Recent lattice advances in weak decays · With C. Bernard [UCLA] ... • Aida El-Khadra: Lattice...
Transcript of Recent lattice advances in weak decays · With C. Bernard [UCLA] ... • Aida El-Khadra: Lattice...
Recent lattice advances in weak decays Amarjit Soni, HET-BNL
([email protected])XXI DAE-BRNS High Energy Physics Symposium 2014
IIT, Mumbai; 12/10/14
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Outline• Introduction & Motivation• Classic challenges: • K=> pi pi, Delta I=1/2 Rule and epsilon’/epsilon• ΔmK
• Precision Frontier (some examples)• BK ; Kl3; ReA2; ImA2; ε’/ε[EWP]Heavy-light:• Decay constants• Mixing Parameters• ξ SU(3) breaking ratio• Semi-leptonic form factors• Summary & outlook
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What’s the hooplah• [Ks => + - ]/ [K+ => + 0 ] = 670!
• ’ /
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Direct CP violation in K=>ππ decays
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Sad story of ’/
• ~15% measurement obtained with heroic efforts (spanning over 20 years!) on both sides of the Atlantic at a cost very iikely well over $200M:
• Its WORTHLESS FOR NOW! It has 0 impact on theory• ONLY LATTICE METHODS CAN CHANGE THIS FACT
• My entry into lattice methods ~1982 was motivated by wanting to reliably calculate ’
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Theory: Salient features
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Four stages
• ~1982 – 1994 .with Claude Bernard
• ~ 1995-1998 with Tom Blum
• 1998---2008 RBC
• 2008 -> present RBC-UKQCD
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Shamir & Furman, NPB 439, 54,1995
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N. Christ @LAT08
Direct K-> (a la Lellouch-Luscher), using finite volume correlation* functions, [i.e. w/o
ChPT] RBC initiates around 2006
* Allows to bypass Maini-Testa theorem
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RBC-UKQCD, arXiv:1111.1699, PRL 2012
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RBC-UKQCD
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Donoghue,,G,H“Dynamics of The SM” ‘92
Dissecting 3/2 Amp on the lattice
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Simplest basic step isSignificantly different
from phenomenological
expectations
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Brute force32X32X32X
64X16
QCDOC 10 Tf
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Mass depends of ReA2, A0
Due to the cancellation, 3/2 amplitude decreases significantly as the
pion mass is lowered towards its physical value
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TXT cancellation with T• At physical kinematics we find
T ~ - 0.7 T X T in contrast to expectation from common folklore (large N): T ~ T X T/N ~ 0.3• i.e. the very 1st step in large N and in vacuum saturation
(factorization) is not adhered in QCD• Using in addition (at scale of ~1.7 GeV), z1 = -0.30, z2=
1.14 one finds• Re A0 / Re A2 ~ 10.9 ; thus about 50% of the
observed enhancement originates from simple tree operators
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Stolen from Christoph Lehner
Delta F=2 mixings are extremely valuable treasures in providing stringent constraints on BSM
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2nd order Weak in SM=> tiny effects resulting from QM mixings
Some examples
• Ball-park value of charm mass from ΔmK, Mohapatra, Rao & Marshak, PR 171, 1502, 1968
Gaillard & Lee, PRD 10, 897, 1974
• “Large” Bd mixing (Argus’87) => early indicator of large mt (requires fB)
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Outstanding Th.puzzles of our times
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Relevance of the lattice
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With C. Bernard[UCLA]
Lattice 2014@ Columbia University, june 23-28
• Lot of input used from review talks by:• Nicolas Garron: Weak interactions of kaons and pions• Chris Sachrajda: Long distance contributions to flavor changing
processes• Chris Bouchard: Testing the SM under the weight of heavy flavors• Aida El-Khadra: Lattice QCD and flavor physics, a new landscape
@ CKM 2014, Sept 2014, Vienna
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Multitude of cutting edge calculations
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RBC-UKQCD: BK with physical masses
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The weakest link now
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The sign of the non-leading term
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Cheng & Li, Gauge Field Theory
DGH
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Weak Interactions & Modern Particle
TheoryHoward Georgi
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BK & the KM nobel prize
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Critical Role of the B factories in the verification of the KM hypothesis was recognized and cited by the Nobel Foundation
A single irreducible phase in the weak interaction matrix accounts for most of the CPV observed in kaons and B’s.
CP violating effects in the B sector are O(1) rather than O(10-3) as in the kaon system.
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Lattice:BK ~.756(.015)
Inputs:εK ; B->l ν X;ΔmsΔmd
Long-distance (non-local) contribution to ΔmK
RBC/UKQCD has developed method in the past several years to attack such LD effects that typically
arise in 1-loop weak processes
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Perturbation Theory attempts
• S. Herrlich & U Nierste, NPB 419, 292, 1994
• J. Brod & M. Gorbahn, PRL 108, 121801, 2012
• NNLO ~ 0.36 LO• [charm mass is not that heavy for me to feel comfortable with PT; In
own pheno work tend to assign 50% error]
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RBC/UKQCD (ongoing)attempts at taming ΔmK
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Jiang-lei Yu PhD thesis Columbia Univ (2013)
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• Adds one more observable to the very short list that can be used for UT analysis and constraints on BSM
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In progress RBC/UKQCD:
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D-,Bmixings [Chris Bouchard @ Lat14]
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Vub: semi-leptonic form factor• Many ongoing independent efforts on the lattice• RBC-UKQCD is unique as it is using DWQ for light quarks and relativistic
Heavy quarks….study lead in past 2 years or so by Taichi Kawanai (BNL)
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Summary & outlook• In past ~5 years, as mentioned before, due to better methods (algorithms, theoretical understandings/formalism ) and of course
due to significant increases in computing resources, major progress was made for a host of important physical observables for weak decays• From lattice in (~5 years) anticipate[ norm .. results with physical meson masses!] :BK sub-percent accuracy…….[is this improved accuracy really useful?]• ΔmK ~ O(10%)….New observable for UT & search for NP.• BB ~ 4% ; BBs ~ 3% ; ξ < ~ 2%; Vub ~O(5%)• And last but potentially most important, ε’/ε with ~20% error• From Expt: LHCb Run 2; Belle 2 (X40 lumi over Belle)• Expect SM-CKM UT tests with improve accuracy from current 15-20% to around
5%; and numerous other powerful tests.
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