The ee$\in$MC generator package is extended to include $e^{+}e^{-} \to Hadrons (nγ)$ events where the photons can be generated in either the initial-state or final-state production. In particular, the $e^{+}e^{-} \to π^{+}π^{-} (nγ)$, $e^{+}e^{-} \to Υ(4s) (mγ) \to B^{+}B^{-} (nγ)$ and $e^{+}e^{-} \to Υ(4s) (mγ) \to B^{0}\bar{B}^{-} (nγ)$ decay channels have been implemented in the generator. The B-mesons are not decayed in ee$\in$MC, but are left for other generators that specialized in B-mesons. Both the initial-state-radiation and final-state-radiation are simulated using the Yennie-Frautschi-Suura Exponentiation procedure \cite{Yennie:1961}, where several effective models are implemented to investigate the assumption of the radiative structure of the final-state vertex. The impact of these radiative models on the $e^{+}e^{-} \to Υ(4s) (mγ) \to B^{+}B^{-} (nγ)$ and $e^{+}e^{-} \to Υ(4s) (mγ) \to B^{0}\bar{B}^{-} (nγ)$ processes, excludes some models, particularly, in regards to the Coulomb potential. This has an important impact for meson and baryon systems near threshold.
In this paper a review on event shapes at hadron colliders, mainly focused on experimental results, is presented. Measurements performed at the Tevatron and at the LHC, for the soft and hard regimes of QCD, are reviewed. The potential applications of event shapes for unveiling the origin of collective-like phenomena in small collision systems as well as for testing pQCD predictions are discussed.
We calculate, for the first time, the NNLO QCD corrections to identified heavy hadron production at hadron colliders. The calculation is based on a flexible numeric framework which allows the calculation of any distribution of a single identified heavy hadron plus jets and non-QCD particles. As a first application we provide NNLO QCD predictions for several differential distributions of $B$ hadrons in $t\bar t$ events at the LHC. Among others, these predictions are needed for the precise determination of the top quark mass. The extension of our results to other processes, like open or associat…
We present the calculation of the next-to-leading order QCD corrections for top-quark pair production in association with an additional jet at hadron colliders, using the modified minimal subtraction scheme to renormalize the top-quark mass. The results are compared to measurements at the Large Hadron Collider run I. In particular, we determine the top-quark running mass from a fit of the theoretical results presented here to the LHC data.
Heavy flavor measurements in high multiplicity proton-proton and proton-nucleus collisions at collider energies enable unique insights into their production and hadronization mechanism because experimental and theoretical uncertainties cancel in ratios of their cross-sections relative to minimum bias events. We explore such event engineering using the Color Glass Condensate (CGC) effective field theory to compute short distance charmonium cross-sections. The CGC is combined with heavy-quark fragmentation functions to compute $D$-meson cross-sections; for the $J/ψ$, hadronization is described e…
Semi-inclusive deep-inelastic scattering (SIDIS) at the Electron-Ion Collider will allow for precise mapping of the 3D momentum and spin structure of nucleons and nuclei over a large kinematic region. In this contribution, we demonstrate methods utilizing the hadronic final state and scattered electron, as well as machine learning, to more reliably reconstruct the virtual photon four momentum and SIDIS kinematics across the inclusive DIS coverage at the EIC.
We study the system-size dependence of Knudsen number, a measure of degree of thermalization, for hadron resonance gas that follows the Lattice-QCD equation of state at zero chemical potential. A comparison between Knudsen numbers for the AuAu collisions at RHIC and the hadron gas of size similar to the size of high-multiplicity pp events at LHC, reassures the applicability of hydrodynamics in interpreting the features of particle production in high-multiplicity pp events.
To measure the $R$ value in an energy scan experiment with $\ee$ collisions, precise calculation of initial state radiation is required in event generators. We present an event generator for this consideration, which incorporates initial state radiation effects up to the second order accuracy, and the radiative correction factor is calculated using the totally hadronic Born cross section. The measured exclusive processes are generated according to their cross sections, while the unknown processes are generated using the LUND Area Law model, and its parameters are tuned with data collected at $…
Recent results related to Double-Parton Scattering (DPS) and Multi-Parton Interactions (MPI) from the LHC experiments (ALICE, ATLAS, CMS and LHCb) are reviewed and discussed together with a brief overview of relevant literature. The robust evidence collected for DPS in different channels at LHC energies is complemented by an increasing understanding of our description of MPI in high energy collisions and the corresponding modelling of the underlying event (UE) in hadronic interactions. Potential new results expected during Run 2 at the LHC are also anticipated. The relation and the interplay b…
Searching for a stop-pair sample from top counting experiments at hadron colliders
如果光停止对在强子对撞机中产生，并通过可能的衰变链停止->电荷伴子+ b，然后是电荷伴子->中性伴子+ f f '衰变，则当停止的质量接近时，可以密切模拟顶夸克事件。顶夸克的。由于产生率低得多，停止事件可以被埋在顶夸克事件样本之下。为了揭示停止事件，需要应用特定的选择切割。通过蒙特卡罗模拟和适当的运动学切割，我们发现这种停止事件可以从顶夸克样品中提取出来，并在即将进行的Tevatron和LHC升级实验中被顶夸克计数实验检测到。然而，由于Tevatron的运行1的小统计，停止信号在运行1处保持隐藏。
Phase space veto method for next-to-leading order event generators in hadronic collisions
利用一个否决权来组织次主导阶QCD的计算，该否决权使得虚发射图和实发射图之间相互抵消，这种方法被应用于强子碰撞。该方法采用相空间切片与切片参数动态确定的事件。它允许产生未加权的事件，并能与部分子簇射一致地合并。最终产品对于最终用户来说更直观，因为它是概率性的，并且可以很容易地与通用淋浴和强子化程序接口，以获得适合于实验分析的完整事件描述。作为一个例子，事件发生器的过程pp --> Z + X在NLO和接口一致的PYTHIA淋浴和强子化包。
We present an event generator for the simulation of central exclusive processes in hadron-hadron reactions. Among others, it implements the two-photon production of lepton pairs previously introduced in LPAIR. As a proof of principle, we show that the two approaches are numerically consistent. The $k_{\rm T}$-factorized description of this process is also handled, along with the two-photon production of a quark, or a $W^\pm$ gauge boson pair. This toolbox may be used as a common framework for the definition of many other processes following this approach. Additionally, photoproduction and othe…
In these proceedings, we summarise the results of the recent calculation of the NNLO QCD corrections for the production of a top-quark pair in association with a bottom-flavoured hadron. The results consist of differential distributions of observables involving the identified hadron.
Detailed and precise background predictions are the backbone of large parts of high-energy collider phenomenology. This requires to embed precision QCD calculations into detailed event generators, to produce comprehensive software simulations. Only continued progress in this direction will allow us to exploit the full potential of measurements at the Large Hadron Collider, or at a future Electron-Ion Collider. This work presents a method to combine third-order QCD calculations for hadronic scattering processes with Monte-Carlo event generators, thus enabling a new generation of precision predi…
In this paper heavy quark energy loss models are embedded in full event-by-event viscous hydrodynamic simulations to investigate the nuclear suppression factor and azimuthal anisotropy of D$^0$ mesons in PbPb collisions at 5.02 TeV in the $p_T$ range 8-40 GeV. In our model calculations, the $R_\text{AA}$ of D$^0$ mesons is consistent with experimental data from the CMS experiment. We present the first calculations of heavy flavor cumulants $v_2\{2\}$ and $v_3\{2\}$ (and also discuss $v_2\{4\}$), which is also consistent with experimental data. Event-shape engineering techniques are used to com…
Multiple Reflection Expansion (MRE) formalism has been applied to hadron resonance gas (HRG) model to study the finite-size effect on thermodynamics of small systems of hadron gas at the chemical freeze-out temperature in high-multiplicity events of proton-proton (pp) colisions at the LHC. Comparison with larger systems of heavy-ion (AA) collisions helps in undersanding the usefulness of the effect on small systems. Thermodynamic properties of these systems at the chemical freeze-out, with and without system-size effect, are contrasted with those for infinite hadronic phase of strongly interac…
A calculation of the transport coefficients of hot and dense hadronic matter based on the event generator URASiMA
利用事件发生器URASiMA（Ultra-Relativistic AA Collision Simulator based on Multiple Scattering Algorithm），在周期边界条件下计算了稠密热强子物质的物理量和输运系数。作为输运系数的最简单的例子，我们研究了稠密热强子物质的重子扩散常数的温度依赖性和化学势依赖性。
We have developed an event generator for direct-photon production in hadron collisions, including associated two-jet production in the framework of the GR@PPA event generator. The event generator consistently combines $γ$ + 2-jet production processes with the lowest-order $γ$ + jet and photon-radiation (fragmentation) processes from QCD 2-jet production using a subtraction method. The generated events can be fed to general-purpose event generators to facilitate the addition of hadronization and decay simulations. Using the obtained event information, we can simulate photon isolation and hadron…
The first implementation of fragmentation in a numerical code for the computation of cross sections at next-to-next-to-leading order in QCD has recently been completed. I will present some results of the first application of this new framework to the production of top-quark pairs at the LHC in association with a bottom-flavoured hadron. Additionally, I will present an extended version of this calculation, which includes the decay of the $B$-hadron to a $J/ψ$ meson or a muon.
Hadronization is a complex quantum process whereby quarks and gluons become hadrons. The widely-used models of hadronization in event generators are based on physically-inspired phenomenological models with many free parameters. We propose an alternative approach whereby neural networks are used instead. Deep generative models are highly flexible, differentiable, and compatible with Graphical Processing Unit (GPUs). We make the first step towards a data-driven machine learning-based hadronization model by replacing a compont of the hadronization model within the Herwig event generator (cluster…
Particle production and event topology are very strongly correlated in high-energy hadronic and nuclear collisions. Event topology is decided by the underlying particle production dynamics and medium effects. Transverse spherocity is an event shape observable, which has been used in pp and heavy-ion collisions to separate the events based on their geometrical shapes. It has the unique capability to distinguish between jetty and isotropic events. In this work, we have implemented transverse spherocity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV using A Multi-Phase Transport Model (AMP…
The high-multiplicity pp collisions at the Large Hadron Collider energies with various heavy-ion-like signatures have warranted a deeper understanding of the underlying physics and particle production mechanisms. It is a common practice to use experimental data on the hadronic transverse momentum ($p_T$) spectra to extract thermodynamical properties of the system formed in heavy ion and high multiplicity pp collisions. The non-availability of event topology dependent experimental data for pp collisions at $\sqrt{s}$ = 13 TeV on the spectra of non-strange and strange hadrons constrains us to us…
