TeV能区物理

文章简要介绍研究TeV能区物理的意义、重要性和当前国际上的发展形势,以及清华大学粒子物理理论组为发展TeV能区物理研究所做的工作和取得的成果.     

用地面阵列寻找TeV能区γ点源的方法探讨

文中探讨搜寻TeV能区γ点源的方法.讨论利用student变量t判断来自源区及背景区宇宙线事例的统计差别,并由Bayes定理与MonteCarlo模拟相结合计算源区各能段的信号数,推算蟹状星云在TeV能区的γ射线微分能谱     

太阳大耀斑期间甚高能粒子流强增加的一种机制

近年来,在太阳大耀班期间,由地面中子记录装置及地下不同深度μ子记录器记录到宇宙线粒子的短期增长(GLE)现象,其能量范围已达几百GeV,甚至可达TeV能区.本文讨论了TeV能区的增长现象可能是银河宇宙线部分粒子获得再加速,由于宇宙线粒子能谱很陡,几百GeV的再加速能量能使TeV以上能区宇宙线流强有明显增长.     

用神经网络分辨原初宇宙线成分

尝试在高山乳胶室实验中用神经网络的方法区分超高能区原初宇宙线当中的质子和原子核,对模拟数据的分析结果表明,当族事例观测能量大于500TeV时,对质子和原子核的分辨率均能稳定在80%附近;而当族事例观测能量在100TeV和500TeV之间时,对质子和原子核的分辨率均大于70%.     

10TeVγ射线的星系际红外背景光子吸收现象的研究

TeVγ射线在星系际空间传播过程中将与红外背景光子作用而被衰减或吸收.大气ˇC成像望远镜实验观测到了Mrk421和Mrk501处于活动高态时的TeVγ射线发射并测出它们的能谱.报道了利用TibetⅡ/HD阵列在1995年10月至1997年至8月收集的数据,通过Mrk421和Mrk501的能谱研究星系际红外背景光子吸收现象的初步结果.结果显示:直到30TeV能区尚未观测到Mrk421和Mrk501能谱中存在统计上具有显著意义的红外背景光子吸收10TeVγ射线的现象.     

大型强子对撞机上的CMS探测器

CMS探测器是大型强子对撞机(LHC)上的4个实验之一,它的设计思想是在质心能量为14TeV及积分亮度为1034cm-2s-1的条件下对质子-质子对撞进行研究.它的特点是非常紧凑,其μ子室几乎覆盖了4π立体角.另外,CMS探测器还有可提供超强磁场的超导磁铁和由超导磁铁环绕的径迹室以及电磁量能器和强子量能器.CMS探测器对于末态为电子、光子、特别是μ子的物理过程有很好的测量精度.     

寻找10TeV能区的γ射线暴

利用西藏羊八井大气簇射实验数据,开展了对10TeV能区γ暴的全天区搜寻. 分析了4亿个簇射事例,找出在给定的时间间隔和给定的小天区内出现的簇射事例团. 采用等天顶角方法来估计背景. 有少量事例团显示了对背景的超出,但它们的显著性还不够高,尚不足以认定为γ暴. 讨论了羊八井二期阵列实验对寻找10TeVγ暴所具有的高灵敏度.     

用羊八井ASγ实验数据寻找TeV能区的γ射线暴

γ射线暴的TeV能区辐射对研究其起源、辐射机制等是非常重要的.利用西藏羊八井ASγ实验三期阵列的重建数据,通过在给定的小天区和时间间隔内寻找较高显著性事例团的方法对TeV能区的γ射线暴进行了寻找,在计算过程中采用“等天顶角法”来估计背景.工作中采用了两种途径来寻找γ射线暴,一种是与卫星γ射线暴的符合寻找,另一种是全天区独立寻找.结果发现少量事例团对背景有明显超出,考虑试验次数后,其超出还不足以认定为γ射线暴.通过Monte Carlo模拟,给出了在95%置信水平下,到达大气顶部流强上限的估计值为3.32×10^-9—1.24×10^-7 cm^-2s^-1. 关键词： γ射线暴 TeV能区 ASγ实验 宇宙射线     

清华大学高能物理研究中心TUHEP

“清华大学高能物理研究中心”主要从事粒子物理理论和实验研究，与国内外进行学术交流，重点研究方向是TeV能区物理，同时也开展高能核物理研究。名誉主任：王乃彦院士主任：高原宁学术委员会主席：邝宇平院士中心成员：毕楷杰，陈少敏，高原宁，何红建，邝宇平，王青，张斌，庄鹏飞高能中心主办的“直线对撞机物理、探测器与加速器”国际研讨会／暑期学校于2005年7月15-20日在清华大学理学院报告厅举行。左图为参会成员合影。理论方面研究范围：粒子物理理论以及对国际上各高能物理实验的理论预言和唯象分析；中低能粒子物理及各种非微扰…     

宇宙线超高能多核心族事例

本文报道了甘巴拉山乳胶室在核乳胶片上记录的宇宙线超高能多核心族事例KOE19(ΣE_γ≈1530TeV). 分析了事例的族现象特征, 并同其它大族事例进行比较. 把事例中的几个主要核心的特性同加速器和C喷注的实验结果以及TeV能区唯象QCD理论计算结果作了比较, 讨论了TeV能区超高能粒子强相互作用的一些特征.     

Performance of LHAASO-WCDA and observation of the Crab Nebula as a standard candle

The first Water Cherenkov detector of the LHAASO experiment (WCDA-1) has been operating since April 2019. The data for the first year have been analyzed to test its performance by observing the Crab Nebula as a standard candle. The WCDA-1 achieves a sensitivity of 65 mCU per year, with a statistical threshold of 5 \begin{document}$\sigma$\end{document}. To accomplish this, a 97.7% cosmic-ray background rejection rate around 1 TeV and 99.8% around 6 TeV with an approximate photon acceptance of 50% is achieved after applying an algorithm to separate gamma-induced showers. The angular resolution is measured using the Crab Nebula as a point source to be approximately 0.45° at 1 TeV and better than 0.2° above 6 TeV, with a pointing accuracy better than 0.05°. These values all match the design specifications. The energy resolution is found to be 33% for gamma rays around 6 TeV. The spectral energy distribution of the Crab Nebula in the range from 500 GeV to 15.8 TeV is measured and found to be in agreement with the results from other TeV gamma ray observatories.     

Ultra-high energy cosmic rays and prompt TeV gamma rays from gamma ray bursts

Gamma ray bursts (GRBs) have been proposed as one possible class of sources of the ultrahigh energy cosmic ray (UHECR) events observed up to energies ≳ 10²⁰ eV. The synchrotron radiation of the highest energy protons accelerated within the GRB source should produce gamma rays up to TeV energies. Here we briefly discuss the implications on the energetics of the GRB from the point of view of the detectability of the prompt TeV γ-rays of proton-synchrotron origin in GRBs in the up-coming ICECUBE muon detector in the south pole.     

寻找超高能宇宙线源——西藏广延空气簇射实验

总结了１９９０年６月到１９９３年１０月期间西藏空气簇射阵列的观测结果。寻找了来自于蟹状星云、Ｘ射线双星、脉冲星、活动星系核和其它活动天体的能量为１０ＴｅＶγ射线连续发射，没有发现连续稳定发射的迹象，但给出了每个源的流强上限。在阵列所观测的天区寻找了１０ＴｅＶ的γ暴，结果没有发现能量１０ＴｅＶ的γ暴，最后也给出了发现此种γ暴的上限。应用该阵列，明显地观测到了能量为１０ＴｅＶ的宇宙线流强的太阳和月亮阴影。观测了朝向和远离太阳的行星际空间磁场对宇宙线阴影的影响，这是行星际磁场对阴影位移影响的第一次直接观测。研究并发现在实验期间，太阳阴影的位置每年都在变化。同时观测在此期间，朝向和远离方向的宇宙线阴影的不同变化。另外，应用该实验的数据，给出了所谓的“膝”区的原初宇宙线能谱。     

高能宇宙射线数值模拟中能谱指数的标定

在利用TeV能区宇宙射线数值模拟数据研究朝前区强子相互作用时, 需要足够多的低空簇射事例样本。提出了可以通过降低FIXCHI（宇宙射线第一次相互作用高度）来提高高能宇宙射线数值模拟效率,但对相应的能谱指数进行标定是必要的。以1 TeV处直达概率为标准, 得到各能区的能谱强度, 并采用将能谱强度与能量进行线性拟合, 以标定能谱指数的方法, 使宇宙射线数值模拟的效率及准确率都大大提高。 In the study of hadronic interaction in the forward region by the simulation of cosmic ray, it is necessary to simulate large numbers of cosmic ray events with low first interaction height. We confirmed that by reducing the FIXCHI the efficiency of cosmic ray simulation can be improved. But the calibration for energy slope is needed. We got the energy slope based on the probability of direct arrived events with energy of 1 TeV, and fitted the intensity of spectrum with energy to make certain the energy slope of high energy cosmic ray. By this way, the efficiency and precision of cosmic ray simulation is greatly improved.     

A STUDY OF ULTRA-HIGH ENERGY γ-RAYS BY EMULSION CHAMBERS

Ultra-high energy γ-rays have been observed by emulsion chambers exposed at Yunnan Station （3200m, 700g/cm² atmospheric depth）. The integral spectrum, the vertical intensity and the attenuation length in air of the gamma rays in the energy region 2 TeV to 30 TeV are presented. The results of gamma ray families with total observed energies ranging from 5 TeV to 70 TeV are discussed.     

Will protons become gray at 13 TeV and 100 TeV?

It is shown that the regime of pp-interactions at 7 TeV is a critical one. The LHC data about elastic pp-scattering at 7 and 8 TeV are used to get some information about both elastic and inelastic profiles of pp-collisions. They are discussed in the context of two phenomenological models which intend to describe the high energy pp-data with high accuracy. Some predictions following from these models for an LHC energy of 13 TeV and for an energy of 95 TeV of the newly proposed collider are discussed. It is claimed that the center of the inelastic interaction region will become less dark with an increase of energy albeit very slowly.     

Lepton Electric Charge Swap at the 10 TeV Energy Scale

We investigate the nature of the dark matter by proposing a mechanism for the breaking of local rotational symmetry between ordinary third family leptons and proposed non-regular leptons at energy scales below 10 TeV. This symmetry breaking mechanism involves electric charge swap between ordinary families of leptons can and produces highly massive non-regular leptons of order 0 （1 TeV） mass unobservable at energy scales below 10 TeV （the scale of LEP Ⅰ, Ⅱ and neutrino oscillation experiments）. Electric charge swap between ordinary families of leptons produces heavy neutral non-regular leptons with order 0 （1 TeV） masses, which may form cold dark matter. The existence of these proposed leptons can be tested once the Large Hadron Collider （LHC） becomes operative at 10 TeV energy-scales. This proposition may have far reaching applications in astrophysics and cosmology.     

Lepton Electric Charge Swap at the 10 TeV Energy Scale

We investigate the nature of the dark matter by proposing a mechanism for the breaking of local rotational symmetry between ordinary third family leptons and proposed non-regular leptons at energy scales below 10 TeV. This symmetry breaking mechanism involves electric charge swap between ordinary families of leptons can and produces highly massive non-regular leptons of order O (1 TeV) mass unobservable at energy scales below 10 TeV (the scale of LEP Ⅰ, Ⅱ and neutrino oscillation experiments). Electric charge swap between ordinary families of leptons produces heavy neutral non-regular leptons with order O (1 TeV) masses, which may form cold dark matter. The existence of these proposed leptons can be tested once the Large Hadron Collider (LHC) becomes operative at 10 TeV energy-scales. This proposition may have far reaching applications in astrophysics and cosmology.