Outline Introduction and Motivation Inclusion of NLO results in WHIZARD Summary and Outlook Appendix NLO Event Simulation for Chargino Production at the ILC based on hep-ph/0607127, hep-ph/0610401 Tania Robens in collaboration with W. Kilian, J. Reuter RWTH Aachen SUSY 2007, Universit¨ at Karlsruhe Tania Robens NLO Event Simulation for Chargino Production at the ILC SUSY 2007, Universit¨ at Karlsruhe
Outline Introduction and Motivation Inclusion of NLO results in WHIZARD Summary and Outlook Appendix Introduction and Motivation 1 Charginos and Neutralinos in the MSSM Experimental accuracy and NLO results Inclusion of NLO results in WHIZARD 2 Implementation in WHIZARD Photons: fixed order vs resummation Results Summary and Outlook 3 Tania Robens NLO Event Simulation for Chargino Production at the ILC SUSY 2007, Universit¨ at Karlsruhe
Outline Introduction and Motivation Inclusion of NLO results in WHIZARD Summary and Outlook Appendix Charginos and Neutralinos in the MSSM Chargino and Neutralino sector: Reconstruction of SUSY parameters χ ± χ 0 Charginos � i and Neutralinos � i : superpositions of gauge and Higgs boson superpartners Chargino/ Neutralino sector: tan β, µ (Higgs sector), M 1 , M 2 (soft breaking terms) can be reconstructed from χ ± sector χ ± χ ± χ 0 masses of � 1 , � 2 , � 1 , 2 σ in the � (Choi ea 98, 00, 01) low-scale parameters + evolution to high scales (RGEs): ⇒ hint at SUSY breaking mechanism (Blair ea, 02) requires high precision in ew-scale parameter determination Tania Robens NLO Event Simulation for Chargino Production at the ILC SUSY 2007, Universit¨ at Karlsruhe
Outline Introduction and Motivation Inclusion of NLO results in WHIZARD Summary and Outlook Appendix Charginos and Neutralinos in the MSSM Chargino production at the ILC ILC : future e + e − collider, √ s = 500 GeV (1 TeV ) “clean” environment, low backgrounds ⇒ high precision Charginos: (typically) light in the MSSM ⇒ easily accessible at colliders (ILC/ LHC) ⇐ LO production at the ILC: χ + χ + ˜ ˜ e + e + ν e ˜ γ, Z e − χ − ˜ e − χ − ˜ decays: typically long decay chains e.g. e + e − → � ν τ ( → τ + τ − ν τ ¯ χ + τ + χ 0 χ 0 χ − τ − 1 � 1 → ˜ 1 ˜ 1 ν τ ¯ ν τ � 1 � 1 ) Tania Robens NLO Event Simulation for Chargino Production at the ILC SUSY 2007, Universit¨ at Karlsruhe
Outline Introduction and Motivation Inclusion of NLO results in WHIZARD Summary and Outlook Appendix Experimental accuracy and NLO results Experimental accuracy and theoretical next-to-leading-order (NLO) corrections experimental errors: obtained from simulation studies (LHC/ ILC study, Weiglein ea, 04) generate “experimental data” with known SUSY input parameters errors: combination of statistical and systematic errors combined LHC + ILC: � same O errors from fitting routines determining SUSY parameters Theory : Full NLO SUSY corrections for σ ( ee → � χ � χ ) at ILC: in the % regime (Fritzsche ea 04, ¨ Oller ea 04, 05) ⇒ include complete NLO contributions in analyses ⇐ Tania Robens NLO Event Simulation for Chargino Production at the ILC SUSY 2007, Universit¨ at Karlsruhe
Outline Introduction and Motivation Inclusion of NLO results in WHIZARD Summary and Outlook Appendix Experimental accuracy and NLO results Experimental accuracy and theoretical next-to-leading-order (NLO) corrections experimental errors: obtained from simulation studies (LHC/ ILC study, Weiglein ea, 04) generate “experimental data” with known SUSY input parameters errors: combination of statistical and systematic errors combined LHC + ILC: � same O errors from fitting routines determining SUSY parameters Theory : Full NLO SUSY corrections for σ ( ee → � χ � χ ) at ILC: in the % regime (Fritzsche ea 04, ¨ Oller ea 04, 05) ⇒ include complete NLO contributions in analyses ⇐ Tania Robens NLO Event Simulation for Chargino Production at the ILC SUSY 2007, Universit¨ at Karlsruhe
Outline Introduction and Motivation Inclusion of NLO results in WHIZARD Summary and Outlook Appendix Implementation in WHIZARD From σ tot to Monte Carlo event generators MC event generators: Generate event samples (same form as experimental outcome) experiments: see final decay products need to compare with simulated event samples also: important irreducible background effects ( e.g. Hagiwara ea, 05, → talk by J¨ urgen Reuter ) ⇒ include NLO results in Monte Carlo Generators ⇐ MC Generator WHIZARD (W. Kilian, LC-TOOL-2001-039) : so far: LO Monte Carlo Event Generator for 2 → n particle processes includes various physical models (SM, MSSM, non-commutative geometry, little Higgs models), initial state radiation, parton shower models,... Tania Robens NLO Event Simulation for Chargino Production at the ILC SUSY 2007, Universit¨ at Karlsruhe
Outline Introduction and Motivation Inclusion of NLO results in WHIZARD Summary and Outlook Appendix Implementation in WHIZARD From σ tot to Monte Carlo event generators MC event generators: Generate event samples (same form as experimental outcome) experiments: see final decay products need to compare with simulated event samples also: important irreducible background effects ( e.g. Hagiwara ea, 05, → talk by J¨ urgen Reuter ) ⇒ include NLO results in Monte Carlo Generators ⇐ MC Generator WHIZARD (W. Kilian, LC-TOOL-2001-039) : so far: LO Monte Carlo Event Generator for 2 → n particle processes includes various physical models (SM, MSSM, non-commutative geometry, little Higgs models), initial state radiation, parton shower models,... Tania Robens NLO Event Simulation for Chargino Production at the ILC SUSY 2007, Universit¨ at Karlsruhe
Outline Introduction and Motivation Inclusion of NLO results in WHIZARD Summary and Outlook Appendix Implementation in WHIZARD NLO cross section contributions σ tot contributions and dependencies: σ born virtual O ( α ) corrections: σ virt ( λ ) emission of soft/ hard collinear/ hard non-collinear photons: σ soft (∆ E γ , λ ) + σ hc (∆ E γ , ∆ θ γ ) + σ 2 → 3 (∆ E γ , ∆ θ γ ) higher order initial state radiation: σ ISR − σ O ( α ) ISR ( Q ) λ : photon mass , ∆ E γ : soft cut , ∆ θ γ : collinear angle Tania Robens NLO Event Simulation for Chargino Production at the ILC SUSY 2007, Universit¨ at Karlsruhe
Outline Introduction and Motivation Inclusion of NLO results in WHIZARD Summary and Outlook Appendix Implementation in WHIZARD Including FormCalc O ( α ) results in WHIZARD use FeynArts / FormCalc generated code for M virt ( λ ) : virtual corrections f s (∆ E γ , λ ) : soft photon factor ( M born : born contribution) fixed order: integrate over effective matrix element: |M eff | 2 (∆ E γ ) = (1+ f s (∆ E γ , λ )) |M born | 2 + 2 Re ( M born M ∗ virt ( λ )) ∆ E γ : soft photon cut, λ : photon mass in practice: create library from FormCalc code, link this to WHIZARD Tania Robens NLO Event Simulation for Chargino Production at the ILC SUSY 2007, Universit¨ at Karlsruhe
Outline Introduction and Motivation Inclusion of NLO results in WHIZARD Summary and Outlook Appendix Photons: fixed order vs resummation (1): Fixed O ( α ) contributions integrate |M eff | 2 (born/ virtual/ soft photonic part) hard collinear photons: collinear approximation ( M born ) hard non-collinear photons: explicit e e → � χ � χ γ process ( M 2 → 3 born ) corresponds to analytic results in literature (Fritzsche ea/ ¨ Oller ea) Tania Robens NLO Event Simulation for Chargino Production at the ILC SUSY 2007, Universit¨ at Karlsruhe
Outline Introduction and Motivation Inclusion of NLO results in WHIZARD Summary and Outlook Appendix Photons: fixed order vs resummation (1): Fixed O ( α ) contributions integrate |M eff | 2 (born/ virtual/ soft photonic part) + hard collinear photons: collinear approximation ( M born ) + hard non-collinear photons: explicit e e → � χ � χ γ process ( M 2 → 3 born ) corresponds to analytic results in literature (Fritzsche ea/ ¨ Oller ea) problem: too low en- e − e + → ˜ ergy cuts: |M eff | 2 < 0 χ − χ + 1 ˜ 1 LO |M eff | 2 ( − + + − ) ⇒ use negative weights or set M eff = 0 √ s = 1 TeV ∆ E = 10 event generator ∆ E = 0 . 5 specific problem 0 ( σ tot ≥ 0) − 1 − 0.5 0 0.5 1 cos θ M 2 behaviour, different cuts [GeV] Tania Robens NLO Event Simulation for Chargino Production at the ILC SUSY 2007, Universit¨ at Karlsruhe
Outline Introduction and Motivation Inclusion of NLO results in WHIZARD Summary and Outlook Appendix Photons: fixed order vs resummation (2): Resumming leading logs to all orders idea: subtract O ( α ) soft + virtual collinear contributions in M eff : (1 + f s (∆ E γ )) |M born | 2 + 2 Re ( M born M ∗ | � M eff | 2 = virt ) 2 f ISR , O ( α ) (∆ E γ ) |M born | 2 − s fold this with ISR structure function: � � 1 � 1 dx 2 f ISR ( x 1 ) f ISR ( x 2 ) | � M eff | 2 ( s , x i )) d Γ dx 1 0 0 f ISR ( x ): Initial state radiation (Jadach, Skrzypek, Z.Phys. 1991) ⇒ describes collinear (real + virtual) photons in leading log accuracy ⇐ f ISR , O ( α ) : soft integrated O ( α ) contribution s Tania Robens NLO Event Simulation for Chargino Production at the ILC SUSY 2007, Universit¨ at Karlsruhe
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