM VI Kovalskyi (BaBar)

BSM VI

Hamel de Monchenault

BKll (46 events)

E(GeV)MES(GeV/c2)


Slide 20

CP, Rare decays, CKM VI

Kovalskyi (BaBar)

K*ll Asymmetry as a function of q2

Angular variables e.g.*: angle of l l pair in their rest frame. C10 interferes with C7/C9 to

give asymmetry


Slide 21

B d

First observation of B+ +

CP, Rare decays, CKM VI Kovalskyi (BaBar)

B++

B00

MES(GeV/c2)


Slide 22


Kovalskyi (BaBar)

b

d,s W

W

tb

t

d,s

t

ds

|Vtd/Vts|=0.171+0.018

-0.021

+0.017

-0.014

Compare with BK*

Same CKM elements as mixing – but a non-trivial test


Slide 23

B l + l -

Prediction: few 10-8

Measure B + + l +l - and B0 0 l + l - with l =e or (and e - )

Total limit 7.9 x 10 -8 at 90% CL for B+

( twice B0)Amazing to be probing at

this level


Kovalskyi (BaBar)

MES(GeV/c2)MES(GeV/c2)

E(G

eV)

E(G

eV)


Slide 24

Charmless Hadronic Decays

• Many modes• Will present collected branching ratios• Will present measurements of time-integrated

CP violation ACP: they follow on directly from differences in charge conjugate decay states – from the B+/B- difference - trivial– From self-tagged neutral modes – trivial– From C part of CP+mixing fit – nontrivial but standard


Slide 25

ExamplesHeavy Quark Physics I

Dragic (Belle)

Bona (BaBar)

MES(GeV/c2)MES(GeV/c2) E(GeV)


Slide 26

2 body -K combinations

Results on many other decays. See talks by Dragic, Bona, Latham and Schümann in Heavy Quark Physics Session I

Heavy Quark Physics I Dragic (Belle)

Bona (BaBar)


Slide 27


Slide 28

B K+- /K-+

Direct CP violation

Experiments agree:

BaBar:

ACP=-0.108 0.0240.007

Bel

ACP=-0.093 0.0180.008

0B0

B

CP, Rare decays, CKM IV

Di Marco (BaBar)

Unno (Belle)


Slide 29

Direct CP in K

Competing amplitudes with different strong and weak phasesACP should be the same for K+- and K+0 (Gronau: hep-ph 0508047)

Current averages (HFAG)ACP (K+-)=-0.093 0.015ACP (K+0)=+0.047 0.026

Difference 0.14 0.03 – a long way from zeroMaybe colour-suppressed trees are responsible

Maybe New Physics


Slide 30

Lipkin Sum Rule

RLipkin=2

(B+K+0)+(B0K00)

(B+K0+)+(B0K+-)From isospin and assuming the b s penguin diagram dominates R should be 1+O(10-2)

Obtain (HFAG average)

RLipkin=1.06 0.05(Was 1.25 0.10 in 2003)


Slide 31

BK ratios

Can form many ratios, especially(A Buras, R Fleischer et al, Phys J C 45 (701-710) 2006)

Rn=(K+ -) Rc=2 (K+ 0)

2 (K00) (K0+)

Heavy Quark Physics I Dragic (Belle)

Obtain (HFAG averages)

Rn=0.99 0.07

Rc=1.11 0.07

Agree with each other

And with SM predictions

The “K puzzle” is no more


Slide 32

The Polarisation PuzzleB V V decays are spin 0 to spin1+spin1

Should be 100% longitudinally polarised (if tree or penguin dominates)

Measurements confute this – for heavier V especially

Needs to be understood – affects CP decomposition

More data now available


Slide 33

B 00

See 98 22 events

- 3 significance

BR (1.16 0.27)10-6

Fit longitudinal polarisation fl= 0.86 0.05

Measurement needed for B 0 +- , used for alpha

Informs penguin uncertainty in determination

CP, rare decays, CKM III

Telnov (BaBar)

+32

-31

+0.36 -0.37

+0.11

-0.13

MES(GeV/c2) E(GeV)


Slide 34

B K* and f(980)K*

fL around 0.5, as in B K* as opposed to ~1 from simple models

Heavy Quarks I

Bona (BaBar)


Slide 35

More on B to V V

CDF measure longitudinal polarisation in K*, K*

Confirm BaBar and Belle results that polarisation is not 100%

on the way

CP, rare decays, CKM VI

Bussey (CDF)

M(K) (GeV)


Slide 36

Rare Tau Decays

Search for New Physics in decays with Lepton Flavour Violation

The B factories are also factories

(+ -) = 0.89 nb at s = M() Total sample of ~1.5 billion tau leptons

BSM VI

Hayasaka


Slide 37

Compendium of resultsMode x10-7 Mode x10-7

Belle 0.45 lll 1.13.5

e BaBar 1.1 +ee BaBar 1.1

Belle 0.65 ee+ Belle 1.9

e Belle 0.92 lhh BaBar 0.74.8

' Belle 1.3 + BaBar 0.7

e' Belle 1.6 lV0 Belle 2.07.7

Belle 1.2 0 Belle 2.0

e Belle 0.80 BaBar 0.59

Ks Belle 0.52 BaBar 0.58

eKs Belle 0.60 BaBar 0.72

BaBar 1.5

BSM VI

Hayasaka


Slide 38

General techniques

Divide event into two hemispheres

‘Tag side’ usual 1prong (e, , , ) or 3 prong decay.

Different analyses use different tags, trading purity for numbers.

‘Signal side’ with no neutrinos. Powerful energy/momentum constraint.

ee

generic decay

signal event


Slide 39

l l K0

l is or e. Theoretical predictions vary

from ~10-40 for SM (with mixing) upwards

New 90% CL limits

Br ( - e - ) < 12 x 10-8

Br ( - - ) < 4.1 x 10-8

Br ( - e - KS) < 5.6 ×10-8

Br ( - - KS) < 4.9 ×10-8

(hep-ex/0605025)

426

TeV160

tan100.3)(

SUSYM

Br

Belle result

BaBar result

Excluded re

gion

BSM VI

Hayasaka

Tan


Slide 40

- -, K -, -, K –

Look for B-L conserved processes as allowed in the Standard Model

Look for B-L violating processes as Baryogenesis may need them

Channel B-L Background N @90% CL

- - C 0.420.42 0 <5.94 10-8

- - V 0.560.56 0 <5.76 10-8

-K - C 0.260.26 0 <7.19 10-8

- K - V 0.120.12 1 <14.6 10-8

Decays to non-strange baryons ruled out through proton lifetime measurements

BSM VI

Hayasaka

E(G

eV)


Slide 41

in and 3 modes• Limit 1.6 x10-7 @ 90% CL

(BaBar)• 0.65 x10-7 @ 90% from Belle

MSSM prediction

%

%

%

%

BSM VI

Hayasaka

Tan

MA(GeV/c2)


Slide 42

Y(1S)CLEO result on Lepton flavour violation

Detect through decay to e

BR< 6.2 10-6

LFV Scale >1 TeV

(e)

BSM VI

Besson(CLEO)

p/Ebeam

p e/Ebe

am


Slide 43

Putting it all togetherAn example: MSSM

parameter space

Isidori and Paradisi

hep-ex 0605012

One set of Parameters {,AU, sparticle masses}

Restrictions on MH, Tan

Due to bs

Bs

g-2

MB

B

BSM VI

Hamel de Monchenault

M(H+)

Tan


Slide 44

Conclusion

BaBar and Belle are probing physics at the TeV scale, exploring parameter spaces of proposed New Physics models

Limits on Higgs Masses, Tan , SUSY particles.

Precision Frontier and Energy Frontier are Complementary. LHC results will benefit from Rare Decay information.

Standard Model beginning to be heavily stressed

A SuperB factory would stress it even further


Slide 45

Many more results at next year’s conference(s)

We look forward to welcoming you to Manchester next year


Slide 46

Backup slides


Slide 47

Exp. Needs: single B beams

Lots of modes have several and need beams with a single, monochromatic B: B, B, BK,…

Fully reconstruct one of the Bs and study the remaining of the event closed kinematics, missing energy reconstruction

Semileptonic D(*)l(n)5K/fb-1

Hadronic D(*) X3K/fb-1 efficiency purity

Tag types

X=n+m0+pK+qKs Pioneered by BaBar


Slide 48

New Physics Implications

SO(10) modelDermisek et al

hep-ph/0507233

CP, Rare decays, CKM IV Farrington (CDF)

M1/2(GeV)

(G

eV)


Slide 49

What is a rare decay?Experimental definition:One which has not been seen, or only just

been seen for the first timeTheoretical definition:One which, in the standard model, is either

absolutely forbidden or strongly suppressed: FCNC, helicity, small CKM element.

(bc is big, so everything else is small)


Slide 50

HFAG ACP

Documents

Rare B and decays and searches for New Physics Roger Barlow Manchester University and New (preliminary) results, mostly but not entirely from the B factory