finding the higgs · finding the higgs robert harlander institute for theoretical particle physics...
TRANSCRIPT
Finding the Higgs
Robert Harlander
Institute for Theoretical Particle Physics
University of Karlsruhe
YETI’05, January 5–8, 2005
Robert Harlander — Finding the Higgs – p. 1
Guidelines
What are we looking for?
Higgs properties (Standard Model):
spin = 0
electric charge = 0
mass = ?
couples to mass!
H
t
p
X
X
g
p
=mt
v,
H= 2
M2V
v
Robert Harlander — Finding the Higgs – p. 2
Guidelines
What are we looking for?(. . . of course, anything new will make us happy. . . )
Higgs properties (Standard Model):
spin = 0
electric charge = 0
mass = ?
couples to mass!
H
t
p
X
X
g
p
=mt
v,
H= 2
M2V
v
Robert Harlander — Finding the Higgs – p. 2
Guidelines
What are we looking for?(. . . of course, anything new will make us happy. . . )
Higgs properties (Standard Model):
spin = 0
electric charge = 0
mass = ?
couples to mass!
H
t
p
X
X
g
p
=mt
v,
H= 2
M2V
v
Robert Harlander — Finding the Higgs – p. 2
Guidelines
What are we looking for?(. . . of course, anything new will make us happy. . . )
Higgs properties (Standard Model):
spin = 0
electric charge = 0
mass = ?
couples to mass!
H
t
p
X
X
g
p
=mt
v,
H= 2
M2V
v
Robert Harlander — Finding the Higgs – p. 2
Particle masses
t b c s τ µ e Z W± H
178 5 1.3 0.1 1.8 0.1 0.0005 91 80 . 250
≥ 115
Robert Harlander — Finding the Higgs – p. 3
Higgs search at LEP
direct:
Z(M = 91 GeV)
)E ~ 205 GeV( ~
Ze
He
+
_
Z*
⇒ MH = 114+69
−45 GeVMH < 260 GeV
Robert Harlander — Finding the Higgs – p. 4
Higgs search at LEP
direct:
Z(M = 91 GeV)
)E ~ 205 GeV( ~
Ze
He
+
_
Z*
⇒ MH & 114.4 GeV
⇒
MH = 114+69
−45 GeV
MH < 260 GeV
Robert Harlander — Finding the Higgs – p. 4
Higgs search at LEP
direct:
Z(M = 91 GeV)
)E ~ 205 GeV( ~
Ze
He
+
_
Z*
⇒ MH & 114.4 GeV
indirect: H+
e µ
_Z
+
_
e µ
0
1
2
3
4
5
6
10020 400
mH [GeV]
∆χ2
Excluded Preliminary
∆αhad =∆α(5)
0.02761±0.00036
0.02749±0.00012
incl. low Q2 data
Theory uncertainty
⇒ MH = 114+69
−45 GeV
MH < 260 GeV
Robert Harlander — Finding the Higgs – p. 4
Higgs search at LEP
direct:
Z(M = 91 GeV)
)E ~ 205 GeV( ~
Ze
He
+
_
Z*
⇒ MH & 114.4 GeV
indirect: H+
e µ
_Z
+
_
e µ
0
1
2
3
4
5
6
10020 400
mH [GeV]
∆χ2
Excluded Preliminary
∆αhad =∆α(5)
0.02761±0.00036
0.02749±0.00012
incl. low Q2 data
Theory uncertainty
⇒ MH = 114+69
−45 GeV
MH < 260 GeV
Robert Harlander — Finding the Higgs – p. 4
Higgs search at LEP
direct:
Z(M = 91 GeV)
)E ~ 205 GeV( ~
Ze
He
+
_
Z*
⇒ MH & 114.4 GeV
indirect: H+
e µ
_Z
+
_
e µ
0
1
2
3
4
5
6
10020 400
mH [GeV]
∆χ2
Excluded Preliminary
∆αhad =∆α(5)
0.02761±0.00036
0.02749±0.00012
incl. low Q2 data
Theory uncertainty
⇒ MH = 114+69
−45 GeV
MH < 260 GeV
Robert Harlander — Finding the Higgs – p. 4
Particle masses
t b c s τ µ e Z W± H
178 5 1.3 0.1 1.8 0.1 0.0005 91 80 . 250
≥ 115
Robert Harlander — Finding the Higgs – p. 5
Particle masses
t b c s τ µ e Z W± H
178 5 1.3 0.1 1.8 0.1 0.0005 91 80 . 260
≥ 114
Robert Harlander — Finding the Higgs – p. 6
Higgs Decay
b
b
HW
W
γ
γ
H
Z
HZ
ν
ν
W
W
l
H
_l
+
Robert Harlander — Finding the Higgs – p. 7
Higgs Decay
b
b
HW
W
γ
γ
H
l+
l_
_
+l
l
Z
HZ
ν
ν
W
W
l
H
_l
+
Robert Harlander — Finding the Higgs – p. 7
Higgs Decay
b
b
HW
W
γ
γ
H
q
q
_
+l
l
Z
HZ
ν
ν
W
W
l
H
_l
+
Robert Harlander — Finding the Higgs – p. 7
Higgs Decay
b
b
HW
W
γ
γ
H
ν
ν
W
W
l
H
_l
+
Robert Harlander — Finding the Higgs – p. 7
Higgs Decay
b
b
H
W
W
γ
γ
H
ν
ν
W
W
l
H
_l
+
Robert Harlander — Finding the Higgs – p. 7
Higgs Decay
b
b
HW
W
γ
γ
H
ν
ν
W
W
l
H
_l
+
Robert Harlander — Finding the Higgs – p. 7
Tevatron Discovery Potential
Robert Harlander — Finding the Higgs – p. 8
Tevatron Discovery Potential
currently:
Robert Harlander — Finding the Higgs – p. 8
Higgs search at the LHC
proton – proton collider
Robert Harlander — Finding the Higgs – p. 9
Higgs search at the LHC
proton – proton collider
Robert Harlander — Finding the Higgs – p. 9
Higgs search at the LHC
proton – proton collider
Robert Harlander — Finding the Higgs – p. 9
Higgs search at the LHC
H
t
p
X
X
g
p
gluon fusion ttH
Robert Harlander — Finding the Higgs – p. 10
Higgs search at the LHC
H
tg
gluon fusion ttH
Robert Harlander — Finding the Higgs – p. 10
Higgs search at the LHC
X
X
H
t
p
g
p
gluon fusion
ttH
Robert Harlander — Finding the Higgs – p. 10
Higgs search at the LHC
X
X
H
t
p
g
p
H
t
p
X
X
g
p
gluon fusion
ttH
Robert Harlander — Finding the Higgs – p. 10
Higgs search at the LHC
X
X
H
t
p
g
p
H
tg
gluon fusion
ttH
Robert Harlander — Finding the Higgs – p. 10
Higgs search at the LHC
X
X
H
t
p
g
p p
p
X
H
X
gt
gluon fusion ttH
Robert Harlander — Finding the Higgs – p. 10
Higgs search at the LHC
H
tg
H
tg
gluon fusion ttH
Robert Harlander — Finding the Higgs – p. 10
Higgs search at the LHC
H
Robert Harlander — Finding the Higgs – p. 11
Higgs search at the LHC
q
q
H
Robert Harlander — Finding the Higgs – p. 11
Higgs search at the LHC
X
H
pq
pq
X
VBF
Robert Harlander — Finding the Higgs – p. 11
Higgs search at the LHC
X
H
pq
pq
X
V
H
VBF
Robert Harlander — Finding the Higgs – p. 11
Higgs search at the LHC
X
H
pq
pq
X
Vq
qH
VBF
Robert Harlander — Finding the Higgs – p. 11
Higgs search at the LHC
X
H
pq
pq
X
q
q V
H
X
p
p
X
VBF Higgs Strahlung
Robert Harlander — Finding the Higgs – p. 11
Higgs search at the LHC
q
q
H
Vq
qH
VBF Higgs Strahlung
Robert Harlander — Finding the Higgs – p. 11
Diffractive Higgs Production
X
X
H
t
p
g
p
Robert Harlander — Finding the Higgs – p. 12
Diffractive Higgs Production
tp
p
X
X
H
g
Robert Harlander — Finding the Higgs – p. 12
Diffractive Higgs Production
p
p
pt
p
H
g
Robert Harlander — Finding the Higgs – p. 12
Diffractive Higgs Production
p
p
pt
p
H
g
signature: p ⊕ H ⊕ p (⊕ = rapidity gap)[Khoze, Martin, Ryskin][Boonekamp, de Roeck, Peschanski, Royon], . . .
Robert Harlander — Finding the Higgs – p. 12
Gluon Fusion vs. ttH
H
tg
H
tg
gluon fusion ttH
Robert Harlander — Finding the Higgs – p. 13
Gluon Fusion vs. ttH
H
tg
H
tg
gluon fusion ttH
s ≥ MH s ≥ 2mt + MH
Robert Harlander — Finding the Higgs – p. 13
Gluon Fusion vs. ttH
H
tg
H
tg
gluon fusion ttH
s ≥ MH s ≥ 2mt + MH
s = x1 x2s ∼ x2 s
Robert Harlander — Finding the Higgs – p. 13
Gluon Fusion vs. ttH
H
tg
H
tg
gluon fusion ttH
s ≥ MH s ≥ 2mt + MH
x ≥ 0.8 · 10−2 x ≥ 3.3 · 10−2
s = x1 x2s ∼ x2 s
Robert Harlander — Finding the Higgs – p. 13
Cross sections
σ(pp → H + X) [pb]√s = 14 TeV
NLO / NNLO
MRST
gg → H (NNLO)
qq → Hqqqq
_' → HW
qq_ → HZ
gg/qq_ → tt
_H
MH [GeV]
10-4
10-3
10-2
10-1
1
10
10 2
100 200 300 400 500 600 700 800 900 1000
tt
t
H
H
q
q
Vq
V
q
t
_t
H
q
q H
V_
V
Robert Harlander — Finding the Higgs – p. 14
Cross sections
σ(pp → H + X) [pb]√s = 14 TeV
NLO / NNLO
MRST
gg → H (NNLO)
qq → Hqqqq
_' → HW
qq_ → HZ
gg/qq_ → tt
_H (NLO)
MH [GeV]
10-4
10-3
10-2
10-1
1
10
10 2
100 200 300 400 500 600 700 800 900 1000
tt
t
H
H
q
q
Vq
V
q
t
_t
H
q
q H
V_
V
Robert Harlander — Finding the Higgs – p. 14
Cross sections
σ(pp → H + X) [pb]√s = 14 TeV
NLO / NNLO
MRST
gg → H (NNLO)
qq → Hqqqq
_' → HW
qq_ → HZ
gg/qq_ → tt
_H (NLO)
MH [GeV]
10-4
10-3
10-2
10-1
1
10
10 2
100 200 300 400 500 600 700 800 900 1000
tt
t
H
H
q
q
Vq
V
q
t
_t
H
q
q H
V_
V
Robert Harlander — Finding the Higgs – p. 14
Cross sections
σ(pp → H + X) [pb]√s = 14 TeV
NLO / NNLO
MRST
gg → H (NNLO)
qq → Hqqqq
_' → HW
qq_ → HZ
gg/qq_ → tt
_H (NLO)
MH [GeV]
10-4
10-3
10-2
10-1
1
10
10 2
100 200 300 400 500 600 700 800 900 1000
tt
t
H
H
q
q
Vq
V
q
t
_t
H
q
q H
V_
V
Robert Harlander — Finding the Higgs – p. 14
Gluon fusion: tt
t
H
largest cross section
gg → H → ZZ → 4µ: gold plated mode for MH & 135 GeV
Z
Z
_µ
+µ
+µ_
µ
t
H
X
p
X
g
p
sensitive to
new particles, e.g. supersymmetry: tt
t
H +~t
~
t~ H
t
top Yukawa coupling
Robert Harlander — Finding the Higgs – p. 15
Gluon fusion: tt
t
H
largest cross section
gg → H → ZZ → 4µ: gold plated mode for MH & 135 GeV
Z
Z
_µ
+µ
+µ_
µ
t
H
X
p
X
g
p
sensitive to
new particles, e.g. supersymmetry: tt
t
H +~t
~
t~ H
t
top Yukawa coupling
Robert Harlander — Finding the Higgs – p. 15
Gluon fusion: tt
t
H
largest cross section
gg → H → ZZ → 4µ: gold plated mode for MH & 135 GeV
Z
Z
_µ
+µ
+µ_
µ
t
H
X
p
X
g
p
sensitive to
new particles, e.g. supersymmetry: tt
t
H +~t
~
t~ H
t
top Yukawa coupling
Robert Harlander — Finding the Higgs – p. 15
Gluon fusion: tt
t
H
but:
gg → H → bb not useful!
Robert Harlander — Finding the Higgs – p. 16
Gluon fusion: tt
t
H
but: gg → H → bb not useful!
Robert Harlander — Finding the Higgs – p. 16
Gluon fusion: tt
t
H
but: gg → H → bb not useful!
particle mass (GeV)
σ rate ev/yearLHC √s=14TeV L=1034cm-2s-1
barn
mb
µb
nb
pb
fb
50 100 200 500 1000 2000 5000
GHz
MHz
kHz
Hz
mHz
µHz
1
10
10 2
10 3
10 4
10 5
10 6
10 7
10 8
10 9
10 10
10 11
10 12
10 13
10 14
10 15
10 16
10 17
LV1 input
max LV2 inputmax LV1 output
max LV2 output
σ inelastic
bb–
tt–
W
W→lνZ
Z→l+l-
ZSM→3γ
gg→HSM
qq–
→qq–HSM
HSM→ZZ(*)→4l
HSM→γγh→γγ
tanβ=2-50ZARL→l+l-
Zη→l+l-scalar LQ
SUSY q~q~+q
~g~+g
~g~
tanβ=2, µ=mg~=mq
~
tanβ=2, µ=mg~=mq
~/2
Robert Harlander — Finding the Higgs – p. 16
Gluon fusion: tt
t
H
but: gg → H → bb not useful!
need to rely on gg → H → γγ at MH . 135 GeV
Robert Harlander — Finding the Higgs – p. 16
Gluon fusion: tt
t
H
but: gg → H → bb not useful!
need to rely on gg → H → γγ at MH . 135 GeV
CER
N L
HC
Higgs physics
Some extensions of the Standard
Model involve a richer set of Higgs
bosons: in the Minimal
Supersymmetric SM there are five
new bosons (h0, H
0, A
0, H
+, H
-).
Their discovery involves the use of
more complicated signatures, such
as the identification of a jet as
coming from b quarks
Observability of the SM Higgs in CMS with 10
5 pb
-1. The CMS
detector can probe the entire mass range up to MH ~ 1 TeV with a signal significance well above 5σ
4. For the highest MH, in the range 0.5 - 1 TeV, the promising channels for 105 pb-1 are H0 → ZZ → �
+�–
νν, H0 → ZZ → �+�–
jj and H0 → W+W
– → �±νjj.
Detection relies on leptons, jets and missing transverse energy (Et
miss), for which the hadronic calorimeter( HCAL ) performance is very important
2-3. In the MH range 130 - 700 GeV the most promising channel is H0 → ZZ*→ 2�+2�
– or H0 → ZZ → 2�+2�–. The detection relies on the
excellent performance from the muon chambers, the tracker and the electromagnetic calorimeter. For MH ≤ 170 GeV a mass resolution of ~1 GeV should be achieved with the 4 Tesla magnetic field and the high resolution of the crystal calorimeter
10060
5
10
15
20
25
200 400 700
MH (GeV)
Sig
nific
an
ce
Standard Model Higgs
γγ
γγ + ≥ 2 jets
S= NS
NB
S= NS
NB
S= NS
NS + NB
H → ZZ, ZZ* → 4 ±
H → WW →
γγ
ν ν
H → ZZ → ν ν
40
35
30
Ne
ν/1
00 fb
–1/ 5
GeV
70
60
50
40
30
20
10
00 50
104.05
100 150 200 250
SM
M (bb), GeV
h → bb in mSUGRA
1. H0 → γγ is the most promising channel if MH is in the range 80 – 140 GeV. The high performance PbWO4 crystal electromagnetic calorimeter in CMS has been optimized for this search. The γγ mass resolution at Mγγ ~ 100 GeV is better than 1%, resulting in a S/B of ≈1/20. With larger data samples (≥ 105 pb-1) the "associated" modes (pp → WH0 and pp → ttH0) should give higher S/B ratios for the same H0 decay channel
8000
6000
4000
2000
080 100 120 140
Mγγ (GeV)
Higgs signal
Eve
nts
/ 5
00 M
eV
fo
r 10
5 p
b-1
H → γγ
MH ≤ 130 GeV
60
80
20
40
0100 120 140 160 180 200
M (4 ±) GeV
Eve
nts
/ 2
Ge
V f
or
Lin
t =
10
5 p
b-1
tt + Zbb + ZZ*
Et > 20,15,10,10 GeV;
pt > 20,10,5,5 GeV;µ
|ηe, | < 2.5, 2.4;µ
e
H → ZZ*→ 4 ±
130 ≤ MH ≤ 170 GeV 5
4
3
2
1
0 200 400 600 800 1000 1200 1400 1600 1800
H → ZZ → ��jjM
H= 800 GeV
M(��jj), GeV
Ne
v /
20
0G
eV
/ 3
*10
4 p
b-1
Signal
Bkgd
CENTRAL CUTS (Iη < 2.4):
Pl> 50 GeV/c Pz> 150 GeV/c
TAGGING JETS(IηI > 2.4):
1 cluster, No addit. jets with Pt > 40 GeV
I Mcl
- MZ
I < 15 GeVI Mll - M
Z I < 10 GeV
tt
I
2 jets with E > 400 GeV and Pt > 10GeV/c
The Standard Model (SM) of Particle Physics has unified the Electromagne-tic interaction (carrier: γ) and the weak interaction (carriers: W+, W–, Z0). Yet these four bosons are very different: the γ is massless whereas the W± and Z0
are quite massive (80 – 90 GeV). In the framework of the SM particles acquire mass through their interaction with the Higgs field. This implies the existence of a new particle: the Higgs boson H0. The theory does not predict the mass of the H0, but it does predict its production rate and decay modes for each possible mass. CMS has been optimized to discover the Higgs in the full expected mass range 0.08 TeV < MH < 1 TeV~ ~
The decay signature of the Higgs depends on its mass:
+
+
+
+
+
++
++
+
++
+
+
+
+
+
+
+
+
+
+
+
+
++
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
++
++
++++
++++
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
++
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
++
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
++
+
+
+
+
+
+
+
+
+
+
+
+
++
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
++
+
+
+
+
+
+
+
+ +
+ +
+
+
+ +
+ +++
+ +
+
++ ++
++
+ +
+
+
+
+
+
+
+ +
+
+++
++
+++++
+
+
+++++++
+
+
+
+
++
++
+
+
+
+
+ +
+ +
+
+
+
+
+
+
+
+
+
++
++
+
+
+
+
+
+
+ + +
+
+
+
+
+ + +
+
++
+
+
+ + +
+
+
+
+
+
+
+
+
+
++
+
++
++
+
+
+
+
+
+
+
+
++ +
++++
++
++
+++
+
+
+
+++++++
+ +
+
+
+ +
+++
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ +
+
+
++
+ +
+
++
++
+
+
+
+
+
+
+
+
+
+
+
+
+++
++
+
+
+
+
+ + +
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
++
+
+
+
+
+
+
+
+
+
+
+
+
+
+
++
++++
+
+++
++
++
++
+
+
+ +
+++
+
+ +
+
+
++
+
+
+
+
+
++
+
++++
+
+
++
+
++
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ +
+
+
+
+
++
+
++++
++
+
++
+
++
+
+
+++++
+++
++++
++
+++
+++
+++++++++++
+++++++++
++
++++++++
+++
++
+
++
+
+++
++++++
+++
++++++++++++
+
+
+
+
+
+
++
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
++++
+ +
+
+
+
+
+
+
+
+
+
+
+
+
+
+++
++
+
+
+ + +
+
+
+
+
+
+
+
+ +
+ +
+
+
+
+ +
+
+
++
++
+
+
+
+
+ +
+ +
+
+
+
++
+++
++
++
+
+++
++
+
++
+
++
+
+
++
+
+
+
+
+
+ +
+ +
+
+
+
+
+
++
+
+
+ +
++
+
++
+++++
++
+++++++
++
++
+
+
++
+
++
++
+
++
+
+ +
+ +
+
++
++
+ +
++
+
+
++
+
+
+
+
+
+
+++
+
++
+
+
+
+
+
+
+
+
+
++
+
+
+
+
+ +
+ +
+
+
+ +
+
++
++
+ +
+ ++
+
+
+
+
+
+
+
+
+
+
+
+
+++++++++
++++++++
++++++
+++++
++++++
+
++
+ +
++
+
+
+
+
+
+
+
+
+
+
+
++
+
+
+ +
+ +
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
++++
+
+
++
+
+
+
+
+
+ +
+
+
+
+
++
+
+
+ +
+
+
+
+
+++
++
+
+
+
++
+
+
++ ++ +
+
+
+
++
+
+
+ +
+++
+ ++
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
++
+
++
+
++
+
++
+
+
+
+
+
+
+
++
++
+
+
+
+
++
+
++
++
+
+
+
+
+
+
+
+
+
+
+
+
++
+
+
++
+
+
+
+
++
+
+
++
+ +
+
+
+
+
++
++
+++
+
+
+ +
+
+
++
++
++
+
+ +
+
+
+
+ +
+
+
+
++
+
+
+
+
+
+
+
+
+
+
+
+ +
+
+
+
+
+
+
+
+
+
+
+++
+
+ +
+
+
+
+
+
+
++
+
+
++
+
+
+
+
+++
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ +
+
++
+
+
+
+
+
+
+ +
+
+
++
+
+
+
++
+
+
+
+
+
+
+
+
+
+
+
+
+++
++
+++
++
+
+
+
+
+
+
+
+
+
+
+
+
+
+ +
+ +
++ ++++ +
+ +++ +
+
++
+ +
+ +
+
+
+
+
+
+
+
+
+
+
+
+ +
+ +
+
++
+
+
+
+
+
+
+
++
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
++
+
+
+
+
+
+
+
+
+
+
++ +
+++
+ +
++
+
+
++
+
+
++
+
+
+
+
+
+
+
+
+
+
+
+ + + +
++
++ +
+
+
++
+
+
++
+
+
+
+
+
+
+
+
+
+
+
+
+ +
+
+ +
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+ +
++
+
+
+++
+
+ +
+
+
+
+ ++
+
+
++
+
+
+++
+
+
+
+
+
+
++
+
+
+
+++
+++++++
+
+
++
+ +
+
+
+
+
++
+
+
+
+
+
+
+
++
++
+
++ +
+
++
++
++
+
+
+
++
+
+
+
+
++
+
+
++
+
+ +
+
+
++
+
++
+
+
+
+
+
+
+
+
++ +
+
+
+
+
+
+
+
+
+
+
+
+
++
+
+
+++ + +
+
+
+
+
+
+
+
+
+ +
+ + + +
+
+
+
+
+
+
+
+++
+
++
+
+++
+
++
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
++
++
+
+
+
+
+
+
+
+
+ +
+
+
+
+
+
+
+
+
++
+
+
++
+
+ +
++
+
+
+
+
+ +
++
+
++
+
+
+
+
+
+
+
++
+
+
+
+ +
+
+
+
+
+
+
++
+
+
+ +
+ +
+
+
+
++
+ +++
++
++++++
++
++
+
+
++++++
++ +
+++
+++
+
+ +
+
+
++
+
+
+ +
+
+
+ +
+
+ + +
+
+
++
+
+
+
+
+
+++
+
+
+
++
+
+
+ ++
+
+
+
+
+ + +
+
+
++
+
+
+ +
++
+
++
+++
+
++
+
++++
+
+
+
+
+
+
++
+
+
+
+
+
+
++
+
+
++
+
+
+ +
+
+++
+++
+ + + + ++ +
++ ++ +
+
+
+
+
+
+
+
+
+
+
+
++
+
+
++ + +
+ + + +
++
+
++
+
++
++
++
+
++
++
++
++
+ +
++
++
+
++
+
++
+
++
+
+
++
++
+
++++++
+++
++
++
+++
++
++++
+
++
++
+
++
++ +
+
+ +
++ ++ +
+
+
+
+
+ +
++
+
+
+
+
+
+
+
+
+
+ +
+
+
+
++
+ +
+
++
++
++
++
++
+
+
+
++
+
+
+
+
+
+
++
+
+
+
+
+
+
++ ++ +
+
++
+
+
++++++++++
++++
+
+
+
++
+
+
+
+++
+ +
++++++
+
+
+
+
+
+
+
+
+
+
+++
+
+
+
+
+
+
+
+
+
+ +
+
+
+
+ +
+
+
++
+
+
+
+++
+
+
+
++
++ ++
+
+
+ +
++
+
+
+
+
+
+
+
+
+++++
+
+
+
+
+
+
+
+
+
+
+++ +
+
+ + + + + ++ ++++ + +
+
++
++
+++
+
+++
+
+ ++
++ + +
+ + + + +
+
++ ++++ ++++++++++ +++++
++ ++
++ ++
+++ +
+ +
++
+
+ ++ ++
+++
+
++++++
+
++
++
++
++
+++
+++++++++++++++
+++
++
+++
+
+ + + + +
+ + ++
+++
+ +
++
+
+
+++
+
+
+
+
+
++++
++
++
+
+
+ +
+
+
+
+
+
+
++
++
++
++
+ ++
++
++
++
++
++
++
++
++
++
+
++++
+
+
+
+
421 H(800 GeV) →e+e- jet jet→ZZZZ*H(130 GeV) → e+e- e+e-→ 3 H(150 GeV) → µ+µ- µ+µ-→ZZ*H(100 GeV) → γ γ
Robert Harlander — Finding the Higgs – p. 16
Gluon fusion: tt
t
H
but: gg → H → bb not useful!
need to rely on gg → H → γγ at MH . 135 GeV
phase space is a single point: s ≡ M2H
Robert Harlander — Finding the Higgs – p. 16
Gluon fusion: tt
t
H
but: gg → H → bb not useful!
need to rely on gg → H → γγ at MH . 135 GeV
phase space is a single point: s ≡ M2H
NLO:Ht
t
t
⇒ phase space opens: s ≥ M2H
!
Robert Harlander — Finding the Higgs – p. 16
Gluon fusion: tt
t
H
but: gg → H → bb not useful!
need to rely on gg → H → γγ at MH . 135 GeV
phase space is a single point: s ≡ M2H
NLO:Ht
t
t
⇒ phase space opens: s ≥ M2H
!
⇒ large radiative corrections expected
Robert Harlander — Finding the Higgs – p. 16
Gluon fusion: tt
t
H
but: gg → H → bb not useful!
need to rely on gg → H → γγ at MH . 135 GeV
phase space is a single point: s ≡ M2H
NLO:Ht
t
t
⇒ phase space opens: s ≥ M2H
!
⇒ large radiative corrections expected→ reliable result requires NNLO
Robert Harlander — Finding the Higgs – p. 16
Gluon fusion: theory prediction
tt
t
H
1
10
100 120 140 160 180 200 220 240 260 280 300
σ(pp→H+X) [pb]
MH [GeV]
LO
√s = 14 TeV
[R.H., Kilgore ’02][Anastasiou, Melnikov ’02][Ravindran, Smith,
v. Neerven ’03]
[Spira, Djouadi, Graudenz,Zerwas ’91/’93]
[Dawson ’91]
Robert Harlander — Finding the Higgs – p. 17
Gluon fusion: theory prediction
tH
t
1
10
100 120 140 160 180 200 220 240 260 280 300
σ(pp→H+X) [pb]
MH [GeV]
LONLO
√s = 14 TeV
[R.H., Kilgore ’02][Anastasiou, Melnikov ’02][Ravindran, Smith,
v. Neerven ’03]
[Spira, Djouadi, Graudenz,Zerwas ’91/’93]
[Dawson ’91]
Robert Harlander — Finding the Higgs – p. 17
Gluon fusion: theory prediction
tH
t
1
10
100 120 140 160 180 200 220 240 260 280 300
σ(pp→H+X) [pb]
MH [GeV]
LONLONNLO
√s = 14 TeV
[R.H., Kilgore ’02][Anastasiou, Melnikov ’02][Ravindran, Smith,
v. Neerven ’03]
[Spira, Djouadi, Graudenz,Zerwas ’91/’93]
[Dawson ’91]
Robert Harlander — Finding the Higgs – p. 17
Resummation
[Catani, de Florian,Grazzini, Nason (’03)]
Robert Harlander — Finding the Higgs – p. 18
ttH
t
_t
H
clear signature: bbbbW+W−
[Beenakker, Dittmaier, Krämer,Plümper, Spira, Zerwas ’01]
[Dawson, Reina, Wackeroth,Orr, Jackson ’01-’03]
Robert Harlander — Finding the Higgs – p. 19
ttH
t
_t
H
clear signature: bbbbW+W−
direct handle on top Yukawa coupling
[Beenakker, Dittmaier, Krämer,Plümper, Spira, Zerwas ’01]
[Dawson, Reina, Wackeroth,Orr, Jackson ’01-’03]
Robert Harlander — Finding the Higgs – p. 19
ttH
t
_t
H
clear signature: bbbbW+W−
direct handle on top Yukawa coupling
but: rather small cross section
[Beenakker, Dittmaier, Krämer,Plümper, Spira, Zerwas ’01]
[Dawson, Reina, Wackeroth,Orr, Jackson ’01-’03]
Robert Harlander — Finding the Higgs – p. 19
ttH
t
_t
H
clear signature: bbbbW+W−
direct handle on top Yukawa coupling
but: rather small cross section
increased by QCD corrections?
[Beenakker, Dittmaier, Krämer,Plümper, Spira, Zerwas ’01]
[Dawson, Reina, Wackeroth,Orr, Jackson ’01-’03]
Robert Harlander — Finding the Higgs – p. 19
ttH
t
_t
H
σ(pp → tt_ H + X) [fb]
√s = 14 TeV
MH = 120 GeV
µ0 = mt + MH/2
NLO
LO
µ/µ0
0.2 0.5 1 2 50
200
400
600
800
1000
1200
1400
1
[Beenakker, Dittmaier, Krämer,Plümper, Spira, Zerwas ’01]
[Dawson, Reina, Wackeroth,Orr, Jackson ’01-’03]
Robert Harlander — Finding the Higgs – p. 19
ttH
t
_t
H
σ(pp → tt_ H + X) [fb]
√s = 14 TeV
MH = 120 GeV
µ0 = mt + MH/2
NLO
LO
µ/µ0
0.2 0.5 1 2 50
200
400
600
800
1000
1200
1400
1
[Beenakker, Dittmaier, Krämer,Plümper, Spira, Zerwas ’01]
[Dawson, Reina, Wackeroth,Orr, Jackson ’01-’03]
Robert Harlander — Finding the Higgs – p. 19
Vector Boson Fusion
H
q
q
Vq
V
q
signature: two forward jets + HiggsH → γγ, H → τ+τ−, H → WW , H → bb
Robert Harlander — Finding the Higgs – p. 20
Vector Boson Fusion
H
q
q
Vq
V
q
signature: two forward jets + HiggsH → γγ, H → τ+τ−, H → WW , H → bb
important for discovery ([Rainwater, Zeppenfeld ’97], . . . )and study (e.g. couplings [Zeppenfeld et al.], [Dührssen et al.])
Robert Harlander — Finding the Higgs – p. 20
Vector Boson Fusion
H
q
q
Vq
V
q
signature: two forward jets + HiggsH → γγ, H → τ+τ−, H → WW , H → bb
important for discovery ([Rainwater, Zeppenfeld ’97], . . . )and study (e.g. couplings [Zeppenfeld et al.], [Dührssen et al.])
QCD corrections under control (and small)[Han, Willenbrock ’91], [Figy, Oleari, Zeppenfeld ’03]
Robert Harlander — Finding the Higgs – p. 20
Higgs Strahlung
q
q H
V_
V
Robert Harlander — Finding the Higgs – p. 21
Higgs Strahlung
q
q H
V_
V
most important mode at Tevatron!
Robert Harlander — Finding the Higgs – p. 21
Higgs Strahlung
q
q H
V_
V
most important mode at Tevatron!
. . . but only marginal importance at LHC
Robert Harlander — Finding the Higgs – p. 21
Higgs Strahlung
H
V
V
_q
q
0.9
0.95
1
1.05
1.1
1.15
1.2
1.25
1.3
1.35
80 100 120 140 160 180 200MH[GeV]
KW
H(L
HC
)
LO
NLO
[Brein, Djouadi, R.H. ’03]
[Han, Willenbrock ’90]
[Ciccolini, Dittmaier, Krämer ’03]
Robert Harlander — Finding the Higgs – p. 22
Higgs Strahlung
q
q H
V_
V
0.9
0.95
1
1.05
1.1
1.15
1.2
1.25
1.3
1.35
80 100 120 140 160 180 200MH[GeV]
KW
H(L
HC
)
LO
NLO
NNLO[Brein, Djouadi, R.H. ’03]
[Han, Willenbrock ’90]
[Ciccolini, Dittmaier, Krämer ’03]
Robert Harlander — Finding the Higgs – p. 22
Higgs Strahlung
q
q H
V_
V
0.9
0.95
1
1.05
1.1
1.15
1.2
1.25
1.3
1.35
80 100 120 140 160 180 200MH[GeV]
KW
H(L
HC
)
QCD+EW
LO
NLO
NNLO[Brein, Djouadi, R.H. ’03]
[Han, Willenbrock ’90]
[Ciccolini, Dittmaier, Krämer ’03]
Robert Harlander — Finding the Higgs – p. 22
Discovery Potential
1
10
10 2
100 120 140 160 180 200
mH (GeV)
Sig
nal s
igni
fica
nce
H → γ γ ttH (H → bb) H → ZZ(*) → 4 l H → WW(*) → lνlν qqH → qq WW(*)
qqH → qq ττ
Total significance
5 σ
∫ L dt = 30 fb-1
(no K-factors)
ATLAS
Robert Harlander — Finding the Higgs – p. 23
Higgs sector in SUSY
H ↔ h0, H0, A, H+, H−
Mh0 . 130 GeV
modified couplings to SM particles (tan β!)
implications for Higgs production:
tt
t
H +~t
~
t~ H
t
t
_t
H + h
b
_b
Robert Harlander — Finding the Higgs – p. 24
Higgs sector in SUSY
H ↔ h0, H0, A, H+, H−
Mh0 . 130 GeV
modified couplings to SM particles (tan β!)
implications for Higgs production:
tt
t
H
+~t
~
t~ H
t
t
_t
H
+ h
b
_b
Robert Harlander — Finding the Higgs – p. 24
Higgs sector in SUSY
H ↔ h0, H0, A, H+, H−
Mh0 . 130 GeV
modified couplings to SM particles (tan β!)
implications for Higgs production:
tt
t
H +~t
~
t~ H
t
t
_t
H
+ h
b
_b
Robert Harlander — Finding the Higgs – p. 24
Higgs sector in SUSY
H ↔ h0, H0, A, H+, H−
Mh0 . 130 GeV
modified couplings to SM particles (tan β!)
implications for Higgs production:
tt
t
H +~t
~
t~ H
t
t
_t
H + h
b
_b
Robert Harlander — Finding the Higgs – p. 24
Example: “gluophobic Higgs”
[Djouadi ’98], [Carena et al. ’99]
tt
t
H +~t
~
t~ H
t
interfere destructively!
[R.H., Steinhauser ’04]
mt1= 200 GeV
mg = 1 TeV
tan β = 10 , α = 0 ,
θt =π
4
0
20
40
60
80
100
300 400 500 600 700 800 900
σ(pp→h+X) [pb]
m [GeV]t2~
SUSY, LO
SM, LO
LHC
Robert Harlander — Finding the Higgs – p. 25
Example: “gluophobic Higgs”
[Djouadi ’98], [Carena et al. ’99]
tt
t
H +~t
~
t~ H
t
+t
~H
t
[R.H., Steinhauser ’04]
mt1= 200 GeV
mg = 1 TeV
tan β = 10 , α = 0 ,
θt =π
4
0
20
40
60
80
100
300 400 500 600 700 800 900
σ(pp→h+X) [pb]
m [GeV]t2~
SUSY, LO
SM, LO
LHC
Robert Harlander — Finding the Higgs – p. 25
Example: “gluophobic Higgs”
[Djouadi ’98], [Carena et al. ’99]
tt
t
H +~t
~
t~ H
t
+t
~H
t
[R.H., Steinhauser ’04]
mt1= 200 GeV
mg = 1 TeV
tan β = 10 , α = 0 ,
θt =π
4
0
20
40
60
80
100
300 400 500 600 700 800 900
σ(pp→h+X) [pb]
m [GeV]t2~
SUSY, NNLO’SUSY, NLOSUSY, LO
SM, LO
LHC
Robert Harlander — Finding the Higgs – p. 25
bb → H in SUSY
modified Yukawa couplings in SUSY:λb
λt
=mb
mt
·vu
vd
=mb
mt
· tan β
t
_t
H + h
b
_b
collinear logarithms: ∼ αs ln(mb/MH) ∼ αs ln(5/200)
resummation: bottom parton densities
b_
b
H →
_
H
b
b
Robert Harlander — Finding the Higgs – p. 26
bb → H in SUSY
modified Yukawa couplings in SUSY:λb
λt
=mb
mt
·vu
vd
=mb
mt
· tan β
t
_t
H + h
b
_b
collinear logarithms: ∼ αs ln(mb/MH) ∼ αs ln(5/200)
resummation: bottom parton densities
b_
b
H →
_
H
b
b
Robert Harlander — Finding the Higgs – p. 26
bb → H in SUSY
modified Yukawa couplings in SUSY:λb
λt
=mb
mt
·vu
vd
=mb
mt
· tan β
t
_t
H + h
b
_b
collinear logarithms: ∼ αs ln(mb/MH) ∼ αs ln(5/200)
resummation: bottom parton densities
b_
b
H →
_
H
b
b
Robert Harlander — Finding the Higgs – p. 26
pp → H + bb
to yield larger cross sections. Note that closed top-quark loops have not been included in the NNLOcalculation of bb → h [10].
To all orders in perturbation theory the four- and five-flavor number schemes are identical, butthe way of ordering the perturbative expansion is different and the results do not match exactly at finiteorder. The quality of the approximations in the two calculational schemes is difficult to quantify, andthe residual uncertainty of the predictions may not be fully reflected by the scale variation displayed inFig. 8.
σ(pp_→ bb
_h + X) [fb]
√s = 1.96 TeV
µ = (2mb + Mh)/4
Mh [GeV]
bb_
→ h (NNLO)
gg → bb_
h (NLO)
1
10
100 110 120 130 140 150 160 170 180 190 200
σ(pp → bb_
h + X) [fb]
√s = 14 TeV
µ = (2mb + Mh)/4
Mh [GeV]
bb_
→ h (NNLO)
gg → bb_
h (NLO)10
10 2
10 3
100 150 200 250 300 350 400
Fig. 8: Total cross sections for pp(pp) → bbh + X at the Tevatron and the LHC as a function of the Higgs mass Mh with
no b jet identified in the final state. The error bands correspond to varying the scale from µR = µF = (2mb + Mh)/8 to
µR = µF = (2mb + Mh)/2. The NNLO curves are from Ref. [10].
6. Conclusions
We investigated bbh production at the Tevatron and the LHC, which is an important discovery channelfor Higgs bosons at large values of tan β in the MSSM, where the bottom Yukawa coupling is stronglyenhanced [13, 14]. Results for the cross sections with two tagged b jets have been presented at NLOincluding transverse-momentum and pseudorapidity cuts on the b jets which are close to the experimen-tal requirements. The NLO corrections modify the predictions by up to 50% and reduce the theoreticaluncertainties significantly. For the cases of one and no tagged b jet in the final state we compared theresults in the four- and five-flavor-number schemes. Due to the smallness of the b quark mass, largelogarithms Lb might arise from phase space integration in the four-flavor-number scheme, which areresummed in the five-flavor-number scheme by the introduction of evolved b parton densities. The five-flavor-number scheme is based on the approximation that the outgoing b quarks are at small transversemomentum. Thus the incoming b partons are given zero transverse momentum at leading order, andacquire transverse momentum at higher order. The two calculational schemes represent different pertur-bative expansions of the same physical process, and therefore should agree at sufficiently high order. Itis satisfying that the NLO (and NNLO) calculations presented here agree within their uncertainties. Thisis a major advance over several years ago, when comparisons of bb → h at NLO and gg → bbh at LOwere hardly encouraging [1, 16].
7. Acknowledgement
We thank the organizers of the 2003 Les Houches workshop for organizing such a productive and inter-esting workshop.
b_
b
H
_
H
b
b
bb → H: [R.H., Kilgore ’03]
gg → bbH: [Dawson et al. ’04], [Dittmaier et al. ’04]
Robert Harlander — Finding the Higgs – p. 27
What I could not talk about. . .
backgrounds
differential vs. inclusive cross sections
behavior of QCD corrections?
most recent development: NNLO Monte Carlo for gg → H[Anastasiou, Melnikov, Petriello ’04]
technical developments(!)
charged Higgs bosons
. . .
Robert Harlander — Finding the Higgs – p. 28
What I could not talk about. . .
backgrounds
differential vs. inclusive cross sections
behavior of QCD corrections?
most recent development: NNLO Monte Carlo for gg → H[Anastasiou, Melnikov, Petriello ’04]
technical developments(!)
charged Higgs bosons
. . .
Robert Harlander — Finding the Higgs – p. 28
What I could not talk about. . .
backgrounds
differential vs. inclusive cross sections
behavior of QCD corrections?
most recent development: NNLO Monte Carlo for gg → H[Anastasiou, Melnikov, Petriello ’04]
technical developments(!)
charged Higgs bosons
. . .
Robert Harlander — Finding the Higgs – p. 28
What I could not talk about. . .
backgrounds
differential vs. inclusive cross sections
behavior of QCD corrections?
most recent development: NNLO Monte Carlo for gg → H[Anastasiou, Melnikov, Petriello ’04]
technical developments(!)
charged Higgs bosons
. . .
Robert Harlander — Finding the Higgs – p. 28
What I could not talk about. . .
backgrounds
differential vs. inclusive cross sections
behavior of QCD corrections?
most recent development: NNLO Monte Carlo for gg → H[Anastasiou, Melnikov, Petriello ’04]
technical developments(!)
charged Higgs bosons
. . .
Robert Harlander — Finding the Higgs – p. 28
What I could not talk about. . .
backgrounds
differential vs. inclusive cross sections
behavior of QCD corrections?
most recent development: NNLO Monte Carlo for gg → H[Anastasiou, Melnikov, Petriello ’04]
technical developments(!)
charged Higgs bosons
. . .
Robert Harlander — Finding the Higgs – p. 28
Summary
main Higgs production modes at LHC:
tt
t
H H
q
q
Vq
V
qt
_t
H
q
q H
V_
V
(+ diffractive)
Robert Harlander — Finding the Higgs – p. 29
Summary
main Higgs production modes at LHC:
tt
t
H H
q
q
Vq
V
qt
_t
H
q
q H
V_
V
(+ diffractive)
combination necessary for Higgs studies
Robert Harlander — Finding the Higgs – p. 29
Summary
main Higgs production modes at LHC:
tt
t
H H
q
q
Vq
V
qt
_t
H
q
q H
V_
V
(+ diffractive)
combination necessary for Higgs studies
theory predictions under good control→ triggered many important technical developments
Robert Harlander — Finding the Higgs – p. 29
Summary
main Higgs production modes at LHC:
tt
t
H H
q
q
Vq
V
qt
_t
H
q
q H
V_
V
(+ diffractive)
combination necessary for Higgs studies
theory predictions under good control→ triggered many important technical developments
supersymmetry: much wider field,but many results remain valid
Robert Harlander — Finding the Higgs – p. 29