We present a detailed comparison of the fixed-order predictions computed by four publicly available computer codes for Drell-Yan processes at the LHC and Tevatron colliders. We point out that while there is agreement among the predictions at the next-to-leading order accuracy, the predictions at the next-to-next-to-leading order (NNLO) differ, whose extent depends on the observable. The sizes of the differences in general are at least similar, sometimes larger than the sizes of the NNLO corrections themselves. We demonstrate that the neglected power corrections by the codes that use global slicing methods for the regularization of double real emissions can be the source of the differences. Depending on the fiducial cuts, those power corrections become linear, hence enhanced as compared to quadratic ones that are considered standard.
We present a simple approach to combine NNLO QCD calculations and parton showers, based on the UNLOPS technique. We apply the method to the computation of Drell-Yan lepton-pair production at the Large Hadron Collider. We comment on possible improvements and intrinsic uncertainties.
Using the technology of the CAESAR approach to resummation, we examine the jet-veto efficiency in Higgs-boson and Drell-Yan production at hadron colliders and show that at next-to-leading logarithmic (NLL) accuracy the resummation reduces to just a Sudakov form factor. Matching with NNLO calculations results in stable predictions for the case of Drell-Yan production, but reveals substantial uncertainties in gluon-fusion Higgs production, connected in part with the poor behaviour of the perturbative series for the total cross section. We compare our results to those from POWHEG with and without…
We compute the rapidity distribution of the virtual photon produced in the Drell-Yan process through next-to-next-to-leading order in perturbative QCD. We introduce a powerful new method for calculating differential distributions in hard scattering processes. This method is based upon a generalization of the optical theorem; it allows the integration-by-parts technology developed for multi-loop diagrams to be applied to non-inclusive phase-space integrals, and permits a high degree of automation. We apply our results to the analysis of fixed target experiments.
We consider the production of W and Z bosons in hadron collisions. We present a selection of numerical results obtained through a fully exclusive calculation up to next-to-next-to-leading order (NNLO) in QCD perturbation theory. We include the $γ$--$Z$ interference, finite-width effects, the leptonic decay of the vector bosons and the corresponding spin correlations. The calculation is completely realistic, since it allows us to apply arbitrary kinematical cuts on the final-state leptons and the associated partons, and to compute the corresponding distributions in the form of bin histograms.
We discuss the influence of fixed target Drell-Yan data on the extraction of parton distribution functions at next-to-next-to-leading order (NNLO) in QCD. When used in a parton distribution fit, the Drell-Yan (DY) data constrain sea quark distributions at large values of Bjorken x. We find that not all available DY data are useful for improving the precision of parton distribution functions (PDFs) obtained from a fit to the deep inelastic scattering (DIS) data. In particular, some inconsistencies between DIS-based parton distribution functions and DY data for large values of dilepton rapidity …
We present the full next-to-next-to-leading order (NNLO) corrections to the coefficient function for the polarized cross section $d Δσ/d Q$ of the Drell-Yan process. We study the effect of these corrections on the process $p+p\to l^+l^-+`X'$ at an C.M. energy $\sqrt{S}=200 GeV$. All QCD partonic subprocesses have been included provided the lepton pair is created by a virtual photon, which is a valid approximation for a lepton pair invariant mass $Q<50 GeV$. For this reaction the dominant subprocess is given by $q+\bar q\to γ^*+`X'$ and its higher order corrections so that it provides us with a…
We present a next-to-next-to-leading order accurate description of Drell-Yan lepton pair production processes through $γ^*/Z$ or $W$ exchange that includes consistently parton shower effects. Results are obtained by upgrading the vector-boson plus one jet NLO calculation in POWHEG with the MiNLO procedure and by applying an appropriate reweighting procedure making use of the DYNNLO program. We compare to existing data and to accurate resummed calculations.
We present a comparative study of the invariant mass and rapidity distributions in Drell-Yan lepton pair production, with particular emphasis on the role played by the QCD evolution. We focus our study around the Z resonance ($50 <Q < 200$ GeV) and perform a general analysis of the factorization/renormalization scale dependence of the cross sections, with the two scales included both in the evolution and in the hard scatterings. We also present the variations of the cross sections due to the errors on the parton distributions (pdf's) and an analysis of the corresponding $K$-factors. Prediction…
Drell-Yan lepton pairs with finite transverse momentum are produced when the vector boson recoils against (multiple) parton emission(s), and is determined by QCD dynamics. At small transverse momentum, the fixed order predictions break down due to the emergence of large logarithmic contributions. This region can be studied via the $p_T^Z$ distribution constructed from the energies of the leptons, or through the $ϕ^*$ distribution that relies on the directions of the leptons. For sufficiently small transverse momentum, the $ϕ^*$ observable can be measured experimentally with better resolution. …
We present results for Drell-Yan production from the GENEVA Monte-Carlo framework. We combine the fully-differential NNLO calculation with higher-order resummation in the 0-jettiness resolution variable. The resulting parton-level events are further combined with parton showering and hadronization provided by PYTHIA8. The 0-jettiness resummation is carried out to NNLL', which consistently incorporates all singular virtual and real NNLO corrections. It thus provides a natural perturbative connection between the NNLO calculation and the parton shower regime, including a systematic assessment of …
We calculate the Mellin moments of next-to-next-to-leading order coefficient functions of the Drell-Yan and Higgs production cross sections. The results can be expressed in term of finite harmonic sums which are maximally threefold up to weight four. Various algebraic relations among these finite sums reduce the complexity of the results suitable for fast numerical evaluations. It is shown that only five non--trivial functions occur besides Euler's $ψ$--function in the representation of these Wilson coefficients.
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 ener…
We consider the production of pairs of lepton through the Drell-Yan process at the LHC and present the most accurate prediction on their rapidity distribution. While the fixed order prediction is already known to next-to-next-to-leading order in perturbative QCD, the resummed contribution coming from threshold region of phase space up to next-to-next-to-leading logarithmic (NNLL) accuracy has been computed in this article. The formalism developed in [1-3] has been used to resum large threshold logarithms in the two dimensional Mellin space to all orders in perturbation theory. We have done a d…
We analyse polarised Drell-Yan process using the factorisation method and derive operator definitions for polarised parton distribution functions. We demonstrate that a factorisation analogous to that in the unpolarised Drell-Yan case holds in this process. We study the leading order gluonic contribution to the first moment of polarised Drell-Yan function and show that it is consistent with results obtained from polarised deep inelastic scattering.
Several properties of high energy hadronic collisions are illustrated by comparing DIS and the Drell-Yan process within a scalar QED model. Diffraction and transverse momentum broadening within the target system are found to be non-universal. Here these effects are simply due to the Coulomb phase shift in the Drell-Yan production amplitude.
We calculate the one-loop QCD correction for inclusive jet cross section and Drell-Yan process in a general low-energy effective Lagrangian for composite quarks and leptons.
We study angular distributions of Drell-Yan leptons in the proton-proton collisions invoking the hypothesis of quark Reggeization in t-channel exchanges at high energy.
The longitudinally polarized Drell-Yan process is one of most powerful tools to probe the structure of hadrons. By means of the recent formalism of the polarized proton-deuteron(pd) Drell-Yan, we calculate the ratio of the proton-deuteron Drell-Yan cross section to the proton-proton(pp) one $Δσ_{pd}/2Δσ_{pp}$in the polarized case.The theoretical results can be compared with future experimental data to confirm the nuclear effect due to the six-quark cluster in deuteron .
Dimensional continuation is applied to resummed expressions for the DIS and Drell-Yan partonic cross sections, to regularize the Landau pole. Simple analytic expression are obtained, encoding information about nonperturbative power--suppressed effects.
We briefly discuss the collinear factorization formula for the associated production of one particle and a Drell-Yan pair in hadronic collisions. We outline possible applications of the results to three different research areas.
Next-to-leading order electroweak and QCD radiative corrections to the Drell-Yan process with high dimuon masses for experiments CMS LHC at CERN have been studied in fully differential form. The FORTRAN code READY for numerical analysis of Drell-Yan observables has been presented. The radiative corrections are found to become significant for CMS LHC experiment setup.
We extract the Boer-Mulders functions of valence and sea quarks in the proton from unpolarized $p+D$ Drell-Yan data measured by the FNAL E866 Collaboration. Using these Boer-Mulders functions, we calculate the $\cos 2 ϕ$ asymmetries in unpolarized $pp$ Drell-Yan processes, both for the FNAL E866/NuSea and the BNL Relativistic Heavy Ion Collider (RHIC) experiments. We also estimate the $\cos 2 ϕ$ asymmetries in the unpolarized $p\bar{p}$ Drell-Yan processes at GSI.
Production of a forward Drell-Yan lepton pair accompanied by a jet separated by a large rapidity interval is proposed to study the BFKL evolution at the LHC. Several observables to be measured are presented including the azimuthal angle dependence of the lepton pair which allows to determine Drell-Yan structure functions.
We present the analytic computation of leading high-energy logarithms of the inclusive Drell-Yan and vector boson production cross-section. We also study the phenomenological relevance of the high-energy corrections for Drell-Yan processes at the LHC. We find that the resummation corrects the NNLO result by no more than a few percent, for values of the invariant mass of the lepton pair below 100 GeV.
The transverse-momentum ($Q_T$) distribution of low-mass Drell-Yan pairs is calculated in QCD perturbation theory with all-order resummation of $α_s (α_s \ln(Q^2_T/Q^2))^n$ type terms. We demonstrate that the rapidity distribution of low-mass Drell-Yan pairs at large-enough transverse momentum is an advantageous source of constraints on the gluon distribution and its nuclear dependence. We argue that low-mass Drell-Yan pairs in the forward region provide a good and clean probe of small-$x$ gluons at collider energies.
The transverse momentum distribution of low-mass Drell-Yan pairs is calculated in QCD perturbation theory with all-order resummation. We argue that at LHC energies the results should be reliable for the entire transverse momentum range. We demonstrate that the transverse momentum distribution of low-mass Drell-Yan pairs is an advantageous source of constraints on the gluon distribution and its nuclear dependence.
Forward Drell-Yan process at the LHC probes the proton structure at very small Bjorken-$x$ and moderate hard scales. In this kinematical domain higher twist effects may be significant and introduce sizeable corrections to the standard leading twist description. We study the forward Drell-Yan process beyond the leading twist approximation within the color dipole model framework that incorporates multiple scattering effects. We derive the Mellin representation of the forward Drell-Yan impact factors for fully differential cross-sections. These results combined with the color dipole cross-section…
The Helicity Structure Functions in the Drell-Yan process are discussed in a framework of Parton Reggeization Approach, which includes the transverse momentum of initial-state partons in a way compatible with QED gauge-invariance. Relationships with conventional Transverse Momentum Dependent Parton Model formalism are clarified.
The unitarity corrections effects encoded in the Glauber-Mueller approach are taken into account to calculate the differential cross sections in the Drell-Yan process in the rest frame. A detailed study of the Drell-Yan process in terms of the $γ^{*}q$ transverse separation and the color dipole size, as well as the effective dipole cross section is performed and compared with the available small $x$ data. Estimates for the Drell-Yan cross section at RHIC energies are presented and discussed.
We present prospects and requirements for the study at HERA of hard photon processes which generate high $p_T$ photons in the final state, and processes which generate Drell-Yan lepton pairs.
We study the power corrections to the cross-section of Drell-Yan production within the Wilson line approach and apply the methods of QCD asymptotic dynamics to identify the leading renormalon contribution.
On the basis of a fit to the Sivers effect in deep-inelastic scattering, we make predictions for single-spin asymmetries in the Drell-Yan process at RHIC.
We consider the leading and sub-leading twist $T$-odd and even contributions to the $\cos 2ϕ$ azimuthal asymmetry in unpolarized dilepton production in Drell-Yan Scattering and semi-inclusive deep inelastic scattering of pions.
We set tight constraints on the energy loss of hard quarks in nuclear matter from NA3 Drell-Yan measurements. Our estimate then allows for the description of HERMES preliminary deep inelastic scattering data on hadron production.
We calculate the transverse momentum distribution of low-mass Drell-Yan pairs in QCD perturbation theory with all-order resummation. We demonstrate that the transverse momentum distribution of low-mass Drell-Yan pairs is an advantageous source of constraints on the gluon distribution and its nuclear dependence. With the reduction in background, we argue that low-mass Drell-Yan pairs in the forward region provide a good and clean probe of small-x gluons at RHIC and LHC.
In this talk, we discuss recent developments in combining parton showers and fixed-order calculations. We focus on the UNNLOPS method for matching next-to-next-to-leading order computations to the parton shower, and we present results from Sherpa for Drell-Yan lepton-pair and Higgs-boson production at the LHC.
We briefly discuss the collinear factorization formula for the associated production of one particle and a Drell-Yan pair in hadronic collisions. We outline possible applications of the results to three different research areas.
Based on a recent work on the quantum chromodynamic (QCD) factorization for semi-inclusive deep-inelastic scattering (DIS), we present a set of factorization formulas for the spin-dependent DIS and Drell-Yan cross sections at low transverse momentum.
We study the renormalization of the Wilson loop with a path corresponding to the Drell-Yan lepton pair production in two-loop approximation of perturbation theory. We establish the renormalization group equation in next-to-leading order and find a process specific anomalous dimension Gamma_DY in the corresponding approximation.
We calculate the gauge invariant Drell-Yan-like hadron tensors. In connection with new COMPASS results, we propose the single spin asymmetry which probes gluon poles together with chiral-odd and time-odd functions. The relevant pion production as a particular case of Drell-Yan-like process has been discussed. For the meson-induced Drell-Yan process, we model an analog of the twist three distribution function, which is a collinear function in inclusive channel, by means of two non-collinear distribution amplitudes which are associated with exclusive channel. This modelling demonstrates the fund…
Recently, a reconsideration of Drell-Yan cross sections at moderate energies and masses has suggested the possibility of relevant enhancements of the cross sections in some kinematical regions. If confirmed, these predictions could largely affect the planning of Drell-Yan experiments aimed at transverse spin measurements after 2010. More in general, the problem is present of a precision measurement of the $τ$ dependence of Drell-Yan cross sections. Here we discuss the feasibility of such a measurement within short time at the COMPASS apparatus, and its relevance for the PANDA experiment.
The results of a recent calculation of the QCD corrections to the polarized Drell-Yan process are summarized. Some implications for the production of vector bosons at RHIC are discussed.
We revisit the transverse single spin asymmetry in the angular distribution of a Drell-Yan dilepton pair. We study this asymmetry by using twist-3 collinear factorization, and we obtain the same result both in covariant gauge and in the light-cone gauge. Moreover, we have checked the electromagnetic gauge invariance of our calculation. Our final expression for the asymmetry differs from all the previous results given in the literature. The overall sign of this asymmetry is as important as the sign of the Sivers asymmetry in Drell-Yan.
We present state-of-the-art predictions for transverse observables relevant to colour-singlet production at the LHC, in particular the transverse momentum of the colour singlet in gluon-fusion Higgs production and in neutral Drell-Yan lepton-pair production, as well as the $ϕ^*_η$ observable in Drell Yan. We perform a next-to-next-to-next-to-leading logarithmic (N$^3$LL) resummation of such observables in momentum space according to the RadISH formalism, consistently including in our prediction all constant terms of relative order $α_s^3$ with respect to the Born, thereby achieving N$^3$LL$^\p…
The perturbative description of certain differential distributions across a wide kinematic range requires the matching of fixed-order perturbation theory with resummation of large logarithmic corrections to all orders. We present precise matched predictions for transverse-momentum distributions in Higgs boson (H) and Drell-Yan pair (DY) production as well as for the closely related ${ϕ^{*}_η}$ distribution at the LHC. The calculation is exclusive in the Born kinematics, and allows for arbitrary fiducial selection cuts on the decay products of the colour singlets, which is of primary relevance …
Drell Yan production is a sensitive probe of new physics and as such has been calculated to high order in both the electroweak and QCD sectors of the Standard Model, allowing for precision comparisons between theory and data. Here we extend these calculations to the Standard Model Effective field theory (SMEFT) and present the NLO QCD and electroweak contributions to the neutral Drell Yan process that are linear in the Wilson coefficients of the SMEFT theory.
Using a subtraction method, we derive the formulae suitable for use in Monte-Carlo event generators to give the angular distribution for the gluon-quark induced NLO corrections in Drell-Yan lepton pair production. We also give the corresponding helicity density matrix for W and Z boson production.
We estimate the power corrections (infrared renormalon contributions) to the coefficient functions for the differential Drell-Yan cross-section $d^2σ/dQ^2dy$, where $Q^2$ is the mass squared and $y$ the rapidity of the produced lepton pair. We employ the dispersive method based on the analysis of one-loop Feynman graphs containing a massive gluon.
The Drell-Yan process is analyzed in soft-collinear effective theory near the end-point region. It is assumed that the relevant final-state hadron energy $Q(1-z)$ where $z$ is the momentum fraction transferred to the virtual photon is the typical hadronic scale $\simΛ$, thus no intermediate scale exists. It is shown that this setup successfully reproduces the full theory results. We also discuss the factorized soft Wilson lines for the Drell-Yan process.
I present applications of a master formula for next-to-next-to-leading order soft and virtual QCD corrections to various electroweak, Higgs, and supersymmetric processes. They include Drell-Yan and charged Higgs production, single-top production in flavor-changing neutral-current processes, and squark and gluino production.
The Drell-Yan process is a copious source of lepton pairs at high energy and is measured with great precision at the Large Hadron Collider (LHC). Barring any new light particles, beyond the Standard Model effects can be studied in Drell-Yan production using an effective field theory. At tree level, new 4-fermion interactions dominate, while at one loop operators modifying 3-gauge boson couplings contribute effects that are enhanced at high energy. We study the sensitivity of the neutral Drell-Yan process to these dimension-6 operators and compare the sensitivity to that of $W^+W^-$ pair produc…
Radiative corrections to the neutral current Drell--Yan-like processes are considered. Complete one-loop electroweak corrections are calculated within the SANC system. Theoretical uncertainties are discussed. Numerical results are presented for typical conditions of LHC experiments.
The contribution of the sub-process $γq \to q' l_1\bar{l}_2$ in hadron-hadron interactions is considered. It is a part of one-loop electroweak radiative corrections for the Drell-Yan production of lepton pairs at hadron colliders. It is shown that this contribution should be taken into account aiming at the 1% accuracy of the Drell-Yan process theoretical description. Both the neutral and charged current cases are evaluated. Numerical results are presented for typical conditions of LHC experiments.
We compute the QCD$\times$QED (${\cal{O}}(α_s α)$) mixed and QED$^2$ (${\cal{O}}(α^2)$) corrections to the production of an on-shell $Z$ boson in hadronic collisions. We obtain them by profiting from the calculation of the pure QCD terms after taking the corresponding abelian limits. Therefore, we extend the available knowledge up to complete next-to-next-to leading order precision in QCD$\oplus$QED. We present explicit results for the perturbative coefficients and perform the phenomenological analysis at different collider energies with particular emphasis on the mixed corrections. We study t…
We study the polarized Drell-Yan processes from the collision of two spin-1/2 hadrons at order 1/Q based on the framework of transverse momentum dependent factorization.We give the complete twist-three results of total sixteen independent structure functions in terms of twist-two and twist-three transverse momentum dependent distribution functions.
We present next-to-next-to-leading-order (NNLO) results for an exclusive soft function that appears in a recently developed factorization theorem for transverse momentum distributions. The factorization theorem, derived using the Soft Collinear Effective Theory, involves both a soft function and unintegrated nucleon distribution functions fully differential in momentum coordinates. The soft function is given by the vacuum matrix element of soft Wilson lines and is also fully differential in all components. We give results and relevant technical details for the NNLO calculation of the soft func…
We discuss the Drell-Yan dilepton production using the transverse momentum dependent parton distributions evolved with the Catani-Ciafaloni-Fiorani-Marchesini-Kwieciński (CCFM-K) equations in the single loop approximation. Such equations are obtained assuming angular ordering of emitted partons (coherence) for $x\sim 1$ and transverse momentum ordering for $x \ll 1$. This evolution scheme also contains the Collins-Soper-Sterman (CSS) soft gluon resummation. We make a comparison with a broad class of data on transverse momentum spectra of low mass Drell-Yan dileptons.
