Hadronic calorimetry and jet/τ/E T miss performance studies in ATLAS

The European Physical Journal C - Jets, τ jets, and missing transverse energy are important components of the physics expected at the LHC. The accurate measurement of the direction and energy...     

Electromagnetic calorimetry and e/γ performance in CMS

The European Physical Journal C - The electromagnetic calorimeter of the CMS experiment at LHC will consist of about 76000 Lead Tungstate crystals. Its main purpose is the very precise energy...     

Direct photon and photon-jet measurement capability of the ATLAS experiment at the LHC

Direct photon and photon-jet correlations are perfect tools for tomographic studies of the dense medium produced in heavy ion collisions at LHC energies. Due to their weak interactions with the medium, direct photons serve as standard candles for hard-scattering processes, providing a clean calibration of the momentum of the associated jets. The ATLAS detector has powerful opportunities to carry out these measurements. The combination of fine granularity, longitudinal segmentation and large acceptance is unique for the LHC detectors. We show how it will provide optimal capability to distinguish direct photon clusters from neutral meson clusters based on their shower profile over a wide acceptance in η−?$\eta -?$ up to 200 GeV in pT$p_T$. We show that combined with a photon isolation cut ATLAS would be able to measure a relatively background-free direct photon yield from 50–200 GeV along with the corresponding gamma-jet correlations in one nominal LHC Pb+Pb year. These high pT$p_T$ photons provide clean and statistically significant measurements of gamma-jet correlations and the fragmentation function for photon-tagged jets.     

GaN/AlGaN双带红外探测及光子频率上转换研究

研究了GaN/AlGaN异质结构中的双带（中、远）红外探测及光子频率上转换特性.通过光致发光光谱确认GaN/AlGaN探测器结构中AlGaN本征层的Al组分,讨论了不同Al组分GaN/AlGaN异质结的导带带阶界面功函数差.在拟合单周期GaN/AlGaN探测器中红外和远红外波段响应谱的基础上,研究多周期GaN/AlGaN探测器与GaN/AlGaN发光二极管集成结构的中红外和远红外光子频率上转换效率与GaN发射层厚度、AlGaN本征层厚度、紫光光子出射效率、内量子效率、空间频率和发射层掺杂浓度间的关系,优化 关键词： 双带红外探测 光子频率上转换 响应谱 GaN/AlGaN     

Joint multipartite photon statistics by on/off detection

We demonstrate a method to reconstruct the joint photon statistics of two or more modes of radiation by using on/off photodetection performed at different quantum efficiencies. The two-mode case is discussed in detail, and experimental results are presented for the bipartite states obtained after a beam splitter fed by a single photon state or a thermal state.     

Resonances in electron scattering and photon absorption

A short survey is given of the development of ideas about resonances in atomic scattering processes and their connection with the theory of resonant states in nuclei, impurity resonances in solids, ion-atom scattering and recombination in plasmas. A detailed discussion of the experimental situation for atomic resonances is then given, followed by a review of the theory of resonance reactions as applied to them. Special attention is given to effective range and quantum defect methods, and to Fano's configuration interaction theory. Theoretical results for line positions, shapes and widths are compared with experimental data and the need for more angular distribution data is emphasized.     

Influence of an intense pulsed electromagnetic field on nonresonant scattering of a photon by an electron for the nonrelativistic energy

The theory of nonresonant scattering of a photon by an electron in the field of an intense pulsed light wave is developed. The approximation when a pulse width is considerably greater than the characteristic time of wave oscillation is considered. The nonresonant kinematic region is determined. The general relativistic expression for the nonresonant cross-section is derived for the range of the external field intensities if η ₀ ? 1, η₀ ² ? 1 (see Eq. (12)) is valid. The obtained differential cross-section of the process has form of a sum over partial differential cross-sections. Each of them corresponds to the process with emission (absorption) of a certain number of wave photons. It is shown, that for nonrelativistic energy the cross-section summed over all possible partial processes differs considerably from the cross-section of Compton scattering if the external field is absent and may exceed the latter over than 200%.     

Evolution of ideas in photon detection

In this paper we consider an evolution of ideas in vacuum photodetector developments. Diverse approaches in developments of vacuum photodetectors (classical photomultipliers and hybrid phototubes) for the last half of century are covered. A particular emphasis is made on large area vacuum photodetectors developments. Some other issues concerning WLS and light guide techniques for increasing photodetectors sensitivity are highlighted as well.     

单分子光子源光子统计的非平衡探测

研究了在Hanbury Brown Twiss探测方式下，非平衡探测系统对光子统计测量的影响。通过记录2个单光子计数器响应的单分子光子源输出的每一个事件，分析具有泊松统计背景的实际单分子光子源的光子统计特性，讨论并给出了非平衡探测系统的单分子光子源Mandel参数。研究表明：非理想的50／50分束器、非理想的线性传输效率和非理想的探测器都会使单分子光子源Mandel参数的实际测量结果小于平衡系统的Mandel参数，最后给出了单分子光子源Mandel参数的非理想探测的校正表达式。     

电磁场中光子-轴子的转化微分截面

运用费曼微扰方法分别计算了在磁偶极场、电偶极场和均匀静电场及静磁场中光子转化成轴子的非极化微分截面.在电偶极场中,沿光子传播方向及其反方向上的非极化微分截面为零;而在磁偶极场中,在上述方向上通常则具有非零的微分截面,但当光子传播方向平行于磁场偶极距矢量时,该微分截面为零.在均匀的静磁场和均匀静电场中,只有在光子传播方向及其反方向上具有非零的微分截面,但后者小于前者.在轴子质量趋于零的极限条件下,上述过程和光子转化为引力子的过程表现出某些非常类似的性质. 关键词： 轴子 光子 微分截面     

Dominance of electromagnetic effects in high energy hadron and photon induced reaction

It is argued that at high enough energy the electromagnetic interaction will dominate over the strong interactions in all reactions that can proceed via photon exchange. Important consequences of this possibility are discussed. Among them are the possibility of measuring meson and photon structure functions already in the energy range of the NAL machine, the possibility of a breakdown of isospin invariance at high energy and its possible verification at the ISR CERN machine, and the inequality between particle and antiparticle cross sections at high energy.     

Scattering of neutrinos (antineutrinos) on an electron with emission of a photon in the renormalizable theory of the weak and electromagnetic interaction

The differential and total cross sections are obtained for the processes \(v(\bar v) + e \to v(\bar v) + e + \gamma \) in the renormalizable theory of the weak and electromagnetic interaction.     

The design and performance of the ATLAS Inner Detector trigger for Run 2

The design and performance of the ATLAS Inner Detector (ID) trigger algorithms running online on the High Level Trigger (HLT) computing cluster with the early LHC Run 2 data are discussed. During the LHC shutdown from 2013 to 2015, the HLT farm was redesigned to run in a single HLT stage, rather than in two stages (Level 2 and Event Filter) as was used in Run 1. This allowed for a redesign of the HLT ID tracking algorithm, which aims to satisfy the challenging demands of the higher collision energy of the LHC in Run 2 and is essential for tracking of different charged particles in the ATLAS detector. The detailed performance of the tracking algorithms with the initial Run 2 data is discussed for electrons, muons and other charged particles. Comparison with the Run 1 strategy is made and demonstrates the superior performance of the strategy adopted for Run 2.     

Splitting of a photon into three by an electron

The process of splitting a photon into three by an electron is considered in this paper. A calculation is carried out in the lower order of perturbation theory, based on the exact solution of the problem concerning the motion of an electron in the field of a quantized plane electromagnetic wave. The photons of the wave are taken to be linearly polarized in both the initial and final states and the electron is unpolarized. The -component of the differential and total emission probability is calculated. Special cases of the differential and total probability for the polarized photon emitted are presented.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 12–15, February, 1979.In conclusion, the authors thank Professor V. G. Bagrov for attention to work.     

Splitting of a polarized photon by an unpolarized electron

The process of splitting of a polarized photon of a plane electromagnetic wave into two polarized photons by an unpolarized electron is examined. The degree of circular and linear polarization of the photon radiated is studied in detail.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 133–138, August, 1978.The authors are grateful to Professor V. G. Bagrov for discussing the research.