10 research outputs found

    Measurement of the dependence of transverse energy production at large pseudorapidity on the hard-scattering kinematics of proton-proton collisions at √s=2.76 TeV with ATLAS

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    The relationship between jet production in the central region and the underlying-event activity in a pseudorapidity-separated region is studied in 4.0 pb-1 of s=2.76 TeV pp collision data recorded with the ATLAS detector at the LHC. The underlying event is characterised through measurements of the average value of the sum of the transverse energy at large pseudorapidity downstream of one of the protons, which are reported here as a function of hard-scattering kinematic variables. The hard scattering is characterised by the average transverse momentum and pseudorapidity of the two highest transverse momentum jets in the event. The dijet kinematics are used to estimate, on an event-by-event basis, the scaled longitudinal momenta of the hard-scattered partons in the target and projectile beam-protons moving toward and away from the region measuring transverse energy, respectively. Transverse energy production at large pseudorapidity is observed to decrease with a linear dependence on the longitudinal momentum fraction in the target proton and to depend only weakly on that in the projectile proton. The results are compared to the predictions of various Monte Carlo event generators, which qualitatively reproduce the trends observed in data but generally underpredict the overall level of transverse energy at forward pseudorapidity

    Measurement of W boson angular distributions in events with high transverse momentum jets at s√= 8 TeV using the ATLAS detector

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    The W boson angular distribution in events with high transverse momentum jets is measured using data collected by the ATLAS experiment from proton–proton collisions at a centre-of-mass energy at the Large Hadron Collider, corresponding to an integrated luminosity of . The focus is on the contributions to processes from real W emission, which is achieved by studying events where a muon is observed close to a high transverse momentum jet. At small angular separations, these contributions are expected to be large. Various theoretical models of this process are compared to the data in terms of the absolute cross-section and the angular distributions of the muon from the leptonic W decay.Fil: Aaboud, M.. Université Mohamed Premier and LPTPM; MarruecosFil: Aad, G.. Aix-Marseille Université ; FranciaFil: Abbott, B.. Oklahoma State University; Estados UnidosFil: Abdallah, J.. Academia Sinica; ChinaFil: Abdinov, O.. Azerbaijan Academy of Sciences; AzerbaiyánFil: Alconada Verzini, María Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Alonso, Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Arduh, Francisco Anuar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Dova, Maria Teresa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Hoya, Joaquín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Monticelli, Fernando Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Wahlberg, Hernan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Bossio Sola, Jonathan David. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Marceca, Gino. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Otero y Garzon, Gustavo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Piegaia, Ricardo Nestor. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Sacerdoti, Sabrina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Zibell. A.. Julius-Maximilians-Universität ; AlemaniaFil: Zieminska, D.. Indiana University; Estados UnidosFil: Zimine, N. I.. Joint Institute for Nuclear Research; RusiaFil: Zimmermann, C.. Universität Mainz ; AlemaniaFil: Zimmermann, S.. Albert-Ludwigs-Universität ; AlemaniaFil: Zinonos, Z.. Georg-August-Universität ; AlemaniaFil: Zinser, M.. Universität Mainz ; AlemaniaFil: Ziolkowski, M.. Universität Siegen ; AlemaniaFil: Živković, L.. University of Belgrade ; SerbiaFil: Zobernig, G.. University of Wisconsin; Estados UnidosFil: Zoccoli, A.. Università di Bologna ; ItaliaFil: Nedden, M. zur. Humboldt University; AlemaniaFil: Zurzolo, G.. Università di Napoli; ItaliaFil: Zwalinski, L.. Cern - European Organization For Nuclear Research; SuizaFil: The ATLAS Collaboration. No especifica

    Erratum: Search for Resonant and Nonresonant Higgs Boson Pair Production in the bb[over ¯]τ^{+}τ^{-} Decay Channel in pp Collisions at sqrt[s]=13  TeV with the ATLAS Detector [Phys. Rev. Lett. 121, 191801 (2018)]

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    Operation and performance of the ATLAS Tile Calorimeter in Run 1

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    The Tile Calorimeter is the hadron calorimeter covering the central region of the ATLAS experiment at the Large Hadron Collider. Approximately 10,000 photomultipliers collect light from scintillating tiles acting as the active material sandwiched between slabs of steel absorber. This paper gives an overview of the calorimeter’s performance during the years 2008–2012 using cosmic-ray muon events and proton–proton collision data at centre-of-mass energies of 7 and 8TeV with a total integrated luminosity of nearly 30 fb−1. The signal reconstruction methods, calibration systems as well as the detector operation status are presented. The energy and time calibration methods performed excellently, resulting in good stability of the calorimeter response under varying conditions during the LHC Run 1. Finally, the Tile Calorimeter response to isolated muons and hadrons as well as to jets from proton–proton collisions is presented. The results demonstrate excellent performance in accord with specifications mentioned in the Technical Design Report

    Search for high-mass new phenomena in the dilepton final state using proton-proton collisions at s=13\sqrt{s}=13 TeV with the ATLAS detector

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    A search is conducted for both resonant and non-resonant high-mass new phenomena in dielectron and dimuon final states. The search uses 3.2 fb1^{-1} of proton-proton collision data, collected at s=13\sqrt{s} = 13 TeV by the ATLAS experiment at the LHC in 2015. The dilepton invariant mass is used as the discriminating variable. No significant deviation from the Standard Model prediction is observed; therefore limits are set on the signal model parameters of interest at 95% credibility level. Upper limits are set on the cross-section times branching ratio for resonances decaying to dileptons, and the limits are converted into lower limits on the resonance mass, ranging between 2.74 TeV and 3.36 TeV, depending on the model. Lower limits on the qq\ell\ell qq contact interaction scale are set between 16.7 TeV and 25.2 TeV, also depending on the model

    Search for scalar leptoquarks in pp\mathit{pp} collisions at s=13\sqrt{s}=13 TeV with the ATLAS experiment

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    An inclusive search for a new-physics signature of lepton-jet resonances has been performed by the ATLAS experiment. Scalar leptoquarks, pair-produced in pp collisions at s√ = 13 TeV at the large hadron collider, have been considered. An integrated luminosity of 3.2 fb(−)(1), corresponding to the full 2015 dataset was used. First (second) generation leptoquarks were sought in events with two electrons (muons) and two or more jets. The observed event yield in each channel is consistent with Standard Model background expectations. The observed (expected) lower limits on the leptoquark mass at 95% confidence level are 1100 and 1050 GeV (1160 and 1040 GeV) for first and second generation leptoquarks, respectively, assuming a branching ratio into a charged lepton and a quark of 100%. Upper limits on the aforementioned branching ratio are also given as a function of leptoquark mass. Compared with the results of earlier ATLAS searches, the sensitivity is increased for leptoquark masses above 860 GeV, and the observed exclusion limits confirm and extend the published results

    Erratum to: Search for exclusive Higgs and Z boson decays to φγ and ργ with the ATLAS detector

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    A strategy for a general search for new phenomena using data-derived signal regions and its application within the ATLAS experiment

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    This paper describes a strategy for a general search used by the ATLAS Collaboration to find potential indications of new physics. Events are classified according to their final state into many event classes. For each event class an automated search algorithm tests whether the data are compatible with the Monte Carlo simulated expectation in various distributions sensitive to the effects of new physics. The significance of a deviation is quantified using pseudo-experiments. A data selection with a significant deviation defines a signal region for a dedicated follow-up analysis with an improved background expectation. The analysis of the data-derived signal regions on a new dataset allows a statistical interpretation without the large look-elsewhere effect. The sensitivity of the approach is discussed using Standard Model processes and benchmark signals of new physics. As an example, results are shown for 3.2 fb1^{-1} of proton-proton collision data at a centre-of-mass energy of 13 TeV collected with the ATLAS detector at the LHC in 2015, in which more than 700 event classes and more than 105^5 regions have been analysed. No significant deviations are found and consequently no data-derived signal regions for a follow-up analysis have been defined.Comment: 63 pages in total, author list starting page 47, 23 figures, 5 tables, final version published in Eur. Phys. J. C. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2016-38

    Search for bottom squark pair production in proton-proton collisions at root s=13 TeV with the ATLAS detector

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    The result of a search for pair production of the supersymmetric partner of the Standard Model bottom quark ((b) over tilde (1)) is reported. The search uses 3.2 fb(-1) of pp collisions at root s = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider in 2015. Bottom squarks are searched for in events containing large missing transverse momentum and exactly two jets identified as originating from b-quarks. No excess above the expected Standard Model background yield is observed. Exclusion limits at 95 % confidence level on the mass of the bottom squark are derived in phenomenological supersymmetric R-parity-conserving models in which the (b) over tilde (1) is the lightest squark and is assumed to decay exclusively via (b) over tilde (1) -> b (chi) over tilde (0)(1), where (chi) over tilde (0)(1) is the lightest neutralino. The limits significantly extend previous results; bottom squark masses up to 800 (840) GeV are excluded for the. (chi) over tilde (0)(1) mass below 360 (100) GeV whilst differences in mass above 100 GeV between the (b) over tilde (1) and the (chi) over tilde (0)(1) are excluded up to a (b) over tilde (1) mass of 500 GeV

    Weaving ways of knowing to enhance biocultural resilience in a mahinga kai species-at-risk

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    The futures of many threatened species rest on our collective efforts to reweave the biological, cultural, and linguistic threads that together comprise biocultural diversity. For Western researchers, there is growing recognition that Indigenous Peoples and local communities are at the forefront of place-based approaches that bring together diverse ways of knowing and seeing. Here in Aotearoa New Zealand, these include restoration efforts led by mana whenua tribal groups with local authority to weave Māori—the Indigenous Peoples of Aotearoa New Zealand—knowledge, practices, and processes with Western science. For example, genomic markers offer a unique lens to explore relationships across populations, and in turn, co-develop management programmes that build resilience in threatened species. A growing number of studies are applying genomic data to enhance conservation outcomes, but few have tapped into their full potential by weaving these data with Indigenous and local relationships of place. This thesis represents the collective efforts of many—including whānau extended families, researchers, and practitioners, many of whom affiliate to the local iwi tribe, Ngāi Tahu—led here by a Pākehā (New Zealander of European settler descent) researcher. The recent application of genomic tools by Western-trained researchers to address conservation issues (i.e., conservation genomics) presents both opportunities and challenges for efforts to restore biocultural diversity. This thesis seeks to consider such complexities, including how genomic data might be better understood through a multiplicity of worldviews. Chapter Two serves to frame the research narrative of this thesis through a Perspective published in People and Nature’s joint special issue on informing decision-making with Indigenous and local knowledge and science. Few published conservation translocations (i.e., movement of animals or plants for conservation benefit) are led or co-led by Indigenous Peoples or centre Indigenous knowledge systems. As Kāi Tahu and Pākehā researchers and practitioners working in partnership in Aotearoa New Zealand, we consider how conservation translocations that weave diverse ways of knowing and seeing can enhance species recovery and build ecosystem resilience. We highlight the co-development of conservation translocations with Te Kōhaka o Tūhaitara and Te Nohoaka o Tukiauau Trusts where we are weaving emerging genomic approaches with mātauraka Māori Māori knowledge systems to recover culturally significant freshwater species. We further offer a Two-Eyed Seeing framework to support the co- design of conservation translocations led or co-led by Indigenous researchers and communities around the world. Chapter Three extends the narrative introduced in Chapter Two by focusing on the caveats of interpreting genomic data without local historical or contemporary context; namely, the movement or management of culturally significant species by Indigenous Peoples and local communities (IPLCs) in the distant or recent past. This Perspective brings together Kāi Tahu and Pākehā researchers and practitioners with expertise across customary and contemporary mahika kai food gathering (i.e., including processes, practices, and places), conservation genomics, ecology, fish biology, and aquaculture. To date, few efforts to characterise genetic variation within and between populations consider how human relationships with place may shape present-day species distributions. Yet, the movement of species by Indigenous and local communities in the distant and recent past provides important context for the interpretation of genomic data. For example, freshwater kōura1 crayfish in subalpine streams alongside ancient walking trails in Te Waipounamu (the South Island of Aotearoa New Zealand) were moved between sites to provide readily accessible food for travellers. We reflect on how weaving diverse ways of knowing and seeing can better reveal the biocultural complexities of genomic data derived from culturally significant species such as kōura, including locally adaptive variation. In Chapter Four, we shift focus to a research partnership with aquaculture company KEEWAI, mana whenua, and Te Rūnanga o Ngāi Tahu (TRoNT). This chapter reflects on the benefits, risks, and outstanding questions around genetic rescue (i.e., the introduction or restoration of new genetic material to small, isolated populations to reduce genetic load). We present experimental co-design and preliminary genomic data as proof-of-concept for a series of kōura translocation experiments at the KEEWAI aquaculture ponds ultimately intended to grow our understanding of the genetic mechanisms underlying genetic rescue. These data contribute toward the foundation and development of a multi-generational research programme that will support tribal-led aquaculture initiatives for kōura and other mahika kai species across the Kāi Tahu takiwā tribal territory. The research partnerships and approaches described above are brought together in Chapter Five to explore contemporary and historical relationships across kēkēwai1 freshwater crayfish populations in Te Waipounamu by weaving genomic data with placed-based knowledges. Genomic data reveal strong population genetic structure—as well as signatures of population admixture—across seventeen genetically depauperate populations in Te Waipounamu. Differentiation and environment association analyses further identify patterns of genetic variation linked to hydroclimatic variables, including temperature, precipitation, and water flow regimes. We consider how weaving these data with place-based knowledges can enhance resilience in kēkēwai through tribal-led initiatives for mahika kai. Our findings further contribute toward a growing understanding of how adaptive and neutral genetic variation shape threatened species’ capacity to respond to future change. Finally, Chapter Six critically reflects on the journey of this thesis and future directions, including tribal-led research programmes that will strengthen the relationships between people and mahika kai to build intergenerational capacity for protecting biocultural heritage. Two additional manuscripts, three blogs and an example summary for mana whenua are also included in the appendices. Together, these works contribute toward reconnection to place and the growth of our collective knowledge for treasured species in Aotearoa New Zealand and beyond
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