3,556 research outputs found
Soft-gluon resolution scale in QCD evolution equations
QCD evolution equations can be recast in terms of parton branching processes.
We present a new numerical solution of the equations. We show that this
parton-branching solution can be applied to analyze infrared contributions to
evolution, order-by-order in the strong coupling , as a function of
the soft-gluon resolution scale parameter. We examine the cases of
transverse-momentum ordering and angular ordering. We illustrate that this
approach can be used to treat distributions which depend both on longitudinal
and on transverse momenta.Comment: Latex, 8 pages, 4 figure
Collinear and TMD Quark and Gluon Densities from Parton Branching Solution of QCD Evolution Equations
We study parton-branching solutions of QCD evolution equations and present a
method to construct both collinear and transverse momentum dependent (TMD)
parton densities from this approach. We work with next-to-leading-order (NLO)
accuracy in the strong coupling. Using the unitarity picture in terms of
resolvable and non-resolvable branchings, we analyze the role of the soft-gluon
resolution scale in the evolution equations. For longitudinal momentum
distributions, we find agreement of our numerical calculations with existing
evolution programs at the level of better than 1 percent over a range of five
orders of magnitude both in evolution scale and in longitudinal momentum
fraction. We make predictions for the evolution of transverse momentum
distributions. We perform fits to the high-precision deep inelastic scattering
(DIS) structure function measurements, and we present a set of NLO TMD
distributions based on the parton branching approach.Comment: 27 pages, 8 figure
Ultrashort pulse characterization by spectral shearing interferometry with spatially chirped ancillae
We report a new version of spectral phase interferometry for direct electric
field reconstruction (SPIDER), which enables consistency checking through the
simultaneous acquisition of multiple shears and offers a simple and precise
calibration method. By mixing the test pulse with two spatially chirped ancilla
fields we generate a single-shot interferogram which contains multiple shears,
the spectral amplitude of the test pulse, and the reference phase, which is
accurate for broadband pulses. All calibration parameters - shear,
upconversion-frequency and reference phase position - can be accurately
obtained from a single calibration trace.Comment: 11 pages, 7 figure
RETRATO EXTERIOR DE SOLDADOS [Material gráfico]
ESCUELA TALLER DE MODERNIZACIÓN DE ARCHIVOS Y BIBLIOTECAS DEL AYUNTAMIENTO DE VALSEQUILLOCopia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 201
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Search for MSSM Higgs bosons decaying to μ+μ-in proton-proton collisions at √s=13TeV
A search is performed for neutral non-standard-model Higgs bosons decaying to two muons in the context of the minimal supersymmetric standard model (MSSM). Proton-proton collision data recorded by the CMS experiment at the CERN Large Hadron Collider at a center-of-mass energy of 13TeVwere used, corresponding to an integrated luminosity of 35.9fb-1. The search is sensitive to neutral Higgs bosons produced via the gluon fusion process or in association with a bbquark pair. No significant deviations from the standard model expectation are observed. Upper limits at 95% confidence level are set in the context of the mmod+hand phenomenological MSSM scenarios on the parameter tanβas a function of the mass of the pseudoscalar Aboson, in the range from 130 to 600GeV. The results are also used to set a model-independent limit on the product of the branching fraction for the decay into a muon pair and the cross section for the production of a scalar neutral boson, either via gluon fusion, or in association with bquarks, in the mass range from 130 to 1000GeV
Search for new neutral Higgs bosons through the H → ZA→ ℓ+ℓ−b b ¯ process in pp collisions at √s = 13 TeV
This paper reports on a search for an extension to the scalar sector of the standard model, where a new CP-even (odd) boson decays to a Z boson and a lighter CP-odd (even) boson, and the latter further decays to a b quark pair. The Z boson is reconstructed via its decays to electron or muon pairs. The analysed data were recorded in proton-proton collisions at a center-of-mass energy s = 13 TeV, collected by the CMS experiment at the LHC during 2016, corresponding to an integrated luminosity of 35.9 fb−1. Data and predictions from the standard model are in agreement within the uncertainties. Upper limits at 95% confidence level are set on the production cross section times branching fraction, with masses of the new bosons up to 1000 GeV. The results are interpreted in the context of the two-Higgs-doublet model. [Figure not available: see fulltext.]
TMDlib2 and TMDplotter: a platform for 3D hadron structure studies
A common library, TMDlib2, for Transverse-Momentum-Dependent distributions (TMDs) and unintegrated parton distributions (uPDFs) is described, which allows for easy access of commonly used TMDs and uPDFs, providing a three-dimensional (3D) picture of the partonic structure of hadrons. The tool TMDplotter allows for web-based plotting of distributions implemented in TMDlib2, together with collinear pdfs as available in LHAPDF
Study of the B +→ J / ψ Λ ¯ p decay in proton-proton collisions at √s = 8 TeV
A study of the B +→ J / ψ Λ ¯ p decay using proton-proton collision data collected at s = 8 TeV by the CMS experiment at the LHC, corresponding to an integrated luminosity of 19.6 fb−1, is presented. The ratio of branching fractions B(B+→J/ψΛ¯p)/B(B+→J/ψK∗(892)+) is measured to be (1.054 ± 0.057(stat) ± 0.035(syst) ± 0.011(B))%, where the last uncertainty reflects the uncertainties in the world-average branching fractions of Λ ¯ and K*(892) + decays to reconstructed final states. The invariant mass distributions of the J / ψ Λ ¯ , J/ψp, and Λ ¯ p systems produced in the B +→ J / ψ Λ¯ p decay are investigated and found to be inconsistent with the pure phase space hypothesis. The analysis is extended by using a model-independent angular amplitude analysis, which shows that the observed invariant mass distributions are consistent with the contributions from excited kaons decaying to the Λ ¯ p system. [Figure not available: see fulltext.
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