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 S19: BSM Higgs PhysicsLive
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Sponsoring Units: DPF Chair: Xing Wang, UCSD |
Monday, April 19, 2021 1:30PM - 1:42PM Live |
S19.00001: Search for Higgs boson decays to invisible final states produced in vector boson fusion in association with a low pT photon with the ATLAS detector Nicholas Felice Some new physics extensions of the Standard Model predict that the 125 GeV Higgs boson can be a portal to invisible dark matter candidates through its decay. Direct searches for Higgs boson decay to invisible particles are a convenient way to explore this scenario. I present the results of a search for invisible decays of the Higgs boson produced through the vector boson fusion channel with an associated low pT photon in $pp$ collisions at $\sqrt{s}=$ 13 TeV with the ATLAS detector. I will discuss the main backgrounds, signal optimization, and uncertainties associated with the analysis, as well as the upper limit on the branching ratio of the Standard Model Higgs boson to a pair of invisible particles. [Preview Abstract] |
Monday, April 19, 2021 1:42PM - 1:54PM Live |
S19.00002: Probing off-shell Higgs portals at colliders Maximilian Ruhdorfer, Ennio Salvioni, Andreas Weiler We present the reach of current and future colliders on the vector boson fusion production of invisible scalars through an off-shell Higgs boson. The two leading Higgs portals, {\it renormalizable} and {\it derivative}, are discussed and their sizable differences highlighted. We consider a variety of future high-energy lepton and hadron colliders, emphasizing the unique potential of a multi-TeV muon collider to probe this “nightmare scenario” for new physics. The impact on strongly motivated theoretical models is assessed, including pseudo-Goldstone WIMP dark matter, electroweak baryogenesis, and neutral naturalness. Based on arXiV:1910.04170 [hep-ph] (published in SciPost Physics 8 (2020) 027), and work in progress. [Preview Abstract] |
Monday, April 19, 2021 1:54PM - 2:06PM Live |
S19.00003: Search for Generic Heavy Higgs Boson Using 13 TeV pp Collision Data at ATLAS Yue Xu We present an indirect search for a fermi-phobic heavy Higgs boson, through potential dimension-6 effects in an effective field theory context, which can cause significant kinematic deviations from those predicted within the Standard Model. The $pp \rightarrow W^{\pm}H \rightarrow W^{\pm}W^{\pm}W^{\mp}$ process is considered with 139 fb$^{-1}$ of $pp$ collision data at $\sqrt{s}=13~\text{TeV}$ collected by the ATLAS detector. Events with two same-sign leptons ($e$ or $\mu$) in association with one large-R jet or two small-R jets with an invariant mass consistent with a hadronically decaying $W$-boson are analyzed to test for the presence of effects from new physics. [Preview Abstract] |
Monday, April 19, 2021 2:06PM - 2:18PM Not Participating |
S19.00004: Search for new physics in an extended Higgs sector in the 4b final state Marc Osherson, Eva Halkiadakis, Scott Thomas, Rebecca Kowalski The discovery of the standard model Higgs boson at the LHC does not exclude an extended Higgs sector. There are many possible variations of such a model, but one feature is true in general: if such a sector has an approximate global symmetry and spontaneous symmetry breaking, there exist two scalar particles which we have not yet discovered. The heavier of these ($X$) would have a large branching fraction to the lighter of the two ($a$), which itself has Higgs-like couplings. One of the most prominent signatures of this extended Higgs sector would be $X \rightarrow aa \rightarrow (bb)(bb)$, at least if the mass of the $a$ is less than twice that of the top quark. In this talk, we present the first search for this model in proton-proton collisions, using data collected by CMS at a center of mass energy of 13 TeV, and corresponding to an integrated luminosity of 137 fb$^{-1}$. In particular, we consider the case where the mass of the $X$ is sufficiently large compared to that of the $a$ such that each pair of b-quarks is reconstructed as a single large radius jet with substructure. We present cross-section limits as a function of both the $X$ and $a$ masses, and propose extensions of the analysis to further probe the range of possible extended higgs sectors. [Preview Abstract] |
Monday, April 19, 2021 2:18PM - 2:30PM Live |
S19.00005: Investigating the Unexplored H$\to$4g Decay Mode With Machine Learning Analysis Techniques in $pp$ Collisions at $\sqrt{s}=$ 13 TeV With the ATLAS Detector Murtaza Safdari ATLAS is investigating a previously unexplored final state of the Higgs boson (H) decaying to four gluons (g). Several Beyond Standard Model (BSM) physics models propose a coupling of the Standard Model (SM) Higgs to new scalars or pseudoscalars (a), which in turn can decay to gluons via BSM-SM physics interactions. Previous analyses have searched for other decay modes of the BSM scalars, but none have looked for the 4g final state due to its experimental challenges. With the full 139 fb$^{-1}$ of data ATLAS collected over the 2015-2018 run, sensitivity to the H$\to$aa$\to$4g decay can be reached with innovative Machine Learning (ML) analysis techniques. The mass range of the scalar being targeted in this analysis is 1 - 15 GeV/c$^2$, wherein the a$\to$gg decay is contained within the same jet in the ATLAS detector. This leads to a unique substructure in the jets which can be harnessed using ML classifiers designed to learn the distinct features of a di-gluon jet arising from the decay of a scalar. The analysis also employs cutting edge background estimation techniques to decorrelate the outputs of the ML classifiers with the axes used for the estimation. The analysis provides complementary sensitivity with indirect constraints. [Preview Abstract] |
Monday, April 19, 2021 2:30PM - 2:42PM Live |
S19.00006: Search for a Light Pseudoscalar Higgs Boson in the Two Higgs Doublet Model using Data from the Large Hadron Collider (LHC) Redwan Habibullah A search is presented for a light pseudoscalar Higgs boson (a) using data collected by the CMS experiment at LHC, at centre-of-mass of energy of 13 TeV. The study looks into the decay Higgs boson (H) via the H$\to $aa$\to \mu \mu \tau \tau $ channel. The Higgs boson can be both standard-model-like (125 GeV) or heavier. The pseudoscalar mass falls within the range m$_{\mathrm{a\thinspace }}\epsilon $[2m$_{\mathrm{\tau }}$,m$_{\mathrm{H}}$/2]. The large mass difference between the Higgs and the pseudoscalar means that the final tau lepton decay products are highly boosted in the decay direction and collimated. A modified version of tau reconstruction is used to account for the highly overlapping decay products. The modified reconstruction technique gives higher reconstruction efficiency over the standard tau reconstruction and hence better signal significance and background rejection. This technique also becomes useful when looking into various final states, especially the ones where one of the taus decays hadronically while the other decays leptonically ($\mu $/e). respectively.The performance of the altered reconstruction technique, as opposed to the standard tau reconstruction, is also presented. The results from the 2016 and 2017 CMS datasets will be shown. [Preview Abstract] |
Monday, April 19, 2021 2:42PM - 2:54PM Live |
S19.00007: Rare Higgs Decays to $Z$ $J/\psi$ Himal Acharya Rare decays of Higgs bosons into the $Z$-boson together with a vector meson are a promising laboratory to search for physics beyond the standard model (BSM). Such BSM physics might alter Yukawa couplings to lighter quarks and add loop diagrams, possibly resulting in higher decay rates than predicted by the standard model. A search for decays of the Higgs boson into a $Z$-boson and a $J/\psi$ meson, with subsequent decays of the $J/\psi$ meson into muon pairs, and the $Z$-boson into an electron or muon pair is performed with the Compact Muon Solenoid detector at the Large Hadron Collider (LHC). A data sample of proton-proton collisions collected at a center-of-mass energy of 13 TeV during the LHC Run-2 is used. I will present the searches and implications for future searches of BSM signatures at high luminosity. [Preview Abstract] |
Monday, April 19, 2021 2:54PM - 3:06PM Live |
S19.00008: Search for Higgs Boson decaying to long-lived scalar particles in $pp$ collisions at $\sqrt{s}=13$TeV with the ATLAS Detector Amber Roepe Many theories beyond the SM predict the existence of new particles with a macroscopic decay length, referred to as Long-Lived Particles (LLPs). These LLPs can help us understand the difference in scale of our fundamental forces, known as the hierarchy problem. We performed a search for decays of the Higgs boson to two long-lived neutral scalar particles $a$, in which each $a$ decays to a pair of $b$ quarks. As a result of the $a$ lifetime, the $b$ quarks are displaced. Therefore, our analysis requires the use of a special reconstruction algorithm, referred to as "Large Radius Tracking" (LRT). LRT was optimized to have a very high efficiency at the expense of high fake rate and CPU consumption. It is only feasible to use this algorithm on a specially selected $\sim$10\% of the data collected. I developed an algorithm to select potential signal events for reconstruction with LRT, based on the results of the standard reconstruction. From the collection of LRT tracks, it is possible to reconstruct high-mass displaced vertices, for which there is no SM background. This is a novel search within the ATLAS experiment which provides unique sensitivity to this important signal between that of prompt searches and long-lived searches targeting decays in the calorimeter or muon spectrometer. [Preview Abstract] |
Monday, April 19, 2021 3:06PM - 3:18PM Live |
S19.00009: Search for Charged Higgs decaying into a top and bottom quark with a single leptonic final state Michael Lukasik, Jingyu Luo Many extensions of the Standard Model include the addition of a charged Higgs boson. The two-Higgs doublet model (2HDM) is one such extension that predicts a doublet of such particles. The type II model of 2HDM predicts three neutral Higgs bosons along with a positive and negative charged pair of Higgs bosons. In this talk, we present a search for these charged Higgs bosons decaying into a top and bottom quark and ending in a single leptonic final state. We perform a multivariable analysis using a Boosted Decision Tree approach to aid in signal and background discrimination. CMS data collected at 13 TeV in 2017 (41.5 fb\textasciicircum \textbraceleft -1\textbraceright ) and 2018 (59.97 fb\textasciicircum \textbraceleft -1\textbraceright ) are considered in this search. [Preview Abstract] |
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