E.R. Bielert
A5013751798- Particle physics theoretical and experimental studies
- High-Energy Particle Collisions Research
- Quantum Chromodynamics and Particle Interactions
- Superconducting Materials and Applications
- Spacecraft and Cryogenic Technologies
- Particle Accelerators and Free-Electron Lasers
- Particle accelerators and beam dynamics
- Particle Detector Development and Performance
- Thermal Analysis in Power Transmission
- Dark Matter and Cosmic Phenomena
- Computational Physics and Python Applications
- Optimization and Search Problems
- Neutrino Physics Research
- Magnetic Properties and Applications
- Theoretical and Computational Physics
- Radiation Detection and Scintillator Technologies
- Medical Imaging Techniques and Applications
- Advanced Graph Theory Research
- Cold Atom Physics and Bose-Einstein Condensates
- Atomic and Subatomic Physics Research
- Superconductivity in MgB2 and Alloys
- Advanced NMR Techniques and Applications
- Graph Labeling and Dimension Problems
- Geothermal Energy Systems and Applications
European Organization for Nuclear Research
2011-2020
University of Aveiro
2017-2019
University of Illinois Urbana-Champaign
2017-2019
University of Twente
2011-2015
The first measurement of transverse-spin-dependent azimuthal asymmetries in the pion-induced Drell-Yan (DY) process is reported. We use CERN SPS 190 GeV/c π^{-} beam and a transversely polarized ammonia target. Three giving access to different transverse-momentum-dependent (TMD) parton distribution functions (PDFs) are extracted using dimuon events with invariant mass between 4.3 GeV/c^{2} 8.5 GeV/c^{2}. Within experimental uncertainties, observed sign Sivers asymmetry found be consistent...
New results for the double spin asymmetry A1p and proton longitudinal structure function g1p are presented. They were obtained by COMPASS Collaboration using polarised 200 GeV muons scattered off a longitudinally NH3 target. The data collected in 2011 complement those recorded 2007 at 160 GeV, particular lower values of x. improve statistical precision g1p(x) about factor two region x≲0.02. A next-to-leading order QCD fit to g1 world is performed. It leads new determination quark...
Measurements of the Collins and Sivers asymmetries for charged pions neutral kaons produced in semi-inclusive deep-inelastic scattering high energy muons off transversely polarised protons are presented. The results were obtained using all available COMPASS proton data, which taken years 2007 2010. exhibit valence region a non-zero signal there hints also kaons. found to be positive compatible with zero otherwise.
The main characteristics of the COMPASS experimental setup for physics with hadron beams are described. This was designed to perform exclusive measurements processes several charged and/or neutral particles in final state. Making use a large part apparatus that previously built spin structure studies muon beam, it also features new target system as well or upgraded detectors. is able operate at high incident flux available CERN. It characterised by angular and momentum coverages, nearly flat...
The COMPASS collaboration at CERN has measured diffractive dissociation of 190 GeV/$c$ pions into the $\pi^-\pi^-\pi^+$ final state using a stationary hydrogen target. A partial-wave analysis (PWA) was performed in bins $3\pi$ mass and four-momentum transfer isobar model so far largest PWA consisting 88 waves. narrow $J^{PC} = 1^{++}$ signal is observed $f_0(980)\,\pi$ channel. We present resonance-model study subset spin-density matrix selecting states with 2^{++}$ $4^{++}$ decaying...
We have performed the most comprehensive resonance-model fit of $\pi^-\pi^-\pi^+$ states using results our previously published partial-wave analysis (PWA) a large data set diffractive-dissociation events from reaction $\pi^- + p \to \pi^-\pi^-\pi^+ p_\text{recoil}$ with 190 GeV/$c$ pion beam. The PWA results, which were obtained in 100 bins three-pion mass, $0.5 < m_{3\pi} 2.5$ GeV/$c^2$, and simultaneously 11 reduced four-momentum transfer squared, $0.1 t' 1.0$ $($GeV$/c)^2$, are subjected...
Exclusive production of $\eta\pi^-$ and $\eta'\pi^-$ has been studied with a $191\,\textrm{GeV}/c$ $\pi^-$ beam impinging on hydrogen target at COMPASS (CERN). Partial-wave analyses reveal different odd/even angular momentum ($L$) characteristics in the inspected invariant mass range up to $3\,\textrm{GeV}/c^2$. A striking similarity between two systems is observed for $L=2,4,6$ intensities (scaled by kinematical factors) relative phases. The known resonances $a_2(1320)$ $a_4(2040)$ are line...
A semi-inclusive measurement of charged hadron multiplicities in deep inelastic muon scattering off an isoscalar target was performed using data collected by the COMPASS Collaboration at CERN. The following kinematic domain is covered data: photon virtuality ${Q}^{2}>1\text{ }\text{ }(\mathrm{GeV}/c{)}^{2}$, invariant mass hadronic system $W>5\text{ }\mathrm{GeV}/{c}^{2}$, Bjorken scaling variable range $0.003<x<0.4$, fraction virtual energy carried $0.2<z<0.8$, and square transverse...
Proton transverse-spin azimuthal asymmetries are extracted from the COMPASS 2010 semi-inclusive hadron measurements in deep inelastic muon-nucleon scattering those four regions of photon virtuality $Q^2$, which correspond to di-muon mass $\sqrt{Q^2}$ used ongoing analysis Drell-Yan measurements. This allows for a future direct comparison nucleon transverse-momentum-dependent parton distribution functions these two alternative Various two-dimensional kinematic dependences presented induced by...
The COMPASS collaboration has collected the currently largest data set on diffractively produced ${\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ final states using a negative pion beam of $190\text{ }\text{ }\mathrm{GeV}/c$ momentum impinging stationary proton target. This allows for systematic partial-wave analysis in 100 bins three-pion mass, $0.5<{m}_{3\ensuremath{\pi}}<2.5\text{ }\mathrm{GeV}/{c}^{2}$, and 11 reduced four-momentum...
Final results are presented from the inclusive measurement of deep-inelastic polarised-muon scattering on longitudinally polarised deuterons using a 6LiD target. The data were taken at 160 GeV beam energy and shown for kinematic range 1(GeV/c)2<Q2<100(GeV/c)2 in photon virtuality, 0.004<x<0.7 Bjorken scaling variable W>4GeV/c2 mass hadronic final state. deuteron double-spin asymmetry A1d longitudinal-spin structure function g1d bins x Q2. Towards lowest accessible values x, decreases becomes...
Multiplicities of charged pions and unidentified hadrons produced in deep-inelastic scattering were measured bins the Bjorken scaling variable $x$, relative virtual-photon energy $y$ hadron $z$. Data obtained by COMPASS Collaboration using a 160 GeV muon beam an isoscalar target ($^6$LiD). They cover kinematic domain photon virtuality $Q^2$ > 1(GeV/c$)^2$, $0.004 < x 0.4$, $0.2 z 0.85$ $0.1 y 0.7$. In addition, leading-order pQCD analysis was performed pion multiplicity results to extract...
We report on the first measurement of exclusive single-photon muoproduction proton by COMPASS using 160 GeV/c polarised μ+ and μ− beams CERN SPS impinging a liquid hydrogen target. determine dependence average measured cross sections for deeply virtual Compton scattering squared four-momentum transfer t from initial to final proton. The slope B t-dependence is fitted with single exponential function, which yields B=(4.3±0.6stat|sys−0.3+0.1)(GeV/c)−2. This result can be converted into...
Precise measurements of charged-kaon multiplicities in deep inelastic scattering were performed. The results are presented three-dimensional bins the Bjorken scaling variable x, relative virtual-photon energy y, and fraction z carried by produced hadron. data obtained COMPASS Collaboration 160 GeV muons off an isoscalar 6LiD target. They cover kinematic domain 1(GeV/c)2<Q2<60(GeV/c)2 photon virtuality, 0.004<x<0.4, 0.1<y<0.7, 0.20<z<0.85, W>5 GeV/c2 invariant mass hadronic system. from sum...
A search for the exclusive production of Zc±(3900) hadron by virtual photons has been performed in channel Zc±(3900)→J/ψπ±. The data cover range from 7 GeV to 19 centre-of-mass energy photon–nucleon system. full set COMPASS collected with a muon beam between 2002 and 2011 used. An upper limit ratio BR(Zc±(3900)→J/ψπ±)×σγN→Zc±(3900)N/σγN→J/ψN 3.7×10−3 established at confidence level 90%.
The Sivers function describes the correlation between transverse spin of a nucleon and motion its partons. For quarks, it was studied in previous measurements azimuthal asymmetry hadrons produced semi-inclusive deep inelastic scattering leptons off transversely polarised targets, found to be non-zero. In this letter evaluation for gluons is presented. contribution photon–gluon fusion subprocess enhanced by requiring two high transverse-momentum hadrons. analysis method based on Monte Carlo...
We have searched for exclusive production of exotic charmonia in the reaction $\mu^+~N \rightarrow \mu^+ (J\!/\!\psi\pi^+\pi^-)\pi^{\pm}~N'$ using COMPASS data collected with incoming muons 160 GeV/$c$ and 200 momentum. In $J\!/\!\psi\pi^+\pi^-$ mass distribution we observe a signal statistical significance 4.1 $\sigma$. Its width are consistent those $X(3872)$. The shape $\pi^+\pi^-$ from observed decay into shows disagreement previous observations may be interpreted as possible evidence...
We present a precise measurement of the proton longitudinal double-spin asymmetry $A_1^{\rm p}$ and spin-dependent structure function $g_1^{\rm at photon virtualities $0.006~({\rm GeV}/c)^2
The transverse spin asymmetries measured in semi-inclusive leptoproduction of hadrons, when weighted with the hadron momentum $P_T$, allow for extraction important transverse-momentum-dependent distribution functions. In particular, Sivers provide direct information on function, which is a leading-twist that arises from correlation between an unpolarised quark transversely polarised nucleon and nucleon. Using high-statistics data collected by COMPASS Collaboration 2010 proton target, we have...
Single hadron azimuthal asymmetries of positive and negative hadrons produced in muon semi-inclusive deep inelastic scattering off longitudinally polarised deuterons are determined using the 2006 COMPASS data also combined all deuteron data. For each charge, dependence asymmetry on angle $\phi$ is obtained by means a five-parameter fitting function that besides $\phi$-independent term includes four modulations predicted theory: $\sin\phi$, $\sin 2 \phi$, 3\phi$ $\cos\phi$. The amplitudes...
We present a new amplitude analysis of the ηπ D-wave in reaction π−p→ηπ−p measured by COMPASS. Employing an analytical model based on principles relativistic S-matrix, we find two resonances that can be identified with a2(1320) and excited a2′(1700), perform comprehensive their pole positions. For mass width a2 M=(1307±1±6) MeV Γ=(112±1±8) MeV, for state a2′ obtain M=(1720±10±60) Γ=(280±10±70) respectively.
The design and construction of a wide-aperture, superconducting quadrupole magnet for the LHC insertion region is part study towards luminosity upgrade at CERN. engineering components tooling, procurement, work presented in this paper includes innovative features such as more porous cable insulation, new collar structure allowing horizontal assembly with hydraulic collaring press, tuning shims adjustment field quality, fishbone like ground-plane an improved quench-heater design. Rapid...
Using a novel analysis technique, the gluon polarisation in nucleon is re-evaluated using longitudinal double-spin asymmetry measured cross section of semi-inclusive single-hadron muoproduction with photon virtuality $$Q^2>1~(\mathrm{GeV}/c)^2$$ . The data were obtained by COMPASS experiment at CERN 160 GeV/c polarised muon beam impinging on $$^6$$ LiD target. By analysing full range hadron transverse momentum $$p_\mathrm{T}$$ , different -dependences underlying processes are separated...
In the fragmentation of a transversely polarized quark several left–right asymmetries are possible for hadrons in jet. When only one unpolarized hadron is selected, it exhibits an azimuthal modulation known as Collins effect. pair oppositely charged observed, three can be considered, di-hadron asymmetry and two single asymmetries. lepton deep inelastic scattering on nucleons all these coupled with transversity distribution. From high statistics COMPASS data hadron-pair production we have...