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Rare B Decays Chris Parkes SUPA Postgraduate Lectures Introduction Radiative decays b  s  b  d  Electroweak Penguin b  sl + l - Rate Forward backward.

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Presentation on theme: "Rare B Decays Chris Parkes SUPA Postgraduate Lectures Introduction Radiative decays b  s  b  d  Electroweak Penguin b  sl + l - Rate Forward backward."— Presentation transcript:

1 Rare B Decays Chris Parkes SUPA Postgraduate Lectures Introduction Radiative decays b  s  b  d  Electroweak Penguin b  sl + l - Rate Forward backward asymmetry Final states with neutrinos

2 B mesons / Baryons Masses known to a few MeV and various excitations Baryons In spectator model b lifetimes would all be the same –Non-spectator effects give rise to a hierarchy Theory and experimental pattern in agreement Evidence 1998 Accurate Mass 2005

3 What do we mean by a rare B-decay ? All decays ‘rare’ as decays out of generation Flavour Changing Neutral Currents (FCNC) are even more suppressed as forbidden at tree level in SM –b  s –b  d Rare in this context means not b  c

4 Feynman Diagrams for B Processes

5 FCNC B decays Forbidden at tree level in SM Occur via Penguin / Box diagrams Sensitive to New Physics heavy particles –SUSY, non-SM Higgs

6 Operator Product Expansion (OPE) A method of formulating an effective theory of the interaction Feynman diagram full process description Or Effective point-like vertex e.g.  decay Contains : 1)CKM elements V CKM 2)Matrix Element Operators non-perturbative - Lattice Calculations, HQET 3)Wilson Coupling Coefficients C i (there are 10) Aim to measure these – sensitive to new physics Form an effective weak Hamiltonian, effective vertices multiplied by effective coupling constants

7 bsbs

8 Discovery of b  s , B  K*  FCNC CLEO, 1993 (PRL 71,674) Later extended to inclusive b  s  rate measurement Rate sensitive to new physics

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12 Current Result (BaBar/Belle)

13 bdbd

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15 Discovery of b  d 

16 And… b  d gluon (g  )

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20 Forward Backward Asymmetry of leptons sensitive to New Physics, determine C 7 C 9 C 10

21 Determined with low precision Requires a larger data sample LHCb or Super-B Factory

22 Channels with neutrinos

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26 B (s)   +  -

27 Really really rare! SM box SM Penguin Sensitive to New Physics in SUSY models

28 B (s)   +  - Unique Experimental signature Easy to identify / trigger – good for ATLAS/CMS Really really rare! Needs LHC data sample for SM B s 3.5x10 -9, B d 1.0x Current limits from Tevatron

29 Information Sources Varenna CP violation school 2005 –http://varenna05.pi.infn.it/ –Slides taken from talks of: –Rare B Decays – H. Aihara OPE & Wilson Coefficients, A. Buras hep-ph/


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