tt+X hadroproduction at NLO+SMC Zoltn Trcsnyi University of - - PowerPoint PPT Presentation

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tt+X hadroproduction at NLO+SMC Zoltn Trcsnyi University of - - PowerPoint PPT Presentation

Nov 29, 2023 347 likes •961 views

tt+X hadroproduction at NLO+SMC Zoltn Trcsnyi University of Debrecen and Institute of Nuclear Research in collaboration with A. Kardos, M.V. Garzelli and HELAC group based on arXiv:1101.2672, 1108.0387 and unpublished Thursday,

slide-1
SLIDE 1

Zoltán Trócsányi

University of Debrecen and Institute of Nuclear Research in collaboration with

  • A. Kardos, M.V. Garzelli

and HELAC group based on arXiv:1101.2672, 1108.0387 and unpublished

tt+X hadroproduction at NLO+SMC −

Thursday, September 22, 2011

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SLIDE 2
  • Motivation
  • Method
  • Predictions
  • Conclusions and Plans

Outline

Thursday, September 22, 2011

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SLIDE 3

Motivation

Thursday, September 22, 2011

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SLIDE 4
  • 1. The higher collider energy, the larger weight

in total cross section

The importance of being top

Thursday, September 22, 2011

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SLIDE 5
  • 1. The higher collider energy, the larger weight

in total cross section

  • 2. The t-quark is heavy, Yukawa coupling ∼1

⇒ plays important role in Higgs physics

The importance of being top

mt = 172.0 ± 0.9 ± 1.3 (PDG) 173.3 ± 1.1 (TeVatron)

Thursday, September 22, 2011

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SLIDE 6
  • 1. The higher collider energy, the larger weight

in total cross section

  • 2. The t-quark is heavy, Yukawa coupling ∼1
  • 3. The t-quark decays before hadronization

⇒ quantum numbers more accessible than in case of other quarks

The importance of being top

|Vtb|2 ≫ |Vts|2, |Vtd|2

  • 1. The higher collider energy, the larger weight

in total cross section

Thursday, September 22, 2011

slide-7
SLIDE 7

Top at the LHC

  • 1. Present: precision measurement of

production cross section, mass

ATLAS: arXiv:1109.3912

Thursday, September 22, 2011

slide-8
SLIDE 8

Top at the LHC

  • 1. Present: precision measurement of

production cross section, mass

CMS: arXiv:1108.3773

Thursday, September 22, 2011

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SLIDE 9
  • 2. Future: measurement of couplings

Top at the LHC

  • 1. Present: precision measurement of σtot, mt

quantum numbers, decay rates

Baur et al, hep-ph/0412021, 0512262

Thursday, September 22, 2011

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SLIDE 10
  • 2. Future: plenty of radiation in association

with t-pair

  • 3. Important backgrounds to coupling

measurements, Higgs searches: pp →ttj, ttbb, ttjj These require precise predictions for distributions at hadron level (with decays, top is not detected)

Top at the LHC

σNLO(pp → t¯ t) = 806 pb σNLO(pp → t¯ t+jet; pj

⊥ > 50 GeV) = 376 pb

  • 1. Present: precision measurement of σtot, mt

quantum numbers, decay rates

− − − −

Thursday, September 22, 2011

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SLIDE 11

Method

Thursday, September 22, 2011

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SLIDE 12
  • Idea: exact calculation in the first two orders of pQCD
  • Subtraction method (FKS in POWHEG-Box)

NLO subtractions

dΦn+1 = dΦn dΦrad , dΦrad ∝ dt dz dφ

2π

dσNLO = [B(Φn) + V(Φn) + R(Φn+1)dΦrad] dΦn = [B(Φn) + V (Φn) + (R(Φn+1)−A(Φn+1)) dΦrad] dΦn B(Φn) =

  • dσLO ,

V (Φn) = V(Φn)+

  • dΦradA(Φn+1)

Thursday, September 22, 2011

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SLIDE 13

Idea: use NLO calculation as hard process as input for the SMC Bottleneck: how to avoid double counting of first radiation w.r.to Born process (present both in R and in the PS)

From NLO to NLO+PS

Solutions:

  • MCatNLO [Frixione, Webber hep-

ph/0204244]

  • POWHEG [Nason hep-ph/

0409146, Frixione, Nason, Oleari arXiv:0709.2092] Result: PS events giving distributions exact to NLO in pQCD

Nason, Ridolfi hep-ph/0606275

Thursday, September 22, 2011

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SLIDE 14

SMC idea: use probabilistic picture of parton splitting in the collinear approximation, iterate splitting to high orders

  • Standard MC first emission:

From standard SMC to POWHEG MC

  • POWHEG MC first emission:

¯ B(Φn) = B(Φn) + V (Φn) + R(Φn+1) − A(Φn+1)

  • dΦrad

dσSMC = B(Φn)dΦn

  • ∆SMC(t0) + ∆SMC(t)αs(t)

2π 1 t P(z)

  • Θ(t − t0) dΦSMC

rad

  • = lim

k⊥→0 R(Φn+1)/B(Φn)

dσ = ¯ B(Φn)dΦn

  • ∆(Φn, pmin

⊥ ) + ∆(Φn, k⊥)R(Φn+1)

B(Φn) Θ(k⊥ − pmin

⊥ ) dΦrad

  • Thursday, September 22, 2011
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SLIDE 15
  • SMC Sudakov (probability of no emission with virtuality

above t)

From standard SMC to POWHEG MC

  • PMC Sudakov (probability of no emission with transverse

momentum above p⊥)

∆SMC(t) = exp

  • −
  • t

dΦ′

rad

αs(t′) 2π 1 t′ P(z′)

  • ∆(Φn, p⊥) = exp
  • −
  • dΦ′

rad

R(Φn, Φ′

rad)

B(Φn) Θ(k⊥(Φn, Φ′

rad) − p⊥)

  • Thursday, September 22, 2011
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SLIDE 16
  • The cross section is:

Accuracy of POWHEG MC

  • dσ =
  • ¯

BdΦn

  • ∆(Φn, pmin

⊥ )

+

  • dΦrad∆(Φn, k⊥)R(Φn+1)

B(Φn) Θ(k⊥ − pmin

⊥ )

  • ∆(Φn, p⊥) = exp
  • −
  • dΦ′

rad

R(Φn, Φ′

rad)

B(Φn) Θ(k⊥(Φn, Φ′

rad) − p⊥)

  • PMC Sudakov (probability of no emission with transverse

momentum above p⊥)

Thursday, September 22, 2011

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SLIDE 17
  • The cross section is:

Accuracy of POWHEG MC

  • dσ =
  • ¯

BdΦn

  • ∆(Φn, pmin

⊥ )

+

  • dΦrad∆(Φn, k⊥)R(Φn+1)

B(Φn) Θ(k⊥ − pmin

⊥ )

  • 1−∆(Φn,pmin

⊥

)

     

  • dσ =
  • dΦn ¯

B = σNLO

This can be shown for observables as well, see Frixione, Nason, Oleari arXiv:0709.2092

  • We obtained the NLO cross section

Thursday, September 22, 2011

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SLIDE 18

Three frameworks

  • HELAC-NLO [Bevilacqua et al 1007.4918] codes are

used to provide squared matrix elements

  • Standard Shower Monte Carlo [Sjostrand et al,

hep-ph/0603175, Corcella et al hep-ph/0210213] (SMC) is used to shower the events RESULT of PowHel (=POWHEG-BOX+HELAC-NLO): Les Houches file of Born and Born+1st radiation events (LHE) ready for processing with SMC followed by almost arbitrary experimental analysis

  • POWHEG-BOX [Alioli et al, 1002.2581] is used to

perform the related calculations to generate equal weight events for further showering (black box)

Thursday, September 22, 2011

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SLIDE 19

http://grid.kfki.hu/twiki/bin/view/DbTheory/ WebHome#Events_with_NLO_accuracy_for_par

Thursday, September 22, 2011

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SLIDE 20
  • If the ordering variable in the shower is different from the

transverse momentum of the parton splitting, such as the angular

  • rdering in HERWIG, then the hardest emission is not necessarily

the first one

  • In such cases the HERWIG discards shower evolutions (vetoed

shower) with larger transverse momentum in all splittings occurring after the first emission

  • In principle, a truncated shower simulating wide-angle soft emission

before the first emission is also needed

  • There is no implementation of truncated shower in HERWIG using

external LHE event files, the effect of the truncated showers is absent from our predictions

SMC’s with veto

  • In POWHEG-Box the first emission is the hardest one measured by

transverse momentum

Thursday, September 22, 2011

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SLIDE 21
  • Flavour structures, Born phase space
  • From Helac-OneLoop (in the process of automatization):
  • Tree-level helicity amplitudes for the Born and real

radiation processes (crossed into physical channels from all incoming kinematics)

  • One-loop corrections to the helicity amplitudes of Born

processes (unitarity based numerical evaluation of one- loop amplitudes)

  • Use polarization vectors to project tree-level helicity-

correlated matrix elements to Lorentz basis to get the spin-correlated squared matrix elements

  • From HELAC-Dipoles: two subroutines for colour-

correlated squared matrix elements of the Born processes

Input to POWHEG-BOX

Thursday, September 22, 2011

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SLIDE 22

✓ Check (implementation of) real emission squared matrix

elements in POWHEG-BOX to those from HELAC-PHEGAS in randomly chosen phase space points

✓ Check (implementation of) virtual correction in POWHEG-

BOX to those from HELAC-OneLoop in randomly chosen phase space points

✓ Check the ratio of soft and collinear limits to real emission

matrix elements tends to 1 in randomly chosen kinematically degenerate phase space points

Checks

Thursday, September 22, 2011

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SLIDE 23

✓ Compare LO and NLO cross sections to published

predictions

➡ ttZ: Lazopoulos et al, arXiv:0709.4044 ➡ ttγ: Melnikov et al, arXiv:1102.1967 ➡ ttH: Beenakker et al, hep-ph/0107081, 0211352

Reina et al, hep-ph/0107101, 0109066, 0305087

➡ ttjet: Dittmaier et al, hep-ph/0703120, 0810.0452 ➡ ttbb: Bredenstein et al, arXiv: 0905.0110, 1001.4006

Bevilacqua et al, arXiv:0907.4723

Comparison to NLO

Thursday, September 22, 2011

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SLIDE 24

Transverse momentum & rapidity distributions of the Z0-boson in pp → tt Z at the LHC

PowHel-NLO vs. NLO

−

20 40 60 80 100 120 140 160 180 200 1.0 1.1 1.2 1.3 1.4 1.5 20 40 60 80 100 120 140 160 180 200

σ [fb]

MRST2001nlo mt = 170.9GeV mZ = 91.18GeV µ = mt + mZ/2 (a) √s = 14TeV LMMP-NLO LMMP-LO POWHEL-NLO POWHEL-LO MadEvent

K-fact p⊥,Z [GeV]

50 100 150 200 250 300 350 1.0 1.25 1.0 1.5 1.75

  • 3
  • 2
  • 1

1 2 3

dσ dyZ [fb] mt = 170.9GeV mZ = 91.19GeV µ = mt + mZ/2 MRST2001 √s = 14TeV NLO LO

K-fact yZ

Thursday, September 22, 2011

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SLIDE 25

Transverse momentum and rapidity distributions of the t-quark in pp → tt γ at the LHC (with Frixione-isolation)

PowHel-NLO vs. NLO

−

10-1

2 5

1

2 5

10

2

0.95 1.0 1.05 100 200 300 400 500 600

dσ dp⊥,t [fb/GeV] √s = 14TeV mt = 172GeV µ = mt CTEQ6.6M PowHel-NLO NLO

Ratio p⊥,t [GeV]

100 200 300 400 500 600 700 800 900 1000 0.95 1.0 1.05

  • 3
  • 2
  • 1

1 2 3

dσ dyt [fb] √s = 14TeV mt = 172GeV µ = mt CTEQ6.6M PowHel-NLO NLO

Ratio yt

Thursday, September 22, 2011

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SLIDE 26

Transverse momentum & rapidity distributions of the photon in pp → tt γ at the LHC (with Frixione-isolation)

PowHel-NLO vs. NLO

−

10-1 1 10 102 0.95 1.0 1.05 50 100 150 200 250 300 350 400

dσ dp⊥,γ [fb/GeV] √s = 14TeV mt = 172GeV µ = mt CTEQ6.6M PowHel-NLO NLO

Ratio p⊥,γ [GeV]

100 200 300 400 500 600 700 800 900 1000 0.95 1.0 1.05

  • 3
  • 2
  • 1

1 2 3

dσ dyγ [fb] √s = 14TeV mt = 172GeV µ = mt CTEQ6.6M PowHel-NLO NLO

Ratio yγ

Thursday, September 22, 2011

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SLIDE 27

Transverse momentum and rapidity distributions of the Higgs boson in pp → tt H at the TeVatron

PowHel-NLO vs. NLO

− −

10-6 10-5 10-4 10-3 10-2 0.95 1.0 1.05

  • 2.0
  • 1.5
  • 1.0
  • 0.5

0.0 0.5 1.0 1.5 2.0

dσ dyH [pb] √s = 2TeV mt = 174GeV mH = 120GeV µ = mt + mH/2 MRST2002NLO PowHel-NLO NLO

Ratio yH

10-7

2 5

10-6

2 5

10-5

2 5

0.95 1.0 1.05 50 100 150 200 250 300

dσ dp⊥,H [pb/GeV] √s = 2TeV mt = 174GeV mH = 120GeV µ = mt + mH/2 MRST2002NLO PowHel-NLO NLO

Ratio p⊥,H [GeV]

Thursday, September 22, 2011

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SLIDE 28

Transverse momentum and rapidity distributions of the t-quark in pp → tt H at the TeVatron

PowHel-NLO vs. NLO

− −

10-7

2 5

10-6

2 5

10-5

2 5

0.95 1.0 1.05 50 100 150 200 250 300

dσ dp⊥,t [pb/GeV] √s = 2TeV mt = 174GeV mH = 120GeV µ = mt + mH/2 MRST2002NLO PowHel-NLO NLO

Ratio p⊥,t [GeV]

10-6 10-5 10-4 10-3 10-2 0.95 1.0 1.05

  • 2.0
  • 1.5
  • 1.0
  • 0.5

0.0 0.5 1.0 1.5 2.0

dσ dyt [pb] √s = 2TeV mt = 174GeV mH = 120GeV µ = mt + mH/2 MRST2002NLO PowHel-NLO NLO

Ratio yt

Thursday, September 22, 2011

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SLIDE 29

Transverse momentum and rapidity distributions of the t-quark in pp → tt jet at the TeVatron

PowHel-NLO vs. NLO

− −

2 5

10-3

2 5

10-2

2

0.95 1.0 1.05 0.95 1.0 1.05 50 100 150 200 250 300

dσ dp⊥,t [pb/GeV] √s = 1.96TeV mt = 174GeV µ = mt CTEQ6M R = 1 , #jets ≥ 1 PowHel-NLO NLO

Ratio p⊥,t [GeV]

0.2 0.4 0.6 0.8 1.0 1.2 1.4 0.95 1.0 1.05

  • 2.0
  • 1.5
  • 1.0
  • 0.5

0.0 0.5 1.0 1.5 2.0

dσ dyt [pb] √s = 1.96TeV mt = 174GeV µ = mt CTEQ6M R = 1 , #jets ≥ 1 PowHel-NLO NLO

Ratio yt

Thursday, September 22, 2011

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SLIDE 30

Transverse momentum & rapidity distributions of the hardest jet in pp → tt jet at the TeVatron

PowHel-NLO vs. NLO

− −

10-5 10-4 10-3 10-2 10-1 0.95 1.0 1.05 0.95 1.0 1.05 50 100 150 200 250 300

dσ dp⊥,j [pb/GeV] √s = 1.96TeV mt = 174GeV µ = mt CTEQ6M R = 1 , #jets ≥ 1 PowHel-NLO NLO

Ratio p⊥,j [GeV]

0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.95 1.0 1.05

  • 2.0
  • 1.5
  • 1.0
  • 0.5

0.0 0.5 1.0 1.5 2.0

dσ dyj [pb] √s = 1.96TeV mt = 174GeV µ = mt CTEQ6M R = 1 , #jets ≥ 1 PowHel-NLO NLO

Ratio yj

Thursday, September 22, 2011

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SLIDE 31

PowHel-NLO vs. NLO

Transverse momentum distributions of the b-quark and the bb-pair in pp → tt bb at the LHC

−

10-5 10-4 10-3 10-2 10-1 0.95 1.0 1.05 50 100 150 200 250 300 350 400

dσ dp⊥,b [pb/GeV] √s = 14TeV mt = 172.6GeV p⊥, jet > 20GeV |yjet| < 2.5 , R = 0.8 |ηtrack| < 5 , #jets ≥ 2 PowHel-NLO NLO

Ratio p⊥,b [GeV]

−

10-4

2 5

10-3

2 5

10-2

2 5

0.95 1.0 1.05 50 100 150 200 250 300 350 400

dσ dp⊥,b¯

b [pb/GeV]

√s = 14TeV mt = 172.6GeV p⊥, jet > 20GeV |yjet| < 2.5 , R = 0.8 |ηtrack| < 5 , #jets ≥ 2 PowHel-NLO NLO

Ratio p⊥,b¯

b [GeV]

−

Thursday, September 22, 2011

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SLIDE 32

PowHel-NLO vs. NLO

Invariant-mass and rapidity distributions of the bb-pair in pp → tt bb at the LHC

−

10-4

2 5

10-3

2 5

10-2

2 5

0.95 1.0 1.05 50 100 150 200 250 300 350 400

dσ dmb¯

b [pb/GeV]

√s = 14TeV mt = 172.6GeV p⊥, jet > 20GeV |yjet| < 2.5 , R = 0.8 |ηtrack| < 5 , #jets ≥ 2 PowHel-NLO NLO

Ratio mb¯

b [GeV]

0.2 0.4 0.6 0.8 1.0 1.2 0.95 1.0 1.05

  • 2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5

dσ dyb¯

b [pb]

√s = 14TeV mt = 172.6GeV p⊥, jet > 20GeV |yjet| < 2.5 , R = 0.8 |ηtrack| < 5 , #jets ≥ 2 PowHel-NLO NLO

Ratio yb¯

b

− −

Thursday, September 22, 2011

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SLIDE 33

PowHel-NLO vs. NLO

Message: PowHel-NLO is reliable

Thursday, September 22, 2011

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SLIDE 34

✓ Compare distributions based on events at Born+1st

radiation level (LHE) to those at NLO accuracy Remember: σLHE = σNLO (1+O(αs))

Comparison to NLO

Thursday, September 22, 2011

slide-35
SLIDE 35

LHE vs. NLO

Transverse momentum distributions of the t-quark and the Higgs in pp → tt H at the TeVatron

−

10-5 10-4 10-3 10-2 0.95 1.0 1.05 50 100 150 200 250 300

1 σ dσ dp⊥,t [1/GeV] √s = 2TeV mt = 174GeV mH = 120GeV µ = mt + mH/2 MRST2002NLO PowHel NLO

NLO/LHE p⊥,t [GeV]

10-5 10-4 10-3 10-2 0.95 1.0 1.05 50 100 150 200 250 300

1 σ dσ dp⊥,H [1/GeV] √s = 2TeV mt = 174GeV mH = 120GeV µ = mt + mH/2 MRST2002NLO PowHel NLO

NLO/LHE p⊥,H [GeV]

−

Thursday, September 22, 2011

slide-36
SLIDE 36

LHE vs. NLO

Rapidity distributions of the t-quark and the Higgs boson in pp → tt H at the TeVatron

−

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.95 1.0 1.05

  • 2.0
  • 1.5
  • 1.0
  • 0.5

0.0 0.5 1.0 1.5 2.0

1 σ dσ dyt [1] √s = 2TeV mt = 174GeV mH = 120GeV µ = mt + mH/2 MRST2002NLO PowHel NLO

NLO/LHE yt

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.95 1.0 1.05

  • 2.0
  • 1.5
  • 1.0
  • 0.5

0.0 0.5 1.0 1.5 2.0

1 σ dσ dyH [1] √s = 2TeV mt = 174GeV mH = 120GeV µ = mt + mH/2 MRST2002NLO PowHel NLO

NLO/LHE yH

−

Thursday, September 22, 2011

slide-37
SLIDE 37

LHE vs. NLO

Transverse momentum distributions of the t-quark and the jet in pp → tt jet at the TeVatron

−

10-5 10-4 10-3 10-2 10-1 0.95 1.0 1.05 50 100 150 200 250 300

dσ dp⊥,jet [pb/GeV] √s = 1.96TeV mt = 174GeV p⊥, jet > 20GeV R = 1 , #jets ≥ 2 PowHel NLO

NLO/LHE p⊥,jet [GeV]

10-5 10-4 10-3 10-2 0.95 1.0 1.05 50 100 150 200 250 300 350 400

dσ dp⊥,t [pb/GeV] √s = 14TeV mt = 174GeV p⊥, jet > 20GeV R = 1 , #jets ≥ 1 PowHel NLO

NLO/LHE p⊥,t [GeV]

−

Thursday, September 22, 2011

slide-38
SLIDE 38

LHE vs. NLO

Rapidity distributions of the t-quark and the jet in pp → tt jet at the TeVatron

−

0.0 0.2 0.4 0.6 0.8 1.0 1.2 0.95 1.0 1.05

  • 2.0
  • 1.5
  • 1.0
  • 0.5

0.0 0.5 1.0 1.5 2.0

dσ dyt [pb] PowHel NLO

NLO/LHE yt [1]

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.9 1.0 1.1

  • 4
  • 3
  • 2
  • 1

1 2 3 4

dσ dyjet [pb] PowHel NLO

NLO/LHE yjet [1]

−

Thursday, September 22, 2011

slide-39
SLIDE 39

LHE vs. NLO

Transverse momentum distributions of the b-quark and bb-pair in pp → tt bb at the TeVatron

− −

10-4

2 5

10-3

2 5

10-2

2 5

0.9 1.0 1.1 50 100 150 200 250 300 350 400

dσ dp⊥,b¯

b [pb/GeV]

√s = 14TeV mt = 172.6GeV p⊥, jet > 20GeV |yjet| < 2.5 , R = 0.8 |ηtrack| < 5 , #jets ≥ 2 PowHel NLO

NLE/LHE p⊥,b¯

b [GeV]

10-5 10-4 10-3 10-2 10-1 0.9 1.0 1.1 50 100 150 200 250 300 350 400

dσ dp⊥,b [pb/GeV] √s = 14TeV mt = 172.6GeV p⊥, jet > 20GeV |yjet| < 2.5 , R = 0.8 , k⊥ |ηtrack| < 5 , #jets ≥ 2 PowHel NLO

NLO/LHE p⊥,b [GeV]

− −

Thursday, September 22, 2011

slide-40
SLIDE 40

LHE vs. NLO

Invariant-mass and rapidity distributions of the bb-pair in pp → tt bb at the TeVatron

− −

0.2 0.4 0.6 0.8 1.0 1.2 0.9 1.0 1.1

  • 2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5

dσ dyb¯

b [pb]

√s = 14TeV mt = 172.6GeV p⊥, jet > 20GeV |yjet| < 2.5 , R = 0.8 |ηtrack| < 5 , #jets ≥ 2 PowHel NLO

NLE/LHE yb¯

b

10-4

2 5

10-3

2 5

10-2

2 5

0.9 1.0 1.1 50 100 150 200 250 300 350 400

dσ dmb¯

b [pb/GeV]

√s = 14TeV mt = 172.6GeV p⊥, jet > 20GeV |yjet| < 2.5 , R = 0.8 |ηtrack| < 5 , #jets ≥ 2 PowHel NLO

NLE/LHE mb¯

b [GeV]

− −

Thursday, September 22, 2011

slide-41
SLIDE 41

PowHel-LHE vs. NLO

Message: PowHel-LHE’s are reliable (but tell me your doubts)

Thursday, September 22, 2011

slide-42
SLIDE 42

PowHel+Decay: we just include on-shell decays of t-quarks and the heavy bosons, decay of tau’s emerging from heavy boson-decay as implemented in PYTHIA, turning off any shower and hadronization effects PowHel+SMC: decays, showering and hadronization have been included, using both PYTHIA and HERWIG Number and type of particles are very different => the possible selection cuts are restricted in comparisons

Three levels of predictions

PowHel: we use the events at BORN+1st radiation

Thursday, September 22, 2011

slide-43
SLIDE 43

Jet cuts: to compare decay and full SMC predictions with physical cuts to the extent it is meaningful (leptons are very different at the two levels) Physical cuts: to compare physical predictions from PYTHIA and HERWIG Cuts are shown in figures

Three levels of cuts

No cuts: to compare all three predictions (no leptons, and

  • nly one extra jet, beyond Born in POWHEG predictions)

Thursday, September 22, 2011

slide-44
SLIDE 44

LHE vs. decay vs. full SMC, no cuts

Transverse momentum and rapidity distributions of the hardest jet in pp → tt H at the LHC (n.b.: top-jet is included in LHE but not after decay)

10-6 10-5 10-4 10-3 10-2 0.0 0.5 1.0 1.5 100 200 300 400 500 600

dσ dp⊥,j1 [pb/GeV] mH = 120GeV µ = mt + mH/2 CTEQ6.6M anti-k⊥, R = 0.5 √s = 7TeV mt = 172GeV PowHel+Decay PowHel+PYTHIA PowHel

Decay/SMC p⊥,j1 [GeV]

10-5 10-4 10-3 10-2 10-1 1 0.95 1.0 1.05

  • 4
  • 3
  • 2
  • 1

1 2 3 4

dσ dyj1 [pb] √s = 7TeV mt = 172GeV mH = 120GeV µ = mt + mH/2 CTEQ6.6M anti-k⊥, R = 0.5 PowHel PowHel+Decay PowHel+PYTHIA

Decay/SMC yj1

−

Thursday, September 22, 2011

slide-45
SLIDE 45

Decay vs. full SMC, jet cuts

Lepton and missing pT distributions in pp → tt H at the LHC

−

10-8 10-7 10-6 10-5 10-4 10-3 10-2 0.0 0.5 1.0 1.5 50 100 150 200 250 300 350 400 450

dσ dp⊥,ℓ+ [pb/GeV] mt = 172GeV mH = 120GeV µ = mt + mH/2 CTEQ6.6M p⊥,j ≥ 20GeV |yj| ≤ 2.5 anti-k⊥, R = 0.5 √s = 7TeV PowHel+Decay PowHel+PYTHIA PowHel+HERWIG

Ratio p⊥,ℓ+ [GeV]

10-7 10-6 10-5 10-4 10-3 0.0 0.5 1.0 1.5 100 200 300 400 500 600

dσ d/ p⊥ [pb/GeV] mt = 172GeV mH = 120GeV µ = mt + mH/2 CTEQ6.6M p⊥,j ≥ 20GeV |yj| ≤ 2.5 anti-k⊥, R = 0.5 √s = 7TeV PowHel+Decay PowHel+PYTHIA PowHel+HERWIG

Ratio / p⊥ [GeV]

Thursday, September 22, 2011

slide-46
SLIDE 46

Decay vs. full SMC, jet cuts

HT distributions in pp → tt jet at the TeVatron and pp → tt H at the LHC (scalar sum of all transverse momenta)

− −

10-7 10-6 10-5 10-4 10-3 0.0 0.5 1.0 1.5 200 250 300 350 400 450 500 550 600 650 700

dσ dH⊥ [pb/GeV] p⊥, jet, p⊥, ℓ+ > 20GeV / E⊥ > 20GeV H⊥ > 220GeV #jets ≥ 5 , |yj| ≤ 2 √s = 1.96TeV mt = 172GeV anti-k⊥ , R = 0.5 PowHel+Decay PowHel+PYTHIA PowHel+HERWIG

Ratio H⊥ [GeV]

10-7 10-6 10-5 10-4 0.0 0.5 1.0 1.5 200 300 400 500 600 700 800 900 100011001200

dσ dH⊥ [pb/GeV] √s = 7TeV mt = 172GeV mH = 120GeV µ = mt + mH/2 CTEQ6.6M anti-k⊥, R = 0.5 |yj| ≤ 2.5 p⊥,j ≥ 20GeV PowHel+Decay PowHel+PYTHIA PowHel+HERWIG

Ratio H⊥ [GeV]

−

Thursday, September 22, 2011

slide-47
SLIDE 47

LHE vs. decay vs. full SMC

Message: decay, shower and hadronization can have significant effect, depending strongly on the process, observable, shower setup and selection

Thursday, September 22, 2011

slide-48
SLIDE 48

Predictions

Thursday, September 22, 2011

slide-49
SLIDE 49

Decay vs. full SMC, physical cuts

Lepton transverse momentum and rapidity distributions in pp → tt jet at the TeVatron (NLO+Decay: Melnikov and Schulze, arXiv:1004.3284)

− −

5

10-3

2 5

10-2

2 5

10-1

2

0.75 1.0 1.25

  • 2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5

dσ dyℓ+ [pb] √s = 1.96TeV mt = 172GeV p⊥, jet, p⊥, ℓ+ > 20GeV / E⊥ > 20GeV H⊥ > 220GeV #jets ≥ 5 , |yj| ≤ 2 NLO+Decay PowHel+Decay PowHel+PYTHIA PowHel+HERWIG

Ratio yℓ+

10-10 10-8 10-6 10-4 10-2 0.5 1.0 1.5 50 100 150 200 250

dσ dp⊥,ℓ+ [pb/GeV] p⊥, jet, p⊥, ℓ+ > 20GeV / E⊥ > 20GeV H⊥ > 220GeV #jets ≥ 5 , |yj| ≤ 2 anti-k⊥ , R = 0.5 √s = 1.96TeV mt = 172GeV NLO+Decay PowHel+Decay PowHel+PYTHIA PowHel+HERWIG

Ratio p⊥,ℓ+ [GeV]

Thursday, September 22, 2011

slide-50
SLIDE 50

Decay vs. full SMC, physical cuts

Distributions of HT and rapidity of the fifth jet in pp → tt jet at the TeVatron (NLO+Decay: Melnikov and Schulze, arXiv:1004.3284)

− −

10-7 10-6 10-5 10-4 10-3 0.0 0.5 1.0 1.5 200 250 300 350 400 450 500 550 600 650 700

dσ dH⊥ [pb/GeV] p⊥, jet, p⊥, ℓ+ > 20GeV / E⊥ > 20GeV H⊥ > 220GeV #jets ≥ 5 , |yj| ≤ 2 √s = 1.96TeV mt = 172GeV anti-k⊥ , R = 0.5 PowHel+Decay PowHel+PYTHIA PowHel+HERWIG

Ratio H⊥ [GeV]

2 5

10-2

2 5

10-1 0.75 1.0 1.25

  • 2.0
  • 1.5
  • 1.0
  • 0.5

0.0 0.5 1.0 1.5 2.0

dσ dyj5 [pb] p⊥, jet, p⊥, ℓ+ > 20GeV / E⊥ > 20GeV H⊥ > 220GeV #jets ≥ 5 , |yj| ≤ 2 mt = 172GeV √s = 1.96TeV NLO+Decay PowHel+Decay PowHel+PYTHIA PowHel+HERWIG

Ratio yj5

Thursday, September 22, 2011

slide-51
SLIDE 51

Full SMC, physical cuts

Distributions of lepton transverse momentum & rapidity in pp → tt jet at the LHC

−

10-4 10-3 10-2 10-1 0.0 0.8 1.0 1.2 50 100 150 200 250

dσ dp⊥,ℓ+ [pb/GeV] √s = 7 TeV mt = 172 GeV R = 0.5 , anti − k⊥ #jets ≥ 3 p⊥, jet > 30 GeV , p⊥, ℓ± > 20 GeV / E⊥|ℓ+=ℓ− > 30 GeV , / E⊥|ℓ+=ℓ− > 20 GeV PowHel+Decay PowHel+PYTHIA PowHel+HERWIG µ = m⊥

Ratio p⊥,ℓ+ [GeV]

µ = mt

10-1

2 5

1

2 5

10 0.8 1.0 1.2

  • 2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5

dσ dyℓ+ [pb] √s = 7 TeV mt = 172 GeV R = 0.5 , anti − k⊥ , #jets ≥ 3 p⊥, jet > 30 GeV , p⊥, ℓ± > 20 GeV / E⊥|ℓ+=ℓ− > 30 GeV , / E⊥|ℓ+=ℓ− > 20 GeV PowHel+Decay PowHel+PYTHIA PowHel+HERWIG µ = m⊥

Ratio yℓ+

µ = mt

Thursday, September 22, 2011

slide-52
SLIDE 52

Full SMC, physical cuts

Distributions of l+l- invariant mass and missing transeverse momentum in pp → tt jet at the LHC

−

10-5 10-4 10-3 10-2 10-1 0.0 0.5 1.0 1.5 100 200 300 400 500 600

dσ dmℓ+ℓ− [pb/GeV] √s = 7 TeV mt = 172 GeV R = 0.5 , anti − k⊥ #jets ≥ 3 p⊥, jet > 30 GeV , p⊥, ℓ± > 20 GeV / E⊥|ℓ+=ℓ− > 30 GeV , / E⊥|ℓ+=ℓ− > 20 GeV PowHel+Decay PowHel+PYTHIA PowHel+HERWIG µ = m⊥

Ratio mℓ+ℓ− [GeV]

µ = mt 5

10-3

2 5

10-2

2 5

10-1 0.0 0.5 1.0 1.5 50 100 150 200 250 300

dσ d/ p⊥ [pb/GeV] √s = 7 TeV mt = 172 GeV R = 0.5 , anti − k⊥ #jets ≥ 3 p⊥, jet > 30 GeV , p⊥, ℓ± > 20 GeV / E⊥|ℓ+=ℓ− > 30 GeV , / E⊥|ℓ+=ℓ− > 20 GeV PowHel+Decay PowHel+PYTHIA PowHel+HERWIG µ = m⊥

Ratio / p⊥ [GeV]

µ = mt

Thursday, September 22, 2011

slide-53
SLIDE 53

Decay vs. full SMC, physical cuts

B-meson pair invariant mass and ΔR distributions in pp → tt H at the LHC (aMCatNLO: Hirschi et al, arXiv: 1104.5613)

−

10-5

2 5

10-4

2 5

10-3

2 5

10-2 0.75 1.0 1.25 20 40 60 80 100 120 140 160 180 200

dσ dmBB∆mBB [pb] µ = (m⊥,t · m⊥,¯

t · m⊥,H)1/3

√s = 7TeV mt = 172.5GeV MSTW2008nlo all channels (PowHel+PYTHIA) all channels (PowHel+HERWIG) H→ bb channel (PowHel+HERWIG) H→ bb channel (aMCatNLO+HERWIG)

Ratio mBB [GeV]

2 5

10-3

2 5

10-2

2

0.75 1.0 1.25 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

dσ d∆R(BB)∆R(BB) [pb] √s = 7TeV mt = 172.5GeV MSTW2008nlo µ = (m⊥,t · m⊥,¯

t · m⊥,H)1/3

all channels (PowHel+PYTHIA) all channels (PowHel+HERWIG) H→ bb channel (PowHel+HERWIG) H→ bb channel (aMCatNLO+HERWIG)

Ratio ∆R(BB)

Thursday, September 22, 2011

slide-54
SLIDE 54

Decay vs. full SMC, jet and physical cuts

jet-jet invariant mass distribution in pp → tt H at the LHC left: only jet cuts right: physical cuts

−

10-6 10-5 10-4 10-3 10-2 0.0 0.5 1.0 1.5 50 100 150 200 250 300

dσ dmjj [pb/GeV] µ = mt + mH/2 CTEQ6.6M anti-k⊥, R = 0.5 |yj|, |yℓ±| ≤ 2.5 / Et ≥ 30GeV p⊥,j, p⊥,ℓ± ≥ 20GeV √s = 7TeV mt = 172GeV mH = 120GeV PowHel+Decay PowHel+PYTHIA PowHel+HERWIG

Ratio mjj [GeV]

10-4

2 5

10-3

2 5

10-2

2 5

0.0 0.5 1.0 1.5 50 100 150 200 250 300

dσ dmjj [pb/GeV] mt = 172GeV mH = 120GeV µ = mt + mH/2 CTEQ6.6M p⊥,j ≥ 20GeV |yj| ≤ 2.5 anti-k⊥, R = 0.5 √s = 7TeV PowHel+Decay PowHel+PYTHIA PowHel+HERWIG

Ratio mjj [GeV]

Thursday, September 22, 2011

slide-55
SLIDE 55

Conclusions and outlook

Thursday, September 22, 2011

slide-56
SLIDE 56

✓ SME’s obtained easily from HELAC-NLO ✓ NLO cross sections are reliable ✓ PowHel LHE are reliable ➡ Effects of decays and showers are often important,

depending on process, observable, shower setup and selection

✓ LHE event files for pp →tt, ttH, ttjet processes

available

➡ Easy predictions for LHC with NLO+PS accuracy

Conclusions

✓ First applications of POWHEG-Box to pp→ttX

processes

− − − −

Thursday, September 22, 2011

slide-57
SLIDE 57

➡ Study scale choices and dependences ➡ Generation of events on request ➡ Comparison to data (in progress) ➡ Make codes public ➡ Extension to further processes... Plans

Thursday, September 22, 2011

slide-58
SLIDE 58

The end

Thursday, September 22, 2011

slide-59
SLIDE 59
  • 2. Future: measurement of couplings

Top at the LHC

  • 1. Present: precision measurement of σtot, mt

quantum numbers, decay rates

Baur et al, hep-ph/0412021, 0512262

Thursday, September 22, 2011

slide-60
SLIDE 60

Full SMC, physical cuts

Distributions of l+l- invariant mass in pp → tt jet at the LHC left: exactly one right: at least one lepton and one antilepton

−

10-5 10-4 10-3 10-2 10-1 0.0 0.5 1.0 1.5 100 200 300 400 500 600

dσ dmℓ+ℓ− [pb/GeV] √s = 7 TeV mt = 172 GeV R = 0.5 , anti − k⊥ #jets ≥ 3 p⊥, jet > 30 GeV , p⊥, ℓ± > 20 GeV / E⊥|ℓ+=ℓ− > 30 GeV , / E⊥|ℓ+=ℓ− > 20 GeV PowHel+Decay PowHel+PYTHIA PowHel+HERWIG µ = m⊥

Ratio mℓ+ℓ− [GeV]

µ = mt

10-5 10-4 10-3 10-2 10-1 0.0 0.5 1.0 1.5 100 200 300 400 500 600

dσ dmℓ+ℓ− [pb/GeV] √s = 7 TeV mt = 172 GeV R = 0.5 , anti − k⊥ #jets ≥ 3 p⊥, jet > 30 GeV , p⊥, ℓ± > 20 GeV / E⊥|ℓ+=ℓ− > 30 GeV , / E⊥|ℓ+=ℓ− > 20 GeV PowHel+Decay PowHel+PYTHIA at least one ℓ+ and ℓ− µ = m⊥

Ratio mℓ+ℓ− [GeV]

Thursday, September 22, 2011