Uzdužna spinska struktura pri COMPASSU

COMPASS is a fixed-target experiment at CERN\u27s Super-Proton-Synchrotron. Part of its physics program is dedicated to the spin structure of the nucleon, which it studies with a 160 GeV polarized muon beam and polarized targets. An overview of its measurements performed with longitudinal target polarization is given. In particular, recent results, concerning the gluon polarization, the separation of the contributions of the individual quark flavors and the test of the Bjorken sum rule, are presented.COMPASS su mjerenja na mirnoj meti pri super protonskom sinkrotronu u CERNu. Dio programa njegovih istraživanja posvećen je spinskoj strukturi nukleona što se proučava sa snopom polariziranih muona energije 160 GeV i polariziranim metama. Izlaže se pregled mjerenja izvedenih s uzdužno polarizaciranim metama. Posebice se izlažu nedavni ishodi za gluonsku polarizaciju, razdjela doprinosa pojedinačnih kvarkovskih okusa i provjera Bjorkenovog pravila suma

Uzdužna spinska struktura pri COMPASSU

COMPASS is a fixed-target experiment at CERN\u27s Super-Proton-Synchrotron. Part of its physics program is dedicated to the spin structure of the nucleon, which it studies with a 160 GeV polarized muon beam and polarized targets. An overview of its measurements performed with longitudinal target polarization is given. In particular, recent results, concerning the gluon polarization, the separation of the contributions of the individual quark flavors and the test of the Bjorken sum rule, are presented.COMPASS su mjerenja na mirnoj meti pri super protonskom sinkrotronu u CERNu. Dio programa njegovih istraživanja posvećen je spinskoj strukturi nukleona što se proučava sa snopom polariziranih muona energije 160 GeV i polariziranim metama. Izlaže se pregled mjerenja izvedenih s uzdužno polarizaciranim metama. Posebice se izlažu nedavni ishodi za gluonsku polarizaciju, razdjela doprinosa pojedinačnih kvarkovskih okusa i provjera Bjorkenovog pravila suma

Mjerenje pionske polarizivosti na COMPASS-U

The electromagnetic structure of pions is probed in π − + (A, Z) → π − + (A, Z) + γ Compton scattering in inverse kinematics (Primakoff reaction) and described by the electric (απ) and the magnetic (βπ) polarizabilities that depend on the rigidity of pion’s internal structure as a composite particle. Values for pion polarizabilities can be extracted from the comparison of the differential cross section for scattering of pointlike pions with the measured cross section. The pion polarizability measurement was performed with a π − beam of 190 GeV. The high beam intensity, the good spectrometer resolution, the high rate capability, the high acceptance and the possibility to use pion and muon beams, unique to the COMPASS experiment, provide the tools to measure precisely the pion polarizabilities in the Primakoff reaction. The preliminary result for pion polarizabilities under the assumption of απ + βπ = 0 is απ = −βπ = (2.5 ± 1.7stat ± 0.6syst) × 10−4 fm3 .Elektromagnetska grad–a piona istražuje se Comptonovim raspršenjem π −+(A, Z) → π − + (A, Z) + γ u obrnutoj kinematici (Primakoffova reakcija) i opisuje se električnom (απ) i magnetskom polarizivošću (βπ). One ovise o krutosti piona kao složene čestice. Vrijednosti pionske polarizivosti izvode se usporedbom diferencijalnih udarnih presjeka za točkaste pione s eksperimentalnima. Mjerenje pionske polarizivosti načinili smo sa snopom π − energije 190 GeV. Snažan snop, dobro razlučivanje spektrometra, velika moć brzog bilježenja i veliko prihvaćanje podataka, te primjena pionskog i mionskog snopa jedinstvene su odlike eksperimenta COMPASS, i to omogućuje točna mjerenja polarizivosti piona Primakoffovom reakcijom. Prethodni ishodi mjerenja za pionske polarizivosti, uz pretpostavku απ + βπ = 0, su απ = −βπ = (2.5 ± 1.7stat ± 0.6syst) × 10−4 fm3

Transverse Momentum Dependent Parton Distribution/Fragmentation Functions at an Electron-Ion Collider

We present a summary of a recent workshop held at Duke University on Partonic Transverse Momentum in Hadrons: Quark Spin-Orbit Correlations and Quark-Gluon Interactions. The transverse momentum dependent parton distribution functions (TMDs), parton-to-hadron fragmentation functions, and multi-parton correlation functions, were discussed extensively at the Duke workshop. In this paper, we summarize first the theoretical issues concerning the study of partonic structure of hadrons at a future electron-ion collider (EIC) with emphasis on the TMDs. We then present simulation results on experimental studies of TMDs through measurements of single spin asymmetries (SSA) from semi-inclusive deep-inelastic scattering (SIDIS) processes with an EIC, and discuss the requirement of the detector for SIDIS measurements. The dynamics of parton correlations in the nucleon is further explored via a study of SSA in D (`D) production at large transverse momenta with the aim of accessing the unexplored tri-gluon correlation functions. The workshop participants identified the SSA measurements in SIDIS as a golden program to study TMDs in both the sea and valence quark regions and to study the role of gluons, with the Sivers asymmetry measurements as examples. Such measurements will lead to major advancement in our understanding of TMDs in the valence quark region, and more importantly also allow for the investigation of TMDs in the sea quark region along with a study of their evolution.Comment: 44 pages 23 figures, summary of Duke EIC workshop on TMDs accepted by EPJ

Hadron Spectroscopy with COMPASS at CERN

The aim of the COMPASS hadron programme is to study the light-quark hadron spectrum, and in particular, to search for evidence of hybrids and glueballs. COMPASS is a fixed-target experiment at the CERN SPS and features a two-stage spectrometer with high momentum resolution, large acceptance, particle identification and calorimetry. A short pilot run in 2004 resulted in the observation of a spin-exotic state with $J^{PC} = 1^{-+}$ consistent with the debated $\pi1(1600)$. In addition, Coulomb production at low momentum transfer data provide a test of Chiral Perturbation Theory. During 2008 and 2009, a world leading data set was collected with hadron beam which is currently being analysed. The large statistics allows for a thorough decomposition of the data into partial waves. The COMPASS hadron data span over a broad range of channels and shed light on several different aspects of QCD.Comment: 4 pages, 5 figure

COMPASS-II Proposal: Questions & Answers

This document presents the answers to the questions on the Compass-II Proposal SPSCP-340 posed by the Referees following the SPSC meeting on 29-30 June, 2010

COMPASS Status Report 2019

The report reviews the activities and the achievements of the Collaboration during the last twelve months. Covered items are the results and ongoing analysis for the data collected in the previous years and the preparations of the 2021 run

The COMPASS experiment

The COMPASS Experiment at the CERN SPS has a broad physics program focused on the study of the spin structure of the nucleon and on hadron spectroscopy. Key measurements for the spin program are the gluon contribution to the spin of the nucleon, semi-inclusive measurements, and the first measurement of the transverse structure function Δ T q(x). Its state-of-the-art apparatus consists of a two-stage large acceptance spectrometer designed for high data rates and equipped with high-resolution tracking, particle identification and electromagnetic and hadronic calorimetry. The first year of physics run (2002) was devoted to the spin programme, using a polarised μ + beam at 160 GeV/c and a polarised [InlineMediaObject not available: see fulltext.] target