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Efficient numerical evaluation of Feynman integrals

Zhao Li; Jian Wang; Qi-Shu Yan; Xiaoran ZhaoSubjects: Physics >> Nuclear Physics

Feynman loop integrals are a key ingredient for the calculation of higher order radiation effects, and are responsible for reliable and accurate theoretical prediction. We improve the efficiency of numerical integration in sector decomposition by implementing a quasi-Monte Carlo method associated with the CUDA/GPU technique. For demonstration we present the results of several Feynman integrals up to two loops in both Euclidean and physical kinematic regions in comparison with those obtained from FIESTA3. It is shown that both planar and non-planar two-loop master integrals in the physical kinematic region can be evaluated in less than half a minute with?O(10?3)accuracy, which makes the direct numerical approach viable for precise investigation of higher order effects in multi-loop processes, e.g. the next-to-leading order QCD effect in Higgs pair production via gluon fusion with a finite top quark mass. |

Preliminary study of light yield dependence on LAB liquid scintillator composition

YE Xing-Chen; YU Bo-Xiang; ZHOU Xiang; ZHAO Li; DING Ya-Yun; LIU Meng-Chao; DING Xue-Feng; ZHANG Xuan; JIE Quan-Lin; ZHOU Li; FANG Jian; CHEN Hai-Tao; HU Wei; NIU Shun-Li; YAN Jia-Qing; ZHAO Hang; HONG Dao-JinSubjects: Physics >> Nuclear Physics

Liquid scintillator (LS) will be adopted as the detector material in JUNO (Jiangmen Underground Neutrino Observatory). The energy resolution requirement of JUNO is 3%, which has never previously been reached. To achieve this energy resolution, the light yield of liquid scintillator is an important factor. PPO (the fluor) and bis-MSB (the wavelength shifter) are the two main materials dissolved in LAB. To study the influence of these two materials on the transmission of scintillation photons in LS, 25 and 12 cm-long quartz vessels were used in a light yield experiment. LS samples with different concentration of PPO and bis-MSB were tested. At these lengths, the light yield growth is not obvious when the concentration of PPO is higher than 4 g/L. The influence from bis-MSB becomes insignificant when its concentration is higher than 8 mg/L. This result could provide some useful suggestions for the JUNO LS. |

Factorization for substructures of boosted Higgs jets

Joshua Isaacson; Hsiang-nan Li; Zhao Li; C.-P. YuanSubjects: Physics >> Nuclear Physics

We present a perturbative QCD factorization formula for substructures of an energetic Higgs jet, taking the energy profile resulting from the?H→bb??decay as an example. The formula is written as a convolution of a hard Higgs decay kernel with two?b-quark jet functions and a soft function that links the colors of the two?b?quarks. We derive an analytical expression to approximate the energy profile within a boosted Higgs jet, which significantly differs from those of ordinary QCD jets. This formalism also extends to boosted?W?and?Z?bosons in their hadronic decay modes, allowing an easy and efficient discrimination of fat jets produced from different processes. |

Probe Higgs boson pair production via the 3?2j+$\notE$ mode

Qiang Li; Zhao Li; Qi-Shu Yan; Xiaoran ZhaoSubjects: Physics >> Nuclear Physics

We perform a detailed hadron-level study on the sensitivity of Higgs boson pair production via the?WW?WW?channel with the final state?3?2j?+ missing?ET?at the LHC with the collision energy?S√=14?TeV and a future 100 TeV collider. To avoid the huge background from?pp→ZW+jets?processes, we confine to consider the four lepton patterns:?e±e±μ??and?μ±μ±e?. We propose a partial reconstruction method to determine the most reliable combination. After that, we examine a few crucial observables which can discriminate efficiently signal and background events, especially we notice that the observable?mT2?is very efficient. For the LHC 14 TeV collisions, with an accumulated 3000 fb?1?dataset, we find that the sensitivity of this mode can reach up to 1.5?σ?for the Standard Model and the triple coupling of Higgs boson?λ3?in the simplest effective theory can be constrained into the range [-1, 8] at?95%?confidence level; at a 100 TeV collider with the integrated luminosity 3000 fb?1, the sensitivity can reach up to 13?σ?for the Standard Model and we find that all values of?λ3?in the effective theory can be covered up to 3σ?even without optimising signals. To precisely measure the triple coupling of Higgs boson?λ3=1?of the Standard Model at a 100 TeV collider, by using the invariant mass of three leptons which is robust to against the contamination of underlying events and pileup effects and by performing a?χ2?analysis, we find that it can be determined into a range [0.8, 1.5] at?95%?confidence level. |

Subjects: Physics >> Nuclear Physics

We explore the discovery potential of Higgs pair production at a 100 TeV collider via full leptonic mode. The same mode can be explored at the LHC when Higgs pair production is enhanced by new physics. We examine two types of fully leptonic final states and propose a partial reconstruction method. The reconstruction method can reconstruct some kinematic observables. It is found that the?mT2?variable determined by this reconstruction method and the reconstructed visible Higgs mass are important and crucial to discriminate the signal and background events. It is also noticed that a new variable, denoted as?Δm?which is defined as the mass difference of two possible combinations, is very useful as a discriminant. We also investigate the interplay between the direct measurements of?tt?h?couplings and other related couplings and trilinear Higgs coupling at hadron colliders and electron-positron colliders. |

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