Measurement of Collins asymmetries in inclusive production of pion pairs at BABAR

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) data, where, due to its chiralodd nature, it couples to a new, unknown fragmentation function, called Collins function. Independent information on the Collins function can be obtained in e+e- -> qq annihilation processes, where q = u, d, s. In the cross section formula, the Collins effect introduces a term that depends on the polarization of the quark q (antiquark q), which produces an asymmetry in the azimuthal distribution of the fragmenting products. For unpolarized beams we do not know the spin of the quarks arising from the e+e- annihilation process, and hence we cannot measure the spin effects due to the Collins function analyzing the hadron distributions generated in only one jet, which come from the fragmentation of a single quark. The Collins spin effect can instead be studied in inclusive production of two hadrons detected in opposite jets, produced by the fragmentation of a correlated qq pair: e+e- -> qq -> h1h2X. This correlation results in an observable azimuthal asymmetry distribution of the two hadrons. In this thesis, we present the measurement of the Collins asymmetries in the pions system (h1; h2 = π), using a sample of about 468 fb^(-1) of data collected at a center of mass energy of 10.54 and 10.58 GeV, with the BABAR detector at the e+e- collider PEPII at the SLAC National Accelerator Laboratory of Stanford. The Collins asymmetries are calculated in two different frames called thrust reference frame (RF12), and second hadron momentum frame (RF0), and the final results are shown as a function of the fractional energy and, for the first time in e+e- annihilation, as a function of the transverse momenta of the two pions. These results can be used in combination with Belle, HERMES, and COMPASS data in order to improve the extraction of the Transversity function, and Collins fragmentation function

Light meson decays at BESIII

Due to the high production rate of light mesons in J/? decays, the hight statistics sample of 1.3 billion of J/? events provides an ideal laboratory to investigate the decay dynamics of light mesons, in particular for ? and ?0 mesons. Recently, the BESIII experiment made significant progresses in ? and ?0 decays, including their hadronic and rare decays investigation, which will be discussed in this proceeding

FRAGMENTATION FUNCTIONS AT BABAR

Inclusive hadron production cross section in e+e- annihilation shed light on fundamental questions of hadronization and fragmentation processes. We present measurements of inclusive spectra of charged pions, kaons, and protons (antiprotons) produced in e+e- collisions at the center-of-mass energy of 10.54 GeV, and tests of QCD predictions and hadronization models. We also report the results on the measurement of the azimuthal modulation induced by the Collins effect in inclusive production of charged pion pairs e+e- → ππX, where the two pions are produced in opposite hemispheres. These data allows the determination of the polarized Collins fragmentation functions

Measurement of inclusive production of light charged hadrons at BaBar

Inclusive hadron production cross sections in e+e-collisions shed light on the fundamental fragmentation and hadronization processes. We present measurements of the inclusive spectra of charged pions, kaons and protons in hadronic events at a center-of-mass energy of 10.54 \gev. These results are compared with theoretical predictions and the predictions of three hadronization models. Along with previous measurements at higher energies, they are also used to study the scaling properties of hadron production

Recent results, status and prospects for the BESIII experiment

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Social partners going digital: using digital tools and adapting social dialogue processes

Aquesta publicació s'elabora a partir de les contribucions de cadascú dels membres nacionals que integren la Network of Eufound Correspondent. Pel cas d'Espanya la contribució ha estat realitzada per l'Alejandro GodinoDigital transformation is changing the world of work. This report looks at how social partners - the actors involved in the regulation of employment relationships - are increasingly adopting technological solutions to improve the services that they provide to their members and facilitate collective bargaining processes. Technological tools offer social partners the opportunity to enhance consultation, engage with their members through digitised processes, improve services and increase networking activities, as well as addressing the issue of membership decline. The findings of this report show that the extent to which the social partners use digital technologies varies greatly across the EU Member States, Norway and the United Kingdom. Provisions in collective agreements on several aspects of digitalisation have been identified in about half of the countries. Through these provisions, social partners encourage their members to boost training on digital skills, ensure fair and safe working conditions and take account of data protection and employee monitoring practices. The European social partners' autonomous framework agreement on digitalisation has provided inspiration to national-level organisations, and follow-up actions in this regard have the potential to greatly benefit their members

Social partners going digital: using digital tools and adapting social dialogue processes

La xarxa de corresponsals d'Eurofound ha contribuït a aquest informe i en concret l'Alejandro Godino com així s'expressa a l'Annex 3: Network of Eurofound CorrespondentsDigital transformation is changing the world of work. This report looks at how social partners - the actors involved in the regulation of employment relationships - are increasingly adopting technological solutions to improve the services that they provide to their members and facilitate collective bargaining processes. Technological tools offer social partners the opportunity to enhance consultation, engage with their members through digitised processes, improve services and increase networking activities, as well as addressing the issue of membership decline. The findings of this report show that the extent to which the social partners use digital technologies varies greatly across the EU Member States, Norway and the United Kingdom. Provisions in collective agreements on several aspects of digitalisation have been identified in about half of the countries. Through these provisions, social partners encourage their members to boost training on digital skills, ensure fair and safe working conditions and take account of data protection and employee monitoring practices. The European social partners' autonomous framework agreement on digitalisation has provided inspiration to national-level organisations, and follow-up actions in this regard have the potential to greatly benefit their members

Measurement of the proton form factor by studying e+e−→ppˉe^{+} e^{-}\rightarrow p\bar{p}

Using data samples collected with the BESIII detector at the BEPCII collider, we measure the Born cross section of $e^{+}e^{-}\rightarrow p\bar{p}$ at 12 center-of-mass energies from 2232.4 to 3671.0 MeV. The corresponding effective electromagnetic form factor of the proton is deduced under the assumption that the electric and magnetic form factors are equal $(|G_{E}|= |G_{M}|)$. In addition, the ratio of electric to magnetic form factors, $|G_{E}/G_{M}|$, and $|G_{M}|$ are extracted by fitting the polar angle distribution of the proton for the data samples with larger statistics, namely at $\sqrt{s}=$ 2232.4 and 2400.0 MeV and a combined sample at $\sqrt{s}$ = 3050.0, 3060.0 and 3080.0 MeV, respectively. The measured cross sections are in agreement with recent results from BaBar, improving the overall uncertainty by about 30\%. The $|G_{E}/G_{M}|$ ratios are close to unity and consistent with BaBar results in the same $q^{2}$ region, which indicates the data are consistent with the assumption that $|G_{E}|=|G_{M}|$ within uncertainties.Comment: 13 pages, 24 figure

Confirmation of a charged charmoniumlike state Zc(3885)∓Z_c(3885)^{\mp} in e+e−→π±(DDˉ∗)∓e^+e^-\to\pi^{\pm}(D\bar{D}^*)^\mp with double DD tag

We present a study of the process $e^+e^-\to\pi^{\pm}(D\bar{D}^*)^{\mp}$ using data samples of 1092~pb$^{-1}$ at $\sqrt{s}=4.23$~GeV and 826~pb$^{-1}$ at $\sqrt{s}=4.26$~GeV collected with the BESIII detector at the BEPCII storage ring. With full reconstruction of the $D$ meson pair and the bachelor $\pi^{\pm}$ in the final state, we confirm the existence of the charged structure $Z_c(3885)^{\mp}$ in the $(D\bar{D}^*)^{\mp}$ system in the two isospin processes $e^+e^-\to\pi^+D^0D^{*-}$ and $e^+e^-\to\pi^+D^-D^{*0}$. By performing a simultaneous fit, the statistical significance of $Zc(3885)^{\mp}$ signal is determined to be greater than 10$\sigma$, and its pole mass and width are measured to be $M_{\rm{pole}}$=(3881.7$\pm$1.6(stat.)$\pm$1.6(syst.))~MeV/$c^2$ and $\Gamma_{\rm{pole}}$=(26.6$\pm$2.0(stat.)$\pm$2.1(syst.))~MeV, respectively. The Born cross section times the $(D\bar{D}^*)^{\mp}$ branching fraction ($\sigma(e^+e^-\to\pi^{\pm}Z_{c}(3885)^{\mp}) \times Br(Z_{c}(3885)^{\mp}\to(D\bar{D}^*)^{\mp})$) is measured to be $(141.6\pm7.9(\text{stat.})\pm12.3(\text{syst.}))~\text{pb}$ at $\sqrt{s}=4.23$~GeV and $(108.4\pm6.9(\text{stat.})\pm8.8(\text{syst.}))~\text{pb}$ at $\sqrt{s}=4.26$~GeV. The polar angular distribution of the $\pi^{\pm}$-$Z_c(3885)^{\mp}$ system is consistent with the expectation of a quantum number assignment of $J^P=1^+$ for $Z_c(3885)^{\mp}$

Observation of the isospin-violating decay J/ψ→ϕπ0f0(980)J/\psi \to \phi\pi^{0}f_{0}(980)

Using a sample of 1.31 billion $J/\psi$ events collected with the BESIII detector at the BEPCII collider, the decays $J/\psi \to \phi \pi^{+}\pi^{-}\pi^{0}$ and $J/\psi \to \phi \pi^{0}\pi^{0}\pi^{0}$ are investigated. The isospin violating decay $J/\psi \to \phi \pi^{0} f_{0}(980)$ with $f_{0}(980) \to \pi\pi$, is observed for the first time. The width of the $f_{0}(980)$ obtained from the dipion mass spectrum is found to be much smaller than the world average value. In the $\pi^{0} f_{0}(980)$ mass spectrum, there is evidence of $f_1(1285)$ production. By studying the decay $J/\psi \to \phi\eta'$, the branching fractions of $\eta' \to \pi^{+}\pi^{-}\pi^{0}$ and $\eta' \to \pi^{0}\pi^{0}\pi^{0}$, as well as their ratio, are also measured.Comment: 10 pages, 10 figures, published in Phys. Rev.