Searching for a new world New Physics at the LHC and beyond LianTao - - PowerPoint PPT Presentation

Searching for a new world

New Physics at the LHC and beyond

LianTao Wang

• U. Chicago

FeynRules/Madgraph School. Nov. 19, 2018. USTC HeFei.

Guardian

SM: complete yet incomplete

• Complete: could be a consistent theory valid up

to the Planck scale.

• Incomplete: many open questions

Origin of electroweak scale Dark matter Origin of CP, flavor Matter anti-matter asymmetry …

• Goal of particle physics: answer these questions.
• Colliders (LHC and beyond) will be crucial.

Road ahead at the LHC

We are here.

LHC is pushing ahead.

• Exp. collaborations are pursuing a broad

and comprehensive physics program: SUSY, composite H, extra Dim, etc.

As data accumulates

)

• 1

luminosity (fb

10 20 30 40 50 60 70 80 90 100

low

m /

high

m

0.5 1 1.5 2 2.5

14 TeV / 8 TeV

= 2 TeV

low

m

qq q q qg gg

Rapid gain initial 10s-100 fb-1, slow improvements afterwards. Progress will become slower, harder

New directions?

stronger coupling heavier NP particle

covered by current searches

NP too heavy for LHC with direct production dark sector covered by current searches

stronger coupling heavier NP particle

stronger coupling heavier NP particle

NP too heavy for LHC with direct production dark sector covered by current searches

Example: Long Lived particles (LLP)

• Very weakly coupled to the SM.

Connection with dark matter, neutrino, etc. τ

• Displaced-Long lived, soft, kink, …

Covered by LHC searches already.

• Cosmological constraints from

BBN: τ < 0.1 sec (107 m)

Curtin and Sundrum

Here, I focus on: decay length >> 10 meters

tons of models

General LLP Map

Far detectors

“demonstrator”

les

• n
• ayers
• ectrons
• –

–

• Letter of intent:

MATHUSLA

FASER

CODEX-b

ϕ

Data acquisition will be moved to surface for run 3

new detectors far away from the interaction region

Could reach τ≈104-5 m

Exotic Higgs decays

For low masses, ATLAS/CMS are background limited, CODEX-b & MATHUSLA have an edge

ATLAS reach: A. Coccaro, et al.: 1605.02742

γd γd h

• V. Gligorov, SK, M. Papucci, D. Robinson: 1708.02243

9

• Application:


Neutral Naturalness
 (See back-up material) 


• S. Knapen

Far detectors

“demonstrator”

les

• n
• ayers
• ectrons
• –

–

• Letter of intent:

MATHUSLA

FASER

CODEX-b

ϕ

Data acquisition will be moved to surface for run 3

Have we fully optimized LLP searches at the interaction points ATLAS, CMS, LHCb?

Optimal place to catch LLP

Number of particle decayed within detector volume:

ΔΩ

L ΔL

#in ≃ #produced × ΔΩ 4π × ΔL d e−L/d

d = γcτ decay length

Very long lived: d ≥ 100s meters d ≫ ΔL, L

Optimal place to catch LLP

Number of particle decayed within detector volume:

#in ≃ #produced × ΔΩ 4π × ΔL d e−L/d

d = γcτ

ATLAS/CMS (LHCb) Far detectors

ΔΩ ΔL L ∼ 4π < 0.1

1 − 10 meters 1 − 10 meters 1 − 10 meters 10 − 100 meters

Optimal place to catch LLP

#in ≃ #produced × ΔΩ 4π × ΔL d e−L/d

d = γcτ

ATLAS/CMS (LHCb) Far detectors

ΔΩ ΔL L ∼ 4π < 0.1

1 − 10 meters 1 − 10 meters 1 − 10 meters 10 − 100 meters

Advantage of far detector? Far away from interaction point, less background. New proposal: use timing information Significantly lower background near interaction point.

Time delay

LT1 LT2 X

a b

SM

`X `a `SM

Timing layer

Good for massive LLP produced with small or moderate boost βX < 1

Basic topologies

SM SM X or SM X Y

SM SM X or SM X

γ ≃ mY 2mX

boost: challenging for mX ≪ mY benchmark: Higgs portal Y = Higgs boost: γ ∼ 1 slow moving, sizable Δt benchmark: SUSY

X → SM

Long lived

χ0 → gravitino + . . . Long lived

X = neutralino

X = LLP

Sensitivity to Higgs portal

h → X X, X → j j

MS(30ps), Δt>0.4ns MS(200ps), Δt>1ns EC(30ps), Δt>1ns MS2DV, noBKG MS1DV, optimistic BRinv

h <3.5%

mX in [GeV] 10 40 50

10-3 10-2 10-1 100 101 102 103 104 105 106 107 108 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100

cτ (m) BR(h→XX) Precision Timing Enhanced Search Limit (HL-LHC)

For example, for BR(h → XX) ∼ 10−3 EC(MS) reach can be cτ ∼ 103(104) meters

Jia Liu, Zhen Liu, LTW

Sensitivity to SUSY

200 400 600 800 1000 1200 1400 10-3 10-2 10-1 100 101 102 103 104 105

mX (GeV) cτ (m) Precision Timing Enhanced Search Limit (HL-LHC) EC

nbkg=100 nbkg=0

MS

nbkg=100 nbkg=0 8 TeV 13 TeV Diplaced Dijet

F =105 TeV

104 103 GMSB Higgsino

Δt > 1.2 ns Δt > 2 ns Δt > 1 ns Δt > 10 ns

Slower moving LLP , timing cuts can be further relaxed.

Jia Liu, Zhen Liu, LTW

stronger coupling heavier NP particle

NP too heavy for LHC with direct production dark sector covered by current searches

Revealing trace of new physics with precision measurements

Higgs Standard Model-like

Agree to about 10-20%

Not entirely surprising

• In general, deviation induced by new physics is of the

form

Current LHC precision: 10% ⇒ sensitive to MNP < 500-700 GeV At the same time, direct searches constrain new physics below TeV already. Unlikely to see O(1) deviation.

δ ' c v2 M 2

NP

MNP : mass of new physics c: O(1) coefficient

Significant improvement with high lumi

4-5% on Higgs coupling, reach TeV new physics

Precision measurement with distribution

SM

broad resonance long tails no rate beyond this

E Low S/B, systematic dominated. Room to improve.

q¯ q → V V, V = W, Z, h.

Diboson production at the LHC

VL VL, h

New physics contribution

New physics effect encoded in the non-renormalizable operators:

1 Λ2 O Λ : new physics scale

Precision measurement at the LHC possible?

δσ σSM ∼ m2

W

Λ2 ∼ 2 × 10−3

LEP precision tests probe NP about 2 TeV At LHC, new physics effect grows with energy

LHC needs to make a 20% measurement to beat LEP LHC has potential.

δσ σSM ∼ E2 Λ2 ∼ 0.25

→ Λ ≥ 2 TeV

E ∼ 1 TeV, Λ ∼ 2 TeV

Picking final state important

At LHC, interference with SM crucial

Signal-SM interference

δσ σSM ∼ E2 Λ2 ∼ 0.25

Without interference

δσ σSM ∼ E4 Λ4 ∼ 0.05

• 1. WZ final states, only longitudinal mode useful
• 2. W/Z+h

Will be challenging

SM WW, WZ processes are dominated by transverse modes New technique such as polarization tagging of W/Z crucial Wh/Zh(bb) channels have large reducible background

Difficult measurement. Large improvement needed. Room for developing new techniques

Operators: d=6

Projections

Possible to reach 4 TeV. Better than LEP , and many LHC direct searches

• D. Liu, LTW

cqL

(3) = 1, L = 3 ab-1

cqL

(3) = 1, L = 300 fb-1

cHB = 1, L = 3 ab-1 cHB = 1, L = 300 fb-1 c3 W = 1, L = 3 ab-1 c3 W = 1, L = 300 fb-1 OL

(3) q, LEP δgZbL bL

OHW - OHB, HL-LHC h → Z γ OW + OB, LEP S-parameter

• ()

() () () Λ %[] Δ ∈ [%%] =

See also: Alioli, Farina, Pappadopulo, Ruderman, Franceschini, Panico, Pomarol, Riva, Wulzer, Azatov, Elias-Miro, Regimuaji, Venturini

Beyond LHC

Future Colliders

ILC in Japan

来自中国的建议

• 年 月“第二届中国高能加速器物理战略发展研讨会”提出了

建造周长为 环形加速器的建议： – ：质心能量为 的高能正负电子对撞机 工厂） – ：在同一隧道建造质心能量为 的强子对撞机。

• 年 月

日香山会议共识：“环形正负电子对撞机 工 厂 超级质子对撞机 是我国高能物理发展的重要选项 和机遇”

• 年 月

日“第三届中国高能加速器物理战略发展研讨会”结 论：“环形正负电子对撞机 工厂 超级质子对撞机 是我国未来高能物理发展的首要选项”

ee+ Higgs Factory pp collider

• Circular. “Scale up” LEP+LHC

CLIC 250 GeV FCC-ee (CERN), CEPC(China) ~100 TeV FCC-hh (CERN), SppC(China)

Ambitious program

FCC-ee:

∼ 106 Higgses, ∼ 1013 Zs, . . .

13 yr run plan: Higgs=3, Z=4, top=5, W=1

Currently, no plan to scan the ttbar threshold.

ILC run plan

years

5 10 15 20 25

integrated luminosities [fb]

1000 2000 3000 4000

Luminosity Upgrade Energy Upgrade ILC, Scenario H-20-staged ECM = 250 GeV ECM = 350 GeV ECM = 500 GeV

Integrated Luminosities [fb]

∼ 0.6 × 106 Higgs

+106 Higgses

No Z-pole or WW run planned

What precision should we aim for?

• In precision measurements, we are going after

deviations of the form

• Take the Higgs coupling.

LHC precision: 5-10% ⇒ sensitive to MNP < TeV

• To go beyond the LHC, need 1% or less precision.

δ ' c v2 M 2

NP

MNP : mass of new physics c: O(1) coefficient

Higgs factory processes

e− e+ Z∗ Z H e− ¯ νe e+ W ∗ W ∗ νe H e− e+ e+ Z∗ Z∗ e− H

H [GeV] f f →

• e

+

e

200 250 300 350 400

(fb) σ

50 100 150 200 250 CEPC Preliminary

H → WW ) ν ν → HZ( Total HZ

Process Cross section Nevents in 5 ab−1 Higgs boson production, cross section in fb e+e− → ZH 212 1.06 × 106 e+e− → ννH 6.72 3.36 × 104 e+e− → eeH 0.63 3.15 × 103 Total 219 1.10 × 106

Zh cross section

[GeV]

• µ

+

µ recoil

M

120 125 130 135 140

Entries/0.2 GeV

1000 2000 3000

CEPC Preliminary

• 1

Ldt = 5 ab

∫

;

• µ

µ → Z CEPC Simulation S+B Fit Signal Background

• e−

e+ f ¯ f Z h

Can use recoil mass to identify Zh process, independent of Higgs decay

zero momentum: M2

recoil = (√s − Eff)2 − p2 ff = s − 2Eff

√s + m2

ff

and are, respectively, the total energy, momentum a

⇒ inclusive measurement of Zh cross section

Higgs width.

e− e+ f ¯ f Z h

Z Z*

ΓH ∝ Γ(H → ZZ∗) BR(H → ZZ∗) ∝ σ(ZH) BR(H → ZZ∗)

e− e+ W W h b ¯ b

ΓH ∝ Γ(H → bb) BR(H → bb) ∝ σ(ννH → ννbb) BR(H → bb) · BR(H → WW ∗)

Unique capability of lepton colliders.

CEPC can do very well

Up to sub percent precision, reach to new physics at multi-TeV scale. Far beyond the reach of LHC.

D r a f t

• v

2 . 1

LHC 300/3000 fb-1 CEPC 240 GeV at 5.6 ab-1 wi/wo HL-LHC

κb κt|κc κg κW κτ κZ κγ 10-3 10-2 10-1 1 Relative Error

Precision of Higgs coupling measurement (7-parameter Fit)

Zhen Liu

Electroweak precision

• 0.15
• 0.10
• 0.05

0.00 0.05 0.10 0.15

• 0.15
• 0.10
• 0.05

0.00 0.05 0.10 0.15 S T EWPT: Oblique Parameters Current (68%) CEPC (68%)

• 0.03 -0.02 -0.01

0.00 0.01 0.02 0.03

• 0.03
• 0.02
• 0.01

0.00 0.01 0.02 0.03 S T EWPT: Oblique Parameters

FCC can do even better (by a factor of a few)

100-ish TeV pp collider

year

1 2 3 4 5 6 7 8 9 10

ratio of mass reach

1 2 3 4 5 6 7 8

s / year

10 × = 6 TeV, 0.6

m

• 1

Mass Reach compared to HL-LHC 3 ab = 100 TeV s

• 1

s

• 2

cm

32

10 × 1 (8 yrs)

• 1

s

• 2

cm

34

10 × (2 yrs) + 3

• 1

s

• 2

cm

32

10 × 1

• 1

s

• 2

cm

34

10 × 3

• 1

s

• 2

cm

35

10 × 1

Hinchliffe, Kotwal, Mangano, Quigg, LTW

A factor of at least 5 increase in reach beyond the LHC, with modest luminosity

Electroweak symmetry breaking

“Simple” picture: Mexican hat

Soon ¡after ¡Nambu’s ¡work 𝜒 =

• √ ¡(𝜒 + 𝑗𝜒)

𝑀 = ¡𝜖 ¡𝜒 ¡𝜖 ¡𝜒 − ¡𝜈

¡𝜒

¡𝜒 − 𝜇 6 ¡(𝜒 ¡𝜒), 𝜒

• 𝜒, ¡

𝜇 φ 𝜒 ¡ ⟶ ¡𝑓 ¡𝜒 𝜈

• Then ¡the ¡potential ¡looks ¡like ¡a ¡“Mexican ¡hat”

Similar to, and motivated by Landau-Ginzburg theory

• f superconductivity.

V (h) = 1 2µ2h2 + λ 4 h4

hhi ⌘ v 6= 0 ! mW = gW v 2

“Simple” picture: Mexican hat

Soon ¡after ¡Nambu’s ¡work 𝜒 =

• √ ¡(𝜒 + 𝑗𝜒)

𝑀 = ¡𝜖 ¡𝜒 ¡𝜖 ¡𝜒 − ¡𝜈

¡𝜒

¡𝜒 − 𝜇 6 ¡(𝜒 ¡𝜒), 𝜒

• 𝜒, ¡

𝜇 φ 𝜒 ¡ ⟶ ¡𝑓 ¡𝜒 𝜈

• Then ¡the ¡potential ¡looks ¡like ¡a ¡“Mexican ¡hat”

Similar to, and motivated by Landau-Ginzburg theory

• f superconductivity.

However, this simplicity is deceiving. Parameters not predicted by theory. Can not be the complete picture.

V (h) = 1 2µ2h2 + λ 4 h4

hhi ⌘ v 6= 0 ! mW = gW v 2

Mysteries of the electroweak scale.

Soon ¡after ¡Nambu’s ¡work 𝜒 =

• √ ¡(𝜒 + 𝑗𝜒)

𝑀 = ¡𝜖 ¡𝜒 ¡𝜖 ¡𝜒 − ¡𝜈

¡𝜒

¡𝜒 − 𝜇 6 ¡(𝜒 ¡𝜒), 𝜒

• 𝜒, ¡

𝜇 φ 𝜒 ¡ ⟶ ¡𝑓 ¡𝜒 𝜈

• Then ¡the ¡potential ¡looks ¡like ¡a ¡“Mexican ¡hat”

Mysteries of the electroweak scale.

What we know now

h

Mysteries of the electroweak scale.

• How to predict/calculate Higgs mass? Naturalness
• Full Higgs potential?
• Order of electroweak phase transition

What we know now

h

The energy scale of new physics responsible for EWSB Electroweak scale, 100 GeV. mh , mW …

How to predict Higgs mass?

The energy scale of new physics responsible for EWSB Electroweak scale, 100 GeV. mh , mW … What is this energy scale? MPlanck = 1019 GeV, …? If so, why is so different from 100 GeV? The so called naturalness problem

How to predict Higgs mass?

The energy scale of new physics responsible for EWSB Electroweak scale, 100 GeV. mh , mW …

Naturalness of electroweak symmetry breaking

TeV new physics. Naturalness motivated Many models, ideas.

Models

• “conventional”

Supersymmetry (SUSY), Composite Higgs, … A bit uncomfortable, still viable.

All eyes on these searches

My view: not a big problem yet.

fine-tuning = comparison: Supersymmetry Composite Higgs

stop top partner, T

current limit:

1 16π2 m2

T

vs m2

h = (125 GeV)2

mT ∼ 1 TeV

A confusing picture for Higgs mass

120 125 130 135 140 145 150 155 160 0.5 1.0 1.5 2.0 2.5

mHiggs

[GeV]

mKK

[TeV]

12/3 21/6 27/6 32/3 + 15/3 + 1-1/3

Supersymmetry Stop too heavy to be natural Composite top partner too light, excluded Such conclusions too simplistic, “work around” available. A bit uncomfortable, yes. Not time to give up just yet.

MSUSY (GeV)

Models

• “conventional”

Supersymmetry (SUSY), Composite Higgs, … A bit uncomfortable, still viable.

Models

• New attempts

Neutral naturalness, N-naturalness, relaxion… None of these is in terribly good shape. But interesting, could develop into something better.

• Why so many models?

Because the situation is confusing.

• Future Colliders crucial in testing them.

Naturalness in SUSY

• LHC searches model dependent, many blind spots.
• 2000
• ~=
• ~=
• ~=
• ()

()

500 1000 1500 2000 500 1000 1500 2000

• ~

[]

• ~

[]

=

• ~

[]

• Testing fine-tuning down to percent level.

Testing naturalness: Supersymmetry

(GeV)

t ~

m

2000 4000 6000 8000 10000

(GeV)

1

χ ∼

m

5000 10000

(fb) σ Excluded

• 4

10

• 3

10

• 2

10

• 1

10 1

Boosted Top Compressed

Exclusion

s

CL

= 100 TeV s

• 1

dt = 3000 fb L

∫

= 20%

sys,bkg

ε = 20%

sys,sig

ε

LHC

Composite Higgs

Neutral naturalness: “twin”

Craig, Katz, Strassler, Sundrum Chacko, Goh, Harnik UV completion with composite Higgs: Low, Tesi, and LTW

Top partner T not colored. Higgs decay through hidden world and back

Neutral naturalness: “twin”

• Can be tested at LHC and Higgs factories.

Craig, Katz, Strassler, Sundrum Chacko, Goh, Harnik UV completion with composite Higgs: Low, Tesi, and LTW Zhang, Liu, LTW

Top partner T not colored. Higgs decay through hidden world and back

Mysteries of the electroweak scale.

Mysteries of the electroweak scale.

• How to predict/calculate Higgs mass?
• What does the rest of the Higgs potential look

like? Nature of electroweak phase transition.

• Is it connected to the matter anti-matter

asymmetry?

What we know now

h

Mysteries of the electroweak scale.

• How to predict/calculate Higgs mass?
• What does the rest of the Higgs potential look

like? Nature of electroweak phase transition.

• Is it connected to the matter anti-matter

asymmetry?

What we know now

h

Nature of EW phase transition

h

?

What we know from LHC LHC upgrades won’t go much further

“wiggles” in Higgs potential Big difference in triple Higgs coupling

Triple Higgs coupling at 100 TeV collider

Talk by Michele Selvaggi at 2nd FCC physics workshop

But, there should be more

• 1st order EW phase transition means there is

new physics close to the weak scale.

• Can be difficult to discover at the LHC.
• Will leave more signature in Higgs coupling.

V (h) = m2 2 h2 + λh4 + 1 Λ2 h6 + . . .

For example

m2h†h + ˜ λ(h†h)2 + m2

SS2 + ˜

aSh†h + ˜ bS3 + ˜ κS2h†h + ˜ hS4

˜ a ˜ a S h h h h

shift in h-Z coupling

c m2

S

(h†∂h)

2

δZh ∼ c v2 m2

S

For example

m2h†h + ˜ λ(h†h)2 + m2

SS2 + ˜

aSh†h + ˜ bS3 + ˜ κS2h†h + ˜ hS4

˜ b ˜ a ˜ a ˜ a ˜ a ˜ a S S S S S ˜ κ h h h h h h h h h h h h

˜ a ˜ a S h h h h

10 20 30 40 50 60 50 100 150 200 g111 SM

g111 Tc

8% - 13%- 30%- 50%-

shift in h-Z coupling

triple Higgs coupling

c m2

S

(h†∂h)

2

δZh ∼ c v2 m2

S

Probing EWSB at higgs factories

• = , ()/ > 0

= “” , ()/ > 1.3 = 1,

Good coverage in model space

Huang, Long, LTW, 1608.06619

Probing EW phase transition

• = , ()/ > 0

= “” , ()/ > 1.3 = 1,

Huang, Long, LTW, 1608.06619

HL-LHC

Conclusion

• LHC still has a lot to say.

15+ years of operation, 95+% of data to come. Need to think about how to new searches with this data.

• Beyond the LHC, we need future colliders to

address the open questions of the Standard Model.

extra

Nightmare scenario:

74

• 3
• 3
• 2
• 2
• 1
• 1
• 0.8
• 0.8
• 0.6
• 0.6
• 0.5
• 0.5
• 0.4
• 0.4
• 0.3
• 0.3
• 0.2
• 0.2
• 0.1
• 0.1

200 400 600 800 1000

• 4
• 2

2 4 6 8 mS [GeV] λHS

Singlet model with a Z2 S → − S h6 term generated at 1-loop order Only marginally visible.

Meade et al

Late comers will be spotted easily:

6/19/18

Pile-Up background, time spread 190 ps (beam property)

Zhen Liu LLP @ LHC LPC TOTW 35

LT2 LT1 Trigger ✏trig ✏sig ✏j

fake

Ref. EC 1.17 m 0.2 m DelayJet 0.5 0.5 10−3 [12] MS 10.6 m 4.2 m MS RoI 0.25, 0.5 0.25 5 ⇥ 10−9 [24]

EC : N PU

bkg = jLint✏EC trig

✓ ¯ nPU j inc ✏j,EC

fake f j nt

◆ ⇡ 2 ⇥ 107, MS : N PU

bkg = jLint✏MS trig

✓ ¯ nPU j inc ✏j,MS

fake f j nt

◆ ⇡ 50, (5)

Pile-up BKG: intrinsic resolution ~190 ps EC (30ps) cut: Δt > 1 ns BKG(EC-PU) ~ 1.3 MS (30ps) cut: Δt > 0.4 ns BKG(MS-PU) ~ 0.86 The detector time resolution for MS can be downgraded to hundreds of ps MS (200ps) cut: Δt > 1ns BKG(MS-PU) << 1 CMS timing module ATLAS MS LLP search

(without timing)

Late comers will be spotted easily:

6/19/18

CMS timing module ATLAS MS LLP search

(without timing)

Same-vertex hard scattering background, time spread 30 ps (precision timing)

Zhen Liu LLP @ LHC LPC TOTW 33

LT2 LT1 Trigger ✏trig ✏sig ✏j

fake

Ref. EC 1.17 m 0.2 m DelayJet 0.5 0.5 10−3 [12] MS 10.6 m 4.2 m MS RoI 0.25, 0.5 0.25 5 ⇥ 10−9 [24]

EC : N SV

bkg = jLint✏EC trig✏j,EC fake ⇡ 1 ⇥ 1011

MS : N SV

bkg = jLint✏MS trig✏j,MS fake ⇡ 4 ⇥ 105,

Hard collision BKG: detector time resolution ~30 ps EC (30ps) cut: Δt > 0.4 ns MS (30ps) cut: Δt > 1ns BKG(SV) << 1 The detector time resolution for MS can be downgraded to hundreds of ps MS (200ps) cut: Δt > 1ns BKG(MS-SV) ~ 0.11

Search based on EC

0. 0.5 1. 2 5 10 20 50 100 200 10-4 10-3 10-2 10-1 100

Δt (ns) 1/ / Δt /bin) delay at EC from LHC

Δt > 0.8 ns

Back ground dominated by pile up After timing cut:

#background ∼ 1

Search based on MS

Δt > 0.4 ns

After timing cut:

#background ∼ 1

0. 0.5 1. 2 5 10 20 50 100 200 10-4 10-3 10-2 10-1 100

Δt (ns) 1/ / Δt /bin) delay at MS from LHC

Pile up background smaller, shielded by HCAL etc.

∼ 50

Before timing cut: Further away, larger for signal.

Δt

Search based on MS

0. 0.5 1. 2 5 10 20 50 100 200 10-4 10-3 10-2 10-1 100

Δt (ns) 1/ / Δt /bin) delay at MS from LHC

Δt > 0.4 ns

#background ∼ 1

Pile up background smaller, shielded by HCAL etc. Further away, larger for signal.

Δt

no need for super good timing resolution

δt ∼ 200 ps

will do

Signal

SM SM X or SM X Y

SM SM X or SM X

ISR jet (time stamp) ISR jet (time stamp)

• 1. ISR jet provides the time for the hard collision
• 2. LLP decay before reaching timing layer.

measurement of Δt

background

ISR jet Trackless jet 1 Fake displaced obj

Time stamping PV

Trackless jet 2

No need to fake signal

ISR jet Trackless jet Fake displaced obj Time stamping PV

Time delay from resolution of timing detector. Time delay from spread of the proton bunch Same hard interaction Pile up ∼ 190 ps

Importance of precision measurement

• No clear indication where new physics might be.

Precision measurement can give crucial guidance.

• Lots of data still to come

Room to improve! Statistics and systematics.

• Will be a important part of the legacy of the

LHC.

LEP taught us a lot. LHC will do the same.

Higgs coupling vs direct search

Higgs couplings 3000/fb diboson 3000fb d i l e p t

• n

3

• f

b 1000 2000 3000 4000 5000 6000 7000 8000 2 4 6 8 10 12 mρ [GeV] gρ

Excluded by current Higgs Coupling measurements Reach of HL-LHC

Testing naturalness at 100 TeV pp collider Fine tuning: (MNP)-2

Why is Higgs measurement crucial?

• Naturalness is the most pressing question of EWSB.

How should we predict the Higgs mass?

• We may not have the right idea. No confirmation of

any of the proposed models.

• Need experiment!
• Fortunately, with Higgs, we know where to look.
• And, the clue to any possible way to address

naturalness problem must show up in Higgs coupling measurement.