Increase In Luminosity Research Articles

CACTUS: a depleted monolithic active timing sensor using a CMOS radiation hard technology

The planned luminosity increase at the Large Hadron Collider in the coming years has triggered interest in the use of the particles' time of arrival as additional information in specialized detectors to mitigate the impact of pile-up. The required time resolution is of the order of tens of picoseconds, with a spatial granularity of the order of 1 mm. A time measurement at this precision level will also be of interest beyond the LHC and beyond high energy particle physics. We present in this paper the first developments towards a radiation hard Depleted Monolithic Active Pixel Sensor (DMAPS), with high-resolution time measurement capability. The technology chosen is a standard high voltage CMOS process, in conjunction with a high resistivity detector material, which has already proven to efficiently detect particles in tracking applications after several hundred of Mrad of irradiation.

ATLAS muon trigger performance

Muons in the final state represent an important signature for many physics studies performed at the Large Hadron Collider (LHC), involving analyses on Standard Model measurements and on new physics searches. An optimized selection of such events requires an efficient and deeply understood muon trigger system. The present work describes the ATLAS muon trigger, consisting of a hardware-based system (Level-1) followed by a software-based reconstruction (High-Level Trigger). To handle the increase of luminosity in Run 2, several upgrades have been implemented to reduce the trigger rate, while still maintaining high values for the efficiency. Such improvements include the request of a coincidence of hits in the muon spectrometer and the hadronic tile calorimeter, an optimised muon isolation and a better estimation of transverse momentum. An overview will be presented on the most recent improvements of the ATLAS muon trigger and on its performance during Run 2. Finally an outlook for the most relevant upgrades planned for Run 3 will be reported.

The Luminosity Distribution of Short Gamma-Ray Bursts under a Structured Jet Scenario

Abstract The joint detection of gravitational wave (GW) and electromagnetic radiation from the binary neutron star merger event GW170817 marks a breakthrough in the field of multi-messenger astronomy. The short gamma-ray burst (sGRB) GRB 170817A, associated with this binary neutron star merger event, has an isotropic-equivalent gamma-ray radiation luminosity of 1.6 × 1047 erg s−1, which is much lower than that of other sGRBs. The measurement of the superluminal movement of the radio afterglow emission confirms the presence of the relativistic jet, and the emission features can be well explained by the structured jet model. In this paper, we calculate the luminosity distribution of sGRBs and its evolution with redshift based on the structured (Gaussian) jet model, and find that the typical luminosity increase with redshift, for nearby sGRBs (such as for luminosity distance less than 200 Mpc) the typical gamma-ray luminosity is just around 1047–1048 erg s−1, which naturally explains the very low radiation luminosity of GRB 170817A. We derived the detection probability of sGRBs by Fermi-GBM and found that the expected detection rate of sGRBs is only about 1 yr−1 within the distance of several hundred Mpc. We explored the effect of the power-law index α of the merger time distribution on the observed characteristics and found that it had little effect on the observed luminosity and viewing-angle distributions. However, it is very interesting that, for different values of α, the distributions of the number of observed sGRBs are quite different, so it is possible to determine the value of α through observed distributions of the number of sGRBs. We used the Bayesian method to make a quantitative analysis and found that the value of α may be identified when the number of observed sGRBs with known redshifts is more than 200. Finally, we compare our results of gamma-ray luminosity distribution with sGRBs with known redshifts, and found that our results are consistent with the observation, which implies that our simulation results can reproduce the observed luminosity distribution well.

Shock propagation in accretion discs around merging black holes: self-similar solution

ABSTRACT To date, the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo gravitational wave detectors have registered several events due to merging binary black holes. It is considered that black holes are surrounded by the circumbinary accretion disc therefore such events must be followed by perturbation of the disc and an increase in the flux of electromagnetic radiation from these objects. Our recent numerical investigations have shown that the heating of matter caused by a shock wave leads to an increase in luminosity. This shock wave arises in the accretion disc due to the central object mass loss as a result of the radiation of gravitational waves. In this paper, a self-similar solution is considered. In this solution the accretion disc perturbation is described in a region, dominated by gas pressure, and the matter opacity is determined by Thomson electron scattering processes. Such an analytical model allows us to approximately estimate the magnitude of the electromagnetic response of the gravitational wave event without time-consuming numerical calculations.

Fast ejecta resulted from jet–wind interaction in the Great Eruption of Eta Carinae

ABSTRACT The accretion model for the 19th century Great Eruption (GE) of η Carinae suggests that mass outflowing from the primary was accreted on to the secondary, and the gravitational energy of that mass accounts for the increase in luminosity and most of the kinetic energy of the ejecta. It further argues that the accretion was accompanied by the ejection of two jets that shaped the bipolar Homunculus nebula. Observations of echos from the GE found emission lines with broad wings suggesting some of the mass in equatorial directions reached more than $10\, 000 \, \rm {km\, s^{-1}}$. We run hydrodynamic simulations following periastron passage during the GE, launching jets from the secondary as it accreted gas erupted from the primary. We then follow the interaction of the polar jets with the surrounding primary wind, as they accelerate part of the flow to velocities ${\gt}10\, 000 \, \rm {km\, s^{-1}}$ and deflect it towards lower latitudes. We find that the amount of mass that reached these high velocities during the GE is $M_h \approx 0.02 \, \rm {M_{\odot }}$. This value reaches maximum and then decreases with time. Our simulations agree with previous results of the accretion model from which we estimate Mh taking into account the energy budget of the GE. The accretion model can explain the observations of high velocity gas in light echos with the known two stars, and a triple star system is not required.

Temperature and packing influence in storage of minimally processed pineapple and papaya

Pineapple and papaya have laborious peeling and cutting, making them inconvenient to the consumer. For this reason, the present work aims to study the chemical aspects for conservation of minimally processed 'Formosa' papaya and 'Perola' pineapple together in the same packing. Fruits were selected, washed, sanitized (200 mg Cl L-1) and stored for 12 h at 10°C. Then, the fruits were minimally processed in a room at 12°C, pineapples were peeled, cut into slices (1.5-2.0 cm thick), and these slides cut in halves, papayas were cut longitudinally in half, ends and seeds were removed and then sliced in transvers direction (1.5-2.0 cm thick). The slices were rinsed (20 mg Cl L-1), drained and packed in PET trays with lids and styrofoam trays covered with PVC film and stored at 4 and 8°C. Every 3 days during storage time, soluble solids (SS), titratable acidity (TA), SS/TA ratio, pH, ascorbic acid, soluble carbohydrates, color (luminosity, Hue, chromaticity), mass loss, texture and appearance were evaluated. For both products, there was an increase in titratable acidity at 4°C and small decreases in soluble solids, SS/TA ratio and pH, these changes being more pronounced at 8°C. Ascorbic acid increased in pineapple and decreased in papaya at 8°C. Soluble carbohydrates decreased in pineapple at 4°C, while in papaya the greater decrease occurred at 8°C. Larger increases in luminosity, Hue angle and chromaticity were observed at 4°C, and they were more significant for pineapple. After 9 days of storage, both fruits presented adequate quality for consumption and sale, the best temperature was 4°C in combination with the styrofoam packing covered with PVC.

CMS phase-II upgrade with GEM detector

The Large Hadron Collider (LHC) will be upgraded in several phases that will allow significant expansion of its physics program. The final luminosity of the accelerator is expected to exceed 5 × 1034cm−2s−1, five times more than the original design value. The CMS muon system must be able to sustain a physics program after the increase of luminosity and maintain sensitivity for electroweak physics for TeV scale searches similar to what was achieved up to now. To cope with the corresponding increase in background rates and trigger requirements, the installation of additional sets of muon detectors based on Gas Electron Multiplier (GEM) technology, referred to as GE2/1 and ME0, has been planned. The installation and commissioning of the GE2/1 chambers is scheduled in 2022, and for ME0 detectors are expected to be installed between 2022 to 2024. We present an overview of the Muon Spectrometer upgrade using GEM technology, a detailed description of the GE2/1 and ME0 upgrade in terms of design, pre-production chambers, mechanics, installation services etc. We will focus in particular on the novel solutions adopted for realization of the latter project, with a summary of the ongoing R&D activities

Energy reconstruction of the ATLAS Tile Calorimeter under high pile-up conditions using the Wiener filter

The ATLAS experiment records data from the proton-proton collisions produced by the Large Hadron Collider (LHC). The Tile Calorimeter is the hadronic sampling calorimeter of ATLAS in the region . It uses iron absorbers and scintillators as active material. Jointly with the other calorimeters it is designed for reconstruction of hadrons, jets, -lepton and missing transverse energy. It also assists in muon identification. The energy deposited by the particles in the Tile Calorimeter is read out by approximately 10,000 channels. The signal provided by the readout electronics for each channel is digitized at 40 MHz and its amplitude is estimated by an optimal filtering algorithm. The increase of LHC luminosity leads to signal pile-up that deforms the signal of interest and compromises the amplitude estimation performance. This work presents the proposed algorithm, based on the Wiener filter theory, for energy estimation in the Tile Calorimeter under high pile-up conditions during LHC Run 3. The performance of the proposed method is studied under various pile-up conditions and compared with the current optimal filtering method using proton-proton collision data.

Testing broad-line region models with reverberation mapping

ABSTRACT New reverberation mapping (RM) measurements, combined with accurate luminosities and line ratios, provide strong constraints on the location of the line emitting gas in the broad-line region (BLR) of active galactic nuclei (AGNs). In this paper, I present new calculations of radiation pressure and magnetic pressure confined clouds and apply them to a ‘generic AGN’ and to NGC 5548. The new calculations are in good agreement with the observed lags of all broad emission lines, and with the luminosities of Ly α, C iv 1549, O vi 1035, and He ii 1640. They are also in reasonable agreement with the luminosities of Mg ii 2798 and the 1990 Å blend of C iii] and Si iii] lines for high-metallicity gas. They explain the changes in time-lag following an increase in continuum luminosity and their dependencies on the inner and outer boundaries of the BLR. They also predict very strong Balmer and Paschen continua with important implications to continuum RM experiments. However, the calculated Balmer and Paschen line luminosities are too weak, by factors of 2–5. This ‘Balmer line crisis’ was noted in several earlier works and is now confirmed and constrained by RM measurements that were not available in the past. It seems that present photoionization codes that use the escape probability formalism fail to correctly compute the Balmer line luminosities in high-density, large optical depth gas.

Development of a FELIX based readout system for ITk strip hybrid module demonstrator for ATLAS Phase-II Upgrade

The Large Hadron Collider (LHC) will undergo a major upgrade around 2024 with a roughly tenfold increase in luminosity. It results in corresponding increases in particle rates and radiation doses that the current ATLAS Inner Tracking Detector cannot cope with. Therefore the ATLAS experiment will build a new all-silicon tracking system called the ITk (Inner Tracker) that includes an inside pixel detector close to the beam line and a strip detector in outside layer. Meanwhile the ATLAS experiment will adopt the Front-End Link eXchange (FELIX) system as the interface between the data acquisition and front-end electronics for all sub-detectors in the Phase II Upgrade. In this contribution, we present a prototype of FELIX based readout system for the strip hybrid module. Its hardware, firmware and software GUI application will be discussed, as well as integration test results.

Estimating the Jet Power of Mrk 231 during the 2017–2018 Flare

Abstract Long-term 17.6 GHz radio monitoring of the broad absorption-line quasar, Mrk 231, detected a strong flare in late 2017. This triggered four epochs of Very Long Baseline Array (VLBA) observations from 8.4 to 43 GHz over a 10 week period as well as an X-ray observation with NuSTAR. This was the third campaign of VLBA monitoring that we have obtained. The 43 GHz VLBA was degraded in all epochs, with only 7 of 10 antennas available in three epochs and 8 in the first epoch. However, useful results were obtained due to a fortuitous capturing of a complete, short 100 mJy flare at 17.6 GHz, both growth and decay. This provided useful constraints on the physical model of the ejected plasma that were not available in previous campaigns. We consider four classes of models: discrete ejections (both protonic and positronic) and jetted (protonic and positronic). The most viable model is a “dissipative bright knot” in a faint background leptonic jet with an energy flux ∼1043 erg s−1. Inverse Compton scattering calculations (based on these models) in the ambient quasar photon field explains the lack of a detectable increase in X-ray luminosity measured by NuSTAR. We show that the core (the bright knot) moves toward a nearby secondary at ≈0.97c. The background jet is much fainter. Evidently, the high-frequency VLBA core does not represent the point of origin of blazar jets, in general, and optical depth “core shift” estimates of jet points of origin can be misleading.

Understanding the role of chia (Salvia Hispanica L.) mucilage on olive oil-based emulsion gels as a new fat substitute in emulsified meat products

This study aimed to develop a chia mucilage (MC)-based emulsion gel (EG) with olive oil to replace pork back fat in emulsified meat products. Six variables (alginate—ALG; collagen—COL; whey—WHEY; carboxymethylcellulose—CMC; transglutaminase—MTG; carrageenan—CAR) with MC were evaluated using a Plackett–Burman (PB) design. Then, a complete factorial design was applied to evaluate the interactions and properties of the selected variables (ALG, COL, and WHEY) for the manufacture of EGs. The responses evaluated in the EGs were pH, color, emulsion stability, rheological, and texture parameters. In PB, the variables CMC, COL, ALG, and WHEY did not lead to any significant effects on the pH values of EGs, which ranged from 5.6 to 5.8. WHEY had a significant effect on the increase in luminosity of the EGs. ALG and WHEY decreased the liquid release of the samples showing greater stability of EGs and meat model systems. All samples of EGs, apart from run 5 (CMC, MTG, CAR, and ALG), showed a typical gel-like behavior (Gʹ > Gʺ) and a frequency-independent behavior. Even the formulation with only mucilage (run 12) showed a dominant Gʹ forming a gel-like structure. The complete factorial design showed stable and strong interactions between WHEY, MC, and olive oil, since a small or no liquid release, were observed in all experiments with WHEY. This study contributed to understanding the interactions among MC, biopolymers, and proteins, disclosing the potentiality of chia mucilage-based emulsion gels for the replacement of animal fat in emulsified meat products.

A study of [O III]/[O II] lines ratio in type 1 active galactic nucleus: Influence of radio jets and Eddington ratio to narrow line region emission

AbstractWe analyze emission line properties and their correlations for 18,043 type 1 active galactic nucleus (AGN) in the range of 0.02 ≤ z ≤ 0.8, based on Sloan Digital Sky Survey Data Release 14 data. We complement the data with photometric measurements from ROSAT, GALEX, 2MASS, and FIRST. We find the following: (a) The average correlation between luminosity of [O III] and AGN luminosity is stronger than those for [O II] line. This is consistent with the stratified model of narrow line region (NLR). Furthermore, we also find a weak dependence of ionization degree with AGN luminosity. (b) The narrow lines luminosity and radio luminosity correlation is stronger for radio quiet AGN and weaker for radio loud (RL) AGN, most likely due to radio jets. A possible explanation is as the jets penetrate the NLR, the shock will ionize its gas, increase the narrow lines emission, and cause a bigger dispersion in the correlation for RL AGN. (c) The investigated narrow lines, [O II], [O III], Hβ, Hα, [N II], and [S II], show a significant trend of decreasing luminosity ratio relative to the broad Hβ luminosity where the slopes in the range of −0.26 to −0.50. We did not find any correlation of the trend slopes with ionization potential or critical density of the lines. We suggest that this correlation is due to decrease in covering factor of NLR as AGN luminosity increases. (d) The EV1 correlation is found in our data and represents change in Eddington ratio. By using L[O III]/L[O II] ratio, we found that the ionization degree decreases as Eddington ratio increases. We also confirm that objects with higher Eddington ratio tend to have narrower Hβ, stronger Fe II emission, and weaker [O III] strength. In contrast to that, objects with lower Eddington ratio tend to have broader Hβ, weaker Fe II emission, and higher [O III] strength.

Evolution of the Global Carbon Cycle and Climate Regulation on Earth

AbstractThe existence of stabilizing feedbacks within Earth's climate system is generally thought to be necessary for the persistence of liquid water and life. Over the course of Earth's history, Earth's atmospheric composition appears to have adjusted to the gradual increase in solar luminosity, resulting in persistently habitable surface temperatures. With limited exceptions, the Earth system has been observed to recover rapidly from pulsed climatic perturbations. Carbon dioxide (CO2) regulation via negative feedbacks within the coupled global carbon‐silica cycles are classically viewed as the main processes giving rise to climate stability on Earth. Here we review the long‐term global carbon cycle budget, and how the processes modulating Earth's climate system have evolved over time. Specifically, we focus on the relative roles that shifts in carbon sources and sinks have played in driving long‐term changes in atmospheric pCO2. We make the case that marine processes are an important component of the canonical silicate weathering feedback, and have played a much more important role in pCO2 regulation than traditionally imagined. Notably, geochemical evidence indicate that the weathering of marine sediments and off‐axis basalt alteration act as major carbon sinks. However, this sink was potentially dampened during Earth's early history when oceans had higher levels of dissolved silicon (Si), iron (Fe), and magnesium (Mg), and instead likely fostered more extensive carbon recycling within the ocean‐atmosphere system via reverse weathering—that in turn acted to elevate ocean‐atmosphere CO2 levels.

A new and unusual LBV-like outburst from a Wolf–Rayet star in the outskirts of M33

ABSTRACT MCA-1B (also called UIT003) is a luminous hot star in the western outskirts of M33, classified over 20 yr ago with a spectral type of Ofpe/WN9 and identified then as a candidate luminous blue variable (LBV). Palomar Transient Factory data reveal that this star brightened in 2010, with a light curve resembling that of the classic LBV star AF And in M31. Other Ofpe/WN9 stars have erupted as LBVs, but MCA-1B was unusual because it remained hot. It showed a WN-type spectrum throughout its eruption, whereas LBVs usually get much cooler. MCA-1B showed an almost four-fold increase in bolometric luminosity and a doubling of its radius, but its temperature stayed ≳29 kK. As it faded, it shifted to even hotter temperatures, exhibiting a WN7/WN8-type spectrum, and doubling its wind speed. MCA-1B is reminiscent of some supernova impostors, and its location resembles the isolated environment of SN 2009ip. It is most similar to HD 5980 (in the Small Magellanic Cloud) and GR 290 (also in M33). Whereas these two LBVs exhibited B-type spectra in eruption, MCA-1B is the first clear case where a Wolf–Rayet (WR) spectrum persisted at all times. Together, MCA-1B, HD 5980, and GR 290 constitute a class of WN-type LBVs, distinct from S Doradus LBVs. They are most interesting in the context of LBVs at low metallicity, a possible post-LBV/WR transition in binaries, and as likely Type Ibn supernova progenitors.

Understanding Broad Mg ii Variability in Quasars with Photoionization: Implications for Reverberation Mapping and Changing-look Quasars

Abstract The broad Mg ii line in quasars has distinct variability properties compared with broad Balmer lines: it is less variable and usually does not display a “breathing” mode, the increase in the average cloud distance when luminosity increases. We demonstrate that these variability properties of Mg ii can be reasonably well explained by simple locally optimally emitting cloud (LOC) photoionization models, confirming earlier photoionization results. In the fiducial LOC model, the Mg ii-emitting gas is on average more distant from the ionizing source than the Hα/Hβ gas and responds with a lower amplitude to continuum variations. If the broad-line region (BLR) is truncated at a physical radius of ∼0.3 pc (for a 108.5 M ⊙ BH accreting at Eddington ratio of 0.1), most of the Mg ii flux will always be emitted near this outer boundary and hence will not display breathing. These results indicate that reverberation mapping results on broad Mg ii, while generally more difficult to obtain owing to the lower line responsivity, can still be used to infer the Mg ii BLR size and hence black hole mass. But it is possible that Mg ii does not have a well-defined intrinsic BLR size–luminosity relation for individual quasars, even though a global one for the general population may still exist. The dramatic changes in broad Hα/Hβ emission in the observationally rare changing-look quasars are fully consistent with photoionization responses to extreme continuum variability, and the LOC model provides natural explanations for the persistence of broad Mg ii in changing-look quasars defined on Hα/Hβ and the rare population of broad Mg ii emitters in the spectra of massive inactive galaxies.

Fast and resource-efficient Deep Neural Network on FPGA for the Phase-II Level-0 muon barrel trigger of the ATLAS experiment

The Level-0 muon trigger system of the ATLAS experiment will undergo a full upgrade for the High Luminosity LHC to stand the challenging requirements imposed by the increase in instantaneous luminosity. The upgraded trigger system will send raw hit data to off-detector processors, where trigger algorithms run on a new generation of FPGAs. To exploit the flexibility provided by the FPGA systems, ATLAS is developing novel precision deep neural network architectures based on trained ternary quantisation, optimised to run on FPGAs for efficient reconstruction and identification of muons in the ATLAS “Level-0” trigger. Physics performance in terms of efficiency and fake rates and FPGA logic resource occupancy and timing obtained with the developed algorithms are discussed.

Performance of electron and photon triggers in ATLAS during LHC Run 2

Electron and photon triggers covering transverse energies from 5 text {GeV } to several text {TeV } are essential for the ATLAS experiment to record signals for a wide variety of physics: from Standard Model processes to searches for new phenomena in both proton–proton and heavy-ion collisions. To cope with a fourfold increase of peak LHC luminosity from 2015 to 2018 (Run 2), to 2.1 times 10^{34},hbox {cm}^{-2}hbox { s}^{-1}, and a similar increase in the number of interactions per beam-crossing to about 60, trigger algorithms and selections were optimised to control the rates while retaining a high efficiency for physics analyses. For proton–proton collisions, the single-electron trigger efficiency relative to a single-electron offline selection is at least 75% for an offline electron of 31 text {GeV }, and rises to 96% at 60 text {GeV }; the trigger efficiency of a 25 text {GeV } leg of the primary diphoton trigger relative to a tight offline photon selection is more than 96% for an offline photon of 30 text {GeV }. For heavy-ion collisions, the primary electron and photon trigger efficiencies relative to the corresponding standard offline selections are at least 84% and 95%, respectively, at 5 text {GeV } above the corresponding trigger threshold.

Application of Synthetic Peptides to Improve Parameters of Skin Physiology: An Open Observational 30-Day Study

We describe a novel, non-invasive peptide-based product intended to counter several pathophysiological signs of aged skin through the topical application of signalling molecule mimics. Several aesthetic parameters of skin physiology were assessed. The product was tested on 20 healthy Caucasian women (35 - 55 years-old) who applied the product twice-daily to the face for 30 days. Skin elasticity, firmness, sagging, brightness, and luminosity were assessed. Additionally, over a period of 3 hours, the hydrating effect of the product vs placebo vs non-treated skin was assessed. After 30 days, participants showed significant increases in skin elasticity (11.8% increase, p < 0.01), luminosity (2.5% increase, p < 0.01), and brightness (110% increase, p < 0.001) with concomitant significant decreases in skin sagging (6.3% decrease, p < 0.05). The product gave a rapid and sustained hydrating action that was significantly greater than placebo alone (10.2% increase, p < 0.05). No adverse reactions were reported. Cosmetic products based on the action of synthetic peptide mimics of endogenous signalling molecules show promise for combatting the pathological degradation of skin as seen in the elderly. Strategies to reverse these symptoms through non-invasive techniques warrant further investigation. This study provides support for the application of peptides to combat signs of aging and to improve the general condition of the skin.

The Belle II Raw Data Management System

The Belle II experiment, a major upgrade of the previouse+e−asymmetric collider experiment Belle, is expected to produce tens of petabytes of data per year due to the luminosity increase from the upgraded SuperKEKB accelerator. The distributed computing system of the Belle II experiment plays a key role, storing and distributing data in a reliable way to be easily accessed and analyzed by more than 1000 collaborators. In particular, the Belle II Raw Data Management system has been developed with an aim to upload output files onto grid storage, register them into the file and metadata catalogs, and make two replicas of the full raw data set using the Belle II Distributed Data Management system. It has been implemented as an extension of DIRAC (Distributed Infrastructure with Remote Agent Control) and consists of a database, services, client and monitoring tools, and several agents that treat the data automatically. The first year of data taken with the Belle II full detector has been managed by the Belle II Raw Data Management system successfully. The design, current status, and performance are presented. Prospects for improvements towards the full luminosity data taking are also reviewed.