arXiv subjects

M. -H. Schune

Publications and source records attributed to M. -H. Schune.

10 recordsLinked to original sources

arXiv2020

SoLid: A short baseline reactor neutrino experiment

The SoLid experiment, short for Search for Oscillations with a Lithium-6 detector, is a new generation neutrino experiment which tries to address the key challenges for high precision reactor neutrino measurements at very short distances from a reactor core and with little or no overburden. The primary goal of the SoLid experiment is to perform a precise measurement of the electron antineutrino energy spectrum and flux and to search for very short distance neutrino oscillations as a probe of eV-scale sterile neutrinos. This paper describes the SoLid detection principle, the mechanical design and the construction of the detector. It then reports on the installation and commissioning on site near the BR2 reactor, Belgium, and finally highlights its performance in terms of detector response and calibration.

physics.ins-det↗

arXiv2019

Commissioning and Operation of the Readout System for the SoLid Neutrino Detector

The SoLid experiment aims to measure neutrino oscillation at a baseline of 6.4 m from the BR2 nuclear reactor in Belgium. Anti-neutrinos interact via inverse beta decay (IBD), resulting in a positron and neutron signal that are correlated in time and space. The detector operates in a surface building, with modest shielding, and relies on extremely efficient online rejection of backgrounds in order to identify these interactions. A novel detector design has been developed using 12800 5 cm cubes for high segmentation. Each cube is formed of a sandwich of two scintillators, PVT and 6LiF:ZnS(Ag), allowing the detection and identification of positrons and neutrons respectively. The active volume of the detector is an array of cubes measuring 80x80x250 cm (corresponding to a fiducial mass of 1.6 T), which is read out in layers using two dimensional arrays of wavelength shifting fibres and silicon photomultipliers, for a total of 3200 readout channels. Signals are recorded with 14 bit resolution, and at 40 MHz sampling frequency, for a total raw data rate of over 2 Tbit/s. In this paper, we describe a novel readout and trigger system built for the experiment, that satisfies requirements on: compactness, low power, high performance, and very low cost per channel. The system uses a combination of high price-performance FPGAs with a gigabit Ethernet based readout system, and its total power consumption is under 1 kW. The use of zero suppression techniques, combined with pulse shape discrimination trigger algorithms to detect neutrons, results in an online data reduction factor of around 10000. The neutron trigger is combined with a large per-channel history time buffer, allowing for unbiased positron detection. The system was commissioned in late 2017, with successful physics data taking established in early 2018.

physics.ins-det↗

arXiv2018

Development of a Quality Assurance Process for the SoLid Experiment

The SoLid experiment has been designed to search for an oscillation pattern induced by a light sterile neutrino state, utilising the BR2 reactor of SCK$\bullet$CEN, in Belgium. The detector leverages a new hybrid technology, utilising two distinct scintillators in a cubic array, creating a highly segmented detector volume. A combination of 5 cm cubic polyvinyltoluene cells, with $^6$LiF:ZnS(Ag) sheets on two faces of each cube, facilitate reconstruction of the neutrino signals. % The polyvinyltoluene scintillator is used as an $\overlineν_e$ target for the inverse beta decay of ($\overlineν_e + p \rightarrow e^{+}+n$), with the $^6$LiF:ZnS(Ag) sheets used for associated neutron detection. Scintillation signals are read out by a network of wavelength shifting fibres connected to multipixel photon counters. Whilst the high granularity provides a powerful toolset to discriminate backgrounds; by itself the segmentation also represents a challenge in terms of homogeneity and calibration, for a consistent detector response. The search for this light sterile neutrino implies a sensitivity to distortions of around $\mathcal{O}$(10)\% in the energy spectrum of reactor $\overlineν_e$. Hence, a very good neutron detection efficiency, light yield and homogeneous detector response are critical for data validation. The minimal requirements for the SoLid physics program are a light yield and a neutron detection efficiency larger than 40 PA/MeV/cube and 50 \% respectively. In order to guarantee these minimal requirements, the collaboration developed a rigorous quality assurance process for all 12800 cubic cells of the detector. To carry out the quality assurance process, an automated calibration system called CALIPSO was designed and constructed.

physics.ins-det↗

arXiv2018

Optimisation of the scintillation light collection and uniformity for the SoLid experiment

This paper presents a comprehensive optimisation study to maximise the light collection efficiency of scintillating cube elements used in the SoLid detector. Very short baseline reactor experiments, like SoLid, look for active to sterile neutrino oscillation signatures in the anti-neutrino energy spectrum as a function of the distance to the core and energy. Performing a precise search requires high light yield of the scintillating elements and uniformity of the response in the detector volume. The SoLid experiment uses an innovative hybrid technology with two different scintillators: polyvinyltoluene scintillator cubes and $^6$LiF:ZnS(Ag) screens. A precision test bench based on a $^{207}$Bi calibration source has been developed to study improvements on the energy resolution and uniformity of the prompt scintillation signal of antineutrino interactions. A trigger system selecting the 1~MeV conversion electrons provides a Gaussian energy peak and allows for precise comparisons of the different detector configurations that were considered to improve the SoLid detector light collection. The light collection efficiency is influenced by the choice of wrapping material, the position of the $^6$LiF:ZnS(Ag) screen, the type of fibre, the number of optical fibres and the type of mirror at the end of the fibre. This study shows that large gains in light collection efficiency are possible compared to the SoLid SM1 prototype. The light yield for the SoLid detector is expected to be at least 52$\pm$2 photo-avalanches per MeV per cube, with a relative non-uniformity of 6 %, demonstrating that the required energy resolution of at least 14 % at 1 MeV can be achieved.

physics.ins-det↗

arXiv2018

Performance of a full scale prototype detector at the BR2 reactor for the SoLid experiment

The SoLid collaboration has developed a new detector technology to detect electron anti-neutrinos at close proximity to the Belgian BR2 reactor at surface level. A 288$\,$kg prototype detector was deployed in 2015 and collected data during the operational period of the reactor and during reactor shut-down. Dedicated calibration campaigns were also performed with gamma and neutron sources. This paper describes the construction of the prototype detector with a high control on its proton content and the stability of its operation over a period of several months after deployment at the BR2 reactor site. All detector cells provide sufficient light yields to achieve a target energy resolution of better than 20%/$\sqrt{E(MeV)}$. The capability of the detector to track muons is exploited to equalize the light response of a large number of channels to a precision of 3% and to demonstrate the stability of the energy scale over time. Particle identification based on pulse-shape discrimination is demonstrated with calibration sources. Despite a lower neutron detection efficiency due to triggering constraints, the main backgrounds at the reactor site were determined and taken into account in the shielding strategy for the main experiment. The results obtained with this prototype proved essential in the design optimization of the final detector. This paper is dedicated to our SCK$\cdot$CEN colleague, Edgar Koonen, who passed away unexpectedly in 2017. Edgar was part of the SoLid collaboration since its inception and his efforts were vital to get the experiment started. He will be duly missed.

physics.ins-det↗

arXiv2017

A novel segmented-scintillator antineutrino detector

The next generation of very-short-baseline reactor experiments will require compact detectors operating at surface level and close to a nuclear reactor. This paper presents a new detector concept based on a composite solid scintillator technology. The detector target uses cubes of polyvinyltoluene interleaved with $^6$LiF:ZnS(Ag) phosphor screens to detect the products of the inverse beta decay reaction. A multi-tonne detector system built from these individual cells can provide precise localisation of scintillation signals, making efficient use of the detector volume. Monte Carlo simulations indicate that a neutron capture efficiency of over 70% is achievable with a sufficient number of $^6$LiF:ZnS(Ag) screens per cube and that an appropriate segmentation enables a measurement of the positron energy which is not limited by gamma-ray leakage. First measurements of a single cell indicate that a very good neutron-gamma discrimination and high neutron detection efficiency can be obtained with adequate triggering techniques. The light yield from positron signals has been measured, showing that an energy resolution of 14%/$\sqrt{E({\mathrm{MeV}})}$ is achievable with high uniformity. A preliminary neutrino signal analysis has been developed, using selection criteria for pulse shape, energy, time structure and energy spatial distribution and showing that an antineutrino efficiency of 40% can be achieved. It also shows that the fine segmentation of the detector can be used to significantly decrease both correlated and accidental backgrounds.

physics.ins-det↗

arXiv2013

The LHCb Trigger and its Performance in 2011

This paper presents the design of the LHCb trigger and its performance on data taken at the LHC in 2011. A principal goal of LHCb is to perform flavour physics measurements, and the trigger is designed to distinguish charm and beauty decays from the light quark background. Using a combination of lepton identification and measurements of the particles' transverse momenta the trigger selects particles originating from charm and beauty hadrons, which typically fly a finite distance before decaying. The trigger reduces the roughly 11\,MHz of bunch-bunch crossings that contain at least one inelastic $pp$ interaction to 3\,kHz. This reduction takes place in two stages; the first stage is implemented in hardware and the second stage is a software application that runs on a large computer farm. A data-driven method is used to evaluate the performance of the trigger on several charm and beauty decay modes.

hep-ex↗

arXiv2006

Feasibility study for a model independent measurement of 2$β+ γ$ in $B^0$ decays using $D^- K^0 π^+$ final states

In this paper we present a feasibility study for measuring the combination of the Unitarity Triangle angle 2$β+γ$ with a time dependent Dalitz analysis in $B^0$ decays using $D^- K^0 π^+$ final states following the method proposed in [1]. For this study we build a model for this decay using the latest experimental information and we investigate the possibility of fitting together with 2$β+γ$ all the relevant strong amplitudes and phases of the decay model. [1] R. Aleksan, T.C. Petersen and A. Soffer, Phys. Rev. D67 (2003) 096002 [hep-ph/0209194].

hep-ph↗

arXiv2006

Heavy Flavours and CP Violation

Recent results on Heavy Flavours and CP violation are presented. After a short introduction a taste of K and D results is given. In a third part results on Vtd and Vts are summaryzed including BBbar mixing results and Bd radiative decays. A summary of Vcb and Vub measurements is presented in the fourth part. In the next section CP violation measurements in the Bd sector are shown. Finally in the last part the overall status of the determination of the CKM matrix is presented both in the context of the Standard Model and in the context of New Physics.

hep-ex↗

arXiv2000

Physics results from BABAR and prospects

The BABAR experiment has been taking data since about one year. Physics results, complementary to those described by G.Sciolla elsewhere in these Proceedings, are presented: various measurements of the neutral and charged B mesons lifetimes, the B^0 mixing frequency, the mistag fractions, and the B --> D_s^(*) X and B^0 --> D_s^(*)+ D^* branching ratios. Some prospects for the close future are shown. All the numbers given here are preliminary.

hep-ex↗