Search results for "quantum chromodynamics"
showing 10 items of 1027 documents
Measurement of the spin-dependent structure function g1(x) of the deuteron
1993
We report on the first measurement of the spin-dependent structure function g1d of the deuteron in the deep inelastic scattering of polarised muons off polarised deuterons, in the kinematical range 0.006<x<0.6, 1 GeV2<Q2<30 GeV2. The first moment, Γ1d=sh{phonetic}01 g1d dx=0.023±0.020 (stat.) ± 0.015 (syst.), is smaller than the prediction of the Ellis-Jaffe sum rules. Using earlier measurements of g1p, we infer the first moment of the spin-dependent neutron structure function g1n. The difference Γ1p-Γ1n=0.20 ±0.05 (stat.) ± 0.04 (syst.) agrees with the prediction of the Bjorken sum rule, Γ1p-Γ1n=0.191 ±0.002.
Effective charge from lattice QCD
2020
Using lattice configurations for quantum chromodynamics (QCD) generated with three domain-wall fermions at a physical pion mass, we obtain a parameter-free prediction of QCD's renormalisation-group-invariant process-independent effective charge, $\hat\alpha(k^2)$. Owing to the dynamical breaking of scale invariance, evident in the emergence of a gluon mass-scale, this coupling saturates at infrared momenta: $\hat\alpha(0)/\pi=0.97(4)$. Amongst other things: $\hat\alpha(k^2)$ is almost identical to the process-dependent (PD) effective charge defined via the Bjorken sum rule; and also that PD charge which, employed in the one-loop evolution equations, delivers agreement between pion parton di…
Precision measurement of the mass difference between light nuclei and anti-nuclei
2015
The measurement of the mass differences for systems bound by the strong force has reached a very high precision with protons and anti-protons. The extension of such measurement from (anti-)baryons to (anti-)nuclei allows one to probe any difference in the interactions between nucleons and anti-nucleons encoded in the (anti-)nuclei masses. This force is a remnant of the underlying strong interaction among quarks and gluons and can be described by effective theories, but cannot yet be directly derived from quantum chromodynamics. Here we report a measurement of the difference between the ratios of the mass and charge of deuterons and anti-deuterons, and $^{3}{\rm He}$ and $^3\overline{\rm He}…
The Large Hadron–Electron Collider at the HL-LHC
2021
The Large Hadron-Electron Collider (LHeC) is designed to move the field of deep inelastic scattering (DIS) to the energy and intensity frontier of particle physics. Exploiting energy-recovery technology, it collides a novel, intense electron beam with a proton or ion beam from the High-Luminosity Large Hadron Collider (HL-LHC). The accelerator and interaction region are designed for concurrent electron-proton and proton-proton operations. This report represents an update to the LHeC's conceptual design report (CDR), published in 2012. It comprises new results on the parton structure of the proton and heavier nuclei, QCD dynamics, and electroweak and top-quark physics. It is shown how the LH…
QCD resummation effects in forward $J/\psi$ and very backward jet inclusive production at the LHC
2017
We propose and study the inclusive production of a forward $J/\psi$ and a very backward jet at the LHC as an observable to reveal high-energy resummation effects \`a la BFKL. Our different predictions are based on the various existing mechanisms to describe the production of the $J/\psi$, namely, NRQCD singlet and octet contributions, and the color evaporation model.
Summary of Week VII
2018
International audience; Week VII of the INT program 2018 “Probing Nucleons and Nuclei in High Energy Collisions” was dedicated to topics at the interface of the electron-ion collider (EIC), heavy ion and proton-nucleus collisions. The EIC will provide complementary tools to investigate and constrain the initial state in HIC collisions, as well as transport properties of QCD matter which can be extracted from observables that are sensitive to final states interactions such as pt-broadening and energy loss. The contributed talks and discussions covered a variety of physics topics from saturation physics and the origin of multi-particle correlations in HIC to jet quenching and the strong coupl…
Remarks on strange-quark simulations with Wilson fermions
2020
Physical review / D 102(7), 074506 (1-10) (2020). doi:10.1103/PhysRevD.102.074506
Leading isospin breaking effects in the HVP contribution to $a_{\mu}$ and to the running of $\alpha$
2021
The 38th International Symposium on Lattice Field Theory, LATTICE2021, Zoom/Gather@Massachusetts Institute of Technology, USA, 26 Jul 2021 - 30 Jul 2021; Proceedings of Science / International School for Advanced Studies (LATTICE2021), 106 (2021). doi:10.22323/1.396.0106
Electroweak Gauge-Boson and Higgs Production at Small qT: Infrared Safety from the Collinear Anomaly
2012
We study the differential cross sections for electroweak gauge-boson and Higgs production at small and very small transverse-momentum $q_T$. Large logarithms are resummed using soft-collinear effective theory. The collinear anomaly generates a non-perturbative scale $q_*$, which protects the processes from receiving large long-distance hadronic contributions. A numerical comparison of our predictions with data on the transverse-momentum distribution in Z-boson production at the Tevatron and LHC is given.
Diffractive Processes at Next-to-Leading Order in the Dipole Picture
2023
Diffraktiiviset prosessit ovat korkean energian rajalla sensitiivisiä kohdehiukkasen gluonijakaumalle, mistä johtuen niiden avulla voidaan tutkia kohdetta kvanttiväridynamiikan epälineaarisessa alueessa. Näiden epälineaaristen ilmiöiden odotetaan johtavan gluonisaturaatioon, jota voidaan kuvata luontevasti värilasikondensaatiksi kutsutun efektiivisen kenttäteorian avulla. Vaikka saatavilla olevassa kokeellisessa datassa onkin vahvoja viitteitä gluonisaturaatiosta, yksiselitteistä merkkiä saturaatiosta ei ole havaittu. Tämän vuoksi on tärkeää parantaa saturaatiolle sensitiivisten prosessien teoreettista ymmärrystä, jotta pystytään löytämään selkeitä eroja kvanttiväridynamiikan lineaarisen ja…