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
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