基于GRPC新型高颗粒度强子量能器读出系统的研究

The discovery of the Higgs boson at LHC is a great achievement in particles physics field. To understand better the nature of the new particle and to study its couplings with the goal to investigate the possibility of the presence of new physics beyond the Standard Model(SM), a new generation of colliders equipped with detectors allowing high precision measurement is needed. One of the techniques that are being visaged to achieve such precise measurement is based on the so-called Particle Flow Algorithms (PFA) which are based on the possibility to follow the different particles produced in beam collisions in the different sub-detectors and then use the most precise one to measure the energy/momentum of those particles. This means that calorimeters should be endowed with tracking capabilities in addition to their capability to measure particles energy. This will allow to have excellent jet energy resolution which an essential element to understand the particles physics at high energy scales. To achieve this high granularity calorimeters are needed...These highly granular calorimeters are not only candidates for the future high energy electron-positron colliders (ILC, CLIC, TLEP,CEPC), but are also an option in the upgrade scenarios of existing experiments...One of the proposed for highly granular hadronic options is based on Glass Resistive Plate Chambers as the sensitive medium and stainless steel plates for absorber. In this proposal, the signal created by the passage of charged particles in GRPC detector is collected thanks to small size pads etched on one side of the electronics board put in contact with the GRPCs. In this option there are three read-out models which are analog, digital and semi-digital readout( 2-bits readout). The readout model and the pad size are important factors to determine the energy resolution and the cost of electronics. ..The project we present here will be based on the Geant4 simulation to study the relation between different readout models , the different pad size and their impact of the energy resolution. The simulation results will use the beam test data of DHCAL(digital-readout HCAL) and SDHCAL(semi-digital readout HCAL) which both of are based on 1cm2 pad size to validate our simulation model. We will then consider the different possible scenarios and measure their impact on the jet energy resolution and on the cost of electronics.

未来正负电子对撞机将以更高精度探测希格斯粒子（2013年诺贝尔物理奖授予提出此粒子的科学家）和超出标准模型的物理。高精度的探测需要将Particle Flow算法结合高颗粒度强子量能器，此新型强子量能器也可实现现有实验量能器的升级。基于玻璃阻性板室（GRPC）的高颗粒度强子量能器是近几年国际研究的前沿，但昂贵的电子学造价制约了其广泛使用。本课题所研究的读出系统在保证高精度探测的同时降低电子学造价。本项目首先针对GRPC气体室做感应电荷大小和分布等研究并将其嵌入到Geant4模拟中，进一步就三种读出方式（模拟、数字和半数字）和不同尺寸读出块（1cm，3cm，5cm…）组合的读出系统重建出的能量分辨率做比较，并与1cm大小读出块的数字化和半数字化强子量能器原型(prototype)的束流数据交叉验证，最后提出最佳的读出系统。

高粒度型强子量能器结合Particle Flow算法可将能量分辨率提高到30%/sqrt(E)，是目前两倍左右，会以更高精度探测希格斯粒子（2013年诺贝尔物理学奖授予了提出该粒子的两位主要科学家）。高粒度型强子量能器不仅是未来正负电子对撞的希格斯工厂所必须，也可用作现有量能器升级的首选。基于GRPC的高粒度型强子量能器已在美法等国展开研究，但其能量分辨率和电子学造价还一直是国际上有争议的前沿问题，读出方式和读出块尺寸是决定能量分辨率和电子学造价的主因。目前并没有相关研究怎样的读出方式，多大的读出块即可满足能量分辨率又可减少电子学造价。.本项目研制了不同玻璃制作的RPC的性质，并做了测试和比较，得到比较好的RPC收集电荷分布，并将此分布放入Geant4程序中，作为电荷分布和读出多重数的输入参数。并利用Geant4模拟了半数字读出下，不同尺寸的读出块重建出的能量分辨率，并利用已有的基于1cm大小读出块的半数字化强子量能器的束流数据验证模拟的正确性，最后结合工程造价给出最佳的读出方式和读出块尺寸的组合。为将来我国的正负电子对撞机（CEPC）的量能器的建设提供了优化方案。.在基金的支持下，以第一作者发表了3篇高水平SCI论文；参加了3次国际会议，并作大会口头报告；参加了在欧洲核子中心的高粒度量能器的束流测试；参加了CEPC和江门中微子国际合作组（JUNO）；培养了2名硕士生。