tmp.dviLinear Electron Positron Collider
Interpretation 1: Global Fits
Fermilab 03/05/2001
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 1
Introduction
boson (once it has been discovered at Tevatron or
LHC) is the key to understand electro–weak symmetry
breaking and the origin of mass.
Higgs Bosons have a very rich phenomenology. We
need a Higgs factory to address all essential elements
of the Higgs mechanism. Such a Higgs factory should
offer:
Well defined initial state
) An Electron–Positron Linear Collider !
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 2
The TESLA Collider
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 3
The TESLA Machine
max. Energy 500 GeV (Phase 1) ... 800++ GeV (Phase 2)
Luminosity 3.4 1034 ... 51034cm2s1
Polarization Electrons 80%, Positrons 40–60%
Bunchsize@IP 5 / 553 nm ... 2 / 391 nm ( ! Beamstrahlung)
Options , e , ee
Giga Z
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 4
The TESLA Machine
achieved in 9-cell cavities
in single-cell structures
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 5
Beamstrahlung
field of the other bunch
dE N2
GeV
Collimator
– 0:6 10 5e+e-pairs per bunch crossing
– 1 hadronic event ( ! hadrons) per 10 bunches
– secondaries (neutrons, ...)
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 6
Beamstrahlung II
and secondaries ) Mask
recognize them!
(similar to ISR)
N
Battaglia
Schulte
(2000)
Monig
Ohl
(1999)
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 7
A Detector for TESLA
take advantage of new technologies and LC goodies
(e.g. beampipe radius 1 cm)
design driven by Higgs physics in many aspects:
– Vertex-Detector
– Calorimetry
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 8
A Detector for TESLA
0
50
100
150
200
250
generated measured
generated
measured

Flavour Tag
”LEP” ”TESLA”
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 9
The Profile of the Higgs Boson
Production Processes
350 GeV 500 GeV 800 GeV
mH = 120 74000 35000 27000
mH = 160 52000 29000 24000
mH = 250 5500 16500 19000
500 fb1 500 fb1 1000 fb1
350 GeV 500 GeV 800 GeV
mH = 120 15500 37500 158000
mH = 160 7500 25000 126000
mH = 250 6500 8000 71000
500 fb1 500 fb1 1000 fb1
350 GeV 500 GeV 800 GeV
mH = 120 – 90 2600
350 GeV 500 GeV 800 GeV
mH = 120 – 80 160
mH = 160 – 20 120
mH = 250 – – 30
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 10
Observation
0
50
100
150
200
250
300
350
Z0 Recoil Mass (GeV)
WW
ZZ
(a)
) independent of Higgs decay
HZ=HZ 2%
(350 GeV/ 500 fb1)
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 11
Mass Measurement
0
50
100
mm HH [[ GeVGeV ]]
E ve
nt s
/ G eV
m H [GeV ]
m=m 3 5 104
(350 GeV/ 500 fb1, weakly dependent on mH )
HZ ! qq`+` HZ !W+W`+`
HZ ! bbqq HZ !W+Wqq ! 6jets
TESLA TESLA
TESLA TESLA
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 12
Spin and CP Quantum Numbers
Observation of H ! or ! H ) Spin 6= 1
dependence of HZ cross section at threshold
s (GeV)
cr os
s se
ct io
n (f
Angular distributions of the fermions in ZH ! f fH
chisquared/df
0
10
20
30
40
50
60
(b)
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 η
<O >
<O>
NLC TESLA
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 13
Higgs Couping to Gauge Bosons
unambigous gHZZ coupling from e+e ! HZ using
recoil mass method
1
1.5
2
SM prediction
500 GeV
350 GeV
σ Zh →
µµ X(fb
1. WW–fusion cross section e+e ! He nue
2. Branching ratio BR( H !W+W)
WW–Fusion:
s = 500 GeV
NLC
TESLA
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 14
Higgs Couping to Gauge Bosons
disentangle Higgsstrahlung and WW–Fusion through
different spectra in missing mass:
Missing Mass (GeV)
(ee ! Hee) (2) 2.8% 3.7% 13.0%
BR(H !WW ()) (1) 5.1% 2.5% 2.1%
BR(H ! ZZ()) (1) 16.9%
NLC
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 15
Higgs ”Coupling” to Photons
Branching ratio into photons:
0
500
1000
1500
2000
2500
3000
MH=120 GeV Lγγ(0.65<z<zmax)=43 fb-1
background
NLC
TESLA
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 16
The Total Higgs Decay Width
For mH < 2mZ the total width H is too small (in the SM)
to be measured directly ) Semi–direct method:
BR(H ! X) = partial(H ! X)
BR(H ! ) measurement.
(WW ! H) and BR(H !WW ) .
(3) X = WW in decay and X = ZZ in production
(e+e ! HZ) and assume gHZZ = gHWW cos W .
Option 120 GeV 140 GeV 160 GeV
(1) 23%
500 fb1 at 500 GeV
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 17
Higgs Coupling to Fermions
main task:
use simultaneous binned
of three tagging variables
TESLA
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 18
Higgs Coupling to Fermions
decay mode mH = 120 GeV mH = 140 GeV
H ! bb 2.4% 2.6%
H ! cc 8.3% 19.0%
H ! gg 5.5% 14.0%
H ! 20%
NLC study (J. Brau et al.) at p s = 500 GeV yields
almost consistent numbers (some details to be under-
stood)
for 500 fb1 at p s = 350 GeV
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 19
Higgs Coupling to top-Quark
(8 fermions!)
states using an ANN
! need high luminosity and high energy
σ(e+e− → tt _ H) [fb]
√s = 800 GeV
√s = 500 GeV
ttH=ttH 11%
for MH = 120 GeV, p s = 800 GeV, 1000 fb1
TESLA
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 20
The Higgs Potential
e+e ! qqbbbb and
e+e ! `+`bbbb
needs very efficient b-tagging and
jet reconstruction (energy flow measurement)
100 120 140 160 180 0
0.2
0.1
0.3
σ [fb]
HHH=HHH 20%
for mH = 120 GeV, p s = 500 GeV, 1000 fb1
TESLA
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 21
Interpretation 1: A Global Fit
How to make most efficient use of the whole set of mea-
surements? ) a global fit (HFITTER).
Include experimental correlation between the different
measurements. Theoretical uncertainties could be (but
are not so far) included into the fit.
mH 120 GeV 140 GeV
gHZZ 1 % 1 %
gHWW 1 % 2 %
gHbb 2 % 2 %
gHcc 3 % 10 %
gHtt 3 % 6 %
gH 3 % 5 %
gHWW 3 % 4 %
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 22
Interpretation 1: Global Fit
a)
0.8
0.85
0.9
0.95
1
1.05
1.1
1.15
1.2
gW/gW(SM)
a)
0.8
0.85
0.9
0.95
1
1.05
1.1
1.15
1.2
gc/gc(SM)
400 GeV < mA < 600 GeV
600 GeV < mA < 800 GeV
800 GeV < mA < 1000 GeV
LC 1σ LC 95% CL
mH = 120 GeV
gc/gc(SM)
400 GeV < mA < 600 GeV
600 GeV < mA < 800 GeV
800 GeV < mA < 1000 GeV
LC 1σ LC 95% CL
mH = 120 GeV
gW/gW(SM)
400 GeV < mA < 600 GeV
600 GeV < mA < 800 GeV
800 GeV < mA < 1000 GeV
LC 95% CL (w/o fusion)
LC 1σ (w/o fusion)
LC 1σ (with fusion)
mH = 120 GeV c)
gW/gW(SM)
400 GeV < mA < 600 GeV
600 GeV < mA < 800 GeV
800 GeV < mA < 1000 GeV
LC 95% CL (w/o fusion)
LC 1σ (w/o fusion)
LC 1σ (with fusion)
mH = 120 GeV c)
gtau/gtau(SM)
MSSM prediction
gtau/gtau(SM)
MSSM prediction
0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 23
Interpretation 2: Supersymmetry
10
20
30
40
50
50 100 150 200 250 300 350 400 450 500
0 h
-1
is it supersymmetric ?
can one determine SUSY parameters ? ( ) mA ?)
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 24
Distinguish SM from MSSM
In the MSSM the Decay Branching Ratios differ from the SM
values. Even without seeing the heavy Higgs Bosons SM and
MSSM can be distiguished.
...but the reach in mA depends on the SUSY parameters.
Carena, Logan et al.
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 25
Distinguish SM from MSSM
and even mA can be indirectly estimated:
K. Desch Higgs Boson Precision Studies at a Linear Electron Positron Collider , Fermilab, 03/05/2001 Page 26
Conclusion
The experimental status in 2012 (PDG) might look like that:
Let’s do these measurements!
We know how to do them (machine, detector, analysis)
We know many ways how to interpret them (theory)
We do not know a more promising way to obtain this
important insight into microscopic physics.
E.Gross