Luminosity Measurements Research Articles

Metrological Uncertainties in the Integrated Luminosity Measurement with the Updated Design of a Detector at CEPC

Abstract In order to measure integrated luminosity with the required precision of $10^{-4}$ at the $Z^0$ pole, the proposed CEPC $e^{+}e^{-}$ collider requires a luminometer, a specially designed calorimeter placed in the very forward region to identify Bhabha scattering at low polar angles. Usually, such a device is placed at the outgoing beams, to keep the spatial symmetries of the head-on collisions at accelerators with a nonzero crossing angle. At CEPC it is currently proposed to place the luminometer on the z-axis. We review the feasibility of measurement of the integrated luminosity at the $Z^{0}$ pole with the required precision, focusing on the luminometer centered around the z-axis and the post-CDR beam properties.

Intelligent and Optimal System for Monitoring Environmental Variables and Solar Luminosity, with solar path tracker and telemetry

In this proposed research are analyzed general solutions and techniques to optimize the solar luminosity measurement by a designed smart system, as well as its usability by the solar energy conversion and its storing. However, many times, this kind of systems have not an optimal solar path tracker and as a consequence it can not be measured the full solar luminosity during all the day, therefore, in this work are designed optimal mathematical models and algorithms to enhance the solar path tracker according to measure solar luminosity and getting optimal solar energy conversion/storing, which is useful to study geographical conditions before to build solar energy conversion centers. As well as, in this research also is studied and suggested some techniques to get wireless data communication regarding the measured environmental variables, measured solar luminosity and stored electrical energy as a consequence of the solar energy conversion, which can be transmitted, so far away, to a central monitoring center by Radio Frequency (RF) waves.

Luminosity calibration bias in van-der-Meer scan due to the beam-beam interaction for q-Gaussian beams

The accuracy of luminosity calibration is an important problem in the operation of colliders, the successful solution of which determines the accuracy of the experiments performed. In hadron colliders, luminosity calibration is performed using van-der-Meer scanning, the goal of which is to measure the overlap of the colliding beams. When two beams collide, their electromagnetic interaction leads to a change in their overlap and, consequently, the luminosity calibration is biased. Typically, this effect is accounted for under the assumption that beams have a Gaussian particle distribution. However, it is known that the particle distribution in hadron collider beams differs from Gaussian and is more generally described by q-Gaussian functions. Accurate accounting of electromagnetic interaction becomes an urgent task as the requirements for the accuracy of luminosity measurements increase (for example, in the HL-LHC project the goal is an accuracy of 1 %). This paper presents a model of the electromagnetic interaction of beams with a q-Gaussian distribution of particles, and determines the influence of this interaction on the luminosity calibration using the van der Meer scanning method. Calculations were carried out for beams with conditions of the CMS and ATLA experiments.

On the Initial Spin Period Distribution of Neutron Stars

We derive the initial spin period distribution of neutron stars by studying the population of young pulsars associated with supernova remnants. Our hierarchical Bayesian approach accounts for the measurement uncertainties of individual observations and selection effects. Without correcting for selection effects, as done in previous studies, we find that pulsar initial spin periods follow a Weibull distribution, peaking at 40 ms, which is favored against a lognormal distribution with a Bayes factor of 200. The known selection effects in radio pulsar surveys, including pulse broadening and period-dependent beaming fraction, have been quantitatively investigated. We show that, based on measurements of pulsar luminosity and spin period from the ATNF Pulsar Catalogue, the impact of pulse broadening on the inference of the pulsar period distribution is likely to be insignificant. Correcting for the beaming selection effect, the Weibull distribution remains the preferred model, while its peak slightly shifts to longer periods at 50 ms. Our method will prove useful in constraining the birth properties of neutron stars in the Square Kilometre Array era.

Constraints on the z ∼ 5 Star-forming Galaxy Luminosity Function From Hubble Space Telescope Imaging of an Unbiased and Complete Sample of Long Gamma-Ray Burst Host Galaxies

We present rest-frame UV Hubble Space Telescope imaging of the largest and most complete sample of 23 long-duration gamma-ray burst (GRB) host galaxies between redshifts 4 and 6. Of these 23, we present new WFC3/F110W imaging for 19 of the hosts, which we combine with archival WFC3/F110W and WFC3/F140W imaging for the remaining four. We use the photometry of the host galaxies from this sample to characterize both the rest-frame UV luminosity function (LF) and the size–luminosity relation of the sample. We find that when assuming the standard Schechter-function parameterization for the UV LF, the GRB host sample is best fit with α=−1.30−0.25+0.30 and M*=−20.33−0.54+0.44 mag, which are consistent with results based on z ∼ 5 Lyman-break galaxies. We find that ∼68% of our size–luminosity measurements fall within or below the same relation for Lyman-break galaxies at z ∼ 4. This study observationally confirms expectations that at z ∼ 5 Lyman-break and GRB host galaxies should trace the same population and demonstrates the utility of GRBs as probes of hidden star formation in the high-redshift Universe. Under the assumption that GRBs unbiasedly trace star formation at this redshift, our nondetection fraction of 7/23 is consistent at the 95% confidence level with 13%–53% of star formation at redshift z ∼ 5 occurring in galaxies fainter than our detection limit of M 1600Å ≈ −18.3 mag.

NuSTAR detection of a broad absorption line in IGR J06074+2205

BeXRB pulsar IGR J06074+2205 using NuSTAR observations. The temporal and spectral characteristics of the source are investigated. We detect coherent X-ray pulsations of the source and determine the spin period evolution. Using the current spin period data of the source, we show that the source is spinning down at 0.0202(2) sday−1. The pulse profiles are found to evolve with energy and luminosity. Another interesting feature of the source is that the pulse profiles are dual peaked. The dual-peaked pulse profile is characterized by a decreasing secondary peak amplitude with increasing energy. We also observed a proportionate increase in the primary peak amplitude as the energy increases. The pulse fraction exhibits an overall increasing trend with the energy. The X-ray continuum of the source indicates the existence of a characteristic absorption feature with a centroid energy ∼55 keV, which may be interpreted as a cyclotron line. We estimate the corresponding magnetic field strength to be ∼4.74×1012 G. A peculiar ‘10 keV’ absorption feature is observed in the X-ray spectra of the second observation. The luminosity measurements predict that the source may be accreting in the sub-critical regime.

Overview of the ATLAS High-Granularity Timing Detector: project status and results

The increase of the particle flux (pile-up) at the high-luminosity phase of the Large Hadron Collider (LHC) with an instantaneous luminosity up to L ≈ 7.5 × 1034 cm-2 s-1 will have a severe impact on the ATLAS detector reconstruction and trigger performance. A High Granularity Timing Detector (HGTD) will be installed in the forward region for pile-up mitigation and luminosity measurement. This detector, based on Low Gain Avalanche Detectors and custom ASICs, will provide a time resolution of 30 ps per track at the beginning of HL-LHC and 50 ps at the end. This proceeding paper will summarise the overall specifications of the HGTD as well as the project status.

The fundamental plane of blazars based on the black hole spin-mass energy

ABSTRACT We examine the fundamental plane of 91 blazars which include flat-spectrum radio quasars and BL Lacertae objects with known X-ray luminosity (LR), radio luminosity (LX), and black hole mass measurements (M) to reflect the relationship between jet and accretion for blazars. The fundamental plane of blazars are logLR = ${0.273}_{+0.059}^{-0.059}\log L_X$ + ${0.695}_{+0.191}^{-0.191}\log M$ + ${25.457}_{+2.728}^{-2.728}$ and logLR = ${0.190}_{+0.049}^{-0.049}\log L_X$ + ${0.475}_{+0.157}^{-0.157}\log M$ + ${28.568}_{+2.245}^{-2.245}$ after considering the effect of beam factor. Our results suggest that the jet of blazars has connection with accretion. We set the black hole spin energy as a new variable to correct the black hole mass and explore the effect of black hole spin on the fundamental relationship. We find that the fundamental plane of blazars is affected by the black hole spin, which is similar to the previous work for active galactic nuclei. We additionally examine a new fundamental plane which is based on the black hole spin-mass energy (Mspin). The new fundamental plane (logLR = ${0.332}_{+0.081}^{-0.081}\log L_X$ + ${0.502}_{+0.091}^{-0.091}\log M_{spin}$ + ${22.606}_{+3.346}^{-3.346}$ with R-Square = 0.575) shows that Mspin has a better correlation coefficient compared to the M for fundamental plane of blazars. These results suggest that the black hole spin should be considered as an important factor for the study of fundamental plane for blazars. And these may further our understanding of the Blandford–Znajek process in blazars.

Low Gain Avalanche Detectors for the ATLAS High Granularity Timing Detector: Laboratory and test beam campaigns

The High Granularity Timing Detector (HGTD) is designed for the mitigation of pile-up effects in the ATLAS forward region and for bunch per bunch luminosity measurements. HGTD, based on Low Gain Avalanche Detector (LGAD) technology and covering the pseudorapidity region between 2.4 and 4.0, will provide high precision timing information to distinguish between collisions occurring close in space but well-separated in time. Apart from being radiation resistant, LGAD sensors should deliver 30 ps time resolution per track for a minimum-ionizing particle (35 ps per hit) at the start of lifetime, increasing to 50 ps per track (70 ps per hit) at the end of HL-LHC operation. Each readout cell has a transverse size of 1.3×1.3 mm2 leading to a highly granular detector with about 3 millions of readout electronics channels. A dedicated ASIC for the HGTD detector, ALTIROC, is being developed in several phases producing prototype versions of 2×2, 5×5 and 15×15 channels. HGTD modules are hybrids of the LGAD and ALTIROC connected through flip-chip bump bonding process. Several test beam campaigns have been conducted at DESY and CERN SPS between 2021 and 2022. A summary of the results from LGAD-alone and hybrids will be presented.

LUCID-3: the upgrade of the ATLAS luminosity detector for High-Luminosity LHC

The ATLAS physics program at the High Luminosity LHC (HL-LHC) calls for a precision in the luminosity measurement of 1%. A larger uncertainty would represent the dominant systematic error in precision measurements, including those in the Higgs sector. To fulfill such requirement in an environment characterized by up to 140 simultaneous interactions per crossing (200 in the ultimate scenario), ATLAS will feature several luminosity detectors. At least some of them must be both calibratable in the van der Meer scans at low luminosity and able to measure up to the highest values. LUCID-3, the upgrade of the present ATLAS luminometer (LUCID-2), will fulfill such a condition. The reasons for an upgrade of LUCID-2 and the envisaged solutions are discussed and a description of the LUCID-3 project is given. Finally, the first results obtained with the prototypes installed in ATLAS during the present LHC Run-3 are discussed as means of the validation of the final design.

The CMS Fast Beam Condition Monitor for HL-LHC

The high-luminosity upgrade of the LHC brings unprecedented requirements for real-time and precision bunch-by-bunch online luminosity measurement and beam-induced background monitoring. A key component of the CMS Beam Radiation, Instrumentation and Luminosity system is a stand-alone luminometer, the Fast Beam Condition Monitor (FBCM), which is fully independent from the CMS central trigger and data acquisition services and able to operate at all times with a triggerless readout. FBCM utilizes a dedicated front-end application-specific integrated circuit (ASIC) to amplify the signals from CO2-cooled silicon-pad sensors with a timing resolution of a few nanoseconds, which enables the measurement of the beam-induced background. FBCM uses a modular design with two half-disks of twelve modules at each end of CMS, with four service modules placed close to the outer edge to reduce radiation-induced aging. The electronics system design adapts several components from the CMS Tracker for power, control and read-out functionalities. The dedicated FBCM23 ASIC contains six channels and adjustable shaping time to optimize the noise with regards to sensor leakage current. Each ASIC channel outputs a single binary high-speed asynchronous signal carrying time-of-arrival and time-over-threshold information. The chip output signal is digitized,encoded, and sent via a radiation-hard gigabit transceiverand an optical link to the back-end electronics for analysis. This paper reports on the updated design of the FBCM detector and the ongoing testing program.

The Measurement of Masses of OB-type Stars from LAMOST DR5

The measurements of masses and luminosities of massive stars play an important role in understanding the formation and evolution of their host galaxies. In this work, we present the measurement of masses and luminosities of 2946 OB-type stars, including 78 O-type stars and 2868 B-type stars, based on their stellar parameters (effective temperature, surface gravity, and metallicity) and the Padova and Trieste Stellar Evolution Code isochrones model. Our results show that the median mass and luminosity of the 2946 OB-type stars are 5.4 M ⊙ and log(L/L ⊙) = 3.2 with median relative errors of 21.4% and 71.1%, respectively. A good agreement between our results estimated by using our method and those derived by using the orbital motions of binary stars from the literature is found for some B-type stars. In addition, we also fit the mass–luminosity relation of B-type stars by using our derived mass and the luminosity from Gaia Data Release 3.

Luminosity calibration by means of van-der-Meer scan for Q-Gaussian beams

Luminosity is the key quantity characterizing the performance of charged particle colliders. Precise luminosity determination is an important task in collider physics. Part of this task is the proper calibration of detectors dedicated for luminosity measurements. The wide-used experimental method of calibration is the van-der-Meer scan, which is the beam separation scan performed at specifically optimized beam conditions. This work is devoted to modeling this scan with the q-Gaussian distribution of particles in colliding beams. Because of its properties, the q-Gaussian distribution is believed to describe the density closer to reality than regular Gaussian-based models. In this work, the q-Gaussian model is applied for van-der-Meer scan modeling, and the benefits of this model for luminosity calibration task are demonstrated.

The optimization, design and performance of the FBCM23 ASIC for the upgraded CMS beam monitoring system

We present the development of the FBCM23 ASIC designed for the Phase-II upgrade of the Fast Beam Condition Monitoring (FBCM) system built at the CMS experiment which will replace the present luminometer based on the BCM1F ASIC [1]. The FBCM system should provide reliable luminosity measurement with 1 ns time resolution enabling the detection of beam-induced background. The FBCM23 ASIC comprises 6 channels of the fast front-end amplifier working in transimpedance configuration, booster amplifier, and leading edge discriminator. The complete processing chain provides an overall shaping function equivalent to the CR-RC3 filter. The paper will show the optimization of the design, overall architecture, and the detailed implementation in a CMOS 65 nm process as well as preliminary electrical performance.

ALICE luminosity determination for Pb–Pb collisions at √s NN = 5.02 TeV

Luminosity determination within the ALICE experiment is based on the measurement, in van der Meer scans, of the cross sections for visible processes involving one or more detectors (visible cross sections). In 2015 and 2018, the Large Hadron Collider provided Pb–Pb collisions at a centre-of-mass energy per nucleon pair of √s NN = 5.02 TeV. Two visible cross sections, associated with particle detection in the Zero Degree Calorimeter (ZDC) and in the V0 detector, were measured in a van der Meer scan.This article describes the experimental set-up and the analysis procedure, and presents the measurement results. The analysis involves a comprehensive study of beam-related effects and an improved fitting procedure, compared to previous ALICE studies, for the extraction of the visible cross section. The resulting uncertainty of both the ZDC-based and the V0-based luminosity measurement for the full sample is 2.5%. The inelastic cross section for hadronic interactions in Pb–Pb collisions at √s NN = 5.02 TeV, obtained by efficiency correction of the V0-based visible cross section, was measured to be 7.67 ± 0.25 b, in agreement with predictions using the Glauber model.

Luminosity determination using Z boson production at the CMS experiment

The measurement of Z boson production is presented as a method to determine the integrated luminosity of CMS data sets. The analysis uses proton–proton collision data, recorded by the CMS experiment at the CERN LHC in 2017 at a center-of-mass energy of 13TeV\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\,\ ext {Te\\hspace{-.08em}V}$$\\end{document}. Events with Z bosons decaying into a pair of muons are selected. The total number of Z bosons produced in a fiducial volume is determined, together with the identification efficiencies and correlations from the same data set, in small intervals of 20pb-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\,\ ext {pb}^{-1}$$\\end{document} of integrated luminosity, thus facilitating the efficiency and rate measurement as a function of time and instantaneous luminosity. Using the ratio of the efficiency-corrected numbers of Z bosons, the precisely measured integrated luminosity of one data set is used to determine the luminosity of another. For the first time, a full quantitative uncertainty analysis of the use of Z bosons for the integrated luminosity measurement is performed. The uncertainty in the extrapolation between two data sets, recorded in 2017 at low and high instantaneous luminosity, is less than 0.5%. We show that the Z boson rate measurement constitutes a precise method, complementary to traditional methods, with the potential to improve the measurement of the integrated luminosity.

BPNN model based AI for the estimation of soot data from flame luminosity emissions in H2/N2 diluted ethylene laminar diffusion flames

Advanced combustion devices and alternative fuels like hydrogen require an estimation of the impact of such changes on engine exhaust emissions of regulated pollutants like soot. Huge experimental data are then required to be collected and post-processed, both in academic and industrial setups. Machine learning and artificial intelligence can be employed to reduce cost and time. This study presents a Back Propagation Neural Network (BPNN) model that has been validated and optimized for the simultaneous prediction of soot volume fraction, temperature and particle sizes from flame luminosity measurements. The compatibility, robustness and reliability of neural network models in terms of fuel composition and flow rate variations was analyzed , by varying both fuel flow rate and fuel stream dilution in axisymmetric diffusion flame burning in a coflow of air. BPNN model predicted results were contrasted against those obtained through laser diagnostics. A detailed analysis of the performance of BPNN model, based on an extensive experimental study revealed indifference to N2/H2 dilution and fuel flow rate variations. Furthermore, an original BPNN model is optimized to improve learning rate and to reduce computation cost, by applying a Bayesian algorithm which continuously monitors and minimizes an error function. It was concluded that a training set size of three was sufficient to predict soot field parameters with a fair prediction accuracy. These results have direct implication for the application of proposed technique in practical combustion equipment where operating parameter, e.g. Air–fuel ratio and EGR, show both gradual and instantaneous variations and affect both performance and emissions. These results clearly demonstrate the robustness of this technique which offers opportunities for real-time, in situ, monitoring of practical combustion devices. Hence, Real-time data of sooting characteristics of flames can be used to both monitor and control pollutant emissions by integrating a response strategy in the system.

High energy bremsstrahlung at the FCC-ee, FCC-eh and LHeC

Bremsstrahlung spectra will be strongly distorted due to small lateral beam sizes at future colliders. That in turn will have large consequences for the electron and positron beam lifetimes as well as for the luminosity measurements in the case of electron-hadron colliders. We discuss in detail such consequences for the future circular collider and large hadron electron collider cases.

Efficient simulations of ionized ISM emission lines: a detailed comparison between the FIRE high-redshift suite and observations

ABSTRACT The Atacama Large Millimeter/Submillimeter Array (ALMA) in the submillimetre and the JWST in the infrared have achieved robust spectroscopic detections of emission lines from the interstellar medium (ISM) in some of the first galaxies. These unprecedented measurements provide valuable information regarding the ISM properties, stellar populations, galaxy morphologies, and kinematics in these high-redshift galaxies and, in principle, offer powerful tests of state of the art galaxy formation models, as implemented in hydrodynamical simulations. To facilitate direct comparisons between simulations and observations, we develop a fast post-processing pipeline to predict line emission from the H ii regions around simulated star particles, accounting for spatial variations in the surrounding gas density, metallicity, and incident radiation spectrum. Our ISM line emission model currently captures H α, H β, and all of the [O iii] and [O ii] lines targeted by ALMA and JWST at z > 6. We illustrate the power of this approach by applying our line emission model to the publicly available Feedback In Realistic Environments (FIRE) high-z simulation suite and perform a detailed comparison with current observations. We show that the FIRE mass–metallicity relation is in 1σ agreement with ALMA/JWST measurements after accounting for the inhomogeneities in the ISM properties. We also quantitatively validate the description of the one-zone model, which is widely used for interpreting [O iii] and H β line luminosity measurements. This model is publicly available and can be implemented on top of a broad range of galaxy formation simulations for comparison with JWST and ALMA measurements.

Optical Identification of Galaxy Clusters among SRG/eROSITA X-ray Sources Based on Photometric Redshift Estimates for Galaxies

We discuss an algorithm whereby the massive galaxy clusters detected in the SRG/eROSITA all-sky survey are identified and their photometric redshifts are estimated. For this purpose, we use photometric redshift estimates for galaxies and WISE forced photometry. To estimate the algorithm operation quality, we used a sample of 634 massive galaxy clusters from the Planck survey with known spectroscopic redshifts in the range 0,1zspec0,6. The accuracy of the photometric redshift estimates for this sample is bzphot/(1+zphot)=0,5%, the fraction of large deviations is 1.3%. We show that these large deviations arise mainly from the projections of galaxy clusters or other large-scale structures at different redshifts in the X-ray source field. Measuring the infrared (IR) luminosities of galaxy clusters allows one to estimate the reliability of the optical identification of the clusters detected in the SRG/eROSITA survey and to obtain an additional independent measurement of their total gravitational masses, M500. We show that the masses M500 of the galaxy clusters estimated from their IR luminosity measurements have an accuracy @logM500=0,124, comparable to the accuracy of the mass estimation for the galaxy clusters from their X-ray luminosities.