The Physics Case for Particle Colliders at Energies Beyond LHC - - PowerPoint PPT Presentation

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The Physics Case for Particle Colliders at Energies Beyond LHC - - PowerPoint PPT Presentation

Feb 13, 2024 371 likes •617 views

The Physics Case for Particle Colliders at Energies Beyond LHC Snowmass 2013 Markus Luty University of California Davis Conclusions What unites us: focus on discovery Lepton and proton colliders are remarkably complementary A

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SLIDE 1

The Physics Case for Particle Colliders at Energies Beyond LHC

Snowmass 2013 Markus Luty University of California Davis
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SLIDE 2

Conclusions

  • What unites us: focus on discovery
  • Lepton and proton colliders are remarkably
complementary
  • A choice between unknowns
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SLIDE 3

Conclusions (cont’d)

100 TeV pp machine:
  • Unprecedented reach for new physics,
but there are low-energy loopholes
  • Best guess: most sensitive probe of tuning
in SUSY High energy lepton machines:
  • Less energy reach, essentially no loopholes
  • Precision program (Higgs, top)
  • Best guess: most sensitive probe of tuning
in composite Higgs models
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SLIDE 4

The Standard Model

With the discovery of the Higgs, we have experimentally established a theory that can be consistently extrapolated to the Planck scale. Can we justify continued exploration with expensive particle colliders? There is no guarantee of discovery. We are exploring the unknown.
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SLIDE 5 New physics at TeV scale

Unanswered Questions

  • Dark matter
  • Unification
  • Naturalness
  • Inflation
  • Origin of masses and mixings
...
  • Matter-antimatter asymmetry
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SLIDE 6

Naturalness

Elementary scalars are unnatural
  • K. Wilson
1262 = 175992038487088835203904637364744757 – 175992038487088835203904637364728881
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SLIDE 7

Two Ideas

SUSY Compositeness (includes extra dimensions) tuning in standard model
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SLIDE 8

SUSY

The most successful paradigm for physics beyond the standard model Most general feature of spectrum: High scale SUSY breaking: RGE + unification Low scale SUSY breaking: gauge mediation ⇒ jets + MET signature
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SLIDE 9

SUSY at LHC

LHC run 1 searches: no sign of SUSY gluino mass [GeV] 800 1000 1200 1400 1600 1800 2000 2200 2400 squark mass [GeV] 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 Squark-gluino-neutralino model =8 TeV s ,
  • 1
L dt = 20.3 fb ∫ ATLAS Preliminary 0-lepton combined ) theory SUSY σ 1 ± ) = 0 GeV Observed limit ( 1 χ ∼ m( ) exp σ 1 ± ) = 0 GeV Expected limit ( 1 χ ∼ m( ) = 395 GeV Observed limit 1 χ ∼ m( ) = 395 GeV Expected limit 1 χ ∼ m( ) = 695 GeV Observed limit 1 χ ∼ m( ) = 695 GeV Expected limit 1 χ ∼ m( ) = 0 GeV Observed 1 χ ∼ ) m(
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7TeV (4.7fb LHC run 2 & HL-LHC: tremendous increase in reach Mass (GeV) 2 χ ∼ and 1 ± χ ∼ 100 200 300 400 500 600 700 800 Mass (GeV) 1 χ ∼ 100 200 300 400 500 600 700 ATLAS Simulation , 95% exclusion limit
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3000 fb discovery reach σ , 5
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3000 fb , 95% exclusion limit
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300 fb discovery reach σ , 5
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300 fb =14 TeV s [GeV] q ~ m 2000 2500 3000 3500 4000 [GeV] g ~ m 1500 2000 2500 3000 3500 4000 [pb] σ
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10
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10 [pb] σ Z axis discovery reach
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3000 fb discovery reach
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300 fb exclusion 95% CL
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3000 fb exclusion 95% CL
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300 fb 1/2 >15GeV HT = 14 TeV MET/ s = 0. LSP Squark-gluino grid, m Zn, sys=30% ATLAS Preliminary (simulation)
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SLIDE 10 [GeV] t ~ m 200 300 400 500 600 700 800 900 1000 [GeV] 1 χ ∼ m 100 200 300 400 500 600 Based on SUS-13-011 discovery reach σ Estimated 5 1 χ ∼ t → t ~ *, t ~ t ~ → pp 1-lepton channel
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8 TeV, 20 fb (scenario A)
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14 TeV, 300 fb (scenario B)
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14 TeV, 300 fb CMS Preliminary t = m 1 χ ∼
  • m
t ~ m W = m 1 χ ∼
  • m
t ~ m (b) [GeV] t ~ m 200 300 400 500 600 700 800 900 1000 [GeV] 1 χ ∼ m 100 200 300 400 500 600 Based on SUS-13-011 discovery reach σ Estimated 5 1 χ ∼ t → t ~ *, t ~ t ~ → pp 1-lepton channel
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8 TeV, 20 fb (scenario A)
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14 TeV, 300 fb (scenario B)
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14 TeV, 300 fb CMS Preliminary t = m 1 χ ∼
  • m
t ~ m W = m 1 χ ∼
  • m
t ~ m (b)

SUSY Naturalness?

Tuning: ⇒ My rough summary: LHC run 1: probes 10% tuning LHC run 2: 1% tuning HL-LHC: another factor of 4 Many sensitive stop searches...
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SLIDE 11

Scenarios

Discovery: we know what to do...
  • “We told you so”
  • Study the %#**! out of the signal
  • Assess what future facilities best leverage discovery
  • Drink champagne
No discovery: Do we keep going?

SUSY

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SLIDE 12

Cosmic Mysteries

1991: Limits on the cosmic microwave anisotropy were pushing the limits of cold dark matter cosmology... [H. Murayama Lepton-Photon 2013] COBE:
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SLIDE 13

Fine Tuning!

mit “Big Bang not yet dead but in decline” Nature 377, 14 (1995) Bang! A Big Theory May Be Shot” A new study of the stars could rewrite the history of the universe Times, Jan 14 (1991)

Times, Jan 14 (1991)

1% tuning
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SLIDE 14

SUSY at 100 TeV pp

5 10 15 20 25 30 35 5 10 15 20 25 30 35 m é g HTeVL m é q HTeVL 10 jet + MET events
  • T. Cohen, K. Howe, J. Wacker
LHC run 1 LHC run 2, HL-LHC 33 TeV LHC 100 TeV VLHC
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SLIDE 15

SUSY at Colliders

Tuning: Energy reach:
  • Hermetic “EW-ino scan”
  • Masses measured to 1%
  • Similar for sleptons
Best hope for making quantitative connection between collider MET and DM ⇒
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SLIDE 16

Compositeness

Version 2.0: Higgs as pseudo Nambu-Goldstone boson Tuning: from Higgs couplings How far can we probe? and precision EW
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SLIDE 17

Compositeness at Colliders

Draft

  • 300/fb
300/fb 3 TeV 3/ab VLHC can discover resonances to ??? Probes naturalness only indirectly
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SLIDE 18

Dark Matter

Motivates dark matter at TeV scale Thermal relic ⇒ observed value for collider production freeze-out, indirect detection direct detection
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SLIDE 19

DM at 100 TeV pp

Mass [GeV] χ 500 1000 1500 2000 2500 3000 3500 σ 1 2 3 4 5 6 Wino (8 TeV) Wino (14 TeV) Wino (100 TeV) Higgsino (8 TeV) Higgsino (14 TeV) Higgsino (100 TeV) > 450 GeV T E ,
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8 TeV, 40 fb > 900 GeV T E ,
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14 TeV, 3000 fb > 3000 GeV T E ,
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100 TeV, 3000 fb Monojet, MadGraph, Parton-Level, pp
  • M. Low, L. Wang [preliminary]
[GeV]
  • m
1 10 2 10 3 10 4 10 /s] 3 qq [cm
  • v> for
  • 95% CL limit on <
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10 Thermal relic value 2x FermiLAT bb LHC7, 5/fb LHC14, 300/fb LHC14, 3/ab pp33, 3/ab pp100, 3/ab CTA Halo CTA Fornax CTA Segue D8 SUSY WIMP Effective DM
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SLIDE 20

Leptons vs. Hadrons

VLHC ILC 250 10% 1% ILC 500 CLIC 1 TeV 10 TeV Precision Energy muon ILC 1000
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SLIDE 21

Data Makes us Smarter

19 MeV
  • systematics
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SLIDE 22

More Study Needed!

The ILC community has set the gold standard for documenting their machine and its physics reach. CLIC is also in good shape, but there are few studies for VLHC and muon collider. More such studies are needed as input to the decision about the next big step forward in the energy frontier.
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SLIDE 23

How do we Decide?

“Guaranteed discovery” is guaranteed mediocrity High energy lepton and proton colliders are extremely complementary Neither has a guarantee of discovery We have to decide. If X finishes its run and we have seen nothing beyond the measurements that are guaranteed, I will say: “We did the right thing.”