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Particle Physics at the LHC

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Particle Physics at the LHC Triple Gauge Couplings and Quartic Gauge Couplings Particle Physics at the LHC Gernot Knippen Faculty of Mathematics and Physics University of Freiburg June 17, 2014 Gernot Knippen TGC and QGC June 17, 2014 1 / 26 Table of content 1 Theoretical fundamentals Theory of electroweak interactions Effective field theory 2 Limits on anomalous nTGC Lagrangian and possible contributions pp ! ZZ analysis Limits from pp ! ZZ analysis 3 Limits on cTGC Lagrangian pp ! WW analysis Limits from pp ! WW analysis 4 Limits on aQGC Lagrangian pp ! W ±W ±jj analysis Limits from pp ! W ±W ±jj analysis 5 Summary & Outlook Gernot Knippen TGC and QGC June 17, 2014 2 / 26 Theoretical fundamentals Theory of electroweak interactions QED Lagrangian Quantum electrodynamics described by 1 L = ¯(iγµ@ − m) − Q ¯γµ A − F F µν : µ µ 4 µν free fermion propagation (L0) photon kinetic energy fermion photon interaction Theory invariant under local phase transformation (U(1)) 0 iQα(x) ! = e : 0 (Aµ ! Aµ = Aµ + @µχ) Gernot Knippen TGC and QGC June 17, 2014 3 / 26 Theoretical fundamentals Theory of electroweak interactions Electroweak Lagrangian Theory invariant under SU(2)L ⊗ U(1) 0 i ~τ~α(x) i Y β(x) ! = e 2 e 2 : ~τ Y Y L =χ ¯ γµ i@ − g W~ − g 0 B χ + ¯ i@ − g 0 B + L L µ 2 µ 2 µ L R µ 2 µ R kin with gauge invariant term describing gauge field kinetics: 1 1 L = − B Bµν − W~ W~ µν kin 4 µν 4 µν resulting from non-abelian gauge structure . Bµν .= @µBν − @νBµ W~ µν .= @µW~ ν − @νW~ µ + gW~ µ × W~ ν Gernot Knippen TGC and QGC June 17, 2014 4 / 26 Theoretical fundamentals Theory of electroweak interactions Gauge boson self-coupling in the electroweak theory Cubic and quartic interaction terms resulting from Lkin: h µ ν ν µ y µ ν y ν µy y µ ν ν µ i L3 = − ie cot θW @ W − @ W WµZν − @ W − @ W WµZν + WµWν @ Z − @ Z h µ ν ν µ y µ ν y ν µy y µ ν ν µ i − ie @ W − @ W WµAν − @ W − @ W WµAν + WµWν @ A − @ A e2 h i h i L = − (W yW µ)2 − W µyW µyW W ν − e2 cot2 θ W yW µZ Z ν − W yZ µW Z ν 4 2 µ ν W µ ν µ ν 2 sin θW h y µ ν y µ ν y µ ν i − e cot θW 2WµW Zν A − WµZ Wν A − WµA WnuZ 2h y µ ν y µ ν i − e WµW Aν A − WµA Wν A W + W − W + W − Z/γ Z/γ W − W + W − W + Z/γ Gernot Knippen TGC and QGC June 17, 2014 5 / 26 Theoretical fundamentals Effective field theory Effective field theory (EFT) Assumption: New physics separated by different (energy) scale Λ from accessible region. (s Λ2) ! Describe observations by parametrized, most general Lagrangian which recovers the Standard Model in the limit Λ ! 1. (Unitary should be preserved.) ! Model independent approach for physics BSM. Example: Fermi theory of β decay (quartic coupling with coupling strength GF , describing two weak interaction vertices at low energies s MW .) p p n ν¯ ! n ν¯ W − e− e− Gernot Knippen TGC and QGC June 17, 2014 6 / 26 Limits on anomalous nTGC Limits on anomalous neutral triple gauge couplings Gernot Knippen TGC and QGC June 17, 2014 6 / 26 Limits on anomalous nTGC Lagrangian and possible contributions Neutral triple gauge couplings (nTGC) Forbidden in Standard Model but possibly realized as \anomalous" coupling (in EFT approach). Construct Lagrangian from general process properties: • 9 total helicity states but only 7 valid (angular momentum conservation) • bose statistics have to be respected ! Effective ZZV Lagrangian: violating CP invariance 2 e γ µν Z µν σ LZZV = 2 − f4 (@µF ) + f4 (@µZ ) Zσ (@ Zν) MZ ! γ ρ Z ρ ~λξ − f5 (@ Fρλ) + f5 (@ Zρλ) Z Zξ conserving CP invariance Gernot Knippen TGC and QGC June 17, 2014 7 / 26 Limits on anomalous nTGC Lagrangian and possible contributions SM and some new physics contributions to nTGC SM Z NLO and higher order contributions Z ∗/γ∗ V (only CP conserving f5 ) Z MSSM 1-loop (and higher order) contributions from charginos and neutralinos New bosons V CP violating coupling f4 sensitive to two-Higgs-doublet model in 1-loop corrections. Gernot Knippen TGC and QGC June 17, 2014 8 / 26 Limits on anomalous nTGC pp ! ZZ analysis Limits on anomalous nTGC from ZZ production in pp collisions CERN-PH-EP-2012-318 Strategy: Obtain limits on anomalous ZZZ and ZZγ couplings from differential dσZZ cross section Z . dpT Analyse ZZ signal channels: ZZ (∗) ! l+l−l+l− and ZZ ! l+l−νν¯ Gernot Knippen TGC and QGC June 17, 2014 9 / 26 Limits on anomalous nTGC pp ! ZZ analysis Extended-lepton selection Aim: Increase selection acceptance in the ZZ (∗) ! l+l−l+l− channel by using leptons which are normally not used due to detector geometry. Forward spectrometer muons Muons outside the nominal ID range with 2:5 < jηj < 2:7. Are required to have a) full track in muon spectrometer, b) pT > 10 GeV and c) X ET of calorimeter deposites inside ∆R = 0:2 smaller that 15 % of muon pT . Calorimeter-tagged muons Muons in the muon spectrometer limited coverage range jηj < 0:1. Are required to a) have calorimeter deposit consistent with muon which is matched to ID track b) have pT > 20 GeV and c) fulfill same impact parameter and isolation criteria as \standard muons". Gernot Knippen TGC and QGC June 17, 2014 10 / 26 Limits on anomalous nTGC pp ! ZZ analysis Extended-lepton selection Aim: Increase selection acceptance in the ZZ (∗) ! l+l−l+l− channel by using leptons which are normally not used due to detector geometry. Calorimeter-only electrons Electrons outside the ID range with 2:5 < jηj < 3:16. Are required to a) have pT > 20 GeV and b) pass the tight identification requirement. pT is calculated from calorimeter energy and electron direction. Charge is assigned depending on the charge of the other electron(s). At most one lepton from each extended category! Gernot Knippen TGC and QGC June 17, 2014 10 / 26 Limits on anomalous nTGC pp ! ZZ analysis Signal region definitions ZZ(∗) ! l+l−l+l−: • exactly 4 isolated leptons, two same-flavour opposite charge pairs (e+e−e+e−, e+e−µ+µ− or µ+µ−µ+µ−) • ∆R(l1; l2) > 0:2 • ambiguity in lepton combinations removed by choosing combination with lowest jml +l − − MZ j • at least one lepton pair fulfills 66 < ml +l − < 116 GeV (the other ml +l − > 20 GeV) Gernot Knippen TGC and QGC June 17, 2014 11 / 26 Limits on anomalous nTGC pp ! ZZ analysis Signal region definitions ZZ ! l+l−νν¯: 1010 9 ATLAS Data WW 10 + - + - 8 -1 Z+X ZZ→l l l l ∫ Ldt = 4.6 fb - 10 W+X ZZ→l+l νν 107 s = 7 TeV Wγ/Wγ* Total Uncertainty 6 Top → + -νν 10 WZ ZZ l l 5 Events / 5 GeV 10 • exactly 2 leptons of same flavour with 104 103 pT > 20 GeV 102 10 1 • ∆R(l1; l2) > 0:3 10-1 -50 0 50 100 150 Axial-Emiss [GeV] • 76 < ml +l − < 106 GeV T miss ~miss p~Z Z • axial-ET = −ET · =pT > 75 GeV and miss Z Z ATLAS Data WW jE −p j 4 + - + - T T =p < 0:4 -1 Z+X ZZ→l l l l T 10 ∫ Ldt = 4.6 fb - W+X ZZ→l+l νν γ γ 3 s = 7 TeV W /W * Total Uncertainty 10 Top + - Events / 0.1 → νν • jet veto WZ ZZ l l 102 • no additional lepton with 10 10 < pT ≤ 20 GeV 1 10-1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 |Emiss-pZ|/pZ T T T Gernot Knippen TGC and QGC June 17, 2014 11 / 26 Limits on anomalous nTGC pp ! ZZ analysis Background estimation for the ZZ (∗) ! l +l −l +l − channel Background estimated via data-driven (dd.) method N(BG) = [N(lllj) − N(ZZ)] × f − N(lljj) × f 2; where • N(lllj) = number of events with 3 leptons and 1 lepton-like jet satisfying all selection criteria • N(lljj) = number of events with 2 leptons and 2 lepton-like jet satisfying all selection criteria • N(ZZ) = MC estimate for real leptons classified as lepton-like jet • f = ratio of the probability for a non-lepton to satisfy the full lepton selection criteria to the probability for a non-lepton to satisfy the lepton-like jet criteria. Gernot Knippen TGC and QGC June 17, 2014 12 / 26 Limits on anomalous nTGC Limits from pp ! ZZ analysis Determining limits on anomalous nTGC • Couplings are parametrized in form-factor 1.2 ATLAS Data approach + - + - -1 ZZ → l l l l ∫ L dt = 4.64 fb Background (dd.) 1 Total Uncertainty Events / GeV s= 7 TeV fZ=fZ=0.1 + - + - γ4 γ5 0.8 ZZ → l l l l 1 f4=f5=0.1 γ V V f =0.1 f = f −! 0 γ4 i n i;0 0.6 f5=-0.1 (1 + s^=Λ2) s!1 0.4 with n = 3 and Λ = 3 TeV to ensure 0.2 0 50 100 150 200 250 300 350 400 450 unitarity is not violated at LHC energies. pZ [GeV] T • To obtain simulated pZ distributions for T Data ATLAS + - V 2.5 ZZ→l l νν Background -1 different f a reweighting method L dt = 4.6 fb i Total Uncertainty ∫ 2 fZ=fZ=0.1 2 2 γ4 γ5 s= 7 TeV jMj jM j f =f =0.1 ( = ) is used.
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