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Browsing by Author "Lesiak, Tadeusz"

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    Higgs physics at the CLIC electron–positron linear collider
    (The European Physical Journal C, 2017) Daniluk, Witold; Krupa, Beata; Kucharczyk, Marcin; Lesiak, Tadeusz; Moszczyński, Arkadiusz; Pawlik, Bogdan; Sopicki, Paweł; Wojtoń, Tomasz; Zawiejski, Leszek
    The Compact Linear Collider (CLIC) is an option for a future e+e− collider operating at centre-of-mass energies up to 3 TeV, providing sensitivity to a wide range of new physics phenomena and precision physics measurements at the energy frontier. This paper is the first comprehensive presentation of the Higgs physics reach of CLIC operating at three energy stages: √s = 350 GeV, 1.4 and 3 TeV. The initial stage of operation allows the study of Higgs boson production in Higgsstrahlung (e+e− → ZH) and WW-fusion (e+e− → Hνe ¯νe), resulting in precise measurements of the production cross sections, the Higgs total decay width ΓH, and model-independent determinations of the Higgs couplings. Operation at √s > 1 TeV provides high-statistics samples of Higgs bosons produced through WW-fusion, enabling tight constraints on the Higgs boson couplings. Studies of the rarer processes e+e− → t¯tH and e+e− → HHνe ¯νe allow measurements of the top Yukawa coupling and the Higgs boson self-coupling. This paper presents detailed studies of the precision achievable with Higgs measurements at CLIC and describes the interpretation of these measurements in a global fit.
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    Poszukiwanie łamania liczby barionowej i leptonowej w rozpadach ciężkich barionów oraz badanie tła dla poszukiwań długożyciowych cząstek egzotycznych
    (2016-06) Rachwał, Bartłomiej; Lesiak, Tadeusz; Kucharczyk, Marcin; Ciborowski, Jacek; Płaczek, Wiesław
    The thesis describes searches for baryon and lepton number violation in X b → K−µ + (X b = Λ b , Ξ 0 b ) decays. The study is performed in the LHCb experiment using data sample corresponding to an integrated luminosity of 3.0 fb− 1 of proton-proton collisions at the centre-of-mass energy of 7 TeV (8 TeV), collected in 2011 (2012), respectively. No statistically significant signal of the decays in question has been found. As a result, the upper limits have been set: B (Λ b → K−µ + ) < 3.6 × 10− 9 and B (Ξ 0 b → K−µ + ) < 1.8 × 10− 8 at the 95% confidence level. The second part of the thesis presents the background studies for exotic searches. The measurement of σ(bb) and σ(cc) production cross-sections with b − (c − ) hadron inclusive final states has been performed with data collected by the LHCb experiment in 2010 in proton-proton collisions at the centre-of- mass energy of 7 TeV. The author of this thesis has prepared the interface to the Next-To-Leading-Order POWHEG simulation framework into the LHCb software chain. All the kinematic characteristics of the hadron production in proton-proton collisions have been studied. The resulting angular and momentum correlations indicate a possible contribution from other mechanisms of bb production than the flavour creation, mainly the gluon splitting.
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    Report on Research Activities 2017-2020
    (Institute of Nuclear Physics Polish Academy of Sciences, 2021-05) Maj, Adam; Fornal, Bogdan; Grębosz, Jerzy; Horzela, Andrzej; Kopeć, Renata; Kwiatek, Wojciech; Lesiak, Tadeusz; Olko, Paweł; Skrzypek, Maciej; Świerblewska, Iwona; Świerblewski, Jacek; Wilczyński, Henryk; Zieliński, Piotr
    The "Report on Research Activities 2017-2020" summarizes the most important highlights of the scientific activities at IFJ PAN in the last four years. These highlights encompass activities in both fundamental and application research. Studies concerning basic research were carried out at the Division of Particle Physics and Astrophysics, the Division of Nuclear Physics and Strong Interactions, the Division of Condensed Matter Physics and at the Division of Theoretical Physics. In turn, the works related to scientific applications were conducted at the Division of Interdisciplinary Research and the Division of Applications of Physics. Of particular importance is the Cyclotron Centre Bronowice (CCB), which is a spectacular demonstration of the strong connection between basic research and applications. Reported is also information about the Krakow School of Interdisciplinary PhD Studies (KISD) which is coordinated by IFJ PAN, about the division of the construction of scientific equipment and infrastructure (DAI), about accredited laboratories, as well as about the outreach activity which has been carried out with great vigor. We invite the Reader of the Report to learn about all of the main research achievements of our Institute in recent years.
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    Search for Charged Lepton Flavour Violation at LHCb experiment
    (Institute of Nuclear Physics Polish Academy of Sciences, 2015) Chrząszcz, Marcin; Lesiak, Tadeusz; Lusiani, Alberto; Ciborowski, Jacek; Muryn, Bogdan
    The thesis describes searches for charged lepton flavour violation in the process τ−→ μ−μ+μ−. The study is performed at the LHCb experiment data sample corresponding to an integrated luminosity of 3 fb-1 of proton-proton collisions at a centre-of-mass energy of 7 TeV (8 TeV), collected in 2011 (2012), respectively. No significantly statistical signal of the decay in question has been found and as a result the upper limit was set: B(τ−→μ−μ+μ−) < 4.6 × 10 − 8 at 90% confidence level. The limit was then interpreted in terms of an effective field theory approach including beyond the Standard Model operators with different lepton chirality structures. We found that the limits are within the range: (4.1−6.8)×10−8 at 90% confidence level. The thesis presents also the combination of upper limits for all lepton flavour violating τ lepton decays. For the decay in question, i.e. τ−→μ−μ+μ−, the combination leads to the upper limit of B(τ−→μ−μ+μ−) < 1:2 ×10−8 at 90% confidence level.
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    Studies of the opto-electronic chain for the LHCb RICH upgrade
    (Institute of Nuclear Physics Polish Academy of Sciences, 2021) Ślazyk, Igor; Lesiak, Tadeusz; Calabrese, Roberto; Dziurda, Agnieszka; Turała, Michał; Nuzzo, Salvatore Vitale
    Niniejsza praca opisuje szczegółowo testy jakości fotodetektorów i związanej z nimi elektroniki (tzw. komórek podstawowych) dla modernizacji detektorów promieniowania Czerenkowa RICH (ang. Ring-Imaging Cherenkov), wchodzącego w skład spektrometru LHCb, dokonanych w Uniwersytecie w Ferrarze. Celem pracy jest szczegółowe omówienie kompletnego procesu kontroli jakości, od rozwoju zestawu pomiarowego przeznaczonego do testów wraz z jego oprogramowaniem służącym do akwizycji i analizy danych pomiarowych, aż do opisu samych pomiarów dokonanych na komórkach elementarnych i ich rezultatów
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    Studies of time dependent CP violation in charm decays of B 0 s mesons
    (Institute of Nuclear Physics Polish Academy of Sciences, 2015) Dziurda, Agnieszka; Lesiak, Tadeusz; Gligorov, Vladimir Vava; Ciborowski, Jacek; Muryn, Bogdan
    The thesis describes the world-first, time-dependent measurement of charge-parity (CP ) violation in B 0 s → D∓ s K± decays. The study is performed at the LHCb experiment using data sample corresponding to an integrated luminosity of 1.0 fb− 1 of proton-proton collisions at a center-of-mass energy of √ s = 7 TeV, recorded in 2011. The CP violating observables are found to be: C = 0.52 ± 0.25 ± 0.04, D f = 0.29 ± 0.42 ± 0.17, D ¯ f = 0.14 ± 0.41 ± 0.18, S f = − 0.90 ± 0.31 ± 0.06, S ¯ f = − 0.36 ± 0.34 ± 0.06, where the first (second) uncertainty is statistical (systematic). These observables are used to perform the first measurement of the Cabibbo-Kobayashi-Maskawa angle γ in B 0 s → D∓ s K± decays, finding γ = (113 +30 − 44 )◦ modulo 180◦ at 68% CL, where the error contains both statistical and systematic uncertainties.