Precision Measurements & Their Sensitivity to New Physicspgl/talks/FCC-ee.pdf · 2016. 2. 10. ·...

Precision Measurements & Their Sensitivity to New Physics

• Precision experiments

• Implications for the SM andbeyond

• Paradigms and realizations

• The FCC-ee

Physics Behind Precision, CERN (2/2/16) Paul Langacker (IAS)

Precision Physics: Past and Present

• Weak neutral current (ν scattering; APV; polarized e−; e+e−; · · · )

• Z, W (Spp̄S, LEP, SLC, Tevatron, LHC)

• Higgs

• Triple/quartic gauge vertices; WLWL→WLWL

• Weak charged current (β, µ, · · · decay; CP violation; unitarity triangle)

• QED (classic tests; gµ − 2; µ Lamb shift (proton radius))

• t physics

• EDMs

• Flavor physics, rare decays, FCNC, neutrinos

• Precision cosmology


5

were individually corrected for the small energy depen-dence of the γ-Z box diagram calculated in Ref. [32]. Theeven smaller additional correction for the Q2 dependenceof the γ-Z box diagram above Q2=0.025 (GeV/c)

2was

included using the prescription provided in Ref. [27] withEM form factors from Ref. [23]. The small energy andQ2 dependent uncertainties associated with the predictedcorrections were folded into the systematic error of eachpoint. The effect of either doubling, or not including thenominally forward angle γ-Z radiative correction for the6 larger angle data > 21◦ used in the fit resulted in achange in Qp

W (PVES) < ± 0.0006.The effects of varying the maximum Q2 or θ of the

data included in the fit were studied and found to besmall for data above Q2∼0.25 (GeV/c)2. Truncating thedata set at lower Q2 values tends to destabilize the fit,and enhances the sensitivity to the underlying statisticalfluctuations in the data set, as reported in [22]. The effectof varying the dipole mass in the strange and axial formfactors was also studied and found to be small, with avariation of < ± 0.001 in Qp

W for 0.7 (GeV/c)2 < λ2 <2 (GeV/c)2. Smaller values of λ are disfavored by latticeQCD calculations of strange form factors [53], and theresults quickly plateau for larger values.

▲

▲

▲

0.0 0.1 0.2 0.3 0.4 0.5 0.60.0

0.1

0.2

0.3

0.4

■

■

■

✖

■

◆ This Experiment■ HAPPEX✖ SAMPLE▲ PVA4● G0 SM (prediction)

◆

Data Rotated to the Forward-Angle Limit

[GeV/c]Q 22

ç

ç

W A

/A

= Q

+

B(

,θ

= 0

)p

0Q

2Q

2

ep

FIG. 2. Global fit result (solid line) presented in the forwardangle limit as reduced asymmetries derived from this mea-surement as well as other PVES experiments up to Q2 = 0.63(GeV/c)2, including proton, helium and deuterium data. Theadditional uncertainty arising from this rotation is indicatedby outer error bars on each point. The yellow shaded regionindicates the uncertainty in the fit. Qp

W is the intercept ofthe fit. The SM prediction [34] is also shown (arrow).

In order to illustrate the 2-dimensional global fit(θ, Q2) in a single dimension (Q2), the angle dependenceof the strange and axial form-factor contributions was re-moved by subtracting

[Acalc(θ, Q

2) − Acalc(0◦, Q2)

]from

the measured asymmetries Aep(θ, Q2), where the calcu-

lated asymmetries Acalc are determined from Eq. 2 usingthe results of the fit. The reduced asymmetries from

this forward angle rotation of all the e⃗p PVES data usedin the global fit are shown in Fig. 2 along with the re-sult of the fit. The intercept of the fit at Q2 = 0 isQp

W (PVES)=0.064 ± 0.012.

The present measurement also constrains the neutral-weak quark couplings. The result of a fit combining themost recent correction [54] to the 133Cs APV result [8],with the world PVES data (including the present mea-surement) is shown in Fig. 3.

0.22

0.24

-0.70 -0.65 -0.60 -0.55 -0.50 -0.45 -0.40

0.18 0.17

0.16

0.15

0.14 0.13

0.12

C1u C1d

C1u

+ C

1d

sin ! |2

-

-

-

-

-

-

-

-

-

0.20

0.26

133Cs APV PVES

Inner Ellipses - 68% CLOuter Ellipses - 95% CL

ZW

FIG. 3. The constraints on the neutral-weak quark couplingconstants C1u − C1d (isovector) and C1u + C1d (isoscalar).The more horizontal (green) APV band (shown at ∆χ2 = 2.3)provides a tight constraint on the isoscalar combination from133Cs data. The more vertical (blue) ellipse represents theglobal fit of the existing Q2 < 0.63 PVES data including thenew result reported here at Q2=0.025 (GeV/c)2. The smaller(red) ellipse near the center of the figure shows the resultobtained by combining the APV and PVES information. TheSM prediction [34] as a function of sin2 θW in the MS schemeis plotted (diagonal black line) with the SM best fit valueindicated by the (black) point at sin2 θW =0.23116.

The neutral weak couplings determined from this com-bined fit are C1u=−0.1835 ± 0.0054 and C1d=0.3355 ±0.0050, with a correlation coefficient -0.980. The cou-plings can be used in turn to obtain a value for Qp

W ,Qp

W (PVES+APV) = −2(2C1u +C1d)=0.063±0.012, vir-tually identical with the result obtained from thePVES results alone. In addition the C1’s canbe combined to extract the neutron’s weak chargeQn

W (PVES+APV)=−2(C1u + 2C1d)=−0.975 ± 0.010.Both Qp

W and QnW are in agreement with the SM val-

ues [34] QpW (SM) = 0.0710 ± 0.0007 and Qn

W (SM) =−0.9890 ± 0.0007.

Prescriptions for determining the mass reach impliedby this result can be found in the literature [2, 6]. Thecommissioning data reported here comprise 4% of the

10

10 2

10 3

10 4

10 5

0 20 40 60 80 100 120 140 160 180 200 220

Centre-of-mass energy (GeV)

Cro

ss-s

ecti

on (

pb)

CESRDORIS

PEP

PETRATRISTAN

KEKBPEP-II

SLC

LEP I LEP II

Z

W+W-

e+e−→hadrons


0

10

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30

160 180 200

!s (GeV)

"W

W (

pb

)

YFSWW/RacoonWW

no ZWW vertex (Gentle)

only #e exchange (Gentle)

LEPPRELIMINARY

17/02/2005

QCD αs(Mz) = 0.1185 ± 0.0006

Z pole fit

0.1

0.2

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αs (Q)

1 10 100Q [GeV]

Heavy Quarkonia (NLO)e+e– jets & shapes (res. NNLO)

DIS jets (NLO)

Sept. 2013

Lattice QCD (NNLO)

(N3LO)

τ decays (N3LO)

1000

pp –> jets (NLO)(–)

a

_

_

dm6 K¡sm6 & dm6

ubV

`sin 2(excl. at CL > 0.95)

< 0`sol. w/ cos 2

_

`a

l-0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0

d

0.0

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0.7

excl

uded

are

a ha

s C

L >

0.95

EPS 15

CKMf i t t e r

– 44–

)µBest fit signal strength (

Combined

γγ →H

llll→ (*) ZZ→H

νlν l→ (*) WW→H

ττ →H

bb→W,Z H

H

-0.18+0.21 = 1.33 µ

-0.28+0.33 = 1.55 µ

-0.35+0.40 = 1.43 µ

-0.28+0.31 = 0.99 µ

-0.4+0.5 = 1.4 µ

0.7 ± = 0.2 µ

A1

A1

A1

A1

A2*

A3*

* ATLAS Preliminarynot in combination

** CMS Preliminarynot in combination

0.14 C1± = 0.80 µ

0.27 C1± = 0.77 µ

0.28 C1± = 0.92 µ

0.20 C1± = 0.68 µ

0.41 C1± = 1.10 µ

0.29 C6**± = 0.87 µ

0.62 C1± = 1.15 µ

ATLAS CMS Prel.-1 4.8 fb≤Ldt ∫ = 7 TeV: s -1 5.1 fb≤Ldt ∫ = 7 TeV: s

-1 20.7 fb≤Ldt ∫ = 8 TeV: s -1 19.6 fb≤Ldt ∫ = 8 TeV: s = 125.5 GeVHm = 125.7 GeVHm

-1 0 1 2 -1 0 1 2

Figure 16: The signal strengths µ measuredby the ATLAS experiment from Refs. A1 [119],A2 [132] and A3 [137], and CMS experimentfrom Ref. C1 [123] and C6 [131] in the five prin-cipal channels and their combination. It shouldbe noted that the ATLAS combination only in-cludes the bosonic γγ, ZZ and WW channels.

III.6. Higgs Production in association with top quarks

As discussed in Section II, the coupling of the Higgs particle

to top quarks plays a special role in the electroweak breaking

mechanism and in its possible extensions. Substantial indirect

evidence of this coupling is provided by the compatibility

of observed rates of the Higgs boson in the main discovery

channels as one of the main production processes, the gluon

fusion, is dominated by a top quark loop. Direct evidence of

this coupling at the LHC and the future e+e− colliders will

be mainly available through the ttH final state. The analyses

channels for such complex final states can be separated in four

classes according to the decays of the Higgs boson. In each of

January 9, 2014 16:22


Results of the Precision Program

• Established electroweak SM to first approximationgauge theory (V,A; W,Z); SU(2)× U(1);

fermion reps., chiralities; sin2 θW ; t; ντ required

1398 UGO AMALDI et al. 36

plings e, (u), e;(d), i =I.,R are uniquely determined (Fig.6) by the data in Tables I—III and are in good agreementwith the standard-model predictions.The ve parameters gz, gz are shown in Fig. 7. The

(—)v „e data alone allow four solutions (which dilfer byg ~—g and by gf ~g~ ). The reactor v, e results elim-inate solution C (Ref. 111),while the Los Alamos v, e ex-periment eliminates solutions C and D. The remainingtwo solutions [axial-vector-dominant (A) and vector-dominant (B)] are consistent with all data ". The axial-vector-dominant solution agrees with the standard modeland is shown in Fig. 7(b).Assuming a single Z boson, the e+e data (mainly

the forward-backward asymmetries) are very useful fortesting e-p-~ universality in the axial-vector couplings(the vector couplings are consistent with zero and arenot well determined). Assuming p= 1 and the canonical

1.0

04—

0.2—

O.O—1.0 —0.8 —0.6 —0.4 —0.2C)U

10t i t l I I l I f

0.0

0.8—SU xU e -- 1.0

V

1.0A

0. 2x (b)

O. 6--D

co. ~—-i'.0 ' '.I',f ' )'z '

j'

o.o-,Q)& B--/

——1.0

0.4—

0.2—

pp I I I I

-1.0 —0.8 -0.6 -0.4 —0.2C]„

O.O

FIG. 8. (a) Allowed regions (90% C.L.) in C1„-C]d from theSLAC eD experiment and atomic parity violation. (b) Com-bined fit. Also shown are the predictions of the standard mod-el as a function of sin 0~ and the changes that would be in-duced by extra Z bosons with Mz ——Mz and 0=0. (The Z &2 I

does not contribute to Cl;. )

0. 1

0.0—e & —0.1— 0.

—0.2—SU xU2 1

—0.8 —0,7I I

—0.4 -0.5 —0.2ge

00 ) A

-0.6

FIG. 7. (a) Allowed regions (90% C.L.) for the ve parame-( —)

ters g&—g& for various reactions: v „e (solid lines), reactor v, e(dot-dashed line), and v, e (dashed line). {b) Allowed (axial-vector-dominant) region (A) {90%and 68% C.L.) from the glo-bal fit to all ve data [the second, vector-dominant solution (B)is off scale]. Also shown are the standard-model predictions asa function of sin 0~ and changes that would be induced by ad-ditional Z bosons with Mz ——Mz and 0=—0.

2 1

expression for h zz, a fit to all data yieldsh g~g ——g~g~q ——0.272 +0.015 and h gg ——gag q ——0.232+0.026, very close to the standard-model prediction —,'.For g & ————,', these imply g~& ———0.54+0.03 and

gz ———0.46+0.05, in impressive agreement with univer-sality.The allowed region for the eq couplings C&„and C»

are shown in Fig. 8. These are obtained from a simul-taneous fit of C&„, C&d, C2„, and C2d to the SLAC andatomic parity-violation data. (The pC asymmetries arenot used because they depend on parity-conserving cou-plings as well. ) The agreement of C&„and C,d with thestandard-model prediction is impressive. Cz„and Czdare only weakly constrained and are not displayed. "

F. Additional Z bosons (Refs. 114—116)

Many extensions of the standard-model predict the ex-istence of additional Z bosons. For the simplest case(one extra Z) the physical (mass eigenstate) bosons are

Amaldi et al., Phys.Rev. D36 (1987)

-

-

-

-

-

-

-

-

ì

0.16

0.18

0.20

0.22

0.24

0.26

QWHThL

QWHCsL

Bates eC

SLACeD

Mainze Be

PVES

-0.8 -0.7 -0.6 -0.5 -0.4 -0.30.10

0.12

0.14

0.16

0.18

C1 u-C1 d

C1

u+C

1d


(−12, 0), SM

(0,−12), mirror

(0, 0), topless

(−12,−

12), vector doublet

Schaile and Zerwas, Phys.Rev. D45 (1992)

0.07

0.08

0.09

0.1

0.11

0.12

-0.46 -0.45 -0.44 -0.43 -0.42 -0.41gLb

g Rb

68.3 95.5 99.5 % CL

SM

LEPEWWG


• Established SM at loop level (QED, EW, QCD, mixed)

– Renormalization theory vindicated

– mt, MH successfully predicted

t(b)

t(b)

Z(γ) Z

t

b

W W

H H

– Typeset by FoilTEX – 1

t

W

t

b b

Z

W

t

W

b b

Z



• The top quark prediction

0

40

80

120

160

200

240

1989 1991 1993 1995 1997 1999 2001 2003 2005 2007

Top M

ass (

Ge

V/c

2)

Year

0

50

100

150

200

250

1988 1990 1992 1994 1996 1998

mt [G

eV/c

2 ]

Year

LEP 2494.6 ± 2.7 MeV

m H = 60 – 1000 GeV

αs = 0.123 ± 0.006

m Z = 91 186 ± 2 MeV

100

150

200

250

2480 2490 2500ΓZ [MeV]

mt [

GeV

/c ]2

– Updated from Chris Quigg, Phys.Today (1997), hep-ph/9704332

– Current indirect value: 177.0(2.1) GeV (Erler and Freitas, PDG);direct: 173.21(0.87) GeV (LHC/Tevatron, PDG)


http://arxiv.org/pdf/hep-ph/9704332.pdf

http://pdg.lbl.gov/2015/reviews/rpp2014-rev-standard-model.pdf

http://pdg.lbl.gov

32 10. Electroweak model and constraints on new physics

150 155 160 165 170 175 180 185mt [GeV]

10

20

30

50

100

200

300

500

1000

MH [G

eV]

ΓZ, σhad, Rl, Rq (1σ)Z pole asymmetries (1σ)MW (1σ)direct mt (1σ)direct MHprecision data (90%)

Figure 10.4: Fit result and one-standard-deviation (39.35% for the closed contoursand 68% for the others) uncertainties in MH as a function of mt for various inputs,and the 90% CL region (∆χ2 = 4.605) allowed by all data. αs(MZ) = 0.1185 isassumed except for the fits including the Z lineshape. The width of the horizontaldashed (yellow) band is not visible on the scale of the plot.

account for Rb, which has been measured on the Z peak and off-peak [227] at LEP 1.An average of Rb measurements at LEP 2 at energies between 133 and 207 GeV is 2.1 σ

below the SM prediction, while A(b)FB (LEP 2) is 1.6 σ low [171].

The left-right asymmetry, A0LR = 0.15138 ± 0.00216 [154], based on all hadronic data

from 1992–1998 differs 2.1 σ from the SM expectation of 0.1468 ± 0.0004. The combinedvalue of Aℓ = 0.1513 ± 0.0021 from SLD (using lepton-family universality and includingcorrelations) is also 2.1 σ above the SM prediction; but there is experimental agreementbetween this SLD value and the LEP 1 value, Aℓ = 0.1481 ± 0.0027, obtained from a fit

to A(0,ℓ)FB , Ae(Pτ ), and Aτ (Pτ ), again assuming universality.

The observables in Table 10.4 and Table 10.5, as well as some other less preciseobservables, are used in the global fits described below. In all fits, the errors includefull statistical, systematic, and theoretical uncertainties. The correlations on the LEP 1lineshape and τ polarization, the LEP/SLD heavy flavor observables, the SLD leptonasymmetries, and the ν-e scattering observables, are included. The theoretical correlations

between ∆α(5)had and gµ − 2, and between the charm and bottom quark masses, are also

accounted for.

The data allow a simultaneous determination of MZ , MH , mt, and the strong coupling

αs(MZ). (m̂c, m̂b, and ∆α(3)had are also allowed to float in the fits, subject to the

August 21, 2014 13:18

Erler and Freitas, PDG Gfitter

LEPEWWG



http://project-gfitter.web.cern.ch/project-gfitter/

http://lepewwg.web.cern.ch/LEPEWWG/

• The Z pole watershed: new TeV-scale physics severely constrained

– Nondecoupling (many forms of strong coupling, DSB): several %

– Decoupling (e.g., SUSY): < 1%

• Limits on weak coupling (oblique: EWSB, chiral fermions; Z′, exotics)

-0.004 -0.002 0 0.002 0.0040

1

2

3

4

5

6

x

0.6 0.2

CDFD0LEP 2

MZ’ [TeV]

Zχ

sin θzz’

0.4 00.81

-0.004 -0.002 0 0.002 0.0040

1

2

3

4

5

6

x

CDF

MZ’ [TeV]

Zψ

sin θzz’

00.50.751 0.25

D0LEP 2

-0.008 -0.004 0 0.004 0.0080

1

2

3

4

5

6

x

0 10.40.30.1 0.2 0.5 0.6 0.7 0.8 0.9

CDFD0LEP 2

MZ’ [TeV]

Zη

sin θzz’

-0.004 -0.002 0 0.002 0.0040

1

2

3

4

5

6 x

CDFD0

MZ’ [TeV]

ZI

sin θzz’

0 0.25 0.5 0.75 1

Figure 1: 95% C.L. contours in MZ0 vs. sin ✓ZZ0 for various models. See the text for details.

that the presence of a Z 0 often moves the central value up to the allowed region. Table 6

shows the best fit values and 1� errors for MH when the LEP 2 bound is removed.

Some Z 0 models have a fairly low minimum �2, especially the Z and the ZR. Table 6

shows the �2 minimum of the ZR model about 3 units below the SM value, technically

implying an upper bound on the ZR mass of about 29 TeV at the 90% C.L. This is actually

the reason why we included the ZR in this paper in the first place. Of course, at present

– 12 –

Erler et al: 0906.2435

-0.004 -0.002 0 0.002 0.0040

1

2

3

4

5

6

0.330.7

0.233

CDF

0.466

MZ’ [TeV]

ZS

sin θzz’

0.166 00.9331

-0.004 -0.002 0 0.002 0.0040

1

2

3

4

5

6

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1 0.6 0.3 00.9 0.5

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MZ’ [TeV]

Z N

sin θzz’

-0.004 0 0.0040

1

2

3

4

5

6

x

1 0.5 0

MZ’ [TeV]

Z R

sin θzz’

-0.004 -0.002 0 0.002 0.0040

1

2

3

4

5

6

x

1 0.8 0.4 0

CDF

0.6 0.2

LEP 2

MZ’ [TeV]

ZLR

sin θzz’

Figure 2: 95% C.L. contours in MZ0 vs. sin ✓ZZ0 for various models. See the text for details.

there is little significance to this observation since we have two additional fit parameters

(M 0Z and sin ✓ZZ0) and various parameters for the charges (like the angles ↵ and �) to adjust.

Nevertheless, this is somewhat surprising given that the SM fit is quite good with �2min = 48.0

for 45 e↵ective degrees of freedom. It may be useful to note that the improvement in �2

arises mainly through �had, QW (e), and the e�-DIS observables, where the latter two are of

special interest in view of proposed and approved experiments to be performed at JLab.

– 13 –

10. Electroweak model and constraints on new physics 43

Table 10.9: 95% CL lower mass limits (in GeV) on various extra Z ′ gauge bosons,appearing in models of unification. More general parametrizations are described inRefs. 268 and 271. The EW results [272] from low energy and W and Z bosondata are for Higgs sectors consisting of doublets and singlets only (ρ0 = 1) withunspecified U(1)′ charges. The next two columns show the limits from ATLAS [273]and CMS [274] from the combination of both lepton channels. The CDF [275] andDØ [276] bounds from searches in p̄p → µ+µ− and e+e−, respectively, are listed inthe next two columns, followed by the LEP 2 e+e− → f f̄ bounds [170] (assumingθ = 0). The hadron collider bounds would be moderately weakened if there are openexotic decay channels [277]. The last column shows the 1 σ ranges for MH when itis left unconstrained in the EW fits.

Z ′ EW ATLAS CMS CDF DØ LEP 2 MH

Zχ 1, 141 2, 540 − 930 903 785 171+493− 89

Zψ 147 2, 380 2, 600 917 891 500 97+ 31− 25

Zη 427 2, 440 − 938 923 500 423+577−350

ZLR 998 − − − − 825 804+174− 35

ZS 1, 257 2, 470 − 858 822 − 149+353− 68

ZSM 1, 403 2, 860 2, 960 1, 071 1, 023 1, 760 331+669−246

One well explored type of physics beyond the SM are extra Z ′ bosons [268]. They donot spoil the observed approximate gauge coupling unification, and appear in many GrandUnified Theories (GUTs), models with extra dimensions [258], as well as in dynamicalsymmetry breaking [257] and Little Higgs models [259]. For example, the SO(10) GUTcontains an extra U(1) as can be seen from its maximal subgroup, SU(5) × U(1)χ.Similarly, the E6 GUT contains the subgroup SO(10) × U(1)ψ. The Zψ possesses onlyaxial-vector couplings to the ordinary fermions, and its mass is generally less constrained.The Zη boson is the linear combination

√3/8Zχ −

√5/8Zψ. The ZLR boson occurs in

left-right models with gauge group SU(3)C × SU(2)L × SU(2)R × U(1)B−L ⊂ SO(10), andthe secluded ZS emerges in a supersymmetric bottom-up scenario [269]. The sequentialZSM boson is defined to have the same couplings to fermions as the SM Z boson. Such aboson is not expected in the context of gauge theories unless it has different couplings toexotic fermions than the ordinary Z boson. However, it serves as a useful reference casewhen comparing constraints from various sources. The physical Z ′ boson is in generala superposition of the SM Z and the new boson associated with the extra U(1). Themixing angle θ satisfies,

tan2 θ =M2

Z01

− M2Z

M2Z′ − M2

Z01

,

where MZ01

is the SM value for MZ in the absence of mixing. Note that MZ < MZ01,

and that the SM Z couplings are changed by the mixing. The couplings of the heavier Z ′

August 21, 2014 13:18

Erler and Freitas, PDG

• Hints of new physics? (ALR vs Abb̄FB; gµ − 2; proton radius)


http://arxiv.org/pdf/0906.2435.pdf


• Precise SM parameters

– sin2 θ̂W (M2Z) = 0.23126(5) (PDG)

– αs(MZ) = 0.1193(16) (Z-pole) vs 0.1185(6) (all), (PDG)

– Gauge couplings (consistent with SUSY gauge unification)

Α1-1

Α2-1

Α3-1

Standard Model

0 5 10 15 200

20

40

60

80

log10Q HGeVL

Αi-

1

Α1-1

Α2-1

Α3-1

Supersymmetric Standard Model

MSUSY=MZ

0 5 10 15 200

20

40

60

80

log10Q HGeVL

Αi-

1

– Neutrino counting (2.984(8) light active ν)


The Standard Model

• Spectacularly successful/unsuccessful

• Mathematically consistent

• Describes nature to 10−16 cm

• Higgs discovery(not DSB; but composite/extra dim?, EFT?)

• But, complicated, fine-tuned,families, many parameters

• Missing: dark matter and energy,nB − nB̄, quantum gravity, mν type


The Paradigms

• Naturalness or tuning

• Uniqueness or environment

• Minimality or remnants

naturalness

(TeV physics)

tuning

(landscape?)


Naturalness or Tuning

• ATLAS/CMS/LHCb: no clear sign of supersymmetry, strongdynamics, or other new physics

– 750 GeV diphoton? 2 TeV diboson? B anomalies?

• Higgs-like particle: consistent with elementary Higgs

– SM: rather light (metastable vacuum or new physics below 1011 GeV)

– MSSM: rather heavy (need heavy stop or large mixing)

0 50 100 150 2000

50

100

150

200

Higgs mass Mh in GeV

Top

mas

sM

tin

GeV

Instability

Non

-perturbativity

Stability

Meta-stab

ility

104 106 108 1010 1012 1014 1016 1018

110

120

130

140

150

160

Supersymmetry breaking scale in GeV

Hig

gsm

ass

mh

inG

eV

Predicted range for the Higgs mass

Split SUSY

High-Scale SUSY

tanΒ = 50tanΒ = 4tanΒ = 2tanΒ = 1

Experimentally favored

Degrassi et al, 1205.6497


• Higgs mass2 very unnatural (tuning by 1034) unless TeV physics(supersymmetry, composite Higgs, extra dimensions)

H

H Hλ

W

H Hg2

W

W

H Hg g

f

f

H Hh h


• Is naturalness a good guide? cf dark energy (tuning by 10120)

(environmental solution?)

• Even for higher-scale new physics: little (baby) hierarchy problem(but reduces FCNC, EDM constraints)


Uniqueness or Environment

• Gauge interactions:determined by symmetry(but groups, representations, SSB)

• Yukawa interactions:unconstrained, unless newsymmetries/principles(local, global, discrete, stringy)

• The uniqueness paradigm:simple, unique, underlyingtheory

Kepler’s Mysterium Cosmographicum


• The environmental paradigm(cf., planetary orbits)

– No simple explanation of parameters

– String landscape: may be & 10600

vacua (de Sitter?); no known selectionprinciple

– Subset habitable, with differentgroups, remnants, hierarchymechanisms, parameters

– Multiverse sampled by eternalinflation?

– Environmental selection? (A word?)


Minimality or Remnants

• Bottom up: minimality often assumed

• Top down: new particles/interactions (remnants) often “slipthrough net”

– Z′, vector fermions, extended Higgs, leptoquarks, diquarks; dark sectors


The Realizations

• Strong dynamics at low scale (composite Higgs, · · · )

• Low fundamental scale (large or warped dimensions, low string scale)

• Perturbative connection to high scale (string, GUT)

– Supersymmetry (nonminimal?), · · ·– Remnants?– Nothing

• Multiverse? (not exclusive)


Future Collider Proposals

• HL-LHC (CERN): (pp, 14 TeV, 3000 fb−1)

• ILC (Japan): (e+e−; 250, 350, 500 GeV (→ 1 TeV),) ILC Higgs: 1310.0763

• CLIC (CERN): (e+e−; 350 GeV→ 3 TeV,) CLIC: 1209.2543, 1307.5288

• CEPC (China): (e+e−; 240 GeV,) CEPP: cepc.ihep.ac.cn

• SPPC (China): (pp, 100 TeV?)

• FCC (CERN)





http://cepc.ihep.ac.cn

The FCC-ee


• FCC-ee (TLEP)

• ∼100 km

• e+e−: precision EW, Higgs,t, BSM

• 90 (Z), 125 (H)?, 160 (WW ),240 (H), 350 (tt̄) GeV

• e± polarization?

• 1012 − 1013Z’s (Tera-Z)

2× 108WW , 105H, 106 tt̄

• FCC-hh (VHE-LHC)

– pp: EWSB, BSM

– 2040-2050: 80-100 TeV

FCC-ee (TLEP): 1308.6176



• 1012 − 1013Z’s(LEP: 1.7× 107; SLC: 6× 105,

Pe− & 0.75)

• Combine with WW and tt̄threshold scans

• Need significant improvementin theory calculations (3 loop)

quantity precision current

MZ 100 keV 2.1 MeVΓZ 100 keV 2.3 MeV

sin2 θ̂W (M2Z) 6× 10−6 5× 10−5

∆α(MZ)/α 1.1× 10−4 3× 10−5

MW 300 keV 15 MeVαs(MZ) 0.0001 0.0006

mt 10 MeV 0.9 GeVNν (Zγ) 0.001 0.008

(GeV)topm171.5 172 172.5 173 173.5 174 174.5 175

(G

eV)

Wm

80.35

80.355

80.36

80.365

80.37 TLEP (Z pole)TLEP (Direct)ILC (Direct)LHC (Future)TevatronStandard Model

(GeV) s50 60 70 80 90 100 110 120 130 140 150

_)/_(

m

-510

-410

at FCC-eeµµ

FB accuracy from AQED_

P. Janot: 1512.05544



• Sensitive to Z − Z′, W −W ′, f − f ′ mixing (vector exotics,

composite Higgs, · · · ); unitarity violation

• Rare/invisible decays: Z,H → dark matter; sterile ν; FCNC;universality violation

• Oblique corrections: Higgs; EWSB; chiral fermions; multipletsplitting

• Effective operators; triple gauge couplings

Barducci et al: 1504.05407

HNL mass (GeV)1 10

2|U

|

-1110

-1010

-910

-810

-710

-610Normal hierarchy

BBN

Seesaw

BAU

PS191

NuTeV

SHiP

FCC-ee

Blondel et al: 1411.5230




(GeV)Hm60 70 80 90 100 110 120 130 140

2 χ∆

0

1

2

3

4

5

6

7

8

9

10

TLEP, matching theory errors

TLEP, current theory errors

LEP, SLC, and Tevatron

5

!0.2 !0.1 0.0 0.1 0.2

!0.2

!0.1

0.0

0.1

0.2

(a)

!0.04 !0.02 0.00 0.02 0.04

!0.04

!0.02

0.00

0.02

0.04

(b)S

T

S

T

PresentGigaZ

TeraZ

MSSMXt = 0

MSSMXt/mt̃ =

√6

SingletA/mS = 1

200

400600

200

400

400

600

PresentGigaZ

TeraZ

400

600

800

800

10001200

800

1000

1500

FIG. 3. The 1σ (darker) and 2σ (lighter) ellipses of precision EW parameters S and T . We show current fits (solid, black) together withprojected sensitivities at ILC GigaZ (dashed, blue) and TLEP TeraZ (dotted, red). The lines show the size of S and T parameters in our singletmodel with A = mS (teal) and in the MSSM with tan β = 30 for Xt =

√6mt̃ (green) and Xt = 0 (purple). The tick marks show specific

mass values in each model;mt̃ values in 200 GeV increments starting frommt̃ = 200 GeV forXt = 0 andmt̃ = 400 GeV forXt =√

6mt̃

in the MSSM; mS values in 200 GeV increments between 200-1000 GeV and 500 GeV increments between 1000-3000 GeV in the singletmodel.

c3G =g2

s(4π)2

120

c3W = g2

(4π)2120

c2G =g2

s(4π)2

120

c2W = g2

(4π)2120

c2B = g′2(4π)2

120

cGG =h2

t(4π)2

112

[(1 + 1

12

g′2c2β

h2t

)− 1

2

X2t

m2t̃

]cWB = − h2

t(4π)2

124

[(1 + 1

2

g2c2β

h2t

)− 4

5

X2t

m2t̃

]

cWW =h2

t(4π)2

116

[(1 − 1

6

g′2c2β

h2t

)− 2

5

X2t

m2t̃

]cW =

h2t

(4π)2140

X2t

m2t̃

cBB =h2

t(4π)2

17144

[(1 + 31

102

g′2c2β

h2t

)− 38

85

X2t

m2t̃

]cB =

h2t

(4π)2140

X2t

m2t̃

cH =h4

t(4π)2

34

[(1 + 1

3

g′2c2β

h2t

+ 112

g′4c22β

h4t

)− 7

6

X2t

m2t̃

(1 + 1

14

(g2+2g′2)c2β

h2t

)+ 7

30

X4t

m2t̃

]

cT =h4

t(4π)2

14

[(1 + 1

2

g2c2β

h2t

)2

− 12

X2t

m2t̃

(1 + 1

2

g2c2β

h2t

)+ 1

10

X4t

m4t̃

]

cR =h4

t(4π)2

12

[(1 + 1

2

g2c2β

h2t

)2

− 32

X2t

m2t̃

(1 + 1

12

(3g2+g′2)c2β

h2t

)+ 3

10

X4t

m4t̃

]

cD =h2

t(4π)2

120

X2t

m2t̃

c6 = − h6t

(4π)212

⎧⎪⎪⎨⎪⎪⎩

[1 + 1

12

(3g2−g′2)c2β

h2t

]3

+[− 1

12

(3g2+g′2)c2β

h2t

]3

+(1 + 1

3

g′2c2β

h2t

)3

−X2t

m2t̃

[2

(1 + 1

12

(3g2−g′2)c2β

h2t

) (1 + 1

8

(g2+g′2)c2β

h2t

)+

(1 + 1

3

g′2c2β

h2t

)2]

+X4

t

m4t̃

[1 + 1

8

(g2+g′2)c2β

h2t

]− X6

t

m6t̃

110

⎫⎪⎪⎬⎪⎪⎭

TABLE II. Wilson coefficients ci for the operators Oi in Table I generated from integrating out MSSM stops with degenerate soft mass mt̃.gs, g, and g′ denote the gauge couplings of SU(3), SU(2)L, and U(1)Y , respectively, ht = mt/v, and tan β = ⟨Hu⟩/⟨Hd⟩ in the MSSM.

rison, et al., (2013), arXiv:1306.6327 [physics.acc-ph];H. Baer, T. Barklow, K. Fujii, Y. Gao, A. Hoang,et al., (2013), arXiv:1306.6352 [hep-ph]; C. Adolph-sen, M. Barone, B. Barish, K. Buesser, P. Burrows,et al., (2013), arXiv:1306.6353 [physics.acc-ph]; (2013),arXiv:1306.6328 [physics.acc-ph]; T. Behnke, J. E. Brau,P. N. Burrows, J. Fuster, M. Peskin, et al., (2013),

arXiv:1306.6329 [physics.ins-det].[4] M. Bicer et al. (TLEP Design Study Working Group),

JHEP 1401, 164 (2014), arXiv:1308.6176 [hep-ex].[5] C. Prescott, W. Atwood, R. L. Cottrell, H. DeStaebler, E. L.

Garwin, et al., Phys.Lett. B84, 524 (1979).[6] G. Alexander et al. (LEP Collaborations, ALEPH Collabora-

tion, DELPHI Collaboration, L3 Collaboration, OPAL Collab-

Henning ea, 1404.1058

Ellis, You: 1510.04561




Z-Pole and Higgs Factory Reach

• Composite Higgs at scale fκW,Z =

√1− v2

f2, S ∼ v2

4f2

• MSSM t̃Lκg − 1 ∼ m2

t4m2

t̃L

T ∼ m4t

16πs2WM2Wm2t̃L

NEW COLLIDERS FOR A NEW FRONTIER 15

Experiment Z (68%) f (GeV) g (68%) mt̃L(GeV)

HL-LHC 3% 1.0 TeV 4% 430 GeVILC500 0.3% 3.1 TeV 1.6% 690 GeV

ILC500-up 0.2% 3.9 TeV 0.9% 910 GeVCEPC 0.2% 3.9 TeV 0.9% 910 GeVTLEP 0.1% 5.5 TeV 0.6% 1.1 GeV

Experiment S (68%) f (GeV) T (68%) mt̃L(GeV)

ILC 0.012 1.1 TeV 0.015 890 GeVCEPC (opt.) 0.02 880 GeV 0.016 870 GeVCEPC (imp.) 0.014 1.0 TeV 0.011 1.1 GeV

TLEP-Z 0.013 1.1 TeV 0.012 1.0 TeVTLEP-t 0.009 1.3 TeV 0.006 1.5 TeV

Table 2.1 Interpreting the Higgs coupling and the bounds on the oblique S and T parameters in terms ofnew physics reach [3]. CEPC (imp.) is assuming the improvement in both sin2 ✓`e↵ and �Z .

and similarly

T =3

8⇡cos2✓W

logM

mW

⇥ 2v2cH

M2= .2⇥ �Zh (2.10)

where we have chosen M ⇠ 300 GeV as a reference. The projected CEPC sensitivity toS, T on the Z poles is �S,�T ⇠ .01, but we see that this is significantly weaker than thedirect reach in �Zh.

The CEPC also has some sensitivity to Higgs self-interactions arising from the (h†h)3

operator. Amusingly, this operator does not induce any of the other dimension 6 operatorsinvolving the Higgs under 1-loop RG evolution. But there is infrared calculable correctionto the Z-Higgs coupling at 1-loop, which probes deviations in the triple Higgs couplingat the 50% level [5].

Of course dimension six operators for the Higgs also give rise to a quadratically ris-ing amplitude for longitudinal WW scattering A(WLWL ! WLWL) ⇠ c s

M2 , which is aclear target of study for the SPPC; any deviation in Higgs couplings seen at CEPC shouldbe correlated with WW scattering at SPPC. It is however difficult to make a sharp cor-relation in a model-independent way: a visible effect at the CEPC means that scale Mcan’t be much larger than the TeV scale, but then partonic scatterings at the SPPC cantake place at scales above M . The falling parton luminosities do not compensate for therising amplitudes, so the prediction for the SPPC is dominated by the physics of the UVcompletion. For instance in composite Higgs modes, we expect that the Higgs couples toa new massive ⇢-like spin-one particle. Detailed studies of the SPPC reach for such statesare under way, but a rough estimate of the reach extends to ⇢ masses up to ⇠ 8 TeV:

We have largely focused on deviations in the largest Higgs couplings to the gaugebosons and the third generation, but the study of Higgs couplings to the light fermionscould be equally interesting, and has the potential to shed significant new light on the ori-gin of flavor. The “big" couplings to the Higgs are already constrained by the Higgs doingits job of unitarizing scattering amplitudes amongst longitudinal W ’s and top quarks. Onthe other hand, the small masses of the lighter generation fermions allow the Unitarity

Fan, Reece, Wang: 1411.1054



References

• Bicer et al, First Look at the Physics Case of TLEP: 1308.6176

• Henning, Lu, Murayama What do precision Higgs measurements buy us?:

1404.1058

• Fan, Reece, and Wang, Possible Futures of Electroweak Precision: ILC,

FCC-ee, and CEPC: 1411.1054

• Blondel et al, Search for Heavy Right Handed Neutrinos at the FCC-ee:

1411.5230

• R. Tenchini, Precision Electroweak Measurements at FCC-ee: 1412.2928

• Barducci et al., Top pair production at a future e+e− machine in a composite

Higgs scenario:1504.05407

• Ellis and You, Sensitivities of Prospective Future e+e- Colliders to Decoupled

New Physics: 1510.04561














• P. Janot, Precision measurements of the top quark couplings at the FCC:

1510.09056

• P. Janot, Direct measurement of αQED(mZ) at the FCC-ee: 1512.05544

• M. Dam, Precision Electroweak measurements at the FCC-ee: 1601.03849

• D. d’Enterria, Physics case of FCC-ee: 1601.06640







Conclusions

• Standard Model is very successful, but complicated, fine-tuned

• Precision physics: major role in establishing SM and restricting BSM

• Major questions

– Naturalness or tuning

– Uniqueness or environment

– Minimality or remnants

– Unification (strings/landscape, GUTs, SUSY, remnants) or strongcoupling/compositeness

– Dark matter/energy; vacuum stability; baryogenesis; ν mass

• Signatures often similar (e.g., 750 GeV diphoton)

• The challenge: distinguishing (multiple/complementary probes, effects)


• Complementary probes

– e+e− (precision Z-pole and above, Higgs factory)

– Other precision and flavor physics (gµ − 2, rare decays/processes,

heavy quark, neutrino)

– Dark matter searches, cosmology

– Energy frontier (LHC, pp at 100 TeV scale)

• The FCC-ee is especially promising


Typical Stringy Effects

• Z′ (or other gauge)

• Extended Higgs/neutralino (doublet, singlet)

• Quasi-chiral exotics

• Leptoquark, diquark, 6RP couplings

• Family non-universality (from different origins) (Yukawas, U(1)′)

• Various ν mass mechanisms (HDO: Majorana or Dirac; D (string)

instantons: non-minimal seesaw, Weinberg op, Dirac, sterile)

• (Quasi-)hidden sectors (strong coupling? SUSY breaking? dark matter?

random?); may be portals (exotics, Z′, Higgs)


• Perturbative global symmetries from anomalous U(1)′

(exponentially-suppressed breaking)

• Nonstandard hypercharge embeddings/normalizations

• Fractionally charged color singlets (e.g., 12)

(confined?, stable relic? millicharged?)

• Large/warped dimensions, low string scale(TeV black holes, stringy resonances)

• Axions, moduli, cosmic strings

• Time/space/environment-varying couplings

• LIV, VEP (speeds, decays, [oscillations] of HE γ, e, gravity waves, [ν’s])


Future/Proposed Precision Program at Colliders

Large Hadron Collider (LHC), CERN

• pp: Higgs, EW, QCD, BSM, · · ·

• 2009-2012: 7-8 TeV, 30 fb−1

• 2015-2022: 13-14 TeV, 300 fb−1

• 2025-2035: HL-LHC, 14 TeV,3000 fb−1

• 33 TeV HE-LHC?


International Linear Collider (ILC), Japan

• e+e−: Higgs factory,Z-pole, WW , tt̄, Z′, · · ·

• 31 km (→ 50)

• 250, 350, 500 GeV(→ 1 TeV)

• Pe− ∼ 80%(Pe+ ∼ 50-60%)

• Z-pole (Giga-Z)

Chapter 3The International Linear ColliderAccelerator

3.1 The ILC Technical Design3.1.1 Overview

The International Linear Collider (ILC) is a high-luminosity linear electron-positron collider based on1.3 GHz superconducting radio-frequency (SCRF) accelerating technology. Its centre-of-mass-energyrange is 200–500 GeV (extendable to 1 TeV). A schematic view of the accelerator complex, indicatingthe location of the major sub-systems, is shown in Fig. 3.1:

central region5 km

2 km

positronmain linac

11 km

electronmain linac

11 km

2 km

Damping Rings

e+ source

e- source

IR & detectors

e- bunch compressor

e+ bunch compressor

Figure 3.1. Schematic layout of the ILC, indicating all the major subsystems (not to scale).

• a polarised electron source based on a photocathode DC gun;

• a polarised positron source in which positrons are obtained from electron-positron pairs byconverting high-energy photons produced by passing the high-energy main electron beamthrough an undulator;

• 5 GeV electron and positron damping rings (DR) with a circumference of 3.2 km, housed in acommon tunnel;

• beam transport from the damping rings to the main linacs, followed by a two-stage bunch-compressor system prior to injection into the main linac;

• two 11 km main linacs, utilising 1.3 GHz SCRF cavities operating at an average gradient of31.5 MV/m, with a pulse length of 1.6 ms;

9

ILC TDR: www.linearcollider.org/ILC/Publications/Technical-Design-Report

ILC Higgs: 1310.0763


http://www.linearcollider.org/ILC/Publications/Technical-Design-Report


Compact Linear Collider (CLIC), CERN

Chapter 3

CLIC Accelerator TechnologyThe aim of the CLIC study has been to develop a technology that can be used to build a multi-TeVlinear electron-positron collider. The study therefore concentrated on a 3 TeV design and demonstratedthe feasibility of the technology, as documented in [1]. A design for 500 GeV has also been developed,although in less detail. After a short summary of the design, the following sections describe two examplesof a staged approach to CLIC, the status of the feasibility studies and the energy flexibility of each energystage of CLIC after construction.

3.1 The CLIC Design at 3 TeVThe conceptual layout of CLIC is shown in Figure 3.1 and the fundamental parameters are given inTable 3.1. These parameters are the result of a full cost optimisation, see Chapter 2.1 in [1].

(c)FT

TA

BC2

delay loop

2.5 km

decelerator, 24 sectors of 878 m

819 klystrons15 MW, 142 µs

CR2

CR1

circumferencesdelay loop 73 mCR1 293 mCR2 439 m

BDS

2.75 kmIP

TA

BC2

delay loop

2.5 km

819 klystrons15 MW, 142 µs

drive beam accelerator

2.4 GeV, 1.0 GHz

CR2

CR1

BDS

2.75 km

48.3 km

CR combiner ring

TA turnaround

DR damping ring

PDR predamping ring

BC bunch compressor

BDS beam delivery system

IP interaction point

dump

drive beam accelerator

2.4 GeV, 1.0 GHz

BC1

Drive Beam

Main Beam

e+ injector,2.86 GeVe+

PDR 389 m

e+

DR 427 m

booster linac

2.86 to 9 GeV

e+ main linac

e– injector,2.86 GeV e–

PDR 389 m

e–

DR 427 m

e– main linac, 12 GHz, 100 MV/m, 21 km

Fig. 3.1: Overview of the CLIC layout atp

s = 3 TeV.

The main (colliding) beams are produced in conventional electron and positron sources and ac-celerated to 2.86 GeV. The beam emittances are reduced in a pre-damping ring followed by a dampingring. In the ring-to-main-linac transport system the beams are compressed longitudinally and acceler-ated to 9 GeV. The main linac uses 100 MV/m 12 GHz accelerating structures to achieve the final beamenergy. In the Beam Delivery System (BDS) the beam is cleaned by collimation and compressed to thevery small size at collision. The main challenge for the CLIC main beam is to achieve the main linacaccelerating gradient (i.e. the high beam energy) and the good beam quality (i.e. the high luminosity). Anadditional challenge arises from the strong beam-beam interaction and is discussed in Chapter 4. Duringthe collision particles will emit beamstrahlung, which reduces their energy and leads to the developmentof a luminosity spectrum. We therefore quote the total luminosity as well as the luminosity above 99%of the nominal centre-of-mass energy. The design foresees 80% polarisation of the electrons at collision,and it is compatible with the addition of a polarised positron source.

The necessary RF power for the main linac is extracted from a high-current, low-energy drive

19

• e+e−: Higgs, tt̄, BSM

• Two beam acceleration

• 48 km

• ∼ 2030: 350 GeV → 3 TeV

• Polarized e− (e+?)

CLIC CDR: clic-study.web.cern.ch/content/conceptual-design-report

CLIC: 1209.2543, 1307.5288


http://clic-study.web.cern.ch/content/conceptual-design-report



Circular Electron Positron Collider (CEPC), China

Easy Access • 300 km from Beijing • 3 h by car • 1 h by train

Beijing Qinhuangdao

Tianjing

Beidaihe

38

Figure 3.3: Illustration of the CEPC-SPPC ring sited in Qinghuangdao. The small circle is 50

km, and the big one 100 km. Which one will be chosen depends on the funding scenario.

Figure 3.4 shows the CEPC ring on the map of Qinghuangdao. The Yellow River Engineering Consulting Co., Ltd., has done an extensive survey and geological study in this area [1].

Figure 3.4: A hypothetical location of the CEPC ring on the Qinghuangdao area map.

• e+e−: Higgs factory, Z,WW , Z′, · · ·

• 50 or 100 km

• 240 GeV (H)

• Z-pole (1010 − 1011Z’s)

• Super pp Collider, (SPPC)

– pp: BSM, naturalness,EWBG, DM

– 100-140 TeV

CEPP: cepc.ihep.ac.cn


http://cepc.ihep.ac.cn

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