arXiv subjects

Jonas Rademacker

Publications and source records attributed to Jonas Rademacker.

At least 19 recordsLinked to original sources

arXiv2025

Luminosity measurement with the LHCb RICH detectors in Run 3

The LHCb Ring-Imaging Cherenkov detectors are built to provide charged hadron identification over a large range of momentum. The upgraded detectors are also capable of providing an independent measurement of the luminosity for the LHCb experiment during LHC Run 3. The modelling of the opto-electronics chain, the application of the powering strategy during operations, the calibration procedures and the proof of principle of a novel technique for luminosity determination are presented. In addition, the preliminary precision achieved during the 2023 data-taking year for real-time and offline luminosity measurements is reported.

hep-ex↗

arXiv2023

A novel unbinned model-independent method to measure the CKM angle $\gamma$ in $B^{\pm} \to DK^{\pm}$ decays with optimised precision

We present a novel unbinned method to combine $B^{\pm} \to DK^{\pm}$ and charm threshold data for the amplitude-model unbiased measurement of the CKM angle gamma in cases where the D meson decays to a three-body final state. The new unbinned approach avoids any kind of integration over the D Dalitz plot, to make optimal use the available information. We verify the method with simulated signal data where the D decays to $K_S \pi^+ \pi^-$. Using realistic sample sizes, we find that the new method reaches the statistical precision on gamma of an unbinned model-dependent fit, i.e. as good as possible and better than the widely used model-independent binned approach, without suffering from biases induced by a mis-modeled D decay amplitude.

hep-ph↗

arXiv2022

Performance of a prototype TORCH time-of-flight detector

TORCH is a novel time-of-flight detector, designed to provide charged particle identification of pions, kaons and protons in the momentum range 2-20 GeV/c over a 9.5 m flight path. A detector module, comprising a 10mm thick quartz plate, provides a source of Cherenkov photons which propagate via total internal reflection to one end of the plate. Here, the photons are focused onto an array of custom-designed Micro-Channel Plate Photo-Multiplier Tubes (MCP-PMTs) which measure their positions and arrival times. The target time resolution per photon is 70 ps which, for 30 detected photons per charged particle, results in a 10-15 ps time-of-flight resolution. A 1.25 m length TORCH prototype module employing two MCP-PMTs has been developed, and tested at the CERN PS using a charged hadron beam of 8 GeV/c momentum. The construction of the module, the properties of the MCP-PMTs and the readout electronics are described. Measurements of the collected photon yields and single-photon time resolutions have been performed as a function of particle entry points on the plate and compared to expectations. These studies show that the performance of the TORCH prototype approaches the design goals for the full-scale detector.

physics.ins-det↗

arXiv2022

Picosecond timing of charged particles using the TORCH detector

TORCH is a large-area, high-precision time-of-flight (ToF) detector designed to provide charged-particle identification in the 2-20 GeV$/c$ momentum range. Prompt Cherenkov photons emitted by charged hadrons as they traverse a 10mm quartz radiator are propagated to the periphery of the detector, where they are focused onto an array of micro-channel plate photomultiplier tubes (MCP-PMTs). The position and arrival times of the photons are used to infer the particles' time of entry in the radiator, to identify hadrons based on their ToF. The MCP-PMTs were developed with an industrial partner to satisfy the stringent requirements of the TORCH detector. The requirements include a finely segmented anode, excellent time resolution, and a long lifetime. Over an approximately 10m flight distance, the difference in ToF between a kaon and a pion with 10GeV$/c$ momentum is 35ps, leading to a 10-15ps per track timing resolution requirement. On average 30 photons per hadron are detected, which translates to a single-photon time resolution of 70ps. The TORCH research and development program aims to demonstrate the validity of the detector concept through laboratory and beam tests, results from which are presented. A timing resolution of 70-100ps was reached in beam tests, approaching the TORCH design goal. Laboratory timing tests consist of operating the MCP-PMTs coupled to the TORCH readout electronics. A time resolution of about 50ps was measured, meeting the TORCH target timing resolution.

physics.ins-det↗

arXiv2020

Studying the potential of Graphcore IPUs for applications in Particle Physics

This paper presents the first study of Graphcore's Intelligence Processing Unit (IPU) in the context of particle physics applications. The IPU is a new type of processor optimised for machine learning. Comparisons are made for neural-network-based event simulation, multiple-scattering correction, and flavour tagging, implemented on IPUs, GPUs and CPUs, using a variety of neural network architectures and hyperparameters. Additionally, a K\'{a}lm\'{a}n filter for track reconstruction is implemented on IPUs and GPUs. The results indicate that IPUs hold considerable promise in addressing the rapidly increasing compute needs in particle physics.

physics.comp-ph↗

arXiv2019

Beam tests of a large-scale TORCH time-of-flight demonstrator

The TORCH time-of-flight detector is designed to provide particle identification in the momentum range 2-10 GeV/c over large areas. The detector exploits prompt Cherenkov light produced by charged particles traversing a 10 mm thick quartz plate. The photons propagate via total internal reflection and are focused onto a detector plane comprising position-sensitive Micro-Channel Plate Photo-Multiplier Tubes (MCP-PMT) detectors. The goal is to achieve a single-photon timing resolution of 70 ps, giving a timing precision of 15 ps per charged particle by combining the information from around 30 detected photons. The MCP-PMT detectors have been developed with a commercial partner (Photek Ltd, UK), leading to the delivery of a square tube of active area 53 $\times$ 53mm$^2$ with a granularity of 8 $\times$ 128 pixels equivalent. A large-scale demonstrator of TORCH, having a quartz plate of dimensions 660 $\times$ 1250 $\times$ 10 mm$^3$ and read out by a pair of MCP-PMTs with custom readout electronics, has been verified in a test beam campaign at the CERN PS. Preliminary results indicate that the required performance is close to being achieved. The anticipated performance of a full-scale TORCH detector at the LHCb experiment is presented.

physics.ins-det↗

arXiv2018

Status of the TORCH time-of-flight project

TORCH is a time-of-flight detector, designed to provide charged pi/K particle identification up to a momentum of 10 GeV/c for a 10 m flight path. To achieve this level of performance, a time resolution of 15 ps per incident particle is required. TORCH uses a plane of quartz of 1 cm thickness as a source of Cherenkov photons, which are then focussed onto square Micro-Channel Plate Photomultipliers (MCP-PMTs) of active area 53 x 53 mm^2, segmented into 8 x 128 pixels equivalent. A small-scale TORCH demonstrator with a customised MCP-PMT and associated readout electronics has been successfully operated in a 5 GeV/c mixed pion/proton beam at the CERN PS facility. Preliminary results indicate that a single-photon resolution better than 100 ps can be achieved. The expected performance of a full-scale TORCH detector for the Upgrade II of the LHCb experiment is also discussed.

physics.ins-det↗

arXiv2018

TORCH: a large area time-of-flight detector for particle identification

TORCH is a time-of-flight detector that is being developed for the Upgrade II of the LHCb experiment, with the aim of providing charged particle identification over the momentum range 2-10 GeV/c. A small-scale TORCH demonstrator with customised readout electronics has been operated successfully in beam tests at the CERN PS. Preliminary results indicate that a single-photon resolution better than 100 ps can be achieved.

physics.ins-det↗

arXiv2018

Testbeam studies of a TORCH prototype detector

TORCH is a novel time-of-flight detector that has been developed to provide charged-particle identification between 2 and 10 GeV/c momentum. TORCH combines arrival times from multiple Cherenkov photons produced within a 10 mm-thick quartz radiator plate, to achieve a 15 ps time-of-flight resolution per incident particle. A customised Micro-Channel Plate photomultiplier tube (MCP-PMT) and associated readout system utilises an innovative charge-sharing technique between adjacent pixels to obtain the necessary 70 ps time resolution of each Cherenkov photon. A five-year R\&D programme has been undertaken, culminating in the construction of a small-scale prototype TORCH module. In testbeams at CERN, this prototype operated successfully with customised electronics and readout system. A full analysis chain has been developed to reconstruct the data and to calibrate the detector. Results are compared to those using a commercial Planacon MCP-PMT, and single photon resolutions approaching 80 ps have been achieved. The photon counting efficiency was found to be in reasonable agreement with a GEANT4 Monte Carlo simulation of the detector. The small-scale demonstrator is a precursor to a full-scale TORCH module (with a radiator plate of $660\times1250\times10~{\rm mm^3}$), which is currently under construction.

physics.ins-det↗

arXiv2017

Model-independent determination of the strong phase difference between $D^0$ and $\bar{D}^0 \to\pi^+\pi^-\pi^+\pi^-$ amplitudes

For the first time, the strong phase difference between $D^0$ and $\bar{D}^0\to\pi^+\pi^-\pi^+\pi^-$ amplitudes is determined in bins of the decay phase space. The measurement uses $818\,\mathrm{pb}^{-1}$ of $e^+e^-$ collision data that is taken at the $\psi(3770)$ resonance and collected by the CLEO-c experiment. The measurement is important for the determination of the $C P$-violating phase $\gamma$ in $B^{\pm}\to D K^{\pm}$ (and similar) decays , where the $D$ meson (which represents a superposition of $D^0$ and $\bar{D}^0$) subsequently decays to $\pi^+\pi^-\pi^+\pi^-$. To obtain optimal sensitivity to $\gamma$, the phase space of the $D \to \pi^+\pi^-\pi^+\pi^-$ decay is divided into bins based on a recent amplitude model of the decay. Although an amplitude model is used to define the bins, the measurements obtained are model-independent. The $CP$-even fraction of the $D \to \pi^+\pi^-\pi^+\pi^-$ decay is determined to be $F_{+}^{4\pi} = 0.769 \pm 0.021 \pm 0.010$, where the uncertainties are statistical and systematic, respectively. Using simulated $B^{\pm}\to D K^{\pm}, D \to \pi^+\pi^-\pi^+\pi^-$ decays, it is estimated that by the end of the current LHC run, the LHCb experiment could determine $\gamma$ from this decay mode with an uncertainty of $(\pm10\pm7)^\circ$, where the first uncertainty is statistical based on estimated LHCb event yields, and the second is due to the uncertainties on the parameters determined in this paper.

hep-ex↗

arXiv2017

Amplitude Analyses of $D^0 \to {\pi^+\pi^-\pi^+\pi^-}$ and $D^0 \to {K^+K^-\pi^+\pi^-}$ Decays

The resonant substructure of $D^0 \to \pi^+\pi^-\pi^+\pi^-$ decays is studied using data collected by the CLEO-c detector. An amplitude analysis is performed in order to disentangle the various intermediate state contributions. To limit the model complexity a data driven regularization procedure is applied. The prominent contributions are the decay modes $D^0\to a_1(1260)^+\pi^-$, $D^0\to \sigma f_0(1370)$ and $D^0 \to \rho(770)^0 \rho(770)^0$. The broad resonances $a_1(1260)^+$, $\pi(1300)^+$ and $a_1(1640)^+$ are studied in detail, including quasi-model-independent parametrizations of their lineshapes. The mass and width of the $a_1(1260)^+$ meson are determined to be $m_{a_1(1260)^+}=[1225\pm9\text{(stat)}\pm17\text{(syst)}\pm10\text{(model)}]\text{MeV}/c^2$ and $\Gamma_{a_1(1260)^+}=[430\pm24\text{(stat)}\pm25 \text{(syst)}\pm18\text{(model)}]\text{MeV}$. The amplitude model of $D^0\to K^+K^-\pi^+\pi^-$ decays obtained from CLEO II.V, CLEO III, and CLEO-c data is revisited with improved lineshape parametrizations. The largest components are the decay modes $D^0\to\phi(1020)\rho(770)^0$, $D^0 \to K_1(1270)^+ K^-$ and $D^0 \to K(1400)^+ K^-$. The fractional $CP$-even content of the decay $D^0\to \pi^+\pi^-\pi^+\pi^-$ is calculated from the amplitude model to be $F_+^{4\pi}=[72.9\pm0.9\text{(stat)}\pm1.5\text{(syst)}\pm1.0\text{(model)}]\%$, consistent with that obtained from a previous model-independent measurement. For $D^0 \to K^+K^-\pi^+\pi^-$ decays, the $CP$-even fraction is measured for the first time and found to be $F_+^{KK\pi\pi}=[75.3\pm1.8\text{(stat)}\pm3.3\text{(syst)}\pm3.5\text{(model)}]\%$. The global decay rate asymmetries between $D^0$ and $\overline{D}^0$ decays are measured to be $A^{4\pi}_{CP}=[+0.54\pm1.04\text{(stat)}\pm0.51\text{(syst)}]\%$ and $A^{KK\pi\pi}_{CP}=[+1.84\pm1.74\text{(stat)}\pm0.30\text{(syst)}]\%$.

hep-ex↗

arXiv2016

Amplitude analysis of $D^{0} \rightarrow \pi^{+} \pi^{-} \pi^{+} \pi^{-}$ decays using CLEO-c data

The resonant substructure of the decay $D^{0} \rightarrow \pi^{+} \pi^{-} \pi^{+} \pi^{-}$ is studied by performing a full five-dimensional amplitude analysis. Preliminary results based on data collected by the CLEO-c detector are presented. This is the largest dataset of $D^{0} \rightarrow \pi^{+} \pi^{-} \pi^{+} \pi^{-}$ decays analysed in this way to-date. The two most significant contributions are $D^{0} \rightarrow a_{1}(1260)^{+} \pi^{-}$ and $D^{0} \rightarrow \rho(770)^{0}\rho(770)^{0}$. The line shape, mass and width of the $a_{1}(1260)$ resonance are determined, and model-independent studies of the line shapes of several resonant contributions are preformed.

hep-ex↗

arXiv2016

Summary of the 2015 LHCb workshop on multi-body decays of D and B mesons

This document contains a summary of the LHCb workshop on multi-body decays of D and B mesons, held at CBPF, Rio de Janeiro, in July 2015. The workshop was focused on issues related to amplitude analysis of three- and four-body hadronic decays. In addition to selected LHCb results, contributions from guest theorists are included.

hep-ex↗

arXiv2014

Model independent determination of the CKM phase $\gamma$ using input from $D^0-\bar{D}^0$ mixing

We present a new, amplitude model-independent method to measure the CP violation parameter $\gamma$ in $B^- \to DK^-$ and related decays. Information on charm interference parameters, usually obtained from charm threshold data, is obtained from charm mixing. By splitting the phase space of the $D$ meson decay into several bins, enough information can be gained to measure $\gamma$ without input from the charm threshold. We demonstrate the feasibility of this approach with a simulation study of $B^- \to DK^-$ with $D \to K^+ \pi^- \pi^+ \pi^-$. We compare the performance of our novel approach to that of a previously proposed binned analysis which uses charm interference parameters obtained from threshold data. While both methods provide useful constraints, the combination of the two by far outperforms either of them applied on their own. Such an analysis would provide a highly competitive measurement of $\gamma$. Our simulation studies indicate, subject to assumptions about data yields and the amplitude structure of $D^0 \to K^+ \pi^- \pi^+ \pi^-$, a statistical uncertainty on $\gamma$ of $\sim 12^{\circ}$ with existing data and $\sim 4^{\circ}$ for the LHCb-upgrade.

hep-ph↗

arXiv2013

Measuring CP violation in 3- and 4-body decays

Multibody charm decays have a rich phenomenology and potentially unique sensitivity to CP violation. In these proceedings we discuss recent results, challenges and prospects in searches for CP violation in three and four body charm decays.

hep-ex↗

arXiv2013

Charm mixing as input for model-independent determinations of the CKM phase gamma

The coherence factor and average strong phase difference of D0 and D0bar decay amplitudes to the same final state play an important role in the precision determination of the CKM parameter gamma using B- -> DK- and related decay modes. So far, this important input from the charm sector could only be obtained from measurements based on quantum-correlated DDbar pairs produced at the charm threshold. We propose to constrain these parameters using charm mixing, using the large charm samples available at the B factories and LHCb. We demonstrate for the example of D0->Kpipipi that a substantial improvement in the precision of the coherence factor and average strong phase difference can be obtained with this method, using existing data.

hep-ph↗

arXiv2010

Non-leptonic D0, D+, and Ds Branching Fractions

Non-leptonic charm decays provide insights into both electro-weak and strong dynamics. This includes the study of long-distance hadronic effects, the approximate symmetries of strong interactions, and precision tests of the Standard Model. In these proceedings we summarise recent results in non-leptonic branching fraction measurements of D mesons, including measurements of relative and absolute branching fractions in inclusive and exclusive modes, radiative decays, and measurements of direct CP violation.

hep-ex↗

arXiv2009

Dalitz Analyses in Charm

Dalitz analyses in charm give access to both magnitudes and phases of the charm decay amplitudes. They play a significant role in charm-mixing measurements, in the measurement of the CP-violating phase gamma in B decays to charm, and in the analysis of light meson resonances. We review recent results in all three categories.

hep-ex↗