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L. Kurchaninov

Publications and source records attributed to L. Kurchaninov.

At least 19 recordsLinked to original sources
arXiv2025

European Strategy for Particle Physics Update -- PIONEER: a next generation rare pion decay experiment

PIONEER is a rapidly developing effort aimed to perform a pristine test of lepton flavour universality (LFU) and of the unitarity of the first row of the CKM matrix by significantly improving the measurements of rare decays of the charged pion. In Phase I, PIONEER aims to measure the charged-pion branching ratio to electrons vs.\ muons $R_{e/μ}$ to 1 part in $10^4$, improving the current experimental result $R_{e/μ}\,\text{(exp)} =1.2327(23)\times10^{-4}$ by a factor of 15. This precision on $R_{e/μ}$ will match the theoretical accuracy of the SM prediction allowing for a test of LFU at an unprecedented level, probing non-SM explanations of LFU violation through sensitivity to quantum effects of new particles up to the PeV mass scale. Phase II and III will aim to improve the experimental precision of the branching ratio of pion beta decay, $π^+\to π^0 e^+ ν(γ)$, currently at $1.036(6)\times10^{-8}$, by a factor of three and six, respectively. The improved measurements will be used to extract $V_{ud}$ in a theoretically pristine manner. The ultimate precision of $V_{ud}$ is expected to reach the 0.05\,\% level, allowing for a stringent test of CKM unitarity. The PIONEER experiment will also improve the experimental limits by an order of magnitude or more on a host of exotic decays that probe the effects of heavy neutrinos and dark sector physics. This input to the 2026 update of the European Strategy for Particle Physics Strategy describes the physics motivation and the conceptual design of the PIONEER experiment, and is prepared based on the PIONEER proposal submitted to and approved with high priority by the PSI program advisory committee (PAC). Using intense pion beams, and state-of-the-art instrumentation and computational resources, the PIONEER experiment is aiming to begin data taking by the end of this decade.

hep-ex↗
arXiv2024

Measurement of the response function of the PIENU calorimeter

Measurements of the response function of the PIENU NaI(T$\ell$) and CsI crystal calorimeter using a monochromatic 70 MeV/c positron beam at various incidence angles are described. The experimental setup and relevant physical processes involved were simulated using Geant4 to reproduce positron energy spectra. Monte Carlo simulations were compared with experimental data across ten calorimeter-beam angles and showed good agreement. This allowed the validation of simulation parameters that were essential for precise measurements of pion decays.

hep-ex↗
arXiv2022

Design and Performance of a Novel Low Energy Multi-Species Beamline for the ALPHA Antihydrogen Experiment

The ALPHA Collaboration, based at the CERN Antiproton Decelerator, has recently implemented a novel beamline for low-energy ($\lesssim$ 100 eV) positron and antiproton transport between cylindrical Penning traps that have strong axial magnetic fields. Here, we describe how a combination of semianalytical and numerical calculations were used to optimise the layout and design of this beamline. Using experimental measurements taken during the initial commissioning of the instrument, we evaluate its performance and validate the models used for its development. By combining data from a range of sources, we show that the beamline has a high transfer efficiency, and estimate that the percentage of particles captured in the experiments from each bunch is (78 $\pm$ 3)% for up to $10^{5}$ antiprotons, and (71 $\pm$ 5)% for bunches of up to $10^{7}$ positrons.

physics.acc-ph↗
arXiv2021

Energy reconstruction in a liquid argon calorimeter cell using convolutional neural networks

The liquid argon ionization current in a sampling calorimeter cell can be analyzed to determine the energy of detected particles. In practice, experimental artifacts such as pileup and electronic noise make the inference of energy from current a difficult process. The beam intensity of the Large Hadron Collider will be significantly increased during the Phase-II long shut down of 2025-2027. Signal processing techniques that are used to extract the energy of detected particles in the ATLAS detector will suffer a significant loss in performance under these conditions. This paper compares the presently used optimal filter technique to convolutional neural networks for energy reconstruction in the ATLAS liquid argon hadronic end cap calorimeter. In particular, it is shown that convolutional neural networks trained with an appropriately tuned and novel loss function are able to outperform the optimal filter technique.

physics.ins-det↗
arXiv2021

Search for three body pion decays $π^+{\to}l^+νX$

The three body pion decays $π^+{\rightarrow}l^+νX~(l=e,μ)$, where $X$ is a weakly interacting neutral boson, were searched for using the full data set from the PIENU experiment. An improved limit on $Γ(π^+{\to}e^+νX)/Γ(π^+{\to}μ^+ν_μ)$ in the mass range $0<m_X<120$ MeV/$c^2$ and a first result for $Γ(π^+{\to}μ^+νX)/Γ(π^+{\to}μ^+ν_μ)$ in the region $0<m_X<33.9$ MeV/$c^2$ were obtained. The Majoron-neutrino coupling model was also constrained using the current experimental result of the $π^+{\to}e^+ν_e(γ)$ branching ratio.

hep-ex↗
arXiv2020

Search for the rare decays $π^+ \to μ^+ν_μν\barν$ and $π^+ \to e^+ν_eν\barν$

The rare pion decays $π^+{\rightarrow}μ^+ν_μν\barν$ and $π^+{\rightarrow}e^+ν_{e}ν\barν$ are allowed in the Standard Model but highly suppressed. These decays were searched for using data from the PIENU experiment. A first result for $Γ(π^+{\rightarrow}μ^+ν_μν\barν)/Γ(π^+{\rightarrow}μ^+ν_μ)<8.6{\times}10^{-6}$, and an improved measurement $Γ(π^+{\rightarrow}{e}^+ν_{e}ν\barν)/Γ(π^+{\rightarrow}μ^+ν_μ)<1.6{\times}10^{-7}$ were obtained.

hep-ex↗
arXiv2020

Improved search for two body muon decay $μ^+{\rightarrow}e^+X_H$

Charged lepton flavor violating muon decay $μ^+{\rightarrow}e^+X_H$, where $X_H$ is a massive neutral boson, was sought by searching for extra peaks in the muon decay $μ^+{\rightarrow}e^+ν\barν$ energy spectrum in the $m_{X_H}$ mass region $47.8-95.1$ MeV/$c^2$. No signal was found and 90% confidence level upper limits were set on the branching ratio $Γ(μ^+{\rightarrow}e^+X_H)/Γ(μ^+{\rightarrow}e^+ν\barν)$ at the level of $10^{-5}$ for this region.

hep-ex↗
arXiv2019

A fast-switching magnet serving a spallation-driven ultracold neutron source

A fast-switching, high-repetition-rate magnet and power supply have been developed for and operated at TRIUMF, to deliver a proton beam to the new ultracold neutron (UCN) facility. The facility possesses unique operational requirements: a time-averaged beam current of 40~$μ$A with the ability to switch the beam on or off for several minutes. These requirements are in conflict with the typical operation mode of the TRIUMF cyclotron which delivers nearly continuous beam to multiple users. To enable the creation of the UCN facility, a beam-sharing arrangement with another facility was made. The beam sharing is accomplished by the fast-switching (kicker) magnet which is ramped in 50~$μ$s to a current of 193~A, held there for approximately 1~ms, then ramped down in the same short period of time. This achieves a 12~mrad deflection which is sufficient to switch the proton beam between the two facilities. The kicker magnet relies on a high-current, low-inductance coil connected to a fast-switching power supply that is based on insulated-gate bipolar transistors (IGBTs). The design and performance of the kicker magnet system and initial beam delivery results are reported.

physics.acc-ph↗
arXiv2019

Search for Heavy Neutrinos in $π\to μν$ Decay

Heavy neutrinos were sought in pion decays $π^+ \rightarrow μ^+ ν$ by examining the observed muon energy spectrum for extra peaks in addition to the expected peak for a massless neutrino. No evidence for heavy neutrinos was observed. Upper limits were set on the neutrino mixing matrix $|U_{μi}|^2$ in the neutrino mass region of 15.7--33.8 MeV/c$^2$, improving on previous results by an order of magnitude.

hep-ex↗
arXiv2018

A beamline for fundamental neutron physics at TRIUMF

This article describes the new primary proton beamline 1U at TRIUMF. The purpose of this beamline is to produce ultracold neutrons (UCN) for fundamental-physics experiments. It delivers up to 40 microA of 480 MeV protons from the TRIUMF cyclotron to a tungsten spallation target and uses a fast kicker to share the beam between the Center for Molecular and Materials Science and UCN. The beamline has been successfully commissioned and operated with a beam current up to 10 microA, facilitating first large-scale UCN production in Canada.

physics.ins-det↗
arXiv2018

In-beam internal conversion electron spectroscopy with the SPICE detector

The SPectrometer for Internal Conversion Electrons (SPICE) has been commissioned for use in conjunction with the TIGRESS $γ$-ray spectrometer at TRIUMF's ISAC-II facility. SPICE features a permanent rare-earth magnetic lens to collect and direct internal conversion electrons emitted from nuclear reactions to a thick, highly segmented, lithium-drifted silicon detector. This arrangement, combined with TIGRESS, enables in-beam $γ$-ray and internal conversion electron spectroscopy to be performed with stable and radioactive ion beams. Technical aspects of the device, capabilities, and initial performance are presented.

physics.ins-det↗
arXiv2018

Improved Search for Heavy Neutrinos in the Decay $π\rightarrow eν$

A search for massive neutrinos has been made in the decay $π\rightarrow e^+ ν$. No evidence was found for extra peaks in the positron energy spectrum indicative of pion decays involving massive neutrinos ($π\rightarrow e^+ ν_h$). Upper limits (90 \% C.L.) on the neutrino mixing matrix element $|U_{ei}|^2$ in the neutrino mass region 60--135 MeV/$c^2$ were set, which are %representing an order of magnitude improvement over previous results.

hep-ex↗
arXiv2017

A novel comparison of Møller and Compton electron-beam polarimeters

We have performed a novel comparison between electron-beam polarimeters based on Møller and Compton scattering. A sequence of electron-beam polarization measurements were performed at low beam currents ($<$ 5 $μ$A) during the $Q_{\rm weak}$ experiment in Hall C at Jefferson Lab. These low current measurements were bracketed by the regular high current (180 $μ$A) operation of the Compton polarimeter. All measurements were found to be consistent within experimental uncertainties of 1% or less, demonstrating that electron polarization does not depend significantly on the beam current. This result lends confidence to the common practice of applying Møller measurements made at low beam currents to physics experiments performed at higher beam currents. The agreement between two polarimetry techniques based on independent physical processes sets an important benchmark for future precision asymmetry measurements that require sub-1% precision in polarimetry.

physics.ins-det↗
arXiv2016

Precision Electron-Beam Polarimetry using Compton Scattering at 1 GeV

We report on the highest precision yet achieved in the measurement of the polarization of a low energy, $\mathcal{O}$(1 GeV), electron beam, accomplished using a new polarimeter based on electron-photon scattering, in Hall~C at Jefferson Lab. A number of technical innovations were necessary, including a novel method for precise control of the laser polarization in a cavity and a novel diamond micro-strip detector which was able to capture most of the spectrum of scattered electrons. The data analysis technique exploited track finding, the high granularity of the detector and its large acceptance. The polarization of the $180~μ$A, $1.16$~GeV electron beam was measured with a statistical precision of $<$~1\% per hour and a systematic uncertainty of 0.59\%. This exceeds the level of precision required by the \qweak experiment, a measurement of the vector weak charge of the proton. Proposed future low-energy experiments require polarization uncertainty $<$~0.4\%, and this result represents an important demonstration of that possibility. This measurement is also the first use of diamond detectors for particle tracking in an experiment.

nucl-ex↗
arXiv2015

Status of the TRIUMF PIENU Experiment

The PIENU experiment at TRIUMF aims to measure the pion decay branching ratio $R=Γ(π^+{\rightarrow}e^+ν_e(γ))/Γ(π^+{\rightarrow}μ^+ν_μ(γ))$ with precision $<0.1$% to provide a sensitive test of electron-muon universality in weak interactions. The current status of the PIENU experiment is presented.

physics.ins-det↗
arXiv2015

Improved measurement of the $π\rightarrow \mbox{e} ν$ branching ratio

A new measurement of the branching ratio, $R_{e/μ} =Γ(π^+ \rightarrow \mbox{e}^+ ν+ π^+ \rightarrow \mbox{e}^+ νγ)/ Γ(π^+ \rightarrow μ^+ ν+ π^+ \rightarrow μ^+ νγ)$, resulted in $R_{e/μ}^{exp} = (1.2344 \pm 0.0023 (stat) \pm 0.0019 (syst)) \times 10^{-4}$. This is in agreement with the standard model prediction and improves the test of electron-muon universality to the level of 0.1 %.

hep-ex↗
arXiv2015

Detector for measuring the $π^+\to e^+ν_e$ branching fraction

The PIENU experiment at TRIUMF is aimed at a measurement of the branching ratio $R^{e/μ}$ = ${Γ\big((π^{+} \rightarrow e^{+} ν_{e}) + (π^{+} \rightarrow e^{+} ν_{e}γ)\big)}/{Γ\big((π^{+} \rightarrow μ^{+} ν_μ)+(π^{+} \rightarrow μ^{+} ν_μγ)\big)}$ with precision $<$0.1\%. Incident pions, delivered at the rate of 60 kHz with momentum 75 MeV/c, were degraded and stopped in a plastic scintillator target. Pions and their decay product positrons were detected with plastic scintillators and tracked with multiwire proportional chambers and silicon strip detectors. The energies of the positrons were measured in a spectrometer consisting of a large NaI(T$\ell$) crystal surrounded by an array of pure CsI crystals. This paper provides a description of the PIENU experimental apparatus and its performance in pursuit of $R^{e/μ}$.

physics.ins-det↗