12. Beyond the Standard Model - University of Cambridge
Transcript of 12. Beyond the Standard Model - University of Cambridge
12. Beyond the Standard ModelParticle and Nuclear Physics
Dr. Tina Potter
Dr. Tina Potter 12. Beyond the Standard Model 1
In this section...
Summary of the Standard Model
Problems with the Standard Model
Neutrino oscillations
Supersymmetry
Dr. Tina Potter 12. Beyond the Standard Model 2
The Standard Model (2012)
Matter: point-like spin 12
Dirac fermions
+ antiparticles
Fermion Charge [e] Mass
1st
gen.
Electron e− −1 0.511 MeV
Electron neutrino νe 0 ∼ 0
Down quark d −1/3 4.8 MeV
Up quark u +2/3 2.3 MeV
2nd
gen.
Muon µ− −1 106 MeV
Muon neutrino νµ 0 ∼ 0
Strange quark s −1/3 95 MeV
Charm quark c +2/3 1.3 GeV
3rd
gen.
Tau τ− −1 1.78 GeV
Tau neutrino ντ 0 ∼ 0
Bottom quark b −1/3 4.7 GeV
Top quark t +2/3 173 GeV
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The Standard Model (2012)Forces: mediated by spin 1 bosons
Force Particle Mass
Electromagnetic Photon γ 0
Strong 8 gluons g 0
Weak (CC) W± 80.4 GeV
Weak (NC) Z 91.2 GeV
The Standard Model also predicts the existence of a spin-0Higgs boson which gives all particles their masses via itsinteractions. Evidence from LHC confirms this, withmH ∼ 125 GeV.
The Standard Model successfully describes all existing particle physics data,with the exception of one
⇒ Neutrino Oscillations ⇒ Neutrinos have mass
In the SM, neutrinos are treated as massless; right-handed states do notexist ⇒ indication of physics Beyond the Standard Model
Dr. Tina Potter 12. Beyond the Standard Model 4
Problems with the Standard ModelThe Standard Model successfully describes all existing particle physics data(though question marks over the neutrino sector).
But: many (too many?) input parameters:Quark and lepton massesQuark chargeCouplings αEM, sin2 θW , αs
Quark (+ neutrino) generation mixing – VCKM
and: many unanswered questions:Why so many free parameters?Why only three generations of quarks and leptons?Where does mass come from? (Higgs boson probably OK)Why is the neutrino mass so small and the top quark mass so large?Why are the charges of the p and e identical?What is responsible for the observed matter-antimatter asymmetry?How can we include gravity?
etcDr. Tina Potter 12. Beyond the Standard Model 5
Beyond the Standard Model – further unification??
Grand Unification Theories (GUTs) aim to unite the strong interaction withthe electroweak interaction. Underpins many ideas about physics beyond theStandard Model.The strength of the interactions depends on energy:
Suggests unification of all forces at ∼ 1015 GeV?Strength of Gravity only significant at the Planck Mass ∼ 1019 GeV
Dr. Tina Potter 12. Beyond the Standard Model 6
Neutrino OscillationsIn 1998 the Super-Kamiokande experiment announcedconvincing evidence for neutrino oscillations implyingthat neutrinos have mass.
π → µνµ↪→ eνµνe
ExpectN(νµ)
N(νe)∼ 2
Super-Kamiokande results indicate a deficit of νµ fromthe upwards direction. Upward neutrinos createdfurther away from the detector.
Interpreted as νµ→ ντ oscillationsImplies neutrino mixing and neutrinos have mass
Dr. Tina Potter 12. Beyond the Standard Model 7
Detecting NeutrinosNeutrinos are detected by observing the lepton produced in charged currentinteractions with nuclei. e.g. νe + N → e− + X νµ + N → µ+ + XSize Matters:
Neutrino cross-sections on nucleons are tiny; ∼ 10−42(Eν/ GeV)m2
Neutrino mean free path in water ∼ light-years.
Require very large mass, cheap and simple detectors.
Water Cerenkov detection
Cerenkov radiationLight is emitted when a charged particle traverses a dielectric medium
A coherent wavefront forms when the velocity of a charged particle exceeds c/n (n =
refractive index)
Cerenkov radiation is emitted in a cone i.e. at fixed angle with respect to the particle.
cos θC =c
nv=
1
nβ
Dr. Tina Potter 12. Beyond the Standard Model 8
Super-Kamiokande
Super-Kamiokande is a Water Cerenkov detector sited in Kamioka, Japan
50, 000 tons of water
Surrounded by 11, 146 × 50 cm diameter, photo-multiplier tubes
Dr. Tina Potter 12. Beyond the Standard Model 9
Super-Kamiokande Examples of events
νµ + N → µ− + X νe + N → e− + X
Dr. Tina Potter 12. Beyond the Standard Model 10
Super-Kamiokande ν deficit
Expect
Isotropic (flat)distributions in cos θN(νµ) ∼ 2N(νe)
Observe
Deficit of νµ from belowWhereas νe look as expected
Interpretation
νµ→ ντ oscillations⇒ neutrinos have mass
e-like
μ-like
No oscillationsWith oscillationsData
Dr. Tina Potter 12. Beyond the Standard Model 11
Neutrino MixingThe quark states which take part in the weak interaction (d ′, s ′) are related tothe flavour (mass) states (d , s)
Weak Eigenstates(d ′
s ′
)=
(cos θC sin θC− sin θC cos θC
)(d
s
)Mass Eigenstates
Cabibbo angle θC ∼ 13◦
Suppose the same thing happens for neutrinos. Consider only the first twogenerations for simplicity.
Weak Eigenstates= flavour eigenstates
(νeνµ
)=
(cos θ sin θ− sin θ cos θ
)(ν1
ν2
)Mass Eigenstates
Mixing angle θ
e.g. in π+ decay produce µ+ and νµ i.e. the neutrino state that couples to theweak interaction.
The νµ corresponds to a linear combinationof the states with definite mass, ν1 and ν2
νe = +ν1 cos θ + ν2 sin θ
νµ = −ν1 sin θ + ν2 cos θ
or expressing the mass eigenstatesin terms of the weak eigenstates
ν1 = +νe cos θ − νµ sin θ
ν2 = +νe sin θ + νµ cos θDr. Tina Potter 12. Beyond the Standard Model 12
Neutrino Mixing
Dr. Tina Potter 12. Beyond the Standard Model 13
Neutrino Mixing
Dr. Tina Potter 12. Beyond the Standard Model 13
Neutrino Mixing
Dr. Tina Potter 12. Beyond the Standard Model 13
Neutrino Mixing
Suppose a muon neutrino with momentum ~p is produced in a weak decay, e.g.π+ → µ+νµ
At t = 0, the wavefunctionψ(~p, t = 0) = νµ(~p) = ν2(~p) cos θ − ν1(~p) sin θ
The time evolution of ν1 and ν2 will be different if they have different masses
ν1(~p, t) = ν1(~p)e−iE1t ; ν2(~p, t) = ν2(~p)e−iE2t
After time t, state will in general be a mixture of νe and νµψ(~p, t) = ν2(~p)e−iE2t cos θ − ν1(~p)e−iE1t sin θ
= [νe(~p) sin θ + νµ(~p) cos θ] e−iE2t cos θ − [νe(~p) cos θ − νµ(~p) sin θ] e−iE1t sin θ
= νµ(~p)[cos2 θe−iE2t + sin2 θe−iE1t
]+ νe(~p)
[sin θ cos θ
(e−iE2t − e−iE1t
)]= cµνµ(~p) + ceνe(~p)
Dr. Tina Potter 12. Beyond the Standard Model 13
Neutrino MixingProbability of oscillating into νe
P(νe) = |ce|2 =∣∣sin θ cos θ
(e−iE2t − e−iE1t
)∣∣2=
1
4sin2 2θ
(e−iE2t − e−iE1t
) (eiE2t − eiE1t
)=
1
4sin2 2θ
(2− ei(E2−E1)t − e−i(E2−E1)t
)= sin2 2θ sin2
[(E2 − E1)t
2
]
But E =√~p 2 + m2 = ~p
√1 +
m2
~p 2∼ ~p +
m2
2~pfor m� E
1 + x ∼ (1 + x/2)2
when x is small, can ignore x2 term
⇒ E2(~p)− E1(~p) ∼ m22 −m2
1
2~p∼ m2
2 −m21
2E
⇒ P(νµ → νe) = sin2 2θ sin2[
(m22 −m2
1)t
4E
]Dr. Tina Potter 12. Beyond the Standard Model 14
Neutrino MixingFor νµ→ ντ P(νµ → ντ) = sin2 2θ sin2
[(m2
3 −m22)t
4E
]= sin2 2θ sin2
[1.27∆m2L
Eν
]where L is the distance travelled in km,
∆m2 = m23 −m2
2 is the mass difference in ( eV)2
and Eν is the neutrino energy in GeV.
Interpretation of Super-Kamiokande ResultsFor E (νµ) = 1 GeV (typical of atmospheric neutrinos)
Results are consistent with νµ → ντ oscillations:
|m23 −m2
2| ∼ 2.5× 10−3 eV2; sin2 2θ ∼ 1Dr. Tina Potter 12. Beyond the Standard Model 15
Neutrino Mixing – Comments
Neutrinos almost certainly have mass
Neutrino oscillation only sensitive to mass differences
More evidence for neutrino oscillationsSolar neutrinos (SNO experiment)Reactor neutrinos (KamLand)
suggest |m22 −m2
1| ∼ 8× 10−5 eV2.
More recent experiments use neutrino beams from accelerators or reactors;observe energy spectrum of neutrinos at a distant detector.
At fixed L, observation of the values of Eν at which minima/maxima areseen determines ∆m2, while depth of minima determine sin2 2θ.
Note all these experiments only tell us about mass differences.
Best constraint on absolute mass comes from the end point in Tritiumβ-decay, m(νe) < 2 eV.
Dr. Tina Potter 12. Beyond the Standard Model 16
Three-flavour oscillationsThis whole framework can be generalised...
νeνµντ
= UPNMS
ν1
ν2
ν3
where UPNMS =
1 0 0
0 c23 s230 −s23 c23
c12 0 s13e−iδ
0 1 0
−s23eiδ 0 c13
c12 s12 0
−s12 c12 0
0 1
defining cos θ12 = c12 etc.
This is an active field!Current status...
sin2 θ12 = 0.304± 0.014
sin2 θ23 = 0.51± 0.06
sin2 θ13 = 0.0219± 0.0012
Dr. Tina Potter 12. Beyond the Standard Model 17
Supersymmetry (SUSY)A significant problem is to explain why the Higgs boson is so light.
The effect of loop corrections on the Higgs mass should be to
drag it up to the highest energy scale in the problem (i.e.
unification, or Planck mass).
f
f
H H
One attractive solution is to introduce a new space-time symmetry, “supersymmetry”
which links fermions and bosons (the only way to extend the Poincare symmetry of special relativity
and respect quantum field theory.)
Each fermion has a boson partner, and vice versa, with the same couplings. Boson and
fermion loops contribute with opposite sign, giving a natural cancellation in their effect on
the Higgs mass. f
f
H H
f
f
H H+
Must be a broken symmetry, because we clearly don’t see bosons and fermions of the
same mass.
However, this doubles the particle content of the model, without any direct evidence (yet),
and introduces lots of new unknown parameters.
Dr. Tina Potter 12. Beyond the Standard Model 18
The Supersymmetric Standard Model
SM : W±, W 0, Bmixing−−−→ W±, Z , γ
SUSY : H0u , H
0d , W
0, B0 mixing−−−→ χ01, χ
02, χ
03, χ
04
H+u , H
−d , W
+, W− mixing−−−→ χ±1 , χ±2
Dr. Tina Potter 12. Beyond the Standard Model 19
SUSY and UnificationIn the Standard Model, the interaction strengths are not quite unified atvery high energy.Add SUSY, the running of the couplings is modified, because sparticleloops contribute as well as particle loops.Details depend on the version of SUSY, but in general unification muchimproved.
Dr. Tina Potter 12. Beyond the Standard Model 20
SUSY and cosmology
SUSY, or any unified theory, tends to have potential problems with explaining the
non-observation of proton decay.
For this reason, many versions of SUSY introduce a conserved quantity “R-parity”, which
means that sparticles have to be produced in pairs.
A consequence is that the lightest sparticle would have to be stable. In many scenarios
this would be a “neutralino” χ01 (a mixture of neutral “gauginos” and “Higgsinos”).
Cosmologists tell us that ∼ 25% of the mass in the
universe is in the form of “dark matter”, which interacts
gravitationally, but otherwise only weakly.
The lightest sparticle could be a candidate for the
“WIMPs” (Weakly Interacting Massive Particles) which
could comprise dark matter.
68.3% Dark Energy
26.8% Dark Matter
4.9% Atoms
? ??
So there are several different reasons why SUSY is attractive.
Dr. Tina Potter 12. Beyond the Standard Model 21
However, no sign of supersymmetry yet...On general grounds, some sparticles ought to be seen at energies around 1 TeVor lower. So LHC ought to be able to see them, especially squarks+gluinos(high σ @LHC).
Model e, µ, τ, γ Jets EmissT
∫L dt[fb−1] Mass limit Reference
Incl
usiv
eS
earc
hes
3rdge
n.g
med
.3rd
gen.
squa
rks
dire
ctpr
oduc
tion
EW
dire
ctLo
ng-li
ved
part
icle
sR
PV
Other
qq, q→qχ01 0 2-6 jets Yes 36.1 m(χ0
1)<200 GeV, m(1st gen. q)=m(2nd gen. q) 1712.023321.57 TeVq
qq, q→qχ01 (compressed) mono-jet 1-3 jets Yes 36.1 m(q)-m(χ0
1)<5 GeV 1711.03301710 GeVq
gg, g→qqχ01 0 2-6 jets Yes 36.1 m(χ0
1)<200 GeV 1712.023322.02 TeVg
gg, g→qqχ±1→qqW±χ01 0 2-6 jets Yes 36.1 m(χ0
1)<200 GeV, m(χ±)=0.5(m(χ01)+m(g)) 1712.023322.01 TeVg
gg, g→qq(ℓℓ)χ01
ee, µµ 2 jets Yes 14.7 m(χ01)<300 GeV, 1611.057911.7 TeVg
gg, g→qq(ℓℓ/νν)χ01 3 e, µ 4 jets - 36.1 m(χ0
1)=0 GeV 1706.037311.87 TeVg
gg, g→qqWZχ01 0 7-11 jets Yes 36.1 m(χ0
1) <400 GeV 1708.027941.8 TeVg
GMSB (ℓ NLSP) 1-2 τ + 0-1 ℓ 0-2 jets Yes 3.2 1607.059792.0 TeVgGGM (bino NLSP) 2 γ - Yes 36.1 cτ(NLSP)<0.1 mm ATLAS-CONF-2017-0802.15 TeVgGGM (higgsino-bino NLSP) γ 2 jets Yes 36.1 m(χ0
1)=1700 GeV, cτ(NLSP)<0.1 mm, µ>0 ATLAS-CONF-2017-0802.05 TeVg
Gravitino LSP 0 mono-jet Yes 20.3 m(G)>1.8 × 10−4 eV, m(g)=m(q)=1.5 TeV 1502.01518F1/2 scale 865 GeV
gg, g→bbχ01 0 3 b Yes 36.1 m(χ0
1)<600 GeV 1711.019011.92 TeVg
gg, g→ttχ01 0-1 e, µ 3 b Yes 36.1 m(χ0
1)<200 GeV 1711.019011.97 TeVg
b1b1, b1→bχ01 0 2 b Yes 36.1 m(χ0
1)<420 GeV 1708.09266950 GeVb1
b1b1, b1→tχ±1 2 e, µ (SS) 1 b Yes 36.1 m(χ01)<200 GeV, m(χ±1 )= m(χ0
1)+100 GeV 1706.03731275-700 GeVb1
t1 t1, t1→bχ±1 0-2 e, µ 1-2 b Yes 4.7/13.3 m(χ±1 ) = 2m(χ01), m(χ0
1)=55 GeV 1209.2102, ATLAS-CONF-2016-077t1 117-170 GeV 200-720 GeVt1
t1 t1, t1→Wbχ01 or tχ0
1 0-2 e, µ 0-2 jets/1-2 b Yes 20.3/36.1 m(χ01)=1 GeV 1506.08616, 1709.04183, 1711.11520t1 90-198 GeV 0.195-1.0 TeVt1
t1 t1, t1→cχ01 0 mono-jet Yes 36.1 m(t1)-m(χ0
1)=5 GeV 1711.0330190-430 GeVt1
t1 t1(natural GMSB) 2 e, µ (Z) 1 b Yes 20.3 m(χ01)>150 GeV 1403.5222t1 150-600 GeV
t2 t2, t2→t1 + Z 3 e, µ (Z) 1 b Yes 36.1 m(χ01)=0 GeV 1706.03986290-790 GeVt2
t2 t2, t2→t1 + h 1-2 e, µ 4 b Yes 36.1 m(χ01)=0 GeV 1706.03986320-880 GeVt2
ℓL,R ℓL,R, ℓ→ℓχ01 2 e, µ 0 Yes 36.1 m(χ0
1)=0 ATLAS-CONF-2017-03990-500 GeVℓ
χ+1 χ−1 , χ+1→ℓν(ℓν) 2 e, µ 0 Yes 36.1 m(χ0
1)=0, m(ℓ, ν)=0.5(m(χ±1 )+m(χ01 )) ATLAS-CONF-2017-039750 GeVχ±
1
χ±1 χ∓1 /χ
02, χ+1→τν(τν), χ0
2→ττ(νν) 2 τ - Yes 36.1 m(χ01)=0, m(τ, ν)=0.5(m(χ±1 )+m(χ0
1)) 1708.07875760 GeVχ±1
χ±1 χ02→ℓLνℓLℓ(νν), ℓνℓLℓ(νν) 3 e, µ 0 Yes 36.1 m(χ±1 )=m(χ0
2), m(χ01)=0, m(ℓ, ν)=0.5(m(χ±1 )+m(χ0
1)) ATLAS-CONF-2017-0391.13 TeVχ±1 , χ
02
χ±1 χ02→Wχ0
1Zχ01 2-3 e, µ 0-2 jets Yes 36.1 m(χ±1 )=m(χ0
2), m(χ01)=0, ℓ decoupled ATLAS-CONF-2017-039580 GeVχ±
1 , χ02
χ±1 χ02→Wχ0
1h χ01, h→bb/WW/ττ/γγ e, µ, γ 0-2 b Yes 20.3 m(χ±1 )=m(χ0
2), m(χ01)=0, ℓ decoupled 1501.07110χ±
1 , χ02 270 GeV
χ02χ
03, χ0
2,3 →ℓRℓ 4 e, µ 0 Yes 20.3 m(χ02)=m(χ0
3), m(χ01)=0, m(ℓ, ν)=0.5(m(χ0
2)+m(χ01)) 1405.5086χ0
2,3 635 GeVGGM (wino NLSP) weak prod., χ0
1→γG 1 e, µ + γ - Yes 20.3 cτ<1 mm 1507.05493W 115-370 GeVGGM (bino NLSP) weak prod., χ0
1→γG 2 γ - Yes 36.1 cτ<1 mm ATLAS-CONF-2017-0801.06 TeVW
Direct χ+1 χ−1 prod., long-lived χ±1 Disapp. trk 1 jet Yes 36.1 m(χ±1 )-m(χ0
1)∼160 MeV, τ(χ±1 )=0.2 ns 1712.02118460 GeVχ±1
Direct χ+1 χ−1 prod., long-lived χ±1 dE/dx trk - Yes 18.4 m(χ±1 )-m(χ0
1)∼160 MeV, τ(χ±1 )<15 ns 1506.05332χ±1 495 GeV
Stable, stopped g R-hadron 0 1-5 jets Yes 27.9 m(χ01)=100 GeV, 10 µs<τ(g)<1000 s 1310.6584g 850 GeV
Stable g R-hadron trk - - 3.2 1606.051291.58 TeVgMetastable g R-hadron dE/dx trk - - 3.2 m(χ0
1)=100 GeV, τ>10 ns 1604.045201.57 TeVg
Metastable g R-hadron, g→qqχ01 displ. vtx - Yes 32.8 τ(g)=0.17 ns, m(χ0
1) = 100 GeV 1710.049012.37 TeVg
GMSB, stable τ, χ01→τ(e, µ)+τ(e, µ) 1-2 µ - - 19.1 10<tanβ<50 1411.6795χ0
1 537 GeVGMSB, χ0
1→γG, long-lived χ01 2 γ - Yes 20.3 1<τ(χ0
1)<3 ns, SPS8 model 1409.5542χ01 440 GeV
gg, χ01→eeν/eµν/µµν displ. ee/eµ/µµ - - 20.3 7 <cτ(χ0
1)< 740 mm, m(g)=1.3 TeV 1504.05162χ01 1.0 TeV
LFV pp→ντ + X, ντ→eµ/eτ/µτ eµ,eτ,µτ - - 3.2 λ′311=0.11, λ132/133/233=0.07 1607.080791.9 TeVντ
Bilinear RPV CMSSM 2 e, µ (SS) 0-3 b Yes 20.3 m(q)=m(g), cτLS P<1 mm 1404.2500q, g 1.45 TeVχ+1 χ
−1 , χ+1→Wχ0
1, χ01→eeν, eµν, µµν 4 e, µ - Yes 13.3 m(χ0
1)>400GeV, λ12k,0 (k = 1, 2) ATLAS-CONF-2016-0751.14 TeVχ±1
χ+1 χ−1 , χ+1→Wχ0
1, χ01→ττνe, eτντ 3 e, µ + τ - Yes 20.3 m(χ0
1)>0.2×m(χ±1 ), λ133,0 1405.5086χ±1 450 GeV
gg, g→qqχ01, χ0
1 → qqq 0 4-5 large-R jets - 36.1 m(χ01)=1075 GeV SUSY-2016-221.875 TeVg
gg, g→ttχ01, χ0
1 → qqq 1 e, µ 8-10 jets/0-4 b - 36.1 m(χ01)= 1 TeV, λ112,0 1704.084932.1 TeVg
gg, g→t1t, t1→bs 1 e, µ 8-10 jets/0-4 b - 36.1 m(t1)= 1 TeV, λ323,0 1704.084931.65 TeVg
t1 t1, t1→bs 0 2 jets + 2 b - 36.7 1710.07171100-470 GeVt1 480-610 GeVt1
t1 t1, t1→bℓ 2 e, µ 2 b - 36.1 BR(t1→be/µ)>20% 1710.055440.4-1.45 TeVt1
Scalar charm, c→cχ01 0 2 c Yes 20.3 m(χ0
1)<200 GeV 1501.01325c 510 GeV
Mass scale [TeV]10−1 1
√s = 7, 8 TeV
√s = 13 TeV
ATLAS SUSY Searches* - 95% CL Lower LimitsDecember 2017
ATLAS Preliminary√s = 7, 8, 13 TeV
*Only a selection of the available mass limits on new states orphenomena is shown. Many of the limits are based onsimplified models, c.f. refs. for the assumptions made.
Dr. Tina Potter 12. Beyond the Standard Model 22
Signs of anything else?
2015: search for new boson
decaying to two photons,
X → γγ.
Bump at 750 GeV...
In both experiments...
200 400 600 800 1000 1200 1400 1600 1800 2000
Even
ts /
20 G
eV
1−10
1
10
210
310
410 PreliminaryATLAS
Spin-2 Selection-1 = 13 TeV, 3.2 fbs
Data
Background-only fit
[GeV]γγm200 400 600 800 1000 1200 1400 1600 1800 2000
Dat
a - f
itted
bac
kgro
und
10−
5−05
1015
Eve
nts
/ ( 2
0 G
eV )
1
10
210
Data
Fit model
σ 1 ±σ 2 ±
EBEB
(GeV)γ γm400 600 800 1000 1200 1400 1600
stat
σ(d
ata-
fit)/
-2
0
2
(13 TeV, 3.8T)-12.7 fbCMS Preliminary
ATLAS 750 GeV local excess ∼ 3.5σ (global drops to 1.8σ) evidence,
CMS 750 GeV local excess ∼ 2.9σ (global drops to 1σ) not discovery
Revisited 8 TeV dataset and performed same analysis. Results are consistent...
What could this be?Extra dimensions: excitations of gravitational field in small, curled up, warped extra dimension
– gives “towers” of spin-2 resonances, gravitons.
Extended Higgs sector: add a second Higgs doublet to the SM
– gives 5 (pseudo-)scalar Higgs bosons (lightest is the 126 GeV Higgs).
Sadly, analysis of larger 2016 dataset showed no such resonance– a statistical fluctuation
Dr. Tina Potter 12. Beyond the Standard Model 23
Follow the results from LHC yourself!
http://atlas.chhttp://cms.web.cern.chhttp://lhcb-public.web.cern.ch/lhcb-public/
Dr. Tina Potter 12. Beyond the Standard Model 24
Summary
Over the past 40 years our understanding of the fundamental particles andforces of nature has changed beyond recognition.
The Standard Model of particle physics is an enormous success. It has beentested to very high precision and can model all experimental observationsso far.
The Higgs “hole” is now becoming closed, though some other aspects ofthe SM are not quite yet under as much experimental “control” as onemight wish for (the neutrino sector, the CKM matrix, etc).
Good reasons to expect that the next few years will bring many more(un)expected surprises (more Higgs or gauge bosons, SUSY?).
Up next...Section 13: Nuclear Physics, Basic Nuclear Properties
Dr. Tina Potter 12. Beyond the Standard Model 25