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.

Measurement of the λb0 lifetime in pp collisions at √s=7 TeV

Abstract: A measurement of the Lambda(b)0 lifetime using the decay Lambda(b)0 to J/Psi Lambda in proton-proton collisions at sqrt(s)=7 TeV is presented. The data set, corresponding to an integrated luminosity of about 5 inverse femtobarns, was recorded with the CMS experiment at the Large Hadron Collider using triggers that selected dimuon events in the J/Psi mass region. The Lambda(b)0 lifetime is measured to be 1.503 +/- 0.052 (stat.) +/- 0.031 (syst.) ps.

Search for dark matter produced in association with a Higgs boson decaying to a pair of bottom quarks in proton–proton collisions at √s=13Te

Abstract: A search for dark matter produced in association with a Higgs boson decaying to a pair of bottom quarks is performed in proton–proton collisions at a center-of-mass energy of 13 $\,\text {Te}\text {V}$ collected with the CMS detector at the LHC. The analyzed data sample corresponds to an integrated luminosity of 35.9 $\,\text {fb}^{-1}$ . The signal is characterized by a large missing transverse momentum recoiling against a bottom quark–antiquark system that has a large Lorentz boost. The number of events observed in the data is consistent with the standard model background prediction. Results are interpreted in terms of limits both on parameters of the type-2 two-Higgs doublet model extended by an additional light pseudoscalar boson $\mathrm {a}$ (2HDM+ $\mathrm {a}$ ) and on parameters of a baryonic $\mathrm {Z}'$ simplified model. The 2HDM+ $\mathrm {a}$ model is tested experimentally for the first time. For the baryonic $\mathrm {Z}'$ model, the presented results constitute the most stringent constraints to date.

I and i

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 …

The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations

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.