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 G08: Standard Model and BSM PhysicsLive
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Chair: Sekhar Chivukula, UCSD |
Sunday, April 18, 2021 8:30AM - 8:42AM Live |
G08.00001: Search for four top quark production in the single-lepton final state with the CMS data Wenyu Zhang, Emanuele Usai, Sinan Sagir, Meenakshi Narain, Ulrich Heintz We present a search for the standard model four top quark (tttt) production in the single-lepton final state. We analyze the proton-proton collision data collected by the CMS experiment at center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 35.8 $fb^{-1}$ in 2016, 41.5 $fb^{-1}$ in 2017 and 59.97 $fb^{-1}$ in 2018. The single lepton final state features a high jet multiplicity, with at least four jets coming from the hadronization of a bottom quark, an electron or a muon, and missing transverse momentum from neutrino. We consider the distribution of the scalar sum of transverse momentum of all the jets (HT) to discriminate the signal from background and, in the absence of signal, set limits on the four tops production cross section. The expected limits and significances on tttt production cross section for data-taking period 2016 to 2018, and their combination are presented. In addition, we perform a multivariate analysis using Boosted Decision Tree (BDT)-based approach to optimize the discrimination between signal and background. Comparison between the HT-based analysis and BDT-based analysis will be discussed. [Preview Abstract] |
Sunday, April 18, 2021 8:42AM - 8:54AM Live |
G08.00002: Search for heavy fermionic partner of the top quark with charge 5/3 in the single leptonic channel using CMS Run 2 data Farrah Simpson With the discovery of the Higgs boson in 2012 by the CMS and ATLAS experiments, searches for new heavy particles have ensued in hope of solving the hierarchy problem. In this talk, I will be discussing the search for the X$_{\mathrm{5/3}}$, a strongly interacting fermionic partner of the top quark with charge $+$5/3. Left-handed and right-handed coupling of the X$_{\mathrm{5/3\thinspace }}$to W bosons are considered separately. The search is conducted using the CMS Run 2 datasets collected in 2017 and 2018. Data was collected with the CMS detector at a luminosity of 41.5 fb$^{\mathrm{-1}}$ and a center-of-mass energy of sqrt(s) $=$ 13 TeV. The search looks for events with pair production of an X$_{\mathrm{5/3\thinspace }}$and its antiparticle which subsequently decay to a top and W boson. To enhance signal separation, the search is constructed to only look for events where one W decays to a lepton and neutrino, while the other three W bosons decay hadronically. Limits on the cross section will be presented and compared to previous results. In addition, I will be discussing the preliminary findings from an additional theory interpretation for the search: events where the X$_{\mathrm{5/3\thinspace }}$and its antiparticle decay to a top quark and a charged Higgs boson. [Preview Abstract] |
Sunday, April 18, 2021 8:54AM - 9:06AM Live |
G08.00003: Differential Measurement of ZZjj Production with the Full ATLAS Run-2 Dataset Prajita Bhattarai The electroweak production of two Z bosons in association with two jets (ZZjj) was experimentally observed in ATLAS with the complete LHC Run 2 dataset in 2019. Electroweak production of ZZjj is sensitive to couplings between the Higgs boson and vector bosons (HVV) as well as triple and quartic gauge couplings. Within the Standard Model, interference between diagrams containing the HVV, triple, and quartic gauge couplings makes electroweak ZZjj production rare. Measurements in this topology are therefore highly-sensitive to possible contributions from new physics. This talk will motivate the differential ZZjj analysis within the fully leptonic final state, discuss some relevant analysis techniques such as unfolding and background estimation, and outline the prospects for probing beyond the Standard Model theories. [Preview Abstract] |
Sunday, April 18, 2021 9:06AM - 9:18AM Live |
G08.00004: Macroscopic Approach to Test Method for Improving Yukawa-Like Interaction Limits Thomas Bsaibes, Luis Pires, Ricardo Decca Yukawa-like interactions arise in many extensions to the standard model. These hypothetical interactions result in a force mediated by a new boson. The potential of a theorized Yukawa-like force between two point masses is $V(r)=-\alpha\frac{Gm_1m_2}{r}e^{-r/\lambda}$, where $G$ is Newton's gravitational constant, $r$ is the separation between the masses, $\alpha$ is the relative strength, and $\lambda$ is the characteristic length of the interaction. Many studies placed limits on $\alpha$ across a wide range of $\lambda$, however for $\lambda$ below 1 $\mu$m, the constraint set on $\alpha$ is poor. A previous study used a spherical test mass; a possible 100-fold improvement to the limit on $\alpha$ in the submicron regime of $\lambda$ may be achieved using a cylindrical test mass. A major challenge in using a cylinder is the alignment of the cylinder with respect to the planar source mass. A scaled up version of the experiment has been constructed to test if the capacitance between a cylinder and a plate can be used to determine the cylinder's alignment. Once the technique is refined it will be used to align a 500 $\mu$m cylinder with the planar source mass. This talk will cover the progress made towards using capacitance as an alignment indicator. [Preview Abstract] |
Sunday, April 18, 2021 9:18AM - 9:30AM Live |
G08.00005: First experimental search for production of magnetic monopoles via the Schwinger mechanism Aditya Upreti The Schwinger mechanism predicts the production of electron-positron pairs in presence of an extremely strong electric field via quantum-mechanical tunnelling. By the electromagnetic duality, if magnetic monopoles (MMs) exist, they would be produced by the same mechanism in sufficiently strong magnetic field. The Pb-Pb heavy ion collisions at the LHC produced the strongest magnetic fields in the known Universe. The first search for MM production via Schwinger mechanism was conducted by the MoEDAL experiment during the 2018 heavy ion run at the LHC, when its detectors were exposed to 0.237 nb$^{-1}$ of 5.2 TeV Pb-Pb collisions. In this talk, I plan to describe this search for MMs in heavy ion collisions. I will highlight the advantages of Schwinger mechanism over its previously considered counterparts, the Drell-Yan mechanism and the photon fusion mechanism, and provide an outlook of future searches that would expand sensitivity of MoEDAL detectors to higher magnetic charges. [Preview Abstract] |
Sunday, April 18, 2021 9:30AM - 9:42AM On Demand |
G08.00006: Calculations of Parton Distribution Functions with An Extension of the Standard Model Richard Holmes Calculations are performed for Parton Distribution Functions (PDFs) with an extension of the Standard Model that invokes permutational symmetry of the mass matrices. The resulting PDFs for valence quarks in baryons have a peak at a value of x\textasciitilde 0.2, in improved agreement with measured data over the conventional model which peaks at 1/3. Physically, this lower value is obtained because of the implied presence of trace probabilities of the higher-mass quark flavors in the extended theory, effectively creating 5 rather than 3 constituent quarks. [Preview Abstract] |
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