The elliptic azimuthal anisotropy coefficient (v2) is measured for charm (D0) and strange (KS0, Λ, Ξ−, and Ω−) hadrons, using a data sample of p+Pb collisions collected by the CMS experiment, at a ...nucleon-nucleon center-of-mass energy of sNN=8.16 TeV. A significant positive v2 signal from long-range azimuthal correlations is observed for all particle species in high-multiplicity p+Pb collisions. The measurement represents the first observation of possible long-range collectivity for open heavy flavor hadrons in small systems. The results suggest that charm quarks have a smaller v2 than the lighter quarks, probably reflecting a weaker collective behavior. This effect is not seen in the larger PbPb collision system at sNN=5.02 TeV, also presented.
Pileup mitigation at CMS in 13 TeV data Chhibra, S.S.; Bilin, B.; Khvastunov, I. ...
Journal of instrumentation,
09/2020, Letnik:
15, Številka:
9
Journal Article
Recenzirano
Odprti dostop
With increasing instantaneous luminosity at the LHC come additional reconstruction challenges. At high luminosity, many collisions occur simultaneously within one proton-proton bunch crossing. The ...isolation of an interesting collision from the additional “pileup” collisions is needed for effective physics performance. In the CMS Collaboration, several techniques capable of mitigating the impact of these pileup collisions have been developed. Such methods include charged-hadron subtraction, pileup jet identification, isospin-based neutral particle “δβ” correction, and, most recently, pileup per particle identification. This paper surveys the performance of these techniques for jet and missing transverse momentum reconstruction, as well as muon isolation. The analysis makes use of data corresponding to 35.9 fb−1 collected with the CMS experiment in 2016 at a center-of-mass energy of 13 TeV. The performance of each algorithm is discussed for up to 70 simultaneous collisions per bunch crossing. Significant improvements are found in the identification of pileup jets, the jet energy, mass, and angular resolution, missing transverse momentum resolution, and muon isolation when using pileup per particle identification.
An inclusive search for the standard model Higgs boson (H) produced with large transverse momentum (p_{T}) and decaying to a bottom quark-antiquark pair (bbover ¯) is performed using a data set of pp ...collisions at sqrts=13 TeV collected with the CMS experiment at the LHC. The data sample corresponds to an integrated luminosity of 35.9 fb^{-1}. A highly Lorentz-boosted Higgs boson decaying to bbover ¯ is reconstructed as a single, large radius jet, and it is identified using jet substructure and dedicated b tagging techniques. The method is validated with Z→bbover ¯ decays. The Z→bbover ¯ process is observed for the first time in the single-jet topology with a local significance of 5.1 standard deviations (5.8 expected). For a Higgs boson mass of 125 GeV, an excess of events above the expected background is observed (expected) with a local significance of 1.5 (0.7) standard deviations. The measured cross section times branching fraction for production via gluon fusion of H→bbover ¯ with reconstructed p_{T}>450 GeV and in the pseudorapidity range -2.5<η<2.5 is 74±48(stat)_{-10}^{+17}(syst) fb, which is consistent within uncertainties with the standard model prediction.
Results on two-particle angular correlations for charged particles emitted in pPb collisions at a nucleon–nucleon center-of-mass energy of 5.02 TeV are presented. The analysis uses two million ...collisions collected with the CMS detector at the LHC. The correlations are studied over a broad range of pseudorapidity, η, and full azimuth, ϕ, as a function of charged particle multiplicity and particle transverse momentum, pT. In high-multiplicity events, a long-range (2<|Δη|<4), near-side (Δϕ≈0) structure emerges in the two-particle Δη–Δϕ correlation functions. This is the first observation of such correlations in proton–nucleus collisions, resembling the ridge-like correlations seen in high-multiplicity pp collisions at s=7 TeV and in AA collisions over a broad range of center-of-mass energies. The correlation strength exhibits a pronounced maximum in the range of pT=1–1.5 GeV/c and an approximately linear increase with charged particle multiplicity for high-multiplicity events. These observations are qualitatively similar to those in pp collisions when selecting the same observed particle multiplicity, while the overall strength of the correlations is significantly larger in pPb collisions.
Machine-learning (ML) techniques are explored to identify and classify hadronic decays of highly Lorentz-boosted W/Z/Higgs bosons and top quarks. Techniques without ML have also been evaluated and ...are included for comparison. The identification performances of a variety of algorithms are characterized in simulated events and directly compared with data. The algorithms are validated using proton-proton collision data at s=13TeV, corresponding to an integrated luminosity of 35.9 fb−1. Systematic uncertainties are assessed by comparing the results obtained using simulation and collision data. The new techniques studied in this paper provide significant performance improvements over non-ML techniques, reducing the background rate by up to an order of magnitude at the same signal efficiency.
The properties of a Higgs boson candidate are measured in the H arrow right ZZ arrow right 4l decay channel, with l = e, mu , using data from pp collisions corresponding to an integrated luminosity ...of 5.1 fb super(-1) at the center-of-mass energy of radicals = 7 TeV and 19.7 fb super(-1) at radicals = 8 TeV, recorded with the CMS detector at the LHC. The new boson is observed as a narrow resonance with a local significance of 6.8 standard deviations, a measured mass of 125.6 + or - 0.4(stat) + or - 0.2(syst) GeV, and a total width < or = 3.4 GeV at the 95% confidence level. The production cross section of the new boson times its branching fraction to four leptons is measured to be (ProQuest: Formulae and/or non-USASCII text omitted) (stat) (ProQuest: Formulae and/or non-USASCII text omitted) (syst) times that predicted by the standard model. Its spin-parity properties are found to be consistent with the expectations for the standard-model Higgs boson. The hypotheses of a pseudoscalar and all tested spin-1 boson hypotheses are excluded at the 99% confidence level or higher. All tested spin-2 boson hypotheses are excluded at the 95% confidence level or higher.
The algorithm developed by the CMS Collaboration to reconstruct and identify τ leptons produced in proton-proton collisions at s=7 and 8 TeV, via their decays to hadrons and a neutrino, has been ...significantly improved. The changes include a revised reconstruction of π0 candidates, and improvements in multivariate discriminants to separate τ leptons from jets and electrons. The algorithm is extended to reconstruct τ leptons in highly Lorentz-boosted pair production, and in the high-level trigger. The performance of the algorithm is studied using proton-proton collisions recorded during 2016 at s=13 TeV, corresponding to an integrated luminosity of 35.9 fb-1. The performance is evaluated in terms of the efficiency for a genuine τ lepton to pass the identification criteria and of the probabilities for jets, electrons, and muons to be misidentified as τ leptons. The results are found to be very close to those expected from Monte Carlo simulation.
The azimuthal anisotropy Fourier coefficients (v_{n}) in 8.16 TeV p+Pb data are extracted via long-range two-particle correlations as a function of the event multiplicity and compared to ...corresponding results in pp and PbPb collisions. Using a four-particle cumulant technique, v_{n} correlations are measured for the first time in pp and p+Pb collisions. The v_{2} and v_{4} coefficients are found to be positively correlated in all collision systems. For high-multiplicity p+Pb collisions, an anticorrelation of v_{2} and v_{3} is observed, with a similar correlation strength as in PbPb data at the same multiplicity. The new correlation results strengthen the case for a common origin of the collectivity seen in p+Pb and PbPb collisions in the measured multiplicity range.
Registro Nacional de la nutrición parenteral domiciliaria del año 2002 Apezetxea, A; Múñoz Jiménez, Agueda; Pedrón Giner, Consuelo ...
Nutrición hospitalaria : organo oficial de la Sociedad Española de Nutrición Parenteral y Enteral,
08/2005, Letnik:
20, Številka:
4
Journal Article
Odprti dostop
Objetivo: Comunicar los resultados del registro sobre Nutrición Parenteral Domiciliaria (NPD) del grupo de Trabajo NADYA-SENPE, correspondientes al año 2002. Material y métodos: Recopilación de los ...datos del registro introducidos por las Unidades responsables de la atención de los pacientes con NPD. Se trata de un registro "on-line" disponible para los usuarios autorizados en la página web del grupo (www.nadya-senpe.com). Se recogen datos epidemiológicos, diagnóstico, vía de acceso, complicaciones, ingresos hospitalarios, grado de incapacidad y evolución a 31 de diciembre de 2002. Resultados: Se recogieron datos de 74 pacientes (56,8% mujeres y 43,2% hombres) pertenecientes a 18 centros hospitalarios. La edad media de los pacientes adultos fue de 49,4 ± 15,5 años; mientras que fue de 2,3 ± 1,1 años para los menores de 14 años (n = 3 pacientes). Las enfermedades que motivaron el uso de NPD fueron la isquemia mesentérica (29,7%), seguida de enfermedad neoplásica (16,2%), enteritis rádica (12,2%), alteraciones de la motilidad (8,1%) y enfermedad de Crohn (5,4%). Los catéteres tunelizados fueron empleados en el 52,7% de los casos, frente al 36,5% de reservorios subcutáneos. La duración media del tratamiento ha sido de 8,7 ± 4,4 meses; el 68,9% de los pacientes habían permanecido con NPD por un periodo superior a los 6 meses, y un 41,9% más de un año. El seguimiento del paciente fue mayoritariamente realizado desde el hospital de referencia (87,8%), y el 12,5% restante por el equipo de atención domiciliaria. En ningún caso el paciente fue seguido por el equipo de atención primaria o por otros especialistas distintos de los que indicaron el soporte nutricional. Se presentaron complicaciones relacionadas con el tratamiento nutritivo en 94 ocasiones. De las complicaciones, las que se presentaron con más frecuencia fueron las infecciosas. Estas complicaciones significaron 1,84 hospitalizaciones por paciente. El número medio de consultas fue de 12,9 consultas por paciente (10,2 rutinarias y 2,7 urgentes). Al finalizar el año, observamos que seguían en activo en el programa el 74,3% de los pacientes; mientras que el 23,6% restante la NPD había sido suspendida. Las principales causas de retirada fueron por éxitus (52,9%) y por pasar a depender de dieta oral (23,5%) o a nutrición enteral (11,8%). En cuanto al grado de incapacidad, el 16,1% estaban confinados en silla o cama y el 17,6% no presentaba ningún grado de incapacidad o sólo una leve incapacidad social Conclusiones: Observamos un mantenimiento en la tasa de prevalencia de NPD en España (1,8 pacientes/millón de habitantes). La causa principal de empleo fue el síndrome de intestino corto secundario a patología vascular, seguido del cáncer. Las complicaciones asociadas al tratamiento nutricional fueron frecuentes, especial-mente las de causa infecciosa.
PDF
