75 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

    Measurement of the nuclear modification factor for muons from charm and bottom hadrons in Pb+Pb collisions at 5.02 TeV with the ATLAS detector

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    Heavy-flavour hadron production provides information about the transport properties and microscopic structure of the quark-gluon plasma created in ultra-relativistic heavy-ion collisions. A measurement of the muons from semileptonic decays of charm and bottom hadrons produced in Pb+Pb and pp collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV with the ATLAS detector at the Large Hadron Collider is presented. The Pb+Pb data were collected in 2015 and 2018 with sampled integrated luminosities of 208 mu b(-1) and 38 mu b(-1), respectively, and pp data with a sampled integrated luminosity of 1.17 pb(-1) were collected in 2017. Muons from heavy-flavour semileptonic decays are separated from the light-flavour hadronic background using the momentum imbalance between the inner detector and muon spectrometer measurements, and muons originating from charm and bottom decays are further separated via the muon track's transverse impact parameter. Differential yields in Pb+Pb collisions and differential cross sections in pp collisions for such muons are measured as a function of muon transverse momentum from 4 GeV to 30 GeV in the absolute pseudorapidity interval vertical bar eta vertical bar < 2. Nuclear modification factors for charm and bottom muons are presented as a function of muon transverse momentum in intervals of Pb+Pb collision centrality. The bottom muon results are the most precise measurement of b quark nuclear modification at low transverse momentum where reconstruction of B hadrons is challenging. The measured nuclear modification factors quantify a significant suppression of the yields of muons from decays of charm and bottom hadrons, with stronger effects for muons from charm hadron decays

    A search for an unexpected asymmetry in the production of e+μ− and e−μ+ pairs in proton-proton collisions recorded by the ATLAS detector at root s = 13 TeV

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    This search, a type not previously performed at ATLAS, uses a comparison of the production cross sections for e(+)mu(-) and e(-)mu(+) pairs to constrain physics processes beyond the Standard Model. It uses 139 fb(-1) of proton-proton collision data recorded at root s = 13 TeV at the LHC. Targeting sources of new physics which prefer final states containing e(+)mu(-) and e(-)mu(+), the search contains two broad signal regions which are used to provide model-independent constraints on the ratio of cross sections at the 2% level. The search also has two special selections targeting supersymmetric models and leptoquark signatures. Observations using one of these selections are able to exclude, at 95% confidence level, singly produced smuons with masses up to 640 GeV in a model in which the only other light sparticle is a neutralino when the R-parity-violating coupling lambda(23)(1)' is close to unity. Observations using the other selection exclude scalar leptoquarks with masses below 1880 GeV when g(1R)(eu) = g(1R)(mu c) = 1, at 95% confidence level. The limit on the coupling reduces to g(1R)(eu) = g(1R)(mu c) = 0.46 for a mass of 1420 GeV

    A search for an excited muon decaying to a muon and two jets in pp collisions at √s = 8 TeV with the ATLAS detector

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    A new search signature for excited leptons is explored. Excited muons are sought in the channel ppμμμμ jet jetpp \to \mu\mu^* \to \mu \mu\textrm{ jet jet}, assuming both the production and decay occur via a contact interaction. The analysis is based on 20.3 fb1^{-1} of pppp collision data at a centre-of-mass energy of s\sqrt{s} = 8 TeV taken with the ATLAS detector at the Large Hadron Collider. No evidence of excited muons is found, and limits are set at the 95% confidence level on the cross section times branching ratio as a function of the excited-muon mass mμm_{\mu^*}. For mμm_{\mu^*} between 1.3 TeV and 3.0 TeV, the upper limit on σB(μμqqˉ\sigma B(\mu^* \to \mu q \bar{q}) is between 0.6 and 1 fb. Limits on σB\sigma B are converted to lower bounds on the compositeness scale Λ\Lambda. In the limiting case Λ=mμ\Lambda = m_{\mu^*}, excited muons with a mass below 2.9 TeV are excluded. With the same model assumptions, these limits at larger μ\mu^* masses improve upon previous limits from traditional searches based on the gauge-mediated decay μμγ\mu^* \to \mu \gamma.Comment: 33 pages in total, author list starting page 16, 4 figures, 5 tables, final version published by New Journal of Physics including corrections in Erratum https://dx.doi.org/10.1088/1367-2630/ab46ed. All figures including auxiliary are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2015-0

    Search for anomalous electroweak production of WW/WZ in association with a high-mass dijet system in pp collisions at √s=8  TeV with the ATLAS detector

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    A search is presented for anomalous quartic gauge boson couplings in vector-boson scattering. The data for the analysis correspond to 20.220.2 fb1^{-1} of s=8\sqrt{s}=8 TeV pppp collisions, and were collected in 2012 by the ATLAS experiment at the Large Hadron Collider. The search looks for the production of WWWW or WZWZ boson pairs accompanied by a high-mass dijet system, with one WW decaying leptonically, and a WW or ZZ decaying hadronically. The hadronically decaying W/ZW/Z is reconstructed as either two small-radius jets or one large-radius jet using jet substructure techniques. Constraints on the anomalous quartic gauge boson coupling parameters α4\alpha_4 and α5\alpha_5 are set by fitting the transverse mass of the diboson system, and the resulting 95% confidence intervals are 0.024<α4<0.030-0.024<\alpha_4<0.030 and 0.028<α5<0.033-0.028<\alpha_5<0.033.Comment: 38 pages in total, author list starting page 22, 5 figures, 2 tables, published in Phys. Rev. D. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2015-09

    Attempted validation of the NUn score and inflammatory markers as predictors of esophageal anastomotic leak and major complications

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    The ability to predict complications following esophagectomy/extended total gastrectomy would be of great clinical value. A recent study demonstrated significant correlations between anastomotic leak (AL) and numerical values of C-reactive protein (CRP), white cell count (WCC) and albumin measured on postoperative day (POD) 4. A predictive model comprising all three (NUn score >10) was found to be highly sensitive and discriminant in predicting AL and complications. We attempted a retrospective validation in our center. Data were collected on all resections performed during a 5-year period (April 2008-2013) using prospectively maintained databases. Our biochemistry laboratory uses a maximum CRP value (156 mg/L), unlike that of the original study; otherwise all variables and outcome measures were comparable. Analysis was performed for all patients with complete blood results on POD4. Three hundred twenty-six patients underwent resection, of which 248 had POD4 bloods. There were 21 AL overall (6.44%); 16 among those with complete POD4 blood results (6.45%). There were 8 (2.45%) in-hospital deaths; 7 (2.82%) in those with POD4 results. No parameters were associated with AL or complication severity on univariate analysis. WCC was associated with AL in multivariate binary logistic regression with albumin and CRP (OR 1.23 [95% CI 1.03-1.47]; P = 0.021). When a binary variable of CRP ≥ 156 mg/L was used rather than an absolute value, no factors were significant. Mean NUn was 8.30 for AL, compared with 8.40 for non-AL (P = 0.710 independent t-test). NUn > 10 predicted 0 of 16 leaks (sensitivity 0.00%, specificity 94.4%, receiver operator curve [ROC] area under the curve [AUC] 0.485; P = 0.843). NUn > 7.65 was 93% sensitive and 21.6% specific. ROC for WCC alone was comparable with NUn (AUC 0.641 [0.504-0.779]; P = 0.059; WCC > 6.89 93.8% sensitive, 20.7% specific; WCC > 15 6.3% sensitive and 97% specific). There were no associations between any parameters and other complications. In a comparable cohort with the original study, we demonstrated a similar multivariate association between WCC alone on POD4 and subsequent demonstration of AL, but not albumin or CRP (measured up to 156 mg/L). The NUn score overall (calculated with this caveat) and a threshold of 10 was not found to have clinical utility in predicting AL or complications

    Orientação de dieta para realização da espectrofotometria do refluxo Recommended diet for reflux spectrophotometry

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    RACIONAL: O probe espectrofotométrico de detecção de refluxo duodenogastroesofágico, utilizando a bilirrubina como marcador, pode sofrer interferência de alimentos de forte coloração, gerando falsas leituras. OBJETIVO: Verificar a absorbância de 48 alimentos para identificar aqueles que não interferem com os resultados do probe espectrofotométrico. MÉTODOS: Os alimentos secos foram preparados com água ou leite e os outros triturados ou examinados in natura, no próprio recipiente de calibração do probe. RESULTADOS: A absorbância dos alimentos de cor fraca habitualmente é menor que 0,14 unidade, o limite normal para registros e traçados na pesquisa de refluxo biliar. Dos 48 alimentos testados, 32 demonstraram absorbância menor que o limite estabelecido, mostrando-se adequados, portanto, para serem administrados durante a realização da espectrofotometria. Ao contrário, 16 estão contra-indicados, podendo alterar os resultados do exame: ovo mexido, mingau de farinha láctea, feijão verde, beterraba, cenoura, chuchu, abobrinha, mandioquinha, milho verde cozido, laranja, caju, uva roxa, abacate, manga, mamão e pêssego. CONCLUSÃO: Alimentos com absorbância baixa são capazes de constituir agradável dieta, recomendável no período de exame.<br>BACKGROUND: The spectrophotometric probe, which uses bilirubin as a marker for the detection of duodenoesophagic reflux is subject to interference from strongly colored foods, which can cause erroneously high bilirubin absorbance readings. To overcome this problem it is necessary to ingest a diet that is free from such substances. OBJECTIVE: To test the absorbance of 48 different food substances in an in vitro environment. MATERIAL AND METHOD: Dry foods were blended with water or milk and non-dry solid foods were blended undiluted. It was utilized the proper calibration recipient to test them. RESULTS: The absorbance of weakly colored foods was usually lesser than the commonly accepted threshold of 0.14, and the absorbance of strongly colored foods was usually above this. Thirty-two from the 48 substances tested are suitable when the absorbance threshold is set at 0.14, but scrambled eggs, lacteous flour mush, green beans, beetroot, carrot, chayote, squash, "baroa" potato, boiled corn, orange, cashew, purple grape, avocado, mango, papaya and peach can alter the results and must be avoided. CONCLUSION: From the foods evaluated, enough are suitable at the 0.14 threshold to enable a suitable diet to be constructed for most patients during Bilitec studies

    Metabolic response at repeat PET/CT predicts pathological response to neoadjuvant chemotherapy in oesophageal cancer

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    Objectives Reports have suggested that a reduction in tumour 18F-fluorodeoxyglucose (FDG) uptake on positron emission tomography (PET) examination during or after neoadjuvant chemotherapy may predict pathological response in oesophageal cancer. Our aim was to determine whether metabolic response predicts pathological response to a standardised neoadjuvant chemotherapy regimen within a prospective clinical trial. Methods Consecutive patients staged with potentially curable oesophageal cancer who underwent treatment within a non-randomised clinical trial were included. A standardised chemotherapy regimen (two cycles of oxaliplatin and 5- fluorouracil) was used. PET/CT was performed before chemotherapy and repeated 24-28 days after the start of cycle 2. Results Forty-eight subjects were included: Mean age 65 years; 37 male. Using the median percentage reduction in SUVmax (42%) to define metabolic response, pathological response was seen in 71% of metabolic responders (17/24) compared with 33% of non-responders (8/24; P=0.009, sensitivity 68%, specificity 70%). Pathological response was seen in 81% of subjects with a complete metabolic response (13/16) compared with 38% of those with a less than complete response (12/32; P=0.0042, sensitivity 52%, specificity 87%). There was no significant histology-based effect. Conclusions There was a significant association between metabolic response and pathological response; however, accuracy in predicting pathological response was relatively low. Key Points ̇ PET/CT may predict tumour response to chemotherapy in oesophageal cancer. ̇ This was a prospective study using a standardised chemotherapy regimen. ̇ A significant association between PET/CT findings and disease response was found. ̇ However accuracy in predicting pathological response was relatively low. © European Society of Radiology 2012

    Metabolic response at repeat PET/CT predicts pathological response to neoadjuvant chemotherapy in oesophageal cancer

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    Objectives Reports have suggested that a reduction in tumour 18F-fluorodeoxyglucose (FDG) uptake on positron emission tomography (PET) examination during or after neoadjuvant chemotherapy may predict pathological response in oesophageal cancer. Our aim was to determine whether metabolic response predicts pathological response to a standardised neoadjuvant chemotherapy regimen within a prospective clinical trial. Methods Consecutive patients staged with potentially curable oesophageal cancer who underwent treatment within a non-randomised clinical trial were included. A standardised chemotherapy regimen (two cycles of oxaliplatin and 5- fluorouracil) was used. PET/CT was performed before chemotherapy and repeated 24-28 days after the start of cycle 2. Results Forty-eight subjects were included: Mean age 65 years; 37 male. Using the median percentage reduction in SUVmax (42%) to define metabolic response, pathological response was seen in 71% of metabolic responders (17/24) compared with 33% of non-responders (8/24; P=0.009, sensitivity 68%, specificity 70%). Pathological response was seen in 81% of subjects with a complete metabolic response (13/16) compared with 38% of those with a less than complete response (12/32; P=0.0042, sensitivity 52%, specificity 87%). There was no significant histology-based effect. Conclusions There was a significant association between metabolic response and pathological response; however, accuracy in predicting pathological response was relatively low. Key Points ̇ PET/CT may predict tumour response to chemotherapy in oesophageal cancer. ̇ This was a prospective study using a standardised chemotherapy regimen. ̇ A significant association between PET/CT findings and disease response was found. ̇ However accuracy in predicting pathological response was relatively low. © European Society of Radiology 2012
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