403 research outputs found

    Searches for the associated ttˉHt\bar{t}H production at CMS

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    After the recent discovery of the Higgs boson, the next important goal is to measure its properties. Probing the Yukawa coupling of the Higgs boson to top quarks is a particularly important test of physics beyond the standard model. This coupling can be experimentally accessed by measuring the cross section of the Higgs boson production in association with a top quark pair (ttˉHt\bar{t}H). The talk gives an overview of CMS results on ttˉHt\bar{t}H searches, using the full dataset of pp-collision data collected at the centre of mass energies of 7 and 8 TeV. All relevant Higgs boson decay modes have been studied, including Higgs decays to b-quarks, photons, τ\tau-leptons and multi-lepton final states. Additionally, the first Matrix Element Method based analysis has been carried out, that aims to further increase the sensitivity to the signal.Comment: Proceedings of the 8th International Workshop on the CKM Unitarity Triangle (CKM 2014), Vienna, Austria, September 8-12, 201

    Tartu Ülikooli karjÀÀripĂ€ev

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    W → Ï„Îœ ristlĂ”ike mÔÔtmine ja τ-leptoniteks laguneva topeltlaetud Higgsi bosoni otsimine CMSi eksperimendis

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    VĂ€itekirja elektrooniline versioon ei sisalda publikatsioone.Elementaarosakeste standardmudel kirjeldab hetkel teadaolevat fundamentaalfĂŒĂŒsikat ning on viimaste aastakĂŒmnete jooksul leidnud rohket eksperimentaalset kinnitust. Samas on pĂ”hjust arvata, et standardmudel ei ole fundamentaalne alusteooria, vaid pigem jÀÀnuk ĂŒldisemast fĂŒĂŒsikast, mis avaldub kĂ”rgematel energiatel. Üheks kindlaks viiteks standardmudeli-jĂ€rgse fĂŒĂŒsika kohta on neutriinode nullist erinevad massid, mis on vĂ”rreldes teiste standardmudeli osakeste massidega vĂ€ga vĂ€ikesed. LHC (Large Hadron Collider) on maailma suurim elementaarosakeste kiirendi, mis töötab kĂ”rgemal energial kui ĂŒkski varasem eksperiment. LHC kiirendi ĂŒldisteks eesmaĂ€rkideks on nii uue fĂŒĂŒsika ja Higgsi bosoni otsimine kui ka standardmudeli protsesside uurimine ja tĂ€ppismÔÔtmised. Kiirendi paikneb 27 km. pikkuses ringikujulises tunnelis, mis koosneb magnetitest, milles ringlevad kaks vastassuunalist prootonkiirt. Prootonite interaktsioonipunktides paiknevad osakeste-detektorid, kus toimub pĂ”rgete edasine analĂŒĂŒs. KĂ€esolevas doktoritöös kirjeldatud analĂŒĂŒsid on teostatud CMS (Compact Muon Solenoid) detektori poolt kogutud andmetega. W-bosoni ristloĂ”ike mÔÔtmine τ-leptoni ja neutriino lagunemiskanalis on ĂŒks teadaolevatest standardmudeli protsessidest. τ-leptoniteks laguneva topeltlaetud Higgsi bosoni otsimine baseerub uuel fĂŒĂŒsikateoorial, mis ĂŒritab seletada neutriinode vĂ€ikseid, kuid nullist erinevaid masse. AnalĂŒĂŒsitud eksperimentaalsed andmed on standardmudeliga kooskoĂ”las: mÔÔdetud W-bosoni ristloĂ”ige vastab teoorias arvutatud vÀÀrtusele ning topeltlaetud Higgsi bosoni vĂ”imaliku signaali otsing annab uue massi alampiiri, mis parandab oluliselt eelmist Tevatroni kiirendis saadud tulemust.The standard model of particle physics describes known matter and fundamental interactions and has been experimentally verified to a great level of accuracy. However, it is generally believed that the SM is not a complete theory, but needs to be extended. One of the clear indications of physics beyond the standard model are nonzero neutrino masses, that are extremely small in comparison to the masses of other particles. The Large Hadron Collider (LHC) is the worlds largest particle collider that works at higher energies than ever achieved in previous experiments and tries to find answers to the most fundamental questions in modern physics like the origin of mass, dark matter or nonzero neutrino masses. The LHC is situated in the 27 km long circular tunnel and is composed of a ring of magnets that store two counter-rotating proton beams. The proton collisions are measured and further analyzed by several particle detectors that are situated at the collision points of the proton beams. The data collected by one of the large general-purpose experiments – Compact Muon Solenoid (CMS) – were used in the two analyses that are summarized in this thesis. Firstly, the measurement of the cross section of a W- boson decaying to a τ-lepton and a neutrino, is one of the known standard model processes. The measurement confirms the standard model and is a contribution to τ-lepton physics in CMS. The search for a doubly charged Higgs boson that decays to τ-leptons tests new beyond the standard model physical theory, that is related to the neutrino mass generation mechanism. Analyzed data was found to be in good agreement with the standard model prediction and a new lower bound on the doubly charged Higgs boson mass was set, which considerably improves the previous measurements

    NĂ€gemispuudega inimeste meediatarbimine

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    If a human being gets 75% of information by sight (Vibur 2005), it does not mean that visually impaired people, who use primarily hearing for getting information, that they prefer only radio, which is the only audio channel, because nowadays technology gives a possibility to transfer visual texts into audio form. For example blind people can listen to the news and books by synthetic speech and screen magnification. They can also read books and newspapers from audio files, like from cassettes and CD-s. And in the future there should be only CD-s. Thesis „The Media Use of Visually Impaired People” shows that visually impaired people can use every media channel, if it is converted into suitable form. The choice of channels depends first of all on the people themselves. Next they choose the useful aids, from magnifying glass and television-spectacles till the computer with Braille’ screen. The choice of the aids depends on the rate of disability, and also on activity, interest and the skills of a human being. For example most of the visually impaired people does not know Braille’ and that is why they do not need the aids, which help them to read and write in Braille’ system. And so there is no need for printing Braille’ books, which is the reason why the number of books are decreasing. The ability to read and write in Braille’ system decrease despite of the fact that this system and the inventor of this style Louis Braille is very famous in the history of blind people and even there had been celebrations of the Braille’ day in Estonia in last years. Reading the books is very popular, even though not in Braille’, because sound writing makes much easier to reach different information. Most of audio books and audio journalism (which mostly concerns the life of visually impaired people) are made in the Library of Estonian Blind People. The range of the editions is much smaller compared with the state library, but it is still very important place for mediating information between visually impaired people. If most of the visually impaired people are unemployed, they have plenty of spare time to read books. Most of all they read fiction. In thesis I divided visually impaired people to partially sighted and blind people. On the assumption of empirical part of thesis or to say for the media analyse of visually impaired people I divided them into three groups: partially sighted, people who had lost their sight in later life and people born blind. For analyse I interviewed the medium group – nine people who had lost their sight in later life. In addition I interviewed six experts to explain the media use of visually impaired people. In sampling there were many young people, that is why it appeared that nowadays internet as a medium plays enormous role and the messages of it are used very often. But there is a problem with different media messages of internet, so that getting information is quite complicated for blind people, because there is a lot of odd information on the websites. Despite of the difficulties in websites you can get higher education only when you have computer and internet connection. In summary if visually impaired people have an opportunity and facilities to use all media channels, it gives them equal opportunities to take part in social life. This helps them to integrate in the community, which gives so stronger basis of the development of the society

    Ühe idiolekti analĂŒĂŒs: Ćœenja Fokini keelekasutus

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    Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV

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    Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

    Juxtaposing BTE and ATE – on the role of the European insurance industry in funding civil litigation