physics at the international linear...
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ILC Physics Why ILC? 1 of 27
Physics at the International Linear Collider
[Apology for no proper quotation]
Why ILC?
In recent years, all of the highest–energy particle accelerators have been collidingbeam facilities
e+e− SLC 90GeV 1989 − 1998e+e− LEP 90 − 210GeV 1989 − 2000pp Tevatron 1.8 − 2TeV 1988−pp LHC 14TeV 2007−
The ILC would be a successor to LEP and SLC at higher energy. What is it about
the results from these colliders that calls for a successor?
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Why ILC? 2 of 27
Their aim was to make precision tests of the Standard Model of electroweak/stronginteractions. This is a Yang–Mills gauge theory with the following ingredients:
Local gauge symmetry: SU(3)×SU(2)×U(1)
Unification of weak and EM interactions
Maximal parity violation
Spontaneous symmetry breaking
g2s /4π = 1/9, g2/4π = 1/30, g′2/4π = 1/99, 〈φ〉 = v = 246GeV
mW = gv/2, mZ = (g2 + g′2)1/2v/2, mγ,g = 0; mf = yfv/√
2
Z = cWW − sWB, γ = sWW + cWB with sW/cW = g′/g
Q = I3 + Y , QZ = I3 − Q sin2 θW
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Why ILC? 3 of 27
0
0.1
0.2
0.3
1 10 102
µ GeV
αs(µ
)
0
10
20
30
160 180 200
√s (GeV)
σW
W (
pb
)
YFSWW/RacoonWWno ZWW vertex (Gentle)only νe exchange (Gentle)
LEPPRELIMINARY
02/08/2004Measurement Fit |Omeas−Ofit|/σmeas
0 1 2 3
0 1 2 3
∆αhad(mZ)∆α(5) 0.02761 ± 0.00036 0.02768
mZ [GeV]mZ [GeV] 91.1875 ± 0.0021 91.1873
ΓZ [GeV]ΓZ [GeV] 2.4952 ± 0.0023 2.4965
σhad [nb]σ0 41.540 ± 0.037 41.481
RlRl 20.767 ± 0.025 20.739
AfbA0,l 0.01714 ± 0.00095 0.01642
Al(Pτ)Al(Pτ) 0.1465 ± 0.0032 0.1480
RbRb 0.21638 ± 0.00066 0.21566
RcRc 0.1720 ± 0.0030 0.1723
AfbA0,b 0.0997 ± 0.0016 0.1037
AfbA0,c 0.0706 ± 0.0035 0.0742
AbAb 0.925 ± 0.020 0.935
AcAc 0.670 ± 0.026 0.668
Al(SLD)Al(SLD) 0.1513 ± 0.0021 0.1480
sin2θeffsin2θlept(Qfb) 0.2324 ± 0.0012 0.2314
mW [GeV]mW [GeV] 80.425 ± 0.034 80.398
ΓW [GeV]ΓW [GeV] 2.133 ± 0.069 2.094
mt [GeV]mt [GeV] 178.0 ± 4.3 178.1
Winter 2004
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Why ILC? 4 of 27
Ecm [GeV]
σ had
[nb
]
σ from fitQED unfolded
measurements, error barsincreased by factor 10
ALEPHDELPHIL3OPAL
σ0
ΓZ
MZ
10
20
30
40
86 88 90 92 94
The theory of the Z reso-nance line shape is some-what sophisticated. The EWand strong radiative correc-tions must be included.
The final result agrees with
experiment at the parts–per–
mill level.
The beautiful experiments leave little room for doubt that EW interactions have abasic gauge symmetry SU(2)×U(1). This brings into focus the next question:
What is the agent that breaks this holy symmetry?
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Why ILC? 5 of 27
The Standard Model contains no dynamical mechanism for EWSB. It can onlybe explained by a new fundamental interaction operating at an energy scale of afew hundred GeV. Being ignorant of what the interaction is, physicists propose adescriptive theory by adding a SU(2) scalar doublet, yielding the Higgs boson.
The Higgs boson influences the structure of the W and Z, through the vertex
that gives these particles mass. Fitting the electroweak data, we can look for a
systematic shift due to a heavy Higgs boson. mhSM< 260 GeV (95% c.l.)
80.2
80.3
80.4
80.5
80.6
130 150 170 190 210
mH [GeV]114 300 1000
mt [GeV]
mW
[G
eV]
Preliminary
68% CL
∆α
LEP1, SLD Data
LEP2, pp− Data
0
1
2
3
4
5
6
10020 400
mH [GeV]
∆χ2
Excluded Preliminary
∆αhad =∆α(5)
0.02761±0.00036
0.02747±0.00012
incl. low Q2 data
Theory uncertainty
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Why ILC? 6 of 27
The Higgs boson(s) should be discovered at the LHC, if not before. From the LHC,we will also understand whether there are other new particles of comparable masswhich produce the physics of electroweak symmetry breaking.
Whatever the outcome of these experiments, the next step is to understand thephysics of electroweak symmetry breaking in detail.
To do this, we should apply the powerful experimental methods learned from LEP
and SLC to the Higgs boson and the new particles at a few hundred GeV energies.
International Linear Collider
e+e− with Ec ≥ 0.5 TeV and high luminosityEnergy scan ⊕ Beam polarization
Sensitive detectors ⊕ Precise theoretical predictions
LHC gives us a new global (mixed) picture.
ILC gives us new dynamic multi–dimensional total views.
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics References 7 of 27
Many materials for ILC physics
• ACFA LC report (2001)
• TESLA TDR (2001)
• LC resource book for Snowmass (2001)
• GLC project (2003)
• LC report from WWS (2003)
• LHC/LC note (2004)
• Response to ITRP questions (2004)
• Many LHC/LC related workshops
• · · ·
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Higgs 8 of 27
Once a Higgs–like particle is found, ILC can make precision measurements of itsbasic properties.
If the Higgs boson is the one to give masses to all the SM particles, we need toobserve proportionality between mass and coupling.
We need to measure Higgs self couplings as well to determine the shape of the
Higgs pot and to understand what makes the Higgs boson condense in the vacuum.
τ τ-
-+
+
(GeV)
10
10
1
-3
-2
10-1
SM
Hig
gs B
ra
nch
ing
Ra
tio
bb
ggcc
γγ
MH
W W
100 110 120 130 140 150 160 [GeV]Hm
110 120 130 140 150 160 170 180 190
(H,X
)2 g
(H,X
)2
g∆
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1(H,Z)2g
(H,W)2g
)τ(H,2g
(H,b)2g
(H,t)2g
HΓ
without Syst. uncertainty
2 Experiments-1
L dt=2*300 fb∫-1WBF: 2*100 fb
101 100
Mass (GeV)
0.01
0.1
1
Co
up
lin
g c
on
sta
nt to
Hig
gs b
oso
n (κι)
Coupling-Mass Relation
c τ
b
W Z
Ht
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Higgs 9 of 27
Spin and Self–couplings
s, GeV
cross
sec
tion, fb
0
5
10
15
210 220 230 240 250
s = 2
s = 0
s = 1
M* (GeV)
No. of
Even
ts
SM
H → Z*Z → (f1f–
1)(f2f–
2)MH = 150 GeV
Spin 1Spin 2
0
5
10
15
20
25
30
30 35 40 45 50 55 1.0 2.0 3.0
10
20Int (L) = 1 ab
−1
100% efficiency
sqrt(s) [TeV]
Mh = 120 GeV
Mh = 150 GeV
hhh−coupling sensitivityδλ/λ[%]
0.5 1.5 2.5
Pol−beam (eL)
At present, almost NOTHING is known about Higgs sector.
The profile depends on the new physics scenario at the TeV scale.
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Too Many BSM Scenarios 10 of 27
TOO many new physics scenarios with extra dimensions and symmetries
• In the case of high cut–off scale
z SUSY (fermionic dimensions): the most well–motivated and studied
– ???
• In the case of low cut–off scale
z Large extra dimension (bosonic dimensions)
– Extra symmetries
∗ Techni–color
∗ Little Higgs
∗ Higgsless
∗ ???
• Hybrids or much wilder thoughts??
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Too Many BSM Scenarios 11 of 27
Decisive principles and/or experiments DESPERATELY needed
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Precision matters. 12 of 27
Precision matters!!
• Single Higgs? Two Higgs doublets? Additional singlets or triplets?
• SUSY or/and extra–dimension? Composite?
• Type–I or II or III Yukawa couplings and flavor mixings?
• Why top is heavy? Special for the 3rd generation?
• CP violation in Higgs sector? ⇒ γγ mode
gtop/gtop(SM)
gW
/gW
(SM
)
MSSM prediction:
100 GeV < mA < 200 GeV
200 GeV < mA < 300 GeV
300 GeV < mA < 1000 GeV
LHC 1σ
LC 1σLC 95% CL
mH = 120 GeV
0.8
0.85
0.9
0.95
1
1.05
1.1
1.15
1.2
0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2
gtop/gtop(SM)
gW
/gW
(SM
)
MSSM prediction:
100 GeV < mA < 200 GeV
200 GeV < mA < 300 GeV
300 GeV < mA < 1000 GeV
LHC 1σ
LC 1σLC 95% CL
mH = 120 GeV
0.8
0.85
0.9
0.95
1
1.05
1.1
1.15
1.2
0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2 80.30 80.35 80.40 80.45MW [GeV]
0.2312
0.2314
0.2316
0.2318
sin2 θ ef
f
predictions for MW and sin2θeff
δmtexp
= 2.0 GeV
δmtexp
= 0.1 GeV
mh = 115 GeV, δ∆αhad = 7 10 5
MSSM(SPS1b)
SM
prospective exp. errors 68% CL:
LHC/LC
GigaZ
150 200 250 300 350 400 450 500MA [GeV]
115
120
125
130
135
mh [G
eV]
∆mhexp
mt = 175 GeV, tanβ = 5
theory prediction for mh
δmtexp
= 2.0 GeV
δmtexp
= 1.0 GeV
δmtexp
= 0.1 GeV
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Precision matters. 13 of 27
Precision mattered in the Universe as well!!
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Heavy Higgs Bosons 14 of 27
Model–independent searches!!!
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics SUSY 15 of 27
Supersymmetry at the ILC
SSB SUSY + World =
S-parameters
Masses and Mixings of S-particles
d σ (Production and Decay)
Planck or ?? SUSY Physics
(m , M , µ , tan β ) ?? 0 2 S-particles ∃
Couplings
= Experiments
= Theories
Model–independent methods
• End–point spectra• Beam polarizations• e−e− ⊕ γe ⊕ γγ modes
What can be achieved?
• SUSY breaking mechanism• Grand extrapolation
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics SUSY 16 of 27
LHC would discover SUSY phenomena quickly by 2009. However, the measure-ments at the LHC involve
Complicated cascade chainsLarge SM and other SUSY backgrounds
Model dependence of new physics analyses
Multiple hypotheses, distin-guished by different spins andenergy flows, DIFFICULT todistinguish at the LHC due tomissing/unfixed energies.
⇓
Model–independent analyses!!
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics SUSY 17 of 27
)10χm(
60 70 80 90 100 110 120 130 140 150
)Rl~
m(
110
120
130
140
150
160
170
180
190
200
⇑
An LHC/LC synergy
The precisely measured LSPmass at the ILC constrains theLHC measurements of sfermionmasses.
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics SUSY 18 of 27
Beam polarization Spinless?
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics SUSY and GUT 19 of 27
Masses
Couplings
Chirality
Mixing
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Grand extrapolation 20 of 27
1015 1016
Q [GeV]
24
25
Now &LC/GigaZ
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Cosmological connection 21 of 27
Dark Matter = LSP?
WMAP: 0.094 < Ωh2 < 0.128 (2σ)
WMAP: 7%
LHC: 15%
Planck: 2%
ILC: 3%
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Extra dimensions 22 of 27
Extra dimensions at the ILC
z How to tell LED signals from others?
• How to decide nature of extra dimensions?
z Size and shape (topology)?
– Non–commutative geometry?
• Possible probes
z Quantum gravity effects (KK modes)?
– Brane excitation (KK modes of SM par-ticles)?
– Classical gravity effects (Black holes)?
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Extra dimensions 23 of 27
Impossible in SM
Cleanest way to test J=2
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Extra dimensions 24 of 27
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Conclusions 25 of 27
Conclusions
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Conclusions 26 of 27
c© The test of the 2nd (right) pillar of the SM - symmetry breaking and massgeneration - is the most important and urgent problem to solve.
c© The sub–TeV ILC will be crucial to carry out this mission and hence we needit regardless of the BSM scenarios.
c© To what extent the ILC will be able to explore the BSM depends on its scaleand thus luck.
c© If its scale is not too high, ILC [along with LHC ⊕ · · ·] can do a lot:
– Precision super–spectroscopy to test SSB mechanism
– Measurement of size and shape of LED
– Cosmological ⊕ low–high ⊕ CP–Baryon connections
z Certainly, unexpected phenomena are highly expected as history has taught us!
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)
ILC Physics Conclusions 27 of 27
2nd KILC @ Dec/28, 2004 in Pohang S.Y. Choi (Chonbuk)