View
231
Download
0
Category
Preview:
Citation preview
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
Fergus Wilson, RAL. LFV and LU
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)
13th July 2009
Fergus Wilson, RAL. LFV and LU
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.
13th July 2009
Fergus Wilson, RAL. LFV and LU
4
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.
13th July 2009
Fergus Wilson, RAL. LFV and LU
5
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.
13th July 2009
Fergus Wilson, RAL. LFV and LU
6
g-2
13th July 2009
Fergus Wilson, RAL. LFV and LU
7
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
8
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
9
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
10
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
11
μ→eγ and μN→eN
13th July 2009
Fergus Wilson, RAL. LFV and LU
12
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
13
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)
13th July 2009
Fergus Wilson, RAL. LFV and LU
14
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
15
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
16
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
17
Kaon decays
13th July 2009
Fergus Wilson, RAL. LFV and LU
18
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
19
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
20
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%
13th July 2009
Fergus Wilson, RAL. LFV and LU
21
τ decays
13th July 2009
Fergus Wilson, RAL. LFV and LU
22
τ : LFV in τ decays Many different BSM models and predictions to test Predicted rates are several orders of magnitude higher than μ
rates
13th July 2009
Fergus Wilson, RAL. LFV and LU
23
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
24
τ : The experimental landscape
10-10
Belle/BaBar
LHC
SuperB/BelleII
13th July 2009
Fergus Wilson, RAL. LFV and LU
25
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%
13th July 2009
Fergus Wilson, RAL. LFV and LU
26
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
27
Charm
13th July 2009
Fergus Wilson, RAL. LFV and LU
28
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
29
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
30
B and Υ(nS) decays
13th July 2009
Fergus Wilson, RAL. LFV and LU
31
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
32
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
33
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
34
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
35
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)
13th July 2009
Fergus Wilson, RAL. LFV and LU
36
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
13th July 2009
Fergus Wilson, RAL. LFV and LU
37
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.
13th July 2009
Fergus Wilson, RAL. LFV and LU
38
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.
Recommended