Measurement of the Splitting Function in &ITpp &ITand Pb-Pb Collisions at root&ITsNN&IT=5.02 TeV

Data from heavy ion collisions suggest that the evolution of a parton shower is modified by interactions with the color charges in the dense partonic medium created in these collisions, but it is not known where in the shower evolution the modifications occur. The momentum ratio of the two leading partons, resolved as subjets, provides information about the parton shower evolution. This substructure observable, known as the splitting function, reflects the process of a parton splitting into two other partons and has been measured for jets with transverse momentum between 140 and 500 GeV, in pp and PbPb collisions at a center-of-mass energy of 5.02 TeV per nucleon pair. In central PbPb collisions, the splitting function indicates a more unbalanced momentum ratio, compared to peripheral PbPb and pp collisions.. The measurements are compared to various predictions from event generators and analytical calculations.Peer reviewe

Problems of transforming labor legislation of Ukraine in connection with the dissemination of latest employment forms

The article explores the dynamic development of atypical forms of employment in the country and its impact on the Ukrainian labor market. The study highlights the need to create institutional and legal regulation of the latest forms of employment. This approach will facilitate the use of the positive aspects of atypical employment (adaptability, flexibility, the possibility of combining work and personal life, and others). The result of the reform of labor legislation in Ukraine should be the introduction of the latest forms of employment, establishing social dialogue, as well as increasing social guarantees for workers of atypical forms of employment to European labor standards.El artículo explora el desarrollo dinámico de formas atípicas de empleo en el país y su impacto en el mercado laboral ucraniano. El estudio destaca la necesidad de crear una regulación institucional y legal de las últimas formas de empleo. Este enfoque facilitará el uso de los aspectos positivos del empleo atípico (adaptabilidad, flexibilidad, la posibilidad de combinar la vida laboral y personal, y otros). El resultado de la reforma de la legislación laboral en Ucrania debería ser la introducción de las últimas formas de empleo, el establecimiento de un diálogo social y el aumento de las garantías sociales para los trabajadores de formas atípicas de empleo según las normas laborales europeas

Pseudorapidity and transverse momentum dependence of flow harmonics in pPb and PbPb collisions

A search has been performed for heavy resonances decaying to ZZ or ZW in 2l2q final states, with two charged leptons (l = e, mu) produced by the decay of a Z boson, and two quarks produced by the decay of a W or Z boson. The analysis is sensitive to resonances with masses in the range from 400 to 4500 GeV. Two categories are defined based on the merged or resolved reconstruction of the hadronically decaying vector boson, optimized for high- and low-mass resonances, respectively. The search is based on data collected during 2016 by the CMS experiment at the LHC in proton-proton collisions with a center-of-mass energy of root s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1). No excess is observed in the data above the standard model background expectation. Upper limits on the production cross section of heavy, narrow spin-1 and spin-2 resonances are derived as a function of the resonance mass, and exclusion limits on the production of W' bosons and bulk graviton particles are calculated in the framework of the heavy vector triplet model and warped extra dimensions, respectively.A search has been performed for heavy resonances decaying to ZZ or ZW in 2l2q final states, with two charged leptons (l = e, mu) produced by the decay of a Z boson, and two quarks produced by the decay of a W or Z boson. The analysis is sensitive to resonances with masses in the range from 400 to 4500 GeV. Two categories are defined based on the merged or resolved reconstruction of the hadronically decaying vector boson, optimized for high- and low-mass resonances, respectively. The search is based on data collected during 2016 by the CMS experiment at the LHC in proton-proton collisions with a center-of-mass energy of root s = 13 TeV, corresponding to an integrated luminosity of 35.9 fb(-1). No excess is observed in the data above the standard model background expectation. Upper limits on the production cross section of heavy, narrow spin-1 and spin-2 resonances are derived as a function of the resonance mass, and exclusion limits on the production of W' bosons and bulk graviton particles are calculated in the framework of the heavy vector triplet model and warped extra dimensions, respectively.Measurements of azimuthal angular correlations are presented for high-multiplicity pPb collisions at root s(NN) = 5.02 TeV and peripheral PbPb collisions at root s(NN) = 2.76 TeV. The data used in this work were collected with the Compact Muon Solenoid (CMS) detector at the European Organization for Nuclear Research (CERN) Large Hadron Collider (LHC). Fourier coefficients as functions of transverse momentum and pseudorapidity are studied using the scalar product method; four-, six-, and eight-particle cumulants; and the Lee-Yang zero technique. The influence of event plane decorrelation is evaluated using the scalar product method and found to account for most of the observed pseudorapidity dependence.Peer reviewe

Measurement of prompt and nonprompt J/ψJ/\psi production in pp and pPb collisions at sNN=\sqrt{s_{NN}} = 5.02 TeV

This paper reports the measurement of $J/\psi$ meson production in proton-proton (pp) and proton-lead (pPb) collisions at a center-of-mass energy per nucleon pair of 5.02 TeV by the CMS experiment at the LHC. The data samples used in the analysis correspond to integrated luminosities of 28 pb$^{-1}$ and 35 nb$^{-1}$ for pp and pPb collisions, respectively. Prompt and nonprompt J/psi mesons, the latter issuing from the decay of B mesons, are measured in their dimuon decay channels. Differential cross sections are measured in the transverse momentum range of 2 < $p_t$ < 30 GeV/c, and center-of-mass rapidity ranges of |y$_{CM}$| < 2.4 (pp) and -2.87 < y$_{CM}$ < 1.93 (pPb). The nuclear modification factor, R$_{pPb}$, is measured as functions of $p_t$ and y$_{CM}$. Small modifications of the $J/\psi$ cross sections are observed in pPb relative to pp collisions. The ratio of $J/\psi$ production cross sections in p-going and Pb-going directions, R$_{FB}$, studied as functions of $p_t$ and y$_{CM}$, shows a significant decrease for increasing transverse energy deposited at large pseudorapidities. These results, which cover a wide kinematic range, provide new insight on the role of cold nuclear matter effects on prompt and nonprompt $J/\psi$ production

Nuclear modification factor of D0^0 mesons in PbPb collisions at sNN=5.02\sqrt{s_\mathrm{NN}} = 5.02 TeV

The transverse momentum ($p_t$) spectrum of prompt D0 mesons and their antiparticles has been measured via the hadronic decay channels $D^0 \to K^- pi^+$ and $\bar{D}^0 \to K^+ pi^-$ in pp and PbPb collisions at a centre-of-mass energy of 5.02 TeV per nucleon pair with the CMS detector at the LHC. The measurement is performed in the $D^0$ meson $p_t$ range of 2-100 GeV and in the rapidity range of $|y| <$ 1. The pp (PbPb) dataset used for this analysis corresponds to an integrated luminosity of 27.4 pb$^{-1}$ (530 $\mu$b$^{-1}$). The measured $D^0$ meson $p_t$ spectrum in pp collisions is well described by perturbative QCD calculations. The nuclear modification factor, comparing $D^0$ meson yields in PbPb and pp collisions, was extracted for both minimum-bias and the 10% most central PbPb interactions. For central events, the $D^0$ meson yield in the PbPb collisions is suppressed by a factor of 5-6 compared to the pp reference in the $p_t$ range of 6-10 GeV. For $D^0$ mesons in the high-$p_t$ range of 60-100 GeV, a significantly smaller suppression is observed. The results are also compared to theoretical calculations

Measurement of transverse momentum relative to dijet systems in PbPb and pp collisions at sNN=2.76\sqrt{s_{NN}} = 2.76 TeV

An analysis of dijet events in PbPb and pp collisions is performed to explore the properties of energy loss by partons traveling in a quark-gluon plasma. Data are collected at a nucleon-nucleon center-of-mass energy of 2.76 TeV at the LHC. The distribution of transverse momentum (pT) surrounding dijet systems is measured by selecting charged particles in different ranges of pT and at different angular cones of pseudorapidity and azimuth. The measurement is performed as a function of centrality of the PbPb collisions, the pT asymmetry of the jets in the dijet pair, and the distance parameter R used in the anti-kt jet clustering algorithm. In events with unbalanced dijets, PbPb collisions show an enhanced multiplicity in the hemisphere of the subleading jet, with the pT imbalance compensated by an excess of low-pT particles at large angles from the jet axes

Challenges to the chiral magnetic wave using charge-dependent azimuthal anisotropies in pPb and PbPb collisions at sNN=\sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = 5.02 TeV

Charge-dependent anisotropy Fourier coefficients ($v_n$) of particle azimuthal distributions are measured in pPb and PbPb collisions at $\sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} =$ 5.02 TeV with the CMS detector at the LHC. The normalized difference in the second-order anisotropy coefficients ($v_2$) between positively and negatively charged particles is found to depend linearly on the observed event charge asymmetry with comparable slopes for both pPb and PbPb collisions over a wide range of charged particle multiplicity. In PbPb, the third-order anisotropy coefficient, $v_3$, shows a similar linear dependence with the same slope as seen for $v_2$. The observed similarities between the $v_2$ slopes for pPb and PbPb, as well as the similar slopes for $v_2$ and $v_3$ in PbPb, are compatible with expectations based on local charge conservation in the decay of clusters or resonances, and constitute a challenge to the hypothesis that the observed charge asymmetry dependence of $v_2$ in heavy ion collisions arises from a chiral magnetic wave

Evidence for Transverse Momentum and Pseudorapidity Dependent Event Plane Fluctuations in PbPb and pPb Collisions

A systematic study of the factorization of long-range azimuthal two-particle correlations into a product of single-particle anisotropies is presented as a function of $p_\mathrm{T}$ and $\eta$ of both particles, and as a function of the particle multiplicity in PbPb and pPb collisions. The data were taken with the CMS detector for PbPb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV and pPb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV, covering a very wide range of multiplicity. Factorization is observed to be broken as a function of both particle $p_\mathrm{T}$ and $\eta$. When measured with particles of different $p_\mathrm{T}$, the magnitude of the factorization breakdown for the second Fourier harmonic reaches 20% for very central PbPb collisions but decreases rapidly as the multiplicity decreases. The data are consistent with viscous hydrodynamic predictions, which suggest that the effect of factorization breaking is mainly sensitive to the initial-state conditions rather than to the transport properties (e.g., shear viscosity) of the medium. The factorization breakdown is also computed with particles of different $\eta$. The effect is found to be weakest for mid-central PbPb events but becomes larger for more central or peripheral PbPb collisions, and also for very high-multiplicity pPb collisions. The $\eta$-dependent factorization data provide new insights to the longitudinal evolution of the medium formed in heavy ion collisions

Measurement of transverse momentum relative to dijet systems in PbPb and pp collisions at sNN=2.76 \sqrt{s_{\mathrm{NN}}}=2.76 TeV

An analysis of dijet events in PbPb and pp collisions is performed to explore the properties of energy loss by partons traveling in a quark-gluon plasma. Data are collected at a nucleon-nucleon center-of-mass energy of 2.76 TeV at the LHC. The distribution of transverse momentum (p$_{T}$) surrounding dijet systems is measured by selecting charged particles in different ranges of p$_{T}$ and at different angular cones of pseudorapidity and azimuth. The measurement is performed as a function of centrality of the PbPb collisions, the p$_{T}$ asymmetry of the jets in the dijet pair, and the distance parameter R used in the anti-k$_{T}$ jet clustering algorithm. In events with unbalanced dijets, PbPb collisions show an enhanced multiplicity in the hemisphere of the subleading jet, with the p$_{T}$ imbalance compensated by an excess of low-p$_{T}$ particles at large angles from the jet axes