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

Lattice weak decays, IIT, Guwahati A. Soni 1

mailto:([email protected])

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


What’s the hooplah• [Ks => + - ]/ [K+ => + 0 ] = 670!

• ’ /


Direct CP violation in K=>ππ decays


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 ’

8Lattice weak decays, IIT, Guwahati A. Soni

Theory: Salient features


Four stages

• ~1982 – 1994 .with Claude Bernard

• ~ 1995-1998 with Tom Blum

• 1998---2008 RBC

• 2008 -> present RBC-UKQCD



Shamir & Furman, NPB 439, 54,1995


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



RBC-UKQCD, arXiv:1111.1699, PRL 2012

Lattice weak decays, IIT, Guwahati A. Soni 22T Izubuchi

RBC-UKQCD


Donoghue,,G,H“Dynamics of The SM” ‘92

Dissecting 3/2 Amp on the lattice


Simplest basic step isSignificantly different

from phenomenological

expectations


Brute force32X32X32X

64X16

QCDOC 10 Tf


Mass depends of ReA2, A0

Due to the cancellation, 3/2 amplitude decreases significantly as the

pion mass is lowered towards its physical value

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



Stolen from Christoph Lehner

Delta F=2 mixings are extremely valuable treasures in providing stringent constraints on BSM


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)



Outstanding Th.puzzles of our times


Relevance of the lattice


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


Multitude of cutting edge calculations


RBC-UKQCD: BK with physical masses


The weakest link now


The sign of the non-leading term



Cheng & Li, Gauge Field Theory

DGH


Weak Interactions & Modern Particle

TheoryHoward Georgi

BK & the KM nobel prize



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.


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


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]


RBC/UKQCD (ongoing)attempts at taming ΔmK


Jiang-lei Yu PhD thesis Columbia Univ (2013)

• Adds one more observable to the very short list that can be used for UT analysis and constraints on BSM


In progress RBC/UKQCD:


D-,Bmixings [Chris Bouchard @ Lat14]


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)


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.


recent lattice advances in weak decays · with c. bernard [ucla] ... • aida el-khadra: lattice...

Documents