qcd at c - deutschlands größtes beschleunigerzentrum...

QCD AT COLLIDERS

Dieter ZeppenfeldUniversitat Karlsruhe, Germany

Sino-German Workshop on Frontiers in QCD, DESY, 20 - 23 September 2006

•• Introduction

•• Higgs physics at the LHC

•• QCD corrections to Higgsproduction

•• Hjj cross sections

•• HVV vertex measurement

•• Conclusions

QCD at Hadron Colliders

Existing: Tevatron, pp collisions at√s = 1.96 TeV L ≈ 1032 cm−2sec−1 ↔ 1fb−1/year and increasing...

starting in 2008: LHC, pp collisions at√s = 14 TeV L ≈ 1033–1034 cm−2sec−1 ↔ 10–100fb−1/year

•• Tevatron and LHC are great for studying strong interactions...

•• Main goal: explore energy frontier

- Investigate electroweak symmetry breaking, discover Higgs boson

- Search for new phenomena: SUSY, extra dimensions, Z′, little Higgs ...

- Explore jets at highest available energy on earth

- Much more ....

•• Hard collisions of quarks and gluons: QCD affects all aspects of the physics

Some examples...

Jets at the Tevatron

Largest hard cross section is dijet production

Inclusive jet ET spectrum

(GeV/c)JETTP

0 100 200 300 400 500 600 700

(GeV

/c)

nb T

dYdPσ2 d

-710

-610

-510

-410

-310

-210

-110

1

10

=0.75merge

=0.7, fcone

Midpoint R

CDF Run II Preliminary

0.1<|Y|<0.7

-1 L=1.04 fb∫

Data corrected to the hadron level

Systematic uncertainty

=1.3sep/2, RJET

T=PµNLO: EKS CTEQ 6.1M

Comparison of uncertainties

(GeV/c)JETTP

0 100 200 300 400 500 600 700D

ata

/ The

ory

0.5

1

1.5

2

2.5

3

3.5Data corrected to the parton level

=1.3sep

/2, RJet

T=PµNLO pQCD: EKS CTEQ 6.1M

=0.75merge

=0.7, fcone

Midpoint R

-1 L=1.04 fb∫ 0.1<|Y|<0.7

Data / NLO pQCDSystematic uncertaintySystematic uncertainty includinghadronization and UE

CDF Run II Preliminary

•• Excellent agreement of data with QCD predictions

•• Comparison with NLO cross sections. NNLO calculations in the works

Corrections to Drell Yan distributions

NNLO corrections to lepton distributions in qq→γ∗/Z→l+l− and W→lν: Melnikov, Petriello (2006)

integrated lepton rapidity spectrum, |η| < ηc lepton pT spectrum, pT > pT,c

Bands for factor 2 scale variation at LO, NLO, and NNLO

•• Scale uncertainties well below 1% for NNLO

•• Larger variation for pT,l > mZ/2: calculation is NLO only

•• DY cross section known well enough for luminosity monitor at LHC

SUSY searches

Look for pair production of squarks and/or gluinos via decay chain to jets and LSP (χ01), e.g.

q → qχ02 → qχ0

1Z→ qχ01QQ, qχ0

1l+l−, qχ01νν

g → qq→ qχ01q

resulting in several jets plus missing ET (+ charged leptons)

Highest squark/gluino mass reach in the 4 jet + /ET search. Define

Me f f = pT,1 + pT,2 + pT,3 + pT,4 + /ET

and require

pT,1 > 100 GeV, pT,i > 50 GeV, /ET > max(100 GeV, 0.2 Meff)

SUSY signal is enhanced cross section at large Me f f

For SUSY signal cross sections→ talk by M. Kramer

Dieter Zeppenfeld QCD at colliders 4

Backgrounds to SUSY searches

SUSY signal competes with SM backgrounds: Z + 4 jets, Z→νν; W + 4 jets, W→(l)ν etc.

Parton shower approach to multi-jet processes severely underestimatesbackgrounds

- histogram: PYTHIA simulation

- black dots: expected SUSY signal

- Z + 4 jets, Z→νν backgroundsimulated with full tree level ma-trix elements

Need full QCD ME calculations for multi-jet cross sections in SM if we want to prove newphysics signals. Available at LO via Madgraph, Alpgen, Sherpa, ...Another example: Higgs physics...

Goals of Higgs Physics

Higgs Search = search for dynamics of SU(2)×U(1) breaking

•• Discover the Higgs boson

•• Measure its couplings and probemass generation for gauge bosons and fermions

Fermion masses arise from Yukawa couplings via Φ†→(0, v+H√2

)

LYukawa = −Γ i jd Q′ iLΦd′ jR − Γ

i j∗d d′ iRΦ

†Q′ jL + . . . = −Γ i jd

v + H√2

d′ iL d′ jR + . . .

= −∑f

m f f f(

1 +Hv

)

•• Test SM prediction: f f H Higgs coupling strength = m f /v

•• Observation of H f f Yukawa coupling is no proof that v.e.v exists


Higgs coupling to gauge bosons

Kinetic energy term of Higgs doublet field:

(DµΦ)† (DµΦ) =12

∂µH∂µH +

[( gv2

)2Wµ+W−µ +

12

(g2 + g′2

)v2

4ZµZµ

](1 +

Hv

)2

•• W, Z mass generation: m2W =

( gv2)2, m2

Z =(g2+g′2)v2

4

•• WWH and ZZH couplings are generated

•• Higgs couples propotional to mass: coupling strength = 2 m2V/v within SM

Measurement of WWH and ZZH couplings is essential for identification of H as agent ofsymmetry breaking: Without a v.e.v. such a trilinear coupling is impossible at tree level


Feynman rules

H

f

f

−im fv

H

Wµ+

Wν-

ig mW gµν

H

Zµ

Zν

i g 1cosθW

mZ gµν

Verify tensor structure of HVV couplings. Loop induced couplings lead to HVµνVµν effectivecoupling and different tensor structure: gµν → q1 · q2 gµν − q1νq2µ


Higgs Production Modes at Hadron Colliders

gp t

Hp

X

X

p

V Hp

V

q

qGluon fusion Weak-Boson Fusion

V

p Hq

p

_

q p

H_p t

t

Higgs Strahlung ttH


Total SM Higgs cross sections at the LHC

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

[Kramer (’02)]

tt

t

H

q

qV

HV

W

q H

q_

, Z

q

t

_t

q_

H

Decay of the SM Higgs

Higgs decay width and branching fractions within the SM

Γ(H) [GeV]

MH [GeV]50 100 200 500 1000

10-3

10-2

10-1

1

10

10 2

102

103

10010–5

10–4

10–3

10–2

10–1

10

bb

τ τ

gg

Z

Z

0Z 0W +

+ –

µ µ

γ

γ γ

+ –

W –

ss

cc t t

0

150 200 250

Higgs Mass (GeV)

Bra

nchi

ng R

atio

300 350 400

[hep-ex/0106056]


H→γγ

H

g

g

γ

γ

W/tt

7 BR(H→γγ) ≈ 10−3

7 large backgrounds from qq→γγand gg→γγ

3 but CMS and ATLAS will have ex-cellent photon-energy resolution(order of 1%)

3 Look for a narrow γγ invariantmass peak

3 extrapolate background into thesignal region from sidebands.


H→ ZZ→ `+`−`+`−

3 invariant mass of the charged leptonsfully reconstructed

m4e (GeV/c2)100 110 120 130 140 150 160 170 180 190 200

Eve

nts

for

100

fb-1

/ 2

GeV

/c2

0

5

10

15

20

25 H → ZZ* → 4e CMS, 100 fb-1

mH = 130 GeV/c2

mH = 150 GeV/c2

mH = 170 GeV/c2

b + ZbtZZ* + t

For mH ≈ 0.6–1 TeV, use the “silver-plated” mode H→ ZZ→νν`+`−

3 BR(H→νν`+`−) = 6 BR(H→ `+`−`+`−)

3 the large missing ET allows a measurement of the transverse mass


H→WW→ `+ν`−ν

H

g

g

ν

l-

l+

ν

W-

W+

3 Exploit `+`− angular correlations

3 measure the transverse mass with a Jaco-bian peak at mH

mT =√

2 p``T /ET (1− cos (∆Φ))

7 background and signal have similarshape =⇒ must know the backgroundnormalization precisely

ATLAS TDR

0

100

200

300

0 50 100 150 200 250

mT (GeV)

Eve

nts

/ 5 G

eVmH = 170 GeVintegrated luminosity = 20 fb−1

Weak Boson Fusion

p

V Hp

V

q

q

W

W

H mH > 120 GeV

τ+

−τ

H mH < 140 GeV

γ

γ

WH

mH < 150 GeV

[Eboli, Hagiwara, Kauer, Plehn, Rainwater, D.Z. . . . ]

Most measurements can be performed at the LHC with statistical accuracies on the measuredcross sections times decay branching ratios,σ× BR, of order 10% (sometimes even better).


Statistical and systematic errors at LHC

Assumed errors in fits tocouplings:

•• QCD/PDF uncertainties

- ±5% for WBF

- ±20% for gluon fu-sion

•• luminosity/acceptanceuncertainties

- ±5%

Errors from parton distributions

Modern parton distribution functions (pdf’s) provide information on uncertainties of theirdetermination from data=⇒ can determine pdf errors of Higgs cross section predictions

AlekhinCTEQMRST

√s = 14 TeV

σ(gg → H) [pb]

MH [GeV]1000100

100

10

1

0.1

AlekhinCTEQMRST

√s = 14 TeV

σ(pp → HW ) [pb]

MH [GeV]200180160140120100

4

2

1

0.5

0.31000100

1.1

1.05

1

0.95

0.9

200150100

1.15

1.1

1.05

1

0.95

0.9


Effect on calculated/predicted cross sections

pdf errors on Higgs production cross sections are minor, of order ±5%

AlekhinCTEQMRST

√s = 14 TeV

σ(qq → Hqq) [pb]

MH [GeV]1000100

1

0.1

AlekhinCTEQMRST

√s = 14 TeV

σ(pp → Htt) [pb]

MH [GeV]200180160140120100

1

0.11000100

1.21.151.1

1.051

0.950.9

200150100

1.1

1.05

1

0.95

0.9


QCD corrections for Higgs production

Measurement of partial widths at 10–20% level or couplings at 5–10% level requirespredictions of SM production cross sections at 10% level or better=⇒ need QCD corrections to production cross sections. Much work in recent years

•• gg→H (all but NLO in mt→∞ limit)

– NLO for finite mt: Graudenz, Spira, Zerwas (1993)

– NNLO: Harlander, Kilgore (2001); Anastasiou, Melnikov (2002); Ravindran, Smith, vanNeerven (2003)

– NNLL: Catani, de Florian, Grazzini, Nason (2003)

– N3LO in soft approximation: Moch, Vogt (2005)

•• H j j by gluon fusion at NLO: Campbell, Ellis, Zanderighi (2005)

•• weak boson fusion

– total cross section at NLO: Han, Willenbrock (1991)

– distributions at NLO: Figy, Oleari, D.Z (2003); Campbell, Ellis, Berger (2004)

•• ttH production at NLO: Beenakker et al.; Dawson, Orr, Reina, Wackeroth (2002)→ Kramer

•• bbH production at NLO: Dittmaier, Kramer, Spira; Dawson et al. (2003)→ talk by Kramer

QCD corrections to gg→H

Moch & Vogt, hep-ph/0508265

0

20

40

60

80

1µr /

MH

0.2 0.5 2 3

σ(pp → H+X) [pb]

MH = 120 GeV

LO

NLO

N2LO

N3LOSV

√s = 14 TeV

µr / MH

0.2 0.5 2 3

σ(pp → H+X) [pb]

MH = 240 GeV

N2LO

N3LOSV LO

NLO

√s = 14 TeV

0

5

10

15

20

1

3 Huge improvement in re-cent years

3 Remaining scale uncer-tainty below 10%

3 Uncertainty from gluonpdf ≈ 4− 7%

7 What is K-factor forcross section with cuts?Most problematic: cen-tral jet veto against ttbackground for H→WWsearch


H j j cross section for gluon fusion

Calculation of H j j cross section at NLO in mt→∞ limit by Campbell, Ellis, Zanderighi, hep-ph/0608194

•• Modest increase of cross section at 1-loop: K-factor of order 1.2 - 1.4

•• Reduced scale dependence at NLO: remaining scale uncertainty ≈ ±20%

NLO QCD corrections to VBF

3 Small QCD corrections oforder 10%

3 Tiny scale dependence ofNLO result

- ±5% for distributions

- < 2% for σtotal

3 K-factor is phase spacedependent

3 QCD corrections underexcellent control

7 Need electroweak correc-tions for 5% uncertainty mH = 120 GeV, typical VBF cuts

NLO QCD correction for VBF now available in VBFNLO: Figy, Hankele, Jager, Klamke, Oleari, DZ, ...

parton level Monte Carlo for H j j, W j j, Z j j, W+W− j j, ZZ j j production at NLO QCD

pp→ j je+νeµ−νµX @ LHC

Stabilization of scale dependence at NLO Jager, Oleari, DZ hep-ph/0603177

How to distinguish gluon fusion and WBF?

H

(a)

vs.H

W, Z

W, Z

Double real corrections to gg→H can “fake” WBF

=⇒ we need to investigate the phenomenology of these two processes and understand thedifferences that can be exploited to distinguish between gluon fusion and WBF

=⇒ derive cuts to be applied to enhance WBF with respect to gluon fusion.Measure HWW and HZZ coupling

=⇒ derive cuts to be applied to enhance gluon fusion with respect to WBF.Measure effective Hgg coupling or Htt coupling


WBF signature

pp

J1J2

µ+

e-

ϕ

θ1θ2

J1

J2

µ+

e-

∆ϕjj

ϕ

η

Characteristics:•• energetic jets in the forward and backward directions (pT > 20 GeV)

•• large rapidity separation and large invariant mass of the two tagging jets

•• Higgs decay products between tagging jets

•• Little gluon radiation in the central-rapidity region, due to colorless W/Z exchange(central jet veto: no extra jets with pT > 20 GeV and |η| < 2.5)


Diagrams for gg fusion with finite mt effects

H

(a)

H

(b)

H

H

(c)

H

H

q Q→ q Q H q g→ q g H g g→ g g H

plus crossed processes. In total 61 independent diagrams. [DelDuca, Kilgore, Oleari, Schmidt, DZ (2001)]

Applied cuts for LHC predictions

The cross section diverges in collinear and soft regions

• INCLUSIVE cuts to define H + 2 jets

pT j > 20 GeV |η j| < 5 R j j =√(η j1 − η j2

)2+(φ j1 −φ j2

)2> 0.6

• WBF cuts to enhance WBF over gluon fusionIn addition to the previous ones, we impose

|η j1 − η j2 | > 4.2 η j1 · η j2 < 0 m j j > 600 GeV

– the two tagging jets must be well separated in rapidity

– they must reside in opposite detector hemispheres

– they must possess a large dijet invariant mass.

LHC cross sections below calculated with CTEQ6L1 pdfs and fixedαs = 0.12Expect factor ≈ 1.5 to 2 scale uncertainty due to σ ∼ α4

s


Total cross section with cuts as function of mH

Large top mass limit ok for total cross section provided mH <∼ mt


Distributions and mt→∞ limit

Transverse momentum: Large top mass limit ok provided pT, j <∼ mtDijet invariant mass: Large top mass limit ok throughout


New calculation: pseudoscalar Higgs production

pp→A j jX including top and bottom loops + interference [Michael Kubocz, diploma thesis]

A

(a)

A

(b)

A

A

(c)

A

A


New elements in the calculation

•• AQQ vertices given by −mbv γ5 tanβ and −mt

v γ51

tanβ

•• Interference of top and bottom loops

•• Can simulate CP violation in the Higgs sector: a + ibγ5 coupling to top and bottom

Inclusive cuts WBF cuts

[GeV]Am200 400 600 800 1000

[pb]

σ

1

10

210 =175 GeVt

=1, mβtan

=4.4 GeVb

=50, mβtan

=7, t+bβtan

[GeV]Am200 400 600 800 1000

[pb]

σ-210

-110

1

=175 GeVt

=1, mβtan

=4.4 GeVb

=50, mβtan

=7, t+bβtan

Distributions for A j j production

pT of soft jet Azimuthal angle between jets

20 30 40 50 60 70 80 90 100

10

210

310

410

(fb/GeV)min

(jet)T

/dpσd

=175 GeVt

=1, mβtan=4.4 GeV

b=50, mβtan

=7, t+bβtan=130 GeV, ICAm

min(jet)

Tp

0 20 40 60 80 100 120 140 160 180

2

4

6

8

10

(fb)jj

φ/dσd

jjφ

=175 GeVt

=1, mβ=130 GeV, tanAm

•• lower scale of bottom quark loops induces steeper pT falloff since pT, j > mb

•• Dips in Φ j j distribution at 0 and 180 degrees are characteristic for effective AGµνGµν

interaction

Gluon Fusion as a signal channel

Heavy quark loop induces effective Hgg vertex:

CP− even : imQv

→ Le f f =αs

12πvH Ga

µνGµν,a

CP− odd : − mQvγ5 → Le f f =

αs8πv

A Gaµν Gµν,a =

αs16πv

A GaµνGa

αβεµναβ

Azimuthal angle between tagging jets probes difference

•• Use gluon fusion induced Φ j j signal to probe structure of Hgg vertex

•• Measure size of coupling (requires NLO corrections for precision Campbell, Ellis,Zanderighi)

•• Find cuts to enhance gluon fusion over VBF and other backgrounds

=⇒ Study by Gunnar Klamke in mQ→∞ limit


Gluon fusion signal and backgrounds

Signal channel (LO):

• pp→ H j j in gluon fusion with H → W+W− → l+l−νν, (l = e, µ)

• mH = 160 GeV

dominant backgrounds:

• W+W−-production via VBF (including Higgs-channel): pp→ W+W− j j

• top-pair production: pp→ tt, tt j, tt j j (N. Kauer)

• QCD induced W+W−-production: pp→W+W− j j

applied inclusive cuts (minimal cuts):

• 2 tagging-jetspT j > 30 GeV, |η j| < 4.5

• 2 identified leptonspTl > 10 GeV, |ηl | < 2.5

• separation of jets and leptons∆η j j > 1.0, R jl > 0.7

process σ [fb]GF pp→ H + j j 115.2

VBF pp→W+W− + j j 75.2pp→ tt 6832

pp→ tt + j 9518pp→ tt + j j 1676

QCD pp→ W+W− + j j 363

Characteristic distributions

Separation of WBF H j j signal from QCD background is much easier thanseparation of gluon fusion H j j signal

tagging jet rapidity separation dijet invariant mass

jjη∆1 2 3 4 5 6 7

jjη∆/dσ

dσ1/

0

10

20

30

40

50

60

70

80

90

-310×

signalVBF

+JetsttQCD-WW

[GeV]jjm0 100 200 300 400 500 600 700 800

[1/

GeV

]jj

/dm

σ dσ

1/0

10

20

30

40

50

60

-310×

signalVBF

+JetsttQCD-WW


Selection continued

• b-tagging for reduction of top-backgrounds. (CMS Note 06/014)– (η, pT) - dependent tagging-efficiencies (60% - 75%) with 10% mistagging - probability

• selection cuts:pTl > 30 GeV, Mll < 75 GeV, Mll < 0.44 ·MWW

T , Rll < 1.1,

MWWT < 170 GeV, p�T > 30 GeV MWW

T =√

(E�T + ETll )2 − (~pTll +~p�T)2

llR∆0 0.5 1 1.5 2 2.5 3 3.5 4

llR∆

/dσ dσ

1/

0

10

20

30

40

50

-310×

[GeV]WWTm

0 50 100 150 200 250

[1/

GeV

]W

WT

/dm

σ dσ

1/

0

10

20

30

40

50

60

70

80

90

-310×

signalVBFtt+JetsQCD-WW

Results

process σ [fb] events/ 30 fb−1

GF pp→ H + j j 31.5 944VBF pp→ W+W− + j j 16.5 495

pp→ tt 23.3 699pp→ tt + j 51.1 1533pp→ tt + j j 11.2 336

QCD pp→ W+W− + j j 11.4 342Σ backgrounds 113.5 3405

⇒ S/√

B ≈ 16.2 for 30 fb−1


Tensor structure of the HVV coupling

Most general HVV vertex Tµν(q1, q2)

(a) (b)

g

Q

V

q2H

Q Q

H

Q

q q q q

V

q1q1

q2

µ

ν ν

µ

Tµν = a1 gµν +

a2(q1 · q2 gµν − qν1 qµ2

)+

a3 εµνρσ q1ρq2σ

The ai = ai(q1, q2) are scalar form factors

Physical interpretation of terms:

SM Higgs LI ∼ HVµVµ −→ a1

loop induced couplings for neutral scalar

CP even Le f f ∼ HVµνVµν −→ a2

CP odd Le f f ∼ HVµνVµν −→ a3

Must distinguish a1, a2, a3 experimentally


Azimuthal angle correlations

Tell-tale signal for non-SM coupling is azimuthal angle between tagging jets

Dip structure at 90◦ (CP even) or 0/180◦ (CP odd) only depends on tensor structure of HVVvertex. Very little dependence on form factor, LO vs. NLO, Higgs mass etc.

Azimuthal angle distribution and Higgs CP properties

Kinematics of H j j event:

Define azimuthal angle between jet momenta j+ and j− via

εµνρσ bµ+ jν+bρ− jσ− = 2pT,+ pT,− sin(φ+ −φ−) = 2 pT,+ pT,− sin∆φ j j

•• ∆φ j j is a parity odd observable

•• ∆φ j j is invariant under interchange of beam directions (b+, j+)↔ (b−, j−)

Work with Vera Hankele, Gunnar Klamke and Terrance Figy: hep-ph/0609075

Signals for CP violation in the Higgs Sector

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

-160 -120 -80 -40 0 40 80 120 160

1/ σ

dσ

/ d ∆

φ jj

∆φjj

CP-even, CP-oddCP-evenCP-odd

SM

mixed CP case:a2 = a3, a1 = 0

pure CP-even case:a2 only

pure CP odd case:a3 only

Position of minimum of ∆φ j j distribution measures relative size ofCP-even and CP-odd couplings. For

a1 = 0, a2 = d sinα, a3 = d cosα,

=⇒Minimum at −α and π −α

∆Φ j j-Distribution in gluon fusion

Fit to Φ j j-distribution with function f (∆Φ) = N(1 + A cos[2(∆Φ− ∆Φmax)]− B cos(∆Φ))

-150 -100 -50 0 50 100 1500

100

200

300

400

500

600

700

800

900

-150 -100 -50 0 50 100 1500

100

200

300

400

500

600

700

800

900

jjΦ∆-150 -100 -50 0 50 100 150

even

ts

0

100

200

300

400

500

600

700

800

900

-150 -100 -50 0 50 100 1500

0.2

0.4

0.6

0.8

1

1.2

310×

-150 -100 -50 0 50 100 1500

0.2

0.4

0.6

0.8

1

1.2

310×

jjΦ∆-150 -100 -50 0 50 100 150

even

ts0

0.2

0.4

0.6

0.8

1

1.2

310×

CP-even CP-oddA = 0.100± 0.039 A = 0.199± 0.034∆Φmax = 5.8± 15.3 ∆Φmax = 93.7± 5.1

SignalVBFtt+JetsQCD-WW

L = 300 fb−1

(∆η j j > 3.0)

fit of the background only : A = 0.069± 0.044 and ∆Φmax = 64± 25( mean values of 10 independent fits of data for L = 30 f b−1 each)

∆Φ j j-Distribution: CP violating case

-150 -100 -50 0 50 100 1500

0.2

0.4

0.6

0.8

1310×

-150 -100 -50 0 50 100 1500

0.2

0.4

0.6

0.8

1310×

jjΦ∆-150 -100 -50 0 50 100 150

even

ts

0

0.2

0.4

0.6

0.8

1310×

CP-mixture: equal CP-even and CP-odd contributionsA = 0.153± 0.037∆Φmax = 45.6± 7.3


Conclusions

•• The LHC will push the energy frontier up by another order of mag-nitude.

•• Establishing new physics signals at the LHC requires good under-standing of QCD predictions for signals and backgrounds

•• LHC will observe a SM-like Higgs boson in multiple channels, with5 . . . 20% statistical errors=⇒ great source of information on Higgs couplings

•• Higgs boson CP properties and structure of the HVV and Hggvertices can be obtained from jet-angular correlations in WBF andgluon fusion

•• An exciting new era of particle physics starts in 2008.


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