Physics @ LHC (Physics @ TeV). Status of LHC/ATLAS/CMS and Physics explored at LHC. Fundamentalist of High Energy Physics (U. Tokyo).  Origin of Mass (Higgs). SSB of Higgs Potential gives mass to Gauge boson W/Z: (Freedom of ξ) Motion in η is corresponding to Higgs boson.
Status of LHC/ATLAS/CMS and
Physics explored at LHC
Fundamentalist of High Energy Physics (U. Tokyo)
SSB of Higgs Potential
gives mass to Gauge boson W/Z: (Freedom of ξ)
Motion in η is corresponding to
Simulated H→γγ events
Higgs boson will be observed
at LHC like this event (simulation)
[3-1] Production processes of SM Higgs at LHC
Vector Boson Fusion
GF & VBF are important for discovery:
Cross-section of ttH/bbH is small, but
give the direct information of Yukawa yt/yb.
Associate production with t/b
Vector Boson Fusion (1998Zeppenfeld et al.)
VBF has an excellent potential because of :
(1) Scattered “high Pt” jets are observed in the forward regions. Pt 〜 Mw
(2) There is rapidity gap between two
jets because there is no color exchange.
Only the products from Higgs are observed in the central region.
These are very promising signatures in order to suppress the background.
Number of jets
the SM at LEP suggests
[3-2] Decay Branching Fraction
In such a light region,
there are 5 important
H → γγBr is small of about 10-3,
Butpromising mode due to good resolution of γ
[3-3A] H→ γγin GF and VBF (small Br, but excellent Mγγ）
huge BG. S/N ~1% qq_bar→ γγis dominante
BG is High but also signal stat. is high
Two leading processes contribute to
three different event topologies:
S/N and shape of BG are different in 3 class.
Discovery potential of them are similar, and
we have good redundancy.
γ-ID and resolution are essential :
BG can be estimated with the side band.
Good S/N and flat BG
but Stat. limited
H→γγ indicates that spin
of Higgs is 0 (or 2). scalar
[3-3B] H→ZZ(*)→ ４leptons
Resolution and identifications of leptons are excellent.
Invariant mass distributions of 4 leptons are shown with BG contributions.
Irreducible BG is qq_bar → ZZ* → 4l (continuous distribution)
Reducible BGs are tt & Zbb (lepton comes from semileptonic decay of B
B contamination can be suppressed by isolation of track + anti-impact parameter
Track quality is essential for this mode )
ZZ*→ 4l has excellent discovery potential except for
M(H)<130GeV and M(H)=170GeV (Branching is small):
We can determine also CP, Spin of Higgs using this channel.
Origin of fermion
Tau decay includes neutrino, but
Momenta of ν’s can be calculated using mET information in the collinear limit.
Tau can be reconstructed !!!!
[3-3C] ＶＢＦ H→ττ
Resolution of mET is about 10GeV Mtautau has sharp peak (sigma 〜 10GeV)
Dominant Background process is Z(→tautau)+Njets. Peak appears at 91GeV.
Resolution and tail of mET distribution are essential for this channel
Higgs Spin0 (Yukawa)
[3-3D] VBF Ｈ→ WW
Leptonic decays of W lead to the event topology of
Leptons are emitted
in the same direction
Clear Jacobian Peak is observed:
tt → bb lνlν is main BG:
Leptons are back-to-back in tt.
Φ between di-lepton (Rad)
Similar Discovery potentials are obtained at both ATLAS and CMS
(Notice LO calculation vs NLO)
VBF γγ+ exclusive 1,2 jets analyses will gain significance in low mass regions
H->γγ, tautau covers the region < 130GeV, WW,ZZ > 130GeV
5sigma discovery is possible with L=10fb-1for both ATLAS and CMS
Different technologies are essential for various modes: (Safe and redundant)
Needed (Yukawa)Ldt (fb-1)
ATLAS + CMS
Let’s combine ATLAS+CMS performance
1 fb-1 for 98% C.L. exclusion
5 fb-1 for 5 discovery
over full allowed mass range
--- 98% C.L. exclusion
criticaltest can be performed for “origin of mass”
Relative coupling (Normalized to g(WH))
Mass can be measured
with accuracy of 0.1%
We can show couplings are proportional to their masses
We assume the
SM branching fractions except
for the leading five processes:
Br(H->tautau,tt,bb,ZZ and WW)
Within this assumption,
yt、yτ、yb, gZZH and gWWH
can be calculated.
yt、yτgZZH and gWWH 20%
Higgs Self-couplings (Yukawa)
In order to determine the shape of Higgs potential,
Slope of potential is correspond to Self-coupling
σ×Br is small
Need very High Luminosity
For 6000 fb-1(SLHC)
Dl ~ 19% for 170 GeV MH
Diphoton background is now computed at NLO (Yukawa)(Binoth et al, Eur.Phys.J.C16(2000)311, Bern,Dixon,Schmidt hep-ph/0206194, C.Balasz et al, Phys.Lett.B489(2000)157
1-6 (Yukawa)ＭSSM Higgsの発見能力
(t →H+b がcover)
この緑の部分は、HＳＭに似た性質のhが観測されるだけ。（SUSY decay )
 (Yukawa)Introduction and Conclusion:
Most important/urgent topics in Particle Physics are:
Understanding of “the origin of mass”
(EW symmetry breaking)
SSB of Higgs field is most promising scenario,
but should be examined directly: & determine the potential:
(2) Beyond the Standard Model
Supersymmetry is most promising,
Large Extra Dimension,
unexpected scenario… are also exciting.
These are main purpose of LHC project:
and LHC will give the clear solutions
2008 !! (Yukawa)
Appendix: Mt can be measured with accuracy of 0.9GeV,
Mw will be 15MeV(Very difficult task.
Z’ or high mass gauge boson 5TeV, Littele Higgs heavy top 1TeV