Diapositiva 1

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THE ROLE OF LATTICE QCD IN FLAVOR PHYSICS

• OUTLINE
• Flavor physics and its motivations
• First row unitarity and the Cabibbo angle
• The unitarity triangle analysis
• New Physics

see also talks by M.Wingate (LQCD) I.Shipsey
(Exp.)
Special thanks to P.Gambino, L.Giusti,
G.Isidori, S.Sharpe, and all the
members of the UTfit Collaboration
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THE STANDARD MODEL A LOW ENERGY EFFECTIVE THEORY
CONCEPTUAL PROBLEMS

• CONCEPTUAL PROBLEMS The most obvious
• Gravity MPlanck (hc/GN)1/2 1019 GeV

PHENOMENOLOGICAL INDICATIONS
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MOTIVATIONS FOR FLAVOR PHYSICS

• We do not understand flavor physics
• Why 3 families? Why the hierarchy of masses?

• 10 parameters in the quark sector (6 mq 4 CKM)

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PRECISION ERA OF FLAVOR PHYSICS
EXPERIMENTS
We need to control the theoretical input
parameters at a comparable level of accuracy !!
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2 FIRST ROW UNITARITY AND THE CABIBBO ANGLE
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Vud2 Vus2 Vub2 1 The most stringent
unitarity test
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The NEW experimental results
BNL-E865 PRL 91, 261802 (and Moriond 04)
KTeV hep-ex/0406001
KLOE Moriond 04
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Theory 2 recent lattice contributions
1) LEPTONIC DECAYS
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2) SEMILEPTONIC Kl3 DECAYS Precise (quenched)
calculation of f(0), SPQcdR 2004
The largest th. uncertainty from
f(0) 1 - O(ms-mu)2
Ademollo-Gatto theorem
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ChPT The complete O(p6) calculation
Post, Schilcher (2001), Bijnens, Talavera
(2003) C12 (µ) and C34 (µ) can be determined
from the slope and the curvature of the scalar
form factor. Experimental data, however, are not
accurate enough.
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The Lattice QCD calculation
Talk by F.Mescia (and hep-ph/0403217)
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3) Chiral extrapolation
The dominant contributions to the systematic
error come from the uncertainties on the q2 and
mass dependencies of the form factor
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3 THE UNITARITY TRIANGLE ANALYSIS
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THE UNITARITY TRIANGLE ANALYSIS
5 CONSTRAINTS 2 PARAMETERS
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Bayesian and frequentist 2 stat. approaches
and 2 dedicated workshop
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The Bayesian approach
The Frequentistic approach
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p.d.f
?logL
In the frequentistic approach the selected region
does not have a precise statistical meaning ( at
least 95 ). Nevertheless, if same likelihood
are used, the output results are very similar
Estimates of the uncertainties for lattice
determinations should be given by the lattice
community
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Unitary Triangle Analysis LQCD INPUT PARAMETERS
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Stat., Match.
Quench., Chiral
Error 7 16
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Stat Syst
Error 14
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Stat.
Syst.
Error 3 5
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PRECISION FLAVOR PHYSICS ON THE LATTICE
Vcb from exclusive semil. B-decays
Exp.
Theor.
Error 2.6 4.5
Mainly from LQCD, FNAL Compatible with QCDSR
and HQET Quark Model
FB?D(1) 0.91 0.04
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PRECISION FLAVOR PHYSICS ON THE LATTICE
Vub from exclusive semil. B-decays
Exp.
Theor.
Error 7 14
CLEO 2003
LATTICE
15-20 WITHIN QUENCHING
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Exclusive/Inclusive Vub
Exclusive
Inclusive
?
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Unitary Triangle Analysis RESULTS AND
PERSPECTIVES
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Collaboration
www.utfit.org
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FIT RESULTS
Sin2a 0.14 0.25
Sin2ß 0.697 0.036
? (61.9 7.9)o
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INDIRECT EVIDENCE OF CP VIOLATION
3 FAMILIES - Only 1 phase - Angles
from Sides
Sin2ßUT Sides 0.685 0.047
Sin2ßJ/? Ks 0.739 0.048
Prediction (Ciuchini et al., 2000) Sin2ßUTA
0.698 0.066
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Prediction for ?ms
WITH ALL CONSTRAINTS
?ms NOT USED
?ms (18.0 1.6) ps-1
?ms (20.5 3.2) ps-1
A measurement is expected at FERMILAB
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IMPACT OF IMPROVED DETERMINATIONS
BK 0.86 0.06 0.14
? 1.24 0.04 0.06
sin2ß 0.734 0.054
Vub (32.4 2.4 4.6) 10-4
(exclusive only)
TODAY
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TODAY
?ms (20.5 3.2) ps-1
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4 NEW PHYSICS
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THE COMPATIBILITY PLOTS
1) To which extent improved experimental
determinations will be able to detect New
Physics?
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SEARCH FOR NEW PHYSICS
2) Given the present theoretical and
experimental constraints, to which extent the UTA
can still be affected by New Physics
contributions?
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TWO SOLUTIONS
Standard Model solution Cd 1 fd 0
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HOW CAN WE DISCRIMINATE BETWEEN THE TWO SOLUTIONS?
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Coming back to the Standard Model
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CONCLUSIONS

• LATTICE QCD CALCULATIONS HAD A CRUCIAL IMPACT ON
  TESTING AND CONSTRAINING THE FLAVOR SECTOR OF THE
  STANDARD MODEL
• IN THE PRECISION ERA OF FLAVOR PHYSICS, LATTICE
  SYSTEMATIC UNCERTAINTIES MUST (AND CAN) BE
  FURTHER REDUCED
• IMPORTANT, BUT MORE DIFFICULT PROBLEMS (NON
  LEPTONIC DECAYS, RARE DECAYS, ...) ARE ALSO BEING
  ADDRESSED