This talk will describe analysis using Higgs boson decays to two taus at the ATLAS and CMS experiments, presenting the analysis methods and results. Emphasis will also be put on the QCD aspects that are relevant for the analyses.
Low energy phenomena have been studied in detail at the LHC, providing important input for improving models of non-perturbative QCD effects. The ATLAS collaboration has performed several new measurements in this sector:
We present charged-particle distributions sensitive to the underlying event, measured by the ATLAS detector in proton--proton collisions at a centre-of-mass energy of 13 TeV....
The RHIC beam energy scan program allows for the investigation of the phase diagram of QCD matter by varying the beam energy in the region where the change from crossover to first order phase transition is expected to occur. The nature of the quark-hadron transition can be studied through analyzing the space-time structure of the hadron emission source. One of the best tools to gain...
In high energy physics, exclusive processes are special type of collisions, where both colliding particles remain intact and we observe all of the produced particles. These can be either electroweak (two-photon fusion), strong (double pomeron exchange) or mixed electromagnetic and strong (photoproduction) processes. One of the greatest advantage of these collisions is that there are...
This talk will describe searches for Higgs bosons decaying into two b-quarks at the ATLAS and CMS experiments, presenting the analysis methods and results. Emphasis will also be put on the QCD aspects that are relevant for the analyses.
Bose-Einstein correlations of identical hadrons reveal information about hadron creation from the sQGP formed in ultrarelativistic heavy ion collisions. The measurement of three particle correlations may in particular shed light on hadron creation mechanisms beyond thermal/chaotic emission. In this talk we show the status of PHENIX measurements of three pion correlations as a function of...
Many theories describing physics beyond the Standard Model rely on a large separation of scales. Large scale separation arises in
models with mass-split flavors if the system is conformal in the
ultraviolet but chirally broken in the infrared. Because of the
conformal fixed point, these systems exhibit hyperscaling and a highly
constrained resonance spectrum.
In numerical simulations we...
The impact of nonlinear interaction effects on the total proton-proton cross section is studied. In particular, the relative roles of the perturbative and nonperturbative parton splitting mechanisms are investigated. Additionally, the importance of dynamical higher twist corrections to parton production processes is demonstrated.
A global theoretical description of hadron's transverse momentum spectra in high-energy particle collisions is still an open question today. However, identified hadron spectra measured in the experiments can be described well with non-extensive statistical approach. This method is motivated by the fact that, negative binomial (NBD) multiplicity of the particle number distribution results the...
This talk will describe measurements and searches using Higgs boson decays to two photons at the ATLAS and CMS experiments, presenting the analysis methods and results. Emphasis will also be put on the QCD aspects that are relevant for the analyses.
The most recent results on the production of single W and Z bosons with two jets at high invariant mass at centre-of-mass energies of 7, 8 and 13 TeV are presented. Integrated and differential cross sections are measured in many different phase space regions with varying degree of sensitivity to the electroweak production in vector boson fusion. The cross section for the electroweak W boson...
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...
Measurements of the inclusive and differential top quark pair production cross section in proton-proton collisions at 5.02 TeV, 7 TeV, 8 TeV and 13 TeV are presented using the CMS detector. The total cross section is measured using the lepton+jets, dilepton and fully hadronic channels, including the tau-dilepton and tau+jets modes. Indirect constraints on both the top quark mass and ɑS are...
This talk will describe measurements using Higgs boson decays to 4 leptons at the ATLAS and CMS experiments, presenting the analysis methods and results. Emphasis will also be put on the QCD aspects that are relevant for the analyses.
The production of jets in association with vector bosons is an important process to study QCD in a multi-scale environment. The ATLAS collaboration has performed measurements of vector boson+jets cross sections, differential in several kinematic variables, in proton-proton collision data taken at center-of-mass energies of 8TeV and 13TeV. The measurements are compared to state-of-the art...
I will present a computation of the cross section for Higgs production via gluon fusion that is differential in the Higgs momentum and inclusive with respect to associated QCD radiation.
This calculation is carried out through NNLO in perturbative QCD and includes the O(d-4) pieces which are necessary for UV renormalisation and mass factorisation at N3LO.
First, I will discuss the restriction...
Current predictions for the total top-quark pair production cross section are based on NNLO QCD corrections with NNLL soft-gluon resummation. I will discuss the perspectives to go beyond this approximation by using known ingredients for N3LL soft-gluon resummation and Coulomb corrections.
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 precise measurements of the inclusive production of isolated prompt photons at a center-of-mass energy of 13 TeV, differential in both rapidity and the photon transverse momentum. In...
We discuss a formalism for the resummation of the Higgs transverse momentum, and more in general of inclusive transverse observables, in direct space up to N3LL accuracy. The talk is based on 1604.02191 and 1705.09127.
The production of jets at hadron colliders provides a stringent test of perturbative QCD at the highest energies. The process can also be used to probe the gluon density function of the proton. Specific topologies can be used to extract the strong coupling constant.
The ATLAS collaboration has recently measured the inclusive jet production cross section in data collected at a center-of-mass...
Several measurements of single top quark production in proton-proton collisions at the LHC at centre-of-mass energies of 7, 8 and 13 TeV, using data collected with the CMS experiment, are presented. The analyses investigate separately the productions of top via t-channel exchange, in association with a W boson (tW) or via the s-channel. Final states with at least one charged lepton and one...
This talk will describe the searches for di-Higgs production at the ATLAS and CMS experiments, presenting the analysis methods and results. Emphasis will also be put on the QCD aspects that are relevant for the analyses.
Measurements of the Drell-Yan production of W and Z/gamma bosons at the LHC provide a benchmark of our understanding of perturbative QCD and probe the proton structure in a unique way. The ATLAS collaboration has performed new high precision measurements at center-of-mass energies of 7. The measurements are performed for W+, W- and Z/gamma bosons integrated and as a function of the boson or...
Measurements of the Drell-Yan production of W and Z/gamma bosons at the LHC provide a benchmark of our understanding of perturbative QCD and probe the proton structure in a unique way. The ATLAS collaboration measured the di-lepton mass range up to the TeV scale as well as the triple differential cross-section measurement as a function of Mll, dilepton rapidity and cosθ defined in the...
Measurements of the top quark mass and width using proton-proton collisions at the LHC at centre-of-mass energies of 7, 8 and 13 TeV are presented. The analyses used different decay channels and production modes of the top quark. Several techniques are investigated based on the reconstruction of the top kinematics from final state products, using leptonic decays with a J/psi, the shapes of top...
"The study of Higgs boson properties form an important part of the LHC program. These studies are not only important for a better understanding of electroweak symmetry breaking mechanism but also for BSM searches. For example, most recently a strategy has been proposed to use LHC measurements of the Higgs transverse momentum distribution to constrain the Yukawa couplings of light-generation...
To define precision observables in a way which is most suitable for interpretation
it is convenient to separate electroweak and QCD effects for pp collision processes@LHC. We argue, that for that purpose, choice of orientation of coordinates (in the rest frame of lepton pair) for Drell Yan processes can be beneficial to reduce entanglement of QCD and electroweak effects.
Numerical results...
We present a NLO QCD calculation of ttj production at the LHC in the dilepton channel, where
all non-resonant diagrams, interferences and off-shell effects of the top quark are included. We investigate different choice of dynamical scales in order to stabilize the perturbative convergence of the differential distributions
far away from the threshold. We will also discuss the application of...
Studying the pair production of Higgs bosons at the LHC is important as it is sensitive to the Higgs trilinear coupling. It therefore allows for a direct test of the Higgs potential and the mechanism of electroweak symmetry breaking. Since the heavy top limit provides only a poor description of Higgs boson pair production, a precise theoretical description of this process requires the...
In this talk, we describe the computation of higher-order QED effects relevant in hadronic collisions. We start with a brief discussion about the calculation of mixed QCD-QED one-loop contributions to the Altarelli-Parisi splittings functions. Then, we explain how to extend the DGLAP equations to deal with new parton distributions, emphasizing the consequences of the novel corrections in the...
The LHC experiments have, so far, measured many of the Higgs couplings and found excellent agreement with the minimally-realized electroweak symmetry breaking (EWSB) mechanism in the Standard Model. Nevertheless, there are important couplings that are currently out of reach which test the nature of EWSB and fermion mass generation. This talk will focus on one such coupling: the hhVV coupling....
I will discuss the theoretical uncertainties on the top-quark mass
determination, due to bottom-quark fragmentation in top decays.
In particular, the fragmentation parameters in both HERWIG and PYTHIA, the two main parton shower generators, will be taken into account and their impact on several
observables, relevant form the top-mass extraction, will be investigated.
Furthermore, I will also...
In the high-energy heavy-ion physics community the FORTRAN based HIJING Heavy Ion Jet Interaction Generator code is commonly used, originally developed by Xin-Nian Wang and Miklos Gyulassy [1] -- more than 2 decades ago. Although it was intended to describe the heavy-ion collisions occurring at RHIC energies, it has still many applications with todays higher collision energies. However, the...
This talk will describe searches for physics beyond the SM in final states with Higgs bosons at the ATLAS and CMS experiments, presenting the analysis methods and results. Emphasis will also be put on the QCD aspects that are relevant for the analyses.
We present a formulation for a parton shower at an arbitrary order of perturbation theory, with the aim of indicating how a parton shower can be understood as a systematically improvable approximation, similarly to ordinary perturbative calculations of cross sections. The formalism requires input functions that represent the soft and collinear singularities of QCD at the requisite perturbative...
While large logarithms arising from the IR structure of QCD can be
resummed to higher logarithmic accuracy for specific observables,
numerical calculations based on parton showers are formally correct to
LL only. However, they incorporate additional effects like local
momentum conservation, which are beyond this formal accuracy. As a
first step towards a quantitative study of these effects, a...
Heavy charm and beauty quarks are sensitive probes to study the Quark-Gluon Plasma produced in high-energy heavy-ion collisions. Because of their large masses, they are produced in the initial stage of the collision and therefore explore the entire evolution of the produced medium. ALICE, A Large Ion Collider Experiment located at the Large Hadron Collider at CERN, is a dedicated experiment...
This talk will describe measurements and searches using Higgs boson decays to two W bosons at the ATLAS and CMS experiments, presenting the analysis methods and results. Emphasis will also be put on the QCD aspects that are relevant for the analyses.
Heavy-flavour (beauty and charm) quarks are produced almost
exclusively in initial hard processes, and their yields remain largely
unchanged throughout a heavy-ion reaction.
Nevertheless, they interact with the nuclear matter in all the stages of
its evolution. Thus, heavy quarks serve as ideal self-generated
penetrating probes of the strongly interacting Quark-Gluon Plasma...
The talk will be about the recent calculation of the planar Feynman integrals needed for the two-loop correction to Higgs-plus-jet production (arXiv:1609.06685) with full top-mass dependence, as well as the on-going work on the non-planar parts. I will discuss motivation, integral families, function classes, elliptic integrals, and more.
The improvements of Monte-Carlo event generators in the last decade enable quantitative predictions for the LHC at an unprecedented accuracy.
Combining matrix elements at next-to-leading order in QCD with parton-shower emissions ("matching") and using (N)LO matrix elements for hard emissions at different final-state multiplicities ("merging") led to considerably reduced theoretical...
QCD evolution equations can be recast in terms of parton branching processes. We present a new numerical solution of the equations and show, that this method reproduces the semi-analytical solutions.
We discuss numerical effects of the kinematic boundary of resolvable branchings on the resulting parton distribution functions. We show, how this method can be used to determine Transverse...
We report on our recent progress on the calculation of massive operator matrix elements (OMEs), which at three loop level receive contributions from Feynman diagrams containing two heavy quark lines of different masses. These OMEs are needed in order to obtain the corresponding contributions for the massive Wilson coefficients in deep inelastic scattering at large momentum transfer. They are...
In this talk we review the current status of QCD corrections for Higgs production and decay at the LHC in the context of BSM physics. These corrections are important for two reasons. First, to appreciate possible deviations in the properties of the observed SM-like states due to the effect colored-BSM particles, such as stops, from virtual corrections. Second, QCD corrections are important for...
I am going to present some recent results on the resummation of soft gluon emission corrections to the production of a top-antitop pair in association with a Higgs/W/Z boson at the Large Hadron Collider.
First I will introduce and describe the derivation of the soft-gluon resummation formula for these processes. Based on this formula, we developed a dedicated parton-level Monte Carlo program....
We discuss about radiation from heavy
quarks in the context of next-to-leading order calculations
matched to parton shower generators. A new algorithm for
radiation from massive quarks is presented that offers
advantages over the one previously employed. We implement
the algorithm in the framework of the POWHEG-BOX,
and compare it with the previous one in the case of the hvq
generator for...
After the Higgs boson discovery, LHC can be used as a precision machine to explore its properties. Indeed, in case new resonances will not be found, the only access to New Physics would be via measuring small deviations from the SM predictions. A consistent approach is provided by a bottom-up Effective Field Theory, with dimension six operators built of Standard Model fields (SMEFT). We...
The inclusive transverse momentum spectrum (pt) of the Z boson is measured with high precision at the LHC and for this reason it is used a standard candle to tune Monte Carlo event generators. In turn, this implies that a change in theoretical description of the Z pt affects MC predictions used in other SM precision measurements, such as the W mass measurement. One of the uncertainties that...
This talk will describe searches for additional Higgs bosons at the ATLAS and CMS experiments, presenting the analysis methods and results. Emphasis will also be put on the QCD aspects that are relevant for the analyses.
The measurement of the associated production of a Higgs boson with a pair of top quarks is among the highest priorities of the current LHC physics program. In this talk latest results for threshold resummation of soft gluon corrections for the $pp \to t\bar{t}H$ process will be presented. The resummation is carried out at next-to-next-to-leading-logarithmic accuracy using the direct QCD Mellin...
This talk will describe searches for rare and beyond the Standard Model decays at the ATLAS and CMS experiments, presenting the analysis methods and results. Emphasis will also be put on the QCD aspects that are relevant for the analyses.
In this talk we consider the back-to-back region of the
energy-energy correlation in $e^+e^-$ collisions and present the matching of
the next-to-next-to-leading logarithmic (NNLL) approximation with the recently
computed fixed next-to-next-to-leading order (NNLO) corrections. We perform the
matching in the log R scheme. We compare our results to precise LEP and SLC data,
and find that the...
State-of-the-art theoretical predictions accurate to next-to-leading order QCD interfaced with Pythia8 and Herwig++ event generators are tested by comparing the unfolded ttbar differential data collected with the CMS detector at 8 and 13 TeV. These predictions are also compared with the underlying event activity distributions in ttbar events using CMS proton-proton data collected at a center...
This talk will describe the search for Higgs production in association with a tt-bar pair at the ATLAS and CMS experiments, presenting the analysis methods and results. Emphasis will also be put on the QCD aspects that are relevant for the analyses.
In this talk, the combination of the one-loop matrix-element generator Recola with the multipurpose Monte Carlo program Sherpa is presented. Since both programs are highly automated, the resulting Sherpa+Recola framework allows for the computation of—in principle—any Standard Model process at both NLO QCD and EW accuracy. The reliability of the Sherpa+Recola framework will be demonstrated via...
We present our next-to-next-to-leading order result performed in the CoLoRFulNNLO subtraction scheme for the three jet rate in electron-positron annihilation into three jets using the exclusive kt clustering algorithm. Results matched with next-to-double logarithmic resummation are also shown compared to OPAL data. In addition we present our predictions using the anti-kt algorithm at...
Theoretical uncertainties in the simulation of ttbb production represent one of the main obstacles that still hamper the observation of Higgs-boson production in association with top-quark pairs in the H->b?b. We present a next-to-leading order (NLO) simulation t?tb?b production with massive b-quarks matched to Pythia within the POWHEG method with the hope of reconciling tension between...
This talk will describe the combination of Higgs results from different decay channels at the ATLAS and CMS experiments, presenting the analysis methods and results. Emphasis will also be put on the QCD aspects that are relevant for the analyses.
Decreasing errors in experimental data obtained from colliders like the LHC
makes it necessary to invoke higher and higher orders in theory predictions.
A crucial part of the NNLO QCD predictions is the handling of the double real radiation phase-space and the cancellation of IR divergences with other contributions. I present a new phase-space parameterization for the sector-improved residue...
Several measurements of top quark properties are presented using data collected by the CMS experiment at different centre-of-mass-energies. The properties are mostly probed in production of the top quarks. The charge asymmetry is measured inclusively and differentially probing anomalous couplings to the gluons at production mode. These measurements are extended searching for asymmetries in...
I will present a general method to account for full colour dependence Yang-Mills amplitudes at loop level. The method fits most naturally into the framework of multi-loop integrand reduction and in a nutshell amounts to consistently retaining the colour structures of the unitarity cuts from which the integrand is gradually constructed. I will discuss connections to loop-level Kleiss-Kuijf...
We present results on measurements of characteristics of events with jets, from jet-charge over investigations of shapes to jet mass distributions. The measurements are compared to theoretical prediction including those matched to parton shower and hadronization.
A comprehensive set of measurements of top quark pair production in association with EWK bosons (W, Z or ɣ) is presented at different centre-of-mass energies. The results are compared to the theory predictions and re-interpreted as searches for new physics inducing deviations from the standard model predictions using an effective field theory approach. The status of the search for double-ttbar...
Vector boson scattering at the LHC has recently been discovered in the process $p p \to \mu^+\nu_\mu e^+\nu_e$, the so-called same-sign WW channel. This opens a new window for studying the nature of electroweak symmetry breaking and the role of the Higgs boson. Precision predictions for this process are thus of great importance. In this talk, the electroweak corrections at next-to-leading...
We present measurements of multi-differential Jet cross sections over a wide range in transverse momenta from inclusive jets to multi-jet final states. We present studies on the impact these measurements have on the determination of the strong coupling alphas as well as on parton density functions. We also show angular correlations in multi-jet events at highest center-of-mass energies and...
Searches for new resonances that decay either to pairs of top quarks or a top and a b-quark will be presented. The searches are performed with the ATLAS experiment at the LHC using proton-proton collision data collected in 2015 and 2016 with a centre-of-mass energy of 13 TeV. The invariant mass spectrum of hypothetical resonances are examined for local excesses or deficits that are...
Measurements of the cross sections of the production of pairs of 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. The ATLAS collaboration has performed detailed measurements of integrated and differential cross sections of the production of heavy...
We estimate the top-quark mass extraction uncertainty due to Monte Carlo modeling of top-pair production and its leptonic decay. Using three different NLO+PS generators based on the POWHEG method implementing an increasingly precise treatment of t?t production and decay, including hvq and bb4l, and two different PS implementations we obtain predictions for various kinematic distributions...
Abstract:
We have developed a new procedure to determine Parton Distribution Functions (PDFs) and their uncertainties, based on Markov Chain Monte Carlo methods. We will show in this talk how we can replace the standard $\chi^2$ minimization by procedures grounded on Statistical Methods, and on Bayesian inference in particular, thus offering additional insight into the rich field of PDFs. The...
Searching for heavy vector bosons is one of the challenging objectives of the LHC: I will discuss two scenarios which have not been investigated yet by the experimental collaborations. The first scenario consists in searching for Z' bosons, predicted by U(1) GUT-inspired models, by investigating its possible BSM decays, namely supersymmetric decays, leading to resonant final states with...
We estimate the top-quark mass extraction uncertainty due to Monte Carlo modeling of top-pair production and its leptonic decay. Using three different NLO+PS generators based on the POWHEG method implementing an increasingly precise treatment of $t\bar{t}$ production and decay, including $\texttt{hvq}$ and $\texttt{bb4l}$, and two different PS implementations we obtain predictions for various...
I present a new method to compute the cross section for WW production with a jet veto in QCD, fully exclusive in the decay products of the WW pair. The method is independent of the physics underlying the production of the WW pair, and allows for the interface with any NLO event generator.
