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，由于该通道的信号背景比很低，希格斯玻色子到底夸克H&gt；BB的衰变还没有被测量到。发展从大的QCD背景中提取小的H&gt；BB信号的方法对于确定Higgs与b夸克的耦合至关重要。此外，利用双玻色子产生来研究希格斯自耦合也是非常必要的。Higgs对的产生对Higgs三线性耦合具有直接的敏感性，并提供了有关电弱对称破缺机制的重要信息。标准模型中的双希格斯产生率非常小，在14TeV时大约只有40fb，因此在大多数旨在研究希格斯自耦合的分析中都使用了最大的希格斯衰变模式H&gt；bb。这些分析包括HH-和GT；4b夸克，HH-和GT；2b夸克和2光子。安布罗兹将在大型强子对撞机上进行ATLAS实验。他将首先开发新的方法，利用数据确定高横向动量射流的b标记效率。这一点至关重要，因为大型强子对撞机现在正以更高的质心能量运行。然后，他将专注于使用先进的多变量方法来衡量H&gt；BB。他将受益于由Horizon 2020支持的AMVA4NP网络中正在进行的活动。该网络的重点是为分类和回归问题开发新的工具，这些问题首先对于发现并详细研究H&gt；BB特别重要。安布罗兹先生将研究BB末态的大QCD背景，并开发更有效的方法来使用数据来描述这一背景。他还将开发新的方法，随着第二轮大型强子对撞机光度的增加，改进H&gt；bb的b标记。长期目标是将为H&gt；bb开发的技术也应用于研究包括4个b夸克的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.