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Celebration of Panofsky Prize
Jonathan Dorfan David Hitlin Fumihiko Takasaki Stephen Olsen
“For leadership in the BaBar and Belle Experiments, which established theviolation of CP symmetry in B-meson decay, and furthered our understanding of
quark mixing and quantum chromodynamics.”
B-factory Science ImpactZoltan Ligeti
Celebration of Dorfan/Hitlin Panofsky Prize
SLAC, January 13, 2016
Personal recollections
• I met Dave when as a postdoc at Caltech (1994–97); was fun to think independentof the available data (then mostly CLEO), imagining the huge future data sets
Some were done by BABAR & Belle: B → Xsγ spectrum and moments, B →Xc`ν moments and |Vcb|, B → Xu`ν hadron mass spectrum, B → D∗∗`ν (LLSW)
Some are still left for the future: B → Xsνν, B → Xcτ ν, etc.
• Discussions with Dave — remember vividly being stunned by deep commentsat a level as if he has been working on the same problem, immediate picture ofdecay properties that he heard about for the first time
• The BABAR workshops took place in my 3rd year at CaltechI went to Rome, Princeton, Paris...
Z L – p. 1
Personal recollections
• I met Dave when as a postdoc at Caltech (1994–97); was fun to think independentof the available data (then mostly CLEO), imagining the huge future data sets
Some were done by BABAR & Belle: B → Xsγ spectrum and moments, B →Xc`ν moments and |Vcb|, B → Xu`ν hadron mass spectrum, B → D∗∗`ν (LLSW)
Some are still left for the future: B → Xsνν, B → Xcτ ν, etc.
• Discussions with Dave — remember vividly being stunned by deep commentsat a level as if he has been working on the same problem, immediate picture ofdecay properties that he heard about for the first time
• The BABAR workshops took place in my 3rd year at CaltechI went to Rome, Princeton, Paris...
• Once, on a weekend, jump-starting Dave’s porschefrom my crappy nissan sentra
Z L – p. 1
Personal recollections
• I met Dave when as a postdoc at Caltech (1994–97); was fun to think independentof the available data (then mostly CLEO), imagining the huge future data sets
Some were done by BABAR & Belle: B → Xsγ spectrum and moments, B →Xc`ν moments and |Vcb|, B → Xu`ν hadron mass spectrum, B → D∗∗`ν (LLSW)
Some are still left for the future: B → Xsνν, B → Xcτ ν, etc.
• Discussions with Dave — remember vividly being stunned by deep commentsat a level as if he has been working on the same problem, immediate picture ofdecay properties that he heard about for the first time
• The BABAR workshops took place in my 3rd year at CaltechI went to Rome, Princeton, Paris...
• Once, on a weekend, jump-starting Dave’s porschefrom my crappy nissan sentra
Z L – p. 1
Summary — version one
• Flavor physics was crucial for the development of the standard model(KL → µµ⇒ GIM, charm; εK ⇒ 3rd generation; ∆mK ⇒mc; ∆mB ⇒heavy mt)
• LEP & SLC in the 90s probed the gauge sectorto better than 1%, testing the theory at one-loop level
Nobel Prize, 1999⇒
• Before 1999, ε was the only unambiguous measurement of CP violationCould be fit with KM phase, but O(1) deviations in SM flavor sector were allowed
• BABAR and Belle probed the Yukawa sector much better
Nobel Prize, 2008⇒
• However, O(20%) BSM contributions to FCNC processesstill allowed — lot of room for Belle II & LHCb to find NP
Z L – p. 2
Large impacts on theory
• Flavor physics triggered lots of developments + testing grounds for new methods
CPV motivated: CP invariance of QCD, isospin & SU(3) flavor, Dalitz analyses
FCNC motivated: Heff at high orders, multi-loop perturbative calculations
Heavy quark symmetry: symmetries, HQET at high orders, many applications
Operator product expansions: Develop / use / test expansions to high orders
Soft-collinear effective theory: Started with B → Xsγ and semileptonic
[Developments continue, expect a lot more, data always motivate theory]
BSM: Hundreds of papers motivated by anomalies, elaboration of MFV, GMSB,other frameworks to address lack of NP signals in flavor [all started pre-BABAR]
• Broad impacts: perturbative / nonperturbative / logs vs fixed order / interfacesBroad impacts: (LHC jet vetos, cross sections, jet substructure, EFT for DM signals, ... )
Z L – p. 3
Rough outline
• B physics before BABAR + progress since
• New measurements at BABAR not done / seen beforeNew measurements at BABAR some impacts constraining BSM
• Future: Belle II, LHCb, current anomalies, prospects
Z L – p. 4
Rough outline
• B physics before BABAR + progress since
• New measurements at BABAR not done / seen beforeNew measurements at BABAR some impacts constraining BSM
• Future: Belle II, LHCb, current anomalies, prospects
Disclaimers
I’ll mostly say BABAR throughout this talk — comparable results from Belle
Focus on topics relevant to understand short-distance physics
Thousands of missing references...
Z L – p. 4
Started before BABAR
Discovery of B0–B0 mixing, 1987
• ARGUS: At much higher rate than expected
• Preceded by: discovery of Υ
Preceded by: long B lifetime
• Flurry of theory papers, SM interpretation:
– Probably mt > mW ⇒ no top hadrons– Expect Bs mixing near maximal
• SM predicts large CP violationSM predicts large FCNC B decay rates
Z L – p. 5
Resolving Bs oscillations: CDF, 2006
• Current world averages:
∆md = (0.5055± 0.0020) ps−1 0.4% precision
∆ms = (17.757± 0.021) ps−1 0.1% precision
(Both dominated by LHCb now)
• ∆ms more precise, frequency measurement...
decay time [ps]0 1 2 3 4
can
did
ates
/ (
0.1
ps)
0
200
400
Tagged mixed
Tagged unmixed
Fit mixed
Fit unmixed
LHCb
Z L – p. 6
B lifetime, Vcb — the beginning
• 1983: Long B meson lifetime⇒ |Vcb| is small
(Panofsky prize 2006)
• ARGUS: oscillation & decay timescale comparable: ∆m/Γ ' 0.77 (and ∆Γ� Γ)
• Crucial to allow experimental study of CP violation in B system
• If |Vcb| were as large as |Vus|, probably BABAR & Belle would not have been built
No precision CKM tests? no KM Nobel Prize?
Z L – p. 7
Vub — the beginning
ARGUS, PLB 234 (1990) 409, Received 28 Nov 1989 (201+69 pb−1)
“If interpreted as a signal of b → u cou-pling . . . |Vub/Vcb| of about 10%.”
CLEO, PRL 64 (1990) 16, Received 8 Nov 1989 (212+101 pb−1)
“|Vub/Vcb| . . . is approximately 0.1; itis sensitive to the theoretical model.”
Z L – p. 8
Vcb and Vub since...
• PDG 1988: |Vcb| = 0.046± 0.010, |Vub/Vcb| < 0.2
• Huge experimental and theoretical efforts since late 1980s
• |Vub|: If it were 0, no CP violation in CKM matrix
|Vub|: Dominant uncertainty of the side of the UT opposite to β
|Vub|: Crucial for NP sensitivity (compare “tree” and “loop” constraints)
• |Vcb|: Large part of the uncertainty in the εK constraint
|Vcb|: Large part of the uncertainty in B(K → πνν)
• Same theoretical tools as for inclusive and exclusive rare b → sγ, b → s `+`−,b→ sνν decays, which are sensitive probes of NP
Z L – p. 9
|Vcb| alone excluded GUT models / textures
B → K∗γ and B → Xsγ before BABAR
• CLEO discovered radiative B decays — only bounds on B → K∗`+`− & Xs`+`−
• Series of elaborate calculations of FCNC B decays started about ’87
• Surprisinglyprecise!
Z L – p. 10
B → Xsγ now
• One (if not “the”) most elaborate SM calculationsConstrains many models: 2HDM, SUSY, LRSM, etc.
• NNLO practically completed [Misiak et al., 1503.01789]
4-loop running, 3-loop matching and matrix elements
Scale dependencies significantly reduced ⇒
• B(B → Xsγ)∣∣Eγ>1.6GeV
= (3.36± 0.23)× 10−4
Measurement: (3.43± 0.22)× 10−4
O(104) diagrams, e.g.:
b s
c
c
γ
�
Z L – p. 10
PEP-II and BABAR
Asymmetry is a key to time-dependent measurements
(P. Oddone, Panofsky prize 2005)
The Machine
(APIARY is no more contrived than BaBar for B and B-bar Experiement)
The Physics
[No...][No...]
The BABAR Physics Book
• No executive summary, neither a list of killer apps or gold-plated measurements...
• Serves now as a model for the Belle II Theory Interface Platform
Z L – p. 13
Cites > 500
↑ Unexpected
↓ Expected
CP violation — views around 1999
• Until 1999, ε was the only measured CPV, ε′/ε unambiguously measured in ’99
The SM with 3-generationscould accommodate ε, but ...
[Y. Nir]
• Are there detectable new particles / interactions, which couple to flavor?
Z L – p. 15
Questions around 1999
• Is the SM the only source of CPV? Does the SM fully explain flavor physics?
– CPV in ∆F = 2 only (superweak)? Also in ∆F = 1?
– Are all CPV effects small? Or only small in kaons due to small mixing angles?
– One or more CPV parameters?
– CPV relates to charged currents only? Also in neutral currents?
– Does CPV treat 3rd generation special? Up / down sectors?
– CPV in flavor changing interactions only? EDM searches?
– CPV only in quark sector? Also in lepton sector?
– Find new sources of CPV that could help with baryogenesis?
• It was not known if the SM picture of CPV was even approximately correct
Z L – p. 16
Views of FCNCs around 1999
• Many models with SM-like 1st and 2nd generations, while 3rd is different
• The very high scale sensi-tivity of neutral meson mixingwas known since the 70s
[M. Wise]
While publicity of BABAR relied on CPV, to test the SM, no deep distinction (argM12 or |M12|...)
Z L – p. 17
BABAR novelties
Quantum entanglement in Υ(4S)→ B0B0
• B0B0 pair created in a p-wave (L = 1) evolve coherently and undergo oscillations
Two identical bosons cannot be in an antisymmetric state — if one B decays asa B0 (B0), then at the same time the other B must be B0 (B0)
• EPR effect used for precision physics:
Measure B decays and ∆z
• First decay ends quantum correlation and tags the flavor of the other B at t = t1
Z L – p. 18
One of the cleanest cases: CPV in B → ψKS
• CP violation can be an O(1) effect: sin 2β = 0.691± 0.017
afCP =Γ[B
0(t)→ ψK]− Γ[B
0(t)→ ψK]
Γ[B0(t)→ ψK] + Γ[B
0(t)→ ψK]
= sin 2β sin(∆mt)
0B
0B
CPf
q/p
A
A
b
d
d
b
t
t
W W
b
d
d
b
W
W
t t
• CP violation is large in some B decays — it is small in K decays due to smallCKM elements, not because CP violation is generically small
Z L – p. 19
sin 2β in “penguin modes”
• Huge stakes: robust deviation from expectations would indicate new physics
• Proliferation ofblind analyses...
[ c© Hitlin @ ICHEP 2000]
MeasuringCP violation is no longer auto-
matically interesting — If Sη′K were near
0, we’d have a many σ discovery of NP!
• Some of these measurements willget near current sin 2β levels
sin(2βeff
) ≡ sin(2φe1ff) vs C
CP ≡ -A
CP
Contours give -2∆(ln L) = ∆χ2 = 1, corresponding to 60.7% CL for 2 dof
-0 0.2 0.4 0.6 0.8 1
-0.4
-0.2
0
0.2
0.4
sin(2βeff
) ≡ sin(2φe1ff)
CCP ≡ -ACP
b→ccs
φ K0
η′ K0
KS K
S K
S
π0 K
S
ρ0 K
S
ω KS
f0 K
0
K+ K
- K
0
H F A GH F A GMoriond 2014
PRELIMINARY
Z L – p. 20
Beyond expectations: α and γ
• ’97 CLEO: B(B → Kπ) > B(B → ππ)⇒ |P/T | >∼ 0.3
Isospin analysis to isolate CPV in ππI=2 state (tree)
• Sometimes lucky with hadronic physics:B(B→ρ0ρ0)B(B→ρ+ρ0)
≈ 0.03 vs. B(B→π0π0)B(B→π+π0)
≈ 0.23
Largest BABAR / Belle difference? (deg)α
0 20 40 60 80 100 120 140 160 180
pv
alu
e
0.0
0.2
0.4
0.6
0.8
1.0
EPS 15
CKMf i t t e r
(WA)ρρ→B
(WA)ππ→B
(WA)πρ→B
Combined
CKM fit
• γ: interfere b→ cus (B− → D0K−) withγ: interfere b→ ucs (B− → D0K−)
Problem: small ratio, rB = |A(B−→D0K−)||A(B−→D0K−)| ≈ 0.1
• Most precise: D0, D0 → KS π+π−
Both amplitudes CA; integrate over Dalitz plotγ
0 20 40 60 80 100 120 140 160 180
pv
alu
e
0.0
0.2
0.4
0.6
0.8
1.0
CKM 14
CKMf i t t e r
GLW+ADS
GGSZ
Combined
• Tree-level phase information — became interesting ’03–04 [Richman, Physics Coordinator]
Z L – p. 21
Direct CPV is also O(1)
• Have we seen new physics in CPV?
AK+π− = −0.082± 0.006 (P + T )
AK+π0 = 0.040±0.021 (P+T+C+A+Pew)
• Large difference — small SM sources?
AK+π0 −AK+π− = 0.122± 0.022
(T ) (P )
(C) (Pew)
(Annihilation not shown) [Belle, Nature 452, 332 (2008)]
SCET / factorization predicts: arg (C/T ) = O(ΛQCD/mb) and A+ Pew small
• Large fluctuations? Breakdown of 1/m exp.? Missing something subtle? BSM?
• Can we understand theory well enough, to possibly disprove SM?
• Even larger ACP (Bs → π+K−) = 0.27± 0.04 understood in terms of SU(3)[Grossman, ZL, Robinson, 1308.4143]
Z L – p. 22
D0 –D0 mixing only established in 2007
• Complementary to K, B, Bs
Mixing generated by down quarksor in SUSY by up-type squarks
• Value of ∆m? Not even 2σ now!
Bounds on |q/p| − 1 fairly weakx (%)
−0.6 −0.4 −0.2 0 0.2 0.4 0.6 0.8 1 1.2
y (
%)
−0.6
−0.4
−0.2
0
0.2
0.4
0.6
0.8
1
1.2CPV allowed
σ 1
σ 2
σ 3
σ 4
σ 5
HFAG-charm
CHARM 2015
|q/p|
0.6 0.8 1 1.2 1.4 1.6
Arg
(q/p
) [d
eg
.]
−60
−40
−20
0
20
40
60
σ 1
σ 2
σ 3
σ 4
σ 5
HFAG-charm
CHARM 2015
•SM
•no mixing
• Measurements will remain interesting in the next decade
SUSY: interplay with LHC searches (required degeneracy of squarks)
• Direct CPV: ∆ACP ≡ AK+K− −Aπ+π− = −(8.2± 2.4)× 10−3 (LHCb, 2011)
Current WA: ∆ACP = −(2.5± 1.0)× 10−3 ↖(a stretch in the SM, imho)
• I think we still don’t know how big an effect could (not) be accommodated in SM
Z L – p. 23
Very broad program
• Many fascinating topics I cannot talk about — hundreds of papers on each:
– B → K(∗)`+`− and B → Xs`+`−: first observations to good precision
– Search for decays violating conservation laws
– Search for invisible modes
– Hidden sector searches
– New hadronic states
Z L – p. 24
Very broad program
• Many fascinating topics I cannot talk about — hundreds of papers on each:
– B → K(∗)`+`− and B → Xs`+`−: first observations to good precision
– Search for decays violating conservation laws
– Search for invisible modes
– Hidden sector searches
– New hadronic states
I do not know how many CP violating quantities have been measured, neitherhow many new hadronic states discovered / seen by BABAR
Anyone...?
Z L – p. 24
Putting it all together: the SM CKM fit
• Huge progress compared to pre-BABAR
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1ρ_
η_
(BABAR Physics Book, 1998, p.957)
γ
γ
α
α
dm∆
Kε
Kε
sm∆ & dm∆
ubV
βsin 2
(excl. at CL > 0.95)
< 0βsol. w/ cos 2
exc
luded a
t CL >
0.9
5
α
βγ
ρ
1.0 0.5 0.0 0.5 1.0 1.5 2.0η
1.5
1.0
0.5
0.0
0.5
1.0
1.5
excluded area has CL > 0.95
EPS 15
CKMf i t t e r
• KM phase is the dominant source of CPV in flavor changing transitions of quarks
Z L – p. 25
Nobel Prize 2008
• Before BABAR we did not know that the CKMpicture was (essentially) correct
O(1) deviations in CP violation were possible
• Nobel Prize is formal recognition that the KMphase is established as the dominant sourceof CPV in flavor changing transitions of quarks
• Confirmation of the SM ⇒ looking for corrections to the SM
• Future: What can flavor physics teach us about beyond SM physics?
Z L – p. 26
New physics in meson mixing
• Meson mixing:
Meson mixing:
Simple parametrization:M12 = MSM
12 (1+he2iσ)
SM: CSM
m2W
NP: CNP
Λ2
What is the scale Λ? How different is CNP from CSM?
If deviation from SM seen⇒ upper bound on Λ
• Assume: (i) 3× 3 CKM matrix is unitaryAssume: (ii) tree-level decays dominated by SM
• Mature topic, conservative picture of future progress
Z L – p. 27
The CKM fit with NP allowed in mixing
• Allowed ρ– η region becomes much larger: [1309.2293]
2003 2013 LHCb 50/fb + Belle II 50/ab
ubV
α
βγ
ρ
1.0 0.5 0.0 0.5 1.0 1.5 2.0
η
1.5
1.0
0.5
0.0
0.5
1.0
1.5
excluded area has CL > 0.95
2003
CKMf i t t e r γ
γ
)α(γ
)α(γ
ubV
ubV) & α(γ & γ
α
βγ
ρ
1.0 0.5 0.0 0.5 1.0 1.5 2.0
η
1.5
1.0
0.5
0.0
0.5
1.0
1.5
excluded area has CL > 0.95
2013
CKMf i t t e r
)_(a
)_(a
a
a
ubV
ubV) & _(a & a
_
`a
l
-1.0 -0.5 0.0 0.5 1.0 1.5 2.0
d
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
excluded area has CL > 0.95
Stage II
CKMf i t t e r
_
0.05 0.10 0.15 0.20 0.250.25
0.30
0.35
0.40
0.45
Tree-level constraints unaffected, loop-dominated observables sensitive to NP
• Tree-level measurements (Vub, γ) crucial to isolate new physics contributions
Z L – p. 28
New physics in B0d mixing
2003 Now LHCb 50/fb + Belle II 50/ab
dh0.0 0.5 1.0 1.5 2.0 2.5 3.0
dσ
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0pvalue
excluded area has CL > 0.95
2003
CKMf i t t e r
dh0.0 0.1 0.2 0.3 0.4 0.5
dσ
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0pvalue
excluded area has CL > 0.95
2013
CKMf i t t e r
HFAG 2014s
φ
dh0.0 0.1 0.2 0.3 0.4 0.5
dσ
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0pvalue
excluded area has CL > 0.95
Stage II
CKMf i t t e r
[color: 2σ, dotted: 3σ] M(d)12 = MSM
12 × (1 + hd e2iσd) [1309.2293]
NP <∼ (many×SM) → NP <∼ (0.3 × SM) → NP <∼ (0.05 × SM)
h '|Cij|2
|V ∗ti Vtj|2
(4.5 TeV
Λ
)2
— will reach: Λ ∼
{2.3× 103 TeV
20 TeV (tree + CKM)2 TeV (loop + CKM)
• Right sensitivity to be in the ballpark of gluino masses explored at LHC14
Z L – p. 29
Sensitivity to NP in B0d and B0
s mixing
2003 Now LHCb 50/fb + Belle II 50/ab
dh0.0 0.5 1.0 1.5 2.0 2.5 3.0
sh
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0pvalue
excluded area has CL > 0.95
2003
CKMf i t t e r
dh0.0 0.1 0.2 0.3 0.4 0.5
sh
0.0
0.1
0.2
0.3
0.4
0.5
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0pvalue
excluded area has CL > 0.95
2013
CKMf i t t e r
HFAG 2014s
φ
dh0.0 0.1 0.2 0.3 0.4 0.5
sh
0.0
0.1
0.2
0.3
0.4
0.5
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0pvalue
excluded area has CL > 0.95
Stage II
CKMf i t t e r
[color: 2σ, dotted: 3σ] M(q)12 = MSM
12 × (1 + hq e2iσq) [1309.2293]
NP <∼ (many×SM) → NP <∼ (0.3 × SM) → NP < (0.05 × SM)
Sensitivity caught up with that in Bd mixing, and will improve comparably
• MFV and non-MFV regions will have comparable constraints (unlike in the past)
Z L – p. 30
Future
Missed opportunity
• Dave and I were in the small minority convinced >10 yearsago that a super B factory at SLAC should be a part of ahealthy US HEP program
(My first super-BABAR talk in 2001, Dave’s probably 1–2 years earlier)
• “Lower bound” on future progress (only statistics improvements, maximally conservative)
(2009 BABAR data set)(1999 CLEO data set)
∼(Belle II data set)(Belle data set)
∼(LHCb upgrade)
(LHCb 1 fb−1)∼ 50
Increase in sensitivity to high scales 4√
50 ∼ 2.5, similar to LHC 7-8→ LHC 13-14(Expect unexpected progress — data has always motivated new ideas)
Z L – p. 31
Questions for the future
• Will LHC see new particles beyond the Higgs?SUSY, something else, understand in detail?
• Will NP be seen in the quark sector?
Near future: current anomalies have the largestchance to become significant
Several hints of lepton flavor universality violation
With 50/fb LHCb and 50/ab Belle II data,large discovery potential in many modes
• Will NP be seen in the lepton sector (CLFV)?µ→ eγ, µ→ eee, τ → µγ, τ → µµµ, ...?
Current flavor anomalies
1 2 3 4
significance (σ)
f(t
heo
reti
cal
clea
nlin
ess)
h→τμ
B→Ke+e-/B→Kμ+μ-
D0 μμ CP asym
B→D(*)τνBd→μμ
B→K *μ+μ- angular
Bs→ϕμ+μ-
|Vcb| incl/excl
|Vub| incl/excl
g-2
ϵ'/ϵ
• No one knows — that’s why it’s research...
Z L – p. 32
The B → D(∗)τ ν story: ∼4σ
• Belle & LHCb results on the anomaly seen by BABAR in R(X) =Γ(B → Xτν)
Γ(B → X(e/µ)ν)
R(D) R(D∗)
BABAR 0.440± 0.058± 0.042 0.332± 0.024± 0.018
Belle 0.375± 0.064± 0.026 0.293± 0.038± 0.015
LHCb 0.336± 0.027± 0.030
Average 0.391± 0.050 0.322± 0.022
SM expectation 0.300± 0.010 0.252± 0.005
Belle II, 50/ab ±0.010 ±0.005R(D)
0.2 0.3 0.4 0.5 0.6
R(D
*)
0.2
0.25
0.3
0.35
0.4
0.45
0.5BaBar, PRL109,101802(2012)Belle, arXiv:1507.03233LHCb, arXiv:1506.08614Average
= 1.02χ∆
SM prediction
HFAG
EPS 2015
) = 55%2χP(
HFAG
Prel. EPS2015
SM predictions fairly robust: heavy quark symmetry + lattice QCD for R(D) [1503.07237, 1505.03925]
• Tension: R(D(∗)) vs. B(b→ Xτ+ν) = (2.41± 0.23)% (LEP) [ZL, Tackmann]
Tension: SM predicts R(Xc) = 0.223± 0.004 — precisely [Freytsis, ZL, Ruderman]
Need NP at fairly low scales (leptoquarks, W ′, etc.), likely visible in LHC Run 2
• Soon: LHCb result with hadronic τ decays, measure R(D), maybe Λb decay
Z L – p. 33
What are the largest useful data sets?
• Which measurements will remain far from being limited by theory uncertainties?
– For γ ≡ φ3, theory limit only from higher order electroweak
– Bs,d → µµ, B → µν and other leptonic decays (lattice QCD, [double] ratios)
– Probably CP violation in D mixing (firm up theory)
– Ad,sSL (can get around exp. syst. limits?)
– CLFV, EDM, etc.
• Crude guess: until∼102× Belle II & LHCb upgrade data, sensitivity to high scaleswould improve
• In some decay modes, even in 2030 we’ll have: (exp. bound)/
SM >∼ 103
E.g., B → τ+τ−, e+e− — can build models... I hope to be wrong!
Z L – p. 34
Conclusions — have come a long way
• Flavor physics probes scales�1 TeV; sensitivity limited by statistics, not theory
• New physics in most FCNC processes may still be ∼ 20% of the SM, or more
• Few tensions with the SM; some of these (or others) may become decisive
• Precision tests of SM will improve by 101 – 104 in many channels (CLFV)
I think Mu2e is fantastic — good luck, Dave!
• Many interesting theoretical questions, relevant for experimental sensitivity
• I cannot imagine a scenario in which there is no complementarity between flavorand LHC searches of new physics, and hopefully understanding it
Z L – p. 35
Bonusl slides
The big question: where is new physics?
1 3 5 7 9 11 13 15 17
Tevatron
proton decay
flavor (quarks)
Experimental reach (with significant simplifying assumptions)
log(Energy[GeV])
LHC
dark matter
mu to e
neutrino propertiesE
WS
B
see−
saw
GU
T
Pla
nck
Dashed arrows show anticipated improvements in next generation of experiments
– Proton decay already ruled out simplest version of grand unification
– Neutrino experiments hope to probe see-saw mechanism
– Flavor physics probes TeV-scale new physics with even SM-like suppressions
– LHC was in a unique situation that a discovery was virtually guaranteed (known since 80’s)
Z L – p. i
Push Bs,d→ µ+µ− to theory limit
• For Bd, CMS (LHCb) expect ultimately 15–20% (30–40%) precision at SM level
SM uncertainty ' (2%)⊕ f2Bq⊕ CKM [Bobeth, FPCP’15]
]9−[10)−µ+µ→0BB(0 0.2 0.4 0.6 0.8
LlnΔ2−
0
2
4
6
8
10SM
]9−[10)−µ+µ→s0BB(
0 2 4 6 8
LlnΔ2−
0
10
20
30
40SM
]9−[10)−µ+µ→s0BB(
0 1 2 3 4 5 6 7 8 9
]9−[1
0)− µ
+ µ→
0B
B(
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
68.27%
95.45%
99.73% 5−10
×6.3
−1
7−10
×5.7
−1
9−10
×2−1
SM
CMS and LHCb (LHC run I)
a
b
c
[LHCb & CMS, 1411.4413]
• Theoretically cleanest |Vub| I know, only isospin: B(Bu → `ν)/B(Bd → µ+µ−)
• A decay with mass-scale sensitivity (dim.-6 operator) that competes w/ K → πνν
Z L – p. ii
Bound on vector-like fermions
• Do not make hierarchy problem worse; vector-like fermions can Yukawa couple tothe SM fermions via the Higgs in 11 models (⇒ FCNC Z couplings) [Ishiwata, ZL, Wise]
ModelQuantum Present bounds on M/TeV and λiλj for each ij pair
numbers ij = 12 ij = 13 ij = 23
I (1, 1,−1) 310a 7.0b 7.4c
II (1, 3,−1) 220a 4.9b 5.2c
III (1, 2,−1/2) 310a 7.0b 7.4c
IV (1, 2,−3/2) 310a 7.0b 7.4c
∆F = 1 ∆F = 2 ∆F = 1 ∆F = 2 ∆F = 1 ∆F = 2
V (3, 1,−1/3) 66d [100]e {42, 670}f 30g 25h 21i 6.4j
VI (3, 1, 2/3) 3.9k {42, 670}f — 25h — 6.4j
VII (3, 3,−1/3) 47d [71]e {47, 750}f 21g 28h 15i 7.2j
VIII (3, 3, 2/3) 66d [100]e {47, 750}f 30g 28h 21i 7.2j
IX λ(u)}(3, 2, 1/6)
3.9k 67l — 35h — 9.1j
IX λ(d) 66d [100]e {59, 950}f 30g 35h 18m 9.1j
X (3, 2, 7/6) 3.9k 48l — — — —
XI (3, 2− 5/6) 66d [100]e {42, 670}f 30g 25h 18m 6.4j
Strongest bounds from large variety of processes: a) µ to e conversion; b) τ → eπ; c) τ → µρ; d) K → πνν; e) KL →
µ+µ−; f)K mixing; g)B → πµ+µ−; h)Bd mixing; i)B → Xs`+`−; j)Bs mixing; k)D → µ+µ−; l)Dmixing;m)Bs → µ+µ−
Z L – p. iii
Vector-like fermions — future bounds
• Planned experiments increase sensitivity in mass scales by factors of 2.5− 7
ModelQuantum Future bounds on M/TeV and λiλj for each ij pair
numbers ij = 12 ij = 13 ij = 23
I (1, 1,−1) 2000a 19b 21c
II (1, 3,−1) 1400a 13b 15c
III (1, 2,−1/2) 2000a 19b 21c
IV (1, 2,−3/2) 2000a 19b 21c
∆F = 1 ∆F = 2 ∆F = 1 ∆F = 2 ∆F = 1 ∆F = 2
V (3, 1,−1/3) 280d {100, 1000}e 60f 61g 39h 14i
VI (3, 1, 2/3) 8.3j {100, 1000}e — 61g — 14i
VII (3, 3,−1/3) 200d {110, 1100}e 42f 68g 28h 16i
VIII (3, 3, 2/3) 280d {110, 1100}e 60f 68g 39h 16i
IX λ(u)}(3, 2, 1/6)
8.3j 67k — 86g — 20i
IX λ(d) 280d {140, 1400}e 60f 86g 39h 20i
X (3, 2, 7/6) 8.3j 48k — — — —
XI (3, 2− 5/6) 280d {100, 1000}e 60f 61g 39h 14i
Expected best sensitivity from large variety of processes: a) µ to e conversion; b) τ → eπ; c) τ → µρ; d) K → πνν; e) K
mixing; f) Bd → µ+µ−; g) Bd mixing; h) Bs → µ+µ−; i) Bs mixing; j) D → µ+µ−; k) D mixing.
Z L – p. iv
A super-B best buy list
• Want observables: (i) sensitive to different NP, (ii) measurements can improve byan order of magnitude, and (iii) not limited by hadronic uncertainties:
• Difference of CP asymmetries, SψKS − SφKS• γ from CP asymmetries in tree-level decays vs. γ from SψKS and ∆md/∆ms
• Search for charged lepton flavor violation, τ → µγ, τ → 3µ, and similar modes
• Search for CP violation in D0 −D0 mixing
• The CP asymmetry in semileptonic decay, ASL
• The CP asymmetry in the radiative decay, SK∗γ
• Search for not yet seen FCNC decays and refinements: b→ sνν, B → τ ν, etc.
• Any one of these measurements has the potential to establish new physics
Z L – p. v
Some theory challenges
• New methods & ideas: recall that the best α and γ measurements are in modesproposed in light of Belle & BABAR data (i.e., not in the BABAR Physics Book)
– Better SM upper bounds on Sη′KS − SψKS, SφKS − SψKS, and Sπ0KS− SψKS
– (and similarly in Bs decays)
– How big can CP violation be in D0 –D0 mixing (and in D decays) in the SM?
– Better understanding of semileptonic form factors; bound on SKSπ0γ in SM?
– Inclusive & exclusive semileptonic decays
– Many lattice QCD calculations (operators within and beyond SM)
– Factorization at subleading order (different approaches), charm loops
– Can direct CP asymmetries in nonleptonic modes be understood enough to– make them “discovery modes”? [SU(3), the heavy quark limit, etc.]
• We know how to make progress on some + discover new frameworks / methods?
Z L – p. vi
Charged lepton flavor violation
• SM predicted lepton flavor conservation with mν = 0
Given mν 6= 0, no reason to impose it as a symmetry
• If new TeV-scale particles carry lepton number(e.g., sleptons), then they have their own mixingmatrices⇒ charged lepton flavor violation
• Many interesting processes:µ→ eγ, µ→ eee, µ+N → e+N (′), µ+e− → µ−e+
τ → µγ, τ → eγ, τ → µµµ, τ → eee, τ → µµe
τ → µee, τ → µπ, τ → eπ, τ → µKS, eN → τN
B(µ→ eγ) ∼ αm4ν
m4W
∼ 10−52
1940 1950 1960 1970 1980 1990 2000 2010 2020 2030
-1910
-1710
-1510
-1310
-1110
-910
-710
-510
-310
-110
1
• Next 10–20 years: 102–105 improvement; any signal would trigger broad program
Z L – p. vii
Electric dipole moments and SUSY
• SM + mν: CPV can occur in: (i) quark mixing; (ii) lepton mixing; and (iii) θQCD
Only observed δKM 6= 0, baryogenesis implies there must be more
• Neutron EDM bound: “The strong CP problem”, θQCD < 10−10 — axion?θQCD is negligible for CPV in flavor-changing processes
• EDMs from CKM: vanish at one- and two-loopEDMs from CKM: large suppression at three-loop level
• E.g., SUSY: quark and lepton EDMs can be generated at one-loop
Generic prediction (TeV-scale, no small param’s) above cur-rent bounds; if mSUSY ∼ O(10 TeV), may still discover EDMs
• Expected 102–103 improvements: complementary to LHCDiscovery would give (rough) upper bound on NP scale
Z L – p. viii
LBL Contributions
ConceptionDesign
Fabrication
CommissioningOperations/Calibration
Reco/Simulation
Analysis
upgrade
LBNL BaBar:
Doing the Physics from Start to Finish
B→VV
B→φK
B→Ds π
B→ρπ
CPT,∆Γ
New computing model
Alignment
Trigger
DIRC
SVT
P. Oddone, Panofsky prize 2005
c© R. Cahn