1. Physics at future HEP colliders
LIA F-J+K-PPL
Bordeaux
May 27, 2013
Dirk Zerwas
LAL Orsay
Introduction
Higgs
BSM
Top
Conclusions

2. Introduction The event:
prediction of the Higgs boson (Brout, Englert, Higgs) in the 1960s
discovery of the Higgs boson by ATLAS and CMS in 2012
Good news: observation of a new particle
Better news: opportunity to study new particle

3. Future colliders
HL-LHC and ILC
shorter time scale + P5 report + Jacques Martineau + Nicolas Alamanos)
longer timescale CLIC
newer proposals: FCC and TLEP
Type s
∫Ldt
HL-LHC pp
14TeV
3000fb-1
ILC
e+e-
90GeV-1TeV
250fb-1 – 1000fb-1
CLIC
3TeV
500fb fb-1
FCC
100TeV
TLEP
90GeV-350GeV
10000fb-1 – 2500fb-1
In a nutshell:
hadron machines:
high s achievable
PDFs
sensitivity to direct production of new particles with large masses decay channel dependent
QCD (theoretical predictions)
lepton machines:
LAB = CM frame (beam energy constraint)
small theory errors
sensitivity in precision (sub-%) measurements

4. Letting the Higgs sector tell us about new physics
Definition: ΔX deviation of XXH coupling from SM value:
gXXH= gX gXSM (1+ΔX)
Loop induced coupling:
gXXH=gX gXSM (1+ΔXSM+ΔX)
Different models:
without anomalous effective couplings
with anomalous effective couplings (meaning: new physics possible in a loop)
As observables are in gj2 : expected ambiguity for -2 and 0
+ couple the 2nd and 3rd generation quarks
Measurements at LHC:
σ · BR · L · ~ g2 · g2/Γ
blind to simultaneous coupling/√width changes
Essential: decay and cross section calculation

5. The Higgs sector
w and w/o effective couplings (no effective couplings lead to a slight increase of precision by construction)
ΔZ/W Δτ/b Δb/W:
coupling ratio
error reduced:
+correlation with Δb
ΔZ Δt Δb Δτ :
direct coupling
+correl with Δb
Tilman Plehn, Michael Rauch. arXiv: EPL and update Moriond/Aspen 2013
ΔZ Δt Δb Δτ Δγ:
effective coupling
additional contribution BSM
Higgs portal:
add a hidden sector
2-parameter model: ΔH = cosχ , Γhid

6. Enter the ILC Recoil technique: e+e-  ZH  μμ X
precise measurement of the Higgs boson mass
inclusive measurement of cross section
Taken from Snowmass report
qualitative game changer: inclusive measurement
qualitative change: distinguish c and top
typical experimental error: % level
quantitative game changer: gain on the theory error (0.5% Xsec ZH, WWH, 1% ttH)

7. The Higgs sector precision
ILC (250GeV):
great precision on ΔZ
but not an order of magnitude gain in others?
total width an issue:
σ*BR(ZZ) difficult (low BR)
width determined at 10% level via:
Cries for higher energy 
LHC+ILC combined analysis (…500GeV):
ILC only Gauss errors
clear improvement on Δt
some improvement on D5 couplings Δγ, Δg
LHCILC better than each machine alone

8. ILC up to 1TeV
ILC errors dominated by branching ratio errors (2% for b-quarks, mass induced)
gain in the statistics limited couplings
Theory errors on BR are important!
non-measurement of Δt means determination via Δc, theory error 3x reflected in deterioration of precision
cascades into Δg
impacts the total width
ILC+ expected errors will be sensitive to new models:
Gupta, Rzehak, Wells: Phys.Rev. D86 (2012)

9. Supersymmetry fermion boson
has “no” problems with radiative corrections (quadrat. div.)
has a light Higgs Boson (<140GeV)
interesting pheno at the TeV scale
3 (or more) neutral Higgs bosons: h, A, H
1 (or more) charged Higgs boson(s): H±
and supersymmetric particles
Many different models:
MSSM (low scale many parameters)
mSUGRA (high scale few parameters)
DSS (SUSY with heavy scalars)
GMSB
AMB
Additional (s)particles:
NMSSM
MRSSM/N=1/N=2 hybrid
and many more
spin-0
spin-1/2
spin-1
squarks:
qR, qL q
gluino: g g
sleptons:
ℓR, ℓL ℓ
h,H,A
neutralino χi=1-4
Z, γ H±
charginos: χ±i=1-2 W± ~ ~ ~ ~ ~
R-parity
production of SUSY particles in pairs
(Cascade-) decays to the lightest SUSY particle
LSP stable, neutral and weakly interacting: neutralino (χ1)
experimental signature missing ET
dark matter candidate (and we already found its supersymmetric Spin-0 partner!)

10. Search for Supersymmetry: with a little help from Planck
S. Henrot-Versille (LAL) and SFitter Phys.Rev. D89 (2014)
Fittino, MasterCode, BayesFits,….
mSUGRA:
mass of the Higgs boson restricts parameter space
couplings: no impact yet
relic density Ωh2 (Planck) restricts parameter space
MSSM (technically challenging 13 parameters):
mass of the Higgs boson restricts parameter space
couplings: no impact yet
relic density Ωh2 (Planck) restricts parameter space
SUSY parameter space restricted, but light and heavy regions available in mSUGRA and MSSM

11. Search for Supersymmetry: gluinos and squarks
Signature:
colored particles  large (pb) cross sections
many high transverse momentum jets
large missing ET, meff, momentum imbalance HT
Measure background from data (CRs)/
Extrapolate sensitive variable
many cross checks possible
no exciting deviations 
Equal squark and gluino masses: 1.4TeV

12. Search for Supersymmetry: 3rd generation
large mixing possible
could be lightest squarks
has a large impact on Higgs mass via RC
Exclusion up to 650GeV
BR can reduce sensitivity
watch for assumptions in simplified models
14TeV:
sensitivity to 2.5TeV colored sparticles
HL-LHC:
3TeV colored sparticles
ILC:
small mass differences

13. Search for Supersymmetry: Electroweak Sector
Signature:
associated production of charginos and neutralinos
supersymmetric version of WZ (difficult)
leptonic decays  3(and more) leptons
missing ET well described by SM 
MSSM limit
improve on LEP
LHC:
difficult scenario: limits of order 700GeV obtained with increased leptonic BRs (intermediate sleptons)
ILC:
less dependence on BRs
reach down to small mass differences
LSP could be very light

14. Measure Supersymmetry
LHC:
5% level mass measurement
HL-LHC:
improve to 1%
ILC:
electroweak sector measurements
precision 0.1%
LHC:
12fold ambiguity
ILC:
solves ambiguities
LHC
LHC:
hint on Parameter unification
HL-LHC:
increases precision
ILC:
“measurement” of unification
HL-LHC + ILC
Dark matter (deduced):
LHC:
% level with ambiguities
ILC:
0.1% level

15. Alternatives to Supersymmetry
Search for new physics:
virtual effect: deviations from the Standard Model
real effect: decay of a resonance
Sequential standard model:
Z’, W’ heavier version of Z and W
Modify couplings to get other variants
Search for a resonance
Randall Sundrum (RS):
warped Extra Dimensions
1 additional dimension (compactified)
Search for a Graviton resonance
decay: ee,μμ,γγ (mass reconstruction)
Arkani-Hamed, Dvali, Dimopoulos (ADD):
N ExtraDim macroscopic (LED)
Search for deviations wrt Drell-Yan

16. New “Standard Model” Particles
Signature (sequential) gauge boson (example):
Z’ decay to lepton (e,μ) pairs
bump in mass spectrum
Signature excited quark (example):
resonance decaying to di-jets
LHC 8TeV:
Z’ M>2.5…2.9TeV
excited quarks: M> 3.5 TeV
color octet scalars M> 2.5 TeV….
LHC 14TeV:
roughly double the reach in mass
contact interaction (ll 100fb-1): 31TeV
ILC precision measurements: 5-15TeV (indirect)
100fb-1 14TeV: discovery up to 4.5/5.5TeV

17. Top quark: mass
What if there are no new particles and no deviations? What about the top quark?
dominated (already) by systematic error
hard to go below 0.5GeV
perennial issue (below 0.5GeV) what kind of mass?
O(100MeV) conversion threshold mass to MSbar
precision of O(120MeV) achievable

18. Top quark mass and beyond
Electroweak top quark coupling
Top quark mass
influences the running of the quartic coupling of the Higgs boson:
to which scale can we go up?
is it the Planck scale (=desert)?
LAL/IFIC arXiv:
Study of weak couplings
difficult at LHC (strong production)
high precision possible at ILC

19. Conclusions Exciting times for particle physics:
will the Higgs boson reveal new physics?
will we see a dark matter candidate?
desert or paradise between EW and Planck scale?
stay tuned for HL-LHC and ILC

20. And at higher energies? Snowmass study: CMS projections (fusion error)
0.1% LCC error applied, Gauss (correl) everywhere
combinations dominated by the lepton colliders
kappa setup does not allow to determine new-physics effects in loop-induced couplings separately
HL-LHC + ILC is a great package for sub% level Higgs couplings