The results reported in this collective monography are mainly focused on the applied aspect significant for the development and construction of the International Linear Electron and Positron ...Collider. A greater deal of study was performed by the Belarusian scientists from the National Academy of Sciences and universities of the Republic of Belarus. In PTI NASB, a hydropercussion stamping technology was developed, some niobium resonator parts were manufactured, and copper, aluminum, and superconducting niobium Tesla-type resonators were constructed by the method of electron beam welding. In SPMRS NASB, an immersion-type helium cryostat was developed and manufactured to provide the full-scale microwave tests of resonators, and the superconducting characteristics of original niobium sheets were studied in the area of a weld joint to indicate only a 5% decrease in the critical transition temperature, superconducting transition width, and critical magnetic field. In INP BSU, a measuring technique was developed and a measuring complex was constructed for studying the microwave resonator parameters and, in cooperation with SPMRS NASB, the characteristics of superconducting niobium resonators (resonant frequency, loaded quality factor, standing wave ratio, relative level of losses at the central frequency) were investigated. This monography is designed for the scientists in the field of high-energy physics, the engineers specializing in the construction of accelerator systems, doctoral and postgraduate students, and undergraduates.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Participation of a Joint Institute for Nuclear Research (JINR) team in the research program at the Tevatron at Fermilab is described. In their work on the upgraded CDF Run II detector, the emphasis ...was placed on top quark physics. The JINR team was fully engaged in the data analysis of the CDF experiment, particularly, in measuring the top quark mass in the dilepton and lepton–jet modes, in measuring the top quark charge, and in searching for the Higgs boson. The JINR team made a decisive contribution to the operation of the scintillation counter subsystem of the CDF muon trigger, to the trigger based on the vertex silicon detector for selection of events with secondary vertices and to the preshower detector of the electromagnetic calorimeter. The team was involved in the construction, upgrading, and operation of the system of scintillation counters and developed a system for the online monitoring of their parameters to ensure their effective operation in Run II. The work of the JINR researchers was highly appreciated by the international CDF collaboration.
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The production of a $W$ boson in association with a single charm quark is studied using 140 fb–1 of $\sqrt{s}$ = $13$ $\mathrm{TeV}$ proton-proton collision data collected with the ATLAS detector at ...the Large Hadron Collider. The charm quark is tagged by the presence of a charmed hadron reconstructed with a secondary-vertex fit. The $W$ boson is reconstructed from the decay to either an electron or a muon and the missing transverse momentum present in the event. The charmed mesons reconstructed are D+ → K– π+ π+ and D*+ → D0 π+ → (K– π+) π+ and the charge conjugate decays in the fiducial regions where $p$T($e,μ$) > 30 GeV, |$η(e,μ)$| < 2.5, $p$T (D(*)) > 8 GeV, and |$η$(D(*))| < 2.2. The integrated and normalized differential cross sections as a function of the pseudorapidity of the lepton from the $W$ boson decay, and of the transverse momentum of the charmed hadron, are extracted from the data using a profile likelihood fit. The measured total fiducial cross sections are ${σ}_{fid}^{OS – SS}$ (W– + D+) = 50.2 ± 0.2 ${(stat)}_{–2.3}^{+2.4}$(syst) pb, ${σ}_{fid}^{OS – SS}$ (W+ + D–) = 48.5 ± 0.2 ${(stat)}_{–2.2}^{+2.3}$(syst) pb, ${σ}_{fid}^{OS – SS}$ (W– + D*+) = 51.1 ± 0.4 ${(stat)}_{–1.8}^{+1.9}$(syst) pb, ${σ}_{fid}^{OS – SS}$ (W+ + D*–) = 50.0 ± 0.4 ${(stat)}_{–1.8}^{+1.9}$(syst) pb. Results are compared with the predictions of next-to-leading-order quantum chromodynamics calculations performed using state-of-the-art parton distribution functions. Additionally, the ratio of charm to anticharm production cross sections is studied to probe the $s$-$\bar{s}$ quark asymmetry. The ratio is found to be ${R}_{c}^{±}$= 0.971 ± 0.006 (stat) ± 0.011 (syst). The ratio and cross-section measurements are consistent with the predictions obtained with parton distribution function sets that have a symmetric $s$-$\bar{s}$ sea, indicating that any $s$-$\bar{s}$ asymmetry in the Bjorken-x region relevant for this measurement is small.
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A measurement of W± boson production in Pb+Pb collisions at √sNN=5.02 TeV is reported using data recorded by the ATLAS experiment at the LHC in 2015, corresponding to a total integrated luminosity of ...0.49nb-1. The W± bosons are reconstructed in the electron or muon leptonic decay channels. Production yields of leptonically decaying W± bosons, normalised by the total number of minimum-bias events and the nuclear thickness function, are measured within a fiducial region defined by the detector acceptance and the main kinematic requirements. These normalised yields are measured separately for W+ and W- bosons, and are presented as a function of the absolute value of pseudorapidity of the charged lepton and of the collision centrality. The lepton charge asymmetry is also measured as a function of the absolute value of lepton pseudorapidity. In addition, nuclear modification factors are calculated using the W± boson production cross-sections measured in pp collisions. The results are compared with predictions based on next-to-leading-order calculations with CT14 parton distribution functions as well as with predictions obtained with the EPPS16 and nCTEQ15 nuclear parton distribution functions. No dependence of normalised production yields on centrality and a good agreement with predictions are observed for mid-central and central collisions. For peripheral collisions, the data agree with predictions within 1.7 (0.9) standard deviations for W- (W+) bosons.
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A search for a narrow scalar resonance decaying into an opposite-sign muon pair produced in events with and without b-tagged jets is presented in this paper. The search uses 36.1 fb-1 of $ ...\sqrt{s}=13 $ TeV proton-proton collision data recorded by the ATLAS experiment at the LHC. No significant excess of events above the expected Standard Model background is observed in the investigated mass range of 0.2 to 1.0 TeV. The observed upper limits at 95% confidence level on the cross section times branching ratio for b-quark associated production and gluon-gluon fusion are between 1.9 and 41 fb and 1.6 and 44 fb respectively, which is consistent with expectations. Figure not available: see fulltext..
A search for excited electrons produced in pp collisions at $\sqrt{s}$ = 13 TeV via a contact interaction $q\overline{q}$ → ee* is presented. The search uses 36.1 fb-1 of data collected in 2015 and ...2016 by the ATLAS experiment at the Large Hadron Collider. Decays of the excited electron into an electron and a pair of quarks ($eq\overline{q}$) are targeted in final states with two electrons and two hadronic jets, and decays via a gauge interaction into a neutrino and a W boson (νW) are probed in final states with an electron, missing transverse momentum, and a large-radius jet consistent with a hadronically decaying W boson. No significant excess is observed over the expected backgrounds. Upper limits are calculated for the pp→ ee*→$eeq\overline{q}$ and pp→ ee*→ eνW production cross sections as a function of the excited electron mass $m_{e*}$ at 95% confidence level. The limits are translated into lower bounds on the compositeness scale parameter Λ of the model as a function of $m_{e*}$. For $m_{e*}$ <0.5 TeV, the lower bound for Λ is 11 TeV. In the special case of $m_{e*}$=Λ, the values of $m_{e*}$< 4.8 TeV are excluded. The presented limits on Λ are more stringent than those obtained in previous searches.
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The ATLAS experiment at the Large Hadron Collider employs a two-level trigger system to record data at an average rate of 1 kHz from physics collisions, starting from an initial bunch crossing rate ...of 40 MHz. During the LHC Run 2 (2015–2018), the ATLAS trigger system operated successfully with excellent performance and flexibility by adapting to the various run conditions encountered and has been vital for the ATLAS Run-2 physics programme. For proton-proton running, approximately 1500 individual event selections were included in a trigger menu which specified the physics signatures and selection algorithms used for the data-taking, and the allocated event rate and bandwidth. The trigger menu must reflect the physics goals for a given data collection period, taking into account the instantaneous luminosity of the LHC and limitations from the ATLAS detector readout, online processing farm, and offline storage. This document discusses the operation of the ATLAS trigger system during the nominal proton-proton data collection in Run 2 with examples of special data-taking runs. Aspects of software validation, evolution of the trigger selection algorithms during Run 2, monitoring of the trigger system and data quality as well as trigger configuration are presented.
The study of different modifications for the procedure of determining the reconstructed mass based on the kinematic fit for dilepton events to improve the precision of the top quark mass measurement ...using the template method is described. It is demonstrated that accounting for the top quark decay width from its mass reduces the statistical measurement error by approximately 20%. The possibility of using transfer functions for a detailed description of the connection between the experimentally measured energy characteristics of
b
jets and the momenta of
b
quarks that produced these jets is considered. The capabilities of the modified method as used for the “lepton plus track” sample of the CDF experiment are evaluated.
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Upgraded Tevatron luminosity in Run-II (started 2001) has opened a new level of modern heavy-quark studies compared to that one of Run-I. Now top event samples contain hundreds of event statistics ...for investigation. This review mainly covers the mass measurements of the top quark produced at √s = 1.96 TeV in {ie359-2} collisions at the Collider Detector of Fermilab with the integrated luminosity samples up to 1 fb
−1
. As an example of the top quark mass measurements we consider so-called Matrix Element method in “lepton + jets” and “dilepton” channels of the top-quark decay. The CDF top quark mass obtained in lepton +jets mode is the world most precise single measurement of this important physics parameter. The review summarizes the essential results of the CDF top-quark mass measurement achieved and published for the recent 2003–2008 period. We consider also b-quark baryon discoveries like Σ
b
, Σ
b
*
, Θ
b
as well as first observation of {ie359-3} oscillations. Let us mention here that a CDF/JINR-group created significant contribution to the new CDF complex and physics investigation.
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