Phenomenology Beyond the Standard Modelat the LHC
due to a Higgs boson?
• Why so many types of matter particles?
• What is the dark matter in the Universe?
• Unification of fundamental forces?
• Quantum theory of gravity?
• “… an essential feature of [this] type of theory
… is the prediction of incomplete multiplets of
vector and scalar bosons”
not comment on its existence
• Discussed in detail by Higgs in 1966 paper
A Phenomenological Profile
Precision Tests of the Standard Model
Lepton couplings Pulls in global fit
It works!
• Sensitivity to top, Higgs masses:
• Preferred Higgs mass: mH ~ 100 ± 30 GeV
• Compare with lower limit from direct search at LEP:
mH > 114 GeV
• First attempts in 1990,
Estimating the Mass of the Higgs Boson
JE, Fogli & Lisi
Higgs Production at the
• Couplings proportional to masses (?)
• Important couplings through loops:
– gluon + gluon → Higgs → γγ
Higgs Decay Branching Ratios
July 4th 2012
Data from March 6th
• No indication of any significant deviation from
the Standard Model predictions JE & Tevong You, arXiv:1303.3879
• What is it?
Is it the right shape?
Is it the right size?
What is it ? • Does it have spin 0 or 2?
• Is it scalar or pseudoscalar?
• Is it elementary or composite?
• Does it couple to particle masses?
• Quantum (loop) corrections?
• Decays into γγ, so cannot have spin 1
• Spin 0 or 2?
spin 0 hypothesis
– angular distribution of γγ
Does the ‘Higgs’ have Spin Two ?
Vector boson + ‘Higgs’ combined invariant mass
very different for spins 0 and 2 JE, Hwang. Sanz & You: arXiv:1208.6002
The ‘Higgs’ probably a Scalar
• Pseudoscalar, graviton-like spin-2 disfavoured
• Discriminate spin 2 vs spin 0 via angular
distribution of decays into γγ JE & Hwang: arXiv:1202.6660
2+ disfavoured @
Monte Carlo
What is it ? • Does it have spin 0 or 2?
– Spin 2 very unlikely
• Does it couple to particle masses?
• Quantum (loop) corrections?
What is it ? • Does it have spin 0 or 2?
– Spin 2 seems unlikely, but needs experimental checks
• Is it scalar or pseudoscalar?
– Pseudoscalar disfavoured by experiment
• Does it couple to particle masses?
• Quantum (loop) corrections?
Supersymmetry?
Cutoff
c
a
• Rescale couplings: to bosons by a, to fermions by c
• Standard Model: a = c = 1 JE & Tevong You, arXiv:1303.3879
b bbar τ τ γ γ W W Z Z Global
Global Analysis of Higgs-like Models
• Rescale couplings: to bosons by a, to fermions by c
• ‘Wrong’ sign of c disfavoured JE & Tevong You, arXiv:1303.3879
What is it ? • Does it have spin 0 or 2?
– Spin 2 seems unlikely, but needs experimental checks
• Is it scalar or pseudoscalar?
– Pseudoscalar disfavoured by experiment
– No significant deviations from Standard Model
• Does it couple to particle masses?
• Quantum (loop) corrections?
It Walks and Quacks like a Higgs
• Do couplings scale ~ mass? With scale = v?
• Red line = SM, dashed line = best fit JE & Tevong You, arXiv:1303.3879
Global
fit
-10 GeV JE & Tevong You, arXiv:1303.3879
What is it ? • Does it have spin 0 or 2?
– Spin 2 seems unlikely, but needs experimental checks
• Is it scalar or pseudoscalar?
– Pseudoscalar disfavoured by experiment
– No significant deviations from Standard Model
• Does it couple to particle masses?
– Some prima facie evidence that it does
• Quantum (loop) corrections?
Loop Corrections ?
• γγ coupling ~ 1 σ high? JE & Tevong You, arXiv:1303.3879
What is it ? • Does it have spin 0 or 2?
– Spin 2 seems unlikely, but needs experimental checks
• Is it scalar or pseudoscalar?
– Pseudoscalar disfavoured by experiment
– No significant deviations from Standard Model
• Does it couple to particle masses?
– Some prima facie evidence that it does
• Quantum (loop) corrections?
Theoretical Constraints on Higgs Mass
• Large Mh → large self-coupling → blow up at low-energy scale Λ due to
renormalization
quartic coupling < 0
• Vacuum could be stabilized by Supersymmetry Degrassi, Di Vita, Elias-Miro, Giudice, Isodori & Strumia, arXiv:1205.6497
Vacuum Instability in the Standard Model
• Very sensitive to mt as well as MH
• Present vacuum probably metastable with lifetime >> age of the Universe
Degrassi, Di Vita, Elias-Miro, Giudice, Isodori & Strumia, arXiv:1205.6497
What else is there?
Jets + missing energy
O. Buchmueller, R. Cavanaugh, M. Citron, A. De Roeck, M.J. Dolan, J.E., H. Flacher, S. Heinemeyer, G. Isidori,
J. Marrouche, D. Martinez Santos, S. Nakach, K.A. Olive, S. Rogerson, F.J. Ronga, K.J. de Vries, G. Weiglein
0 1000 2000 3000 4000
m0[GeV]
1
With LHCb update
above pre-LHC, > 1.5 TeV
CMSSM
• The new particle is a scalar
• Couplings ~ Standard Model Higgs
• Elementary scalar a challenge for theorists
• Fits naturally within supersymmetry
What Next: A Higgs Factory?
To study the ‘Higgs’ in detail:
•The LHC
•A linear collider?
(Larger cross section at higher energies)
•A circular e+e- collider: LEP3, …
– A photon-photon collider: SAPPHiRE
• Current uncertainties in SM calculations [LHC Higgs WG] (important correlations)
• Comparisons with
What do you do?
experiments to look
something different