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D. vom Bruch

Publications and source records attributed to D. vom Bruch.

14 recordsLinked to original sources
arXiv2021

Technical design of the phase I Mu3e experiment

The Mu3e experiment aims to find or exclude the lepton flavour violating decay $μ\rightarrow eee$ at branching fractions above $10^{-16}$. A first phase of the experiment using an existing beamline at the Paul Scherrer Institute (PSI) is designed to reach a single event sensitivity of $2\cdot 10^{-15}$. We present an overview of all aspects of the technical design and expected performance of the phase~I Mu3e detector. The high rate of up to $10^{8}$ muon decays per second and the low momenta of the decay electrons and positrons pose a unique set of challenges, which we tackle using an ultra thin tracking detector based on high-voltage monolithic active pixel sensors combined with scintillating fibres and tiles for precise timing measurements.

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

Allen: A high level trigger on GPUs for LHCb

We describe a fully GPU-based implementation of the first level trigger for the upgrade of the LHCb detector, due to start data taking in 2021. We demonstrate that our implementation, named Allen, can process the 40 Tbit/s data rate of the upgraded LHCb detector and perform a wide variety of pattern recognition tasks. These include finding the trajectories of charged particles, finding proton-proton collision points, identifying particles as hadrons or muons, and finding the displaced decay vertices of long-lived particles. We further demonstrate that Allen can be implemented in around 500 scientific or consumer GPU cards, that it is not I/O bound, and can be operated at the full LHC collision rate of 30 MHz. Allen is the first complete high-throughput GPU trigger proposed for a HEP experiment.

physics.ins-det↗
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

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

Irradiation study of a fully monolithic HV-CMOS pixel sensor design in AMS 180 nm

High-Voltage Monolithic Active Pixel Sensors (HV-MAPS) based on the 180 nm HV-CMOS process have been proposed to realize thin, fast and highly integrated pixel sensors. The MuPix7 prototype, fabricated in the commercial AMS H18 process, features a fully integrated on-chip readout, i.e. hit-digitization, zero suppression and data serialization. It is the first fully monolithic HV-CMOS pixel sensor that has been tested for the use in high irradiation environments like HL-LHC. We present results from laboratory and test beam measurements of MuPix7 prototypes irradiated with neutrons (up to $5.0\cdot10^{15}{\,\rm{n}_{\rm{eq}}/cm^2}$) and protons (up to $7.8\cdot 10^{15} \,\rm{protons}/cm^2$) and compare the performance with non-irradiated sensors. Efficiencies well above 90 % at noise rates below 200 Hz per pixel are measured. A time resolution better than 22 ns is measured for all tested settings and sensors, even at the highest irradiation fluences. The data transmission at 1.25 Gbit/s and the on-chip PLL remain fully functional.

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↗
arXiv2016

The MuPix Telescope: A Thin, high Rate Tracking Telescope

The MuPix Telescope is a particle tracking telescope, optimized for tracking low momentum particles and high rates. It is based on the novel High-Voltage Monolithic Active Pixel Sensors (HV-MAPS), designed for the Mu3e tracking detector. The telescope represents a first application of the HV-MAPS technology and also serves as test bed of the Mu3e readout chain. The telescope consists of up to eight layers of the newest prototypes, the MuPix7 sensors, which send data self-triggered via fast serial links to FPGAs, where the data is time-ordered and sent to the PC. A particle hit rate of 1 MHz per layer could be processed. Online tracking is performed with a subset of the incoming data. The general concept of the telescope, chip architecture, readout concept and online reconstruction are described. The performance of the sensor and of the telescope during test beam measurements are presented.

physics.ins-det↗
arXiv2016

MuPix7 - A fast monolithic HV-CMOS pixel chip for Mu3e

The MuPix7 chip is a monolithic HV-CMOS pixel chip, thinned down to 50 μm. It provides continuous self-triggered, non-shuttered readout at rates up to 30 Mhits/chip of 3x3 mm^2 active area and a pixel size of 103x80 μm^2. The hit efficiency depends on the chosen working point. Settings with a power consumption of 300 mW/cm^2 allow for a hit efficiency >99.5%. A time resolution of 14.2 ns (Gaussian sigma) is achieved. Latest results from 2016 test beam campaigns are shown.

physics.ins-det↗
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↗