Medium-Induced Modification of Z-Tagged Charged Particle Yields in Pb+Pb Collisions at 5.02 TeV with the ATLAS Detector

The yield of charged particles opposite to a Z boson with large transverse momentum ( p T ) is measured in 260     pb − 1 of p p and 1.7     nb − 1 of Pb + Pb collision data at 5.02 TeV per nucleon pair recorded with the ATLAS detector at the Large Hadron Collider. The Z boson tag is used to select hard-scattered partons with specific kinematics, and to observe how their showers are modified as they propagate through the quark-gluon plasma created in Pb + Pb collisions. Compared with p p collisions, charged-particle yields in Pb + Pb collisions show significant modifications as a function of charged-particle p T in a way that depends on event centrality and Z boson p T . The data are compared with a variety of theoretical calculations and provide new information about the medium-induced energy loss of partons in a p T regime difficult to measure through other channels

The ATLAS inner detector trigger performance in pp collisions at 13 TeV during LHC Run 2

The design and performance of the inner detector trigger for the high level trigger of the ATLAS experiment at the Large Hadron Collider during the 2016-2018 data taking period is discussed. In 2016, 2017, and 2018 the ATLAS detector recorded 35.6 fb(-1), 46.9 fb(-1), and 60.6 fb(-1) respectively of proton-proton collision data at a centre-of-mass energy of 13TeV. In order to deal with the very high interaction multiplicities per bunch crossing expected with the 13TeV collisions the inner detector trigger was redesigned during the long shutdown of the Large Hadron Collider from 2013 until 2015. An overview of these developments is provided and the performance of the tracking in the trigger for the muon, electron, tau and b-jet signatures is discussed. The high performance of the inner detector trigger with these extreme interaction multiplicities demonstrates how the inner detector tracking continues to lie at the heart of the trigger performance and is essential in enabling the ATLAS physics programme

Search for pair production of third-generation scalar leptoquarks decaying into a top quark and a τ-lepton in pp collisions at s√ = 13 TeV with the ATLAS detector

A search for pair production of third-generation scalar leptoquarks decaying into a top quark and a τ-lepton is presented. The search is based on a dataset of pp collisions at s√ = 13 TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1. Events are selected if they have one light lepton (electron or muon) and at least one hadronically decaying τ -lepton, or at least two light leptons. In addition, two or more jets, at least one of which must be identified as containing b-hadrons, are required. Six final states, defined by the multiplicity and flavour of lepton candidates, are considered in the analysis. Each of them is split into multiple event categories to simultaneously search for the signal and constrain several leading backgrounds. The signal-rich event categories require at least one hadronically decaying τ-lepton candidate and exploit the presence of energetic final-state objects, which is characteristic of signal events. No significant excess above the Standard Model expectation is observed in any of the considered event categories, and 95% CL upper limits are set on the production cross section as a function of the leptoquark mass, for different assumptions about the branching fractions into tτ and bν. Scalar leptoquarks decaying exclusively into tτ are excluded up to masses of 1.43 TeV while, for a branching fraction of 50% into tτ, the lower mass limit is 1.22 TeV

Two-particle azimuthal correlations in photonuclear ultraperipheral Pb plus Pb collisions at 5.02 TeV with ATLAS

Two-particle long-range azimuthal correlations are measured in photonuclear collisions using 1.7 nb − 1 of 5.02 TeV Pb + Pb collision data collected by the ATLAS experiment at the CERN Large Hadron Collider. Candidate events are selected using a dedicated high-multiplicity photonuclear event trigger, a combination of information from the zero-degree calorimeters and forward calorimeters, and from pseudorapidity gaps constructed using calorimeter energy clusters and charged-particle tracks. Distributions of event properties are compared between data and Monte Carlo simulations of photonuclear processes. Two-particle correlation functions are formed using charged-particle tracks in the selected events, and a template-fitting method is employed to subtract the nonflow contribution to the correlation. Significant nonzero values of the second- and third-order flow coefficients are observed and presented as a function of charged-particle multiplicity and transverse momentum. The results are compared with flow coefficients obtained in proton-proton and proton-lead collisions in similar multiplicity ranges, and with theoretical expectations. The unique initial conditions present in this measurement provide a new way to probe the origin of the collective signatures previously observed only in hadronic collision

Observation of electroweak production of two jets in association with an isolated photon and missing transverse momentum, and search for a Higgs boson decaying into invisible particles at 13 TeV with the ATLAS detector

This paper presents the measurement of the electroweak production of two jets in association with a $Z\gamma$ pair with the $Z$ boson decaying into two neutrinos. It also presents the search for invisible or partially invisible decays of a Higgs boson with a mass of 125 GeV produced through vector-boson fusion with a photon in the final state. These results use data from LHC proton-proton collisions at $\sqrt{s}$ = 13 TeV collected with the ATLAS detector corresponding to an integrated luminosity of 139 fb$^{-1}$. The event signature, shared by all benchmark processes considered for measurements and searches, is characterized by a significant amount of unbalanced transverse momentum and a photon in the final state, in addition to a pair of forward jets. For electroweak production of $Z\gamma$ in association with two jets, the background-only hypothesis is rejected with an observed (expected) significance of 5.2 (5.1) standard deviations. The measured fiducial cross-section for this process is 1.31$\pm$0.29 fb. Observed (expected) upper limit of 0.37 (0.34) at 95% confidence level is set on the branching ratio of a 125 GeV Higgs boson to invisible particles, assuming the Standard Model production cross-section. The signature is also interpreted in the context of decays of a Higgs boson to a photon and a dark photon. An observed (expected) 95% CL upper limit on the branching ratio for this decay is set at 0.018 (0.017), assuming the 125 GeV Standard Model Higgs boson production cross-section

The ATLAS inner detector trigger performance in pp collisions at 13 TeV during LHC Run 2

The design and performance of the inner detector trigger for the high level trigger of the ATLAS experiment at the Large Hadron Collider during the 2016-18 data taking period is discussed. In 2016, 2017, and 2018 the ATLAS detector recorded 35.6 fb$^{-1}$, 46.9 fb$^{-1}$, and 60.6 fb$^{-1}$ respectively of proton-proton collision data at a centre-of-mass energy of 13 TeV. In order to deal with the very high interaction multiplicities per bunch crossing expected with the 13 TeV collisions the inner detector trigger was redesigned during the long shutdown of the Large Hadron Collider from 2013 until 2015. An overview of these developments is provided and the performance of the tracking in the trigger for the muon, electron, tau and $b$-jet signatures is discussed. The high performance of the inner detector trigger with these extreme interaction multiplicities demonstrates how the inner detector tracking continues to lie at the heart of the trigger performance and is essential in enabling the ATLAS physics programme

The ATLAS inner detector trigger performance in pp collisions at 13 TeV during LHC Run 2

The design and performance of the inner detector trigger for the high level trigger of the ATLAS experiment at the Large Hadron Collider during the 2016-18 data taking period is discussed. In 2016, 2017, and 2018 the ATLAS detector recorded 35.6 fb$^{-1}$, 46.9 fb$^{-1}$, and 60.6 fb$^{-1}$ respectively of proton-proton collision data at a centre-of-mass energy of 13 TeV. In order to deal with the very high interaction multiplicities per bunch crossing expected with the 13 TeV collisions the inner detector trigger was redesigned during the long shutdown of the Large Hadron Collider from 2013 until 2015. An overview of these developments is provided and the performance of the tracking in the trigger for the muon, electron, tau and $b$-jet signatures is discussed. The high performance of the inner detector trigger with these extreme interaction multiplicities demonstrates how the inner detector tracking continues to lie at the heart of the trigger performance and is essential in enabling the ATLAS physics programme

Leaching of silver from solid waste using ultrasound assisted thiourea method

Thiourea leaching of precious metals such as gold and silver from ores has several advantages when compared with conventional cyanidation process. In recent years, the use of ultrasound in leaching processes is becoming increasingly popular in hydrometallurgy. This paper deals with combining these two techniques for silver leaching from solid waste of a cyanidation leach plant located in Kutahya, Turkey. The primary aim of this research is to assess the technical performance of the method. To achieve maximum leaching yield, eight process variables have been selected to estimate optimum process conditions by means of statistical factorial design and steepest ascent techniques. Laboratory-scale experiments showed that complete leaching of silver may be achieved by this process. (C) 2003 Elsevier B.V. All rights reserved

A novel approach for treatment of sacrococcygeal pilonidal sinus: less is more

BACKGROUND: The surgical management of sacrococcygeal pilonidal sinus (PS) is still a matter of discussion. Therapy ranges from complete wide excision with or without closure of the wound to excochleation of the sinus with a brush. In this paper, we introduce a novel limited excision technique. The aim of this study was to assess the morbidity and recurrence rate of this technique. MATERIALS AND METHODS: Limited excision consisted of a selective extirpation of the sinus after tagging the tract with methylene blue. Ninety-three consecutive patients, who underwent surgery between 2001 and 2004, were analyzed. The patients' survey was performed by mail questionnaire and telephone interview inquiring recurrence, time off work, and time to wound healing. RESULTS: Seventy-three percent of the patients were treated in an outpatient setting. With a median follow-up of 2 years, the recurrence rate was 5%. The median time off work was 2 weeks. The median wound healing time was 5 weeks. CONCLUSION: Limited excision for PS can be done in an outpatient setting with a low recurrence rate and short time off work