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Armen Tumasyan

Bio: Armen Tumasyan is an academic researcher from Yerevan Physics Institute. The author has contributed to research in topics: Large Hadron Collider & Lepton. The author has an hindex of 128, co-authored 1189 publications receiving 79408 citations. Previous affiliations of Armen Tumasyan include CERN & Austrian Academy of Sciences.


Papers
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Journal ArticleDOI
TL;DR: In this article, a search for supersymmetric partners of the top quark, top squarks, was presented based on proton-proton collision events containing multiple jets, no leptons, and large transverse momentum imbalance.
Abstract: A search for production of the supersymmetric partners of the top quark, top squarks, is presented. The search is based on proton-proton collision events containing multiple jets, no leptons, and large transverse momentum imbalance. The data were collected with the CMS detector at the CERN LHC at a center-of-mass energy of 13 TeV, and correspond to an integrated luminosity of 137 fb - 1 . The targeted signal production scenarios are direct and gluino-mediated top squark production, including scenarios in which the top squark and neutralino masses are nearly degenerate. The search utilizes novel algorithms based on deep neural networks that identify hadronically decaying top quarks and W bosons, which are expected in many of the targeted signal models. No statistically significant excess of events is observed relative to the expectation from the standard model, and limits on the top squark production cross section are obtained in the context of simplified supersymmetric models for various production and decay modes. Exclusion limits as high as 1310 GeV are established at the 95% confidence level on the mass of the top squark for direct top squark production models, and as high as 2260 GeV on the mass of the gluino for gluino-mediated top squark production models. These results represent a significant improvement over the results of previous searches for supersymmetry by CMS in the same final state.

21 citations

Journal ArticleDOI
Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam, Federico Ambrogi  +2318 moreInstitutions (170)
TL;DR: A measurement of the production cross section of top quark pairs in association with two b jets is presented in this article, where data collected in proton-proton collisions at s=13TeV by the CMS detector at the LHC corresponding to an integrated luminosity of 35.9

21 citations

01 Nov 2012
TL;DR: A measurement of the forward-backward asymmetry (AFBAFB) of Drell-Yan lepton pairs in pp collisions at View the MathML sources=7 TeV is presented in this article.
Abstract: A measurement of the forward–backward asymmetry (AFBAFB) of Drell–Yan lepton pairs in pp collisions at View the MathML sources=7 TeV is presented. The data sample, collected with the CMS detector, corresponds to an integrated luminosity of 5 fb−15 fb−1. The asymmetry is measured as a function of dilepton mass and rapidity in the dielectron and dimuon channels. Combined results from the two channels are presented, and are compared with the standard model predictions. The AFBAFB measurement in the dimuon channel and the combination of the two channels are the first such results obtained at a hadron collider. The measured asymmetries are consistent with the standard model predictions.

21 citations

Journal ArticleDOI
TL;DR: In this paper, the authors have received support from the Marie-Curie program and the European Research Council and EPLANET (European Union); the Programa Clarin-COFUND del Principado de Asturias (PCLF); and FEDER (Spain).
Abstract: SEIDI, CPAN, PCTI and FEDER (Spain). Individuals have received support from the Marie-Curie program and the European Research Council and EPLANET (European Union); the Programa Clarin-COFUND del Principado de Asturias (...)

21 citations

Journal ArticleDOI
TL;DR: In this article, a measurement of the tt− production cross section (σtt−) in proton-proton collisions at a centre-of-mass energy of 7 TeV, in the all-jet final state that contains at least six jets, two of which are tagged as originating from b quarks.
Abstract: A measurement is presented of the tt− production cross section (σtt−) in proton-proton collisions at a centre-of-mass energy of 7 TeV, in the all-jet final state that contains at least six jets, two of which are tagged as originating from b quarks. The data correspond to an integrated luminosity of 3.54 fb−1, collected with the CMS detector at the LHC. The cross section is determined through an unbinned maximum likelihood fit of background and tt− signal to the reconstructed mass spectrum of tt− candidates in the data, in which events are subjected to a kinematic fit assuming a tt−→W+bW−b−→6 jets hypothesis. The measurement yields σtt−=139±10(stat.)±26(syst.)±3(lum.)pb , a result consistent with those obtained in other tt− decay channels, as well as with predictions of the standard model.

21 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal ArticleDOI
Georges Aad1, T. Abajyan2, Brad Abbott3, Jalal Abdallah4  +2964 moreInstitutions (200)
TL;DR: In this article, a search for the Standard Model Higgs boson in proton-proton collisions with the ATLAS detector at the LHC is presented, which has a significance of 5.9 standard deviations, corresponding to a background fluctuation probability of 1.7×10−9.

9,282 citations

Journal ArticleDOI
TL;DR: In this paper, results from searches for the standard model Higgs boson in proton-proton collisions at 7 and 8 TeV in the CMS experiment at the LHC, using data samples corresponding to integrated luminosities of up to 5.8 standard deviations.

8,857 citations

Journal ArticleDOI
TL;DR: MadGraph5 aMC@NLO as discussed by the authors is a computer program capable of handling all these computations, including parton-level fixed order, shower-matched, merged, in a unified framework whose defining features are flexibility, high level of parallelisation and human intervention limited to input physics quantities.
Abstract: We discuss the theoretical bases that underpin the automation of the computations of tree-level and next-to-leading order cross sections, of their matching to parton shower simulations, and of the merging of matched samples that differ by light-parton multiplicities. We present a computer program, MadGraph5 aMC@NLO, capable of handling all these computations — parton-level fixed order, shower-matched, merged — in a unified framework whose defining features are flexibility, high level of parallelisation, and human intervention limited to input physics quantities. We demonstrate the potential of the program by presenting selected phenomenological applications relevant to the LHC and to a 1-TeV e + e − collider. While next-to-leading order results are restricted to QCD corrections to SM processes in the first public version, we show that from the user viewpoint no changes have to be expected in the case of corrections due to any given renormalisable Lagrangian, and that the implementation of these are well under way.

6,509 citations