Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session G18: Di-Higgs and EFTLive
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Sponsoring Units: DPF Chair: Daniela Bortoletto, Oxford University |
Sunday, April 18, 2021 8:30AM - 8:42AM Live |
G18.00001: Search for Di-Higgs boson production with llbb+ET^miss channel with the ATLAS detector Shuzhou Zhang Observing the production of Higgs boson pairs and measuring the Higgs boson self-coupling is important to both validating the Higgs mechanism in the Standard Model and searching for new physics predicted by BSM models. Many highly motivated models predict the existence of heavy particles decaying into a pair of Higgs bosons. This analysis is to search for Higgs boson pair production from the SM Higgs or BSM Higgs decays with final state of $bbll\nu\nu+E_T^{miss}$ in proton-proton collisions at $\sqrt{s}=13$ TeV. The analysis uses full Run II data collected with the ATLAS detector to an integrated luminosity of 139 fb$^{-1}$. We introduced a deep neural network approach in this analysis to extract signal from background to improve the final significance in the search for non-resonant Higgs boson pair production, while we use a parameterized deep neural network in the search for resonant Higgs boson pair production in the high mass region. [Preview Abstract] |
Sunday, April 18, 2021 8:42AM - 8:54AM Live |
G18.00002: Studies of $t\bar{t}HH$ couplings with the CMS Detector Wei Wei Precision measurements of the Higgs boson couplings to SM particles is a central task at the LHC today and for the HL-LHC in the future. Due to the $\sim$ O(nb) $t\bar{t}$ cross section and large Yukawa coupling, measurements of the interaction of the Higgs with top quarks is particularly compelling. Both $t\bar{t}H$ and $t\bar{t}HH$ signals can be used to probe this coupling. In this analysis, we search for $t\bar{t}HH$ production with the CMS detector at the LHC, including possible deviations signalling BSM physics. As a toy model, to study this signal independently of $t\bar{t}H$, we introduce both 6D and 8D gauge-invariant operators to modify $t\bar{t}HH$ while keeping $t\bar{t}H$ unchanged at tree level. In this model which includes a BSM $t\bar{t}HH$ vertex, Higgs are produced at higher $p_T$ compared with those from SM production. Due to the resulting Lorentz boost, we observe an enhancement around the Higgs mass in the single b-jet mass spectrum. Thus, boosted Higgs decaying to b-pairs appears to be a relevant signature to reduce the SM background for this search. To optimize signal efficiency, we apply techniques such as ML based double b-tagging for clustered b-jet identification and energy correlation functions. [Preview Abstract] |
Sunday, April 18, 2021 8:54AM - 9:06AM Live |
G18.00003: Search for Higgs Boson Pair Production in the Multi-lepton Final State Using Proton-Proton Collision Data at $\sqrt{s} =13$ TeV from the ATLAS Detector Santosh Parajuli This talk will present a search strategy for Higgs boson pair-production in final states with three electrons or muons. The analysis is performed using an integrated luminosity of 139 fb$^{-1}$ of $pp$ collision at $\sqrt{s}= 13$ TeV collected by the ATLAS detector at the LHC. There are many decay modes of Higgs boson pairs that have low branching ratios, and many of these are not covered by dedicated analyses. Some example modes of particular interest for a three lepton final state are WWWW, WW$\tau \tau$, $\tau \tau \tau \tau$, etc. This talk presents the development of a multivariate strategy (boosted decision trees) and current work on background estimation methods and statistical analysis. [Preview Abstract] |
Sunday, April 18, 2021 9:06AM - 9:18AM Live |
G18.00004: Study the Di-Higgs Detection Sensitivity With the ATLAS Detector Using Machine-Learning Approach With XGBoost Xiuyuan Zhang, Bing Zhou I will present my study on the di-Higgs detection sensitivity with Machine-Learning analysis technique. The di-Higgs decay channels used in my study include bb 𝜏𝜏, bb WW, and bb ZZ. The experimental final state is bbll+$E^{miss}_T$. My analysis is based on the ATLAS analysis framework and ROOT (the HEP analysis package). We studied the kinematic distributions of the events from signal and background processes based on Monte Carlo simulated events and compared these distributions with data collected by the ATLAS experiment in Run 2. We first determined and applied event selection cuts to variables which have discriminate power to increase the signal detection sensitivity. Then, using XGBoost (boosted Decision tree program), we trained a multi-class BDT to separate the di-Higgs decay signal from background events to further increase the signal detection sensitivity. Preliminary results show that detection sensitivity could be improve by about a factor of three compared to cut-based analysis. [Preview Abstract] |
Sunday, April 18, 2021 9:18AM - 9:30AM Live |
G18.00005: Theoretical Uncertainties in the Higgs Boson Pair Production in the $b\bar{b}\tau\tau$ Decay Channel Jem Guhit Higgs boson pair production (HH) is one of the more interesting processes to study at the LHC, as it allows us to probe Higgs Boson self-coupling and associated parameters of the Higgs potential, as well as search for physics beyond the standard model. The $b\bar{b}\tau\tau$ final state is one of the most sensitive channels for HH studies due to an appreciable branching ratio, and a relatively clean background. In this talk, the methods used in calculating a few of the more important theoretical uncertainties associated with this analysis are presented - perturbative QCD (pQCD) calculations and Parton Showers for single Higgs backgrounds. From pQCD, main sources of uncertainties come from (i) missing higher orders in the perturbative expansion from the partonic cross section, (ii) parton distribution functions and (iii) experimental determination of the strong coupling constant. These uncertainties associated with pQCD correspond to parton-level final states. Since the simulated samples also pass-through showering and hadronization generators that converts the parton cross section to a hadron level cross section, additional uncertainties occur in (i) modelling parton shower and hadronization through the algorithm and (ii) matrix element next-to-leading-order calculations. [Preview Abstract] |
Sunday, April 18, 2021 9:30AM - 9:42AM Live |
G18.00006: Probing Wilson Coefficient in an EFT Model using VH All Hadronic Decays Syed Haider Abidi, Viviana Cavaliere With the discovery and its subsequent measurements at the LHC, the Higgs boson has been firmly established and now is being used as a probe for new physics. The Effective field theory (EFT) framework parametrizes a large variety of new BSM scenarios. Sensitivity to various Wilson coefficients comes from high energy processes where a variety of particles are involved. One such process is the fully hadronically decaying vector associated Higgs (VH) production. We present first estimates of the constraints on various operators that can be derived by probing this process at the HL-LHC. [Preview Abstract] |
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