arXiv subjects

T. Lesiak

Publications and source records attributed to T. Lesiak.

10 recordsLinked to original sources

arXiv2025

Fundamental Nuclear and Particle Physics At Neutron Sources

Fundamental neutron and neutrino physics at neutron sources, combining precision measurements and theory, can probe new physics at energy scales well beyond the highest energies probed by the LHC and possible future high energy collider facilities. The European Spallation Source (ESS) will in the not too far future be a most powerful pulsed neutron source and simultaneously the world's brightest pulsed neutrino source. The ESS, and neutron sources in general, can provide unprecedented and unique opportunities to contribute to the search for the missing elements in the Standard Model of particle physics. Currently there are no strong indications where hints of the origin of the new physics will emerge. A multi-pronged approach will provide the fastest path to fill the gaps in our knowledge and neutron sources have a pivotal role to play. To survey the ongoing and proposed physics experiments at neutron sources and assess their potential impact, a workshop was held at Lund University in January, 2025. This report is a summary of that workshop and has been prepared as input to the European Strategy Update.

nucl-ex↗

arXiv2025

Polish national input to the 2026 update of the European Strategy for Particle Physics

The Polish high energy physics (HEP) community fully recognizes the urgent need to host at CERN a flagship project implementing a broad, long-term, and comprehensive vision of particle physics research and pursuing technological advances. Thus, we give preference and declare willingness to actively engage and participate in every aspect of the FCC project (both FCC-ee and FCC-hh), particularly accelerator development, detector construction, theoretical calculations, and physics analyses. As the e+e- Higgs Factory is the top priority for our field, the proposal to build a linear collider facility at CERN, opening up complementary physics prospects, should be considered as the second option. Polish teams declare strong support and are fully committed to contribute to the full exploitation of all aspects of the physics potential of the LHC and the HL-LHC programmes. To ensure the long-term development of particle physics, we also support the continuation of the high-field magnet research programme, as well as investigating other scenarios including, in particular, linear acceleration techniques and new acceleration technologies such as plasma acceleration, the muon collider and Gamma Factory. In addition, CERN should continue to provide support to fixed-target programmes at SPS as well as other non-collider and non-accelerator experiments at CERN. Participation in major projects conducted in and outside Europe should also be fostered. Education, communication, and outreach of particle physics are of paramount importance for the future of our field. An increased effort coordinated at the European level and resources allocated in all Member States are essential to effectively support future large-scale particle physics projects.

hep-ex↗

arXiv2019

Top-Quark Physics at the CLIC Electron-Positron Linear Collider

The Compact Linear Collider (CLIC) is a proposed future high-luminosity linear electron-positron collider operating at three energy stages, with nominal centre-of-mass energies: 380 GeV, 1.5 TeV, and 3 TeV. Its aim is to explore the energy frontier, providing sensitivity to physics beyond the Standard Model (BSM) and precision measurements of Standard Model processes with an emphasis on Higgs boson and top-quark physics. The opportunities for top-quark physics at CLIC are discussed in this paper. The initial stage of operation focuses on top-quark pair production measurements, as well as the search for rare flavour-changing neutral current (FCNC) top-quark decays. It also includes a top-quark pair production threshold scan around 350 GeV which provides a precise measurement of the top-quark mass in a well-defined theoretical framework. At the higher-energy stages, studies are made of top-quark pairs produced in association with other particles. A study of ttH production including the extraction of the top Yukawa coupling is presented as well as a study of vector boson fusion (VBF) production, which gives direct access to high-energy electroweak interactions. Operation above 1 TeV leads to more highly collimated jet environments where dedicated methods are used to analyse the jet constituents. These techniques enable studies of the top-quark pair production, and hence the sensitivity to BSM physics, to be extended to higher energies. This paper also includes phenomenological interpretations that may be performed using the results from the extensive top-quark physics programme at CLIC.

hep-ex↗

arXiv2019

Performance and Moli`ere radius measurements using a compact prototype of LumiCal in an electron test beam

A new design of a detector plane of sub-millimetre thickness for an electromagnetic sampling calorimeter is presented. It is intended to be used in the luminometers LumiCal and BeamCal in future linear $e^+e^-$ collider experiments. The detector planes were produced utilising novel connectivity scheme technologies. They were installed in a compact prototype of the calorimeter and tested at DESY with an electron beam of energy 1-5 GeV. The performance of a prototype of a compact LumiCal comprising eight detector planes was studied. The effective Moli`ere radius at 5 GeV was determined to be (8.1 +/- 0.1 (stat) +/- 0.3 (syst)) mm, a value well reproduced by the Monte Carlo (MC) simulation (8.4 +/- 0.1) mm. The dependence of the effective Moli`ere radius on the electron energy in the range 1-5 GeV was also studied. Good agreement was obtained between data and MC simulation.

physics.ins-det↗

arXiv2018

Measurement of shower development and its Molière radius with a four-plane LumiCal test set-up

A prototype of a luminometer, designed for a future e+e- collider detector, and consisting at present of a four-plane module, was tested in the CERN PS accelerator T9 beam. The objective of this beam test was to demonstrate a multi-plane tungsten/silicon operation, to study the development of the electromagnetic shower and to compare it with MC simulations. The Molière radius has been determined to be 24.0 +/- 0.6 (stat.) +/- 1.5 (syst.) mm using a parametrization of the shower shape. Very good agreement was found between data and a detailed Geant4 simulation.

physics.ins-det↗

arXiv2017

Higgs Physics at the CLIC Electron-Positron Linear Collider

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: sqrt(s) = 350 GeV, 1.4 TeV 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- -> Hnunu), resulting in precise measurements of the production cross sections, the Higgs total decay width Gamma_H, and model-independent determinations of the Higgs couplings. Operation at sqrt(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- -> ttH and e+e- -> HHnunu 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.

hep-ex↗

arXiv2015

Performance of fully instrumented detector planes of the forward calorimeter of a Linear Collider detector

Detector-plane prototypes of the very forward calorimetry of a future detector at an e+e- collider have been built and their performance was measured in an electron beam. The detector plane comprises silicon or GaAs pad sensors, dedicated front-end and ADC ASICs, and an FPGA for data concentration. Measurements of the signal-to-noise ratio and the response as a function of the position of the sensor are presented. A deconvolution method is successfully applied, and a comparison of the measured shower shape as a function of the absorber depth with a Monte-Carlo simulation is given.

physics.ins-det↗

arXiv2009

Measurement of $B \to D_s^{(*)} Kπ$ branching fractions

We report a measurement of the exclusive $B^+$ meson decay to the $D_s^{(*)-} K^+π^+$ final state using $657 \times 10^{6} B\overline{B}$ pairs collected at the $Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We use $D_s^{*-}\to D_s^-γ$ and the $D_s^-\to ϕπ^-$, $\overline{K^{*}}(892)^0 K^-$ and $K^0_S K^-$ decay modes for $D_s^{(*)}$ reconstruction and measure the following branching fractions: ${\cal B}(B^+\to D_s^-K^+π^+)= (1.94^{+0.09}_{-0.08} ({\mathrm stat})^{+0.20}_{-0.20} {\mathrm (syst)} \pm 0.17 {\cal(B)})\times 10^{-4}$ and ${\cal B}(B^+\to D_s^{*-}K^+π^+)= (1.47^{+0.15}_{-0.14} ({\mathrm stat})^{+0.19}_{-0.19} ({\mathrm syst}) \pm 0.13 {\cal(B)})\times 10^{-4}$. The uncertainties are due to statistics, experimental systematic errors and uncertainties of intermediate branching fractions, respectively.

hep-ex↗

arXiv2008

Measurement of masses of the $Ξ_c(2645)$ and $Ξ_c(2815)$ baryons and observation of $Ξ_c(2980)\toΞ_c(2645)π$ %and observation of the $Ξ_c(2980)$ and observation of $Ξ_c(2980)\to Ξ_c(2645)π$

We report a precise measurement of the masses of the $Ξ_c(2645)$ and $Ξ_c(2815)$ baryons using a data sample of 414 fb$^{-1}$ collected by the Belle collaboration at the KEKB $e^+ e^-$ collider. The states $Ξ_c(2645)^{0,+}$ are observed in the $Ξ_c^{+,0}π^{-,+}$ decay modes, while the $Ξ_c(2815)^{0,+}$ are reconstructed in the $Ξ_c(2645)^{+,0}π^{-,+}$ decay modes. The following mass splittings are determined: $m_{Ξ_c(2645)^+} - m_{Ξ_c(2645)^0} = (-0.1 \pm 0.3 ({\rm stat}) \pm 0.6 {(\rm syst})) {\rm MeV}/{\rm c}^2$ and $m_{Ξ_c(2815)^+} - m_{Ξ_c(2815)^0} = (-3.4 \pm 1.9 ({\rm stat}) \pm 0.9 {(\rm syst})) {\rm MeV}/{\rm c}^2$ with a much better precision than the current world averages. We also observe a new decay mode, $Ξ_c(2980)^{0,+} \to Ξ_c(2645)^{+,0}π^{-,+}$.

hep-ex↗

arXiv2004

Measurement of masses and branching ratios of $Ξ_c^+$ and $Ξ_c^0$ baryons

We report a measurement of the $Ξ_c^+$ and $Ξ_c^0$ baryon masses, and the branching ratios for various $Ξ_c$ decays, using $140 \mathrm{fb}^{-1}$ of data collected by the Belle experiment at the KEKB $e^+ e^-$ collider.The mass splitting $m_{Ξ_c^0} - m_{Ξ_c^+}$ is found to be $2.9\pm 0.5 \mathrm{MeV}/c^2$; this measurement is three times as precise as the current world average. We measure the branching ratios $Γ(Ξ_c^+\to ΛKππ)/Γ(Ξ_c^+\toΞππ) = 0.32\pm 0.03 \pm 0.02$ and $Γ(Ξ_c^0\to p KKπ)/Γ(Ξ_c^0\toΞπ) = 0.33\pm 0.03 \pm 0.03$, with improved precision, and measure $Γ(Ξ_c^+\to p K^0_S K^0_S)/Γ(Ξ_c^+\toΞππ) = 0.087\pm 0.016 \pm 0.014$, $Γ(Ξ_c^0\to ΛKπ)/Γ(Ξ_c^0\toΞπ) = 1.07\pm 0.12 \pm 0.07$ and $Γ(Ξ_c^0\to ΛK^0_S)/Γ(Ξ_c^0\toΞπ) = 0.21\pm 0.02 \pm 0.02$ for the first time. In $Ξ_c^0$ decays to the $p K^- K^- π^+$ final state, we find evidence for the process $Ξ_c^0 \to p K^- \bar{K}{}^\ast(892)^0$ and measure the fraction of decays via this process to be $0.51\pm 0.03 \pm 0.01$.

hep-ex↗