Department of Physics & Astronomy

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Browsing Department of Physics & Astronomy by Author "Aalto University"

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    GAMMA-RAYS FROM THE QUASAR PKS 1441+25: STORY OF AN ESCAPE
    (IOP Publishing, 2015-12-15) VERITAS; SPOL; ASAS-SN; OVRO; NuSTAR; CRTS; Utah System of Higher Education; University of Utah; McGill University; Washington University (WUSTL); University of California System; University of California Los Angeles; Harvard University; Smithsonian Astrophysical Observatory; Smithsonian Institution; University College Dublin; University of California Santa Cruz; Iowa State University; University of Potsdam; Helmholtz Association; Deutsches Elektronen-Synchrotron (DESY); California State University System; California Polytechnic State University San Luis Obispo; Ollscoil na Gaillimhe-University of Galway; Yale University; Purdue University System; Purdue University; Purdue University West Lafayette Campus; University of Minnesota System; University of Minnesota Twin Cities; Columbia University; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; University of Delaware; University of Iowa; University System of Georgia; Georgia Institute of Technology; University of Chicago; National Aeronautics & Space Administration (NASA); NASA Goddard Space Flight Center; Cork Institute of Technology; University System of Maryland; University of Maryland College Park; United States Department of Energy (DOE); Argonne National Laboratory; University of Arizona; University System of Ohio; Ohio State University; University Diego Portales; Carnegie Institution for Science; Aalto University; National Radio Astronomy Observatory (NRAO); California Institute of Technology; Universidad de Concepcion; Stanford University; SLAC National Accelerator Laboratory; University of Alabama Tuscaloosa
    Outbursts from gamma-ray quasars provide insights on the relativistic jets of active galactic nuclei and constraints on the diffuse radiation fields that fill the universe. The detection of significant emission above 100 GeV from a distant quasar would show that some of the radiated gamma-rays escape pair-production interactions with low-energy photons, be it the extragalactic background light (EBL), or the radiation near the supermassive black hole lying at the jet's base. VERITAS detected gamma-ray emission up to similar to 200 GeV from PKS 1441+25 (z = 0.939) during 2015 April, a period of high activity across all wavelengths. This observation of PKS 1441+25 suggests that the emission region is located thousands of Schwarzschild radii away from the black hole. The gamma-ray detection also sets a stringent upper limit on the near-ultraviolet to near-infrared EBL intensity, suggesting that galaxy surveys have resolved most, if not all, of the sources of the EBL at these wavelengths.
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    Multiwavelength Observations of the Blazar BL Lacertae: A New Fast TeV Gamma-Ray Flare
    (IOP Publishing, 2018-03-28) VERITAS Collaboration; Utah System of Higher Education; University of Utah; Harvard University; Smithsonian Institution; University of California System; University of California Los Angeles; Iowa State University; University of Potsdam; Helmholtz Association; Deutsches Elektronen-Synchrotron (DESY); Washington University (WUSTL); Ollscoil na Gaillimhe-University of Galway; Purdue University System; Purdue University; Purdue University West Lafayette Campus; Tsinghua University; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; McGill University; Columbia University; University of Minnesota System; University of Minnesota Twin Cities; California State University System; California State University East Bay; University of California Santa Cruz; University of Delaware; University of Iowa; DePauw University; University College Dublin; University System of Georgia; Georgia Institute of Technology; University of Chicago; Cork Institute of Technology; University of Alabama Tuscaloosa; Boston University; Saint Petersburg State University; Russian Academy of Sciences; Russian Academy of Science Lebedev Physical Institute; Moscow Institute of Physics & Technology; Max Planck Society; Aalto University; Consejo Superior de Investigaciones Cientificas (CSIC); CSIC - Instituto de Astrofisica de Andalucia (IAA); California Institute of Technology; University of Turku; University of Arizona
    Combined with measurements made by very-long-baseline interferometry, the observations of fast TeV gamma-ray flares probe the structure and emission mechanism of blazar jets. However, only a handful of such flares have been detected to date, and only within the last few years have these flares been observed from lower-frequency-peaked BL. Lac objects and flat-spectrum radio quasars. We report on a fast TeV gamma-ray flare from the blazar BL. Lacertae observed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS). with a rise time of similar to 2.3 hr and a decay time of similar to 36 min. The peak flux above 200 GeV is (4.2 +/- 0.6) x 10(-6) photon m(-2) s(-1) measured with a 4-minute-binned light curve, corresponding to similar to 180% of the flux that is observed from the Crab Nebula above the same energy threshold. Variability contemporaneous with the TeV gamma-ray flare was observed in GeV gamma-ray, X-ray, and optical flux, as well as in optical and radio polarization. Additionally, a possible moving emission feature with superluminal apparent velocity was identified in Very Long Baseline Array observations at 43 GHz, potentially passing the radio core of the jet around the time of the gamma-ray flare. We discuss the constraints on the size, Lorentz factor, and location of the emitting region of the flare, and the interpretations with several theoretical models that invoke relativistic plasma passing stationary shocks.
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    Search for an exotic decay of the Higgs boson to a pair of light pseudoscalars in the final state with two bquarks and two tau leptons in proton-proton collisions at root s=13 TeV The CMS Collaboration
    (Elsevier, 2018) CMS Collaboration; Buccilli, A.; Cooper, S.I.; Henderson, C.; Rumerio, P.; West, C.; Yerevan Physics Institute; Belarusian State University; University of Antwerp; Vrije Universiteit Brussel; Ghent University; Centro Brasileiro de Pesquisas Fisicas; Universidade do Estado do Rio de Janeiro; Universidade Estadual Paulista; Universidade Federal do ABC (UFABC); Bulgarian Academy of Sciences; University of Sofia; Beihang University; Chinese Academy of Sciences; Institute of High Energy Physics, CAS; Peking University; Tsinghua University; Universidad de los Andes (Colombia); University of Split; Rudjer Boskovic Institute; University of Cyprus; Charles University Prague; Escuela Politecnica Nacional Ecuador; Egyptian Academy of Scientific Research & Technology (ASRT); Egyptian Knowledge Bank (EKB); Egyptian Network of High Energy Physics (ENHEP); National Institute of Chemical Physics & Biophysics (NICPB); University of Helsinki; Aalto University; Helsinki Institute of Physics; Lappeenranta University of Technology; CEA; UDICE-French Research Universities; Universite Paris Saclay; Centre National de la Recherche Scientifique (CNRS); CNRS - National Institute of Nuclear and Particle Physics (IN2P3); Institut Polytechnique de Paris; Universites de Strasbourg Etablissements Associes; Universite de Strasbourg; Universite Claude Bernard Lyon 1; Georgian Technical University; Ivane Javakhishvili Tbilisi State University; RWTH Aachen University; Helmholtz Association; Deutsches Elektronen-Synchrotron (DESY); University of Hamburg; Karlsruhe Institute of Technology; National Centre of Scientific Research "Demokritos"; National & Kapodistrian University of Athens; National Technical University of Athens; University of Ioannina; Eotvos Lorand University; Eotvos Lorand Research Network; Hungarian Academy of Sciences; Hungarian Wigner Research Centre for Physics; Hungarian Institute for Nuclear Research; University of Debrecen; Indian Institute of Science (IISC) - Bangalore; Homi Bhabha National Institute; National Institute of Science Education & Research (NISER); Panjab University; University of Delhi; Saha Institute of Nuclear Physics; Indian Institute of Technology System (IIT System); Indian Institute of Technology (IIT) - Madras; Bhabha Atomic Research Center (BARC); Tata Institute of Fundamental Research (TIFR); Indian Institute of Science Education & Research (IISER) Pune; University College Dublin; Istituto Nazionale di Fisica Nucleare (INFN); Universita degli Studi di Bari Aldo Moro; Politecnico di Bari; University of Bologna; University of Catania; University of Florence; University of Genoa; University of Milano-Bicocca; University of Naples Federico II; University of Basilicata; Guglielmo Marconi University; University of Padua; University of Trento; University of Pavia; University of Perugia; University of Pisa; Scuola Normale Superiore di Pisa; Sapienza University Rome; University of Turin; University of Eastern Piedmont Amedeo Avogadro; University of Trieste; Kyungpook National University; Chonnam National University; Hanyang University; Korea University; Sejong University; Seoul National University (SNU); University of Seoul; Sungkyunkwan University (SKKU); Vilnius University; Universiti Malaya; Universidad de Sonora; CINVESTAV - Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional; Instituto Politecnico Nacional - Mexico; Universidad Iberoamericana Ciudad de Mexico; Benemerita Universidad Autonoma de Puebla; Universidad Autonoma de San Luis Potosi; University of Auckland; University of Canterbury; National Centre for Physics - Pakistan; Quaid I Azam University; National Centre for Nuclear Research; University of Warsaw; Laboratorio de Instrumentacao e Fisica Experimental de Particulas; Joint Institute for Nuclear Research - Russia; National Research Centre - Kurchatov Institute; Petersburg Nuclear Physics Institute; Russian Academy of Sciences; Institute for Nuclear Research of the Russian Academy of Sciences; Alikhanov Institute for Theoretical & Experimental Physics; Moscow Institute of Physics & Technology; National Research Nuclear University MEPhI (Moscow Engineering Physics Institute); Russian Academy of Science Lebedev Physical Institute; Lomonosov Moscow State University; Novosibirsk State University; Institute of High Energy Physics - IHEP; Tomsk Polytechnic University; University of Belgrade; Centro de Investigaciones Energeticas, Medioambientales Tecnologicas; Autonomous University of Madrid; University of Oviedo; Consejo Superior de Investigaciones Cientificas (CSIC); Universidad de Cantabria; CSIC - Instituto de Fisica de Cantabria (IFCA); European Organization for Nuclear Research (CERN); Swiss Federal Institutes of Technology Domain; Paul Scherrer Institute; ETH Zurich; University of Zurich; National Central University; National Taiwan University; Chulalongkorn University; Cukurova University; Middle East Technical University; Bogazici University; Istanbul Technical University; National Academy of Sciences Ukraine; Institute for Scintillation Materials of the National Academy of Sciences of Ukraine; Kharkov Institute of Physics & Technology; University of Bristol; UK Research & Innovation (UKRI); Science & Technology Facilities Council (STFC); STFC Rutherford Appleton Laboratory; Imperial College London; Brunel University; Baylor University; Catholic University of America; University of Alabama Tuscaloosa; Boston University; Brown University; University of California System; University of California Davis; University of California Los Angeles; University of California Riverside; University of California San Diego; University of California Santa Barbara; California Institute of Technology; Carnegie Mellon University; University of Colorado System; University of Colorado Boulder; Cornell University; United States Department of Energy (DOE); University of Chicago; Fermi National Accelerator Laboratory; State University System of Florida; University of Florida; Florida International University; Florida State University; Florida Institute of Technology; University of Illinois System; University of Illinois Chicago; University of Iowa; Johns Hopkins University; University of Kansas; Kansas State University; Lawrence Livermore National Laboratory; University System of Maryland; University of Maryland College Park; Massachusetts Institute of Technology (MIT); University of Minnesota System; University of Minnesota Twin Cities; University of Mississippi; University of Nebraska System; University of Nebraska Lincoln; State University of New York (SUNY) System; State University of New York (SUNY) Buffalo; Northeastern University; Northwestern University; University of Notre Dame; University System of Ohio; Ohio State University; Princeton University; University of Puerto Rico; University of Puerto Rico Mayaguez; Purdue University System; Purdue University; Purdue University West Lafayette Campus; Rice University; University of Rochester; Rutgers State University New Brunswick; University of Tennessee System; University of Tennessee Knoxville; Texas A&M University System; Texas A&M University College Station; Texas Tech University System; Texas Tech University; Vanderbilt University; University of Virginia; Wayne State University; University of Wisconsin System; University of Wisconsin Madison; Technische Universitat Wien; Universidade Estadual de Campinas; Universidade Federal do Rio Grande do Sul; Universite Libre de Bruxelles; Cairo University; Helwan University; Zewail City of Science & Technology; King Abdulaziz University; Universite de Haute-Alsace (UHA); Brandenburg University of Technology Cottbus; Indian Institute of Technology (IIT) - Bhubaneswar; Institute of Physics Bhubaneswar (IOPB); Shoolini University; Visva Bharati University; Isfahan University of Technology; Islamic Azad University; University of Siena; International Islamic University Malaysia; Agensi Nuklear Malaysia; Warsaw University of Technology; Peter the Great St. Petersburg Polytechnic University; Budker Institute of Nuclear Physics; Riga Technical University; Adiyaman University; Istanbul Aydin University; Mersin University; Piri Reis University; Gaziosmanpasa University; Ozyegin University; Izmir Institute of Technology; Marmara University; Kafkas University; Istanbul Bilgi University; Hacettepe University; University of Southampton; Monash University; Karamanoglu Mehmetbey University; Utah System of Higher Education; Utah Valley University; Beykent University; Bingol University; Sinop University; Mimar Sinan Guzel Sanatlar University
    A search for an exotic decay of the Higgs boson to a pair of light pseudoscalar bosons is performed for the first time in the final state with two b quarks and two τ leptons. The search is motivated in the context of models of physics beyond the standard model (SM), such as two Higgs doublet models extended with a complex scalar singlet (2HDM + S), which include the next-to-minimal supersymmetric SM (NMSSM). The results are based on a data set of proton–proton collisions corresponding to an integrated luminosity of \(35.9\phantom{\rule{0.2em}{0ex}}{\text{fb}}^{-1}\), accumulated by the CMS experiment at the LHC in 2016 at a center-of-mass energy of \(13\phantom{\rule{0.2em}{0ex}}\text{TeV}\). Masses of the pseudoscalar boson between 15 and \(60\phantom{\rule{0.2em}{0ex}}\text{GeV}\) are probed, and no excess of events above the SM expectation is observed. Upper limits between 3 and 12% are set on the branching fraction \(B\left(h\to aa\to 2\tau 2b\right)\) assuming the SM production of the Higgs boson. Upper limits are also set on the branching fraction of the Higgs boson to two light pseudoscalar bosons in different 2HDM + S scenarios. Assuming the SM production cross section for the Higgs boson, the upper limit on this quantity is as low as 20% for a mass of the pseudoscalar of \(40\phantom{\rule{0.2em}{0ex}}\text{GeV}\) in the NMSSM.