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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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TL;DR: In this paper , a search for supersymmetry in events with two or three low-momentum leptons and missing transverse momentum is performed using proton-proton collisions at the LHC.
Abstract: A bstract A search for supersymmetry in events with two or three low-momentum leptons and missing transverse momentum is performed. The search uses proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV collected in the three-year period 2016–2018 by the CMS experiment at the LHC and corresponding to an integrated luminosity of up to 137 fb − 1 . The data are found to be in agreement with expectations from standard model processes. The results are interpreted in terms of electroweakino and top squark pair production with a small mass difference between the produced supersymmetric particles and the lightest neutralino. For the electroweakino interpretation, two simplified models are used, a wino-bino model and a higgsino model. Exclusion limits at 95% confidence level are set on $$ {\overset{\sim }{\upchi}}_2^0/{\overset{\sim }{\upchi}}_1^{\pm } $$ χ ~ 2 0 / χ ~ 1 ± masses up to 275 GeV for a mass difference of 10 GeV in the wino-bino case, and up to 205(150) GeV for a mass difference of 7.5 (3) GeV in the higgsino case. The results for the higgsino are further interpreted using a phenomenological minimal supersymmetric standard model, excluding the higgsino mass parameter μ up to 180 GeV with the bino mass parameter M 1 at 800 GeV. In the top squark interpretation, exclusion limits are set at top squark masses up to 540 GeV for four-body top squark decays and up to 480 GeV for chargino-mediated decays with a mass difference of 30 GeV.

14 citations

Journal ArticleDOI
Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam  +2314 moreInstitutions (190)
TL;DR: For instance, this article reported the following entities: BMWFW and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES and CSF (Bulgaria); MSIP and NRF (Republic of Korea); LAS (Lithuania); MOE and UM (Malaysia); BMBF, DAE and DST (India); IPM (Iran); SFI (Ireland); INFN======
Abstract: BMWFW and FWF (Austria); FNRS and FWO (Belgium); CNPq, CAPES, FAPERJ, and FAPESP (Brazil); MES (Bulgaria); CERN; CAS, MoST, and NSFC (China); COLCIENCIAS (Colombia); MSES and CSF (Croatia); RPF (Cyprus); SENESCYT (Ecuador); MoER, ERC IUT and ERDF (Estonia); Academy of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF (Germany); GSRT (Greece); OTKA and NIH (Hungary); DAE and DST (India); IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF (Republic of Korea); LAS (Lithuania); MOE and UM (Malaysia); BUAP, CINVESTAV, CONACYT, LNS, SEP, and UASLP-FAI (Mexico); MBIE (New Zealand); PAEC (Pakistan); MSHE and NSC (Poland); FCT (Portugal); JINR (Dubna); MON, RosAtom, RAS and RFBR (Russia); MESTD (Serbia); SEIDI and CPAN (Spain); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR and NSTDA (Thailand); TUBITAK and TAEK (Turkey); NASU and SFFR (Ukraine); STFC (United Kingdom); DOE and NSF (U.S.A.).

14 citations

Journal ArticleDOI
TL;DR: In this paper, the authors measured the lifetimes of the Hadron-proton collisions at the LHC in proton−proton collision at a luminosity of 19.7°C.
Abstract: Measurements are presented of the lifetimes of the $${\\mathrm {B}^0}$$B0, $$\\mathrm {B}^0_\\mathrm {s}$$Bs0, $$\\mathrm {\\Lambda }_\\mathrm {b} ^0$$Λb0, and $$\\mathrm {B}_\\mathrm {c}^+$$Bc+ hadrons using the decay channels $${\\mathrm {B}^0}\\!\\rightarrow \\! \\mathrm {J}/\\psi \\mathrm {K^{*}(892)}{}^{0}$$B0→J/ψK∗(892)0, $${\\mathrm {B}^0}\\!\\rightarrow \\! \\mathrm {J}/\\psi \\mathrm {K^0_S}$$B0→J/ψKS0, $$\\mathrm {B}^0_\\mathrm {s} \\!\\rightarrow \\! \\mathrm {J}/\\psi \\mathrm {\\pi ^+}\\mathrm {\\pi ^-}$$Bs0→J/ψπ+π-, $$\\mathrm {B}^0_\\mathrm {s} \\!\\rightarrow \\! \\mathrm {J}/\\psi \\mathrm {\\phi (1020)}$$Bs0→J/ψϕ(1020), $$\\varLambda _\\mathrm {b}^0\\!\\rightarrow \\!\\mathrm {J}/\\psi \\mathrm {\\Lambda }^{0}$$Λb0→J/ψΛ0, and $$\\mathrm {B}_\\mathrm {c}^+ \\!\\rightarrow \\!\\mathrm {J}/\\psi \\mathrm {\\pi ^+}$$Bc+→J/ψπ+. The data sample, corresponding to an integrated luminosity of 19.7$$\\,\\text {fb}^\\text {-1}$$fb-1, was collected by the CMS detector at the LHC in proton–proton collisions at $$\\sqrt{s}=8\\,\\text {Te}\\text {V} $$s=8TeV. The $${\\mathrm {B}^0}$$B0 lifetime is measured to be $$453.0 \\pm 1.6\\,\\text {(stat)} \\pm 1.8\\,\\text {(syst)} \\,\\upmu \\text {m} $$453.0±1.6(stat)±1.8(syst)μm in $$\\mathrm {J}/\\psi \\mathrm {K^{*}(892)}{}^{0}$$J/ψK∗(892)0and $$457.8 \\pm 2.7\\,\\text {(stat)} \\pm 2.8\\,\\text {(syst)} \\,\\upmu \\text {m} $$457.8±2.7(stat)±2.8(syst)μm in $$ \\mathrm {J}/\\psi \\mathrm {K^0_S}$$J/ψKS0, which results in a combined measurement of $$c\\tau _{{\\mathrm {B}^0}} = 454.1 \\pm 1.4\\,\\text {(stat)} \\pm 1.7\\,\\text {(syst)} \\,\\upmu \\text {m} $$cτB0=454.1±1.4(stat)±1.7(syst)μm. The effective lifetime of the $$\\mathrm {B}^0_\\mathrm {s}$$Bs0 meson is measured in two decay modes, with contributions from different amounts of the heavy and light eigenstates. This results in two different measured lifetimes: $$c\\tau _{\\mathrm {B}^0_\\mathrm {s} \\rightarrow \\mathrm {J}/\\psi \\mathrm {\\pi ^+}\\mathrm {\\pi ^-}} = 502.7 \\pm 10.2\\,\\text {(stat)} \\pm 3.4\\,\\text {(syst)} \\,\\upmu \\text {m} $$cτBs0→J/ψπ+π-=502.7±10.2(stat)±3.4(syst)μm and $$c\\tau _{\\mathrm {B}^0_\\mathrm {s} \\rightarrow \\mathrm {J}/\\psi \\mathrm {\\phi (1020)}} = 443.9 \\pm 2.0\\,\\text {(stat)} \\pm 1.5\\,\\text {(syst)} \\,\\upmu \\text {m} $$cτBs0→J/ψϕ(1020)=443.9±2.0(stat)±1.5(syst)μm. The $$\\mathrm {\\Lambda }_\\mathrm {b} ^0$$Λb0 lifetime is found to be $$442.9 \\pm 8.2\\,\\text {(stat)} \\pm 2.8\\,\\text {(syst)} \\,\\upmu \\text {m} $$442.9±8.2(stat)±2.8(syst)μm. The precision from each of these channels is as good as or better than previous measurements. The $$\\mathrm {B}_\\mathrm {c}^+$$Bc+ lifetime, measured with respect to the $${\\mathrm {B}^{+}}$$B+ to reduce the systematic uncertainty, is $$162.3 \\pm 7.8\\,\\text {(stat)} \\pm 4.2\\,\\text {(syst)} \\pm 0.1\\,(\\tau _{{\\mathrm {B}^{+}}})\\,\\upmu \\text {m} $$162.3±7.8(stat)±4.2(syst)±0.1(τB+)μm. All results are in agreement with current world-average values.

14 citations

Journal ArticleDOI
Vardan Khachatryan1, Albert M. Sirunyan1, Armen Tumasyan1, Wolfgang Adam  +2256 moreInstitutions (148)
TL;DR: In this article, a search for physics beyond the standard model in final states with at least three charged leptons, in any combination of electrons or muons, is reported.
Abstract: Results are reported from a search for physics beyond the standard model in final states with at least three charged leptons, in any combination of electrons or muons The data sample corresponds to an integrated luminosity of 23 fb^(−1) of proton–proton collisions at √s = 13 TeV, recorded by the CMS experiment at the LHC in 2015 Two jets are required in each event, providing good sensitivity to strong production of gluinos and squarks The search regions, sensitive to a range of different new physics scenarios, are defined using the number of jets tagged as originating from bottom quarks, the sum of the magnitudes of the transverse momenta of the jets, the imbalance in the overall transverse momentum in the event, and the invariant mass of opposite-sign, same-flavor lepton pairs The event yields observed in data are consistent with the expected background contributions from standard model processes These results are used to derive limits in terms of R-parity conserving simplified models of supersymmetry that describe strong production of gluinos and squarks Model-independent limits are presented to facilitate the reinterpretation of the results in a broad range of scenarios for physics beyond the standard model

14 citations

Journal ArticleDOI
Albert M. Sirunyan, Armen Tumasyan, Wolfgang Adam1, Ece Aşılar1  +2300 moreInstitutions (197)
TL;DR: In this paper, a search for a neutral spin-1 heavy resonance decaying to a top quark and a vector-like T quark in the all-hadronic final state is presented.
Abstract: A search is presented for massive spin-1 Z′ resonances decaying to a top quark and a heavy vector-like top quark partner T. The search is based on a 2.6 fb−1 sample of proton-proton collisions at 13 TeV collected with the CMS detector at the LHC. The analysis is optimized for final states in which the T quark decays to a W boson and a bottom quark. The focus is on all-jet final states in which both the W boson and the top quark decay into quarks that evolve into jets. The decay products of the top quark and of the W boson are assumed to be highly Lorentz-boosted and cannot be reconstructed as separate jets, but are instead reconstructed as merged, wide jets. Techniques for the identification of jet substructure and jet flavour are used to distinguish signal from background events. Several models for Z′ bosons decaying to T quarks are excluded at 95% confidence level, with upper limits on the cross section ranging from 0.13 to 10 pb, depending on the chosen hypotheses. This is the first search for a neutral spin-1 heavy resonance decaying to a top quark and a vector-like T quark in the all-hadronic final state.

14 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