ALICE TRD Collaboration
We study the electron/pion identification performance of the ALICE Transition Radiation Detector (TRD) prototypes using a neural network (NN) algorithm. Measurements were carried out for particle momenta from 2 to 6 GeV/c. An improvement in pion rejection by about a factor of 3 is obtained with NN compared to standard likelihood methods.
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We present measurements of the transition radiation (TR) spectrum produced in an irregular radiator at different electron momenta. The data are compared to simulations of TR from a regular radiator.
We present the electron/pion identification performance measured with prototypes for ALICE TRD. Measured spectra of energy deposit of pions and electrons as well as their average values are presented and compared to calculations. Various radiators are investigated over the momentum range of 1 to 6 GeV/c. The time signature of TR is exploited in a bidimensional likelihood mothod.
The Transition Radiation Detector (TRD) was designed and built to enhance the capabilities of the ALICE detector at the Large Hadron Collider (LHC). While aimed at providing electron identification and triggering, the TRD also contributes significantly to the track reconstruction and calibration in the central barrel of ALICE. In this paper the design, construction, operation, and performance of this detector are discussed. A pion rejection factor of up to 410 is achieved at a momentum of 1 GeV/$c$ in p-Pb collisions and the resolution at high transverse momentum improves by about 40% when inc…
We present the energy loss measurements with the ALICE TRD in the $βγ$ range 1--10$^{4}$, where $β=v/c$ and $γ=1/\sqrt{1-β^2}$. The measurements are conducted in three different scenarios: 1) with pions and electrons from testbeams; 2) with protons, pions and electrons in proton-proton collisions at center-of-mass energy 7 TeV; 3) with muons detected in ALICE cosmic runs. In the testbeam and cosmic ray measurements, ionization energy loss (dE/dx) signal as well as ionization energy loss plus transition radiation (dE/dx+TR) signal are measured. With cosmic muons the onset of TR is observed. Sig…
The Transition Radiation Detector (TRD) provides particle identification in the ALICE central barrel. In particular, it allows electron identification via the measurement of transition radiation for $\rm p >$ 1 GeV/$c$, where pions can no longer be rejected sufficiently via specific energy loss in the ALICE Time Projection Chamber. The ALICE TRD is uniquely designed to record the time evolution of the signal, which allows even better electron/pion separation. In addition, the electron identification capability of the TRD can be used on-line to trigger at level 1. The particle identification an…
We discuss how a level-1 trigger, about 8 us after a hadron-hadron collision, can be derived from the Transition Radiation Detector (TRD) in A Large Ion Collider Experiment (ALICE) at the LHC. Chamber-wise track segments from fast on-detector reconstruction are read out with position, angle and electron likelihood. In the Global Tracking Unit up to 6 tracklets from a particle traversing the detector layers are matched and used for the reconstruction of transverse momentum and electron identification. Such tracks form the basis for versatile and flexible trigger conditions, e.g. single high-pt …
Separation of electrons from pions in GEM TRD using deep learning
本文提出一种基于深度学习的新技术，通过在基于ATHENA框架模拟的EIC实验蒙特卡罗数据上训练人工神经网络（ANN）模型，成功实现了在GEM TRD中分离电子与π介子。
In LHC Run 3, ALICE will increase the data taking rate significantly to 50\,kHz continuous read out of minimum bias Pb-Pb events. This challenges the online and offline computing infrastructure, requiring to process 50 times as many events per second as in Run 2, and increasing the data compression ratio from 5 to 20. Such high data compression is impossible by lossless ZIP-like algorithms, but it must use results from online reconstruction, which in turn requires online calibration. These important online processing steps are the most computing-intense ones, and will use GPUs as hardware acce…
Development and characterization of MPGD-based transition radiation detectors
本研究开发并测试了基于MPGD的过渡辐射探测器，评估了GEM、Micromegas和μRWELL三种技术在高能物理实验中的应用，展示了其在电子识别和强子抑制方面的性能改进。
In LHC Run 3, ALICE will increase the data taking rate significantly to 50 kHz continuous read out of minimum bias Pb-Pb collisions. The reconstruction strategy of the online offline computing upgrade foresees a first synchronous online reconstruction stage during data taking enabling detector calibration, and a posterior calibrated asynchronous reconstruction stage. The significant increase in the data rate poses challenges for online and offline reconstruction as well as for data compression. Compared to Run 2, the online farm must process 50 times more events per second and achieve a higher…
We present measurements of the energy loss of pions and electrons in drift chambers operated with a Xe,CO2(15%) mixture. The measurements are carried out for particle momenta from 1 to 6 GeV/c using prototype drift chambers for the ALICE TRD. Microscopic calculations are performed using input parameters calculated with GEANT3. These calculations reproduce well the measured average and most probable values for pions, but a higher Fermi plateau is required in order to reproduce our electron data. The widths of the measured distributions are smaller for data compared to the calculations. The elec…
The ALICE Transition Radiation Detector contributes to the tracking, particle identification, and triggering capabilities of the experiment. It is composed of six layers of multi-wire proportional chambers, each of which is preceded by a radiator and a Xe/CO$_2$-filled drift volume. The signal is sampled in timebins of 100~ns over the drift length which allows for the reconstruction of chamber-wise track segments, both online and offline. The particle identification is based on the specific energy loss of charged particles and additional transition radiation photons, the latter being a signatu…
We present measurements of the spectral distribution of transition radiation generated by electrons of momentum 1 to 10 GeV/c in different radiator types. We investigate periodic foil radiators and irregular foam and fiber materials. The transition radiation photons are detected by prototypes of the drift chambers to be used in the Transition Radiation Detector (TRD) of the ALICE experiment at CERN, which are filled with a Xe, CO2 (15 %) mixture. The measurements are compared to simulations in order to enhance the quantitative understanding of transition radiation production, in particular the…
Using prototype modules of the ALICE Transition Radiation Detector we investigate space charge effects and the dependence of the pion rejection performance on the incident angle of the ionizing particle. The average pulse height distributions in the drift chambers operated with the Xe,CO2(15%) mixture provide quantitative information on the gas gain reduction due to space charge accumulating during the drift of the primary ionization. Our results demonstrate that the pion rejection performance of a TRD is better for tracks which are not at normal incidence to the anode wires. We present detail…
Transition Radiation Detector Upgrade for the GlueX-III Charmonium Program
该研究为GlueX-III实验设计并测试了大型三层GEM跃迁辐射探测器原型，验证了其电子鉴别与时间性能，可有效抑制背景，为未来EIC探测器升级提供参考。
At the Large Hadron Collider at CERN in Geneva, Switzerland, atomic nuclei are collided at ultra-relativistic energies. Many final-state particles are produced in each collision and their properties are measured by the ALICE detector. The detector signals induced by the produced particles are digitized leading to data rates that are in excess of 48 GB/$s$. The ALICE High Level Trigger (HLT) system pioneered the use of FPGA- and GPU-based algorithms to reconstruct charged-particle trajectories and reduce the data size in real time. The results of the reconstruction of the collision events, avai…
A Time Projection Chamber (TPC) is a powerful detector for 3-dimensional tracking and particle identification for ultra-high multiplicity events. It is the central tracking device of many experiments, e.g. the ALICE experiment at CERN. The necessity of a switching electrostatic gate, which prevents ions produced in the amplification region o MWPCs from entering the drift volume, however, restricts its application to trigger rates of the order of 1 kHz. Charge amplification by Gas Electron Multiplier (GEM) foils instead of proportional wires offers an intrinsic suppression of the ion backflow, …
Characterization of Stitched Prototypes Chip for the ALICE ITS3 Upgrade
ALICE ITS3升级采用缝合单片传感器技术，通过测试束验证其高探测效率和优异空间分辨率。
The large Time-Of-Flight (TOF) array is one of the main detectors devoted to charged hadron identification in the mid-rapidity region of the ALICE experiment at the LHC. It allows separation among pions, kaons and protons up to a few GeV/c, covering the full azimuthal angle and -0.9 < eta < 0.9. The TOF exploits the innovative MRPC technology capable of an intrinsic time resolution better than 50 ps with an efficiency close to 100% and a large operational plateau; the full array consists of 1593 MRPCs covering a cylindrical surface of 141 m2. The TOF detector has been efficiently taking data s…
A Large-Scale Pad-Sensor Based Prototype of the Silicon Tungsten Electromagnetic Calorimeter for the Forward Direction in ALICE at LHC
构建了用于ALICE前向的硅钨电磁量能器原型，在测试束流和真实碰撞中验证了能量分辨率与模拟一致，并测量了簇射分布。
Design and performance of a large-area scintillator-based chamber for the MID subsystem of ALICE 3
本文报道了ALICE 3升级项目中MID子系统闪烁体室的设计与建造，采用两层闪烁体层和硅光电倍增管读出，通过机器学习算法实现μ子鉴定，效率超过99%。
The ALICE HMPID (High Momentum Particle IDentification) detector has been designed to identify charged pions and kaons in the range 1 < p < 3 GeV/c and protons in the range 1.5 < p < 5 GeV/c. It consists of seven identical proximity focusing RICH (Ring Imaging Cherenkov) counters, covering in total 11 m2, which exploit large area MWPC equipped with CsI photocathodes for Cherenkov light imaging emitted in a liquid C6F14 radiator. The ALICE detector has been widely commissioned using cosmics and LHC beam from December 2007 until October 2008. During the cosmics data taking the HMPID detector col…
Two modules of the AD detector have been studied with the test beam at the T10 facility at CERN. The AD detector is made of scintillator pads read out by wave-length shifters (WLS)coupled to clean fibres that carry the produced light to photo-multiplier tubes (PMTs). In ALICE the AD is used to trigger and study the physics of diffractive and ultra-peripheral collisions as well as for a variety of technical tasks like beam-gas background monitoring or as a luminometer. The position dependence of the modules' efficiency has been measured and the effect of hits on the WLS or PMTs has been evaluat…
ML-based muon identification using a FNAL-NICADD scintillator chamber for the MID subsystem of ALICE 3
本文报告了用于ALICE 3 MID子系统的FNAL-NICADD闪烁体室原型在多种吸收体厚度下的性能，采用机器学习分析和GEANT 4模拟验证，并讨论了改进方向。
ALICE Upgrades
本文介绍ALICE在LHC Run 4及以后的探测器升级：FoCal与新型内层像素径迹层支持低x胶子、重味和双电子测量，ALICE 3则面向QGP重味探针、热辐射及手征对称性恢复研究。
The ITS3 detector and physics reach of the LS3 ALICE Upgrade
ALICE实验在LS3期间将安装基于弯曲晶圆级单片有源像素传感器的ITS3探测器，通过极低物质量和更近的相互作用点距离实现指向分辨率两倍提升，显著扩展重味强子和热双电子的物理研究能力。
Development of a novel compact and fast SiPM-based RICH detector for the future ALICE 3 PID system at LHC
本文提出了一种新型紧凑快速基于硅光电倍增管的RICH探测器，用于未来LHC ALICE 3 PID系统，通过气凝胶辐射体和透明窗口实现带电粒子的时间飞行测量。
A neural network method is developed to discriminate direct photons from the neutral pion background in the PHOS spectrometer of the ALICE experiment at the LHC collider. The neural net has been trained to distinguish different classes of events by analyzing the energy-profile tensor of a cluster in its eigen vector coordinate system. Monte-Carlo simulations show that this method diminishes by an order of magnitude the probability of $π^0$-meson misidentification as a photon with respect to the direct photon identification efficiency in the energy range up to 120 GeV.
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