New Physics on Rare and Doubly CabibboSuppressed D Decays - PowerPoint PPT Presentation

Title: New Physics on Rare and Doubly CabibboSuppressed D Decays


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New Physics on Rare and Doubly Cabibbo-Suppressed
D Decays
Chuan-Hung Chen
Department of Physics, National Cheng-Kung
U., Tainan, Taiwan
pp7_at_08.06.07.ntu.tw
In collaboration with C-Q Geng S-H Nam

• Evidence for D0?D0bar mixing the implications

• New physics on D0 ? ?? K

• Summary

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• P?Pbar oscillations are important

• In the SM, FCNC induced from loop effects, box
  diagrams

-- GIM mechanism to K?Kbar mixing, ??mK
-- Heavy top-quark mass enhancement to
B?Bbar mixing, ?mBq
-- Except D?Dbar mixing, K ? Kbar, Bq ?Bqbar are
observed

• Due to these effects induced from loops, they
  are sensitive to
• the new physics, e.g.

-- New CP violating phase on
-- New Physics on
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• How is D0?D0bar mixing ?

• Strong GIM cancellation, no heavy quark
  enhancement,
• short-distance effects are negligible
  long-distance effects are dominant

• CPV is negligible

• With SU(3)F limit, it vanishes

• Non-zero contributions are associated with SU(3)
  breaking, i.e. ( ms )n

• Heavy-quark effective theory with OPE

• Georgi (92),

• Bigi Uraltsev (01),

• Exclusive approach,
• Donoghue, Golowich, Holstein, Trampetic
  (86) Petrov (97)
• Falk, Grossman, Ligeti, Petrov (02)

with large uncertainity
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• Evidence for D-Dbar mixing observed by

• Babar, arXive hep-ex/0703020, PRL98, 211802
  (07)
• Belle, arXive hep-ex/0703036, PRL98, 211803
  (07)

• With doubly Cabibbo-suppressed (DCS) decays D0?
  K ??

mixing
Interference
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• No signal for CP violation

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• With singly Cabibbo-suppressed decays D0? K K?

• No signal for CP violation

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• New physics on doubly Cabibbo-Suppressed (DCS)
  D0 ? ?? K

• In the SM

• The definition of RD

• With SU(3) limit,

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• Factorization assumption

Babars result in hep-ex/0703020
Indication of new physics
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• Left-right model on DCS D decay

• Left-right Model SU(2)L ? SU(2)R ? U(1)X

-- Two charged gauge bosons WL and WR
-- Both will mix to be
W1 ? WL
-- Besides CKM matrix for left-handed quark, now
we have similar flavor mixing effects for
right-handed quark
-- LR symmetric model, gLgR, V(L)V(R) , the
contributions will be much smaller than those
in the SM
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• Non-manifest LR model,

Langacker Sankar, PRD40,89 London Wyler,
PLB232, 89

• The relative size between SM and LR models

• all the hadronic effects are the same,

• if destructive interference happens

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• New physics (NP) on lifetime difference in
  D?Dbar mxing

• Golowich, Pakvasa, Petrov proposed that the
  lifetime difference could
• be sensitive to new physics. The idea is as
  follows

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• effective interactions with Operator product
  expansion (OPE)

• The leading term in the OPE is given

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• In the SM, only O1 and O2 have the contributions

• SM result from short-distance is

-- proportional to x3s, vanished in SU(3)F limit
-- result of x3s displays the strong cancellation
from GIM mechanism
-- y(LO) 10?8
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• Non-manifest Left-right model on lifetime
  difference in D0

V(L)cs O(1)
V(R)us O(1)
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• With leading OPE, the result of LR mixing effect

With the values of parameters as
World average, A. Schwartz in FPCP
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• Summary

• Evidence of D-Dbar mixing implies

• y ?? O( 10?2 )

• If CP violation in D-Dbar mixing is non-zero,
• it should be small

• Improved measurement on RD is necessary for new
  physics

• Left-right model has important effects on RD and
  
• lifetime difference in D?Dbar mixing