Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session M9: Higgs II |
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Sponsoring Units: DPF Chair: Dmitri Denisov, FermiLab Room: Roosevelt 1 |
Sunday, January 29, 2017 3:30PM - 3:42PM |
M9.00001: Modeling Multi-Variate Gaussian Distributions and Analysis of Higgs Boson Couplings with the ATLAS Detector Olivia Krohn, Aaron Armbruster, Yongsheng Gao Software tools developed for the purpose of modeling CERN LHC $pp$ collision data to aid in its interpretation are presented. Some measurements are not adequately described by a Gaussian distribution; thus an interpretation assuming Gaussian uncertainties will inevitably introduce bias, necessitating analytical tools to recreate and evaluate non-Gaussian features. One example is the measurements of Higgs boson production rates in different decay channels, and the interpretation of these measurements. The ratios of data to Standard Model expectations ($\mu$) for five arbitrary signals were modeled by building five Poisson distributions with mixed signal contributions such that the measured values of $\mu$ are correlated. Algorithms were designed to recreate probability distribution functions of $\mu$ as multi-variate Gaussians, where the standard deviation ($\sigma$) and correlation coefficients ($\rho$) are parametrized. There was good success with modeling 1-D likelihood contours of $\mu$, and the multi-dimensional distributions were well modeled within 1-$\sigma$ but the model began to diverge after 2-$\sigma$ due to unmerited assumptions in developing $\rho$. Future plans to improve the algorithms and develop a user-friendly analysis package will also be discussed. [Preview Abstract] |
Sunday, January 29, 2017 3:42PM - 3:54PM |
M9.00002: Search for new phenomena with the Z( $\to $l$^{+}$l$^{-\, })+$E$_{T}^{Miss}$ final state in pp collision at $\surd $s $=$ 13 TeV with the ATLAS detector Wen Guo I will report a search for new phenomena in the Z( $\to $l$^{+}$l$^{-\, })+$E$_{T}^{Miss}$ final state at $\surd $s $=$ 13 TeV with the ATLAS detector. The underlying new physics signature with this final state includes (1) heavy resonance (such as heavy Higgs) decaying to two Z bosons with ZZ$\to $llvv final state; (2) invisible Higgs decays in association with Z boson production, where Z decays to dilepton; and (3) Mono-Z production associated with dark matter production. Data used in the analysis are from proton-proton collisions at $\surd $s $=$ 13 TeV from the LHC, and collected by the ATLAS experiment. With no deviation observed from standard model predictions, we set upper bounds on the production cross section times branching fraction in the context of the new physics models considered. [Preview Abstract] |
Sunday, January 29, 2017 3:54PM - 4:06PM |
M9.00003: Inclusive Higgs Production at Large Transverse Momentum Hong Zhang, Eric Braaten The transverse momentum ($p_T$) distribution of Higgs is important to check our understanding of the Standard Model, and study new physics. The effective field theory for Higgs, obtained by integrating out the top quark, breaks down when $p_T$ is larger than 200 GeV. We calculate the $p_T$ distribution at much larger $p_T$ using the framework of factorization, in which the cross section is expressed as convolutions of hard-scattering cross sections and fragmentation functions, with the leading logarithms of $p_T^2/m_H^2$ resummed to all orders. By separating the scales $m_H$ and $p_T$, the higher order radiative correction can be greatly simplified. [Preview Abstract] |
Sunday, January 29, 2017 4:06PM - 4:18PM |
M9.00004: Leptonic flavor violation in the Higgs sector at the LHC Brent McCoy, Chung Kao, Wei-Shu Hou, Masaya Kohda, Amarjit Soni We present the discovery potential of $p p \rightarrow \phi^0 \rightarrow \tau \mu +X$ at the Large Hadron Collider (LHC), with $\phi^0 = h^0 , \ H^{0} , \ A^0$. We choose a general Two Higgs Doublet Model (2HDM) with non-negligible flavor changing couplings in the hadronic sector, in which $\phi^0$ couples to $t c$. Current data favors the alignment limit of a 2HDM where $\sin(\beta - \alpha) \approx 1$, which can enhance leptonic couplings to the light Higgs boson and might provide an observable flavor changing cross-section in that sector. We study the $\phi^0 \rightarrow \tau \mu$ channel for a range of $\cos(\beta - \alpha)$ and $\rho_{\tau \mu}$ values that can be consistent with the CMS excess in Run-1 and account for dominant physics background with realistic acceptance cuts at $\sqrt{s} = $ 13 TeV and 14 TeV. [Preview Abstract] |
Sunday, January 29, 2017 4:18PM - 4:30PM |
M9.00005: Hadronic flavor violation in pp -> t phi + X and p p -> t t~ -> bjjc phi +X channels at the LHC Rishabh Jain, Brent Mccoy, Chung Kao, Jackson Sloan We present a study of flavor changing neutral Higgs interaction in $p p \rightarrow t \phi^0 + X $ and $ p p \rightarrow t\bar{t} \rightarrow b j j c \phi^0 + X$ , where $\phi^0$ = $h^0 $ or $H^0$ , at the Large Hadron Collider(LHC). We choose a general two Higgs doublet model (2HDM) to study the $g_{htc}$ couplings with particular emphasis on the $\phi^0 \rightarrow W W \rightarrow l \nu l \nu $ decay channel. With high top production cross section at the LHC,we expect these low background channels to provide a clean signature of flavor changing neutral current among up-type quarks in the Higgs sector and conduct detector simulations to study the visibility and significance of our signal for several values of Higgs masses and the $g_{htc} $ couplings at the LHC. We include standard model (SM) physics background with realistic acceptance cuts at $\sqrt{s}$ = 13 TeV and 14 TeV. [Preview Abstract] |
Sunday, January 29, 2017 4:30PM - 4:42PM |
M9.00006: The search for electroweak-scale right-handed neutrinos and mirror charged leptons through like-sign di-lepton signals Shreyashi Chakdar, Pham Q Hung, Vinh Hoang, K Ghosh, S. Nandi There are four ideas that has been proposed to explain the tiny neutrino masses: the see-saw mechanism with a RH neutrino at the GUT scale, radiatively generated neutrino masses, the neutrino mass arising from a 2nd Higgs doublet having a tiny VEV and coupling only to the neutrinos, and finally the EW-scale $\nu_R$ model.This last framework includes new quarks and leptons of opposite chirality at the electroweak scale (for the same SM gauge symmetry $SU(2)_W \times U(1)_Y$) compared to the SM.This model satisfies the EW precision tests and upon introducing an extra Higgs doublet the constraint coming from the 125-GeV scalar. Since in this model, the mirror fermions are required to be in the EW scale, these can be produced at the LHC giving final states with a very low background from the SM. One such final state is the samesign dileptons with large missing $p_T$ for the events. We explore the constraint provided by the $8$ TeV LHC and prospect of observing this signal in the $13$ TeV. Additional signals will be the presence of displaced vertices depending on the smallness of the Yukawa couplings of the mirror leptons with the ordinary leptons and the singlet Higgs present in the scenario. Of particular importance is also the production of the RH neutrinos at collider energies. [Preview Abstract] |
Sunday, January 29, 2017 4:42PM - 4:54PM |
M9.00007: Monte Carlo Simulations for Likelihood Analysis of the PEN experiment Charles Glaser The PEN collaboration performed a precision measurement of the $\pi^+\rightarrow e^+\nu_e(\gamma)$ branching ratio with the goal of obtaining a relative uncertainty of $5\times10^{-4}$ or better at the Paul Scherrer Institute. A precision measurement of the branching ratio $\Gamma(\pi\rightarrow e\bar{\nu}(\gamma))/\Gamma(\pi\rightarrow \mu \bar{\nu}(\gamma))$ can be used to give mass bounds on ``new'', or non V$-$A, particles and interactions. This ratio also proves to be one of the most sensitive tests for lepton universality. The PEN detector consists of beam counters, an active target, a mini-time projection chamber, multi-wire proportional chamber, a plastic scintillating hodoscope, and a CsI electromagnetic calorimeter. The Geant4 Monte Carlo simulation is used to construct ultra-realistic events by digitizing energies and times, creating synthetic target waveforms, and fully accounting for photo-electron statistics. We focus on the detailed detector response to specific decay and background processes in order to sharpen the discrimination between them in the data analysis. [Preview Abstract] |
Sunday, January 29, 2017 4:54PM - 5:06PM |
M9.00008: Properties of Angular Distributions in Drell-Yan Dilepton Production R. Evan McClellan, Jen-Chieh Peng, Wen-Chen Chang, Oleg Teryaev We present a simple geometric model of the Drell-Yan process based on the unobserved 'natural axis' (quark-anti-quark axis) in the dilepton rest frame. We utilize this model to interpret the recent high-precision Z-boson "Drell-Yan" angular distributions data from CMS. We find good agreement with the pT-dependence of the angular parameters, and extract the relative contributions from the quark-anti-quark and quark-gluon subprocesses, as well as the average degree of 'non-coplanarity' between the quark axis and the hadron plane. We interpret the non-coplanarity as a result of higher-order QCD contributions, and as the cause of the observed Lam-Tung violation. [Preview Abstract] |
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