Study of Collins Asymmetries at BaBar

Transversity distribution describes the quark transverse polarization inside a transversely polarized nucleon. It is the less known leading-twist piece of the QCD description of the partonic structure of the nucleon. Transversity can be extracted from semi-inclusive deep inelastic scattering (SIDIS) where, however, it couples to a new, unknown fragmentation function, called Collins function. We present the preliminary results of the measurement of the azimuthal asymmetries in the process e^+e^- -> qqbar -> pi pi X, where the two pions are produced in opposite hemispheres. These preliminary results are based on a data sample of about 45 fb^{-1}, collected by the BABAR experiment at a center-of-mass energy of 10.54 GeV, and are compared with the Belle measurements.Comment: 6 pages, 4 postscript figues, contributed to the Proceedings of Transversity 201

Measurement of Collins asymmetries in inclusive production of pion pairs in e^+e^- collisions at BABAR

We present a preliminary measurement of the Collins asymmetries in the inclusive process e^+e^- --> qqbar --> pi pi X at center-of-mass energy near 10.6 GeV. We use a data sample of 468 fb^(-1) collected by the BABAR experiment, and we consider pairs of charged pions produced in opposite jets in hadronic events. We confirm a non-zero Collins effect as observed by previous experiments, and we study the Collins asymmetry as a function of pion fractional energies and transverse momenta, and as a function of the polar angle of the analysis axis.Comment: 7 pages, 7 postscript figues, contributed to the Proceedings of the 36th International Conference on High Energy Physic

u-RANIA: a neutron detector based on \mu -RWELL technology

In the framework of the ATTRACT-uRANIA project, funded by the European Community, we are developing an innovative neutron imaging detector based on micro-Resistive WELL ($\mu$ -RWELL) technology. The $\mu$ -RWELL, based on the resistive detector concept, ensuring an efficient spark quenching mechanism, is a highly reliable device. It is composed by two main elements: a readout-PCB and a cathode. The amplification stage for this device is embedded in the readout board through a resistive layer realized by means of an industrial process with DLC (Diamond-Like Carbon). A thin layer of B$_4$C on the copper surface of the cathode allows the thermal neutrons detection through the release of $^7$Li and $\alpha$ particles in the active volume. This technology has been developed to be an efficient and convenient alternative to the $^3$He shortage. The goal of the project is to prove the feasibility of such a novel neutron detector by developing and testing small planar prototypes with readout boards suitably segmented with strip or pad read out, equipped with existing electronics or readout in current mode. Preliminary results from the test with different prototypes, showing a good agreement with the simulation, will be presented together with construction details of the prototypes and the future steps of the project.Comment: Prepared for the INSTR20 Conference Proceeding for JINS

Measurement of Collins asymmetries in the inclusive production of hadron pairs

Transversity distribution, which describes the quark transverse polarization inside a transversely polarized nucleon, is the last leading-twist missing piece of the QCD description of the partonic structure of the nucleon. Transversity can be extracted from semi-inclusive deep inelastic scattering (SIDIS) where it couples to a new, unknown fragmentation function, called Collins function. The aim of the analysis is a measurement of the azimuthal xasymmetries in e+e− → ππX (inclusive hadron production), based on the full BaBar data sample in order to extract the Collins fragmentation function from the measured asymmetries

Measurement of Collins asymmetries at BaBar

Inclusive hadron production cross sections and angular distributions in e+e− collisions shed light on fundamental questions of hadronization and fragmentation processes. We present measurements of the so-called Collins azimuthal asymmetries in inclusive production of hadron pairs in e+e− → h1h2X annihilation process, where the two hadrons (either kaons or pions) are produced in opposite hemispheres. In particular, this is the first measurement in e+e− annihilation experiment of the KK and Kπ azimuthal asymmetries, which allow to better understand the fragmentation processes and the role of the strage quark, and can be used as a tool to explore the spin content of the nucleon

Measurement of Collins asymmetries in the inclusive production of hadron pairs

Transversity distribution, which describes the quark transverse polarization inside a transversely polarized nucleon, is the last leading-twist missing piece of the QCD description of the partonic structure of the nucleon. Transversity can be extracted from semi-inclusive deep inelastic scattering (SIDIS) where it couples to a new, unknown fragmentation function, called Collins function. The aim of the analysis is a measurement of the azimuthal xasymmetries in e+e− → ππX (inclusive hadron production), based on the full BaBar data sample in order to extract the Collins fragmentation function from the measured asymmetries

The Straw Tube Trackers of the PANDA Experiment

The PANDA experiment will be built at the FAIR facility at Darmstadt (Germany) to perform accurate tests of the strong interaction through bar pp and bar pA annihilation's studies. To track charged particles, two systems consisting of a set of planar, closed-packed, self-supporting straw tube layers are under construction. The PANDA straw tubes will have also unique characteristics in term of material budget and performance. They consist of very thin mylar-aluminized cathodes which are made self-supporting by means of the operation gas-mixture over-pressure. This solution allows to reduce at maximum the weight of the mechanical support frame and hence the detector material budget. The PANDA straw tube central tracker will not only reconstruct charged particle trajectories, but also will help in low momentum (< 1 GeV) particle identification via dE/dx measurements. This is a quite new approach that PANDA tracking group has first tested with detailed Monte Carlo simulations, and then with experimental tests of detector prototypes. This paper addresses the design issues of the PANDA straw tube trackers and the performance obtained in prototype tests.Comment: 7 pages,16 figure

A model to explain angular distributions of J/ψJ/\psi and ψ(2S)\psi(2S) decays into ΛΛ‾\Lambda\overline{\Lambda} and Σ0Σ‾0\Sigma^0\overline{\Sigma}^0

BESIII data show a particular angular distribution for the decay of the $J/\psi$ and $\psi(2S)$ mesons into the hyperons $\Lambda\overline{\Lambda}$ and $\Sigma^0\overline{\Sigma}^0$. More in details the angular distribution of the decay $\psi(2S) \to \Sigma^0\overline{\Sigma}^0$ exhibits an opposite trend with respect to that of the other three channels: $J/\psi \to \Lambda\overline{\Lambda}$, $J/\psi \to \Sigma^0\overline{\Sigma}^0$ and $\psi(2S) \to \Lambda\overline{\Lambda}$. We define a model to explain the origin of this phenomenon.Comment: 6 pages, 7 figures, to be published in Chinese Physics

A Cylindrical GEM Inner Tracker for the BESIII experiment at IHEP

The Beijing Electron Spectrometer III (BESIII) is a multipurpose detector that collects data provided by the collision in the Beijing Electron Positron Collider II (BEPCII), hosted at the Institute of High Energy Physics of Beijing. Since the beginning of its operation, BESIII has collected the world largest sample of J/{\psi} and {\psi}(2s). Due to the increase of the luminosity up to its nominal value of 10^33 cm-2 s-1 and aging effect, the MDC decreases its efficiency in the first layers up to 35% with respect to the value in 2014. Since BESIII has to take data up to 2022 with the chance to continue up to 2027, the Italian collaboration proposed to replace the inner part of the MDC with three independent layers of Cylindrical triple-GEM (CGEM). The CGEM-IT project will deploy several new features and innovation with respect the other current GEM based detector: the {\mu}TPC and analog readout, with time and charge measurements will allow to reach the 130 {\mu}m spatial resolution in 1 T magnetic field requested by the BESIII collaboration. In this proceeding, an update of the status of the project will be presented, with a particular focus on the results with planar and cylindrical prototypes with test beams data. These results are beyond the state of the art for GEM technology in magnetic field