Cross Section For Electroweak Production Research Articles

Measurement of electroweak Zleft(nu overline{nu}right)gamma jj production and limits on anomalous quartic gauge couplings in pp collisions at sqrt{s} = 13 TeV with the ATLAS detector

The electroweak production of Zleft(nu overline{nu}right)gamma in association with two jets is studied in a regime with a photon of high transverse momentum above 150 GeV using proton–proton collisions at a centre-of-mass energy of 13 TeV at the Large Hadron Collider. The analysis uses a data sample with an integrated luminosity of 139 fb−1 collected by the ATLAS detector during the 2015–2018 LHC data-taking period. This process is an important probe of the electroweak symmetry breaking mechanism in the Standard Model and is sensitive to quartic gauge boson couplings via vector-boson scattering. The fiducial Zleft(nu overline{nu}right)gamma jj cross section for electroweak production is measured to be {0.77}_{-0.30}^{+0.34} fb and is consistent with the Standard Model prediction. Evidence of electroweak Zleft(nu overline{nu}right)gamma jj production is found with an observed significance of 3.2σ for the background-only hypothesis, compared with an expected significance of 3.7σ. The combination of this result with the previously published ATLAS observation of electroweak Zleft(nu overline{nu}right)gamma jj production yields an observed (expected) signal significance of 6.3σ (6.6σ). Limits on anomalous quartic gauge boson couplings are obtained in the framework of effective field theory with dimension-8 operators.

Sensitivity measuring expected on the electromagnetic anomalous couplings in the tt̄γ vertex at the FCC-he

Starting from an effective Lagrangian for the [Formula: see text] interaction of the top-quark, we consider the electroweak production cross-section via charged current and through the [Formula: see text] signal. Further, we derive the sensitivity expected for the magnetic dipole moment [Formula: see text] and the electric dipole moment [Formula: see text] of the top-quark at the Future Circular Collider-hadron electron (FCC-he). We present our study for [Formula: see text], 10 TeV, [Formula: see text], 100, 300, 500, 1000 fb[Formula: see text], [Formula: see text] and [Formula: see text], 80%, [Formula: see text], respectively. We find that the sensitivity estimated on dipole moments of the top-quark is of the order of magnitude [Formula: see text] for both hadronic and leptonic decay modes of [Formula: see text]: [Formula: see text] and [Formula: see text] at 95% C.L. in the hadronic channel with unpolarized electron beam [Formula: see text]. Our results regarding the polarized electron beam for [Formula: see text] and [Formula: see text] are [Formula: see text], [Formula: see text] and [Formula: see text], [Formula: see text] at 95% C.L. in the hadronic channel. The corresponding results for the leptonic channel with [Formula: see text], 80% [Formula: see text] are [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text], [Formula: see text], respectively. The results for [Formula: see text] and [Formula: see text] in the leptonic channel are weaker than those corresponding to the hadronic channel by a factor of 0.75. Given these prospective sensitivities, the FCC-he is an alternative to study the anomalous couplings of the quark-top that would complement the studies of the LHC with cleaner environments.

Measurement of the cross section for electroweak production of a Z boson, a photon and two jets in proton-proton collisions at sqrt{mathrm{s}} = 13 TeV and constraints on anomalous quartic couplings

A measurement is presented of the cross section for electroweak production of a Z boson and a photon in association with two jets (Zγjj) in proton-proton collisions. The Z boson candidates are selected through their decay into a pair of electrons or muons. The process of interest, electroweak Zγjj production, is isolated by selecting events with a large dijet mass and a large pseudorapidity gap between the two jets. The measurement is based on data collected at the CMS experiment at sqrt{s} = 13 TeV, corresponding to an integrated luminosity of 35.9 fb−1. The observed significance of the signal is 3.9 standard deviations, where a significance of 5.2 standard deviations is expected in the standard model. These results are combined with published results by CMS at sqrt{s} = 8 TeV, which leads to observed and expected respective significances of 4.7 and 5.5 standard deviations. From the 13 TeV data, a value is obtained for the signal strength of electroweak Zγjj production and bounds are given on quartic vector boson interactions in the framework of dimension-eight effective field theory operators.

Potential discovery of staus through heavy Higgs boson decays at the LHC

In this work we present a new search strategy for the discovery of staus at the LHC in the context of the minimal supersymmetric standard model. The search profits from the large s-channel b-quark annihilation production of the heavy CP-even and CP-odd Higgs bosons (H/A) which can be attained in regions of tan β ≫ 1 that avoid the stringent H/A → τ+τ− searches via decays into stau pairs. We also focus on regions where the staus branching ratios are dominated by the decays into a tau lepton and the lightest neutralino. Thus the experimental signature consists of final states made up of a tau-lepton pair plus large missing transverse energy. We take advantage of the large stau-pair production cross sections via heavy Higgs boson decays, which are between one or two orders of magnitude larger than the usual electroweak production cross sections for staus. A set of basic cuts allow us to obtain significances of the signal over the SM backgrounds at the discovery level (5 standard deviations) in the next LHC run with a center-of-mass energy of 14 TeV and a total integrated luminosity of only 100 fb−1.

Measurement of the cross section for electroweak production of Zγ in association with two jets and constraints on anomalous quartic gauge couplings in proton–proton collisions at [formula omitted

A measurement is presented of the cross section for the electroweak production of a Z boson and a photon in association with two jets in proton–proton collisions at s=8 TeV. The Z bosons are identified through their decays to electron or muon pairs. The measurement is based on data collected with the CMS detector corresponding to an integrated luminosity of 19.7 fb−1. The electroweak contribution has a significance of 3.0 standard deviations, and the measured fiducial cross section is 1.86−0.75+0.90(stat)−0.26+0.34(syst)±0.05(lumi) fb, while the summed electroweak and quantum chromodynamic total cross section in the same region is observed to be 5.94−1.35+1.53(stat)−0.37+0.43(syst)±0.13(lumi) fb. Both measurements are consistent with the leading-order standard model predictions. Limits on anomalous quartic gauge couplings are set based on the Zγ mass distribution.

Single production ofX±5/3andY∓4/3vectorlike quarks at the LHC

Two triplet vector-like quarks (VLQs) with hypercharges of $Y=2/3, -1/3$ and one singlet scalar boson are embedded in the standard model (SM) to resolve the 750 GeV diphoton excess. The constraints on the tree-level Higgs- and $Z$-mediated flavor-changing neutral currents are discussed in detail. Besides the resolution of excess, it is found that the signal strength of diphoton Higgs decay can have a $10\%$ deviation from the SM prediction and that the upper limits of the branching ratios for rare top-quark decays are $BR(t\to c (h, Z)) < (6.8, 0.48) \times 10^{-5}$. We find that the production cross section of a single VLQ by electroweak processes is larger than that of VLQ-pair by QCD processes. To explore the signals of the heavy VLQs at the LHC, we throughly analyze the production of single $X_{\pm 5/3}$ and $Y_{\mp 4/3}$ via $q_i q'_j$ annihilations in $pp$ collisions at $\sqrt{s}=13$ TeV. It is found that the electroweak production cross sections for $d X_{5/3}$, $u Y_{-4/3} $, and $d Y_{4/3} $ channels with $m_X=m_Y=1$ TeV can be $84.3$, $72.3$, and $157.8$ fb, respectively; and the dominant decay modes are $X_{5/3} \to (c,t) W^+$ and $Y_{-4/3} \to (s,b) W^-$. With adopting kinematic cuts, the significance for $pp\to d W^+ t$ channel can be over $5\sigma$.

Measurement of the electroweak production cross section of same-sign W±W± bosons associated with dijets with the ATLAS detector

A measurement of the production cross section for two same-sign W± bosons in association with dijets was performed using 20.3 fb-1 of proton-proton collision data collected at s=8 GeV with the ATLAS detector. The background-only hypothesis was rejected at the 4.5σ confidence level and the measured fiducial cross section is in agreement with the Standard Model prediction. Evidence for the electroweak component of this process was observed at the 3.6σ level and a measurement of the fiducial cross section for the electroweak production of the W±W±jj final state was reported. The electroweak component contains contributions from vector boson scattering diagrams. Thus, the fiducial cross section measurement was used to derive constraints on exotic contributions to the quartic WWWW gauge boson vertex. In these proceedings, a brief description of the analysis is presented.

Measurement of the electroweak production cross section of Z bosons associated with dijets with the ATLAS detector

A measurement of the fiducial cross section for the electroweak production of two jets in association with a Z-boson, which includes the vector boson fusion process, is presented. The measurement is performed using 20.3 fb-1 of proton-proton collision data collected at a centre-of-mass energy of s=8 TeV by the ATLAS experiment at the Large Hadron Collider. The electroweak component is extracted by a fit to the dijet invariant mass distribution in a fiducial region chosen to enhance the electroweak contribution over the dominant background in which the jets are produced via the strong interaction. The electroweak cross section is in good agreement with the Standard Model expectations and the background-only hypothesis is rejected with significance above the 5σ level. In addition, measurements of cross sections and differential distributions for inclusive Z-boson-plus-dijet production are performed in five fiducial regions, each with different sensitivity to the electroweak contribution. The results are corrected for detector effects and compared to predictions from the Sherpa and Powheg event generators.

Measurement of the hadronic activity in events with a Z and two jets and extraction of the cross section for the electroweak production of a Z with two jets in pp collisions at $ \sqrt{s}=7 $ TeV

Abstract The first measurement of the electroweak production cross section of a Z boson with two jets (Zjj) in pp collisions at $ \sqrt{s}=7 $ TeV is presented, based on a data sample recorded by the CMS experiment at the LHC with an integrated luminosity of 5 fb−1. The cross section is measured for the ℓℓjj (ℓ = e, μ) final state in the kinematic region m ℓℓ &gt; 50 GeV, m jj &gt; 120 GeV, transverse momenta $ p_{\mathrm{T}}^{\mathrm{j}}&gt;25 $ GeV and pseudorapidity |η j| &lt; 4.0. The measurement, combining the muon and electron channels, yields σ = 154 ± 24 (stat.) ± 46 (exp. syst.) ± 27 (th. syst.) ± 3 (lum.) fb, in agreement with the theoretical cross section. The hadronic activity, in the rapidity interval between the jets, is also measured. These results establish an important foundation for the more general study of vector boson fusion processes, of relevance for Higgs boson searches and for measurements of electroweak gauge couplings and vector boson scattering.

Vector boson plus jet physics at CMS

We present recent results on the jet production rates in association with weak vector bosons and their properties using proton-proton collision data collected with the CMS detector. Azimuthal correlations and events shapes in Z + jets events are also shown. A first measurement of the electroweak production cross section of a Z boson with 2 jets is presented, including measurements of the hadronic activity between the two associated jets.

Production ofW/Zin Association with Jets

This article summarizes recent Tevatron and LHC measurements of W/Z production in association with inclusive jets. The di erential cross sections are measured as a function of jet multiplicity and various kine- matic variables of jets or W=Z boson. Third-jet emission probability, angular correlations among reconstructed objects, and an event shape variable are studied. A first measurement of electroweak production cross section of the Z boson with two forward-backward jets is also presented. All results are compared to next-to-leading order perturbative QCD calculations and predictions of simulations that interface matrix-element calculations with parton showers. These studies constrain the backgrounds to searches for physics beyond the standard model.

Next-to-leading order QCD corrections to slepton pair production via vector–boson fusion

Abstract Slepton pairs can be produced in vector–boson fusion processes at hadron colliders. The next-to-leading order QCD corrections to the electroweak production cross section for p p → l ˜ + l ˜ − + 2 jets at order α s α 4 have been calculated and implemented in an NLO parton-level Monte Carlo program. Numerical results are presented for the CERN large hadron collider.