995 research outputs found

    Architecture and Performance of the Upgraded CMS Calorimeter Trigger

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    S. Laurila on behalf of the CMS collaborationThe CMS Level-1 calorimeter trigger was completely upgraded before the start of the 2016 data-taking. The upgraded system ran successfully during Run 2 and will continue running throughout Run 3. Its novel time-multiplexed architecture is made possible by large FPGAs connected by fastoptical links, operating in MicroTCA chassis. We describe the architecture of the system and the hardware used to implement it. In particular, examples of advanced trigger algorithms enabled by the time-multiplexed design are discussed. Precise FPGA floorplanning allows placing all calorimeter trigger algorithms in a single board. The performance of the system is presented based on the 2016‚Äď2018 data taking of proton collisions at the LHC.Peer reviewe

    Energiankeräys ympäristöstä

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    Tämä kandidaatintyö on kirjallisuusselvitys eri tavoista kerätä energiaa ympäristön energiapotentiaaleista. Työssä käydään läpi neljä erilaista tapaa kerätä energiaa, energian kerääminen aineen mekaanisesta rasituksesta pietsosähköisen kalvon avulla, energian kerääminen radioaalloista, aurinkoenergian kerääminen ja energian kerääminen lämpötilagradientista. Tyypillisesti ympäristöstä kerätyn energian tehotiheys on huomattavasti pienempi verrattuna esimerkiksi akuista saatavan energian tehotiheyteen. Työn loppuosassa vertaillaan eri energiankeräystapoja keskenään ja pohditaan niiden sopivuutta erilaisiin käyttötarkoituksiin. Pietsosähköistä ilmiötä käydään läpi selittämällä ilmiön perusperiaatteet ja mekanismi. Pietsosähköisyyden vahvuuksia on kerätyn energian suhteellisen korkea tehotiheys, ja se on teknologiana pitkälleviety. Heikkouksia on ulostulon suuri vaihtelu, joka riippuu aktiivisuudesta. Energian keräämisessä radioaalloista käydään läpi ilmiön perustoimintaa, lähi- ja kaukokentän eroa ja ilmiön sovelluskohteita. Radioaalloista kerättävä energiamäärä on tyypillisesti pieni, mutta se on riittävä signaalin takaisinlähetykseen. Aurinkoenergian tapauksessa energiaa voidaan kerätä hyvin paljon, ja keräys skaalautuu suoraan keräimien pinta-alan suhteen. Heikkouksia aurinkoenergian keräämisellä on energian saatavuuden syklisyys. Työssä aurinkoenergian keräämisestä käydään läpi ilmiön teoriaa ja yleisempiä sovelluskohteita

    Search for Charged Higgs Bosons Decaying to a Tau Lepton and a Neutrino with the CMS Experiment

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    The Standard Model of particle physics is the most successful and precise theoretical description of fundamental physics. The discovery of the Higgs boson in 2012 by the ATLAS and CMS experiments at the LHC provided strong evidence for the Englert-Brout-Higgs-Guralnik-Hagen-Kibble mechanism, explaining how elementary particles gain their masses in the Standard Model. However, the Standard Model is known to be an incomplete description of the nature, as it cannot explain the origin of dark matter, neutrino masses or the observed matter‚Äďantimatter asymmetry. Therefore more general models with an extended Higgs sector are actively being studied. Models with at least two Higgs doublets predict the existence of electrically charged Higgs bosons. The observation of charged Higgs bosons would provide direct evidence for new physics and guide way towards a more comprehensive theory. In this thesis, a search is presented for charged Higgs bosons decaying into a tau lepton and a neutrino, based on proton-proton collision events recorded by the CMS experiment in 2016 at a center-of-mass energy of 13 TeV. The amount of data corresponds to an integrated luminosity of 35.9 inverse femtobarns. The search targets the hadronic final state with a hadronically decaying tau lepton, missing momentum due to neutrinos, and additional jets from an associated top quark decay. This analysis contains multiple methodological improvements with respect to the previous CMS results on the same search channel. The particle identification algorithms and selection criteria are optimized for good performance under challenging luminosity conditions. Categorization of events based on tau lepton helicity is used to enhance sensitivity. The background from events with jets misidentified as tau leptons is estimated from data, whereas the background from genuine-tau events is estimated from simulation. This thesis also presents a new version of the tau embedding method, which allows the estimation of the genuine-tau background using single-muon events. The transverse mass of the tau-neutrino system is reconstructed. As the data agree with the background-only hypothesis, upper limits are derived for the charged Higgs boson production rate. The search covers signal hypotheses from 80 GeV to 3 TeV, and for the first time in CMS, the hypotheses with the charged Higgs boson mass close to the top quark mass are scanned. For maximal signal sensitivity, the results are combined with those from the leptonic final states of the same search channel. The combined result is interpreted in the context of the Minimal Supersymmetric Standard Model.Hiukkasfysiikan standardimalli on toistaiseksi tarkin teoria perustavista luonnonlaeista. Higgsin bosonin havaitseminen vuonna 2012 LHC-t√∂rm√§yttimen ATLAS- ja CMS-koeasemilla tarjosi vahvaa n√§ytt√∂√§ niin sanotun Higgsin mekanismin puolesta. T√§m√§ mekanismi selitt√§√§, kuinka alkeishiukkasten massat syntyv√§t standardimallissa. Standardimalli ei kuitenkaan ole t√§ydellinen kuvaus luonnosta, sill√§ se ei selit√§ pime√§n aineen syntyper√§√§, neutriinojen massoja tai havaittua aineen ja antiaineen ep√§symmetriaa. Siksi yleisempi√§ malleja, joissa on useampia Higgsin kentti√§, tutkitaan tiiviisti. Mallit, joissa on v√§hint√§√§n kaksi Higgs-duplettikentt√§√§, ennustavat s√§hk√∂varauksellisten Higgsin bosonien olemassaolon. S√§hk√∂varauksellisten Higgsin bosonien havaitseminen tarjoaisi suoraa todistusaineistoa standardimallin ulkopuolisesta fysiikasta ja viitoittaisi tiet√§ kohti laajempaa teoriaa. T√§ss√§ v√§it√∂skirjassa etsit√§√§n s√§hk√∂varauksellisia Higgsin bosoneita, jotka hajoavat tau-leptoniksi ja neutriinoksi. Etsinn√§ss√§ analysoidaan CMS-koeaseman vuonna 2016 mittaamia 13 TeV:n massakeskipiste-energian protoni‚Äďprotoni-t√∂rm√§yksi√§. Datan m√§√§r√§ vastaa 35.9 k√§√§nteisen femtobarnin integroitua luminositeettia. T√§ht√§imess√§ on hadroninen lopputila, jossa tau-leptoni hajoaa hadronisesti, top-kvarkin hajoamisesta syntyy hadronisia hiukkasry√∂ppyj√§ (jettej√§) ja jossa neutriinot havaitaan ep√§suorasti mitattujen kohtisuorien liikem√§√§rien ep√§tasapainona. Ty√∂ss√§ k√§ytetyt analyysimenetelm√§t ovat kehittyneempi√§ verrattuna aiempiin CMS-kollaboraation tuloksiin samasta etsint√§kanavasta. Hiukkasten tunnistamiseen ja t√∂rm√§ystapahtumien valitsemiseen k√§ytetyt algoritmit on optimoitu korkean luminositeetin olosuhteisiin. Tilastollisessa analyysissa t√∂rm√§ystapahtumat kategorisoidaan tau-leptonin helisiteettiin perustuvalla menetelm√§ll√§. Taustatapahtumat, joissa jetti on virheellisesti tunnistettu tau-leptoniksi, arvioidaan datasta. Oikeita tau-leptoneita sis√§lt√§v√§t taustatapahtumat puolestaan arvioidaan simulaatiolla. T√§ss√§ v√§it√∂skirjassa esitell√§√§n my√∂s uusi versio menetelm√§st√§, jolla t√§m√§ tausta voidaan arvioida myoneja sis√§lt√§vist√§ t√∂rm√§ystapahtumista. Tilastollinen analyysi perustuu tau‚Äďneutriino-systeemin kohtisuoraan massaan, jonka avulla johdetaan yl√§raja s√§hk√∂varauksellisten Higgsin bosonien tuottotodenn√§k√∂isyydelle. Etsint√§ kattaa massa-alueen 80 GeV:n ja 3 TeV:n v√§lill√§. T√§m√§ on ensimm√§inen CMS-analyysi, jossa etsint√§√§n sis√§ltyy my√∂s massa-alue top-kvarkin massan l√§heisyydess√§. Tulokset yhdistet√§√§n saman etsint√§kanavan leptonisen lopputilan tuloksiin ja tulkitaan k√§ytt√§en minimaalista supersymmetrist√§ standardimallia

    Search for supersymmetry using Higgs boson to diphoton decays at s‚ąö = 13 TeV

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    A search for supersymmetry (SUSY) is presented where at least one Higgs boson is produced and decays to two photons in the decay chains of pair-produced SUSY particles. Two analysis strategies are pursued: one focused on strong SUSY production and the other focused on electroweak SUSY production. The presence of charged leptons, additional Higgs boson candidates, and various kinematic variables are used to categorize events into search regions that are sensitive to different SUSY scenarios. The results are based on data from proton-proton collisions at the Large Hadron Collider at a center-of-mass energy of 13 TeV collected by the CMS experiment, corresponding to an integrated luminosity of 77.5 fb‚ąí1. No statistically significant excess of events is observed relative to the standard model expectations. We exclude bottom squark pair production for bottom squark masses below 530 GeV and a lightest neutralino mass of 1 GeV; wino-like chargino-neutralino production in gauge-mediated SUSY breaking (GMSB) for chargino and neutralino masses below 235 GeV with a gravitino mass of 1 GeV; and higgsino-like chargino-neutralino production in GMSB, where the neutralino decays exclusively to a Higgs boson and a gravitino for neutralino masses below 290 GeV.Peer reviewe

    Angular analysis of the decay B+-> K*(892)(+)mu(+)mu(-) in proton-proton collisions at root s=8 TeV

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    Angular distributions of the decay B+-> K*(892)(+)mu(+)mu(-) are studied using events collected with the CMS detector in root s = 8 TeV proton-proton collisions at the LHC, corresponding to an integrated luminosity of 20.0 fb(-1). The forward-backward asymmetry of the muons and the longitudinal polarization of the K*(892)(+) meson are determined as a function of the square of the dimuon invariant mass. These are the first results from this exclusive decay mode and are in agreement with a standard model prediction.Peer reviewe

    Search for new particles in an extended Higgs sector with four b quarks in the final state at s=13TeV

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    Publisher Copyright: ¬© 2022 The Author(s)A search for a massive resonance X decaying to a pair of spin-0 bosons Ōē that themselves decay to pairs of bottom quarks, is presented. The analysis is restricted to the mass ranges mŌē from 25 to 100 GeV and mX from 1 to 3 TeV. For these mass ranges, the decay products of each Ōē boson are expected to merge into a single large-radius jet. Jet substructure and flavor identification techniques are used to identify these jets. The search is based on CERN LHC proton-proton collision data at s=13TeV, collected with the CMS detector in 2016‚Äď2018, corresponding to an integrated luminosity of 138fb‚ąí1. Model-specific limits, where the two new particles arise from an extended Higgs sector, are set on the product of the production cross section and branching fraction for X‚ÜíŌēŌē‚Üí(bb‚Äĺ)(bb‚Äĺ) as a function of the resonances' masses, where both the X‚ÜíŌēŌē and Ōē‚Üíbb‚Äĺ branching fractions are assumed to be 100%. These limits are the first of their kind on this process, ranging between 30 and 1 fb at 95% confidence level for the considered mass ranges.Peer reviewe

    Measurement of t(t)over-bar normalised multi-differential cross sections in pp collisions at root s=13 TeV, and simultaneous determination of the strong coupling strength, top quark pole mass, and parton distribution functions

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