Centrality evolution of the charged-particle pseudorapidity density over a broad pseudorapidity range in Pb-Pb collisions at root s(NN)=2.76TeV

Peer reviewe

Implementación de un algoritmo genético para la programación de operaciones en configuración fjssp (flexible job shop scheduling problem)

The Flexible Job Shop Scheduling Problem (FJSSP), consists of intelligently assigning customer orders to a set of machines, in such a way as to minimize the whole time of operation. It is been mostly due to the sum of the times of the operations in all the machines, or the time in which the last operation to be processed in a set of production orders is finished, i.e., the makespan. Given the complexity of the problem, an exact optimization method is generally not viable. Various strategies have been proposed, including the use of diverse heuristics. In this report, a genetic algorithm is proposed, resolving instances reported in the literature, and the results are analyzed in terms of efficiency and stability. With the proposed method we can improve the performance on the production floor and we offer ideas for future research of this type of algorithms to resolve the aforementioned problem.El FJSSP, por sus siglas en inglés (Flexible Job Shop Scheduling Problem), consiste en asignar de manera inteligente órdenes de producción a un conjunto de máquinas, de tal modo que se minimice el tiempo de operación. Tal tiempo se refleja mayormente por la suma de los tiempos de operación en todas las máquinas, o bien por el makespan, es decir, el tiempo en que se termina la última operación en ser procesada en un conjunto de órdenes de producción. Dada la complejidad del problema, y la recurrencia con la que se presenta, un método de optimización exacto generalmente no es viable, por ello se han propuesto diversas estrategias, entre ellas el uso de heurísticas. En este reporte de proyecto, se propone un algoritmo genético, resolviendo instancias reportadas en la literatura, discutiendo los resultados analizados en términos de eficiencia y estabilidad. Con el método propuesto se puede mejorar el desempeño en piso de producción y se ofrecen ideas para aplicaciones futuras de este tipo de algoritmos al problema en cuestió

Detección microscópica y molecular de Plasmodium spp. en flamencos (Phoenicopterus ruber) mantenidos bajo cuidado humano en Zoofari, Centro de Conservación, Morelos, México

Aims. The goal of the current study was to determine the prevalence of Plasmodium in the population of Phoenicopterus ruber kept under human care at Zoofari Conservation Center, Morelos, Mexico Settings and Design. Avian malaria vectors belonging to the family Culicidae has been reported at different Mexican States. Malaria infections compromise different host ranges including Phoenicopteriformes (Phoeniconaias minor, Phoenicopterus chilensis). The singled population housed in Zoofari, Conservation Center may harbor subclinical malaria (Plasmodium) infections. Methods and Material. A descriptive cross- sectional study in a singled population of American flamingos (Phoenicopterus ruber). We compared and contrasted two diagnostic techniques, microscopy and polymerase chain reaction (PCR) for avian haemosporidia. In this study 80 blood smears stained in a Romanowsky stain were examined by microscopy, also molecular analysis were conducted, PCR was performed with the use of primers that amplifies parasite mtDNA from species of Haemoproteus, Plasmodium, Leucocytozoon. Results. A total of 80 Phoenicopterus ruber birds were examined for malarial parasites using both microscopy and PCR diagnostic methods, none of them were positives. Conclusions. Our study corresponds to the first of its kind in the region. After implementing two different diagnostic methods for avian malaria, no evidence was obtained of the presence of hemoparasites in the Phoenicopterus ruber population. This type of research allows us to understand the dynamics and identify emerging diseases that can affect animals and man in a certain geographic region.  Objetivos. Establecer la prevalencia de Plasmodium en la población de Phoenicopterus ruber mantenidos bajo cuidado humano en el Centro de Conservación Zoofari, Morelos, México.Configuración y Diseño. Se han presentado reportes de vectores de malaria aviar pertenecientes a la familia Culicidae en estado de Morelos, México. La malaria aviar puede afectar diversas especies de aves incluyendo Phoenicopteriformes (Phoeniconaias minor, Phoenicopterus chilensis) la población de interés podría ser portadora subclínica de Plasmodium. Materiales y Métodos. se realizó un estudio exploratorio en el total de la población de Phoenicopterus ruber. En la investigación se implementaron dos técnicas de diagnóstico de hemoparásitos, la primera corresponde a análisis de frotis sanguíneos teñidos con una tinción rápida tipo Romanowsky los cuales fueron evaluados mediante microscopía óptica convencional y la segunda concierne la realización de la PCR utilizando iniciadores para amplificar ADN mitocondrial de tres especies de hemoparásitos (Haemoproteus, Plasmodium, Leucocytozoon) Análisis Estadístico utilizado. los resultados negativos del estudio no permiten realizar análisis estadístico Resultados. En la evaluación mediante microscopía convencional no se evidenció en ningún frotis sanguíneo, presencia de merogonias o gránulos de hemozoína, obteniendo una totalidad de 80 muestras negativas. Las PCR realizadas bajo las condiciones utilizadas no demostraron amplificación exitosa de ADN parasitario. Conclusiones. Nuestro estudio corresponde al primero de este tipo en la región. Después de implementar dos técnicas diferentes de diagnóstico para malaria aviar no se obtiene evidencia de la presencia de hemoparásitos en la población de Phoenicopterus ruber. Este tipo de investigaciones permite entender la dinámica e identificar enfermedades emergentes que puedan afectar a los animales y al hombre en una determinada región geográfica.

Measurement of the radius dependence of charged-particle jet suppression in Pb–Pb collisions at sNN=5.02\sqrt{s_{\rm NN}} = 5.02 TeV

The ALICE Collaboration reports a new differential measurement of inclusive jet suppression using pp and Pb–Pb collision data at center-of-mass energy per nucleon–nucleon collision $\sqrt{s_{\rm NN}} = 5.02$ TeV. Charged-particle jets are reconstructed using the anti-$k_{\rm T}$ algorithm with resolution parameters $R$ = 0.2, 0.3, 0.4, 0.5, and 0.6 in pp collisions and $R$ = 0.2, 0.4, 0.6 in central (0–10\%), semi-central (30–50\%), and peripheral (60–80\%) Pb–Pb collisions. The analysis uses a novel approach based on machine learning to mitigate the influence of jet background in central heavy-ion collisions, which enables measurements of inclusive jet suppression for jet $p_{\rm T} \ge 40$ GeV/$c$ in central collisions at a resolution parameter of $R$ = 0.6. This is the lowest value of jet $p_{\rm T}$ achieved for inclusive jet measurements at $R$ = 0.6 at the LHC, and is an important step for discriminating different models of jet quenching in the quark-gluon plasma. The transverse momentum spectra, nuclear modification factors, and derived cross section and nuclear modification factor ratios for different jet resolution parameters of charged-particle jets are presented and compared to model predictions. A mild dependence of the nuclear modification factor ratios on collision centrality and resolution parameter is observed. The results are compared to a variety of jet quenching models with varying levels of agreement, demonstrating the effectiveness of this observable to discriminate between models.The ALICE Collaboration reports a new differential measurement of inclusive jet suppression using pp and Pb$-$Pb collision data at center-of-mass energy per nucleon-nucleon collision $\sqrt{s_{\rm NN}} = 5.02$ TeV. Charged-particle jets are reconstructed using the anti-$k_{\rm T}$ algorithm with resolution parameters $R =$ 0.2, 0.3, 0.4, 0.5, and 0.6 in pp collisions and $R =$ 0.2, 0.4, 0.6 in central (0$-$10%), semi-central (30$-$50%), and peripheral (60$-$80%) Pb$-$Pb collisions. The analysis uses a novel approach based on machine learning to mitigate the influence of jet background in central heavy-ion collisions, which enables measurements of inclusive jet suppression for jet $p_{\rm T} \geq 40$ GeV/$c$ in central collisions at a resolution parameter of $R = 0.6$. This is the lowest value of jet $p_{\rm T}$ achieved for inclusive jet measurements at $R=0.6$ at the LHC, and is an important step for discriminating different models of jet quenching in the quark-gluon plasma. The transverse momentum spectra, nuclear modification factors, and derived cross section and nuclear modification factor ratios for different jet resolution parameters of charged-particle jets are presented and compared to model predictions. A mild dependence of the nuclear modification factor ratios on collision centrality and resolution parameter is observed. The results are compared to a variety of jet quenching models with varying levels of agreement, demonstrating the effectiveness of this observable to discriminate between models

Measurement of Λ(1520) production in pp collisions at √s = 7 TeV and p–Pb collisions at √sNN = 5.02 TeV

The production of the Λ(1520) baryonic resonance has been measured at midrapidity in inelastic pp collisions at s√ = 7 TeV and in p-Pb collisions at sNN−−−√ = 5.02 TeV for non-single diffractive events and in multiplicity classes. The resonance is reconstructed through its hadronic decay channel Λ(1520) → pK− and the charge conjugate with the ALICE detector. The integrated yields and mean transverse momenta are calculated from the measured transverse momentum distributions in pp and p-Pb collisions. The mean transverse momenta follow mass ordering as previously observed for other hyperons in the same collision systems. A Blast-Wave function constrained by other light hadrons (π, K, K0S, p, Λ) describes the shape of the Λ(1520) transverse momentum distribution up to 3.5 GeV/c in p-Pb collisions. In the framework of this model, this observation suggests that the Λ(1520) resonance participates in the same collective radial flow as other light hadrons. The ratio of the yield of Λ(1520) to the yield of the ground state particle Λ remains constant as a function of charged-particle multiplicity, suggesting that there is no net effect of the hadronic phase in p-Pb collisions on the Λ(1520) yield

Coherent ψ(2S) photo-production in ultra-peripheral PbPb collisions at √sNN=2.76 TeV

We have performed the first measurement of the coherent ψ(2S) photo-production cross section in ultra-peripheral PbPb collisions at the LHC. This charmonium excited state is reconstructed via the ψ(2S)→l+l− and ψ(2S)→J/ψπ+π− decays, where the J/ψ decays into two leptons. The analysis is based on an event sample corresponding to an integrated luminosity of about 22 μb−1. The cross section for coherent ψ(2S) production in the rapidity interval −0.9<y<0.9 is dσψ(2S)coh/dy=0.83±0.19(stat+syst) mb. The ψ(2S) to J/ψ coherent cross section ratio is 0.34−0.07+0.08(stat+syst). The obtained results are compared to predictions from theoretical models

J/ψ production as a function of charged-particle multiplicity in p–Pb collisions at √sNN = 8.16 TeV

Inclusive J/ψ yields and average transverse momenta in p-Pb collisions at a center-of-mass energy per nucleon pair sNN−−−√ = 8.16 TeV are measured as a function of the charged-particle pseudorapidity density with ALICE. The J/ψ mesons are reconstructed at forward (2.03<ycms<3.53) and backward (−4.46<ycms<−2.96) center-of-mass rapidity in their dimuon decay channel while the charged-particle pseudorapidity density is measured around midrapidity. The J/ψ yields at forward and backward rapidity normalized to their respective average values increase with the normalized charged-particle pseudorapidity density, the former showing a weaker increase than the latter. The normalized average transverse momenta at forward and backward rapidity manifest a steady increase from low to high charged-particle pseudorapidity density with a saturation beyond the average value

Freeze-out radii extracted from three-pion cumulants in pp, p–Pb and Pb–Pb collisions at the LHC

In high-energy collisions, the spatio-temporal size of the particle production region can be measured using the Bose-Einstein correlations of identical bosons at low relative momentum. The source radii are typically extracted using two-pion correlations, and characterize the system at the last stage of interaction, called kinetic freeze-out. In low-multiplicity collisions, unlike in high-multiplicity collisions, two-pion correlations are substantially altered by background correlations, e.g. mini-jets. Such correlations can be suppressed using three-pion cumulant correlations. We present the first measurements of the size of the system at freeze-out extracted from three-pion cumulant correlations in pp, p-Pb and Pb-Pb collisions at the LHC with ALICE. At similar multiplicity, the invariant radii extracted in p-Pb collisions are found to be 5-15% larger than those in pp, while those in Pb-Pb are 35-55% larger than those in p-Pb. Our measurements disfavor models which incorporate substantially stronger collective expansion in p-Pb as compared to pp collisions at similar multiplicity

Underlying-event properties in pp and p–Pb collisions at √sNN = 5.02 TeV

We report about the properties of the underlying event measured with ALICE at the LHC in pp and p−Pb collisions at sNN−−−√=5.02 TeV. The event activity, quantified by charged-particle number and summed-pT densities, is measured as a function of the leading-particle transverse momentum (ptrigT). These quantities are studied in three azimuthal-angle regions relative to the leading particle in the event: toward, away, and transverse. Results are presented for three different pT thresholds (0.15, 0.5, and 1 GeV/c) at mid-pseudorapidity (|η|10 GeV/c, whereas for lower ptrigT values the event activity is slightly higher in p−Pb than in pp collisions. The measurements are compared with predictions from the PYTHIA 8 and EPOS LHC Monte Carlo event generators

Dielectron production at midrapidity at low transverse momentum in peripheral and semi-peripheral Pb–Pb collisions at √sNN = 5.02 TeV

The first measurement of the e+e− pair production at low lepton pair transverse momentum (pT,ee) and low invariant mass (mee) in non-central Pb−Pb collisions at sNN−−−√=5.02 TeV at the LHC is presented. The dielectron production is studied with the ALICE detector at midrapidity (|ηe|<0.8) as a function of invariant mass (0.4≤mee<2.7 GeV/c2) in the 50−70% and 70−90% centrality classes for pT,ee<0.1 GeV/c, and as a function of pT,ee in three mee intervals in the most peripheral Pb−Pb collisions. Below a pT,ee of 0.1 GeV/c, a clear excess of e+e− pairs is found compared to the expectations from known hadronic sources and predictions of thermal radiation from the medium. The mee excess spectra are reproduced, within uncertainties, by different predictions of the photon−photon production of dielectrons, where the photons originate from the extremely strong electromagnetic fields generated by the highly Lorentz-contracted Pb nuclei. Lowest-order quantum electrodynamic (QED) calculations, as well as a model that takes into account the impact-parameter dependence of the average transverse momentum of the photons, also provide a good description of the pT,ee spectra. The measured ⟨p2T,ee⟩−−−−−√ of the excess pT,ee spectrum in peripheral Pb−Pb collisions is found to be comparable to the values observed previously at RHIC in a similar phase-space region