Azimuthal anisotropy of charged jet production in root s(NN)=2.76 TeV Pb-Pb collisions

We present measurements of the azimuthal dependence of charged jet production in central and semi-central root s(NN) = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as nu(ch)(2) (jet). Jet finding is performed employing the anti-k(T) algorithm with a resolution parameter R = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero nu(ch)(2) (jet) is observed in semi-central collisions (30-50% centrality) for 20 <p(T)(ch) (jet) <90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the nu(2) of single charged particles at high p(T). Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Forward-central two-particle correlations in p-Pb collisions at root s(NN)=5.02 TeV

Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 2GeV/c. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B. V.Peer reviewe

Event-shape engineering for inclusive spectra and elliptic flow in Pb-Pb collisions at root(NN)-N-S=2.76 TeV

Peer reviewe

Pseudorapidity and transverse-momentum distributions of charged particles in proton-proton collisions at root s=13 TeV

The pseudorapidity (eta) and transverse-momentum (p(T)) distributions of charged particles produced in proton-proton collisions are measured at the centre-of-mass energy root s = 13 TeV. The pseudorapidity distribution in vertical bar eta vertical bar <1.8 is reported for inelastic events and for events with at least one charged particle in vertical bar eta vertical bar <1. The pseudorapidity density of charged particles produced in the pseudorapidity region vertical bar eta vertical bar <0.5 is 5.31 +/- 0.18 and 6.46 +/- 0.19 for the two event classes, respectively. The transverse-momentum distribution of charged particles is measured in the range 0.15 <p(T) <20 GeV/c and vertical bar eta vertical bar <0.8 for events with at least one charged particle in vertical bar eta vertical bar <1. The evolution of the transverse momentum spectra of charged particles is also investigated as a function of event multiplicity. The results are compared with calculations from PYTHIA and EPOS Monte Carlo generators. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Elliptic flow of muons from heavy-flavour hadron decays at forward rapidity in Pb-Pb collisions at root s(NN)=2.76TeV

The elliptic flow, v(2), of muons from heavy-flavour hadron decays at forward rapidity (2.5 <y <4) is measured in Pb-Pb collisions at root s(NN)= 2.76TeVwith the ALICE detector at the LHC. The scalar product, two- and four-particle Q cumulants and Lee-Yang zeros methods are used. The dependence of the v(2) of muons from heavy-flavour hadron decays on the collision centrality, in the range 0-40%, and on transverse momentum, p(T), is studied in the interval 3 <p(T)<10 GeV/c. A positive v(2) is observed with the scalar product and two-particle Q cumulants in semi-central collisions (10-20% and 20-40% centrality classes) for the p(T) interval from 3 to about 5GeV/c with a significance larger than 3 sigma, based on the combination of statistical and systematic uncertainties. The v(2) magnitude tends to decrease towards more central collisions and with increasing pT. It becomes compatible with zero in the interval 6 <p(T)<10 GeV/c. The results are compared to models describing the interaction of heavy quarks and open heavy-flavour hadrons with the high-density medium formed in high-energy heavy-ion collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V.Peer reviewe

Measurement of charged jet production cross sections and nuclear modification in p-Pb collisions at root s(NN)=5.02 TeV

Charged jet production cross sections in p-Pb collisions at root s(NN) = 5.02 TeV measured with the ALICE detector at the LHC are presented. Using the anti-k(T) algorithm, jets have been reconstructed in the central rapidity region from charged particles with resolution parameters R = 0.2 and R = 0.4. The reconstructed jets have been corrected for detector effects and the underlying event background. To calculate the nuclear modification factor, R-pPb, of charged jets in p-Pb collisions, a pp reference was constructed by scaling previously measured charged jet spectra at root s = 7 TeV. In the transverse momentum range 20Peer reviewe

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

Fotoproducción coherente de ρ0\rho^{0} en el LHC

Coherent photoproduction of ½0 mesons in ultra-peripheral Pb-Pb collisions at p sNN = 2.76 TeV is measured for the first time at the LHC and also we show the preliminary results for p-Pb collisions at p sNN = 5.02 TeV. In Pb-Pb collisions the invariant mass and transverse momentum distributions for ½0 production are studied in the ¼+¼¡ decay channel at mid-rapidity. The production cross section in the rapidity range |y|<0.5 is found to be d¾/dy=425§10(est.)+42 ¡50(sist.) mb. Coherent ½0 production is studied with and without requirement of nuclear breakup, and the fractional yields for various breakup scenarios are presented. The results are compared with those from lower energies and with model predictions. In p-Pb collisions the invariant mass and transverse momentum distributions for ½0 production are studied in the ¼+¼¡ decay channel on 7 different rapidity bins corresponding to different energies (Pb-p), also a measurement is made in the rapidity range |y|<0.5 at hW°pi= 82 GeV for both samples (Pb-p and p-Pb). The measured cross section is in agreement with the HERA results. The production cross section in the diferent rapidity bins is found to be: ¾°p = 8.441§0.390(est.); 9.026§0.277(est.); 9.973§0.341(est.); 10.354§0.341(est.); 11.855§0.421(est.); 12.092§0.478(est.); 9.203§0.544(est.) ¹b, at energies hW°pi=59, 69, 78, 86, 95, 105, y 119 GeV, respectively. While at the rapidity range |y|<0.5, where two data sample were analized from two different triggers, the cross section is found to be: ¾°p=11.190§0.369(est.) ¹b (p-Pb), and 10.486§0.163(est.) ¹b (Pb-p).Por primera vez se mide la fotoproducción coherente de mesones ½0 en colisiones ultraperiféricas de Pb-Pb a una energía del centro de masa de p sNN = 2.76 TeV en el colisionador LHC y se dan algunos resultados preliminares de las colisiones p-Pb a p sNN = 5.02 TeV. Para las colisiones Pb-Pb, se estudian las distribuciones de la masa invariante y del momento transversal para la producción de ½0 en el canal de decaimiento ¼+¼¡. Se concluyó que la sección eficaz diferencial de producción en el rango de la rapidez jyj< 0.5 es d¾/dy = 425§10(est.)+42 ¡50(sist.) mb. La producción coherente de ½0 fue estudiado con y sin requirimiento del rompimiento nuclear, y son presentadas las fracciones de las muestras obtenidas de la parte resonante del ajuste para varios escenarios de rompimiento. Los resultados son comparados con los de baja energía y con las predicciones de modelos. En las colisiones de p-Pb se estudian las distribuciones de la masa invariante y del momento transversal para la producción de ½0, estudiado en el canal de decaimiento ¼+¼¡. Para la muestra de las colisiones Pb-p, el análisis se dividió en 7 regiones de la rapidez que corresponden a distintas energías, además se hizo una medición en la región cinemática jyj< 0.5 para ambas muestras (p-Pb y Pb-p) a una energía del centro de masa hW°pi= 82 GeV. Las secciones eficaces determinadas para cada región de la rapidez son consistentes con los resultados obtenidos por HERA. Para la muestra Pb-p se determinó que la sección eficaz para cada región de la rapidez son: ¾°p = 8.441§0.390(est.); 9.026§0.277(est.); 9.973§0.341(est.); 10.354§0.341(est.); 11.855§0.421(est.); 12.092§0.478(est.); 9.203§0.544(est.) ¹b, en las energías hW°pi=59, 69, 78, 86, 95, 105, y 119 GeV, respectivamente. Mientras que en la región de la rapidez |y|<0.5 se analizaron dos muestras de dos triggers diferentes en donde ¾°p=11.190§0.369(est.) ¹b (p-Pb), y 10.486§0.163(est.) ¹b (Pb-p)

El frenado por radiación y la ecuación de G.W. Ford bajo la acción de un campo central

El objetivo de esta tesis es comparar la fuerza de frenado de Ford con las fuerzas de fricción que aparecen en la Mecánica Clásica. por ello se estudia la función de Raleigh en el primer capítulo. En el segundo capítulo analizamos la ecuación de Abraham con el objetivo de entender el estado del arte y sentar las bases para el estudio de la ecuación de Ford. El tercer capítulo está orientado en estudiar la ecuación de Ford en el caso de un campo de fuerza central con dos objetivos primordiales. El primero es analizar la potencia radiada en este caso y el segundo es analizar el tiempo de decaimiento