1,787 research outputs found

    Search for Heavy Resonances Decaying to Taus in 7 TeV Proton-Proton Collisions at the Large Hadron Collider

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    Over the last few decades, the Standard Model (SM) of particle physics has been used as a means of understanding the world around us. However, there is an increasing amount of data that suggests the SM of particle physics only describes nature up to energies of the electroweak scale. Extensions to the SM have been developed as a means of explaining experimental observation. If these extensions are indeed the correct mathematical descriptions of nature, the Large Hadron Collider (LHC), located at the European Center for Nuclear Research (CERN) near Geneva, Switzerland, is expected to produce new and exciting physics signatures that can shed light on the evolution of our universe since the early hypothesized Big Bang. Of particular interest are models that may lead to events with highly energetic tau lepton pairs. In this dissertation, focus is placed on a possible search for new heavy gauge bosons decaying to highly energetic tau pairs using a data sample corresponding to an integrated luminosity of 36 pb^-1 of proton-proton collisions at sqrt(s) = 7 TeV collected with the CMS detector at the CERN LHC. The number of observed events in the data is in good agreement with the predictions for SM background processes. In the context of the Sequential SM, a Z0 with mass less than 468 GeV/c^2 is excluded at 95 percent credibility level, exceeding the sensitivity by the Tevatron experiments at the Fermi National Accelerator Laboratory

    Quarkophobic W' for LHC searches

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    We consider a simplified model where a W' boson is added to the standard model with negligible couplings to quarks, but generic couplings to leptons and electroweak bosons. We study the implications of such a model for LHC searches. Consequently, we propose an LHC search through the vector boson fusion topology which would have sensitivity for such a new particle with the current proton-proton collisions's energy and available luminosity.Comment: FPCP 2022 proceeding

    Phenomenology at the LHC of composite particles from strongly interacting Standard Model fermions via four-fermion operators of NJL type

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    A new physics scenario shows that four-fermion operators of Nambu-Jona-Lasinio (NJL) type have a strong-coupling UV fixed point, where composite fermions FF (bosons Π\Pi) form as bound states of three (two) SM elementary fermions and they couple to their constituents via effective contact interactions at the composite scale ΛO\Lambda \approx {\cal O} (TeV). We present a phenomenological study to investigate such composite particles at the LHC by computing the production cross sections and decay widths of composite fermions in the context of the relevant experiments at the LHC with pppp collisions at s=13\sqrt{s}={\rm 13} TeV and s=14\sqrt{s}={\rm 14} TeV. Systematically examining all the different composite particles FF and the signatures with which they can manifest, we found a vast spectrum of composite particles FF that has not yet been explored at the LHC. Recasting the recent CMS results of the resonant channel ppe+Fe+eqqˉpp\rightarrow e^+F \rightarrow e^+e^- q\bar{q}', we find that the composite fermion mass mFm_F below 4.25 TeV is excluded for Λ\Lambda/mFm_F = 1. We further highlight the region of parameter space where this specific composite particle FF can appear using 3 ab1^{-1}, expected by the High-Luminosity LHC, computing 3 and 5 σ\sigma contour plots of its statistical significance.Comment: To appear in EPJC. This revised version expands the search for composite fermion F considering all its possible flavors and topologies and highlighting the signatures not yet investigated at LH

    Probing Compressed Bottom Squarks with Boosted Jets and Shape Analysis

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    A feasibility study is presented for the search of the lightest bottom squark (sbottom) in a compressed scenario, where its mass difference from the lightest neutralino is 5 GeV. Two separate studies are performed: (1)(1) final state containing two VBF-like tagging jets, missing transverse energy, and zero or one bb-tagged jet; and (2)(2) final state consisting of initial state radiation (ISR) jet, missing transverse energy, and at least one bb-tagged jet. An analysis of the shape of the missing transverse energy distribution for signal and background is performed in each case, leading to significant improvement over a cut and count analysis, especially after incorporating the consideration of systematics and pileup. The shape analysis in the VBF-like tagging jet study leads to a 3σ3\sigma exclusion potential of sbottoms with mass up to 530(462)530 \, (462) GeV for an integrated luminosity of 300300 fb1^{-1} at 14 TeV, with 5%5\% systematics and PU =0(50)= 0 \, (50).Comment: 5 pages, 4 figures. Discussions and references updated, reach for PU=50 case give

    Probing Compressed Top Squarks at the LHC at 14 TeV

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    A feasibility study is presented for the search of the lightest top squark in a compressed scenario, where its mass is approximately equal to the sum of the masses of the top quark and the lightest neutralino. The study is performed in the final state of two b-jets, one lepton, large missing energy, and two high-ETE_{\rm T} jets with large separation in pseudo-rapidity, in opposite hemispheres, and with large dijet mass. The LHC could discover compressed top squarks with mass up to approximately 340 GeV (390 GeV) with an integrated luminosity of 1000 ifb (3000 ifb).Comment: Version updated with major changes: (a) 3-body stop decay (to b+W+n1) analyzed for first time (b) systematics calculation and discussion significantly upgraded (c) new kinematic and mass reach plots for the 3-body decay scenario added (d) discussions clarified throughou

    Probing Compressed Sleptons at the LHC using Vector Boson Fusion Processes

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    The vector boson fusion (VBF) topology at the Large Hadron Collider at 14 TeV provides an opportunity to search for new physics. A feasibility study for the search of sleptons in a compressed mass spectra scenario is presented in the final state of two jets, one or two low pTp_{T} non-resonant leptons, and missing energy. The presence of the VBF tagged jets and missing energy are effective in reducing Standard Model backgrounds. Using smuon production with a mass difference between l~L\tilde{l}_{L} and χ~10\tilde{\chi}_{1}^0 of 5-15 GeV, the significance of observing the signal events is found to be \sim 3-6σ\sigma for ml~m_{\tilde{l}}=115-135 GeV, considering an integrated luminosity of 3000 fb1^{-1}.Comment: 6 pages, 1 figure, 3 tables; v3: Journal matched versio