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Testing the SM with penguin-dominated B-decays. Amarjit Soni HET,BNL (soni@bnl.gov). Outline. How good a null test is this? How well does the penguin-dominate? Possible dynamical enhancement of u-quark ? Why (LD)FSI has become a significant concern? How can we tackle this complication?

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testing the sm with penguin dominated b decays

Testing the SM with penguin-dominated B-decays

Amarjit Soni



  • How good a null test is this?
  • How well does the penguin-dominate?
  • Possible dynamical enhancement of u-quark ?
  • Why (LD)FSI has become a significant concern?
  • How can we tackle this complication?
  • How well can we exploit correlation between

ΔSf (=Sf – SψK ) and Cf ?

  • Can we make stronger statement about the sign of ΔSf ?
  • Are there (theoretically) problematic modes?
  • Averaging issue
  • Summary and Conclusions


brief recapitulation basic idea
Brief Recapitulation: Basic Idea

Dominant decay amp.has

0 weak phase [just as in

B->ψKS] up to O(λ2)

brief remarks on the old study with london plb 97
Brief remarks on the old study(with London, PLB’97)
  • Originally motivated by the thenCLEO discovery of
  • Huge inclusive (see Browder..) as well as exclusive
  • (see J. Smith…) Brs. into η’
  • Suggest with Atwood(PLB97;PRL97) use of η’ Xs(d)
  • for search of NP via DIRCP as in SM expect very small
  • With London suggest use of MICP in [η’ , η ,π0,ρ0,ω,φ….]KS to test CKM-paradigm via sin2φ1(β)
  • Present simple (naïve) estimates of T/P …for
  • All cases T/P <0.04
  • Due to obvious limitations of method suggest conservative
  • Bound ΔSf <0.10 for the SM

For DIRCP see also Hou&Tseng,



J. Smith@CKM05

WA ~ 2.7σ

averaging issue are we making a mountain outa anthill
Averaging issue:Are we makinga mountain outa anthill?
  • I am rather sceptical and concerned about

averaging over many small deviations,

leading to ~3.7 σ ….On the other hand,



null test s
Null Test(s)
  • In light of B-factory results (existing exptal info+lattice+phenomenology)-> deviations from CKM-paradigm due BSM-CP-odd phase(s) are likely to be small-> should develop Null Tests
  • Since CP is not an exact symmetry of SM->No EXACT NULL TESTS-> Need “Approximate Null Tests” (ANTs).
  • In b->s transitions, penguin-dominated B-decays are a powerful ANT
  • W(“worthiness”)=C(“cleanliness”) X S(“sensitivity”)=4.5* X 5*
  • ANT: In large class of modes such as (π0,ρ,ω,η’,φ,f0,K0K0…)K0 , (penguin/Total) ~ 1 -> ΔSf ~0
  • Summary of early (London + AS, PLB’97) study….
  • ΔSf < 0.1 in the SM (for modes discussed therein)
  • Summary of Recent Reaxmination (Cheng,Chua+AS,hepph/0502235….) , ΔSf > 0.1 most likely due BSM-CP-odd phase (for many modes)
a possible complications large fsi phases in 2 body b decays
A possible complications: large FSI phases in 2-body B decays
  • The original papers predicting ΔSf=Sf - SψK ~0

used naïve factorization ideas; in particular FSI

were completely ignored.

A remarkable discovery of the past year is that direct

CP in charmless 2-body modes is very large->

(LD)FS phases in B-decays need not be small


Non-perturbative model dependence becomes



B  K

All rescattering diagrams contribute to penguin topology,

dominated by charm intermediate states

fit to rates  rD = rD*  0.67

 predict direct CPV

Should reduce model dependence

Significantly for CPV




1.Note in SD, ΔS switches sign bet. ω,ρ for us no change

2. LD rescattering effects on S & C are highly correlated and similarly

C’s of isospin partners are correlated -> many testable predictions,e.g

LARGE (13%)DIR CP for ω KS & HUGE for ρ KS (~ -46%)






  • Only LD uncertainties due to form-factor cutoff are shown here.

Total errors=SD+LD, for example,

  • FSI yields correct sign and magnitude for A(+K-)
  • P/T|SD=0.12 exp(-i177), P/TSD+LD=(0.140.01)exp[i(1478)]

More remarks

& ρ0KS

May be a good


Based on our study it seems difficult to accommodate

ΔS>0.10 within the SM at least for KS[ή,φ]

summary 1 of 2
Summary (1 of 2)

1) Penguin dominated B-decays (b->s) are very useful “ANTs” of SM;

for many modes ΔS>0.10 difficult to accommodate in SM.

2) The η’ KS is esp. clean…due dominance of Penguin (huge Br), which

was in fact the original motivation for suggesting the η’ ; Model calculations show ΔS(η’ KS )~0.01. Since expt. Error for η’ KS

is smallest (0.11), prospects for precision for this mode seem promising.

3) S-C correlation provides a very useful check On the models -> improved expt. measurements should lead to improvements in the models -> other modes may also become useful.

4) Noteable predictions of our model: large dir.CP in [ π,ρ] K- , [ρ,ω]KS

5) The sign of ΔS in our (and several other) model(s) tends to be positive

with small central value (compared to largish ) errors; thus conclusive

statements regarding the sign are difficult to make (Exptal. sign of ΔS

tends to be negative!)

sign of s in the sm
Sign of ΔS in the SM


η’KS .01(.01,-.01) .00(.00,-.04)

φKS ..020(.004,-.008) .02(.01,-.01) .03(.01,-.04)

πKS .009(.001,-.003).07(.05,-.04) .04(.02,-.03)

summary 2 bottomline
Summary (2):Bottomline

Most of the effect currently is driven by

the largish ΔS for η’ KS . If New Physics

is responsible for this then NP MUST

show up in numerous (b ->s) channels

e.g. η’ K- , φ[K0,K-…](*), affecting mixing,

dir and triple-corr CP…AND BS physics.

Also, in all liklihood, radiative ,

leptonic (b->s) should also be effected making

Expts. With higher luminosities extremely

rich and exciting!