分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-11-10
分类: 物理学 >> 核物理学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: The experimental data of 100A MeV 12C + 12C elastic scattering are checked by using two-body kinematic calculation and 12C+p elastic scattering. It is shown that the measured data are true and reliable. In the paper, the transformation between the excited energy spectra of the 12C+12C system and the ground state energy spectra of the 12C+p system is introduced. The method of subtraction of the hydrogen background in the natural carbon target used in the experiment is elaborately described and the results are discussed. It is indicated that this method of subtraction of hydrogen background is reasonable and can be used in the data analysis. Based on the elastic scattering cross section of the previous experiment of 12C+p at 95.3A MeV, the hydrogen content entered into the reaction is analyzed. The final hydrogen content in the natural carbon target is (2.73 0.12)%.
分类: 物理学 >> 核物理学 提交时间: 2016-08-16
摘要: A new search signature for excited leptons is explored. Excited muons are sought in the channel pp→μμ∗→μμ jet jet, assuming both the production and decay occur via a contact interaction. The analysis is based on 20.3 fb−1 of pp collision data at a centre-of-mass energy of s√ = 8 TeV taken with the ATLAS detector at the Large Hadron Collider. No evidence of excited muons is found, and limits are set at the 95% confidence level on the cross section times branching ratio as a function of the excited-muon mass mμ∗. For mμ∗ between 1.3 TeV and 3.0 TeV, the upper limit on σB(μ∗→μqq¯) is between 0.6 and 1 fb. Limits on σB are converted to lower bounds on the compositeness scale Λ. In the limiting case Λ=mμ∗, excited muons with a mass below 2.8 TeV are excluded. With the same model assumptions, these limits at larger μ∗ masses improve upon previous limits from traditional searches based on the gauge-mediated decay μ∗→μγ.
分类: 物理学 >> 核物理学 提交时间: 2016-09-02
摘要: In this paper, we study the properties of the twist-3 distribution amplitude (DA) of the heavy pseudo-scalars such as ηc, Bc and ηb. New sum rules for the twist-3 DA moments ⟨ξnP⟩HP and ⟨ξnσ⟩HP up to sixth orders and up to dimension-six condensates are deduced under the framework of the background field theory. Based on the sum rules for the twist-3 DA moments, we construct a new model for the two twist-3 DAs of the heavy pseudo-scalar with the help of the Brodsky-Huang-Lepage prescription. Furthermore, we apply them to the Bc→ηc transition form factor (fBc→ηc+(q2)) within the light-cone sum rules approach, and the results are comparable with other approaches. It has been found that the twist-3 DAs ϕP3;ηc and ϕσ3;ηc are important for a reliable prediction of fBc→ηc+(q2). For example, at the maximum recoil region, we have fBc→ηc+(0)=0.674±0.066, in which those two twist-3 terms provide ∼33% and ∼22% contributions. Also we calculate the branching ratio of the semi-leptonic decay Bc→ηclν as Br(Bc→ηclν)=(9.31+2.27−2.01)×10−3.
分类: 物理学 >> 核物理学 提交时间: 2016-09-13
摘要: Searching for the signal of primordial gravitational waves in the B-modes (BB) power spectrum is one of the key scientific aims of the cosmic microwave background (CMB) polarization experiments. However, this could be easily contaminated by several foreground issues, such as the thermal dust emission. In this paper we study another mechanism, the cosmic birefringence, which can be introduced by a CPT-violating interaction between CMB photons and an external scalar field. Such kind of interaction could give rise to the rotation of the linear polarization state of CMB photons, and consequently induce the CMB BB power spectrum, which could mimic the signal of primordial gravitational waves at large scales. With the recent polarization data of BICEP2 and the joint analysis data of BICEP2/Keck Array and Planck, we perform a global fitting analysis on constraining the tensor-to-scalar ratio爎燽y considering the polarization rotation angle which can be separated into a background isotropic part and a small anisotropic part. Since the data of BICEP2 and Keck Array experiments have already been corrected by using the "self-calibration" method, here we mainly focus on the effects from the anisotropies of CMB polarization rotation angle. We find that including the anisotropies in the analysis could slightly weaken the constraints on爎, when using current CMB polarization measurements. We also simulate the mock CMB data with the BICEP3-like sensitivity. Very interestingly, we find that if the effects of the anisotropic polarization rotation angle can not be taken into account properly in the analysis, the constraints on爎爓ill be dramatically biased. This implies that we need to break the degeneracy between the anisotropies of the CMB polarization rotation angle and the CMB primordial tensor perturbations, in order to measure the signal of primordial gravitational waves accurately.
分类: 物理学 >> 核物理学 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: The characteristic gamma-ray spectrum of TNT in the soil induced by DT neutrons is measured by the PFTNA demining system. The GEANT4 toolkit is used to simulate the whole experimental procedure. The simulated spectra are compared with the experimental spectra, and they are mainly consistent. The share of the background sources such as neutrons and gamma is obtained and the contribution that the experimental apparatus to the background, such as shielding, detector sleeve and moderator, is analyzed. The effective gamma signal (from soil and TNT) is 29% of the full spectrum signal, and the background signal, more than 68%, this is mainly produced by shielding and the detector sleeve. By gradually optimizing the shielding and the cadmium sheet of the detector sleeve, the share of the effective gamma signal increases to 47%, and the background signal reduces to 18%.
分类: 物理学 >> 凝聚态:结构、力学和热性能 提交时间: 2017-03-26
摘要: The technique details for measuring radiation dose are expounded. The results of radiation levels of gamma and neutron are presented and the corresponding radiation shielding is discussed based on the simplified estimation. In addition, the radiation level of photon as background for the future experiment is measured by NaI(Tl) detector.
分类: 物理学 >> 核物理学 提交时间: 2023-07-02
摘要: Significant evidence for a gravitational-wave background was reported by several pulsar-timing-array collaborations. By assuming that this signal is interpreted by the scalar-induced gravitational waves, we study physical implications of the observed signal for the nature of primordial curvature perturbations and primordial black holes. In particular, we explore the effects of primordial non-Gaussianity on the inferences of model parameters, and obtain the parameter region allowed by the observed signal, i.e., the primordial scalar spectral amplitude $A_S\sim10^{-2}-1$, the primordial non-Gaussian parameter $-10\lesssim f_{\mathrm{NL}} \lesssim 10$, and the mass of primordial black holes $m_{\mathrm{pbh}}\sim10^{-3}-0.1M_{\odot}$. We find that the non-Gaussianity suppressing the abundance of primordial black holes is preferred by the observed signal. We show that the anisotropies of scalar-induced gravitational waves are a powerful probe for measurements of the non-Gaussian parameter $f_{\mathrm{NL}}$, and conduct a complete analysis of the angular power spectrum in the nano-Hertz band. We expect that the Square Kilometre Array project has potentials to measure such anisotropies.
分类: 物理学 >> 核物理学 提交时间: 2016-09-14
摘要: We present an evaluation of the background induced by�41Am-13C neutron calibration sources in the Daya Bay reactor neutrino experiment. As a significant background for electron-antineutrino detection at 0.26�.12 per detector per day on average, it has been estimated by a Monte Carlo simulation that was benchmarked by a special calibration data set. This dedicated data set also provided the energy spectrum of the background.
分类: 物理学 分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-12-27
摘要: Top squark (stop) can be produced via QCD interaction but also the electroweak interaction at the LHC. In this paper, we investigate the observability of the associated production of stop and chargino, pp→t~1χ~?1pp→t~1χ~1?pp \to \tilde{t}_1\tilde{\chi}^-_
分类: 物理学 分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-12-28
摘要: Motivated by recent studies of intersecting D-brane systems in critical string theory and phenomenological AdS/QCD models, we present a detailed analysis for the vector and scalar fluctuations in a non-critical holographic QCD model in the high temperatur
分类: 物理学 分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-12-28
摘要: We investigate the ability of single top quark production via qq'-> squark->tb and q \bar q'->slepton->t\bar b at the LHC and Tevatron to probe the strength of R-parity violating couplings in the minimal supersymmetric model. We found that given the exist
分类: 物理学 分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-12-28
摘要: We examine the possibility of observing exotic top quark decays via R-violating SUSY interactions at the Fermilab Tevatron and CERN LHC. We present cross-sections for tt?tt?t\bar t production followed by the subsequent decay of either ttt or t?t?\bar t vi
分类: 物理学 分类: 物理学 >> 基本粒子与场物理学 提交时间: 2016-12-28
摘要: We examine the possibility of observing exotic top quark decays via RRR-Parity violating SUSY interactions in e+e?e+e?e^+e^- collisions at \sqrt{s = 500 GeV\sqrt{s = 500 GeV\sqrt{s = 500 GeV. We present cross-sections for tt?tt?t\bar t production followed