Running the CERN LHCf experiment and validating nuclear interaction models at ultra high energies

运行 CERN LHCf 实验并验证超高能量下的核相互作用模型

基本信息

批准号：
20340058
负责人：
KASAHARA Katsuaki
金额：
$ 12.15万
依托单位：
Waseda University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2008
资助国家：
日本
起止时间：
2008 至 2010
项目状态：
已结题

项目摘要

LHCf is a dedicated experiment to observe the spectrum of photons and neutrons produced in the very forward region of collisions at CERN LHC of which energy is comparable to the ultra-high energy cosmic rays (UHECR). The purpose is to validate nuclear interaction models used in the Monte-Carlo (MC) simulations for cosmic-ray experiments, and thus to help clarify the mystery of UHECR.LHCf successfully observed the 450 GeV+450 GeV collisions in the end of 2009 and also 3.5 TeV+3.5 TeV collisions in 2010. The energy is equivalent to the laboratory energy of 4.3・10^<14> eV and 2.6・10^<16> eV, respectively. We examined MC models, DPMJET(v3.04), PYTHIA(v8.145), QGSJET II(v03), SIBYLL(v2.1) and EPOS(v1.99). The spectrum in this completely unexplored region was found not completely far way from our expectation, but these models cannot fit the experimental data in a satisfactory way. The photon spectrum is softer than many MC models while hadrons show a harder spectrum. If we consider the pseudo-rapidity (η) distribution in the central region, obtained by other LHC experiments (ATLAS and CMS), together with our data, we may say all interaction models breakdown in the LHC energy region. DPMJET is a very good model in the low energy region but its photon spectrum is much harder than the LHCf data and theηdistribution suddenly breakdowns at LHC energies. PYTHIA, though tuned to fit the LHCηdistribution, shows a similar photon spectrum as DPMJET.These facts indicate that we need to explore the highest energy LHC collisions expected in a few years to clarify the breakdown tendency and to validate the models, and also that it is important to construct a new interaction model.

LHCF是一项专门的实验，可观察在Cern LHC碰撞的非常正向区域中产生的照片和中子，其能量与超高的能量宇宙射线（UHECR）相当。目的是验证用于宇宙射线实验的蒙特卡洛（MC）模拟中使用的核交互模型，从而有助于阐明2009年底成功地观察到UHECR.LHCF的奥秘成功观察到了450 GEV+450 GEV碰撞，并在2010年和3.5 TEV+3.5 TEV碰撞中均具有等效的能源。分别为2.6・10^<16> eV。我们检查了MC模型，DPMJet（v3.04），Pythia（v8.145），QGSJET II（V03），Sibyll（v2.1）和EPOS（v1.99）。发现这个完全出乎意料的区域的频谱与我们的期望并不完全远，但是这些模型无法满足于实验数据。光子光谱比许多MC模型都柔软，而Hadron显示出更难的光谱。如果我们考虑其他LHC实验（ATLAS和CMS）获得的中心区域中的伪长（η）分布，以及我们的数据，我们可以说LHC能量区域中的所有相互作用模型分解。 DPMJET是低能区域中非常好的模型，但其光子光谱比LHCF数据要困难得多，而LHC能量突然在LHC能量下突然崩溃。毕曲娅（Pythia）虽然调整为适合LHCη分布，但显示出与DPMJET相似的光子光谱。这些事实表明，我们需要探索几年内预期的最高能量LHC碰撞以阐明崩溃趋势和验证模型，并且对于构建新的交互模型也很重要。