Pub Date : 2026-06-01Epub Date: 2026-01-27DOI: 10.1016/j.nima.2026.171318
Artur Kalinowski, Wiktor Matyszkiewicz
The quality of the invariant mass reconstruction of the di- system is crucial for searches and analyses of di- resonances. Due to the presence of neutrinos in the final state, the invariant mass cannot be calculated directly at hadron colliders, where the longitudinal momentum sum constraint cannot be applied. A number of approaches have been adopted to mitigate this issue. The most general approach uses Matrix Element (ME) integration for likelihood estimation, followed by invariant mass reconstruction as the value that maximizes the likelihood. However, this method has a significant computational cost due to the need for integration over the phase space of the decay products. We propose an algorithm that reduces the computational cost by two orders of magnitude while maintaining the invariant mass reconstruction resolution at a level comparable to that of the ME-based method. Moreover, we introduce additional features that allow the estimation of the uncertainty of the reconstructed mass and the kinematics of the initial leptons (e.g. their momenta).
{"title":"Efficient tau-pair invariant mass reconstruction with simplified matrix element techniques","authors":"Artur Kalinowski, Wiktor Matyszkiewicz","doi":"10.1016/j.nima.2026.171318","DOIUrl":"10.1016/j.nima.2026.171318","url":null,"abstract":"<div><div>The quality of the invariant mass reconstruction of the di-<span><math><mi>τ</mi></math></span> system is crucial for searches and analyses of di-<span><math><mi>τ</mi></math></span> resonances. Due to the presence of neutrinos in the final state, the <span><math><mrow><mi>τ</mi><mi>τ</mi></mrow></math></span> invariant mass cannot be calculated directly at hadron colliders, where the longitudinal momentum sum constraint cannot be applied. A number of approaches have been adopted to mitigate this issue. The most general approach uses Matrix Element (ME) integration for likelihood estimation, followed by invariant mass reconstruction as the value that maximizes the likelihood. However, this method has a significant computational cost due to the need for integration over the phase space of the decay products. We propose an algorithm that reduces the computational cost by two orders of magnitude while maintaining the invariant mass reconstruction resolution at a level comparable to that of the ME-based method. Moreover, we introduce additional features that allow the estimation of the uncertainty of the reconstructed mass and the kinematics of the initial <span><math><mi>τ</mi></math></span> leptons (e.g. their momenta).</div></div>","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1086 ","pages":"Article 171318"},"PeriodicalIF":1.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081866","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-06-01Epub Date: 2026-01-24DOI: 10.1016/j.nima.2026.171316
D. Shatilov
The original article Zhang et al. (2025) can be logically divided into two parts: (1) the selection of main parameters for monochromatization and (2) interaction region optics design; the comment pertains only to the first part. The authors of Zhang et al. (2025) state that “The purpose of this paper is to report on the development of realistic IR optics designs for monochromatization at the FCC-ee”. However, the proposed parameters do not seem very realistic and raise many questions; due to space limitations, we will only consider the most important ones.
原文章Zhang et al.（2025）在逻辑上可以分为两个部分：(1)单色化主要参数的选择和(2)相互作用区光学设计；评论只涉及第一部分。Zhang等人（2025）的作者指出，“本文的目的是报告FCC-ee单色化实际红外光学设计的发展”。然而，所提出的参数似乎不太现实，并提出了许多问题；由于篇幅限制，我们将只考虑最重要的。
{"title":"Comment on “Monochromatization interaction region optics design for direct s-channel Higgs production at FCC-ee”","authors":"D. Shatilov","doi":"10.1016/j.nima.2026.171316","DOIUrl":"10.1016/j.nima.2026.171316","url":null,"abstract":"<div><div>The original article Zhang et al. (2025) can be logically divided into two parts: (1) the selection of main parameters for monochromatization and (2) interaction region optics design; the comment pertains only to the first part. The authors of Zhang et al. (2025) state that “The purpose of this paper is to report on the development of realistic IR optics designs for monochromatization at the FCC-ee”. However, the proposed parameters do not seem very realistic and raise many questions; due to space limitations, we will only consider the most important ones.</div></div>","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1086 ","pages":"Article 171316"},"PeriodicalIF":1.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-06-01Epub Date: 2026-01-26DOI: 10.1016/j.nima.2026.171319
Xiushan Wang , Yunpeng Liu , Kang Wang , Ziyao Zeng , Xiaobin Tang
In this study, we report the fabrication and characterization of a prototype metal photocathode pulsed X-ray tube (MPPXT) integrated with a microchannel plate (MCP) structure. Key structural parameters of the X-ray tube were optimized using CST Particle Studio and the Non-dominated Sorting Genetic Algorithm II (NSGA-II), which we applied to guide the fabrication of the prototype. Au photocathodes with various deposition times were characterized, with a deposition time of 150 s yielding a maximum photocurrent of 20.45 nA. When the optimal Au photocathode was integrated into the prototype, the electron multiplication characteristics of both single- and dual-MCP configurations in an X-ray tube were systematically characterized for the first time. The single-MCP configuration at 1000 V achieved a tube current of 35 μA, with a current gain of ∼1.76 × 103. The dual-MCP configuration at 1800 V further improved the multiplication efficiency, producing a tube current of 223 μA with a gain of ∼1.17 × 104. Imaging experiments showed a minimum focal spot size of 0.27 × 0.47 mm, which was consistent with simulations. Moreover, the MPPXT achieved stable pulse modulation at 2 MHz. Thus, the proposed MPPXT exhibited enhanced output intensity and offered the advantage of convenient high-speed modulation. These results demonstrate that the proposed method is promising for applications in high-speed imaging, X-ray communication, and scintillator time-response measurements.
{"title":"Fabrication and performance testing of a metal photocathode pulsed X-ray tube prototype based on microchannel plate","authors":"Xiushan Wang , Yunpeng Liu , Kang Wang , Ziyao Zeng , Xiaobin Tang","doi":"10.1016/j.nima.2026.171319","DOIUrl":"10.1016/j.nima.2026.171319","url":null,"abstract":"<div><div>In this study, we report the fabrication and characterization of a prototype metal photocathode pulsed X-ray tube (MPPXT) integrated with a microchannel plate (MCP) structure. Key structural parameters of the X-ray tube were optimized using CST Particle Studio and the Non-dominated Sorting Genetic Algorithm II (NSGA-II), which we applied to guide the fabrication of the prototype. Au photocathodes with various deposition times were characterized, with a deposition time of 150 s yielding a maximum photocurrent of 20.45 nA. When the optimal Au photocathode was integrated into the prototype, the electron multiplication characteristics of both single- and dual-MCP configurations in an X-ray tube were systematically characterized for the first time. The single-MCP configuration at 1000 V achieved a tube current of 35 μA, with a current gain of ∼1.76 × 10<sup>3</sup>. The dual-MCP configuration at 1800 V further improved the multiplication efficiency, producing a tube current of 223 μA with a gain of ∼1.17 × 10<sup>4</sup>. Imaging experiments showed a minimum focal spot size of 0.27 × 0.47 mm, which was consistent with simulations. Moreover, the MPPXT achieved stable pulse modulation at 2 MHz. Thus, the proposed MPPXT exhibited enhanced output intensity and offered the advantage of convenient high-speed modulation. These results demonstrate that the proposed method is promising for applications in high-speed imaging, X-ray communication, and scintillator time-response measurements.</div></div>","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1086 ","pages":"Article 171319"},"PeriodicalIF":1.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146190893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-06-01Epub Date: 2026-02-05DOI: 10.1016/j.nima.2026.171366
Zilin Chen , Xiaoyu Li , Qing Guo , Hui Zhao , Zhouyu Zhao , Shutao Zhao , Wan Chen , Heting Li , Xiangchen Yang , Yuhui Li
During the tuning of the six-row magnetic array helical undulator's magnetic field, key challenges of gap dependence and X-position dependence are addressed. For gap dependence, the target parameters are the RMS deviations of the second-order field integrals ( & ). Adjusting pole heights alone is proved insufficient. A solution is implemented by magnetic shimming on the poles and utilizing a staggered shimming concept on magnetic blocks. This successfully controls both and within 2000 Gs cm2 across the entire working gap range. For X-position dependence across a ±13 mm range, the focus is on the first/second-order integrals and multipole fields at the outlet. The limited longitudinal space makes magic fingers alone inadequate for compensation. Therefore, two configurations of shimming are introduced to pre-compensate for the dependence, followed by final adjustments with magic fingers. This hybrid approach effectively reduces multipole fields and corrects for defects in the off-axis field.
{"title":"Magnetic shimming schemes for a six-row permanent magnet based helical undulator","authors":"Zilin Chen , Xiaoyu Li , Qing Guo , Hui Zhao , Zhouyu Zhao , Shutao Zhao , Wan Chen , Heting Li , Xiangchen Yang , Yuhui Li","doi":"10.1016/j.nima.2026.171366","DOIUrl":"10.1016/j.nima.2026.171366","url":null,"abstract":"<div><div>During the tuning of the six-row magnetic array helical undulator's magnetic field, key challenges of gap dependence and X-position dependence are addressed. For gap dependence, the target parameters are the RMS deviations of the second-order field integrals (<span><math><mrow><mi>R</mi><mi>M</mi><mi>S</mi><mi>I</mi><mn>2</mn><mi>x</mi></mrow></math></span> & <span><math><mrow><mi>R</mi><mi>M</mi><mi>S</mi><mi>I</mi><mn>2</mn><mi>y</mi></mrow></math></span>). Adjusting pole heights alone is proved insufficient. A solution is implemented by magnetic shimming on the poles and utilizing a staggered shimming concept on <span><math><mrow><mi>B</mi><mi>x</mi></mrow></math></span> magnetic blocks. This successfully controls both <span><math><mrow><mi>R</mi><mi>M</mi><mi>S</mi><mi>I</mi><mn>2</mn><mi>x</mi></mrow></math></span> and <span><math><mrow><mi>R</mi><mi>M</mi><mi>S</mi><mi>I</mi><mn>2</mn><mi>y</mi></mrow></math></span> within 2000 Gs cm<sup>2</sup> across the entire working gap range. For X-position dependence across a ±13 mm range, the focus is on the first/second-order integrals and multipole fields at the outlet. The limited longitudinal space makes magic fingers alone inadequate for compensation. Therefore, two configurations of shimming are introduced to pre-compensate for the dependence, followed by final adjustments with magic fingers. This hybrid approach effectively reduces multipole fields and corrects for defects in the off-axis field.</div></div>","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1086 ","pages":"Article 171366"},"PeriodicalIF":1.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146190881","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-06-01Epub Date: 2026-01-29DOI: 10.1016/j.nima.2026.171323
W. Hamdi , J. Crafts , H. Huang , Z. Huang , M. Kerver , M. Mathison , C. Ploen , A. Singh , T. Song , Y.P. Zhang , D. Adhikari , A. Ahmed , H. Albataineh , K. Aniol , A. Asaturyan , C. Ayerbe Gayoso , P. Bosted , E. Brash , A. Camsonne , J. Caylor , X. Zheng
The Neutral Particle Spectrometer (NPS) is an advanced calorimeter designed to measure neutral electromagnetic particles with high precision in energy, time, and position, under conditions of high luminosity and significant background. Integrated into the experimental setup of Hall C at Thomas Jefferson National Accelerator Facility, the NPS plays a critical role in studies of nucleon structure through exclusive and semi-inclusive reaction channels. This paper presents an assessment of the detector’s performance characteristics, specifically its energy and timing resolution, derived from elastic electron–proton scattering data. We report an energy resolution between 1.2% and 1.3% in the 4.5–7.3 GeV range, and an intrinsic timing resolution better than 200 ps for energies above 500 MeV. These results serve as a reference for current and future precision measurements in hadronic physics.
{"title":"Intrinsic energy and time resolution of the Jefferson Lab Hall C Neutral Particle Spectrometer","authors":"W. Hamdi , J. Crafts , H. Huang , Z. Huang , M. Kerver , M. Mathison , C. Ploen , A. Singh , T. Song , Y.P. Zhang , D. Adhikari , A. Ahmed , H. Albataineh , K. Aniol , A. Asaturyan , C. Ayerbe Gayoso , P. Bosted , E. Brash , A. Camsonne , J. Caylor , X. Zheng","doi":"10.1016/j.nima.2026.171323","DOIUrl":"10.1016/j.nima.2026.171323","url":null,"abstract":"<div><div>The Neutral Particle Spectrometer (NPS) is an advanced calorimeter designed to measure neutral electromagnetic particles with high precision in energy, time, and position, under conditions of high luminosity and significant background. Integrated into the experimental setup of Hall C at Thomas Jefferson National Accelerator Facility, the NPS plays a critical role in studies of nucleon structure through exclusive and semi-inclusive reaction channels. This paper presents an assessment of the detector’s performance characteristics, specifically its energy and timing resolution, derived from elastic electron–proton scattering data. We report an energy resolution between 1.2% and 1.3% in the 4.5–7.3 GeV range, and an intrinsic timing resolution better than 200 ps for energies above 500 MeV. These results serve as a reference for current and future precision measurements in hadronic physics.</div></div>","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1086 ","pages":"Article 171323"},"PeriodicalIF":1.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146070983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-06-01Epub Date: 2026-01-30DOI: 10.1016/j.nima.2026.171338
W.F. Rogers , A.N. Kuchera , T. Awal , T. Baumann , C. Capuano , D. Chrisman , M. Devlin , D. Flores Madrid , J. Glaze , O. Guarinello , P. Gueye , J. Hallett , B. Hassan , K.J. Kelly , O. Lucas , A. Maki , S. Mosby , A. Munroe , T. Redpath , A. Robinson , S. Winner
Plastic scintillator detectors are widely used in nuclear physics experiments and applications. The interpretation of the data often relies on simulation to understand the performance of the detectors and to assist with the analysis of decay energies and widths of neutron-rich nuclei. A neutron scattering experiment was conducted at the Los Alamos Neutron Science Center (LANSCE) to study neutrons scattering from H and C nuclei in plastic scintillators for neutrons with energy 20 to 400 MeV. The detector array consisted of a single detector bar serving as target, and a 45° ramp of detectors 2 m downstream. Results for three interaction observables, including scintillation light detected, kinetic energy distribution following the first scatter, and scattering angle, were compared with predictions from two Geant4-based simulation packages, referred to here as G4-Physics and MENATE_R. Agreement between simulation and data was best for events consisting of a single hit, and poorer for events consisting of two hits.
{"title":"Testing interaction simulations with 20–400 MeV neutron scattering data from plastic scintillators","authors":"W.F. Rogers , A.N. Kuchera , T. Awal , T. Baumann , C. Capuano , D. Chrisman , M. Devlin , D. Flores Madrid , J. Glaze , O. Guarinello , P. Gueye , J. Hallett , B. Hassan , K.J. Kelly , O. Lucas , A. Maki , S. Mosby , A. Munroe , T. Redpath , A. Robinson , S. Winner","doi":"10.1016/j.nima.2026.171338","DOIUrl":"10.1016/j.nima.2026.171338","url":null,"abstract":"<div><div>Plastic scintillator detectors are widely used in nuclear physics experiments and applications. The interpretation of the data often relies on simulation to understand the performance of the detectors and to assist with the analysis of decay energies and widths of neutron-rich nuclei. A neutron scattering experiment was conducted at the Los Alamos Neutron Science Center (LANSCE) to study neutrons scattering from H and C nuclei in plastic scintillators for neutrons with energy 20 to 400 MeV. The detector array consisted of a single detector bar serving as target, and a 45° ramp of detectors 2 m downstream. Results for three interaction observables, including scintillation light detected, kinetic energy distribution following the first scatter, and scattering angle, were compared with predictions from two Geant4-based simulation packages, referred to here as G4-Physics and MENATE_R. Agreement between simulation and data was best for events consisting of a single hit, and poorer for events consisting of two hits.</div></div>","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1086 ","pages":"Article 171338"},"PeriodicalIF":1.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146081865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-06-01Epub Date: 2026-02-02DOI: 10.1016/j.nima.2026.171355
Lin Zhou , Huanbo Feng , Zuke Feng , Difan Yi , Ran Chen , Kuan Liu , Lirong Xie , Qian Zhong , Jiangchuan Tuo , Tianyi Xiong , Fei Xie , Enwei Liang , Hongbang Liu
The Gas Microchannel Plate Pixel Detector (GMPD) is used in astrophysics for measuring X-ray polarization and serves as the prototype for the Low-Energy Polarization Detector (LPD) of the POLAR-2 project. During gamma-ray burst (GRB) observations, the incident flux can vary rapidly on short timescales, inducing charging-up effects that degrade gain stability. We characterize the chip-level charging-up behavior and quantify its impact on detector gain. To suppress this effect at the chip level, a 300 nm resistive film with a sheet resistance of is applied, effectively maintaining gain stability within 9% across varying operational conditions.
{"title":"The charging-up effects on Topmetal pixel chips for the polarization detection of GRBs","authors":"Lin Zhou , Huanbo Feng , Zuke Feng , Difan Yi , Ran Chen , Kuan Liu , Lirong Xie , Qian Zhong , Jiangchuan Tuo , Tianyi Xiong , Fei Xie , Enwei Liang , Hongbang Liu","doi":"10.1016/j.nima.2026.171355","DOIUrl":"10.1016/j.nima.2026.171355","url":null,"abstract":"<div><div>The Gas Microchannel Plate Pixel Detector (GMPD) is used in astrophysics for measuring X-ray polarization and serves as the prototype for the Low-Energy Polarization Detector (LPD) of the POLAR-2 project. During gamma-ray burst (GRB) observations, the incident flux can vary rapidly on short timescales, inducing charging-up effects that degrade gain stability. We characterize the chip-level charging-up behavior and quantify its impact on detector gain. To suppress this effect at the chip level, a 300 nm resistive film with a sheet resistance of <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>10</mn></mrow></msup><mspace></mspace><mi>Ω</mi><mo>/</mo><mi>sq</mi></mrow></math></span> is applied, effectively maintaining gain stability within 9% across varying operational conditions.</div></div>","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1086 ","pages":"Article 171355"},"PeriodicalIF":1.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146190890","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-06-01Epub Date: 2026-02-03DOI: 10.1016/j.nima.2026.171360
C.A. Alexe , J. Bendavid , L. Bianchini , D. Bruschini
We consider the problem of setting confidence intervals on a parameter of interest from the maximum-likelihood fit of a physics model to a binned data set with a large number of bins, large event-counts per bin, and in the presence of systematic uncertainties modeled as nuisance parameters. We use the profile-likelihood ratio for statistical inference and focus on the case in which the model is determined from Monte Carlo simulated samples of finite size. We start by presenting a toy model in which the properties of widely used approximations of the profile-likelihood ratio in the asymptotic limit, which are commonly expected to hold in the high-statistics regime, are manifestly broken even if the numbers of events per bin in both the data and simulated samples are seemingly large enough to warrant their validity. We then move to the general setting to show how statistical uncertainties in the Monte Carlo predictions can affect the coverage of confidence intervals constructed in the asymptotic approximation always in the same direction, namely they lead to systematic under-coverage.
{"title":"Under-coverage in high-statistics counting experiments with finite MC samples","authors":"C.A. Alexe , J. Bendavid , L. Bianchini , D. Bruschini","doi":"10.1016/j.nima.2026.171360","DOIUrl":"10.1016/j.nima.2026.171360","url":null,"abstract":"<div><div>We consider the problem of setting confidence intervals on a parameter of interest from the maximum-likelihood fit of a physics model to a binned data set with a large number of bins, large event-counts per bin, and in the presence of systematic uncertainties modeled as nuisance parameters. We use the profile-likelihood ratio for statistical inference and focus on the case in which the model is determined from Monte Carlo simulated samples of finite size. We start by presenting a toy model in which the properties of widely used approximations of the profile-likelihood ratio in the asymptotic limit, which are commonly expected to hold in the high-statistics regime, are manifestly broken even if the numbers of events per bin in both the data and simulated samples are seemingly large enough to warrant their validity. We then move to the general setting to show how statistical uncertainties in the Monte Carlo predictions can affect the coverage of confidence intervals constructed in the asymptotic approximation always in the same direction, namely they lead to systematic under-coverage.</div></div>","PeriodicalId":19359,"journal":{"name":"Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment","volume":"1086 ","pages":"Article 171360"},"PeriodicalIF":1.4,"publicationDate":"2026-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146190976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-06-01Epub Date: 2026-01-23DOI: 10.1016/j.nima.2026.171297
Omar Abdelrahman , Gianluca Aglieri Rinella , Luca Aglietta , Giacomo Alocco , Matias Antonelli , Roberto Baccomi , Francesco Barile , Pascal Becht , Franco Benotto , Stefania Maria Beolè , Marcello Borri , Daniela Bortoletto , Naseem Bouchhar , Giuseppe Eugenio Bruno , Matthew Daniel Buckland , Szymon Bugiel , Paolo Camerini , Francesca Carnesecchi , Marielle Chartier , Domenico Colella , Alessandra Zingaretti
This paper presents the characterisation and testing of the first wafer-scale monolithic stitched sensor (MOSS) prototype developed for the ALICE ITS3 upgrade that is to be installed during the LHC Long Shutdown 3 (2026–2030). The MOSS chip design is driven by the truly cylindrical detector geometry that imposes that each layer is built out of two wafer-sized, bent silicon chips. The stitching technique is employed to fabricate sensors with dimensions of 1.4 cm 25.9 cm, thinned to 50 m. The chip architecture, the in-pixel front-end, the laboratory and in-beam characterisation, the susceptibility to single-event effects, and the series testing are discussed. The testing campaign validates the design of a wafer-scale stitched sensor and the performance of the pixel matrix to be within the ITS3 requirements. The MOSS chip demonstrates the feasibility of the ITS3 detector concept and provides insights for further optimisation and development.
本文介绍了为ALICE ITS3升级开发的第一个晶圆级单片缝合传感器（MOSS）原型的特性和测试，该原型将在大型强子对撞机长停堆3（2026-2030）期间安装。MOSS芯片的设计是由真正的圆柱形探测器几何结构驱动的，它要求每层都由两个晶圆大小的弯曲硅芯片组成。采用拼接技术制备了尺寸为1.4 cm × 25.9 cm、厚度为50 μm的传感器。讨论了芯片结构、像素内前端、实验室和光束内特性、单事件效应敏感性和系列测试。测试活动验证了晶圆级缝合传感器的设计和像素矩阵的性能符合ITS3的要求。MOSS芯片证明了ITS3探测器概念的可行性，并为进一步优化和开发提供了见解。
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Pub Date : 2026-06-01Epub Date: 2026-02-06DOI: 10.1016/j.nima.2026.171365
Cristiano Bozza, KM3NeT Collaboration
The KM3NeT Collaboration is incrementally building two underwater Cherenkov neutrino telescopes in the Mediterranean Sea. Both telescopes share the same technology for neutrino detection, by studying Cherenkov radiation from secondary charged particles produced in neutrino interactions. Photomultipliers are a common choice for the detection of Cherenkov radiation, but the hostile underwater environment, affected by sea currents and bioluminescence demands innovative solutions in KM3NeT. The distinctive technological features of KM3NeT are discussed, such as its sub-nanosecond timing accuracy and the few-centimetre accurate acoustic positioning of the detector elements. This results in a neutrino pointing accuracy below 0.5°at energies above 100 TeV for track-like events. The KM3NeT design is modular and allows for data taking with the telescope still in the construction stage. Early technical and scientific results are enticing. In particular, KM3NeT recently discovered a neutrino of unprecedented energy from outer space. The article covers the design and operation of the KM3NeT telescopes, as well as readout techniques, time synchronisation, data flow and event reconstruction, highlighting both technical and scientific aspects.
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