Studies of H->bb and the Higgs self-coupling

2012年，在欧洲核子研究中心的大型强子对撞机的碰撞中发现了希格斯玻色子。尽管如此，希格斯玻色子向底夸克H- b> bb的衰变还没有被测量到，因为这个通道的信号与背景比很差。开发从大QCD背景中提取小H- b> bb信号的方法对于确定希格斯粒子与b-夸克的耦合至关重要。此外，利用二玻色子的产生来研究希格斯自耦合也是必要的。希格斯对的产生对希格斯三线性耦合直接敏感，并提供了关于电弱对称性破缺机制的重要信息。标准模型中的非希格斯粒子产生率非常小，在14 TeV时大约只有40fb，因此在大多数旨在研究希格斯粒子自耦合的分析中都使用了最大的希格斯衰变模式H- b> bb。这些分析包括HH-> 4b夸克，HH->2b夸克+2光子。安布罗兹先生将在大型强子对撞机进行ATLAS实验。他将首先开发利用数据确定高横动量射流b标记效率的新方法。这是至关重要的，因为大型强子对撞机现在运行在更高的质能中心。然后，他将重点介绍使用先进的多元方法测量H- b> bb。他将受益于地平线2020支持的AMVA4NP网络中正在进行的活动。该网络的重点是开发新的分类和回归问题的工具，这对于首先发现和详细研究H- b> bb尤为重要。Ambroz先生将研究bb最终状态下的大QCD背景，并开发更有效的方法来用数据描述这一背景。随着LHC亮度的增加，他还将开发新的方法来改进H- b> bb的b标记。长期目标将是将为H- b> bb开发的技术也应用于研究包含4个b夸克的最终态的双希格斯产生，并可用于测试希格斯自耦合。

In 2012 the Higgs boson was discovered in collisions of the Large Hadron Collider at CERN. Nonetheless, the decay of the Higgs boson to bottom quarks, H->bb, has not yet been measured due to the poor signal to background ratio in this channel. Developing methods to extract the small H->bb signal from the large QCD background is critical to determine the coupling of the Higgs to b-quarks. Furthermore, it is also essential to study the Higgs self-coupling using di-boson production. Higgs pair production is directly sensitive to the Higgs trilinear coupling and provides crucial information on the electroweak symmetry breaking mechanism. The di-Higgs production rate in the Standard Model is extremely small, approximately only 40fb at 14 TeV, and therefore the largest Higgs decay mode, H->bb, is used in most of the analyses aiming to study the Higgs self-coupling. These analyses include HH->4 b quarks, HH->2b quarks+2photons. Mr. Ambroz will work on the ATLAS experiment at the LHC. He will first develop new methods to determine the b-tagging efficiency for high transverse momentum jets using data. This is critical as the LHC is now operating at higher center of mass energies. He will then focus on the measurement of H->bb using advanced multivariate methods. He will benefit from the activities that are taking place in the AMVA4NP network, supported by Horizon 2020. This network focuses on the development of new tool for classification and regression problems that are especially important first for finding and then to study in detail H->bb. Mr. Ambroz will study the large QCD background in the bb final state and develop more effective methods to describe this background using data. He will also develop new methods to improve the b-tagging for H->bb as the luminosity of the LHC increases in run 2. The long term goal will be to apply the techniques developed for H->bb also to the study of di-Higgs production in final states that include 4 b-quarks and can be used to test the Higgs self-coupling.