13th July 2009Fergus Wilson, RAL. LFV and LU1 Lepton Universality and Lepton Flavour Violation...

13th July 2009

Fergus Wilson, RAL. LFV and LU

1

Lepton Universality and Lepton Flavour Violation

Fergus WilsonRAL/STFCUK Strategy on Flavour Changing Physics and QCD

13th July 2009


2

Outline Motherhood and Apple Pie. Experimental Measurements by decay

muon anomalous magnetic moment, aμ μ→eγ and μN→eN conversion Kaon decays τ decays Charm decays Υ(nS) and B decays

Not discussed in any depth Vus, Form Factors, αs(Mτ) Experimental details (see following talks)

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3

Declaration of Interest I am a member of BaBar (R.I.P.) and

LHCb. I’ve signed SOIs for SuperB and LHCb

upgrade. I’ve participated in discussions on UK

NA62 involvement.

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The importance of Charged LFV Charge Lepton Flavour Violation (CLFV) is not a

fundamental symmetry of the Standard Model (SM). Even with neutrino oscillations, SM LFV BF is ~ (Mυ/ MW)4

~ 10-54. Compare with Quark Flavour Violation (QFV) which scales with log(mq).

Nearly all BSM theories have a LFV component. Even Minimal Quark Flavour Violating models (QFV

comes from the SM sector only) have a LFV component. Experiments are already eliminating models and/or

parameter space e.g. in τ+→l+l-l+ MFV BF predictions <10-

8, experimental upper limits <10-8. CLFV decays are much cleaner theoretically and

experimentally than QFV: Lepton decays (very few hadrons to worry about). Final state is often all charge tracks. Minimal non-perturbative QCD calculations needed.

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The importance of Charged LFV Very high precision in some theory and experiment e.g.

muon g-2 at 0.5ppm. A driver to improve theoretical calculations and Lattice

QCD. A driver of experimental and accelerator techniques.

Essential to understand the flavour properties of the Higgs and SUSY. A vital cross-check and complementary measurement to the LHC.

If the Higgs/SUSY not found (or find hierarchy of new particles beyond 1TeV) then need to look at loop processes to probe higher mass scales (1-100 TeV).

LFV is can also effected by GUT-scale processes e.g. heavy υ in SeeSaw models.

All BSM models have a different hierarchy of predictions for various LFV decays. It is therefore vital to make as wide a range of LFV measurements as possible.

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g-2

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g-2: Anomalous μ Magnetic Moment aμ Muon al ≠ 0 due to radiative corrections; could come from BSM

particles. Muon anomaly ~750 x e anomaly but more susceptible to heavy

virtual particles ~ (ml/M)2. Connection to LFV in SUSY slepton mixing

→ e MDM, EDM~ ~

2 2 2

2 2 2

2 2 2

ee e e

e

e

m m m

m m m

m m m

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g-2: BSM models and LHC

Nowe.g. LHC finds SPS 1a

Snowmass Points

Present Precision

Future Precision

Can already discriminate between various models and parameter space.

Can be combined with LHC measurements to constrain parameter space

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g-2: Predictions and Results

1

,

,

1

, ,

(116584718.09 0.14) 1

6901 42 1

0

97.9 0.9 0.

9

154 2 1

7

3

SM had LO hl

QED

wad HOl l

had HO

weak

QE eakl

Dl

had LO

a a

a

a

a

a

aa a

2

2

,24

( ) ( )

3

( )( )

( )

had LO

m

m R s K sa ds

e e hadronsR

e

s

se

exp

exp + -

+ -

[ ] 11659192.6 4.1 2.6 0.2

11659177.3 4.3 2.6 0.2[ ]

11659178.3 5.0 2.6 0.2

11659208.0 6.3

15.4 8.0( )

30.7 8.1 (e e with KLOE)

29.7 8.5 (e e w/o KLOE)

SM

SM

SM

a

a e e

a

a a

1.7-3.0σ deviation: Δa could be explained by SUSY

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g-2: The Future Currently

Experimental accuracy 0.46 (stat)+/- 0.28 (syst)= 0.54 ppm (4.4x10 -10) Theory accuracy ~0.6 ppm (~6x10-10) Lattice accuracy ~1.5 ppm: aμ (had,LO) = (715±15)x 10-10 (from 2007, MILC)

Near Future 2012: ISR analyses from BaBar/Belle (see EPS09 possibly) Resonance scans BaBar/Belle KLOE-2 VEPP-2000: up to sqrt(s) = 2 GeV BES III tau-charm factory Total error by 2012: Reduce error by factor 2 to 3.0x10-10?

Further Future: SuperB/BelleII

ISR and resonance scans. E821->E989

Double statistics but then need more muons to be feasible. JPARC/E989/Project X

Aim for 0.1(stat) +/-0.07 (syst) ppm Reduce total error by another factor 2 -> 1.5 x 10-10

Need more muons -> MICE Possiibility to measure muon EDM. Sensiitivity 10-19 e cm → 10-22-10-24 e cm

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μ→eγ and μN→eN

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μ→eγ and μN→eN conversion CLFV very rare in SM ~ 10-54

SUSY-GUT models etc… can enhance this in μ→e to 10-15 – 10-11

Experimental Advantages High Muon Flux Leptonic Decay process

3 2

2 4( ) eGUT

F

B eG m

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μN→eN: Sensitive to many sources of New Physics Compositeness

Second Higgs doublet

Heavy Z’ Anomalous Z

coupling

Predictions at 10-13

Supersymmetry

Heavy Neutrinos

Leptoquarks

132* 108 eNNUU

2TeV/c3000 eddLM 17

2'

10)(@

/TeV3000M

eZB

cZ

H4

H 10 gg e

TeV3000c

( a la Marciano)

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μ→e : already challenging BSMR

andall-

Sundru

m

Litt

lest

Hig

gs

w T

-pari

ty

MSSM

w m

SU

GR

A b

c

CM

SSM

-seesa

w

MEGA

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μ→e : Future precision

Rates indicate type of interaction e.g. new particle in a loop versus a four-fermion point interaction.

Sensitive to scales above LHC

SUSY GUT

SUSY GUT COMET

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μ→e: The Future

MEG starting to take data. Mu2e approved (but long-term funding uncertain?). UK interest:

COMET has CDR before JPARC PAC (June 09). PRISM after COMET but has UK accelerator interest

(muon, FFAG etc…)

13

11

13

16

7.0 10 2001

1.2 10 1

10 2009 2011

10 2016 ? Propo

99

se

9

d

2

SINDRUMII PSI Au e Au Finished

MEGA LAMPF e Finish

MEG PSI e Starting

COMET JPARC

Experiment Whe

Al e Al

Mu

re Mode Limit Date

e FermiL

ed

St

a

atus

b

16

18

10 2018 ? Approved

10 2018 ? Proposed

Al e Al

PRISM JPARC Ti e Ti

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Kaon decays

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Kaon decays and ratios SM predictions (plus theoretical input

and corrections) exist for: BF(M-→l-υ) BF(K→lπυ(γ)) BF(K-,π-→l-υ(γ))

Charged Higgs will change the BF. LFV of a few % possible with

reasonable parameters. Measure BF and ratios (ratios eliminate

many theoretical uncertainties);

1. R = Kμ2(γ) / πμ2(γ) → Vus / Vud

2. RK = Ke2(γ) / Kμ2(γ) → LU Δr = RK (exp) – RK (SM) → New Physics?

3. rμe = Kμ3 / Ke3 → LU

4. Rl23 = Kμ2 / Kμ3 → LU

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K: Status

5(2.493 0.032) 10KLOEKR

/0.063 0.017 (NA48/2)eNPr

Black points could explain g-2 discrepancy

KLOE

23 1.008 0.008KLOElR

5

62 5

5

(2.477 0.001) 10

(2.500 0.016) 10

(2.493 0.032) 10

SMK

NAK

KLOEK

R

R

R

2 2 41-V (4 7) 10ud usV

2

1

1.008 0.005

SMe

ee

r

Gr

G

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Kaon: The Future KLOE 2 Step 0 (5-10 fb-1)

Run with increased lumi from now. Vus error: 0.3% (now) → 0.17% 1-|Vus|2-Vud|2 error: 7x10-4 (now) → 3-4x10-4

RK error: 1.3% (now) → 0.6% (in 5 fb-1)?

NA62-I Data already in hand RK error: 0.7% (now) → 0.4% (full dataset)

NA62-II Construction 2009-2012 Run 2012-2015 RK error: 0.4% (NA62-I) → 0.2%

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τ decays

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τ : LFV in τ decays Many different BSM models and predictions to test Predicted rates are several orders of magnitude higher than μ

rates

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τ : Why look at τ LFV as well as μ? Rates are higher than μ

Many BSM predictions already at experimental precision e.g. 31 decays measured at B Factories at ~ 10-8 level

The τ and μ LFV predictions are often coupled

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τ : The experimental landscape

10-10

Belle/BaBar

LHC

SuperB/BelleII

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τ : Lepton Universality and Charged Higgs

2

52

(1 )( )

( ) (1 )

(1 )( )

(1 )

rade e

rad

rad

erade

g CB e

g B C

Cg mB

g C m

2

3

( )

( )

tan 2001 10

50

e

H

re

GeV

M

Compare to LU from Kaon decays, page 19

About factor 2 more accurate than Kaon modes.

Tests LU at 0.2%

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τ : The Future Next 1-2 years

BaBar, Belle (~1.5x109 tau pairs). LHCb:

τ→μμμ < 1.2x10-7 in 2 fb-1

Next ~5 years ATLAS/CMS

τ→μμμ (W-source) < 3.8x10-8 in 30 fb-1

τ→μμμ (W+Z-source) < 1-2x10-8 in 300 fb-1

LHCb τ→μμμ < 2.0x10-8 in 10 fb-1

Next 10 years SuperB/BelleII (~7.5x1010 tau pairs, 50-75 ab-1)

τ→μμμ < 1x10-9 -1x10-10

τ→lγ < 1x10-8 -1x10-9

τ→lυυ LU at 0.02% (statistical). LHC upgrade

LHCb: τ→μμμ <1x10-8 in 100 fb-1

ATLAS: Improved trigger + detector should extend τ→μμμ but work not yet complete

Next 20 years GLC and GigaZ

ab-1

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Charm

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D+(s)→l+υ and Charged Higgs

3

2

4

6

3

,

4( ) (3.93 0.35 0.10) 10

( )

( ) (6.57 0.90 0.34) 10

( ) (6.29 0.78

CLEO re

0.52) 10

11.74 1.7 0.2

( ) 1.2 1

8.8 10

( ) 2.1 10

sults

:

0

:

(

S

S

S

S

S

D

Bell

BF D

BF D e

B

BF D

BF

e

F

BF D

BF

D

D

R

D e

3) (6.44 0.76 0.57) 10

9

7

SM Predictions

( ) 9.2 10

( ) 1.3 10

2.65

9.76S

S

D

D

BF D e

BF D e

R

R

( ) ( )

( )

222

22 2( ) ( , )2

( ) 18 s s

s

lFs l c d sD D

D

mGD l f m M V

m

( )

( )

( )

22 2 2

( )/2

2 2 2( )

1( )

( ) 1

s

s

s

DsD

sD

m m mDR

D m m m

Charged Boson can contribute

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Charm: The Future Lattice QCD

Already have high precision D and Ds decay constants (error lower than experiment).

BES-III D→lυ Goal 12x (4x) Cleo-c D (Ds) dataset Factor 2-3 improvement in statistical error Statistical error should then equal current Cleo-c

systematic error. BES-III D→h l+l-’ (e.g. D→K- μ+e- )

UL on LFV decays improve by 100-1000 over CLEO/FOCUS/D0 etc… with 20 fb-1

Super B factories D→lυ Factor 10 improvement in statistical error But needs to work on systematics

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B and Υ(nS) decays

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B0→l+l-, B0→l+τ- , B+→l+υ

0 8

0 8

0 8

6

0 5

0 5

6

Channel BF (UL 90%)

5.2 10

11.3 10

9.2 10

1.9 10

2.

1.0 10

8 10

2.2 10

B

B e e

B e

B e

B e

B

B

Non-SM Higgs?

2 2 22

11

7

4

2

2

2

2

SM Prediction:

BF( ) ~ (1.2 0.3) 10

BF( ) ~ (5.2

Standard

Charged

M

1.3) 10

BF( ) ~ (1.59 0.4

Higgs E

odel:

( ) 1

ffect:

, 1 tan

0) 10

8F B l l

B B u

e

BSM H H

H

e

bB

mBF BF r r

m

G m m mF

B e

B

B

B l f Vm

2

2

Error on BF prediction from Vub (~10%) and fB (~10%)

B+→μ+υ experimental Upper Limit approaching SM prediction

B+→μ+υ with B+→τ+υ leads to LU test

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B-→τ-υtanbm

b

q H/W

tanm

HFAG Average BF(B→τυ) = (1.73±0.35) x 10-4

BF on edge of current experimental reach

Need to reduce error

Constraints combined with g-2

95% exclusion region assuming

B→τυ=(1.59±0.4)x10-4

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Lepton Universality and LFV in Υ(nS) decays

BF(Y(ns)→l+l-) should be independent of flavour l.

Υ(nS) and τ LFV decays are related:

Sensitive to a low mass CP-odd Higgs, A0.

LU Cleo results for R(ττ/μμ):

LFV B Factory UL on R(τμ/μμ):

( / )

(1 ) 1.02 0.02 0.05

(2 ) 1.04 0.04 0.05

(3 ) 1.07 0.08 0.05

Mode R

S

S

S

* *e e

2 4( )

( )N MB

B

( ) / ( )

(1 ) 0.023%

(2 ) 0.17% 1.5 TeV

(3 ) 0.13%

Mode B B

S

S

S

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B→Dτυ Also sensitive to charged Higgs Different theory systematics (no Vub and fB but does

have B→D form factors). q2 and τ polarisation also affected by different BSM. Universality between b → cH, b → uH, b→ tH (LHC).

Deviation from SM: 0.5σ (B0) and 1.6 σ (B+)

0 0.41 0.240.39 0.19

0 0.46 0.130.41 0.11

*0 0.69 0.400.66 0.47

0 * 0.75 0.310.66 0.22

( ) (1.51 0.15)%

( ) (1.01 0.10)%

( ) (3.04 0.22)%

( ) (2.56 0.10)%

BF B D

BF B D

BF B D

BF B D

cb

H/W

tanbm

tanm

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50ab-1

B decays: The Future Need improvement on Vub and

fB. LHCb

BF(Bs→e+μ-) < 6.5x10-8 in 2 fb-1; <0.4x10-8 in 100 fb-1

BF(B→τX) < 10-8 in 10 fb-1

B factories are a natural place to do this BF(B→τυ) ±2% BF(B→τX) < 10-8-9

BF(B→μυ) 5σ discovery with 5 fb-1

BF(Ds→τυ) ±1.5% (charm factory better for D→lυ).

BF(B→Dτυ) ±2.5%

Effect of H+ :

B→lυ O(10-30)%

B→Dτυ O(3-10)%

K→lυ O(0.1-0.3)%

(see Isidori talk)

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Lattice QCD : possible 5 – year plan Lattice QCD (Form Factors, VCKM, masses) is an

important input to some LFV measurements. Alternatively, assuming LF conservation,

improved experimental precision will drive LQCD.

( ) ( )

Process , ,

Lattice Parameter (0) /

Current Lattice Error 0.5% 0.6% 2% 6%

Current Exptl. Error 0.2% 0.2% 4% 30%

Future Lattice Error 0.2% 0.3% 0.5% 2%

s s

s s

K D B

K lK l D D l B B l

lf f f f f

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Concluding Remarks There is no one “LFV experiment”. Highly interconnected set of measurements. Many measurements are still statistics

dominated but will become theory-dominated with next generation experiments.

Many SUSY models are already being challenged by LFV and LU measurements.

We can expect many measurement errors to improve as luminosity-1.

Flavour is essential to the understanding of the Higgs (SM and BSM) and SUSY.

It is important to measure LFV in tau and muon decays as different models predict different relative levels of tau and muon LFV.

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Concluding Remarks g-2 is still a benchmark measurement. Hadronic

uncertainties can be understood from tau, charm, beauty and hadron experiments.

BSM models can be confirmed/excluded by measuring a set of golden-mode flavour decays.

The UK has built up a huge expertise in flavour physics over the last decade (both experimental and theoretical).

Flavour has a successful track record on flavour (on-time, on-budget).

A large fraction (30%?) of our community is interested in flavour physics.

Flavour is essential for the breadth of the field in the UK.

Without flavour physics, LHC discoveries will not be complete.

13th July 2009Fergus Wilson, RAL. LFV and LU1 Lepton Universality and Lepton Flavour Violation...

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