Transcript The International Linear Collider – an overview of the physics motivation and theory James Stirling IPPP, University of Durham with acknowledgements to R Barbieri, J.

The International Linear Collider
– an overview of the physics
motivation and theory
James Stirling
IPPP, University of Durham
with acknowledgements to R Barbieri, J Ellis, D Miller
(ICHEP04), M Peskin (Victoria LCW), S. Dawson, R. Heuer
the most up-to-date reference…
The LHC-LC Study Group Report
Georg Weiglein et al.
www.ippp.dur.ac.uk/~georg/lhclc/
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Particle Physics 2004
gauge sector
flavour sector
EWSB sector
 mass sector
… and beyond?
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Particle Physics 2004
 mass
?
QCD
1
CKM
QCD 2
gauge sector
flavour sector
EWSB sector
 mass sector
pentaquarks
EWSB
… and beyond?
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discrepancies?
?
2.7
NuTeV
g-2
LEPEWWG 2004
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Higgs
limits?
SUSY
m t = 178.2  3.9 GeV
dark matter
 S (M Z ) = 0.1186  0.0027
m H = 114 -+4695 GeV
 2 = 15.8/13 df (prob = 26 %)
m H < 260 GeV (95% cl)
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particle physics
the key questions
1)
2)
3)
4)
5)
What is the origin of mass? Is it the Higgs mechanism or …?
What is the origin of the matter-antimatter asymmetry in the universe?
What are the properties of neutrinos?
Is there unification of particles and forces including gravity?
What is the dark matter?
2)  present and future B Factories
3)  solar, atmospheric, reactor, (super)beam, 0,
…, NuFact experiments
1), 4), 5)  high-energy colliders: Tevatron, LHC, ILC
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key issue: electroweak symmetry breaking
Scenarios include:
•
•
•
•
•
•
•
+ gauge unification
dark matter candidate
(MSSM and +variants)
+ ‘naturally’ consistent with PEW data
Supersymmetry
Higgs as Pseudo Goldstone Boson
Composite Higgs
but…
Little Higgs Models
Note: in •
all where
scenarios,
something
is the
Higgs?(or some
Technicolour
combination
of things)
mimic a light Higgs
•
where
are has
the to
superpartners?
• boson
embed
SMprecision
in large electroweak
gauge group
Higgsless models
in•the
(EWPO) fits!
“little hierarchy”
problem!
• Higgs as PGB
Extra dimensions
•
in mh2 cancel top loop with new heavy T quark
then…
…
• new quarks,
gauge bosons, Higgs bosons in
NMSSM with heavier h0 , more neutral
The Calculability Principle (Barbieri):
the 1 – 10 TeV range
scalars etc.
Restrict to models in which the
Fermi scale (GF-1 or MZ) can be related to
but…
some other physical scale (NP
in a calculable
manner, i.e. MZ = NP
• say)
too many
such models?
f(ai) where the ai are physical •parameters.
Then
too ad hoc?
WJ Stirling
CP  consistency with
data  SUSY, Higgs as PGB
nevertheless…
at the very least, a useful “straw-man” alternative
toECFA
SUSY!
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what LHC can do: SM-like Higgs
fb-1
1 year
@1034
1 year
@1033
1 month
@1033
LHC: ATLAS
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what LHC can do: SUSY
Higgses
sparticles
 whole plane covered for at least one
Higgs (but note large “only h” region!)
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 squark and gluino masses
eventually up to ~2.5 TeV
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•
•
•
•
•
however…
‘hadro-philic’ bias in new physics searches (gg,qq  X)
large SM backgrounds always a problem (Higgs< total  10-9)
EWPO: only modest improvement over Tevatron (mtop , mW )
no longitudinal momentum balance; ‘missing pT’ for invisible
particles is relatively crude tool; quark flavour tagging difficult
strong model dependence of new physics analyses:
conventional SUSY
multiple hypotheses,
distinguished by
different spin and
energy flows, difficult
to distinguish at LHC
neutrino LSP (Murayama et al)
‘bosonic supersymmetry’
(Cheng, Matchev, Schmaltz)
Peskin (Victoria, 2004)
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cross sections: LHC vs. ILC
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ILC physics summary
whatever the scenario unveiled by Tevatron & LHC, ILC has
an essential role to play
•
•
•
•
continue with precision electroweak measurements (in
particular, mtop )
if a light Higgs exists, measure its properties (mass,
couplings to fermions & gauge bosons, self-couplings, …)
if LHC reveals other light ( e.g. SUSY) particles, measure
the spectrum and properties
if LHC reveals no light particles, explore the ~1 TeV region
through precision measurements sensitive to virtual new
physics
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precision
MW = cosw MZ  [ 1 + α F(mt,MH,SUSY,..)+ …]
W
b
+
mW (MeV)
mtop (GeV)
sin2eff105
now
34
3.9
17
TeV Run 2
16
1.4
29
LHC
15
1-2
14-20
ILC-GigaZ
7
0.1
1.3
t
H
+ …
Heinemeyer et al (LHCLC report)
current MW
Heinemeyer, Weiglein 04
precision contd.
precision EW
measurements
complement direct new
physics measurements
Heinemeyer et al 2003
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Higgs physics at ILC
Key questions
• precise mass?
• couplings to other particles – SM or not?
• self-couplings?
• other higgses?
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Higgs physics at ILC
Key questions
• precise mass?
• couplings to other particles – SM or not?
• self-couplings?
• other higgses?
compare
with
Guasch, Hollik, Penaranda 2003
Example:
R
BR(h  bb )
BR(h     )
also ttH coupling measurements
– see LHCLC report
Higgs physics at ILC
Key questions
• precise mass?
• couplings to other particles – SM or not?
• self-couplings?
• other Higgses?
V() = ½ mh2 2 + 3 v 3 + ¼ 4 4
in SM: 3 = 4 = ½ mh2 v-2
Z
e
Z*
h
e
h
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 3 / 3 ~ 20%
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supersymmetry at the ILC
the task:
• determination of kinematically
accessible sparticle spectrum
• measure sparticle properties (masses,
cross sections, JPC)
• use these (with complementary
information from LHC) to constrain
underlying SUSY model
• extrapolate to GUT scale using RGEs
the techniques:
• end point spectra
• threshold scans
• + e-e-, e, polarised beams
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example of a global MSSM spectrum fit
*
*
+
*
*
*
LSP
*
+
*
+
+
+
-
* Needs > 500 GeV. (Also < 500 study in LHC/LC)
David Miller, ICHEP04
+ e+e- threshold scan.
- e-e- threshold scan (s-wave allowed)
the LHC-LC synergy:
using precisely measured
LSP mass at ILC to
constrain LHC
measurements of slepton
and squark masses
see e.g. LHCLC report for details, many more examples, and references
… then on to the GUT scale!
Allanach, Blair, Kraml, Martyn, Polesello, Porod,,Zerwas
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… and if nothing below 500 GeV?
a generic feature of
such models is heavy schannel resonances in
the 1-3 TeV range
t
W
b
+
h
+
?
little Higgs
heavy Higgs
no Higgs
…
(new gauge bosons, technipions,
KK resonances, …)
f
e
W
e
Z’
Z’
e

WL
e
e
f
W
e

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WL
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sensitivity to new heavy
resonances in ee WW
sensitivity to new heavy Z’
LC
ILC (eeff)
LHC (direct)
LHC
assume a1=1
M = 1.9 TeV
SM couplings (a=1)
LC: 500 GeV, 500 pb-1
Richard 2003
Barklow et al, LHCLC report
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David Miller
ICHEP04
Summary of the case for the TeV ILC
1. Definite; mt<100MeV
Vital constraint.
Increasingly sure
it can be done.
2. If there is a light Higgs
LHC probably sees.
ILC shows what it is.
3. and extra particles
4. If LHC sees nothing new
below ~ 500 GeV mass
ILC looks beyond
LHC’s direct reach
Then LHC + ILC
point to CLIC, and
maybe superLHC
LHC and ILC needed to
pin down model, identify DM(?),
extrapolate to GUT scale.