分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We study the anisotropies of gravitational waves induced by weak hypermagnetic fields which are randomly distributed and oriented during the electroweak phase transition in the early universe. The theory setup of this study is the standard model plus a real singlet scalar field, which can produce the needed strongly first order electroweak phase transition. Then we investigate how the hypermagnetic fields can convert to magnetic fields and we compute the departure of energy difference between the symmetric phase and the broken phase when the magnetic fields are turned on. It is found that the presence of the hypermagnetic fields can increase the Euclidean action, thus can decrease nucleation temperature, which can lead to a supercool plasma. We point out that the hypermagnetic field can enhance the gravitational wave production from a first order electroweak phase transition and the inhomogeneity of primordial hypermagnetic field can lead to anisotropies of gravitational waves. By examining three well-motivated distribution of hypermagnetic fields, we calculate the corresponding angular power spectra of stochastic gravitational wave background and find they can be significantly larger than the contributions of the Sachs-Wolfe effects and integrated Sachs-Wolfe effects. Our results show that the anisotropies of gravitational wave could provide a novel probe to the primordial hypermagnetic field in the electroweak phase transition epoch.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We study the anisotropies of gravitational waves induced by weak hypermagnetic fields which are randomly distributed and oriented during the electroweak phase transition in the early universe. The theory setup of this study is the standard model plus a real singlet scalar field, which can produce the needed strongly first order electroweak phase transition. Then we investigate how the hypermagnetic fields can convert to magnetic fields and we compute the departure of energy difference between the symmetric phase and the broken phase when the magnetic fields are turned on. It is found that the presence of the hypermagnetic fields can increase the Euclidean action, thus can decrease nucleation temperature, which can lead to a supercool plasma. We point out that the hypermagnetic field can enhance the gravitational wave production from a first order electroweak phase transition and the inhomogeneity of primordial hypermagnetic field can lead to anisotropies of gravitational waves. By examining three well-motivated distribution of hypermagnetic fields, we calculate the corresponding angular power spectra of stochastic gravitational wave background and find they can be significantly larger than the contributions of the Sachs-Wolfe effects and integrated Sachs-Wolfe effects. Our results show that the anisotropies of gravitational wave could provide a novel probe to the primordial hypermagnetic field in the electroweak phase transition epoch.
分类： 物理学 >> 核物理学 提交时间： 2016-09-14
摘要： 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.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： We perform a detailed hadron-level study on the sensitivity of Higgs boson pair production via the WW∗WW∗channel with the final state 3ℓ2j + 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.
分类： 物理学 >> 核物理学 提交时间： 2016-09-02
摘要： 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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