Measurement of electroweak production of a W boson and two forward jets in proton-proton collisions at \( \sqrt{s}=8 \) TeV

Journal of High Energy Physics, Nov 2016

A measurement is presented of the cross section for the electroweak production of a W boson in association with two jets in proton-proton collisions at a center-of-mass energy of 8 TeV. The data set was collected with the CMS detector and corresponds to an integrated luminosity of 19.3 fb−1. The measured fiducial cross section for W bosons decaying to electrons or muons and for p T j1 > 60 GeV, p T j2 > 50 GeV, |η j| < 4.7, and m jj > 1000 GeV is 0.42 ± 0.04 (stat) ± 0.09 (syst) ± 0.01 (lumi) pb. This result is consistent with the standard model leading-order prediction of 0.50 ± 0.02 (scale) ± 0.02 (PDF) pb obtained with MadGraph5_amc@nlo 2.1 interfaced to pythia 6.4. This is the first cross section measurement for this process.

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Measurement of electroweak production of a W boson and two forward jets in proton-proton collisions at \( \sqrt{s}=8 \) TeV

Received: July Measurement of electroweak production of a The CMS collaboration 0 1 2 0 ducial cross section for W bosons 1 University of Maryland, College Park , U.S.A 2 Princeton University , Princeton , U.S.A A measurement is presented of the cross section for the electroweak production of a W boson in association with two jets in proton-proton collisions at a center-of-mass energy of 8 TeV. The data set was collected with the CMS detector and corresponds to an integrated luminosity of 19.3 fb 1 . The measured decaying to electrons or muons and for pTj1 > 60 GeV, pTj2 > 50 GeV, j jj < 4:7, and mjj > 1000 GeV is 0:42 at; p; s; Electroweak interaction; Hadron-Hadron scattering (experiments) - 0:01 (lumi) pb. This result is consistent with the standard model leading-order prediction of 0:50 obtained with MadGraph5 amc@nlo 2.1 interfaced to pythia 6.4. This is the rst cross section measurement for this process. 1 Introduction The CMS detector Simulated samples 2 Event reconstruction and selection Background estimation and signal extraction Systematic uncertainties The CMS collaboration The production of a W or Z boson in association with two jets via the t-channel exchange of an electroweak gauge boson (EW production) plays an important role in testing the gauge sector of the standard model (SM), in particular, aspects of gauge boson self interactions. This process is characterized by the presence of two jets with a large separation in rapidity [1, 2]. Experimental studies of this topology are challenging because of large backgrounds and require a precise understanding of extra quark and gluon emissions computed in quantum chromodynamics (QCD) [3]. Three classes of EW diagrams for ` production in association with two jets are shown in gure 1: a W boson radiating from a quark line (left), a W boson produced through vector boson fusion (VBF) processes involving a W boson and a Z boson (center), and a multiperipheral diagram with no s-channel W boson (right). These diagrams represent the EW signal in this analysis. The study of the EW W+2-jets process is part of a more general investigation of the SM VBF process. These EW processes have been used to investigate the rapidity gaps at hadron colliders [1, 2], as a probe of triple-gauge-boson couplings [4, 5], and as a background to Higgs boson measurements in the VBF channel [6{9]. At the LHC, the EW production of a Z boson in association with forward and backward (8 TeV [10]). The ATLAS Collaboration has published similar results at p jets has been investigated by the CMS Collaboration at a center-of-mass energy of 7 TeV [3] s = 8 TeV [11]. (center) VBF, and (right) multiperipheral processes. The EW production of events with a same-sign W boson pair plus two jets was recently studied by the ATLAS Collaboration [12] and the CMS Collaboration [13] at 8 TeV. This paper presents a measurement of the EW W+2-jets production cross section. in the electron (muon) channel at p s = 8 TeV. The ducial cross section is calculated for W bosons decaying to electrons or muons and for pTj1 > 60 GeV, pTj2 > 50 GeV, j jj < 4:7, and mjj > 1000 GeV. The interference term between EW W+2-jets and QCD W+2-jets is neglected in the calculation of the ducial cross section, and is considered as a source of systematic uncertainty. The data set corresponds to an integrated luminosity of 19.2 (19.3) fb 1 collected by the CMS experiment The CMS detector The central feature of the CMS apparatus is a superconducting solenoid of 6 m internal diameter. Within the solenoid volume are a silicon pixel and strip tracker, a lead tungstate crystal electromagnetic calorimeter (ECAL), and a brass and scintillator hadron calorimeter (HCAL), each composed of a barrel and two endcap sections. Forward calorimeters extend the pseudorapidity [14] coverage provided by the barrel and endcap detectors. are measured in gas-ionization detectors embedded in the steel ux-return yoke outside The silicon tracker measures charged particles within the pseudorapidity range j j < 2:5. It consists of 1440 silicon pixel and 15 148 silicon strip detector modules and is located eld of the superconducting solenoid. For nonisolated particles of 1 < pT < 10 GeV and j j < 1:4, the track resolutions are typically 1.5% in pT and 25{90 (45{150) m in the transverse (longitudinal) impact parameter [15] The electron momentum is estimated by combining the energy measurement in the ECAL with the momentum measurement in the tracker. The momentum resolution for electrons with transverse momentum pT 45 GeV from Z ! ee decays ranges from 1.7% for nonshowering electrons in the barrel region to 4.5% for showering electrons in the endcaps [16]. The electron objects in the transition region between the barrel and endcap (1:44 < j j < 1:57) are less precise. Muons are measured in the range j j < 2:4, with detection planes made using three technologies: drift tubes, cathode strip chambers, and resistive plate chambers. Matching (...truncated)


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V. Khachatryan, A. M. Sirunyan, A. Tumasyan, W. Adam. Measurement of electroweak production of a W boson and two forward jets in proton-proton collisions at \( \sqrt{s}=8 \) TeV, Journal of High Energy Physics, 2016, pp. 147, Volume 2016, Issue 11, DOI: 10.1007/JHEP11(2016)147