Initial-state and final-state interactions, which are conventionally neglected in the parton model, have a profound effect in QCD hard-scattering reactions. These effects, which arise from gluon exchange between the active and spectator quarks, cause leading-twist single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, and the breakdown of the Lam-Tung relation in Drell-Yan reactions. Diffractive deep inelastic scattering also leads to nuclear shadowing and non-universal antishadowing of nuclear structure functions through multiple scattering reactions in the nuclear target. Factorization-breaking effects are particularly important for hard hadron interactions since both initial-state and final-state interactions appear. Related factorization breaking effects can also appear in exclusive electroproduction reactions and in deeply virtual Compton scattering. None of the effects of initial-state and final-state interactions are incorporated in the light-front wavefunctions of the target hadron computed in isolation.
Within the framework of local analytic sector subtraction, we present the subtraction of next-to-leading-order QCD singularities for processes featuring massless coloured particles in the initial as well as in the final state. The features of the method are explained in detail, including the introduction of an optimisation procedure aiming at improving numerical stability at the cost of no extra analytic complexity. A numerical validation is provided for a variety of processes relevant to lepton as well as hadron colliders. This work constitutes a relevant step in view of the application of ou…
In this paper, I qualitatively discuss the matter formed in the fragmentation region of nuclear collisions at the highest energies. I argue that although the initial temperature and baryon number density can become very large, the ratio of initial baryon chemical potential to initial temperature is approximately independent of energy, when measured at a fixed rapidity measured from the end of the fragmentation region. This quantity is argued to be roughly invariant under expansion, and therefore the value measured at decoupling should be approximately the same as the initial value and largely …
Up to the next-leading order (NLO) of quantum chromodynamics (QCD), the process $e^+e^-\to J/ψ+X$ with the center-of-mass (CM) energy range from 3.7 to 10.6 GeV is calculated. At 10.6 GeV, the results is consistent with the experiment results at the Belle. However, the predictions are much smaller than the measurement at BESIII at low CM energy range from 3.7 to 4.6 GeV. This indicates that the convergence of QCD perturbative expansion becomes worse as the CM energy becomes lower and closer to the inclusive $J/ψ$ production threshold. For a further study of the QCD mechanism on $J/ψ$ productio…
The aim of this thesis is to calculate field-theoretically as rigorously as possible the initial state of partonic matter produced in ultrarelativistic heavy-ion collisions at CERN-LHC and BNL-RHIC colliders. The computed minijet initial conditions are then used in the initialization of the relativistic hydrodynamical modeling of these collisions. In the theoretical introduction part the computation of parton production cross section at next-to-leading order (NLO) perturbative QCD (pQCD) is discussed. Furthermore, the full analytical calculation for the squared quark-quark scattering matrix el…
We present a parton-shower matched NNLO QCD calculation for hadronic final state production in Deep Inelastic Scattering. The computation is based on the UNLOPS method and is implemented in the publicly available event generation framework SHERPA. Results are compared to measurements performed by the H1 collaboration.
We present a local subtraction scheme for computing next-to-next-to-leading order QCD corrections to the production of a massive quark-antiquark pair from a colourless initial state. The subtraction terms are built following the CoLoRFulNNLO method and refined in such a way that their integration gives rise to compact, fully analytic expressions. All ingredients necessary for a numerical implementation of our subtraction scheme are provided in detail. As an example, we calculate the fully differential decay rate of the Standard Model Higgs boson to massive bottom quarks at next-to-next-to-lead…
We review the basic concepts of all-order calculations in Quantum Chromodynamics (QCD) and their application to collider phenomenology. We start by discussing the factorization properties of QCD amplitudes and cross-sections in the soft and collinear limits and their resulting all-order exponentiation. We then discuss several applications of this formalism to observables which are of great interest at particle colliders. In this context, we describe the all-order resummation of event-shape distributions, as well as observables that probe the internal structure of hadronic jets.
We present compact analytic formulas that describe the decay of colorless particles to both $q \bar q$ and $gg$ final states through next-to-next-to-leading order in perturbative QCD in the context of the nested soft-collinear subtraction scheme. In addition to their relevance for the description of decays like $V \to q \bar q'$, $V= Z,W$, $H \to b \bar b$ and $H \to gg$, these results provide an important building block for calculating NNLO QCD corrections to arbitrary processes at colliders within the nested soft-collinear subtraction scheme.
The production of two-jet final states in deep inelastic scattering is an important QCD precision observable. We compute it for the first time to next-to-next-to-leading order (NNLO) in perturbative QCD. Our calculation is fully differential in the lepton and jet variables and allows one to impose cuts on the jets both in the laboratory and the Breit frame. We observe that the NNLO corrections are moderate in size, except at kinematical edges, and that their inclusion leads to a substantial reduction of the scale variation uncertainty on the predictions. Our results will enable the inclusion o…
We analyzed the process of $B_s\rightarrow ρρ$ decay in QCD factorization (QCDF) and final state interaction (FSI) effects. In QCDF for this decay we have only the annihilation graph and we expected small Branching ratio. Then we considered FSI effect as a sizable correction where the intermediate states are $π^0π^0$, $π^+π^-$, $K^0\bar{K^0}$ and $K^+K^-$ mesons. To consider the amplitudes of these intermediate states, QCDF approach was used. The experimental branching ratio of $B_s\rightarrow ρρ$ is less than $3.20\times 10^{-4}$ and our result is $1.08 \times 10^{-9}$ and $3.29 \times10^{-4}…
The abundant amount of data to be collected by the ATLAS and CMS collaborations in future runs of the Large Hadron Collider at CERN opens up a new era of precision physics. Some of the most prominent precision observables are related to processes with one or more jets in the final state. In order to fully exploit the potential of the LHC and the HL-LHC, it is imperative to make theoretical predictions at the level of accuracy that matches or even exceeds that of the upcoming measurements. In this talk we present a review of the status of theoretical predictions including NNLO QCD corrections f…
We present the full $\mathcal{O}(α_s)$ supersymmetric QCD corrections for stop-anti-stop annihilation into electroweak final states within the Minimal Supersymmetric Standard Model (MSSM). We also incorporate Coulomb corrections due to gluon exchange between the incoming stops. Numerical results for the annihilation cross sections and the predicted neutralino relic density are presented. We show that the impact of the radiative corrections on the cosmologically preferred region of the parameter space can become larger than the current experimental uncertainty, shifting the relic bands within t…
We initialize the Quantum Chromodynamic conserved charges of baryon number, strangeness, and electric charge arising from gluon splitting into quark-antiquark pairs for the initial conditions of relativistic heavy-ion collisions. A new Monte Carlo procedure that can sample from a generic energy density profile is presented, called Initial Conserved Charges in Nuclear Geometry (ICCING), based on quark and gluon multiplicities derived within the color glass condensate (CGC) effective theory. We find that while baryon number and electric charge have nearly identical geometries to the energy densi…
Our community has to apply {\em non}-perturbative QCD on different levels of flavor dynamics in strange, charm \& beauty hadrons and even for top quarks. We need {\em consistent} parameterization of the CKM matrix and describe weak decays of beauty hadrons with {\em many-body} final states. It is crucial to use the {\em Wilsonian} OPE as much as possible and discuss "duality" in the worlds of quarks and hadrons. The pole mass of heavy quarks is {\em not} well-defined on the {\em non}-perturbative level -- i.e., it is {\em not} Borel summable in total QCD. We need a novel team to combine the st…
In this contribution we report on the latest theoretical predictions for $t\bar{t}b\bar{b}$. These results are obtained for the fully decayed final state $pp \rightarrow e^+ ν_e μ^- ν_μ b \bar{b} b \bar{b}$ at next-to-leading order accuracy in QCD. We present predictions with full off-shell effects and in the Narrow Width Approximation. Specifically, we report on the size of the NLO QCD corrections and the size of the full off-shell effects. Finally, we study the nature of the $b$-jets present in the final state.
A precise theoretical description of W- and Z-boson production in the resonance region is essential for the correct interpretation of high-precision measurements of the W-boson mass and the effective weak mixing angle. Currently, the largest unknown fixed-order contribution is given by the mixed QCD-electroweak corrections of $\mathcal{O}(α_sα)$. We argue, using the framework of the pole expansion for the NNLO QCD-electroweak corrections established in a previous paper, that the numerically dominant corrections arise from the combination of large QCD corrections to the production with the larg…
The title of my talk pointed out central statements: the impact of non-perturbative QCD on {\bf CP} asymmetries in many-body FS in charm \& beauty hadrons. For practical reasons one measures first {\bf CP} violation in two-body final states of heavy flavor hadrons. However, those are small parts of charm hadrons and tiny ones for beauty hadrons; therefore one has to probe {\bf CP} asymmetries in three- \& four-body final states. Thus the transitions to the many-body FS basically give information about the underlying dynamics. The impact of non-perturbative QCD on {\bf CP} asymmetries in many-b…
