Boson Production In Pp Collisions Research Articles

Correction to: Accurate prediction of the $$\phi ^{*}_{\eta }$$ distribution for the forward Z boson production in pp collisions through NNLO+N$$^{3}$$LL

Correction to: Accurate prediction of the $$\phi ^{*}_{\eta }$$ distribution for the forward Z boson production in pp collisions through NNLO+N$$^{3}$$LL

Impact of lepton p T threshold on charge asymmetry predictions for inclusive W boson production in pp collisions at 13 TeV

This paper presents the impact of the lepton transverse momentum threshold on the boson charge asymmetry predictions in perturbative QCD for the inclusive production in proton-proton ( ) collisions. The predictions are obtained at various low- thresholds 20, 25, 30, and 40 GeV in a fiducial region encompassing both the central and forward detector acceptances in terms of the lepton pseudorapidity . The predicted distributions for the lepton charge asymmetry, which is defined by ( ), at the next-to-next-to-leading order (NNLO) accuracy are compared with the CMS and LHCb data at 8 TeV center-of-mass collision energy. The 8 TeV predictions reproduce the data fairly well within the quoted uncertainties. The predictions from the CT14 parton distribution function (PDF) model are in a slightly better agreement with the data over the other PDF sets that are tested. The 13 TeV predictions using various thresholds are reported for and the charge asymmetries that are defined in terms of the differential cross sections in bins of the boson rapidity ( ) and transverse momentum ( ). The NNLO predictions for the , , and distributions are assessed to be in close correlation with the value. The and distributions are particularly shown to be more correlated at a higher threshold. The distributions are also reported from the merged predictions with improved accuracy by the inclusion of the next-to-next-to-next-to-leading logarithm (N3LL) corrections, i.e., at NNLO+N3LL. The predicted distributions from various thresholds represent a finer probe in terms of the capability to provide more constraints on the ratio of and quark distribution functions in the parton momentum fraction range .

Accurate prediction of the $$\phi ^{*}_{\eta }$$ distribution for the forward Z boson production in pp collisions through NNLO+N$$^{3}$$LL

This paper presents a phenomenological study for the differential cross section of the forward Z boson production in leptonic decay channels as a function of the angular variable \(\phi ^{*}_{\eta }\) in proton–proton collisions. The \(\phi ^{*}_{\eta }\) distribution is predicted for the forward pseudorapidity region \(2.0< \eta _{\text {l}} < 4.5\) of the decay leptons at center-of-mass energies of 8, 13, and 14 TeV. Accurate prediction of the \(\phi ^{*}_{\eta }\) distribution is achieved by means of state-of-the-art calculations including fixed-order perturbative QCD and large logarithmic corrections. The predicted distributions are obtained by employing the resummation either at next-to-next-to-leading logarithmic (NNLL) or next-to-NNLL (N\(^{3}\)LL) accuracy which is matched to the perturbative QCD calculation at next-to-next-to-leading order (NNLO) accuracy, that is at NNLO+NNLL and NNLO+N\(^{3}\)LL, respectively. The Z boson \(\phi ^{*}_{\eta }\) variable is experimentally preferable as it has been measured more precisely than the Z boson transverse momentum, though both variables probe the same physics; therefore, an accurate description of the \(\phi ^{*}_{\eta }\) variable is required using theoretical predictions at both NNLO+NNLL and NNLO+N\(^{3}\)LL accuracies. The matched predictions are compared with the available 8-TeV and 13-TeV measurements by the LHCb experiment at the LHC and found to be in good agreement. The 14-TeV predicted distributions at both NNLO+NNLL and NNLO+N\(^{3}\)LL are also reported. In all the predicted results, the NNLO+N\(^{3}\)LL provides more improved accuracy for the reliable description of the \(\phi ^{*}_{\eta }\) distribution throughout its entire phase space region.

Study of CP violation in the process of associated Higgs boson production with a decay into muon pair

After the Higgs boson discovery at the LHC, a lot of additional measurements should be performed to understand in detail the properties of the observed particle. Searches for CP violation in different physics sectors are one of the most promising and important parts of these measurements. Associated Higgs boson production in pp collisions can be a powerful tool for searches for possible CP violation in the Higgs sector. In this paper, the study of CP sensitive observables constructed for a four lepton final state is presented. It is shown that azimuthal angle distributions of leptons in this process demonstrate a strong sensitivity to CP violation at the current limits on Higgs boson coupling parameters and can reveal a genuine mechanism of CP violation.

Measurement of distributions sensitive to the underlying event in inclusive Z boson production in pp collisions at sqrt{s} = 13 TeV with the ATLAS detector

This paper presents measurements of charged-particle distributions sensitive to the properties of the underlying event in events containing a Z boson decaying into a muon pair. The data were obtained using the ATLAS detector at the LHC in proton–proton collisions at a centre-of-mass energy of 13 text {Te}text {V} with an integrated luminosity of 3.2~text{ fb }^{-1}. Distributions of the charged-particle multiplicity and of the charged-particle transverse momentum are measured in regions of the azimuth defined relative to the Z boson direction. The measured distributions are compared with the predictions of various Monte Carlo generators which implement different underyling event models. The Monte Carlo model predictions qualitatively describe the data well, but with some significant discrepancies.

Measurements of W and Z boson production in pp collisions at sqrt{s}=5.02\xa0TeV with the ATLAS detector

Measurements of fiducial integrated and differential cross sections for inclusive W^+, W^- and Z boson production are reported. They are based on 25.0 pm 0.5; mathrm {pb}^{-1} of pp collision data at sqrt{s} = 5.02 TeV collected with the ATLAS detector at the CERN Large Hadron Collider. Electron and muon decay channels are analysed, and the combined W^+, W^- and Z integrated cross sections are found to be sigma _{W^+}= 2266 pm 9~text {(stat)} pm 29~text {(syst)} pm 43~text {(lumi)} pb, sigma _{W^-}= 1401 pm 7~text {(stat)} pm 18~text {(syst)} pm 27~text {(lumi)} pb, and sigma _Z= 374.5 pm 3.4~text {(stat)} pm 3.6~text {(syst)} pm 7.0~text {(lumi)} pb, in good agreement with next-to-next-to-leading-order QCD cross-section calculations. These measurements serve as references for Pb+Pb interactions at the LHC at sqrt{s_{mathrm {NN}}}=5.02 TeV.

Z Boson Production in pp Collisions in the Range of the Center-of-Mass Energy from 7 to 100 TeV

High energy physics colliders have been contributing discoveries of and judgments on particles since the early 20th century. One of the well-known high-energy particle colliders is the large hadron collider (LHC), and its proton-proton collision energies have recently been 7, 8 and 13 TeV with the goal of reaching 14 TeV, which is the maximum capacity of the LHC. However, more physics are still to be explored and tested beyond the energy region of the LHC. Therefore, a new collider bigger than the LHC machine, which will be able to collide protons at a 100-TeV center-of-mass energy, is under consideration by the high-energy physics community. To provide insight into the transition from the LHC to the 100-TeV collider, we investigated some properties of the Z process in the collision-energy range from 7 to 100 TeV by using the HERAPDF2.0, MMHT2014, NNPDF3.1 and CT14 next-to-next-to-leading order (NNLO) parton distribution function (PDF) models at NNLO quantum chromodynamics (QCD). The considered properties are the production rate of the Z boson, the change in the uncertainties caused by the collision energy (PDF, renormalization and factorization scales, strong coupling constant, model and parameterization), the forward-backward asymmetry, and the k-factor of the Z boson.

Measurement of differential cross sections in the kinematic angular variable \u03d5* for inclusive Z boson production in pp collisions at sqrt{s}=8 TeV

Measurements of differential cross sections dσ/dϕ* and double-differential cross sections d2σ/dϕ*d|y| for inclusive Z boson production are presented using the dielectron and dimuon final states. The kinematic observable ϕ* correlates with the dilepton transverse momentum but has better resolution, and y is the dilepton rapidity. The analysis is based on data collected with the CMS experiment at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 fb−1. The normalised cross section (1/σ) dσ/dϕ*, within the fiducial kinematic region, is measured with a precision of better than 0.5% for ϕ* < 1. The measurements are compared to theoretical predictions and they agree, typically, within few percent.

The landscape of W± and Z bosons produced in pp collisions up to LHC energies

We consider a selection of recent experimental results on electroweak W±,Z gauge boson production in pp collisions at BNL RHIC and CERN LHC energies in comparison to prediction of perturbative QCD calculations based on different sets of NLO parton distribution functions including the statistical PDF model known from fits to the DIS data. We show that the current statistical PDF parametrization (fitted to the DIS data only) underestimates the LHC data on W±,Z gauge boson production cross sections at the NLO by about 20%. This suggests that there is a need to refit the parameters of the statistical PDF including the latest LHC data.

Measurement of the transverse momentum spectrum of the Higgs boson produced in pp collisions at sqrt{s}=8 TeV using H \u2192 WW decays

The cross section for Higgs boson production in pp collisions is studied using the H → W+W− decay mode, followed by leptonic decays of the W bosons to an oppositely charged electron-muon pair in the final state. The measurements are performed using data collected by the CMS experiment at the LHC at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 19.4 fb−1. The Higgs boson transverse momentum (pT) is reconstructed using the lepton pair pT and missing pT. The differential cross section times branching fraction is measured as a function of the Higgs boson pT in a fiducial phase space defined to match the experimental acceptance in terms of the lepton kinematics and event topology. The production cross section times branching fraction in the fiducial phase space is measured to be 39 ± 8 (stat) ± 9 (syst) fb. The measurements are found to agree, within experimental uncertainties, with theoretical calculations based on the standard model.

Measurement of forward W and Z boson production in pp collisions at s = 8 $$ \sqrt{s}=8 $$ TeV

Measurements are presented of electroweak boson production using data from $pp$ collisions at a centre-of-mass energy of $\sqrt{s} = 8\mathrm{\,Te\kern -0.1em V}$. The analysis is based on an integrated luminosity of $2.0\mathrm{\,fb}^{-1}$ recorded with the LHCb detector. The bosons are identified in the $W\rightarrow\mu\nu$ and $Z\rightarrow\mu^{+}\mu^{-}$ decay channels. The cross-sections are measured for muons in the pseudorapidity range $2.0 < \eta < 4.5$, with transverse momenta $p_{\rm T} > 20{\mathrm{\,Ge\kern -0.1em V\!/}c}$ and, in the case of the $Z$ boson, a dimuon mass within $60 < M_{\mu^{+}\mu^{-}} < 120{\mathrm{\,Ge\kern -0.1em V\!/}c^{2}}$. The results are \begin{align*} \sigma_{W^{+}\rightarrow\mu^{+}\nu} &= 1093.6 \pm 2.1 \pm 7.2 \pm 10.9 \pm 12.7{\rm \,pb} \, , \sigma_{W^{-}\rightarrow\mu^{-}\bar{\nu}} &= \phantom{0}818.4 \pm 1.9 \pm 5.0 \pm \phantom{0}7.0 \pm \phantom{0}9.5{\rm \,pb} \, , \sigma_{Z\rightarrow\mu^{+}\mu^{-}} &= \phantom{00}95.0 \pm 0.3 \pm 0.7 \pm \phantom{0}1.1 \pm \phantom{0}1.1{\rm \,pb} \, , \end{align*} where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination. The evolution of the $W$ and $Z$ boson cross-sections with centre-of-mass energy is studied using previously reported measurements with $1.0\mathrm{\,fb}^{-1}$ of data at $7\mathrm{\,Te\kern -0.1em V}$. Differential distributions are also presented. Results are in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics.

Recent results on associated vector boson production with the ATLAS and CMS experiments

Several aspects of the associated vector boson production in pp collisions at √s = 7 TeV and √s = 8 TeV at the LHC have been recently investigated by the ATLAS and CMS collaborations. The production cross sections of the W and Z bosons in association with jets, as well as their ratio and the double differential cross section in the Z + jets final state are presented. Measurements of the cross sections of a vector boson (W or Z) in association with heavy flavour jets (b, c) and a top quark pair are also described. The measured cross sections are compared to expectations based on next-to-leading order QCD calculations as well as on Monte Carlo simulations.

Review of single vector boson production in pp collisions at $$\sqrt{s} = 7$$ s = 7 TeV

This review summarises the main results on the production of single vector bosons in the Standard Model, both inclusively and in association with light and heavy flavour jets, at the Large Hadron Collider in proton-proton collisions at a center-of-mass energy of 7 TeV. The general purpose detectors at this collider, ATLAS and CMS, each recorded an integrated luminosity of $\approx 40\,{\rm pb^{-1}}$ and $5\,{\rm fb^{-1}}$ in the years 2010 and 2011, respectively. The corresponding data offer the unique possibility to precisely study the properties of the production of heavy vector bosons in a new energy regime. The accurate understanding of the Standard Model is not only crucial for searches of unknown particles and phenomena but also to test predictions of perturbative Quantum-Chromo-Dynamics calculations and for precision measurements of observables in the electroweak sector. Results from a variety of measurements in which single W or Z bosons are identified are reviewed. Special emphasis in this review is given to interpretations of the experimental results in the context of state-of-the-art predictions.

Determination of the Strange-Quark Density of the Proton from ATLAS Measurements of theW→ℓνandZ→ℓℓCross Sections

A QCD analysis is reported of ATLAS data on inclusive W± and Z boson production in pp collisions at the LHC, jointly with ep deep-inelastic scattering data from HERA. The ATLAS data exhibit sensitivity to the light quark sea composition and magnitude at Bjorken x∼0.01. Specifically, the data support the hypothesis of a symmetric composition of the light quark sea at low x. The ratio of the strange-to-down sea quark distributions is determined to be 1.00−0.28+0.25 at absolute four-momentum transfer squared Q2=1.9 GeV2 and x=0.023.Received 19 March 2012DOI:https://doi.org/10.1103/PhysRevLett.109.012001This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.© 2012 CERN, for the ATLAS Collaboration

Gluon distribution functions and Higgs boson production at moderate transverse momentum

We investigate the gluon distribution functions and their contributions to the Higgs boson production in pp collisions in the transverse momentum dependent factorization formalism. In addition to the usual azimuthal symmetric transverse momentum dependent gluon distribution, we find that the azimuthal correlated gluon distribution also contributes to the Higgs boson production. This explains recent findings on the additional contribution in the transverse momentum resummation for the Higgs boson production as compared to that for electroweak boson production processes. We further examine the small-x naive k_t-factorization in the dilute region and find that the azimuthal correlated gluon distribution contribution is consistently taken into account, and the result agrees with the transverse momentum dependent factorization formalism. We comment on the possible breakdown of the naive k_t-factorization in the dense medium region, due to the unique behaviors for the gluon distributions.

Neutral bilepton boson production in pp collisions from 3-3-1 model

Our aim is to establish some signatures of the extra neutral gauge boson X0, predicted in a version of the SU(3)c x SU(3)L x U(1)x model with right-handed neutrinos, by considering the process p+p → X0 + X0* + X. In this work, we show some results concerning the LHC energy regime (√s = 14 TeV) and projected luminosity. Some distributions are shown and the X0 width is calculated. We conclude that hadron colliders can show a clear signature for the existence of X0 by comparing its production with Z pair production.

Study of di-boson production with the CMS detector at LHC

The relatively high cross sections and the clean signatures of multi-lepton final states make the and pp → WZ0 → 3ℓ(ℓ = e, μ) processes accessible in early CMS data. The CMS potential for the observation and study of these processes is assessed using fully simulated signal and background Monte Carlo samples. The main systematic effects relevant for cross section measurements with 1 fb−1 and 10 fb−1 of data are addressed. We demonstrate that multiple gauge–boson production in pp collisions at LHC energies can be observed in the early phase of the experiment, with an integrated luminosity of or less.

Exclusive Higgs boson production at the CERN LHC: Hard rescattering corrections

We examine, as a correction to the central exclusive Higgs boson production in pp collisions at the LHC, the rescattering of gluonic ladders off the proton. As usual, at the lowest order the hard part of this process can be described as a fusion of two hard gluonic ladders. We calculate corrections to this hard amplitude which are due to rescattering of these ladders. These corrections, which contain high mass diffractive excitations of the proton, have not yet been taken into account by the usual soft survival probabilities. We find that the correction due to the exchange of a single hard rescattering is negative, large and infrared sensitive. As a first step towards a more reliable description we therefore replace the rescattering exchange by a unitarized amplitude using the BK equation which generates the saturation scaleQs(x). We also include a soft gap survival probability factor. We discuss the results and outline possible future strategies. hep-ph/0601128

Observation of W ± and Z 0 through their leptonic decay modes in [formula omitted] and pp collisions

We exploit the results of a recent calculation of first-order QCD corrections to direct lepton production. As a signature of W ± production in pp scattering we present various aspects of the single lepton inclusive cross section including the forward-backward asymmetry. Predictions for polarized proton beams are also made. For Z 0 a better signal is obtained when both leptons are detected. We discuss QCD corrections as well as polarization effects for this channel also. The weak boson production in pp collisions is discussed in the appendix.