Anomalous gauge couplings in SHERPA

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1 Anomalous gauge couplings in SHERPA Institute for Particle Physics Phenomenology Dresden, 02/10/2013 Anomalous gauge couplings in SHERPA 1

2 Contents 1 Status of SHERPA 2 Anomalous gauge coupling model in SHERPA 3 Conclusions Anomalous gauge couplings in SHERPA 2

3 Status of SHERPA Anomalous gauge coupling model in SHERPA Conclusions The SHERPA event generator framework Two multi-purpose Matrix Element (ME) generators AMEGIC++ JHEP02(2002)044 COMIX JHEP12(2008)039 CS subtraction EPJC53(2008)501 A Parton Shower (PS) generator CSSHOWER++ JHEP03(2008)038 A multiple interaction simulation à la Pythia AMISIC++ hep-ph/ A cluster fragmentation module AHADIC++ EPJC36(2004)381 A hadron and τ decay package HADRONS++ A higher order QED generator using YFS-resummation PHOTONS++ JHEP12(2008)018 Sherpa s traditional strength is the perturbative part of the event MEPS (CKKW), MC@NLO, MENLOPS, MEPS@NLO full analytic control mandatory for consistency/accuracy JHEP02(2009)007 Anomalous gauge couplings in SHERPA 3

4 Recent developments PS LO LO LO Parton showers resummation of (soft-)collinear limit intrajet evolution matrix elements (ME) and parton showers (PS) are approximations in different regions of phase space MEPS combines multiple LOPS keeping either accuracy NLOPS elevate LOPS to NLO accuracy MENLOPS supplements core NLOPS with higher multiplicities LOPS combines multiple NLOPS keeping either accuracy Anomalous gauge couplings in SHERPA 4

5 Recent developments ME LO LO LO LO Matrix elements fixed-order in α s hard wide-angle emissions interference terms matrix elements (ME) and parton showers (PS) are approximations in different regions of phase space MEPS combines multiple LOPS keeping either accuracy NLOPS elevate LOPS to NLO accuracy MENLOPS supplements core NLOPS with higher multiplicities LOPS MEPS@NLO combines multiple NLOPS keeping either accuracy Anomalous gauge couplings in SHERPA 5

6 Recent developments ME PS LO LO LO LO LO LO LO MEPS (CKKW,MLM) Catani, Krauss, Kuhn, Webber JHEP11(2001)063 Lönnblad JHEP05(2002)046 Höche, Krauss, Schumann, Siegert JHEP05(2009)053 matrix elements (ME) and parton showers (PS) are approximations in different regions of phase space MEPS combines multiple LOPS keeping either accuracy NLOPS elevate LOPS to NLO accuracy MENLOPS supplements core NLOPS with higher multiplicities LOPS combines multiple NLOPS keeping either accuracy Anomalous gauge couplings in SHERPA 6

7 Recent developments PS NLO NLO NLO NLOPS Frixione, Webber JHEP06(2002)029 Nason JHEP11(2004)040, Frixione et.al. JHEP11(2007)070 Höche, Krauss, MS, Siegert JHEP09(2012)049 matrix elements (ME) and parton showers (PS) are approximations in different regions of phase space MEPS combines multiple LOPS keeping either accuracy NLOPS elevate LOPS to NLO accuracy MENLOPS supplements core NLOPS with higher multiplicities LOPS combines multiple NLOPS keeping either accuracy Anomalous gauge couplings in SHERPA 7

8 Recent developments ME PS NLO LO LO LO NLO NLO LO MENLOPS Hamilton, Nason JHEP06(2010)039 Höche, Krauss, MS, Siegert JHEP08(2011)123 Gehrmann, Höche, Krauss, MS, Siegert JHEP01(2013)144 matrix elements (ME) and parton showers (PS) are approximations in different regions of phase space MEPS combines multiple LOPS keeping either accuracy NLOPS elevate LOPS to NLO accuracy MENLOPS supplements core NLOPS with higher multiplicities LOPS combines multiple NLOPS keeping either accuracy Anomalous gauge couplings in SHERPA 8

9 Recent developments ME PS NLO NLO NLO NLO NLO NLO NLO Lavesson, Lönnblad JHEP12(2008)070 Höche, Krauss, MS, Siegert JHEP04(2013)027 Gehrmann, Höche, Krauss, MS, Siegert JHEP01(2013)144 matrix elements (ME) and parton showers (PS) are approximations in different regions of phase space MEPS combines multiple LOPS keeping either accuracy NLOPS elevate LOPS to NLO accuracy MENLOPS supplements core NLOPS with higher multiplicities LOPS combines multiple NLOPS keeping either accuracy Anomalous gauge couplings in SHERPA 9

10 Recent results Fixed-mulitplicity NLOPS pp W + 0, 1, 2, 3jets SHERPA+BLACKHAT pp jets SHERPA+BLACKHAT pp t tb b SHERPA+OPENLOOPS Multijet merging at NLO accuracy (MEPS@NLO) pp W + jets SHERPA+BLACKHAT e + e jets SHERPA+BLACKHAT pp h + jets SHERPA+GOSAM p p t t + jets SHERPA+GOSAM pp 4l + jets SHERPA+OPENLOOPS Höche, Krauss, MS, Siegert Phys.Rev.Lett.110(2013) Höche, MS Phys.Rev.D86(2012) Cascioli, Maierhöfer, Moretti, Pozzorini, Siegert arxiv: Höche, Krauss, MS, Siegert JHEP04(2013)027 Gehrmann, Höche, Krauss, MS, Siegert JHEP01(2013)144 Höche, Krauss, MS, Siegert, in YR3 arxiv: Höche, Huang, Luisoni, MS, Winter Phys.Rev.D88(2013) Cascioli, Höche, Krauss, Maierhöfer, Pozzorini, Siegert arxiv: Anomalous gauge couplings in SHERPA 10

11 Recent results Höche, Krauss, MS, Siegert in preparation pp h+jets NLO; LO) µ R/F [ 1 2, 2] µ def µ Q [ 1 2, 2] µ def µ core = m h NLO dependence for pp h+0,1,2 jets LO dependence for pp h+3 jets Q cut = 20 GeV dσ/dp [pb/gev] Ratio Higgs boson transverse momentum (njet 2) Meps@Nlo µf, µr variation µ Q variation p (H) [GeV] Anomalous gauge couplings in SHERPA 11

12 Recent results pp 4l + 0, 1 jets virtuals from OPENLOOPS µ R/F [ 1 2, 2] µ core µ Q [ 1 2, 2] µ core ( µ core = 1 2 E W + + EW NLO dependence for pp 4l+0,1 jets LO dependence for pp 4l+2 jets Q cut = 20 GeV includes loop-induced processes gg 4l and gg 4l+g, gq 4l+q, q q 4l+g Cascioli, Höche, Krauss, Maierhöfer, Pozzorini, Siegert arxiv: ) dσ/d φ ll[fb] dσ/dσ MEPS@NLO dσ/dσ MEPS@NLO Azimuthal lepton distance(atlas, Njet = 0) MEPS@NLO 4l +0,1j µf,r/2 2µF,R µ Q/ 2 2µ Q Unc. quad. sum MC@NLO 4l NLO4l Sherpa+OpenLoops 0.08 MEPS@LOOP 2 4l +0,1j φ ll Anomalous gauge couplings in SHERPA 12

13 Recent results pp 4l + 0, 1 jets virtuals from OPENLOOPS µ R/F [ 1 2, 2] µ core µ Q [ 1 2, 2] µ core ( µ core = 1 2 E W + + EW NLO dependence for pp 4l+0,1 jets LO dependence for pp 4l+2 jets Q cut = 20 GeV includes loop-induced processes gg 4l and gg 4l+g, gq 4l+q, q q 4l+g Cascioli, Höche, Krauss, Maierhöfer, Pozzorini, Siegert arxiv: ) dσ/dm ll[fb/gev] dσ/dσ MEPS@NLO dσ/dσ MEPS@NLO Leptonpairmass(CMS,Njet =1) Sherpa+OpenLoops MEPS@NLO 4l +0,1j µf,r/2 2µF,R µ Q/ 2 2µ Q Unc. quad. sum MC@NLO 4l NLO4l +1j 0.08 MEPS@LOOP 2 4l +0,1j m ll [GeV] Anomalous gauge couplings in SHERPA 13

14 Anomalous gauge coupling model in SHERPA Gleisberg et.al. JHEP02(2009)007 available since 2005 details of Lagrangian or Feynman rules implemented unitarisation based on form factors e.g. pp W γ/zγ + X Anomalous gauge couplings in SHERPA 14

15 Anomalous gauge coupling model in SHERPA Gleisberg et.al. JHEP02(2009)007 available since 2005 details of Lagrangian or Feynman rules implemented unitarisation based on form factors e.g. pp W γ/zγ + X Anomalous gauge couplings in SHERPA 15

16 Anomalous triple gauge couplings Hagiwara et.al. Nucl.Phys.B282(1987)253 Operators for interaction of two charged and one neutral gauge boson L W W V /g W W V = ig V 1 ( W µν W µ V ν W µv ν W µν) + iκ V W µv ν W µν + iλ V m 2 W λµ W ν µ V νλ W g V 4 W µw ν ( µ V ν + ν V µ ) + g V 5 ɛ µνρσ (W µ ρ W ν )V σ + i κ V 2 ɛµνρσ W µw ν V ρσ + i λ V 2m 2 ɛ µνρσ W µλ W ν λ V ρσ, W V = γ/z, g W W γ = e and g W W Z = e cot θ W g1 V = 1 + g1 V and κ V = 1 + κ V in Standard Model: g1 V = κ V = λ V = g4 V = g5 V = κ V = λ V = 0 Anomalous gauge couplings in SHERPA 16

17 Anomalous triple gauge couplings γ Z ints. Hagiwara et.al. Nucl.Phys.B282(1987)253 ZZV (q 1, q 2, P ) = i ( ) P 2 m 2 ] V [f V m 2 4 (P α g µβ + P β g µα ) + f5 V ɛ µαβρ (q 1 q 2 ) ρ Z ZγV (q 1, q 2, P ) = i ( ) P 2 m 2 [ V h V 1 (q µ 2 gαβ q2 α g µβ ) Γ αβµ Γ αβµ V 3µ (P ) m 2 Z V 1α (q 1 ) + hv 2 m 2 P α [ (P q 2 )g µβ q µ 2 P β] Z ] + h V 3 ɛ µαβρ q 2ρ + hv 4 m 2 P α ɛ µβρσ P ρ q 2σ Z V 2β (q 2 ) in limit on two on-shell coupling to one off-shell gauge boson in general more coupling terms Γ Z Z Z = Γ Z 1Z 2Z3 + Γ Z 2Z 3Z1 + Γ Z 3Z 1Z2 in Standard Model: f4 V = f5 V = h V 1 = h V 2 = h V 3 = 0 Gounaris et.al. Phys.Rev.D62(2000) Anomalous gauge couplings in SHERPA 17

18 Anomalous quartic gauge couplings Quartic interactions respecting SU(2) custodial symmetry Gangemi et.al. hep-ph/ L 4 = α 4 e 4 ( 1 2 W µw µ W ν W ν ( W µ W µ) c 2 W µz µ W ν Z ν + 1 ) W 4c 4 (Z µ Z µ ) 2 W ( (W L 5 = α 5 µ W µ) c 2 W µz µ W ν Z ν + 1 ) W 4c 4 (Z µ Z µ ) 2 W in Standard Model: α 4 = α 5 = 0 Anomalous gauge couplings in SHERPA 18

19 Unitarisation Introduce ŝ dependent form factor a(ŝ) = a 0 (1 + ŝ/λ 2 ) n a coupling parameter Λ new physics scale, typically O(1) O(10) TeV n exponent, typically 2 or 3 m exponent, typically 1 regularises cross sections for suitable Λ, n and m Anomalous gauge couplings in SHERPA 19

20 Unitarisation Introduce ŝ dependent form factor a(ŝ) = a 0 (1 + (ŝ/λ 2 ) m ) n a coupling parameter Λ new physics scale, typically O(1) O(10) TeV n exponent, typically 2 or 3 m exponent, typically 1 regularises cross sections for suitable Λ, n and m Anomalous gauge couplings in SHERPA 20

21 SHERPA s AGC model used in Usage in ATLAS arxiv: neutral triple gauge couplings in ZZ arxiv: neutral triple gauge couplings in ZZ Usage in CMS arxiv: neutral and charged triple gauge couplings in Wγ and Zγ arxiv: neutral triple gauge couplings in ZZ arxiv: neutral and charged triple gauge couplings in Wγ and Zγ arxiv: neutral triple gauge couplings in Zγ CMS-PAS-SMP neutral triple gauge couplings in ZZ Anomalous gauge couplings in SHERPA 21

22 Example results CMS collaboration Phys.Lett.B701(2011) Events / 10 GeV CMS, 36 pb s = 7 TeV 1 Data Wγ MC + backgrounds W+jets Other backgrounds atgc κ γ = 0, λ γ = 0.5 Events / 10 GeV CMS, 36 pb Data 10 1 s = 7 TeV Zγ Z+jets γ atgc h 3 = γ E T [GeV] γ E T [GeV] Example for scan used to derive limits on κ γ, λ γ, h γ 3, hγ 4 with a a/λn. Anomalous gauge couplings in SHERPA 22

23 Example results dσ/dm 3l [pb/gev] dσ/dm 3l [pb/gev] Trilepton invariant mass pp WWW aqgc (LOPS) Λ =5 TeV, n = 2, m = 1 α4 =0.1 α4 =0.01 pp WWW (MC@NLO) pp t tw (MC@NLO) pp WWW (LOPS) m 3l [GeV] Subleading lepton transverse momentum pp WWW aqgc (LOPS) Λ =5 TeV, n = 2, m = 1 α4 =0.1 α4 =0.01 pp WWW (MC@NLO) pp t tw (MC@NLO) pp WWW (LOPS) m 3l [GeV] dσ/dm 3l [pb/gev] dσ/dm 3l [pb/gev] Leading lepton transverse momentum pp WWW aqgc (LOPS) Λ =5 TeV, n = 2, m = 1 α4 =0.1 α4 =0.01 pp WWW (MC@NLO) pp t tw (MC@NLO) pp WWW (LOPS) m 3l [GeV] 3rd lepton transverse momentum pp WWW aqgc (LOPS) Λ =5 TeV n = 2, m = 1 α4 =0.1 α4 =0.01 pp WWW (MC@NLO) pp t tw (MC@NLO) pp WWW (LOPS) m 3l [GeV] pp 3l + MET + X SM signal and backgrounds can be simulated at NLOPS/MEPS@NLO accuracy AGC signal can be simulated at NLOPS accuracy if virtual correction is known MEPS (CKKW) does give the correct shapes Anomalous gauge couplings in SHERPA 23

24 Photon induced processes Archibald, et.al. Nucl.Phys.179(2008) ; Hall, Krauss, Schönherr in preparation Photon initial state γγ X a) γpdf inelastic process probes photon content of proton b) EPA elastic process photon bremsstrahlung (Weizsäcker-Williams approx.) Examples: pp ll + X pp W + W + X MC@NLO (QCD), γpdf, EPA contribs can also be used to probe AGCs 1/σ incl dσ/dmµµ [GeV 1 ] mc@nlo+γpdf mc@nlo mc@nlo+epa mc@nlo Drell-Yan muon pair mass distribution Sherpa CMS data CMS-PAS-SMP Sherpa mc@nlo + γpdf + EPA γpdf MRST2004QED γpdf NNPDF2.3QED mµµ [GeV] Anomalous gauge couplings in SHERPA 24

25 Photon induced processes Archibald, et.al. Nucl.Phys.179(2008) ; Hall, Krauss, Schönherr in preparation Photon initial state γγ X a) γpdf inelastic process probes photon content of proton b) EPA elastic process photon bremsstrahlung (Weizsäcker-Williams approx.) Examples: pp ll + X pp W + W + X MC@NLO (QCD), γpdf, EPA contribs can also be used to probe AGCs Events/5GeV mc@nlo+γpdf mc@nlo mc@nlo+epa mc@nlo Leading lepton transverse momentum in pp W + W ATLAS data Phys.Lett. B712 (2012) Sherpa mc@nlo + γpdf + EPA γpdf MRST2004QED γpdf NNPDF2.3QED p,l1 [GeV] Anomalous gauge couplings in SHERPA 25

26 Matrix element weights and reweighting SHERPA will contain an Python interface (available since SHERPA-2.0.β 2 ) gives access to SHERPA s matrix elements (AMEGIC++ & COMIX) takes external four momenta and flavours returns colour and helicity summed/averaged matrix elements including symmetry and flux factors can be used to reweight a given sample to different AGCs care must be taken for very different values of the AGCs or in the case of the emerging of new Lorentz structures (cannot reweight what is missing in the original sample) Anomalous gauge couplings in SHERPA 26

27 Conclusions including exact soft-gluon colour coherence multijet merging at NLO accuracy preserves NLO accuracy at every jet multiplicity and and all resummation properties of the parton shower extensive implementation of anomalous gauge couplings (atgcs, aqgcs) restrictions in neutral triple AGC sector practically irrelevant when m ll m Z is used in analysis can be embedded in MEPS (multijet merging) can be embedded in MC@NLO, MENLOPS, MEPS@NLO where one-loop is known tools for ME-reweighting provided imminent release SHERPA Anomalous gauge couplings in SHERPA 27

28 Thank you for your attention! Anomalous gauge couplings in SHERPA 28