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HO10, CERN, 01.07.10 - PPT Presentation

A Kulesza Squark and gluino production at hadron colliders Soft Gluon Resummation For Squark and Gluino Hadroproduction AK and L Motyka Phys Rev Lett 102 111802 2009 ID: 248997

gluino production hadron squark production gluino squark hadron colliders kulesza cern ho10 nlo susy beenakker mer

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Slide1

HO10, CERN, 01.07.10

A. Kulesza, Squark and gluino production at hadron colliders

Soft Gluon

Resummation For Squark and Gluino Hadroproduction

AK and L. Motyka, Phys. Rev. Lett. 102, 111802 (2009)AK and L. Motyka, Phys. Rev. D 80 (2009) 095004W. Beenakker, S. Brensing, M. Krämer, AK, E. Laenen and I. Niessen, JHEP 12 (2009) 041W. Beenakker, S. Brensing, M. Krämer, AK, E. Laenen and I. Niessen, arXiv:1006.4771 [hep-ph]

Anna Kulesza

HO10 Theory

Institute, CERN, 01.07.2010Slide2

Outline

HO10, CERN, 01.07.10A. Kulesza, Squark and gluino production at hadron colliders

erturbative higher order

effects at work at the LHCMotivation: why high precision for squark and gluino productionStatus of the predictions for squark and gluino production processesSoft gluon effects beyond NLO → resummation

Numerical predictions for the LHC (and Tevatron)Slide3

HO10, CERN, 01.07.10

A. Kulesza, Squark and gluino production at hadron colliders

I. HIGHER ORDERS

= why higher orders for SUSY signals?Slide4

HO are Already Needed

HO10, CERN, 01.07.10A. Kulesza, Squark and gluino production at hadron colliders

(… for some processes and some quantities)Slide5

HO are Already Needed

HO10, CERN, 01.07.10A. Kulesza, Squark and gluino production at hadron colliders

(… for some processes and some quantities)

MSSM:

minimal content of SUSY particles + R-parity Hadron colliders: coloured sparticles most copiously producedSlide6

HO are Already Needed

HO10, CERN, 01.07.10A. Kulesza, Squark and gluino production at hadron colliders

(… for some processes and some quantities)

MSSM:

minimal content of SUSY particles + R-parity Hadron colliders: coloured sparticles most copiously producedHigh rates for pair-production of squarks and gluinosSlide7

HO are Already Needed

HO10, CERN, 01.07.10

A. Kulesza, Squark and gluino production at hadron colliders

(… for some processes and some quantities)

MSSM:minimal content of SUSY particles + R-parity Hadron colliders: coloured sparticles most copiously producedHigh rates for pair-production of squarks and gluinosSquark and gluino production for SPS1a'xKey discovery processes in SUSY searches

xSlide8

Tevatron

searches

Inclusive information on

total production cross sectionscrucial for determination of mass limits in case of no discovery

A. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10squarksgluinosSlide9

HO will be needed

A. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10

No show at the LHC → determination of mass limits from inclusive measurements, see Tevatron

need predictions for total rates Slide10

Discovery

Exclusive information characteristic to decay products

mass spectrum determination through measurements of kinematic properties, e.g. endpoints of distributions

HO will be needed

A. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10 No show at the LHC → determination of mass limits from inclusive measurements, see Tevatron need predictions for total rates Slide11

SUSY parameter determination

For three-body decays mass reconstruction via kinematic endpoints difficultSome BSM scenarios, e.g. models of extra dimensions, can predict similar to SUSY cascade decay signatures at the LHC

A. Kulesza, Squark and gluino production at hadron colliders

HO10, CERN, 01.07.10

Need additional information on event ratesSlide12

SUSY parameter determination

For three-body decays mass reconstruction via kinematic endpoints difficultSome BSM scenarios, e.g. models of extra dimensions, can predict similar to SUSY cascade decay signatures at the LHC

Adding information on cross sections to information on kinematical edges significantly improves accuracy of

SUSY parameter determination from global fits

A. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10Need additional information on event ratesΔχ2[Dreiner, Krämer, Lindert, O’Leary’10]SPS1a7 TeV, 1fb-1Slide13

SUSY parameter determination

For three-body decays mass reconstruction via kinematic endpoints difficultSome BSM scenarios, e.g. models of extra dimensions, can predict similar to SUSY cascade decay signatures at the LHC

Adding information on cross sections to information on kinematical edges significantly improves accuracy of of SUSY parameter determination from global fits

A. Kulesza, Squark and gluino production at hadron colliders

HO10, CERN, 01.07.10Need additional information on event ratesΔχ2[Dreiner, Krämer, Lindert, O’Leary’10] NLO vs LO: substantial reduction of errors on (some) parameter values!SPS1a7 TeV, 1fb-1Slide14

HO10, CERN, 01.07.10

A. Kulesza, Squark and gluino production at hadron colliders

II. PERTURBATIVE HIGHER ORDER EFFECTSSlide15

Partonic subprocesses

Leading Order = O

(αs2)

A. Kulesza, Squark and gluino production at hadron colliders

HO10, CERN, 01.07.10[Kane, Leveille'82][Harrison, Llewellyn Smith'84][Dawson, Eichten, Quigg'85]Slide16

NLO SUSY-QCD

corrections →

(αs3 ) [Beenakker, Höpker, Spira, Zerwas'96] [Beenakker, Krämer, Plehn, Spira, Zerwas’97For squark-antisquark production: dominant NNLO contributions (NNLL-NNLO, Coulomb, scale dependence) → O(αs4 ) [Langenfeld, Moch'09]EW corrections → O(αs2 α2) [

Hollik, Kollar, Trenkel'07][Hollik, Mirabella'08] [Hollik, Mirabella, Trenkel'08] [Beccaria et al.'08] [Mirabella'09] [Germer, Hollik, Mirabella, Trenkel’10]Theoretical StatusHO10, CERN, 01.07.10A. Kulesza, Squark and

gluino production at hadron collidersFixed-order corrections to O(αs2) processesSlide17

NLO SUSY-QCD

corrections →

Hollik, Kollar, Trenkel'07][Hollik, Mirabella'08] [Hollik, Mirabella, Trenkel'08] [Beccaria et al.'08] [Mirabella'09] [Germer, Hollik, Mirabella, Trenkel’10]Theoretical StatusHO10, CERN, 01.07.10

A. Kulesza, Squark and gluino production at hadron collidersQCD-EW interference and photon-induced contributions, tree-level EW [Bornhauser

et al.'07][Alan,

Cankocak

, Demir'07] [

Hollik

Kollar

, Trenkel'07][Hollik, Mirabella'08] [

Hollik

, Mirabella, Trenkel'08] [

Bozzi

Fuks

, Klasen'05] [

Germer

Hollik

, Mirabella, Trenkel

’10]

Tree-level EW effects

)

and

)

Fixed-order corrections to

(

)

processesSlide18

NLO SUSY-QCD

corrections →

Hollik, Kollar, Trenkel'07][Hollik, Mirabella'08] [Hollik, Mirabella, Trenkel'08] [Beccaria et al.'08] [Mirabella'09] [Germer, Hollik, Mirabella, Trenkel’10]Theoretical StatusHO10, CERN, 01.07.10

A. Kulesza, Squark and gluino production at hadron collidersQCD-EW interference and photon-induced contributions, tree-level EW [Bornhauser

et al.'07][Alan,

Cankocak

, Demir'07] [

Hollik

Kollar

, Trenkel'07][Hollik, Mirabella'08] [

Hollik

, Mirabella, Trenkel'08] [

Bozzi

Fuks

, Klasen'05] [

Germer

Hollik

, Mirabella, Trenkel

’10]

Tree-level EW effects

)

and

)

Bound-state effects in

gluino

-pair production

[Hagiwara, Yokoya'09]

gluinonia

production and decay

[

Kauth

Kühn

Marquard

, Steinhauser'09]

Fixed-order corrections to

(

)

processesSlide19

LO vs NLO

NLO SUSY QCD

A. Kulesza, Squark and gluino production at hadron colliders

HO10, CERN, 01.07.10

[Beenakker, Höpker, Spira, Zerwas’97]Slide20

LO vs NLO

LO results for total cross sections suffer from enormous scale dependence

NLO SUSY QCD

A. Kulesza, Squark and gluino production at hadron colliders

HO10, CERN, 01.07.10[Beenakker, Höpker, Spira, Zerwas’97]Slide21

LO vs NLO

LO results for total cross sections suffer from enormous scale dependence

NLO SUSY QCD

A. Kulesza, Squark and gluino production at hadron colliders

HO10, CERN, 01.07.10[Beenakker, Hopker, Spira, Zerwas’97]100% correction!Slide22

At Threshold

Large masses of SUSY particles ⇒

production close to thresholdGeneral structure of the NLO

correction in the threshold limit

A. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10Soft/collinear gluon emission Coulomb gluonsSlide23

At Threshold

Large masses of SUSY particles ⇒

production close to thresholdGeneral structure of the NLO

correction in the threshold limit

A. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10Soft/collinear gluon emission Coulomb gluonsBoth types of corrections can be resummed to all ordersHere: NLL resummation of soft gluon correctionsSlide24

At Threshold

Large masses of SUSY particles ⇒

production close to thresholdGeneral structure of the NLO

correction in the threshold limit

corrections for [Hagiwara, Yokoya’09][Kulesza, Motyka’09]Resummation of soft and Coulomb corrections together [Beneke, Schwinn, Falgari’09], applied toSlide25

Soft gluon

resummation

HO10, CERN, 01.07.10

A. Kulesza, Squark and gluino production at hadron colliders

Systematic reorganization of perturbative series, for threshold logs performed in the space of Mellin momentssums up LL: αsn log n+1 (N) NLL: αsn log n (N) [Sterman’87][Catani, Trentadue’89]withSlide26

Threshold Resummation For Squark And Gluino Production

HO10, CERN, 01.07.10

A. Kulesza, Squark and gluino production at hadron colliders

2 process with nontrivial colour structure and massesmatrices in colour spacefrom solving the renormalization group equationSlide27

Soft anomalous dimensions

Need 1-loop anomalous dimension matrices in order to resum up to NLL

massless 2→n QCD

processes [Kidonakis, Oderda

, Sterman'98] [Bonciani et al.'03][Mert Aybat, Dixon, Sterman'06]massive case: heavy quark pair-production [Kidonakis, Sterman'96][Bonciani et al.'98]Calculation of 1-loop soft anomalous dimension matrices Γij for 2→2 processes with nontrivial colour structure and massive particles in the final stateHO10, CERN, 01.07.10A. Kulesza, Squark and gluino production at hadron colliderssame colour structure as in top-antitop production ✓Slide28

Resummation for Processes with colour and masses

Threshold limit:

ΓIJ

matrices calculated in the s-channel colour basis become diagonal [

Beneke, Falgari, Schwinn'09]HO10, CERN, 01.07.10A. Kulesza, Squark and gluino production at hadron collidersSlide29

Resummation

for Processes with

colour and masses

Threshold limit: ΓIJ matrices calculated in the

s-channel colour basis become diagonal [Beneke, Falgari, Schwinn'09]In orthogonal basis in colour space for which ΓIJ is diagonal the resummed partonic cross section reads up to NLL [Kidonakis, Sterman'96-97][Bonciani, Catani, Mangano, Nason'98]Full set of D(1) coefficients for squark and gluino production processesD(1) correspond to values of the quadratic Casimir operators for the SU(3) representations for the outgoing state  soft gluon radiation only “feels” the total colour charge of the heavy-particle pair produced at thresholdHO10, CERN, 01.07.10A. Kulesza, Squark and gluino production at hadron collidersSlide30

Resummation

-improved NLL+NLO total cross section

NLL

resummed expression has to be matched with the full NLO resultInverse

Mellin transform evaluated using a contour in the complex N space according to 'Minimal Prescription’ [Catani, Mangano, Nason Trentadue'96]NLO cross sections evaluated with publicly available code PROSPINO [Beenakker, Hoepker, Krämer, Plehn, Spira, Zerwas] [http://www.thphys.uni-heildelberg.de/plehn/prospino/]HO10, CERN, 01.07.10A. Kulesza, Squark and gluino production at hadron collidersSlide31

HO10, CERN, 01.07.10

A. Kulesza, Squark and gluino production at hadron colliders

II. PERTURBATIVE HIGHER ORDER EFFECTS AT WORKSlide32

Gluino-Pair Production @ LHC

HO10, CERN, 01.07.10A. Kulesza, Squark and gluino production at hadron colliders

[AK,Motyka’08] [AK,Motyka’09]

=mgluino/msquarkSignificant correction wrt. NLO due to resummation for gluino-pair productionCTEQ6MSlide33

Gluino-Pair Production @ LHC

HO10, CERN, 01.07.10A. Kulesza, Squark and gluino production at hadron colliders

[AK,Motyka’08] [AK,Motyka’09]

=mgluino/msquarkSignificant correction wrt. NLO due to resummation for gluino-pair productionReduction of theory error due to scale variation down to ~5% for gluino masses > 1 TeVCTEQ6MSlide34

NLL at LHC

Calculations extended to all four processes of squark and gluino production

gluino

=msquarkA. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10[Beenakker, Brensing, Krämer, A.K., Laenen, Niessen’09]Slide35

NLL at LHC

Calculations extended to all four processes of squark and gluino production

gluino

=msquarkA. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10[Beenakker, Brensing, Krämer, A.K., Laenen, Niessen’09]Slide36

NLL at LHC

Calculations extended to all four processes of squark and gluino production

gluino

=msquarkmgluino=msquarkMost precise predictions for squark and gluino production rates currently availableA. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10[Beenakker, Brensing, Krämer, A.K., Laenen, Niessen’09]Slide37

NLL at Tevatron

NLL resummed results also available for all four processes of squark

and gluino production at the Tevatron

mgluino=msquarkmgluino=msquarkMost precise predictions for squark and gluino production rates currently availableA. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10[Beenakker, Brensing, Krämer, A.K., Laenen, Niessen’09]Slide38

Tevatron mass limits revisited

Reduced theory error due to scale variationShift of the central value and the error band

HO10, CERN, 01.07.10

A. Kulesza, Squark and gluino production at hadron colliders

[Beenakker, Brensing, Krämer, A.K., Laenen, Niessen, in preparation]Slide39

Stops

Scalar SUSY-partners of left- and right-handed fermions mix: weak interaction eigenstates mix into mass

eigenstates The off-diagonal terms in the mixing matrix are proportional to

fermion mass, mfStop likely to be the lightest squark

Strongest mixing in the 3rd generation, in particular in the stop sectoraaaA. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10aaSlide40

Stops

Scalar SUSY-partners of left- and right-handed fermions mix: weak interaction

eigenstates

mix into mass eigenstates The off-diagonal terms in the mixing matrix are proportional to fermion mass,

Stops

Scalar SUSY-partners of left- and right-handed fermions mix: weak interaction eigenstates mix into mass

eigenstates The off-diagonal terms in the mixing matrix are proportional to

fermion mass, mfStop likely to be the lightest squark

At leading orderStrongest mixing in the 3rd generation, in particular in the stop sectoraaaA. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10aaSquark-antisquarkSlide42

Stops

Scalar SUSY-partners of left- and right-handed fermions mix: weak interaction

eigenstates

mix into mass eigenstates The off-diagonal terms in the mixing matrix are proportional to fermion mass,

mfStop likely to be the lightest squark At leading orderStrongest mixing in the 3rd generation, in particular in the stop sectorStop-antistopaaaA. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10aaOnly diagonal i.e. pairs producedLO cross section depends only on the stop massNote: for sbottom-pair production LO contribution negligible Slide43

Stop Resummation

HO10, CERN, 01.07.10

A. Kulesza, Squark and gluino production at hadron colliders

Tevatron

LHC @ 7 TeV[Beenakker, Brensing, Krämer, A.K., Laenen, Niessen’10]Slide44

Stop Resummation

HO10, CERN, 01.07.10

A. Kulesza, Squark and gluino production at hadron colliders

Tevatron

Reduction of the scale dependence for NLO+NLL predictions, compared with NLO LHC @ 7 TeV[Beenakker, Brensing, Krämer, A.K., Laenen, Niessen’10]Slide45

Stop Resummation

HO10, CERN, 01.07.10

A. Kulesza, Squark and gluino production at hadron colliders

Tevatron

Reduction of the scale dependence for NLO+NLL predictions, compared with NLO LHC @ 7 TeV[Beenakker, Brensing, Krämer, A.K., Laenen, Niessen’10]Beware: large pdf uncertaintiesSlide46

Stop pT

distribution

Tevatron

LHC @7

TeVA. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10[Beenakker, Brensing, Krämer, A.K., Laenen, Niessen’10][Beenakker, Höpker, Spira, Zerwas’97]Slide47

Stop pT

distribution

Tevatron

LHC @7

TeVA. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10K-factors for transverse momentum distributions are not constant and depend on pT![Beenakker, Brensing, Krämer, A.K., Laenen, Niessen’10][Beenakker, Höpker, Spira, Zerwas’97]Slide48

Resummation for pT

distributions

Transverse momentum distributions can also contain logarithmic terms which become large in the threshold limit

Same structure of the threshold resummed cross section in the Mellin moment space (moments taken wrt. ) , soft anomalous dimension a function of

pT .HO10, CERN, 01.07.10A. Kulesza, Squark and gluino production at hadron collidersSlide49

Resummation for pT

distributions

Transverse momentum distributions can also contain logarithmic terms which become large in the threshold limit

Same structure of the threshold resummed cross section in the Mellin moment space (moments taken wrt. ) , soft anomalous dimension a function of

pT .HO10, CERN, 01.07.10A. Kulesza, Squark and gluino production at hadron collidersTevatronLHC@ 7 TeV[Beenakker, Brensing, Krämer, A.K., Laenen, Niessen’10]Slide50

Summary

If SUSY realised

in Nature, squarks

and gluinos will

be produced copiously at the LHCHigher order theoretical predictions for production cross sections at the LHC are needed No discovery: derivation of mass limitsDiscovery: SUSY parameter determinationNLL+NLO, i.e. resummed results matched with NLO SUSY-QCD, are the most accurate preditions currently available for all four processes of squark and gluino production, as well as stop-pair productionThe resummed predictions will be used to improve mass limits at the TevatronHO10, CERN, 01.07.10A. Kulesza, Squark and gluino production at hadron collidersSlide51

PDF Uncertainty

HO10, CERN, 01.07.10

A. Kulesza, Squark and gluino production at hadron collidersSlide52

Stop production at NLO

At NLO also only the diagonal pairs are produced, mixed pairs only at O(α

s4)Very weak dependence of the NLO results on SUSY parameter other than stop mass

NLO calculations used by the Tevatron collaboration to establish mass limits

Stop masses in the range 115-200 GeV, depending on the measurement channel and details of the SUSY model, excluded by Tevatron collaborationsA. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10[Beenakker, Krämer, Plehn, Spira, Zerwas’97]Slide53

Soft anomalous dimensions

Need 1-loop anomalous dimension matrices in order to resum up to NLL

massless 2→n QCD

processes [Kidonakis, Oderda

, Sterman'98] [Bonciani et al.'03][Mert Aybat, Dixon, Sterman'06]massive case: heavy quark pair-production [Kidonakis, Sterman'96][Bonciani et al.'98]Calculation of 1-loop soft anomalous dimension matrices Γij for 2→2 processes with nontrivial colour structure and massive particles in the final stateHO10, CERN, 01.07.10A. Kulesza, Squark and gluino production at hadron collidersOne-loop integrals in the eikonal approximation equal masses [Kidonakis, Sterman'96] unequal masses ( ) [Beenakker, Brensing, Krämer, AK, Laenen, Niessen'09]

Combination with colour structures Γij for , , ,Slide54

NLO corrections

Significant NLO SUSY-QCD corrections

(Note: all

squarks (L,R) mass degenerate apart from stops) HO10, CERN, 01.07.10

A. Kulesza, Squark and gluino production at hadron colliders[Beenakker, Hopker, Spira, Zerwas’97]LHC @ 14 TeVSlide55

At NLL accuracy, soft wide-angle (non-collinear) gluon emission has to be included

Soft non-collinear emission sensitive to the colour structure of the underlying hard scattering processCalculation of 1-loop soft anomalous dimension matrices

ΓJI

for 22 process with nontrivial colour structure and massive particles in the final stateCalculations confirm soft gluon radiation only “feels” the total

colour charge of the heavy particle pair produced at threshold Resummation with colour A. Kulesza, Squark and gluino production at hadron collidersHO10, CERN, 01.07.10same colour structure as in top-antitop production ✓[AK, Motyka’08-’09][Beenakker, Brensing, Krämer, A.K., Laenen, Niessen’09]Slide56

Soft gluon resummation

HO10, CERN, 01.07.10A. Kulesza, Squark and gluino production at hadron colliders

Systematic reorganization of

perturbative series

NLONNLOαsn log 2n(β2)αsn log 2n-1(β2)