Drell-Yan Production Research Articles

Mixed QCD-EW two-loop amplitudes for neutral current Drell-Yan production

We present the mixed QCD-EW two-loop virtual amplitudes for the neutral current Drell-Yan production. The evaluation of the two-loop amplitudes is one of the bottlenecks for the complete calculation of the NNLO mixed QCD-EW corrections. We present the computational details, especially the evaluation of all the relevant two-loop Feynman integrals using analytical and semi-analytical methods. We perform the subtraction of universal infrared singularities and present the numerical evaluation of the hard function.

Fiducial Drell-Yan production at the LHC improved by transverse-momentum resummation at N4LLp+N3LO

Drell-Yan production is one of the precision cornerstones of the LHC, serving as calibration for measurements such as the $W$-boson mass. Its extreme precision at the level of 1% challenges theory predictions at the highest level. We present the first independent calculation of Drell-Yan production at order $\alpha_s^3$ in transverse-momentum ($q_T$) resummation improved perturbation theory. Our calculation reaches the state-of-the-art through inclusion of the recently published four loop rapidity anomalous dimension and three loop massive axial-vector contributions. We compare to the most recent data from CMS with fiducial and differential cross-section predictions and find excellent agreement at the percent level. Our resummed calculation including the matching to $Z$+jet production at NNLO is publicly available in the upcoming CuTe-MCFM 10.3 release and allows for theory-data comparison at an unprecedented level.

Measurement of Mass Dependence of the Transverse Momentum of Lepton Pairs in Drell–Yan Production at \(\sqrt {s}=13\) TeV

Measurement of Mass Dependence of the Transverse Momentum of Lepton Pairs in Drell–Yan Production at \(\sqrt {s}=13\) TeV

Parton distributions and new physics searches: the Drell–Yan forward–backward asymmetry as a case study

We discuss the sensitivity of theoretical predictions of observables used in searches for new physics to parton distributions (PDFs) at large momentum fraction x. Specifically, we consider the neutral-current Drell–Yan production of gauge bosons with invariant masses in the TeV range, for which the forward–backward asymmetry of charged leptons from the decay of the gauge boson in its rest frame is a traditional probe of new physics. We show that the qualitative behaviour of the asymmetry depends strongly on the assumptions made in determining the underlying PDFs. We discuss and compare the large-x behaviour of various different PDF sets, and find that they differ significantly. Consequently, the shape of the asymmetry observed at lower dilepton invariant masses, where all PDF sets are in reasonable agreement because of the presence of experimental constraints, is not necessarily reproduced at large masses where the PDFs are mostly unconstrained by data. It follows that the shape of the asymmetry at high masses may depend on assumptions made in the PDF parametrization, and thus deviations from the traditionally expected behaviour cannot be taken as a reliable indication of new physics. We demonstrate that forward–backward asymmetry measurements could help in constraining PDFs at large x and discuss the accuracy that would be required to disentangle the effects of new physics from uncertainties in the PDFs in this region.

Inclusive production cross sections at N3LO

We present for the first time the inclusive cross section for associated Higgs boson production with a massive gauge boson at next-to-next-to-next-to-leading order in QCD. Furthermore, we introduce n3loxs, a public, numerical program for the evaluation of inclusive cross sections at the third order in the strong coupling constant. Our tool allows to derive predictions for charged- and neutral-current Drell-Yan production, gluon- and bottom-quark-fusion Higgs boson production and Higgs boson associated production with a heavy gauge boson. We discuss perturbative and parton distribution function (PDF) uncertainties of the aforementioned processes. We perform a comparison of global PDF sets for a variety of process including associated Higgs boson production and observe 1σ deviations among predictions for several processes.

Nuclear Modification of Transverse Momentum Dependent Parton Distribution Functions by a Global QCD Analysis.

We perform the first simultaneous global QCD extraction of the transverse momentum dependent (TMD) parton distribution functions and the TMD fragmentation functions in nuclei. We have considered the world set of data from semi-inclusive electron-nucleus deep inelastic scattering and Drell-Yan dilepton production. In total, this data set consists of 90 data points from HERMES, Fermilab, RHIC, and LHC. Working at next-to-leading order and next-to-next-to-leading logarithmic accuracy, we achieve a χ^{2}/d.o.f.=1.196. In this analysis, we perform the first extraction of nuclear modified TMDs and compare these to those in free nucleons. We also make predictions for the ongoing JLab 12GeV program and future electron-ion collider measurements.

Leptoquark production at LHC

Leptoquarks are hypothetical bosonic particles with a unique property; they can transform quarks into leptons and vice versa. There is a large number of scientific articles that cover questions of the leptoquark production and ways of their detection at Large Hadron Collider (LHC). LHC can produce leptoquarks in several different ways. The production mechanism that is best studied in literature is the pair production which is dominant for small Yukawa couplings. However, with the increase of the Yukawa couplings, the phenomenology of leptoquarks becomes more interesting and diverse. Namely, for large Yukawa couplings there are also additional leptoquark production mechanisms: t-channel production, single production, Drell-Yan di-lepton production and a resonant production. Moreover, there has recently been introduced a novel leptoquark production mechanism that is of the t-channel topology which gives asymmetric leptoquark pairs in the final state. The novel production mechanism has the potential to be complementary to other leptoquark production mechanisms in limiting certain parts of the parameter space that is described by the relevant Yukawa couplings and leptoquark masses. This article will provide the most recent studies of that particular leptoquark production mechanism at LHC.

The role of vector boson fusion in the production of heavy vector triplets at the LHC and HL-LHC

We clarify the role of vector boson fusion (VBF) in the production of heavy vector triplets at the LHC and the HL-LHC. We point out that the presence of VBF production leads to an unavoidable rate of Drell-Yan (DY) production and highlight the subtle interplay between the falling parton luminosities and the increasing importance of VBF production as the heavy vector mass increases. We discuss current LHC searches and HL-LHC projections in di-boson and di-lepton final states and demonstrate that VBF production outperforms DY production for resonance masses above 1 TeV in certain regions of the parameter space. We define two benchmark parameter points which provide competitive production rates in vector boson fusion.

Unpolarized transverse momentum distributions from a global fit of Drell-Yan and semi-inclusive deep-inelastic scattering data

We present an extraction of unpolarized transverse-momentum-dependent parton distribution and fragmentation functions based on more than two thousand data points from several experiments for two different processes: semi-inclusive deep-inelastic scattering and Drell-Yan production. The baseline analysis is performed using the Monte Carlo replica method and resumming large logarithms at N3LL accuracy. The resulting description of the data is very good (χ2/Ndat = 1.06). For semi-inclusive deep-inelastic scattering, predictions for multiplicities are normalized by factors that cure the discrepancy with data introduced by higher-order perturbative corrections.

PDF bias and flavor dependence in TMD distributions

Transverse momentum dependent (TMD) distributions match collinear parton density functions (PDF) in the limit of small transverse distances, which is accounted for by global extractions of TMD distributions. We study the influence of the collinear PDF value and uncertainties on the determination of unpolarized TMD distributions and the description of Drell-Yan (DY) and Z-boson production measurements at low transverse momenta. We take into account, for the first time in fits including TMD evolution, flavor-dependent non-perturbative TMD profiles. We carry out a Bayesian analysis to incorporate the propagation of PDF uncertainties into TMD extractions. We find that collinear PDF uncertainties and non-perturbative TMD flavor dependence are both essential to obtain reliable TMD determinations, and should be included in future global analyses.

Soft integrals and soft anomalous dimensions at N3LO and beyond

We calculate soft phase-space and loop master integrals for the computation of color-singlet cross sections through N3LO in perturbative QCD. Our results are functions of homogeneous transcendental weight and include the first nine terms in the expansion in the dimensional regulator ϵ. We discuss the application of our results to the computation of deeply-inelastic scattering and e+e− annihilation processes. We use these results to compute the perturbative coefficient functions for the Drell-Yan and gluon-fusion Higgs boson production cross sections to higher orders in ϵ through N3LO in QCD in the limit where only soft partons are produced on top of the colorless final state. Furthermore, we extract the anomalous dimension of the inclusive threshold soft function and of the N-Jettiness beam and jet functions to N4LO in perturbative QCD.

Monolepton production in SMEFT to mathcal{O} (1/Λ4) and beyond

We calculate pp → ℓ+ν, ℓ− overline{nu} to mathcal{O} (1/Λ4) within the Standard Model Effective Field Theory (SMEFT) framework. In particular, we calculate the four-fermion contribution from dimension six and eight operators, which dominates at large center of mass energy. We explore the relative size of the mathcal{O} (1/Λ4) and mathcal{O} (1/Λ2) results for various kinematic regimes and assumptions about the Wilson coefficients. Results for Drell-Yan production pp → ℓ+ℓ− at mathcal{O} (1/Λ4) are also provided. Additionally, we develop the form for four fermion contact term contributions to pp → ℓ+ν, ℓ− overline{nu} , pp → ℓ+ℓ− of arbitrary mass dimension. This allows us to estimate the effects from even higher dimensional (dimension > 8) terms in the SMEFT framework.

Longitudinal Z-boson polarization and the Higgs boson production cross-section

We present a study of the LHC (and HL-LHC) potential towards a precise determination of the gluon parton distribution function of the proton at intermediate Bjorken-xx from measurements of Drell-Yan production. To this extent, we exploit a clean and theoretically well predicted observable: the Drell-Yan lepton angular coefficient A_0A0, associated with the longitudinal polarization of the Z boson. Through a detailed numerical analysis using the open-source xFitter platform, we illustrate how this observable can provide significant sensitivity over current determinations of the gluon PDF, and a reduction in the PDF uncertainty on the Higgs boson production cross-section by a factor of over 50%.

Master integrals for mixed QCD-QED corrections to charged-current Drell-Yan production of a massive charged lepton

The master integrals for the mixed QCD-QED two-loop virtual corrections to the charged-current Drell-Yan process qoverline{q} ′ → ℓν are computed analytically by using the differential equation method. A suitable choice of master integrals makes it successful to cast the differential equation system into the canonical form. We keep the dependence on charged lepton mass in the building of differential equations and then expand the system against the ratio of small charged lepton mass to large W-boson mass. In such a way the final results will contain large logarithms of the form log( {m}_{ell}^2 / {m}_W^2 ). Finally, all the canonical master integrals are given as Taylor series around d = 4 spacetime dimensions up to order four, with coefficients expressed in terms of Goncharov polylogarithms up to weight four.

Nuclear effects in the deuteron and global QCD analyses

We report the results of a new global QCD analysis, which includes deep-inelastic $e/\mu$ scattering data off proton and deuterium, as well as Drell-Yan lepton pair production in proton-proton and proton-deuterium collisions and $W^\pm/Z$ boson production data from $pp$ and $p \bar p$ collisions at the LHC and Tevatron. Nuclear effects in the deuteron are treated in terms of a nuclear convolution approach with bound off-shell nucleons within a weak binding approximation. The off-shell correction is controlled by a universal function of the Bjorken variable $x$ describing the modification of parton distributions in bound nucleons, which is determined in our analysis along with the parton distribution functions of the proton. A number of systematic studies are performed to estimate the uncertainties arising from the use of various deuterium datasets, from the modeling of higher twist contributions to the structure functions, from the treatment of target mass corrections, as well as from the nuclear corrections in the deuteron. We obtain predictions for the ratios $F_2^n/F_2^p$, and $d/u$, focusing on the region of large $x$. We also compare our results with the ones obtained by other QCD analyses, as well as with the recent data from the MARATHON experiment.

Third-Order Fiducial Predictions for Drell-Yan Production at the LHC.

The Drell-Yan process at hadron colliders is a fundamental benchmark for the study of strong interactions and the extraction of electroweak parameters. The outstanding precision of the LHC demands very accurate theoretical predictions with a full account of fiducial experimental cuts. In this Letter we present a state-of-the-art calculation of the fiducial cross section and of differential distributions for this process at third order in the strict fixed-order expansion in the strong coupling, as well as including the all-order resummation of logarithmic corrections. Together with these results, we present a detailed study of the subtraction technique used to carry out the calculation for different sets of experimental cuts, as well as of the sensitivity of the fiducial cross section to infrared physics. We find that residual theory uncertainties are reduced to the percent level and that the robustness of the predictions can be improved by a suitable adjustment of fiducial cuts.

Testing left-right symmetry with an inverse seesaw mechanism at the LHC

In the left-right symmetric models, a heavy charged gauge boson ${W}^{\ensuremath{'}}$ can decay to a lepton and a right-handed neutrino (RHN). If the neutrino masses are generated through the standard type-I seesaw mechanism, the Yukawa couplings controlling two-body decays of the RHN become very small. As a result, the RHN decays to another lepton and a pair of jets via an off-shell ${W}^{\ensuremath{'}}$. This is the basis of the Keung-Senjanovi\ifmmode \acute{c}\else \'{c}\fi{} (KS) process, which was originally proposed as a probe of lepton number violation at the LHC. However, if a different mechanism like the inverse seesaw generates the neutrino masses, a TeV-scale RHN can have large Yukawa couplings and hence dominantly decay to a lepton and a $W$ boson, leading to a kinematically different process from the KS one. We investigate the prospect of this unexplored process as a probe of the inverse seesaw mechanism in the left-right symmetric models at the High Luminosity LHC (HL-LHC). Our signal arises from the Drell-Yan production of a ${W}^{\ensuremath{'}}$ and leads to two high-${p}_{T}$ same-flavour-opposite-sign leptons and a boosted $W$-like fatjet in the final state. We find that a sequential ${W}^{\ensuremath{'}}$ with mass up to $\ensuremath{\sim}6\text{ }\text{ }\mathrm{TeV}$ along with a TeV-scale RHN can be discovered at the HL-LHC.

Mixed QCD-electroweak corrections to dilepton production at the LHC in the high invariant mass region

We compute mixed QCD-electroweak corrections to the neutral-current Drell-Yan production of a pair of massless leptons in the high invariant mass region. Our computation is fully differential with respect to the final state particles. At relatively low values of the dilepton invariant mass, mℓℓ ∼ 200 GeV, we find unexpectedly large mixed QCD-electroweak corrections at the level of −1%. At higher invariant masses, mℓℓ ∼ 1 TeV, we observe that these corrections can be well approximated by the product of QCD and electroweak corrections. Hence, thanks to the well-known Sudakov enhancement of the latter, they increase at large invariant mass and reach e.g. −3% at mℓℓ = 3 TeV. Finally, we note that the inclusion of mixed corrections reduces the theoretical uncertainty related to the choice of electroweak input parameters to below the percent level.

Linear power corrections for two-body kinematics in the qT subtraction formalism

Transverse-momentum cuts on undistinguished particles in two-body final states induce an enhanced sensitivity to low momentum scales. This undesirable feature, which ultimately leads to an instability of the fixed-order series, poses additional challenges to non-local subtraction schemes. In this letter, we address this issue for general colour-singlet processes within the qT-subtraction formalism, focusing on neutral-current Drell–Yan production. We present a simple procedure to reduce the dependence on the slicing parameter from linear to quadratic, by accounting for the linear power corrections through an appropriate recoil prescription. We observe a dramatical improvement of the numerical convergence and a reduction of the systematic uncertainties. We also discuss how a linear dependence in qT can be avoided for Drell–Yan production by using staggered cuts, which, to the best of our understanding, could be used in experimental analyses. We show that our approach can be successfully applied also to on-shell ZZ production. We finally study diphoton production and verify that our approach is insufficient to capture the linear power corrections introduced by the isolation procedure. The recoil prescription is available in version 2.1 of Matrix.

Transverse momentum distributions in low-mass Drell-Yan lepton pair production at NNLO QCD

The production of lepton pairs at low invariant mass and finite transverse momentum resolves QCD dynamics at the boundary between the perturbative and non-perturbative domains. We investigate the impact of NNLO QCD corrections on these observables at energies corresponding to the BNL RHIC collider and to fixed-target experiments. Satisfactory perturbative convergence is observed in both cases. Only the collider data are found to be well-described by perturbative QCD, thus indicating the importance of non-perturbative effects in lepton-pair transverse momentum distributions at fixed target energies.