Next-to-Leading Order QCD Analysis of Polarized Deep Inelastic Scattering Data

We present a Next-to-Leading order perturbative QCD analysis of world data on the spin dependent structure functions $g_1^p, g_1^n$, and $g_1^d$, including the new experimental information on the $Q^2$ dependence of $g_1^n$. Careful attention is paid to the experimental and theoretical uncertainties. The data constrain the first moments of the polarized valence quark distributions, but only qualitatively constrain the polarized sea quark and gluon distributions. The NLO results are used to determine the $Q^2$ dependence of the ratio $g_1/F_1$ and evolve the experimental data to a constant $Q^2 = 5 GeV^2$. We determine the first moments of the polarized structure functions of the proton and neutron and find agreement with the Bjorken sum rule.Comment: 21 pages, 4 figures; final version to be published in Phys. Lett. B. References updated. Uses elsart.cls version 1996/04/22, 2e-1.4

Precision determination of the neutron spin structure function g1ng^{n}_{1}

We report on a precision measurement of the neutron spin structure function g1ng^n_1g1n​ using deep inelastic scattering of polarized electrons by polarized ^3He. For the kinematic range 0.014<x<0.7 and 1 (GeV/c)^2< Q^2< 17 (GeV/c)^2, we obtain ∫0.0140.7g1n(x)dx=−0.036±0.004(stat)±0.005(syst)\int^{0.7}_{0.014} g^n_1(x)dx = -0.036 \pm 0.004 (stat) \pm 0.005 (syst)∫0.0140.7​g1n​(x)dx=−0.036±0.004(stat)±0.005(syst) at an average Q2=5(GeV/c)2Q^2=5 (GeV/c)^2Q2=5(GeV/c)2. We find relatively large negative values for g1ng^n_1g1n​ at low xxx. The results call into question the usual Regge theory method for extrapolating to x=0 to find the full neutron integral ∫01g1n(x)dx\int^1_0 g^n_1(x)dx∫01​g1n​(x)dx, needed for testing quark-parton model and QCD sum rules. (arXiv

Next-to-leading order QCD analysis of polarized deep inelastic scattering data

We present a Next-to-Leading order perturbative QCD analysis of world data on the spin dependent structure functions g1p,g1ng_1^p, g_1^ng1p​,g1n​, and g1dg_1^dg1d​, including the new experimental information on the Q2Q^2Q2 dependence of g1ng_1^ng1n​. Careful attention is paid to the experimental and theoretical uncertainties. The data constrain the first moments of the polarized valence quark distributions, but only qualitatively constrain the polarized sea quark and gluon distributions. The NLO results are used to determine the Q2Q^2Q2 dependence of the ratio g1/F1g_1/F_1g1​/F1​ and evolve the experimental data to a constant Q2=5GeV2Q^2 = 5 GeV^2Q2=5GeV2. We determine the first moments of the polarized structure functions of the proton and neutron and find agreement with the Bjorken sum rule

Measurement of the neutron spin structure function g2ng_{2}^{n} and asymmetry a2na_{2}^{n}

We have measured the neutron structure function g2n_{2}^{n}2n​ and the virtual photon-nucleon asymmetry A2n_{2}^{n}2n​ over the kinematic range 0.014≤x≤0.70.014\leq x \leq 0.70.014≤x≤0.7 and 1.0≤Q2≤17.01.0 \leq Q^{2} \leq 17.01.0≤Q2≤17.0 by scattering 48.3 GeV longitudinally polarized electrons from polarized 3^{3}3He. Results for A2n_{2}^{n}2n​ are significantly smaller than the R\sqrt{R}R​ positivity limit over most of the measured range and data for g2n_2^{n}2n​ are generally consistent with the twist-2 Wandzura-Wilczek prediction. Using our measured g2n_{2}^{n}2n​ we obtain results for the twist-3 reduced matrix element d2nd_{2}^{n}d2n​, and the integral ∫\int∫g2n(x)dx_{2}^{n}(x)dx2n​(x)dx in the range 0.014≤x≤1.00.014\leq x \leq 1.00.014≤x≤1.0. Data from this experiment are combined with existing data for g2n_{2}^{n}2n​ to obtain an average for d2nd_{2}^{n}d2n​ and the integral ∫\int∫g2n(x)dx_{2}^{n}(x)dx2n​(x)dx

Review of particle physics

This biennial Review summarizes much of particle physics. Using data from previous editions, plus 2778 new measurements from 645 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics. Among the 108 reviews are many that are new or heavily revised including those on CKM quark-mixing matrix, Vud &amp; Vus, Vcb &amp; Vub, top quark, muon anomalous magnetic moment, extra dimensions, particle detectors, cosmic background radiation, dark matter, cosmological parameters, and big bang cosmology

Review of particle physics

The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 2,143 new measurements from 709 papers, we list, evaluate, and average measured properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Among the 120 reviews are many that are new or heavily revised, including a new review on Machine Learning, and one on Spectroscopy of Light Meson Resonances. The Review is divided into two volumes. Volume 1 includes the Summary Tables and 97 review articles. Volume 2 consists of the Particle Listings and contains also 23 reviews that address specific aspects of the data presented in the Listings. The complete Review (both volumes) is published online on the website of the Particle Data Group (pdg.lbl.gov) and in a journal. Volume 1 is available in print as the PDG Book. A Particle Physics Booklet with the Summary Tables and essential tables, figures, and equations from selected review articles is available in print, as a web version optimized for use on phones, and as an Android app