Showing papers by "Marcel Michael Stanitzki published in 2018"
TL;DR: In this paper, a search for new phenomena in final states with an energetic jet and large missing transverse momentum is reported, and the results are translated into exclusion limits in models with pair-produced weakly interacting dark-matter candidates, large extra spatial dimensions, and supersymmetric particles in several compressed scenarios.
Abstract: Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses proton-proton collision data corresponding to an integrated luminosity of 36.1 fb−1 at a centre-of-mass energy of 13 TeV collected in 2015 and 2016 with the ATLAS detector at the Large Hadron Collider. Events are required to have at least one jet with a transverse momentum above 250 GeV and no leptons (e or μ). Several signal regions are considered with increasing requirements on the missing transverse momentum above 250 GeV. Good agreement is observed between the number of events in data and Standard Model predictions. The results are translated into exclusion limits in models with pair-produced weakly interacting dark-matter candidates, large extra spatial dimensions, and supersymmetric particles in several compressed scenarios.
358 citations
TL;DR: In this article, the observed significance is 5.8 standard deviations, compared to an expectation of 4.9 standard deviations and the observed (expected) significance is 6.3 (5.1) standard deviations.
306 citations
TL;DR: In this paper, the properties of the Higgs boson were measured in the two-photon final state using 36.1 fb-1 of proton? proton collision data recorded at ffiffi √s = 13 TeV by the ATLAS experiment at the Large Hadron Collider.
Abstract: Properties of the Higgs boson are measured in the two-photon final state using 36.1 fb-1 of proton? proton collision data recorded at ffiffi √s = 13 TeV by the ATLAS experiment at the Large Hadron Collider. Cross-section measurements for the production of a Higgs boson through gluon-gluon fusion, vectorboson fusion, and in association with a vector boson or a top-quark pair are reported. The signal strength, defined as the ratio of the observed to the expected signal yield, is measured for each of these production processes as well as inclusively. The global signal strength measurement of 0.99 ± 0.14 improves on the precision of the ATLAS measurement at √s = 7 and 8 TeV by a factor of two. Measurements of gluon-gluon fusion and vector-boson fusion productions yield signal strengths compatible with the Standard Model prediction. Measurements of simplified template cross sections, designed to quantify the different Higgs boson production processes in specific regions of phase space, are reported. The cross section for the production of the Higgs boson decaying to two isolated photons in a fiducial region closely matching the experimental selection of the photons is measured to be 55 ± 10 fb, which is in good agreement with the Standard Model prediction of 64 ± 2 fb. Furthermore, cross sections in fiducial regions enriched in Higgs boson production in vector-boson fusion or in association with large missing transverse momentum, leptons or top-quark pairs are reported. Differential and double-differential measurements are performed for several variables related to the diphoton kinematics as well as the kinematics and multiplicity of the jets produced in association with a Higgs boson. These differential cross sections are sensitive to higher order QCD corrections and properties of the Higgs boson, such as its spin and CP quantum numbers. No significant deviations from a wide array of Standard Model predictions are observed. Finally, the strength and tensor structure of the Higgs boson interactions are investigated using an effective Lagrangian, which introduces additional CP-even and CP-odd interactions. No significant new physics contributions are observed.
251 citations
TL;DR: A search for the decay of the Standard Model Higgs boson into a bb¯ pair when produced in association with a W or Z boson is performed with the ATLAS detector as mentioned in this paper.
221 citations
TL;DR: In this article, a search for an invisibly decaying Higgs boson or dark matter candidates produced in association with a leptonically decaying Z boson in proton-proton collisions at s = 13 TeV is presented.
115 citations
TL;DR: In this article, a search for the standard model Higgs boson produced in association with a top-quark pair, t(t)overbarH, is presented using 36.1 fb(-1) of pp collision data at root s = 13 TeV collecte...
Abstract: A search for the standard model Higgs boson produced in association with a top-quark pair, t(t)overbarH, is presented. The analysis uses 36.1 fb(-1) of pp collision data at root s = 13 TeV collecte ...
108 citations
TL;DR: In this article, a search for a heavy neutral Higgs boson decaying into a Z boson and another heavy Higgs Boson, H, was performed using a data sample corresponding to an integrated luminosity of 36.1 fb(-1) from...
104 citations
TL;DR: In this article, a search for electroweak production of supersymmetric particles using recursive jigsaw reconstruction was performed in two-and three-lepton final states using a technique that assigns reconstructed objects to the most probable hemispheres of the decay trees.
Abstract: A search for electroweak production of supersymmetric particles is performed in two-lepton and three-lepton final states using recursive jigsaw reconstruction, a technique that assigns reconstructed objects to the most probable hemispheres of the decay trees, allowing one to construct tailored kinematic variables to separate the signal and background. The search uses data collected in 2015 and 2016 by the ATLAS experiment in s=13 TeV proton-proton collisions at the CERN Large Hadron Collider corresponding to an integrated luminosity of 36.1 fb-1. Chargino-neutralino pair production, with decays via W/Z bosons, is studied in final states involving leptons and jets and missing transverse momentum for scenarios with large and intermediate mass splittings between the parent particle and lightest supersymmetric particle, as well as for the scenario where this mass splitting is close to the mass of the Z boson. The latter case is challenging since the vector bosons are produced with kinematic properties that are similar to those in Standard Model processes. Results are found to be compatible with the Standard Model expectations in the signal regions targeting large and intermediate mass splittings, and chargino-neutralino masses up to 600 GeV are excluded at 95% confidence level for a massless lightest supersymmetric particle. Excesses of data above the expected background are found in the signal regions targeting low mass splittings, and the largest local excess amounts to 3.0 standard deviations. © 2018 CERN, for the ATLAS Collaboration. Published by the American Physical Society.
97 citations
TL;DR: In this article, the coupling properties of the Higgs boson were studied in the four-lepton (e, μ) decay channel using 36.1 fb−1 collision data from the LHC at a centre-of-mass energy of 13 TeV collected by the ATLAS detector.
Abstract: The coupling properties of the Higgs boson are studied in the four-lepton (e, μ) decay channel using 36.1 fb−1 of pp collision data from the LHC at a centre-of-mass energy of 13 TeV collected by the ATLAS detector. Cross sections are measured for the main production modes in several exclusive regions of the Higgs boson production phase space and are interpreted in terms of coupling modifiers. The inclusive cross section times branching ratio for H → ZZ∗ decay and for a Higgs boson absolute rapidity below 2.5 is measured to be 1. 73 − 0.23 + 0.24 (stat.) − 0.08 + 0.10 (exp.) ± 0.04(th.) pb compared to the Standard Model prediction of 1.34±0.09 pb. In addition, the tensor structure of the Higgs boson couplings is studied using an effective Lagrangian approach for the description of interactions beyond the Standard Model. Constraints are placed on the non-Standard-Model CP-even and CP-odd couplings to Z bosons and on the CP-odd coupling to gluons.
96 citations
TL;DR: In this paper, a measurement of off-shell Higgs boson production was performed using data from proton-proton collisions at a center-of-mass energy of s=13 TeV.
87 citations
TL;DR: This Letter documents a measurement of the first jet substructure quantity at a hadron collider to be calculated at next-to-next- to-leading-logarithm accuracy.
Abstract: Jet substructure observables have significantly extended the search program for physics beyond the standard model at the Large Hadron Collider. The state-of-the-art tools have been motivated by the ...
TL;DR: In this paper, measurements of ZZ production in the l(+)l(-)l'l'(+) l'(-) channel in proton-proton collisions at 13 TeV center-of-mass energy at the Large Hadron Collider are presented.
Abstract: Measurements of ZZ production in the l(+)l(-)l'(+)l'(-) channel in proton-proton collisions at 13 TeV center-of-mass energy at the Large Hadron Collider are presented. The data correspond to 36.1 f ...
TL;DR: In this paper, a search for resonant and nonresonant pair production of Higgs bosons in the b (b) over bar tau(+)tau(-) final state is presented.
Abstract: A search for resonant and nonresonant pair production of Higgs bosons in the b (b) over bar tau(+)tau(-) final state is presented. The search uses 36.1 fb(-1) of pp collision data with root s = 13 ...
TL;DR: In this paper, a neural network was used to improve the background rejection and extract the signal of top quark production in the collision data collected by the ATLAS experiment at the LHC in 2015 and 2016.
TL;DR: In this paper, a search for pair production of the supersymmetric partners of the Higgs boson (higgsinos H˜) in gauge-mediated scenarios is reported.
Abstract: A search for pair production of the supersymmetric partners of the Higgs boson (higgsinos H˜) in gauge-mediated scenarios is reported Each higgsino is assumed to decay to a Higgs boson and a gravitino Two complementary analyses, targeting high- and low-mass signals, are performed to maximize sensitivity The two analyses utilize LHC pp collision data at a center-of-mass energy s=13 TeV, the former with an integrated luminosity of 361 fb-1 and the latter with 243 fb-1, collected with the ATLAS detector in 2015 and 2016 The search is performed in events containing missing transverse momentum and several energetic jets, at least three of which must be identified as b-quark jets No significant excess is found above the predicted background Limits on the cross section are set as a function of the mass of the H˜ in simplified models assuming production via mass-degenerate higgsinos decaying to a Higgs boson and a gravitino Higgsinos with masses between 130 and 230 GeV and between 290 and 880 GeV are excluded at the 95% confidence level Interpretations of the limits in terms of the branching ratio of the higgsino to a Z boson or a Higgs boson are also presented, and a 45% branching ratio to a Higgs boson is excluded for mH˜≈400 GeV
TL;DR: In this article, a combined measurement of differential and inclusive total cross sections of Higgs boson production is performed using 36.1 fb −1 of 13 TeV proton-proton collision data produced by the LHC and recorded by the ATLAS detector in 2015 and 2016.
TL;DR: In this paper, a search for the narrow structure X(5568) reported by the D0 Collaboration in the decay sequence X→B_{s}−π−±, B_{s−π −1}→J/ψϕ, is presented based on a data sample recorded with the ATLAS detector at the LHC.
Abstract: A search for the narrow structure, X(5568), reported by the D0 Collaboration in the decay sequence X→B_{s}^{0}π^{±}, B_{s}^{0}→J/ψϕ, is presented The analysis is based on a data sample recorded with the ATLAS detector at the LHC corresponding to 49 fb^{-1} of pp collisions at 7 TeV and 195 fb^{-1} at 8 TeV No significant signal was found Upper limits on the number of signal events, with properties corresponding to those reported by D0, and on the X production rate relative to B_{s}^{0} mesons, ρ_{X}, were determined at 95% confidence level The results are N(X)<382 and ρ_{X}<0015 for B_{s}^{0} mesons with transverse momenta above 10 GeV, and N(X)<356 and ρ_{X}<0016 for transverse momenta above 15 GeV Limits are also set for potential B_{s}^{0}π^{±} resonances in the mass range 5550 to 5700 MeV
TL;DR: In this paper, a search for the direct pair production of the stop, the supersymmetric partner of the top quark, was presented for the R-parity-violating coupling to a final state with two leptons.
Abstract: A search is presented for the direct pair production of the stop, the supersymmetric partner of the top quark, that decays through an R-parity-violating coupling to a final state with two leptons a ...
TL;DR: In this article, a search for a heavy resonance decaying into WZ in the fully leptonic channel (electrons and muons) is performed based on proton-proton collision data collected by the ATLAS experiment at the Large Hadron Collider at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 36.1 fb −1.
TL;DR: In this paper, the dynamics of isolated-photon production in association with a jet in proton-proton collisions at a centre-of-mass energy of 13 TeV were studied with the ATLAS detector at the LHC using a dataset with an integrated luminosity of 3.2 fb −1.
TL;DR: In this paper, a measurement of the fragmentation functions of jets into charged particles in $p$+Pb collisions and $pp$ collisions is presented, using 28 nb$^{-1}$ and 26 pb$€-1$ of $pp€ data, both at $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV, collected in 2013 and 2015 with the ATLAS detector at the LHC.
TL;DR: In this paper, a measurement of the production of three isolated photons in proton-proton collisions at a centre-of-mass energy s=8 TeV is reported, based on an integrated luminosity of 20.2 fb −1 collected with the ATLAS detector at the LHC.
TL;DR: In this paper, the results of a search for gluino pair production with subsequent R-parity-violating decays to quarks are presented using 36.1 fb(-1) of data collected by the ATLAS detector in proton-protector networks.
TL;DR: In this article, the measurement of differential cross sections of isolated prompt photons produced in association with a b-jet or a c-jet was presented, which provided sensitivity to the heavy-f...
TL;DR: A normalized differential cross-section measurement in a fiducial phase-space region where interference effects between top-quark pair production and associated production of a single top quark with a W boson and a b-quarks are significant is presented.
Abstract: This Letter presents a normalized differential cross-section measurement in a fiducial phase-space region where interference effects between top-quark pair production and associated production of a single top quark with a W boson and a b-quark are significant. Events with exactly two leptons (ee, μμ, or eμ) and two b-tagged jets that satisfy a multiparticle invariant mass requirement are selected from 36.1 fb^{-1} of proton-proton collision data taken at sqrt[s]=13 TeV with the ATLAS detector at the LHC in 2015 and 2016. The results are compared with predictions from simulations using various strategies for the interference. The standard prescriptions for interference modeling are significantly different from each other but are within 2σ of the data. State-of-the-art predictions that naturally incorporate interference effects provide the best description of the data in the measured region of phase space most sensitive to these effects. These results provide an important constraint on interference models and will guide future model development and tuning.
TL;DR: In this paper, a search for exotic decays of the Higgs boson to a pair of new (pseudo)scalar particles, H→aa, where the a particle has a mass in the range 20-60 GeV, was presented.
TL;DR: In this paper, a search for heavy resonances decaying into a Higgs boson and a new particle (X) was reported, utilizing 36.1 fb(-1) of proton-proton collision data at root s = 13 TeV collected during 2015 and 2016.
DOI•
01 Jan 2018
TL;DR: Recommendations for accelerator and detector design optimizations are given, with which the background level in the SiD detector can be reduced in order to reach the aimed-for precision at the ILC.
Abstract: Der "International Linear Collider" (ILC) ist ein geplanter Linearbeschleuniger fur die Kollisionen von Elektronen und Positronen bei einer anfanglichen Schwerpunktsenergie von 250 GeV. Mit seinen Forschungszielen steht er in einem erganzenden Zusammenhang mit dem "Large Hadron Collider" (LHC). Denn nach der Entdeckung des Higgs-Bosons am LHC in 2012 ist eines der Ziele des ILC, die Eigenschaften und Wechselwirkungen des Higgs-Bosons und des Top-Quarks mit nie dagewesener Prazision zu messen. Auch die Suche nach Teilchen aus Modellen jenseits des Standardmodells, welche ebenfalls auf dem Programm der verschiedenen ILC-Phasen steht, wird durch diese Prazision erleichtert.
Sowohl das Layout des Beschleunigers als auch das der Detektoren muss optimiert werden, um Untergrundraten unterhalb einer gewissen Grenze zu halten und damit die angestrebte Prazision zu erreichen. Hierzu wurden einige Studien durchgefuhrt, um verschiedene Untergrundquellen zu untersuchen und die Raten im SiD Detektor, einer der beiden fur den ILC vorgeschlagenen Detektorexperimente, zu analysieren. Diese Studien basieren auf Monte Carlo Generatoren, welche Untergrundereignisse aus verschiedenen Quellen simulieren. Nach einer vollen Detektorsimulation wurden diese Ereignisse dann in Hinsicht auf die SiD Detektorokkupanz beurteilt. Liegt diese Okkupanz nahe oder sogar oberhalb der von der SiD-Gruppe festgelegten Akzeptanzgrenze, so wurden Vorschlage zur Beschleuniger- und Detektoroptimierung unterbreitet und getestet, mit denen die Okkupanz reduziert werden kann.
Zu den hier untersuchten Untergrunden gehoren sowohl der e+e- - Paaruntergrund, der durch die Wechselwirkung der elektromagnetischen Felder der kollidierenden Strahlbundel entsteht, als auch der Myonen-Maschinenuntergrund aus der Wechselwirkung des Strahls mit den Beschleunigerinstrumenten, sowie der Neutronenuntergrund, der von den Strahl-Dumps aus in Richtung der Detektoren gerichtet ist. Zusatzliche Simulationen umfassen die Untersuchung des Designs der Strahl-Dumps im Hinblick auf die Bestrahlungsdosis in der Dump-Halle. Die Abhangigkeit des e+e- - Paaruntergrundes von den ILC-Strahlparametern wurde fur die in 2017 beantragte Anderung der Parameter fur die erste ILC-Phase evaluiert.
Die Ergebnisse der in der vorliegenden Arbeit prasentierten Studie haben dabei zur Entscheidungsfindung masgeblich beigetragen. Neben den Simulationsstudien wurden auch Messungen in der japanischen Beschleunigeranlage "Accelerator Test Facility 2" durchgefuhrt, um die Maschinenuntergrundrate in Abhangigkeit von verschiedenen Beschleunigerzustanden zu messen. Das Ziel war hierbei die Funktionalitat eines Strahlkollimators zu testen.
Bei allen prasentierten Studien werden Vorschlage zur Beschleuniger- und Detektoroptimierung genannt, um die Untergrundraten in SiD zu reduzieren und somit die geplanten Prazisionsmessungen ermoglichen.
Posted Content•
TL;DR: The LYCORIS Large Area Silicon Strip Telescope for the DESY II Test Beam Facility is presented in this article, which provides elec- tron and positron beams for beam tests of up to 6 GeV.
Abstract: The LYCORIS Large Area Silicon Strip Telescope for the DESY II Test Beam Facility is presented. The DESY II Test Beam Facility provides elec- tron and positron beams for beam tests of up to 6 GeV. A new telescope with a large 10x20 cm$^2$ coverage area based on a 25 {\mu}m pitch strip sensor is to be installed within the PCMAG 1 T solenoid. The current state of the system is presented.
01 Nov 2018
TL;DR: Prototypes has been developed based on the GBTx and GBT-SCA chip family and SFP+ optical links to understand the design issues, the behavior of the EoS and the detector level integration for the ATLAS experiment.
Abstract: For the ATLAS experiment a new Silicon tracker is necessary for the High-Luminosity Upgrade of the LHC. The main building blocks for the strip tracker is a module which consists of a silicon sensor, readout ASICs and a hybrid PCB. Up to 28 modules are placed on long substructures. An End-of-Substructure (EoS) card provides common connections for data, commands and power to the off-detector systems. Prototypes has been developed based on the GBTx and GBT-SCA chip family and SFP+ optical links to understand the design issues, the behavior of the EoS and the detector level integration. Presented will be the design of the electronics, the exercised tests for electrical behavior, mechanical deformation and thermal behavior.