lhc physics: higgs and beyond...“intermediate” bsm sector non-sm flavor probe physics at energy...
TRANSCRIPT
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Lecture I: What we learned from run-I[The SM as an effective theory & the “ghost” of the anthropic principle] Lecture II: What we can hope to learn from run-II (at high-pT)[Future prospects in Higgs physics and direct NP searches]
Lecture III: Indirect searches for NP[Flavor physics beyond the SM]
LHC Physics: Higgs and beyond
Gino Isidori[ University of Zürich ]
(a personal selection of topics in the wast domain of LHC physics)
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
IntroductionThe flavor sector of the SM
Present status of CKM fitsThe flavor structure of the SM viewed as EFT
The flavor problemThe MFV hypothesisVariations on the “MFV theme”
Speculations on the breaking of LFU in B decaysRecent anomalies in B physicsSpeculations on the breaking of LFU
Conclusions
Lecture III: Indirect searches for NP[Flavor physics beyond the SM]
Introduction
Twofold role of Flavor Physics[ = study of flavor-changing and CPV phenomena, of both quarks and leptons]
We need to search for New Physics [with a broad spectrum perspective given the lack of NP signal so far...]
Indirect probe of physics at energy scales not directly accessible at accelerators
Identify symmetries and symmetry-breaking patterns beyond those present in the SM
The SM is likely to be an effective theory, i.e. the limit(in the experimentally accessible range of energies and effective couplings)
of a more fundamental theory, with new degrees of freedom
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Twofold role ofFlavor Physics
SM
flavor-violatinginteractions
High-scale[flavor-symmetric?]
theory
Identify symmetries and symmetry-breaking patterns beyond those present in the SM
Higgssector
The observed pattern of fermion masses angles does not seem to be accidental !
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Introduction
Twofold role ofFlavor Physics
SM +
flavor-violatinginteractions
High-scale[flavor-symmetric?]
theory
Higgssector
“intermediate”BSM sector
non-SMflavor
Probe physics at energy scales not directly accessible at accelerators
Identify symmetries and symmetry-breaking patterns beyond those present in the SM
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Introduction
With flavor physics we address the second set of key questions of particle physics:
What determines the Higgs mass term (or the Fermi scale)?
Is there anything else beyond the SM Higgs at the TeV scale?
What determines the observed pattern of masses and mixing angles of quarks and leptons?
Which are the sources of flavor symmetry breaking accessible at low energies? [Is there anything else beside SM Yukawa couplings & neutrino mass matrix?]
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
High-energy searches[the high-energy frontier]
High-precision measurements [the high-intensity frontier]
Introduction
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The flavor sector of the SM
3 identical replica of the basic fermion family [ψ = QL , uR, dR, LL, eR ] ⇒ huge flavor-degeneracy: U(3)5 global symmetry
ℒSM = ℒgauge (Aa, ψi) + ℒHiggs(ϕ, Aa, ψi )
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The flavor structure of the SM
The gauge Lagrangian is invariant under 5 independent U(3) global rotations for each of the 5 independent fermion fields
E.g.: QLi → Uij
QLj
U(1) flavor-independent phase +
SU(3) flavor-dependent mixing matrix
Σ ψ = QL , uR ,dR ,LL ,eR Σi=1..3 ψi iD ψi
QL = uL
dL
LL = νL
eL
, uR , dR , , eR
3 identical replica of the basic fermion family [ψ = QL , uR, dR, LL, eR ] ⇒ huge flavor-degeneracy: U(3)5 global symmetry
ℒSM = ℒgauge (Aa, ψi) + ℒHiggs(ϕ, Aa, ψi )
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The flavor structure of the SM
U(1)L × U(1)B × U(1)Y × SU(3)Q × SU(3)U × SU(3)D ×...
Flavor mixingLepton numberBarion number
Hypercharge
3 identical replica of the basic fermion family [ψ = QL , uR, dR, LL, eR ] ⇒ huge flavor-degeneracy: U(3)5 global symmetry
ℒSM = ℒgauge (Aa, ψi) + ℒHiggs(ϕ, Aa, ψi )
Within the SM the flavor-degeneracy is broken only by the Yukawa interaction:
QLi YD
ik dRk ϕ + h.c. → dL
i MDik dR
k + ...
QLi YU
ik uRk ϕc + h.c. → uL
i MUik uR
k + ...
in the quarksector:
_
_
_
_
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The flavor structure of the SM
3 identical replica of the basic fermion family [ψ = QL , uR, dR, LL, eR ] ⇒ huge flavor-degeneracy: U(3)5 global symmetry
ℒSM = ℒgauge (Aa, ψi) + ℒHiggs(ϕ, Aa, ψi )
Within the SM the flavor-degeneracy is broken only by the Yukawa interaction:
QLi YD
ik dRk ϕ + h.c. → dL
i MDik dR
k + ...
QLi YU
ik uRk ϕc + h.c. → uL
i MUik uR
k + ...
in the quarksector:
_
_
_
_
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The flavor structure of the SM
The Y are not hermitian → diagonalized by bi-unitary transformations:
VD+ YD
UD = diag(yb , ys , yd)
VU+ YU
UU = diag(yt , yc , yu)yi = ≈
2½ mqi
〈 ϕ〉
mqi
174 GeV
3 identical replica of the basic fermion family [ψ = QL , uR, dR, LL, eR ] ⇒ huge flavor-degeneracy: U(3)5 global symmetry
ℒSM = ℒgauge (Aa, ψi) + ℒHiggs(ϕ, Aa, ψi )
Within the SM the flavor-degeneracy is broken only by the Yukawa interaction:
QLi YD
ik dRk ϕ + h.c. → dL
i MDik dR
k + ...
QLi YU
ik uRk ϕc + h.c. → uL
i MUik uR
k + ...
in the quarksector:
_
_
_
_
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The flavor structure of the SM
YD = diag(yd ,ys ,yb)
YU = V+ × diag(yu ,yc ,yt)
The residual flavor symmetry let us to choose a (gauge-invariant) flavor basis where only one of the two Yukawas is diagonal:
YD = V × diag(yd ,ys ,yb)
YU = diag(yu ,yc ,yt)
V= unitary matrix
or
To diagonalize also the second mass matrix we need to rotate separately uL & dL (non gauge-invariant basis) ⇒ V appears in charged-current gauge interactions:
Jwμ = uL
γ μ dL → uL
V γμ dL
Cabibbo-Kobayashi-Maskawa(CKM) mixing matrix
_ _
MD = diag(md ,ms ,mb)
MU = V+ × diag(mu ,mc ,mt)
_
_
_
_
...however, it must be clear that this non-trivial mixing originates only from the Higgs sector: Vij → δij if we switch-off Yukawa interactions !
QLi YD
ik dRk ϕ → dL
i MDik dR
k + ...
QLi YU
ik uRk ϕc → uL
i MUik uR
k + ...
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The flavor structure of the SM
To diagonalize also the second mass matrix we need to rotate separately uL & dL (non gauge-invariant basis) ⇒ V appears in charged-current gauge interactions:
Jwμ = uL
γ μ dL → uL
V γμ dL
_ _
MD = diag(md ,ms ,mb)
MU = V+ × diag(mu ,mc ,mt)
_
_
_
_QL
i YDik dR
k ϕ → dL
i MDik dR
k + ...
QLi YU
ik uRk ϕc → uL
i MUik uR
k + ...
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The flavor structure of the SM
V CKM = [V ud V us V ub
V cd V cs V cb
V td V ts V tb]
3 real parameters (rotational angles)
+1 complex phase (source of CP violation)
The SM quark flavor sector is described by 10 observable parameters:
6 quark masses
3+1 CKM parameters
Cabibbo-Kobayashi-Maskawa(CKM) mixing matrix
To diagonalize also the second mass matrix we need to rotate separately uL & dL (non gauge-invariant basis) ⇒ V appears in charged-current gauge interactions:
Jwμ = uL
γ μ dL → uL
V γμ dL
_ _
MD = diag(md ,ms ,mb)
MU = V+ × diag(mu ,mc ,mt)
_
_
_
_QL
i YDik dR
k ϕ → dL
i MDik dR
k + ...
QLi YU
ik uRk ϕc → uL
i MUik uR
k + ...
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The flavor structure of the SM
The SM quark flavor sector is described by 10 observable parameters:
6 quark masses
3+1 CKM parameters
1-λ2/2 λ Aλ3(ρ-iη)
- λ 1-λ2/2 Aλ2
Aλ3(1-ρ-iη) -Aλ2 1
≈VCKM
Cabibbo-Kobayashi-Maskawa(CKM) mixing matrix
Present status of CKM fits
At present all the measurements of quark flavor-violating observables show a remarkable success of the CKM picture: we have a redundant and consistent determination of various CKM elements.
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
At present all the measurements of quark flavor-violating observables show a remarkable success of the CKM picture: we have a redundant and consistent determination of various CKM elements.
The agreement between data and SM expectations is even more striking if we consider other observables, not appearing in CKM fits, such as
BR(B → Xs γ) or the Bs mixing phase
Present status of CKM fits
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Significant constraints on the flavor structure of possible
new degrees of freedom
3 identical replica of the basic fermion family ⇒ huge flavor-degeneracy [U(3)5 symmetry]
Flavor-degeneracy broken only by the Yukawa interaction
several new sources of flavor symmetry breaking are, in principle, allowed
The redundancy of CKM fits allow us to investigate the flavor structure of the new degrees of freedom
which hopefully will show up above the electroweak scale
Λ = effective scale of new physics
+ Σ On(d) (ϕ, Aa, ψi)
cn
Λd-4 ℒeff = ℒgauge (Aa, ψi) + ℒHiggs(ϕ, Aa, ψi )
The flavor structure of the SM viewed as EFT
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Probing the flavor structure of physics beyond the SM requires the following three main steps:
Identify processes where the SM is calculable with good accuracy using the tree-level inputs, or sufficiently suppressed for null tests.
Determine the CKM elements from theoretically clean and non-suppressed tree-level processes, where the SM is likely to be largely dominant.
Measure with good accuracy these rare processes and determine the allowed room for new physics.
ΔF=2 Neutral meson mixing [ K, Bd, Bs + D]
CP-violating observables
Rare decays:FCNC modes (B→ll, BK* ll,...)Helicity-suppressed observables
Forbidden processes
Exclusive and inclusive semi-leptonic b→u decays ( |Vub| )
Selected non-leptonic B decays sensitive to γ
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The flavor problem
The “chain” mentioned before has already been closed, with quite good accuracy, in the case of down-type ΔF=2 observables (K0 and Bd,s mixing):
Highly suppressed amplitude potentially very sensitive
to New Physics
No SM tree-level contributionStrong suppression within the SM because of CKM hierarchy Calculable with good accuracy since dominated by short-distance dynamics [power-like GIM mechanism → top-quark dominance]Measurable with good accuracy from the time evolution of the neutral meson system
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The ΔF=2 bounds
b d
bd Vqd Vq'b*
Vqb* Vq'd
B B_
q'
q
b d
bd Vqd Vq'b*
Vqb* Vq'd
B B_
q'
power-like GIM mechanism:
AΔF=2 = Σq,q'=u,c,t (Vqb*Vqd) (Vq'b
*Vq'd) Aq'q
q
AΔF=2 = Σq=u,c,t (Vqb*Vqd) [ Vtb
*Vtd (Atq-Auq) + Vcb*Vcd (Acq-Auq) ]
[CKM unitarity]
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The ΔF=2 bounds
The “chain” mentioned before has already been closed, with quite good accuracy, in the case of down-type ΔF=2 observables (K0 and Bd,s mixing):
Vub*Vud = - Vtb
*Vtd - Vcb*Vcd
b d
bd Vqd Vq'b*
Vqb* Vq'd
B B_
q'
power-like GIM mechanism:
AΔF=2 = Σq,q'=u,c,t (Vqb*Vqd) (Vq'b
*Vq'd) Aq'q
q
AΔF=2 = Σq=u,c,t (Vqb*Vqd) [ Vtb
*Vtd (Atq-Auq) + Vcb*Vcd (Acq-Auq) ]
[CKM unitarity]
Aqq' ~
mq mq'
mW2
AΔF=2 ~ (Vtb*Vtd)2 + ...
g4mt2
16π2mW4
[expansion of the loop amplitude for small
(internal) quark masses]g4
16π2mW2
Const. + + ... ⟨ B| (bL γμ dL )
2 |B ⟩_ _
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The ΔF=2 bounds
The “chain” mentioned before has already been closed, with quite good accuracy, in the case of down-type ΔF=2 observables (K0 and Bd,s mixing):
Vub*Vud = - Vtb
*Vtd - Vcb*Vcd
bL dL
bLdL Yqd Yq'b*
Yqb* Yq'd
B B_
q'R
qR
The origin of this behavior can be better understood if we
switch-off gauge interactions (“gauge-less limit”)ϕ+
dLi YU
ik uRk ℒYukawa →
_ϕ- + h.c.
YU = V+ × diag(yu, yc, yt)
≈ V+ × diag(0, 0, yt)
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The ΔF=2 bounds
The “chain” mentioned before has already been closed, with quite good accuracy, in the case of down-type ΔF=2 observables (K0 and Bd,s mixing):
bL dL
bLdL Yqd Yq'b*
Yqb* Yq'd
B B_
tR
tR ϕ+
dLi YU
ik uRk ℒYukawa →
_ϕ- + h.c.
YU = V+ × diag(yu, yc, yt)
≈ V+ × diag(0, 0, yt)
ADF=2 ~ (Vtb*Vtd)2 ~ (Vtb
*Vtd)2(yt)
4
16π2mt2
This way we obtain the exact result of the amplitude in the limit mt ≫mW :
gaugeless g4 mt2
16π2mW4
mt = yt v / √2
mW = g v / 2
ADF=2 = ADF=2 × [ 1 + O(g2) ]full gauge-less
The origin of this behavior can be better understood if we
switch-off gauge interactions (“gauge-less limit”)
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The ΔF=2 bounds
The “chain” mentioned before has already been closed, with quite good accuracy, in the case of down-type ΔF=2 observables (K0 and Bd,s mixing):
ℒeff = ℒSM
(yt2 Vtb
*Vtd)2
16π2mt2
M(Bd−Bd) ~ + cNP
1
Λ2
_
+ Σ On(d) cn
Λd-4The list of dimension 6 ops. includes (bL
γμ dL )2 that contributes
to Bd mixing at the tree-level
bL dLρ'bd
dL bL
Possible dynamical origin of this d=6 operator:
The flavor problem
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The “chain” mentioned before has already been closed, with quite good accuracy, in the case of down-type ΔF=2 observables (K0 and Bd,s mixing), showing no significant deviations from the SM (at the 5%-30% level):
ℒeff = ℒSM
(yt2 Vtb
*Vtd)2
16π2mt2
M(Bd−Bd) ~ + cNP
1
Λ2
_
+ Σ On(d) cn
Λd-4
N.B.: In Kaon physics the CKM suppression is even stronger:
Bs-mix.: Vtb*Vts ~ λ2 Bd-mix.: Vtb
*Vtd ~ λ3 K-mix: Vts*Vtd ~ λ5
The list of dimension 6 ops. includes (bL
γμ dL )2 that contributes
to Bd mixing at the tree-level
The flavor problem
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The “chain” mentioned before has already been closed, with quite good accuracy, in the case of down-type ΔF=2 observables (K0 and Bd,s mixing), showing no significant deviations from the SM (at the 5%-30% level):
cNP
Serious conflict with the expectation of new physics around the TeV scale, to stabilize the electroweak sector of the SM [ The flavour problem ]
~ 1
~ 1(16π2)
Λ 2×104 TeV [K]
Λ 2×103 TeV [K]
treestrong + generic flavor
loop + generic flavor>~
>~
(yt2 Vtb
*Vtd)2
16π2mt2
M(Bd−Bd) ~ + cNP
1
Λ2
_
The flavor problem
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The “chain” mentioned before has already been closed, with quite good accuracy, in the case of down-type ΔF=2 observables (K0 and Bd,s mixing), showing no significant deviations from the SM (at the 5%-30% level):
~ 1
~ 1(16π2)
treestrong + generic flavor
loop + generic flavor
~ (yt Vti*Vtj)2
~ (yt Vti*Vtj)2(16π2)
Λ 5 TeV [K & B]
Λ 0.5 TeV [K & B]
treestrong + “alignment”
loop + “alignment”>~
>~cNP
Λ 2×104 TeV [K]
Λ 2×103 TeV [K]>~
>~
(yt2 Vtb
*Vtd)2
16π2mt2
M(Bd−Bd) ~ + cNP
1
Λ2
_
The flavor problem
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The “chain” mentioned before has already been closed, with quite good accuracy, in the case of down-type ΔF=2 observables (K0 and Bd,s mixing), showing no significant deviations from the SM (at the 5%-30% level):
~ 1
~ 1(16π2)
treestrong + generic flavor
loop + generic flavor
~ (yt Vti*Vtj)2
~ (yt Vti*Vtj)2(16π2)
Λ 5 TeV [K & B]
Λ 0.5 TeV [K & B]
treestrong + “alignment”
loop + “alignment”>~
>~cNP
Λ 2×104 TeV [K]
Λ 2×103 TeV [K]>~
>~
(yt2 Vtb
*Vtd)2
16π2mt2
M(Bd−Bd) ~ + cNP
1
Λ2
_
Comparable to the scales directly probed at the LHCand/or indirectly probed in precision Higgs physics
The flavor problem
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The “chain” mentioned before has already been closed, with quite good accuracy, in the case of down-type ΔF=2 observables (K0 and Bd,s mixing), showing no significant deviations from the SM (at the 5%-30% level):
Can we build NP models where the alignment with the CKM is “natural”?
Is there a unique form of alignment that allows Λ ~ 1 TeV?
Does this shed light on the origin of fermion masses and CKM hierarchies?
Can we see deviations from the SM with more precise measurements? Where?
Some partial answers in the rest of this lecture, hopefully more complete answers from future flavor-physics data...
New flavor-breaking sources at the TeV scale (if any) are highly tuned
The flavor problem
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
SU(3)Q×SU(3)U×SU(3)D
Quark Flavor
Group
YD
VCKM
YU
This specific symmetry + symmetry-breaking pattern is responsible for the GIM suppression of Flavor Changing Neutral Currents, the suppression of CPV,...
all the successful SM predictions in the quark flavor sector
Flavor symmetry: U(3)5 = SU(3)Q
×SU(3)U ×SU(3)D
×...
[global symmetry of the SM gauge sector]
Symmetry-breaking terms: YU & YD
[quark Yukawa couplings]
ℒSM = ℒgauge + ℒHiggs
QLi YU
ij UR
j ϕ + QL
i YD
ij DR
j ϕc
_ _
Minimal Flavor Violation
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Since the global flavor symmetry is already broken within the SM, is not consistent to impose it as an exact symmetry beyond the SM (fine-tuning, not invariant under quantum corrections)
However, we can (formally) promote this symmetry to be an exact symmetry, assuming the Yukawa matrices are the vacuum expectation values of appropriate auxiliary fields:
_ _E.g.: YD ~ (3,1,3) & YU ~ (3,3,1) under SU(3)Q
L×SU(3)U
R×SU(3)D
R
(1,1,3) (3,1,1) _
(3,1,3) _
(1,1,1) = invariant
ℒYukawa = QL YD DR ϕ + QL YUUR ϕc + LL YL eR ϕ + h.c._ _ _
Minimal Flavor Violation
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
SU(3)Q×SU(3)U×SU(3)D
Quark Flavor
Group
YD
VCKM
YUFlavor symmetry: U(3)5 = SU(3)Q
×SU(3)U ×SU(3)D
×...
[global symmetry of the SM gauge sector]
Symmetry-breaking terms: YD ~ 3Q
×
3D
Y5YU ~ 3Q ×
3U
_ _
[quark Yukawa couplings]
A natural mechanism to reproduce the SM successes in flavor physics -without fine tuning- is the MFV hypothesis:
Yukawa couplings = unique sources of flavor symmetry breaking also beyond SM
Minimal Flavor Violation
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
General principle (RGE invariant) which can be applied to any TeV-scale new-physics model
unknown“flavor-blind”
dynamics
⟨Y ⟩ ⟨Y ⟩
ΛF
breaking of GF
by means of ⟨Y ⟩
Λ (~ TeV)
flavor-blind dynamics [non-SM degrees of freedom stabilizing the Higgs mass]
SM degreesof freedom
natural cut-off scale of the effectivetheory
Minimal Flavor Violation
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
YD = diag(yd ,ys ,yb) YU = V+ × diag(yu ,yc ,yt)
A low-energy EFT satisfies the criterion of MFV if all higher-dimensional operators, constructed from SM and Y fields, are (formally) invariant under the flavor group [ SU(3)Q×SU(3)U×SU(3)D ]
Typical FCNC dim.-6 operator: QLi (YUYU
+)ij QLj × LL LL
_ _
We can always choose a quark basis where:
(3,3,1) _
(1,1,1)
(3,3,1) _
yi = 2½ mqi
〈 ϕ〉
⟨Y ⟩ ⟨Y ⟩
Minimal Flavor Violation
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
YD = diag(yd ,ys ,yb) YU = V+ × diag(yu ,yc ,yt)
A low-energy EFT satisfies the criterion of MFV if all higher-dimensional operators, constructed from SM and Y fields, are (formally) invariant under the flavor group [ SU(3)Q×SU(3)U×SU(3)D ]
Typical FCNC dim.-6 operator:
We can always choose a quark basis where:
same CKM structure
of the dominant (top-induced or short-distance)
SM contribution !
(YU YU+)ij ≈ yt
2 V3iV3j *
V+ × diag( yu
2, yc2, yt
2 ) × V
≈ V+ × diag(0, 0, yt
2) × V
yi = 2½ mqi
〈 ϕ〉
QLi (YUYU
+)ij QLj × LL LL
_ _
Minimal Flavor Violation
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Flavor symmetry: U(3)5 = U(3)Q
×U(3)U ×U(3)D
×...
Symmetry-breaking terms: YD ~ 3Q
×3D YU ~ 3Q×3U
o_ _
General principle that can be implemented independently of the specific high-energy completion of the theory
Within the generic effective theory approach, the bounds on the scale of New Physics are reduced to few TeV (at most)
It leads to a very predictive framework:
Main virtues:
All flavor-changing loop-induced amplitudes have the same CKM/Yukawa structure as in the SM. Only the flavor-independent magnitude of the transition amplitudes can be modified.
U(3)Q×U(3)U×U(3)D
Quark Flavor
Group
YU
YD
VCKM
Basic assumptions:
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
All flavor-changing loop-induced amplitudes have the same CKM/Yukawa structure as in the SM [e.g.: A(sdZ) ~ Vts
*Vtd, A(bsZ) ~ Vtb*Vts, …].
Only the flavor-independent magnitude can be modified
Z
dLsL newd.o.f.
Yst + Ytd
A(sdZ)
A(bsZ)
Vtd
Vtb= as in the SM...
As a result, the most the tight experimental constraints on rare processes are naturally satisfied:
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
A few important comments:
I) MFV is not a theory of flavor
It does not allow us to compute the Yukawa couplings in terms of some more fundamental parameters
It is a useful predictive (hence falsifiable) construction that allow us to identify which are the irreducible sources of flavor-symmetry breaking
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
A few important comments:
I) MFV is not a theory of flavor
To prove MFV from data we would need to
observe some deviation form the SM in rare processes
observe the CKM pattern predicted by MFV [within same type of amplitudes]
In most of the processes measured so far we cannot go beyond the 10%-20% level of precision (even if the exp. precision is much better) because of irreducible theoretical uncertainties on evaluating the overall strength of the SM amplitude (non-perturbative effects of strong interactions)
Some more rare decays not observed so far could provide more useful infos.Very interesting candidates: Bd,s l
+l- (currently under investigation @ LHC)
1
Λ2 A[b→d(s)] ∼ Vtd(s) cSM + cNP
1
MW2
(0) (0)
II) Despite its phenomenological success, MFV is far from being “verified”
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Typical examples: Bd,s l
+l-
... and, hopefully, spectacular NP effects in the charged lepton sector:
B(μ→eγ) could reach values in the 10-12 - 10-13 range (within the reach of MEG)
Sizable enhancements still possible in models with an extended Higgs sector
A few important comments:
I) MFV is not a theory of flavor
III) Even within the “pessimistic” MFV hypothesis, we can still expect sizable deviations from the SM in various B physics observables...
II) Despite its phenomenological success, MFV is far from being “verified”
µ eTeV-scale
new physics
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
U(3)3 = U(3)Q×U(3)U×U(3)D
Largest flavor symmetry group compatible with the SM gauge symmetry
MFV hypothesis: the Yukawa couplings are the only breaking terms of this large flavor symmetry group
U(3)Q×U(3)U×U(3)D
Quark Flavor
Group
YD
VCKM
YUSmall deviations from the SM in flavor-violating observables (in agreement with data)
virtue main problemNo explanation for Y hierarchies (non-dynamical spurion analysis)
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Variations on the “MFV theme”
U(3)3 = U(3)Q×U(3)U×U(3)D
U(2)3 = U(2)Q×U(2)U×U(2)D
Barbieri, G.I., Jones-Perez,Lodone, Straub, '11
Largest flavor symmetry group compatible with the SM gauge symmetry
MFV = minimal breaking of U(3)3 by (3,3) terms [SM Yukawa couplings]
acting on 1st& 2nd generations
Same protection of FCNCs+
Additional virtue:
The exact symmetry limit is good starting point for the SM spectrum (mu=md=ms=mc=0, VCKM=1) → small breakings terms needed
An interesting variation of MFV is obtained considering the following subgroup:
Yu = yt 0
0 1
V
0 1
0 0 Δ
|V| ~ 0.04 |Δ| ~ 0.006
Unbrokensymmetry
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Variations on the “MFV theme”
U(3)3 = U(3)Q×U(3)U×U(3)D
U(2)3 = U(2)Q×U(2)U×U(2)D
Barbieri, G.I., Jones-Perez,Lodone, Straub, '11
Largest flavor symmetry group compatible with the SM gauge symmetry
MFV = minimal breaking of U(3)3 by (3,3) terms [SM Yukawa couplings]
acting on 1st& 2nd generations
An interesting variation of MFV is obtained considering the following subgroup:
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Variations on the “MFV theme”
Large mass gap (several TeV) not controlled by flavor symmetries (as opposite to MFV)and fine-tuning considerations
This flavor symmetry is particularly interesting in the SUSY context, since it allow to realize the“split-family” scenario discussed yesterday:
Speculations on the breaking of LFU in B physics
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Recent anomalies in B physics
A series of recent (and less recent) anomalies in B physics have received a lot of attention recently:
Beside the significance of each anomaly, what makes them particularly (at least in my opinion) is the fact they all seem to be connected to a possible violation of Lepton Flavor Universality
I. Anomalies in B → D(*) τν [LHCb, Belle, Babar]
II. Anomalies in B → K(*) μμ / ee [LHCb]
I. Anomalies in B → D(*) τν [LHCb, Belle, Babar]
Test of LFU in charged currents [τ vs. light leptons (μ, e) ]:
SM prediction quite solid: f.f. uncertainty cancel (to a good extent...) in the ratio Consistent exp. results by 3 (very) different experiments
NEW → NEW →
~1.8σ ~3.2σ
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Test of LFU in charged currents [τ vs. light leptons (μ, e) ]:
SM prediction quite solid: f.f. uncertainty cancel (to a good extent...) in the ratio Consistent exp. results by 3 (very) different experiments
4σ excess over SM (if D and D* combined)The two channels are well consistent with a universal enhancement (~30%) of the SM bL → cL τL νL amplitude (RH or scalar amplitudes disfavored)
M. Rotondo
bL cL
WτL νL
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
I. Anomalies in B → D(*) τν [LHCb, Belle, Babar]
II. Anomalies in B → K(*) μμ / ee [LHCb]
The largest anomaly is the one [obs. in 2013 and confirmed with higher stat. in 2015] in the P5' [B → K*μμ] angular distribution.But less significant anomalies present also in other B → K*μμ observables and also in other b→sμμ channels [overall smallness of all BR(B → Hadron + μμ)]
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
II. Anomalies in B → K(*) μμ / ee [LHCb]
The largest anomaly is the one [obs. in 2013 and confirmed with higher stat. in 2015] in the P5' [B → K*μμ] angular distribution.But less significant anomalies present also in other B → K*μμ observables and also in other b→sμμ channels [overall smallness of all BR(B → Hadron + μμ)]
B → K(*) ll are FCNC amplitudes (“natural” probes of physics beyond the SM):
No SM tree-level contributionStrong suppression within the SM because of CKM hierarchy
Key point to be addressed: th. control of QCD effects
I. Construction of a local eff. Hamiltonian at the electroweak scale
Three-step procedure to deal with the various scales of the problem:
Heff = Σi Ci(MW) Qi b s
Heavy NP encoded in the Ci(MW) No difference among all b → s ll decays
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Mixing of the four-quark Qi into the FCNC Qi [“dilution” of the potentially interesting NP]:
g
Q2 c, u
p ~ μ
b
s
II. Evolution of Heff down to low scales using RGE
Negligible for Q10 [Bs,d → ll & B → K(*)ll ]
Large for “photon penguins” Q9 [ B → K(*)ll only]
Heff = Σi Ci(MW) Qi
Heff = Σi Ci(μ ~ mb) Qi
FCNC operators (E.W. penguins)
Q9= Q
f(b s)
V −A(l l)
V
Q10=Q
f(b s)
V−A(l l)
A
⋮
Four-quark (tree-level) ops.:
Q1=(b s)
V−A(c c)
V −A
Q2=(bc)
V−A(c s)
V−A
⋮
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
II. Evolution of Heff down to low scales using RGE
Heff = Σi Ci(MW) Qi
Heff = Σi Ci(μ ~ mb) Qi
FCNC operators (E.W. penguins)
Q9= Q
f(b s)
V −A(l l)
V
Q10=Q
f(b s)
V−A(l l)
A
⋮
Four-quark (tree-level) ops.:
Q1=(b s)
V−A(c c)
V −A
Q2=(bc)
V−A(c s)
V−A
⋮
III. Evaluation of the hadronic matrix elements
sensitivity to long-distances (cc threshold...)
distinction between different modes
A(B → f ) = Σi Ci(μ) ⟨ f | Qi |B ⟩ (μ)
non-perturbative effects...
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
II. Anomalies in B → K(*) μμ / ee [LHCb]
The largest anomaly is the one [obs. in 2013 and confirmed with higher stat. in 2015] in the P5' [B → K*μμ] angular distribution.But less significant anomalies present also in other B → K*μμ observables and also in other b→sμμ channels [overall smallness of all BR(B → Hadron + μμ)]
observables designed to cancel f.f. dependence in the HQ limit
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
II. Anomalies in B → K(*) μμ / ee [LHCb]
The largest anomaly is the one [obs. in 2013 and confirmed with higher stat. in 2015] in the P5' [B → K*μμ] angular distribution.But less significant anomalies present also in other B → K*μμ observables and also in other b→sμμ channels [overall smallness of all BR(B → Hadron + μμ)]
Against NP: Main effect in P5' not far from cc threshold“NP” mainly in C9 (↔ charm)
Significance reduced with conservative estimates of non-factorizable corrections
Pro NP: Reduced tension in all the observables with a unique fit of non-standard Ci(MW)
Jaeger et al. '12 Hambrock et al. '13, Hiller & Zwicky '13, Lyon & Zwicky '14
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
II. Anomalies in B → K(*) μμ / ee [LHCb]
The largest anomaly is the one [obs. in 2013 and confirmed with higher stat. in 2015] in the P5' [B → K*μμ] angular distribution.But less significant anomalies present also in other B → K*μμ observables and also in other b→sμμ channels [overall smallness of all BR(B → Hadron + μμ)]
Against NP: Main effect in P5' not far from cc threshold“NP” mainly in C9 (↔ charm)
Significance reduced with conservative estimates of non-factorizable corrections
Pro NP: Reduced tension in all the observables with a unique fit of non-standard Ci(MW)
Jaeger et al. '12 Hambrock et al. '13, Hiller & Zwicky '13, Lyon & Zwicky '14
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
II. Anomalies in B → K(*) μμ / ee [LHCb]
Pro NP: Reduced tension in all the observables with a unique fit of non-standard short-distance Wilson coefficients Descotes-Genon, Matias, Virto '13, '15
Altmannshofer & Straub '13, '15Beaujean, Bobeth, van Dyk '13Horgan et al. '13
Altmannshofer & Straub '15
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
II. Anomalies in B → K(*) μμ / ee [LHCb]
Last but not least, the most interesting effect in b → sll transitions the 2.6σ deviation from the SM observed in the LFU ratio
∫ dΓ(B+ → K+μμ)
∫ dΓ(B+ → K+ee)
[1-6] GeV2
RK =
Negligible th. error → clean test of LFU (in neutral currents)
Bordone et al. work in prog.
RK = 1 ± O(1%)
This anomaly is perfectly described assuming NP only in b→sμμ [and not in b→see] consistently with the various b→sμμ anomalies
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Speculations on the breaking of LFU
(Some of) these recent results have stimulated a lot of theoretical activity.
Most interesting aspect: possible breaking of LFU, both in charged currents (b → cτν vs. b → cμν) and in neutral currents (b → sμμ vs. b → see)
A few general messages:
LFU is not a fundamental symmetry of the SM Lagrangian (accidental symmetry in the gauge sector, broken by Yukawas)
LFU tests at the Z peak are not too stringent (→ gauge sector)
Most stringent tests of LFU involve only 1st-2nd gen. quarks & leptons
→ Natural to conceive NP models where LFU is violated more in processes with 3rd gen. quarks (↔ hierarchy in Yukawa coupl.)
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
+ many others...
(Some of) these recent results have stimulated a lot of theoretical activity:
...but till last summer most attempts focused only on one set of anomalies (either charged or neutral currents)
What I will discuss next are some general considerations in trying to describe both these effect within simplified (rather general) semi-dynamical models.
Speculations on the breaking of LFU
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Anomalies are seen only in semi-leptonic (quark×lepton) operators
RR and scalar currents disfavored → LL current-current operators
Necessity of at least one SU(2)L-triplet effective operator ( + maybe a singlet one):
Bhattacharya et al. '14Alonso, Grinstein, Camalich '15Greljo, GI, Marzocca '15
EFT-type considerations:
Large coupling (competing with SM tree-level ) in bc (=33CKM) → l3 ν3 Small non-vanishing coupling (competing with SM FCNC) in bs → l2 l2
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Anomalies are seen only in semi-leptonic (quark×lepton) operators
RR and scalar currents disfavored → LL current-current operators
Necessity of at least one SU(2)L-triplet effective operator ( + maybe a singlet one):
EFT-type considerations:
QL
QL
LL
LL
LQ current
LL currentQQ current
Two natural classes of mediators, giving rise to different correlations among quark×lepton, (evidence) and quark×quark + lepton×lepton (bounds)
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Bhattacharya et al. '14Alonso, Grinstein, Camalich '15Greljo, GI, Marzocca '15
Anomalies are seen only in semi-leptonic (quark×lepton) operators
RR and scalar currents disfavored → LL current-current operators
Necessity of at least one SU(2)L-triplet effective operator ( + maybe a singlet one):
EFT-type considerations:
Large coupling (competing with SM tree-level ) in bc (=33CKM) → l3 ν3 Small non-vanishing coupling (competing with SM FCNC) in bs → l2 l2Two natural classes of mediators, giving rise to different correlations among quark×lepton, (evidence) and quark×quark + lepton×lepton (bounds)
+ small corrections for 2nd (& 1st) generations
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Bhattacharya et al. '14Alonso, Grinstein, Camalich '15Greljo, GI, Marzocca '15
→ fits well with the idea of approximate U(2)n flavor symmetry
I. From R(D*) & R(D) data [Γ(b → cτν)/Γ(b → cμν)] →
Λ2
General consequences in charged currents:
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
II. In principle, it should be possible to get a strong bound on the sub-leading leptonic coupling (λμμ) from Γ(b → cμν)/Γ(b → ceν), but surprisingly it is not so stringent (|λμμ| < 0.1) → no dedicated studies @ B-facotries ! ~
I. From R(D*) & R(D) data [Γ(b → cτν)/Γ(b → cμν)] →
Λ2
General consequences in charged currents:
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
II. In principle, it should be possible to get a strong bound on the sub-leading leptonic coupling (λμμ) from Γ(b → cμν)/Γ(b → ceν), but surprisingly it is not so stringent (|λμμ| < 0.1) → no dedicated studies @ B-facotries ! ~
I. From R(D*) & R(D) data [Γ(b → cτν)/Γ(b → cμν)] →
III. Even if it is hard to quantify, this breaking of LFU in c.c could decrease the (old) tension between exclusive & inclusive determinations of |Vub| & |Vcb|:
B → Xc,u τuν
μνν
Irreducible bkg. for the inclusive meas. subtracted (at present) assuming SM-like Γ(B → Xc,uτν)
if Γ(B → Xc,uτν) is enhanced
over the SM → |Vc(u)b|incl. are over estimated
Λ2
General consequences in charged currents:
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Main assumptions:
Non-Universal flavor structure of the currents → mainly 3rd generations
We assume the effective triplet operator is the result of integrating-out a heavy triplet of vector bosons (W', Z') coupled to a single current:
Greljo, GI, Marzocca '15
A simplified dynamical model:
→ Coupling to 3rd generations not suppressed [dynamical assumption]
→ Coupling to light generations controlled by small U(2)q × U(2)l breaking spurions related to sub-leading terms in the Yukawa couplings
down-typemass basis
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
+
several constraints:
R(D*)R(D)RK P5'(B → K*μμ)
B(B → Kνν) ΔMBs , ΔMBd
CPV(D-D)Γ(B → Xμν)/Γ(B → Xeν)τ → 3μ Γ(τ → μνν)/Γ(τ → eνν)
Overall good fit of low-energy data (non-trivial given tight constraints from ΔF=2 & LFV)
5 free parameters:
Best fit point:
(flavor structure of the sub-leading terms not really probed)
A simplified dynamical model → low-energy global fit:
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
A simplified dynamical model → low-energy global fit:
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
… and gives several clear predictions for future low-energy data:
b → c(u) lν
ℒeff works well...
b → s μμ
b → s ττ
b → s νν
, but overall size of the anom. should decrease
|NP| ~ |SM| → large enhancement (~ BR×4) or strong suppr.
~ ± 50% deviation from SM in the rate
Meson mixing
τ decays
~ 10% deviations from SM both in ΔMBs & ΔMBd
τ → 3μ not far from present exp. bound
BR(B→D*τν)/BRSM = BR(B→Dτν)/BRSM = BR(Λb → Λcτν)/BRSM
= … = BR(Bu → τν)/BRSM Rμ/e(X) ~ 10% Rτ/μ(X)
A simplified dynamical model → further low-energy tests:
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The dynamical model
W' and Z' resonances in the mass range:
Strong constraint on gH from e.w. precisions tests:
The “heavy vector triplet” eff. Lagrangian [Pappadopulo, Tham, Torre, Wulzer, '14]in a rather peculiar parameter range:
≈ 0.3 < 0.01~
A simplified dynamical model → high-energy constraints:
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The heavy vectors are produced mainly from 3rd gen. quarks (bb → Z', bc → W' ) and decay mainly in 3rd generations quarks or leptons (Z' → ττ,bb,tt, W' →tb, τν)
The only really stringent constraint comes from Z' → ττ
Not a very easy signature...
A simplified dynamical model → high-energy constraints:
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
The heavy vectors are produced mainly from 3rd gen. quarks (bb → Z', bc → W' ) and decay mainly in 3rd generations quarks or leptons (Z' → ττ,bb,tt, W' →tb, τν)
The only really stringent constraint comes from Z' → ττ
Minimal version of the model(no exotic decay channels)
ruled out by direct searches
Not a very easy signature...
A simplified dynamical model → high-energy constraints:
Greljo, GI, Marzocca '15
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
N.B.: while the low-energy consequences are almost independent from the structure of the underlying dynamical model, the high-energy consequences can be very different.
For instance, choosing the LQ mediator, we have a perfect candidate also for the mediator of the “S(750)”→γγ,gg effective couplings...
A simplified dynamical model → high-energy constraints:
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
QL
QL
LL
LL
LQ current
LL currentQQ current
Conclusions
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Conclusions
We entered in a very special era in particle physics: the SM is a successful theory that has no intrinsic energy limitations.
While waiting for possible clear clues for physics beyond the SM from high-energy experiments, the key (and difficult) question we face is: what determines the precise values of SM parameters?[“anarchy + anthropic selection” vs. “new symmetries”]
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016
Conclusions
We entered in a very special era in particle physics: the SM is a successful theory that has no intrinsic energy limitations.
While waiting for possible clear clues for physics beyond the SM from high-energy experiments, the key (and difficult) question we face is: what determines the precise values of SM parameters?[“anarchy + anthropic selection” vs. “new symmetries”]
In this perspective, (some of) the anomalies that are emerging both at high-pT and in flavor physics could be the first hints of new symmetries...
We cannot exclude the anthropic principle is the right explanation for some of these couplings (e.g. for the cosmological constant), but it is definitely premature to give-up the attempt of finding dynamical explanations for most of them.
G. Isidori – LHC Physics: Higgs and beyond COURSE D'HIVER 2016 du LAL, 17-19 Feb 2016