Multi-loop Feynman integrals represent an essential building block for the precision physics program at high-energy colliders and beyond. In my talk I will review recent developments concerning their evaluation with the method of differential equations, giving particular emphasis to the so-called canonical form and presenting some examples of phenomenological interest.
I review the theory status of double parton scattering, with emhasis on higher-order raditative corrections.
Measurements of the inclusive and differential cross-sections for top-quark pair and single top production cross sections in proton-proton collisions with the ATLAS detector at the Large Hadron Collider are presented at center-of-mass energies of 8 TeV and 13 TeV. The inclusive measurements reach high precision and are compared to the best available theoretical calculations. These...
The calculation of Feynman Integrals is one of bottlenecks for precision calculations at Next-to-Next-to-leading order and beyond. Differential Equations have proven to be a powerful tool to relieve this bottleneck and have seen a rapid development in the last years. In this talk I will review these recent developments especially focusing on the so-called canonical form. I will present the...
Precise measurements of Higgs boson production in association with top-quark pairs
allow for constraints on the top-quark Yukawa coupling, which in turn is crucial to fully
characterise the scalar sector of the Standard Model and could also open a window on
Beyond-the-Standard-Model interactions. At the Large Hadron Collider, searches for
$t\bar{t}H$ production in the dominant $H \to b...
We present the xFitter project which provides an open-source software framework
for the determination of the proton's parton distribution functions and for the interpretation of the physics analyses in the context of Quantum Chromodynamics.
The project has been used recently for a number of analyses performed by the LHC collaborations and theory community, which are summarised briefly. The...
We discuss the automation of the calculation of leading- and next-to-leading order contributions to short-distance cross sections at hadron colliders. With the new public version of the code MadGraph5_aMC@NLO, not only NLO QCD and EW corrections but also all the subleading contributions in a mixed QCD and EW coupling expansion can now be calculated. We discuss the key features for obtaining...
The investigation of the $pp \rightarrow t {\overline t} H$ process is among the highest priorities of the current LHC physics program. Correspondingly, improvements in precision with which theoretical predictions for this process are known are of central importance. In this talk the recent progress concerning theoretical predictions for the signal will be reviewed.
Calculations for dijet production in diffractive deep-inelastic scattering (DIS) at next-to-next-to-leading order accuracy (NNLO) are presented. The calculations are based on the antenna subtraction formalism and the hard coefficients are convoluted with currently available PDFs for diffractive scattering (DPDFs).
The NNLO predictions are compared to a large number of available measurements...
In this status report on the multi-purpose Monte-Carlo event generator Sherpa
I review recent and ongoing Sherpa studies, as well as the latest
developments of its fixed-order and all-order technologies. Fixed-order
improvements I discuss include fully automated EW corrections and support
for additional loop-induced processes. On the all-order side I cover
Sherpa's parton showers and the...
Abstract: An algorithm for the systematic analytical approximation of multi-scale Feyn-
man integrals will be discussed. The algorithm produces algebraic expressions as functions of
the kinematical parameters and mass scales appearing in the Feynman integrals, allowing
for fast numerical evaluation. The results are valid in all kinematical regions, both above
and below thresholds, up to in...
The parameters of the electroweak theory are determined in a combined electroweak and QCD analysis using all deep-inelastic $e^+p$ and $e^-p$ neutral current and charged current scattering cross sections published by the H1 Collaboration, including data with longitudinally polarised lepton beams. The mass of the $W$ boson in the on-shell scheme is determined as $\mW=80.508\pm 0.115\,\GeV$. The...
A number of Higgs measurements and searches for new phenomena in the Higgs sector rely on identification or vetos of particle jets with fairly low transverse momentum in the range of 20-30 GeV. In these cases uncertainties from the modelling of the parton shower and the underlying event can be sizeable. This talk will give an overview of how these uncertainties enter in several analyses.
I will review recent theory developments for diboson production at the LHC within the puclicly available code MATRIX: With the two lepton plus two neutrino channels, which mix ZZ and WW production, NNLO corrections have been completed to all experimentally relevant leptonic final states for diboson processes. NLO corrections to the loop-induced gg channel are formally of N3LO accuracy, but...
Abstract will be available shortly. The talk has been suggested by the organizer
ATLAS + CMS.
The content of this talk is related to the activities of one the CMS groups (Generator, Forward, SM, Top) and ATLAS groups (PMG, SM, TOP, Forward).
The study of the Higgs boson properties is one of the main tasks of contemporary high-energy physics. Among Higgs properties, its interaction with gluons is interesting since it can be facilitated by yet unknown elementary particles. One of the major sources of uncertainty in the theoretical description of $ggH$ coupling originates from mixed QCD-electroweak contributions. The NLO QCD...
Measurements of the cross sections of the production of two or three electroweak gauge bosons at the LHC constitute stringent tests of the electroweak sector of the Standard Model and provide a model-independent means to search for new physics at the TeV scale. Such studies can be complemented by measurements of vector boson fusion or vector boson scattering processes with one or two gauge...
In this talk I will present our results on the Higgs plus jet production at the large transverse momentum, that is, above the top mass threshold. In particular, it will be shown how corresponding two-loop amplitudes were computed in approximation of nearly massless top quarks.
Precise measurements of the mass of the W boson are important to test the overall consistency of the Standard Model of particle physics. The current best measurements of the W boson mass come from single production measurements at hadron colliders in its decay mode to a lepton (electron or muon) and a neutrino and pair production of W bosons at lepton colliders, where also the decay mode of...
In this talk I show that the $Z$ boson polarization has relevant information to distinguish the signal $pp \to ZH$, $H \to b\bar{b}$ from the dominant background $Zb\bar{b}$, which is part of the $\mathcal{O}(\alpha_s^2)$ correction to the Drell-Yan $Z$ production, and can help us to finally observe the largest Higgs boson branching ratio.
The strong coupling constant $\alpha_s$ is determined from inclusive jet and dijet cross sections in neutral-current deep-inelastic ep scattering (DIS) measured at HERA by the H1 collaboration using next-to-next-to-leading order (NNLO) QCD predictions. The dependence of the NNLO predictions and of the resulting value of $\alpha_s(m_Z)$ at the $Z$-boson mass $m_Z$ are studied as a function of...
I will present a calculation of the leading-colour five-gluon amplitude at two loop in QCD. The calculation is performed by means of D-dimensional integrand reduction method, complemented with the finite-field reconstruction techniques and momentum twistor parameterization. Numerical results for all helicity configurations are obtained by employing both sector decomposition methods and IBP...
We present a direct space resummation formalism for colour singlet production in hadronic collisions. We focus on N3LL results for Higgs boson production in gluon-gluon fusion as well as results for Drell-Yan production, we show predictions with phenomenological cuts matched to NNLO fixed-order predictions.
In this talk, I review recent theoretical developments for VBS processes at the LHC.
I will present a strong coupling constant extraction at next-to-leading order QCD accuracy using ATLAS Z+2,3,4 jets data. This is the first extraction using processes with a dependency on high powers of the coupling constant. The values of the strong coupling constant at the Z mass obtained are compatible with the world average and with uncertainties commensurate with other next-to-leading...
We observe more and more advances in the technology of multiloop calculations.
Hence it is of utmost importance to develope computational frameworks which
can tackle the computational burden presented by the regularization
of up to two unresolved parton emissions coming from the matrix elements.
CoLoRFulNNLO is such a framework built around local subtractions
derived from first principles. In...
The weak boson fusion contribution to Higgs boson production is enhanced significantly by requiring a large invariant mass and rapidity separation between the associated jets. This induces large logarithmic corrections in the prediction for the gluon-fusion background, which are incorporated to all orders within the High Energy Jets (HEJ) formalism. We present HEJ predictions for the...
The strong-coupling constant $\alpha_s(m_Z)$ is measured from the transverse momentum distribution of Z bosons measured at $\sqrt{s} = 1.96$ TeV with the CDF experiment, using predictions based on qt resummation at NNLO+NNLL, as implemented in the DYTURBO program. The measurement is performed through a simultaneous fit of $\alpha_s(m_Z)$, PDFs, and the non-perturbative Sudakov form factor.
This talk describe recent results on the measurement of the Electroweak production of V and VV + jets.
We present measurements of differential jet cross sections over a wide range in transverse momenta from inclusive jets to multi-jet final states. Studies on the impact that these measurements have on the determination of the strong coupling alpha_s as well as on parton density functions are reported.
https://arxiv.org/abs/1712.00480
New Results on Vector Boson Scattering Processes with the ATLAS Detector
Measurements of the cross sections of the vector-boson scattering processes at the LHC constitute stringent tests of the electroweak sector of the Standard Model and provide a model-independent means to search for new physics at the TeV scale. The ATLAS collaboration observed the electroweak production of WZ and...
In this talk, recent results on the calculation of fully differential single-jet production in neutral current deep inelastic scattering at next-to-next-to-next-to leading order (N3LO) in the strong coupling are presented. The results are obtained by the combination of antenna subtraction at next-to-next-to leading order (NNLO) with the method of projection to born. Details of the combination...
The production of Higgs boson pairs (HH) offers a unique opportunity to explore the structure of the Higgs field potential through the determination of the Higgs boson self interaction. Despite being an extremely rare process, with a predicted cross section of about 33 fb at a center-of-mass energy of 13 TeV, variations of the Higgs couplings, or the presence of heavy resonances, might enhance...
The total top-antitop production cross section at hadron colliders is
one of the key observables of the Standard Model. Comparisons of LHC
measurements with theoretical calculations are being used to determine
the top-quark mass and the strong coupling and are included in global
PDF fits. These applications are currently based on calculations at
the next-to-next-to-leading order (NNLO) in QCD...
We consider soft gluon evolution of a system of clusters forming the initial state of the cluster hadronziation model, in order to constrain colour reconnection models from a perturbative point of view.
We show that this ansatz produces clusters with properties attributed to
a colour pre-confined state and find strong evidence for formerly investigated colour reconnection models based on...
The phenomenology of highly energetic jets and their substructure plays an important role for the physics program at the LHC. In recent years various grooming techniques have been proposed that need to be included consistently in perturbative calculations. Within Soft Collinear Effective Theory (SCET) we establish factorization theorems for jet substructure observables measured on an inclusive...
The top quark is unique among the known quarks in that it decays before it has an opportunity to form hadronic bound states. This makes measurements of its properties particularly interesting as one can access directly the properties of a bare quark. The latest measurements of these properties with the ATLAS detector at the LHC are presented using 8 TeV and 13 TeV data. Limits on the rate of...
NLO-subtraction schemes such as CS-dipole-subtraction are indispensable for MC-Generators to calculate real and virtual corrections efficiently. However, those algorithms suffer from numerical inefficiencies and even cause distortions in physical distributions when interfaced with parton showers, if the process in question comprises potentially resonant particles.
In this talk I will elucidate...
Several theories beyond the Standard Model predict the existence of additional neutral or charged Higgs particles, as well as decays of the Higgs boson that are either forbidden or strongly suppressed in the SM.Results from selected recent searches for additional Higgs bosons in different production processes and decay modes, and for BSM decays of the 125 GeV-Higgs boson will be presented.
We present a complete description of top quark pair production in association with a hard photon in the dilepton channel. Our calculation is accurate to NLO in QCD. It is based on matrix elements for e+νeμ−ν¯μbb¯γ production and includes all resonant and non-resonant diagrams, interferences, and off-shell effects of the top quarks and the W gauge bosons. This calculation constitutes the first...
Jets are the experimental signature of energetic quarks and gluons produced in high energy processes. A detailed understanding of both the energy scale and the transverse momentum resolution of jets is of crucial importance for the analysis of perturbative QCD processes. In addition, the substructure, shape and mass of jets is an important tool to separate and study quark and gluon initiated...
I will discuss recent developments in the calculation of next-to-leading power corrections in Drell Yan and other electroweak annihilation processes.
QCD Issues in Searches for New Physics with the ATLAS Detector
The ATLAS experiment at the LHC has a broad search program covering a wide variety of models of physics beyond the Standard Model, from simplified models to UV complete models like supersymmetry. In many searches, the final states include one or more hadronic object, and QCD constitutes a crucial background, the control and...
Rare decays are powerful probes for Physics beyond the Standard Model
(SM), as new particles can have a large impact on physics observables.
Recent results on lepton universality tests and measurements of
branching fractions and angular distributions of rare b->sll decays have
shown tensions with the SM predictions. The LHCb experiment is ideally
suited for the study of the these flavour...
Results of the QCD analysis of a variety of the hard-scattering data is overviewed with a particular focus on determination of the quark distributions in the nucleon. A potential of the recent precise data collected at the LHC for the problem of parton species disentangling is discussed and compared to the impact of the low-energy fixed-target data. Finally, remaining challenges and potential...
Lund diagrams, a representation of the phase space within jets, have long been used in discussing parton showers and resummations. I will point out that they can also serve as a powerful tool for experimentally characterising the radiation pattern within jets. I will briefly comment on some of their analytical properties and highlight their scope for constraining Monte Carlo simulations. I...
The talk should cover W, Z/gamma* measurements sensitive to PDFs, as well as measurements of EW observables which are affected by significant PDF uncertainties (sin2thetaW, W mass).
I will discuss recent developments regarding long-distance effects in B->K(*)l+ l- decays.
Precise knowledge of these effects is needed for the interpretation of the present anomaly seen in the experimental results. The approach I discuss relies on the analytic properties of the hadronic matrix elements. It combines the available theory information beyond the physical phase space with...
The production of prompt isolated photons at hadron colliders provides a stringent test of perturbative QCD and can be used to probe the gluon density function of the proton.
The ATLAS collaboration has performed numerous cross section measurements of prompt photon production, among which are a precise measurement of the production of isolated prompt photons in association with heavy flavor...
The search for CP violation is a large part of the flavour programs at LHCb and the B factories, with pure hadronic decays as the key players. Three-body decays, which form a large part of the B meson branching fraction, contain much more information than two-body decays, because of their non-trivial kinematic structure. Recently, these decays were described using a QCD factorization framework...
Precision measurements of the Drell-Yan production of Z bosons at the LHC provide a benchmark of our understanding of perturbative QCD and electroweak processes and probe the proton structure in a unique way.
ATLAS performed a measurement of the effective leptonic weak mixing angle using electron and muon pairs from Z boson decay at a center of mass energy of 8 TeV. It consists of a set of...
The talk will cover measurements and QCD analyses of inclusive and differential
top quark pairs and single top production, and of jets production, from ATLAS, CMS and LHCb.
We present a new algorithm to incorporate calculations with massive $b$-quarks, usually performed in the four flavour scheme, into a merged simulation obtained in the five flavour scheme. We apply this algorithm to $tt+\mathrm{jets}$ / $ttbb$ production, study the uncertainties of this newly developed method and compare our results to dedicated 4F/5F simulations.
We study the transverse momentum spectrum for Drell-Yan production including the bottom mass effect. The pt-distribution of DY or Z boson is very important observable at the LHC, particularly to the ratio of W boson and Z boson spectrum to precisely measure of the W boson mass. The presence of an extra mass scale namely the bottom mass along with the hard scale and the pt-scale makes it very...
Mellin moments of PDFs are calculable as expectation values of local operators within external states, using Lattice QCD. With sufficiently small statistical and systematic uncertainties, these provide information that will be complementary to parametrizations obtained from global fits to experimental data. I will present such lattice results.
We present our calculation of next-to-leading order QCD effects in single top production for a precision determination of the Wtb coupling. The calculation is performed analytically with an off-shell top quark and includes relevant operators from the Standard Model Effective Field Theory (SMEFT) that modify the Wtb coupling also at next-to-leading order in QCD. We discuss the phenomenological...
I present the recent determination of αs performed by the NNPDF collaboration. I particularly discuss the novel methodology adopted in the fit, as well as the breakdown of the uncertainties.
We present an overview of the current status of calculations for the QCD renormalization constants.
We present color planar and complete light quark QCD contributions to the three loop heavy quark form factors in the case of vector, axialvector, scalar and pseudoscalar currents. We evaluate the master integrals applying a new method based on differential equations for general bases, which is applicable for all first order factorizing systems. The analytic results are expressed in terms of...
Perturbative calculations for many collider observables suffer from large logarithmic corrections associated with soft emissions or radiation collinear to beam or jet directions. Resummation using SCET techniques is based on factorisation theorems, and requires the calculation of jet, soft and beam functions to some perturbative accuracy. This task has up to now mainly been achieved...
The Belle II experiment, now operating at the KEK laboratory in Japan, is a substantial upgrade of both the Belle detector and the KEKB $e^+ e^-$accelerator. It aims to collect 50 times more data than existing B-Factory samples. Belle II is uniquely capable to study the so-called "XYZ" particles: heavy exotic hadrons consisting of more than three quarks. First discovered by Belle, these now...
We will talk about the recent progress in the CTEQ-TEA global analysis.
Starting from a factorization theorem in effective field theory, we derive a parton-shower equation for the resummation of non-global logarithms. We have implemented this shower and interfaced it with a tree-level event generator to obtain an automated framework to resum the leading logarithm of non-global observables in the large-Nc limit. Using this setup, we compute gap fractions for dijet...
Measurements of CP violation are a core part of the LHCb physics
programme and provide sensitivity to angles of the CKM matrix as well as
probing our understanding of the differences between matter and
antimatter. A summary of recent LHCb results are presented, including
the time-dependent B0->Dpi analysis which profits from the largest
flavour tagged sample analysed by LHCb, the world's first...
The total pp cross section is a fundamental observable at the LHC. It can be derived from the measurement of the elastic cross section, using the optical theorem. Measurements of the elastic proton-proton cross section were performed at a center-of-mass energy of 8 TeV at various settings of the beam optics using the ALFA detector.
The ALFA detector is also used to tag forward protons in...
This talk describes the measurement of the jets mass and other jet substructure studies at CMS
We calculate the N-jettiness soft function for tW production up to next-to-next-to-leading order in QCD, which is an important ingredient of the N-jettiness subtraction method for predicting the differential cross sections of massive coloured particle productions. We also compare the results with the predictions from renormalization group equations controlled by the soft anomalous dimension.
In this study, we calculate the mass spectrum, weak decay constants, two photon decay widths, and two gluon decay widths of ground (1S), and radially excited (2S, 3S, 4S) states of pseudoscalar charmoniuum and bottomonium such as η_cand η_b, as well as the mass spectrum, leptonic decay constants and radiative decay widths of ground state (1S) and excited (2S, 1D, 3S, 2D, 4S,3D, 5S, 5D) states...
Latest results from Underlying event measurements from ATLAS and CMS are presented.
