arXiv subjects

P. Kuusiniemi

Publications and source records attributed to P. Kuusiniemi.

14 recordsLinked to original sources

arXiv2025

Evidence for Anomalies in Muon-Induced Neutron Emissions from Pb

This paper examines neutron multiplicity spectra emitted from massive targets at depths of 3, 40, 210, 583, 1166, and 4000 m.w.e. The measurements, carried out between 2001 and 2024, used three experimental setups with either 14 or 60 He-3 neutron detectors and lead (Pb) targets weighing 306, 565, or 1134 kg. The total acquisition time exceeded six years. When available, the spectra obtained were compared with Monte Carlo simulations. Our data indicate potential anomalies that might limit the accuracy of modelling the muon-induced neutron multiplicity spectra with a single power-law function. Even at shallow depths, the single-power-law approach fails to account for a small but statistically significant excess of events at the highest multiplicities. This excess resembles a second power-law component. Since the anomaly varies only slightly with depth, it is unlikely to be directly linked to the muon flux. Our highest-quality data, acquired at 583 m.w.e., suggest a possible structure similar to the emission of approximately 74, 106, 143, and 214 neutrons from the target. We propose new underground measurements using low-cost, large-area, position-sensitive neutron arrays surrounding multi-ton Pb targets to verify and investigate these suspected anomalies and to determine their origin.

hep-ex↗

arXiv2023

New Evidence for DM-like Anomalies in Neutron Multiplicity Spectra

Subterrestrial neutron spectra show weak but consistent anomalies at multiplicities ~100 and above. The origin of the excess events remains ambiguous, but, in principle, it could be a signature of Dark Matter WIMP annihilation-like interaction with a massive Pb target. However, since the results of the available measurements are below the 5-sigma discovery level, and the observed anomalous structures are on a significant muon-induced background, an independent verification at even greater depth is needed. For that purpose, we have launched NEMESIS 1.4 - a new dedicated experiment consisting of a 1134 kg Pb target and 14 He-3 detectors with PE moderators and a fully digital readout. NEMESIS 1.4 has been taking data at the deepest level (1.4 km, 4000 m.w.e.) of the Pyhasalmi mine, Finland, since November 2022. We describe the idea behind the new setup, compare the first results with the previous data and Monte Carlo simulations, and give the outlook for further research. If the existence of the anomalies is unambiguously confirmed and the model interpretation positively verified, this will be the first Indirect Detection of Dark Matter in the laboratory.

hep-ex↗

arXiv2019

Measurement of the $2^+\rightarrow 0^+$ ground-state transition in the $β$ decay of $^{20}$F

We report the first detection of the second-forbidden, non-unique, $2^+\rightarrow 0^+$, ground-state transition in the $β$ decay of $^{20}$F. A low-energy, mass-separated $^{20}\rm{F}^+$ beam produced at the IGISOL facility in Jyväskylä, Finland, was implanted in a thin carbon foil and the $β$ spectrum measured using a magnetic transporter and a plastic-scintillator detector. The $β$-decay branching ratio inferred from the measurement is $b_β = [ 0.41\pm 0.08\textrm{(stat)}\pm 0.07\textrm{(sys)}] \times 10^{-5}$ corresponding to $\log ft = 10.89(11)$, making this one of the strongest second-forbidden, non-unique $β$ transitions ever measured. The experimental result is supported by shell-model calculations and has significant implications for the final evolution of stars that develop degenerate oxygen-neon cores. Using the new experimental data, we argue that the astrophysical electron-capture rate on $^{20}$Ne is now known to within better than 25% at the relevant temperatures and densities.

nucl-ex↗

arXiv2018

Possibilities for Underground Physics in the Pyhäsalmi mine

The Pyhäsalmi mine is uniquely suited to host new generation of large-scale underground experiments. It was chosen both by the LAGUNA-LBNO and by the LENA Collaboration as the preferred site for a giant neutrino observatory. Regrettably, none of these projects got funded. The termination of the underground excavations in the fall of 2019 marks an important milestone. To maintain the infrastructure in good condition a new sponsor must be found: either a large-scale scientific project or new commercial operation. The considered alternatives for the commercial used of the mine include a pumped-storage hydroelectricity plant and a high-security underground data-storage centre. Without a new sponsor the ongoing experiments, including the cosmic-ray experiment EMMA and the study of 14C content in liquid scintillators, have to be completed within the next few years.

physics.ins-det↗

arXiv2014

The LBNO long-baseline oscillation sensitivities with two conventional neutrino beams at different baselines

The proposed Long Baseline Neutrino Observatory (LBNO) initially consists of $\sim 20$ kton liquid double phase TPC complemented by a magnetised iron calorimeter, to be installed at the Pyhäsalmi mine, at a distance of 2300 km from CERN. The conventional neutrino beam is produced by 400 GeV protons accelerated at the SPS accelerator delivering 700 kW of power. The long baseline provides a unique opportunity to study neutrino flavour oscillations over their 1st and 2nd oscillation maxima exploring the $L/E$ behaviour, and distinguishing effects arising from $δ_{CP}$ and matter. In this paper we show how this comprehensive physics case can be further enhanced and complemented if a neutrino beam produced at the Protvino IHEP accelerator complex, at a distance of 1160 km, and with modest power of 450 kW is aimed towards the same far detectors. We show that the coupling of two independent sub-MW conventional neutrino and antineutrino beams at different baselines from CERN and Protvino will allow to measure CP violation in the leptonic sector at a confidence level of at least $3σ$ for 50\% of the true values of $δ_{CP}$ with a 20 kton detector. With a far detector of 70 kton, the combination allows a $3σ$ sensitivity for 75\% of the true values of $δ_{CP}$ after 10 years of running. Running two independent neutrino beams, each at a power below 1 MW, is more within today's state of the art than the long-term operation of a new single high-energy multi-MW facility, which has several technical challenges and will likely require a learning curve.

hep-ph↗

arXiv2014

Optimised sensitivity to leptonic CP violation from spectral information: the LBNO case at 2300 km baseline

One of the main goals of the Long Baseline Neutrino Observatory (LBNO) is to study the $L/E$ behaviour (spectral information) of the electron neutrino and antineutrino appearance probabilities, in order to determine the unknown CP-violation phase $δ_{CP}$ and discover CP-violation in the leptonic sector. The result is based on the measurement of the appearance probabilities in a broad range of energies, covering t he 1st and 2nd oscillation maxima, at a very long baseline of 2300 km. The sensitivity of the experiment can be maximised by optimising the energy spectra of the neutrino and anti-neutrino fluxes. Such an optimisation requires exploring an extended range of parameters describing in details the geometries and properties of the primary protons, hadron target and focusing elements in the neutrino beam line. In this paper we present a numerical solution that leads to an optimised energy spectra and study its impact on the sensitivity of LBNO to discover leptonic CP violation. In the optimised flux both 1st and 2nd oscillation maxima play an important role in the CP sensitivity. The studies also show that this configuration is less sensitive to systematic errors (e.g. on the total event rates) than an experiment which mainly relies on the neutrino-antineutrino asymmetry at the 1st maximum to determine the existence of CP-violation.

hep-ph↗

arXiv2014

LBNO-DEMO: Large-scale neutrino detector demonstrators for phased performance assessment in view of a long-baseline oscillation experiment

In June 2012, an Expression of Interest for a long-baseline experiment (LBNO) has been submitted to the CERN SPSC. LBNO considers three types of neutrino detector technologies: a double-phase liquid argon (LAr) TPC and a magnetised iron detector as far detectors. For the near detector, a high-pressure gas TPC embedded in a calorimeter and a magnet is the baseline design. A mandatory milestone is a concrete prototyping effort towards the envisioned large-scale detectors, and an accompanying campaign of measurements aimed at assessing the detector associated systematic errors. The proposed $6\times 6\times 6$m$^3$ DLAr is an industrial prototype of the design discussed in the EoI and scalable to 20 kton or 50~kton. It is to be constructed and operated in a controlled laboratory and surface environment with test beam access, such as the CERN North Area (NA). Its successful operation and full characterisation will be a fundamental milestone, likely opening the path to an underground deployment of larger detectors. The response of the DLAr demonstrator will be measured and understood with an unprecedented precision in a charged particle test beam (0.5-20 GeV/c). The exposure will certify the assumptions and calibrate the response of the detector, and allow to develop and to benchmark sophisticated reconstruction algorithms, such as those of 3-dimensional tracking, particle ID and energy flow in liquid argon. All these steps are fundamental for validating the correctness of the physics performance described in the LBNO EoI.

physics.ins-det↗

arXiv2011

Multichannel Data Acquisition System for Scintillation Detectors of the Emma Experiment

The multichannel data acquisition system is intended to be used in the EMMA experiment studying cosmic rays. The array will be in the Pihasalmi mine (central Finland) at a depth of about 85 m. The scintillator counters (SC-1) of the array are cast plastic scintillators with a wavelength of each SC-1 detector is 12.2{\times}12.2{\times}3.0 cm^3. 16 SC-1 detectors are placed in the metal case of 50.0{\times}50.0{\times}13.0 cm^3 dimension. Each case, called SC-16 detector, contains electronics of preliminary processing of signals and operating mode stabilization. The whole of the array will contain 96 detectors SC-16. It will make 1536 channels placed in three planes (48+24+24 detectors). The array will allow us to measure the time of flight of particles between SC-16 detectors and the coordinates of SC-1 fired detectors. This paper presents the function diagram of data acquisition system that includes electronic of detectors, the hodoscope pulse channels, the trigger block and VME blocks.

astro-ph.IM↗

arXiv2009

The LAGUNA design study- towards giant liquid based underground detectors for neutrino physics and astrophysics and proton decay searches

The feasibility of a next generation neutrino observatory in Europe is being considered within the LAGUNA design study. To accommodate giant neutrino detectors and shield them from cosmic rays, a new very large underground infrastructure is required. Seven potential candidate sites in different parts of Europe and at several distances from CERN are being studied: Boulby (UK), Canfranc (Spain), Fréjus (France/Italy), Pyhäsalmi (Finland), Polkowice-Sieroszowice (Poland), Slanic (Romania) and Umbria (Italy). The design study aims at the comprehensive and coordinated technical assessment of each site, at a coherent cost estimation, and at a prioritization of the sites within the summer 2010.

physics.ins-det↗

arXiv2009

Geiger mode APD's for the underground cosmic ray experiment EMMA

Multi-pixel photodiodes operating in a limited Geiger mode will be used for photoreadout of scintillator counters in underground cosmic ray experiment EMMA. Main parameters of photodiodes and the performance of EMMA scintillator counters are presented.

physics.ins-det↗

arXiv2009

Multi-pixel Geiger-mode avalanche photodiode and wavelength shifting fibre readout of plastic scintillator counters of the EMMA underground experiment

The results of a development of a scintillator counter with wavelength shifting (WLS) fibre and a multi-pixel Geiger-mode avalanche photodiode readout are presented. The photodiode has a metal-resistor-semiconductor layered structure and operates in the limited Geiger mode. The scintillator counter has been developed for the EMMA underground cosmic ray experiment.

physics.ins-det↗

arXiv2008

On the level of background in underground muon measurements with plastic scintillator counters

In this short note we present results of background measurements carried out with a polystyrene based cast plastic 12.0x12.0x3.0 cm^3 size scintillator counter with a wavelength shifting fibre and a multi-pixel Geiger mode avalanche photodiode readout in the Baksan underground laboratory at a depth of 200 meters of water equivalent. The total counting rate of the scintillator counter measured at this depth and at a threshold corresponding to ~0.37 of a minimum ionizing particle is approximately 1.3 Hz.

physics.ins-det↗

arXiv2007

Large underground, liquid based detectors for astro-particle physics in Europe: scientific case and prospects

This document reports on a series of experimental and theoretical studies conducted to assess the astro-particle physics potential of three future large-scale particle detectors proposed in Europe as next generation underground observatories. The proposed apparatus employ three different and, to some extent, complementary detection techniques: GLACIER (liquid Argon TPC), LENA (liquid scintillator) and MEMPHYS (\WC), based on the use of large mass of liquids as active detection media. The results of these studies are presented along with a critical discussion of the performance attainable by the three proposed approaches coupled to existing or planned underground laboratories, in relation to open and outstanding physics issues such as the search for matter instability, the detection of astrophysical- and geo-neutrinos and to the possible use of these detectors in future high-intensity neutrino beams.

hep-ph↗

arXiv2005

EMMA - A New Underground Cosmic-Ray Experiment

A new type of cosmic-ray experiment is under construction in the Pyhäsalmi mine in the underground laboratory of the University of Oulu, Finland. It aims to study the composition of cosmic rays at and above the knee region. The experiment, called EMMA, will cover approximately 150 square-metres of detector area. The array is capable of measuring the multiplicity and the lateral distribution of underground muons, and the arrival direction of the air shower. The full-size detector is expected to run by the end of 2007.

astro-ph↗