Search results for "hadron"

Measurement of the production of high-pT electrons from heavy-flavour hadron decays in Pb–Pb collisions at √sNN = 2.76 TeV

2017

Electrons from heavy-flavour hadron decays (charm and beauty) were measured with the ALICE detector in Pb–Pb collisions at a centre-of-mass of energy √sNN = 2.76 TeV. The transverse momentum (pT) differential production yields at mid-rapidity were used to calculate the nuclear modification factor RAA in the interval 3 < pT < 18 GeV/c. The RAA shows a strong suppression compared to binary scaling of pp collisions at the same energy (up to a factor of 4) in the 10% most central Pb–Pb collisions. There is a centrality trend of suppression, and a weaker suppression (down to a factor of 2) in semi-peripheral (50–80%) collisions is observed. The suppression of electrons in this broad pT interval …

Production of muons from heavy-flavour hadron decays in p–Pb collisions at √sNN = 5.02 TeV

2017

The production of muons from heavy-flavour hadron decays in p–Pb collisions at √sNN = 5.02 TeV was studied for 2 < pT < 16 GeV/c with the ALICE detector at the CERN LHC. The measurement was performed at forward (p-going direction) and backward (Pb-going direction) rapidity, in the ranges of rapidity in the centre-of-mass system (cms) 2.03 < ycms < 3.53 and −4.46 < ycms < −2.96, respectively. The production cross sections and nuclear modification factors are presented as a function of transverse momentum (pT). At forward rapidity, the nuclear modification factor is compatible with unity while at backward rapidity, in the interval 2.5 < pT < 3.5 GeV/c, it is above unity by more than 2σ. The r…

Spatially dependent parton distribution functions and hard processes in nuclear collisions

2014

First measurement of the Sivers asymmetry for gluons using SIDIS data

2017

The Sivers function describes the correlation between the transverse spin of a nucleon and the transverse motion of its partons. It was extracted from measurements of the azimuthal asymmetry of hadrons produced in semi-inclusive deep inelastic scattering of leptons off transversely polarised nucleon targets, and it turned out to be non-zero for quarks. In this letter the evaluation of the Sivers asymmetry for gluons in the same process is presented. The analysis method is based on a Monte Carlo simulation that includes three hard processes: photon-gluon fusion, QCD Compton scattering and leading-order virtual-photon absorption process. The Sivers asymmetries of the three processes are simul…

Forward light-by-light scattering and electromagnetic correction to hadronic vacuum polarization

2023

Lattice QCD calculations of the hadronic vacuum polarization (HVP) have reached a precision where the electromagnetic (e.m.) correction can no longer be neglected. This correction is both computationally challenging and hard to validate, as it leads to ultraviolet (UV) divergences and to sizeable infrared (IR) effects associated with the massless photon. While we precisely determine the UV divergence using the operator-product expansion, we propose to introduce a separation scale $\Lambda\sim400\;$MeV into the internal photon propagator, whereby the calculation splits into a short-distance part, regulated in the UV by the lattice and in the IR by the scale $\Lambda$, and a UV-finite long-di…

Production of Σ(1385)± and Ξ(1530)0 in proton–proton collisions at √s = 7 TeV

2015

The production of the strange and double-strange baryon resonances ((1385)±, (1530)0) has been measured at mid-rapidity (|y|< 0.5) in proton–proton collisions at √s = 7 TeV with the ALICE detector at the LHC. Transverse momentum spectra for inelastic collisions are compared to QCD-inspired models, which in general underpredict the data. A search for the φ(1860) pentaquark, decaying in the π channel, has been carried out but no evidence is seen. peerReviewed

Measurement of emission-angle anisotropy via long-range angular correlations with high-pT hadrons in d+Au and p+p collisions at √sNN = 200 GeV

2018

We present measurements of two-particle angular correlations between high-transverse-momentum (2 < pT < 11 GeV/c) π0 observed at midrapidity (|η| < 0.35) and particles produced either at forward (3.1 <η< 3.9) or backward (−3.7 <η< −3.1) rapidity in d + Au and p + p collisions at √sNN = 200 GeV. The azimuthal angle correlations for particle pairs with this large rapidity gap in the Au-going direction exhibit a characteristic structure that persists up to pT ≈ 6 GeV/c and which strongly depends on collision centrality, which is a similar characteristic to the hydrodynamical particle flow in A + A collisions. The structure is absent in the d-going direction as well as in p + p collisions, in t…

Interaction of hadrons and tests for the nature of resonances

2016

El propósito de esta Tesis es contribuir al extenso esfuerzo que se ha hecho, en las ultimas décadas, a fin de entender la estructura de las partículas hadrónicas, uno de los temas más importantes en física hadrónica. En los años 50, el desarrollo de los aceleradores de partículas reveló la existencia de una gran cantidad de nuevas resonancias. La proliferación de partículas, poco después, manifestó un patrón, y un esquema de organización para describirlo se hizo necesario. Al principio, se encontró una solución generalizando el concepto de isospín con el modelo de Fermi-Yang de 1959, en el que el protón y el neutrón aparecen como bloques fundamentales y las otras partículas como sus combin…

Jet-like correlations with neutral pion triggers in pp and central Pb–Pb collisions at 2.76 TeV

2016

Physics letters / B B763, 238 - 250 (2016). doi:10.1016/j.physletb.2016.10.048

Features of W production in p-p, p-Pb and Pb-Pb collisions

2017

We consider the production of inclusive W bosons in variety of high-energy hadronic collisions: p--p, p--$\overline{\rm p}$, p--Pb, and Pb--Pb. In particular, we focus on the resulting distributions of charged leptons from W decay that can be measured with relatively low backgrounds. The leading-order expressions within the collinearly factorized QCD indicate that the center-of-mass energy dependence at forward/backward rapidities should be well approximated by a simple power law. The scaling exponent is related to the small-$x$ behaviour of the quark distributions, which is largely driven by the parton evolution. An interesting consequence is the simple scaling law for the lepton charge as…