Measurement of the W W + W Z cross section and limits on anomalous triple gauge couplings using final states with one lepton, missing transverse momentum, and two jets with the ATLAS detector at s = 7 $$ \sqrt{s}=7 $$ TeV

Abstract

The production of a W boson decaying to eν or µν in association with a W or Z boson decaying to two jets is studied using 4.6 fb −1 of proton-proton collision data at √ s = 7 TeV recorded with the ATLAS detector at the LHC. The combined W W +W Z cross section is measured with a significance of 3.4σ and is found to be 68±7 (stat.)±19 (syst.) pb, in agreement with the Standard Model expectation of 61.1±2.2 pb. The distribution of the transverse momentum of the dijet system is used to set limits on anomalous contributions to the triple gauge coupling vertices and on parameters of an effective-field-theory model. The ATLAS collaboration 26 IntroductionThe study of vector boson pair production at the Large Hadron Collider (LHC) provides an important test of the electroweak sector of the Standard Model (SM) at the highest available energies. Deviations observed in the total or differential cross sections from the SM predictions may arise from anomalous triple gauge boson interactions [1] or from new particles decaying into vector bosons [2]. Vector boson pair production is also an important source of background in studies of the Higgs boson and in searches for signals of physics beyond the SM. The cross sections for W W and W Z production at the LHC have previously been measured in fully leptonic final states [3][4][5][6]. The semileptonic final states suffer from larger backgrounds from W or Z boson production in association with jets, but benefit from significantly larger branching fractions than the fully leptonic states and thus represent important complementary measurements. In this paper the W W + W Z cross section is -1 -JHEP01(2015)049 measured in the νjj ( = e, µ) final state using a data sample of proton-proton (pp) collisions with an integrated luminosity of 4.6 fb −1 collected by the ATLAS detector at the LHC. In addition, the reconstructed dijet transverse momentum distribution is used to set limits on anomalous contributions to the triple gauge coupling vertices (aTGCs), after requiring that the dijet invariant mass is close to the mass of the W or Z boson.The combined W W +W Z production cross section (hereafter, W V cross section, where V = W, Z) has been measured in the νjj final state in proton-antiproton collisions at the Tevatron collider by both the CDF [7] and D0 [8] collaborations, and more recently in pp collisions by the CMS [9] collaboration. Limits on anomalous triple gauge couplings in W V → νjj production have also been presented by CDF [10], D0 [11], and CMS [9]. This paper is organised as follows. The overall analysis strategy is described in section 2 and a short description of the ATLAS detector is given in section 3. The Monte Carlo (MC) simulation used for the signal and background modelling is summarized in section 4. Details of the object and event reconstruction and of the event selection are given in sections 5 and 6 respectively. The method to estimate the signal and background processes is discussed in section 7. The cross section measurement is detailed in section...

Model-independent precision constraints on dimension-6 operators

“…One would expect that the LHC may significantly improve on the LEP-2 constraints; in particular, the blind direction, which is plaguing the interpretation of the LEP-2 data, should be lifted. So far, ATLAS and CMS have delivered the constraints on the anomalous TGCs in the WW, WZ, and Wγ production processes at √ s = 7 TeV [38][39][40]. However, it is difficult to interpret the existing results as constraints on dimension-6 operators in the effective field theory beyond the SM.…”

“…Notice that Ref [12]. uses a different normalization (and notation) with δg dZ;L = (cos θ W /g L )δg Z dL etc, which we also adopt here in Eq (40)…”

CP-violation in the ZZZ and ZWW vertices at e + e − colliders in Two-Higgs-Doublet Models

“…Recent LHC experiments [17,19,21] have constrained the CP-conserving anomalous couplings, but not the CP-violating f Our aim is to determine the CP violating contributions to the ZW W vertex, hence the contributions to f Z 4 .…”

Yang–Mills theories at high energy accelerators

“…10 of Ref. [15]), and their study at high energies continues at the Large Hadron Collider [17,16]. At LHC energies the mutual scattering of electroweak bosons, through processes like those shown in Fig.…”