The calibration of an LHCb electromagnetic calorimeter by recovering the invariant mass of neutral pions

The precise calibration of an electromagnetic calorimeter is extremely important for flavor tagging and for the study of B-mesons decays and therefore is of great importance for implementing the physics program of the LHCb experiment. The purpose of the calibration process is to achieve a 2% accuracy when measuring the energies of electrons and photons. At the last step of a multi-stage procedure, the method of restoring the invariant mass of a neutral pion in its decay into two photons is used.     

Study of response nonuniformity for the LHCb calorimeter module and the prototype of the CBM calorimeter module

A spatial nonuniformity of the response to high-energy muons is studied in the modules of the LHCb electromagnetic calorimeter and the prototype of the calorimeter module with lead plates and scintillator tiles 0.5 mm thick. The nonuniformity of the response of the inner LHCb modules to 50-GeV electrons is also measured. Software is developed for a thorough simulation of light collection in scintillator plates of a shashlik calorimeter. A model is elaborated to describe light transmission from the initial scintillation to the wavelength-shifting fiber with a subsequent reradiation and propagation of light over the fiber to the photodetector. The results of the simulation are in good agreement with data.     

高能激光能量计溯源问题研究

由于高能激光能量计标定过程中没有标准的能量测量装置和标准的激光源,无法采用常规方法对其进行标校。提出了一种利用现有小能量计从低到高逐级多次传递不确定度的方法,以及一种利用能量等效原理对激光能量计进行标校的方法。不确定度传递法方法简单,但环节较多导致不确定度较大。等效标定法包括电标法和光标法,电标法对设计要求较高,但求解过程相对简单。光标法工程实现难度要低得多,但必须事先对灯组余热及热损失进行测算。等效法的三个条件与误差大小关系紧密,在结构设计中必须严格考虑,它是提高测量准确性的根本,其次要尽量减少不确定度传递的中间环节,最后需要对误差项进行科学分析和测定,在此基础上对这些项进行相应的修正和补偿。     

An electromagnetic calorimeter for the silicon detector concept

A silicon-tungsten calorimeter for silicon detector (SiD) at the International Linear Collider is under development. Recent progress is summarized.      

Method for reconstructing the gamma-ray arrival direction in the converter + calorimeter system

When designing devices of modern gamma astronomy, one of the most important problems is achieving the maximum possible angular resolution. This study is devoted to the method for reconstructing the arrival direction of primary gamma-rays with energies E _γ > 10 GeV in the GAMMA-400 satellite experiment. By the example of the GAMMA-400 gamma telescope, the possibility of improving the angular resolution of gamma telescopes incorporating a “converter + calorimeter” system is shown. The dependence of the angular resolution on the step of silicon strips used to determine the coordinates of incident particles in the converter and calorimeter and the distance between the converter and calorimeter is analyzed.     

Calibration of drift chambers and calorimeter of BigBite spectrometer

Method of calibration of the calorimeter and drift chambers of the BigBite spectrometer having been used in the experiment on measuring the neutron electric form-factor is presented. The BigBite spectrometer provided measurement of the direction and momentum of scattered electron by means of measuring its trajectory after passing through the magnetic field. Calibration of the set of detectors of the BigBite spectrometer was important for success of the experiment.     

Angular reconstruction of a lead scintillating-fiber sandwiched electromagnetic calorimeter

The Neighbor Cell Deposited Energy Ratio （NCDER） is a new method that is proposed to reconstruct incidence position in a single layer for a 3-dimensional imaging electromagnetic calorimeter （ECAL）. This method was applied to reconstruct the ECAL test beam data for the Alpha Magnetic Spectrometer-02 （AMS-02）. The results show that this method can achieve an angular resolution of 7.36±0.08°/√E＋0.28±0.02° in the determination of the photon＇s direction, which is much more precise than that obtained with the commonly-adopted Center of Gravity （COG） method （8.4±0.1°/E＋0.8±0.3°）. Furthermore, since it uses only the properties of electromagnetic showers, this new method could also be used for other type of fine grain sampling calorimeters.     

Angular reconstruction of a lead scintillating-fiber sandwiched electromagnetic calorimeter

The Neighbor Cell Deposited Energy Ratio(NCDER) is a new method that is proposed to reconstruct incidence position in a single layer for a 3-dimensional imaging electromagnetic calorimeter(ECAL).This method was applied to reconstruct the ECAL test beam data for the Alpha Magnetic Spectrometer-02(AMS-02).The results show that this method can achieve an angular resolution of 7.36±0.08°/E~(1/2)(?)0.28±0.02o in the determination of the photon's direction,which is much more precise than that obtained with the commonly-adopted Center of Gravity(COG) method(8.4±0.1°/E~(1/2)(?)0.8±0.3o).Furthermore,since it uses only the properties of electromagnetic showers,this new method could also be used for other type of fine grain sampling calorimeters.     

Theory of the conformally invariant mass

By interpreting the conformal transformations as space-time-dependent change of units and introducing the concept of the conformally invariant mass and charge, we develop new conformally invariant Maxwell equations with source terms and equations of motion for massive particles. Although the usual equations of motion with mass terms break the conformal symmetry, it is shown that the Minkowski space is not the most general framework to describe physical processes and there exists a wider consistent dynamics in which conformal invariance is exact. New results also include the general transformation laws of the electromagnetic fields, of currents and force densities. The theory leads naturally to an affine connection and to the 21-parameter inhomogeneous conformal group, ISO(4, 2).     

高功率激光能量测试的卡计系数标定技术

提出在卡计系数标定中采用直线拟合方法,综合考察相关系数、斜率、截距、斜率和截距标准偏差等参数,以斜率相对标准偏差作为采用何种直线拟合的主要判断依据;若过零直线拟合的斜率相对标准偏差小于不过零的斜率相对标准偏差,认为截距为随机误差,卡计系数标定按照非等精度的加权平均法求解;反之,应按照不过零直线拟合,截距为测试的系统误差,根据定位回归误差大小判断并剔除粗大误差;这样可以合理给出激光能量测试的卡计标定系数。     

高功率激光能量测试的卡计系数标定技术

提出在卡计系数标定中采用直线拟合方法,综合考察相关系数、斜率、截距、斜率和截距标准偏差等参数,以斜率相对标准偏差作为采用何种直线拟合的主要判断依据;若过零直线拟合的斜率相对标准偏差小于不过零的斜率相对标准偏差,认为截距为随机误差,卡计系数标定按照非等精度的加权平均法求解;反之,应按照不过零直线拟合,截距为测试的系统误差,根据定位回归误差大小判断并剔除粗大误差;这样可以合理给出激光能量测试的卡计标定系数。     

Status of the LHCb experiment

The European Physical Journal C - LHCb is a dedicated experiment to study CP violation and other rare processes in the B meson system at LHC. It is designed to exploit the large sample of Bd and Bs...     

Correction of PMT position effect for a lead-scintillating fiber electromagnetic calorimeter

The position effect of the photoelectron multiplier tube (PMT) of the electromagnetic calorimeter (ECAL) of Alpha Magnetic Spectrometer-02 (AMS-02) has been studied with beam-test data. The reconstructed deposited energy in a layer versus incidence position in the cell can be described by Gaussian distribution, maximum and minimum value can be obtained when the particle passes across the center and the edge of a cell respectively. The distribution can be used to correct the effect of incidence position on energy reconstruction. Much better energy resolution was acquired be got with the correction, for 100 GeV electrons, energy resolution improved from 3% to 2%.     

Method for identifying low-energy antiprotons using the electromagnetic position-sensitive calorimeter of the PAMELA spectrometer

The PAMELA experiment on the study of cosmic rays in a wide energy range was performed onboard the Resurs-DK1 spacecraft from June 2006 to February 2016. The data on antiproton fluxes in the near-Earth space play an important role for this field of physics. Their detection by the PAMELA spectrometer is possible using two independent detectors: the track system in a magnetic field and the position-sensitive calorimeter (in the low-energy region, <1 GeV). The presented technique for identifying antiprotons is based on the analysis of tracks of the antiproton and secondary charged mesons produced during its annihilation in the calorimeter. This technique allows identification of antiprotons with energies of 200–800 MeV, independently confirming the data of a magnetic analysis and increasing the statistics due to the larger geometrical factor of the calorimeter in comparison with a track system.     

Physics reach of the LHCb experiment

The European Physical Journal C - The physics prospects of the LHCb experiment are presented here for precision CP violation measurements and rare decays.     

Strange quark mass from the invariant mass distribution of Cabibbo-suppressed tau decays

Quark mass corrections to the hadronic width play a significant role only for the strange quark. The complete determination of decays into strange hadronic final states performed by ALEPH allows the extraction of the strange spectral function. New results on strange decay modes from other experiments are also incorporated into the present analysis. Using as input moments of the spectral function the analysis leading to the determination of is conducted using reasonable theoretical constraints on the nonperturbative components. Careful attention is paid to the treatment of the perturbative expansions of the moments which exhibit convergence problems. The result obtained, , is stable over the scale from down to about 2 GeV. Its evolution yields and . Received: 22 May 2001 / Published online: 5 November 2001     

On the invariant mass conjecture in general relativity

An asymptotic symmetries theorem is proved under certain hypotheses on the behaviour of the metric at spatial infinity. This implies that the Einstein-von Freud-ADM mass can be invariantly assigned to an asymptotically flat four dimensional end of an asymptotically empty solution of Einstein equations if the metric is a no-radiation metric or if the end is defined in terms of a collection of boost-type domains.On leave of absence from the Institute of Mathematics, Polish Academy of Sciences, Warsaw, PolandSupported in part by the Polish Ministry of Science Research Project CPBP 01.2 and by the NSF Grant PHY8503072 to Yale University