A5034338982- Particle physics theoretical and experimental studies
- Quantum Chromodynamics and Particle Interactions
- High-Energy Particle Collisions Research
- Particle Detector Development and Performance
- Superconducting Materials and Applications
- Muon and positron interactions and applications
- Particle Accelerators and Free-Electron Lasers
- Advanced NMR Techniques and Applications
- Atomic and Subatomic Physics Research
- Nuclear physics research studies
- Photocathodes and Microchannel Plates
- Crystallography and Radiation Phenomena
- Electron and X-Ray Spectroscopy Techniques
- Neutrino Physics Research
- Radiation Therapy and Dosimetry
- Spectroscopy and Quantum Chemical Studies
- Quantum and electron transport phenomena
- Solid State Laser Technologies
- Advanced Data Storage Technologies
- Particle accelerators and beam dynamics
- Geophysics and Gravity Measurements
- NMR spectroscopy and applications
- Laser Design and Applications
- Random Matrices and Applications
- Luminescence Properties of Advanced Materials
Johannes Gutenberg University Mainz
2010-2024
University of Aveiro
2018-2023
A. Alikhanyan National Laboratory
2023
European Organization for Nuclear Research
2018-2019
Universität Hamburg
2012
University Medical Center Hamburg-Eppendorf
2012
Campbell Collaboration
2011
University of Trieste
2009
University of Burdwan
2009
Max Planck Institute for Nuclear Physics
2008
We present the final results of spin asymmetries A1 and structure functions g1 proton deuteron in kinematic range 0.0008<x<0.7 0.2<Q2<100GeV2. For determination A1, addition to usual method which employs inclusive scattering events includes a large radiative background at low x, we use new minimizes by selecting with least one hadron as well muon state. find that this gives smaller errors for x<0.02, so it is combined provide optimal set results.Received 18 May...
We report on a measurement of the parity-violating asymmetry in scattering longitudinally polarized electrons unpolarized protons at Q2 0.230 (GeV/c)(2) and angle theta (e) = 30 degrees - 40 degrees. Using large acceptance fast PbF2 calorimeter with solid delta omega 0.62 sr, A4 experiment is first parity violation to count individual events. The measured A(phys)=(-5.44+/-0.54(stat)+/-0.26(sys))x10(-6). standard model expectation assuming no strangeness contributions vector form factors A(0)...
We present a new measurement of the spin-dependent structure function g1d deuteron in deep inelastic scattering 190 GeV polarised muons on deuterons, kinematic range 0.003 < x 0.7 and 1 GeV2 Q2 60 GeV2. This is found to be negative at small x. The first moment Γ1d=∫01g1ddx evaluated Q02 = 10 0.034 ± 0.009 (stat.) 0.006 (syst.). value below Ellis-Jaffe sum rule prediction by three standard deviations. Using our earlier determination Γ1p, we obtain Γ1p − Γ1n 0.199 0.038 which agrees with Bjorken rule.
We present a measurement of semi-inclusive spin asymmetries for positively and negatively charged hadrons from deep inelastic scattering polarised muons on protons deuterons in the range 0.003<x<0.7 Q2>1 GeV2. Compared to our previous publication this subject, with new data statistical errors have been reduced by nearly factor two. From these inclusive we determine quark distributions valence quarks non-strange sea at Q2=10 The u distribution, Δuv(x), is positive polarisation increases x. d...
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 present a next-to-leading order QCD analysis of the presently available data on spin structure function g1 including final from Spin Muon Collaboration. results for first moments proton, deuteron, and neutron functions, determine singlet nonsinglet parton distributions in two factorization schemes. also test Bjorken sum rule find agreement with theoretical prediction at level 10%.Received 18 May 1998DOI:https://doi.org/10.1103/PhysRevD.58.112002©1998 American Physical Society
We present a measurement of the longitudinal spin cross section asymmetry for deep-inelastic muon-nucleon interactions with two high transverse momentum hadrons in final state. Two methods event classification are used to increase contribution photon-gluon fusion process above 30%. The most effective one, based on neural network approach, provides asymmetries Al→NlhhXp=0.030±0.057(stat)±0.010(syst) and Al→NlhhXd=0.070±0.076(stat)±0.010(syst). From these values we derive an averaged gluon...
We report on a measurement of the asymmetry in scattering transversely polarized electrons off unpolarized protons, A( perpendicular), at two Q2 values 0.106 and 0.230 (GeV/c)(2) angle 30 degrees <theta(e)<40 . The measured transverse asymmetries are perpendicular)(Q(2)=0.106 (GeV/c)(2))=(-8.59+/-0.89(stat)+/-0.75(syst))x10(-6) perpendicular)(Q(2)=0.230 (GeV/c)(2))=(-8.52+/-2.31(stat)+/-0.87(syst))x10(-6). first errors denote statistical error second systematic uncertainties. From comparison...
The semi-inclusive difference asymmetry A^{h^{+}-h^{-}} for hadrons of opposite charge has been measured by the COMPASS experiment at CERN. data were collected in years 2002-2004 using a 160 GeV polarised muon beam scattered off large ^6LiD target and cover range 0.006 < x 0.7 1 Q^2 100 (GeV/c)^2. In leading order QCD (LO) A_d^{h^{+}-h^{-}} measures valence quark polarisation provides an evaluation first moment Delta u_v + d_v which is found to be equal 0.40 +- 0.07 (stat.) 0.05 (syst.)...
The COMPASS experiment at the CERN SPS has studied diffractive dissociation of negative pions into π−π−π+ final state using a 190 GeV/c pion beam hitting lead target. A partial wave analysis been performed on sample 420 000 events taken values squared 4-momentum transfer t′ between 0.1 and 1 GeV2/c2. well-known resonances a1(1260), a2(1320), π2(1670) are clearly observed. In addition, data show significant natural-parity exchange production resonance with spin-exotic quantum numbers JPC=1−+...
We present a LO evaluation of helicity densities valence, Δuv+Δdv, non-strange sea, Δu¯+Δd¯, and strange quarks, Δs (assumed to be equal Δs¯). They have been obtained from the inclusive asymmetry A1,d semi-inclusive asymmetries A1,dπ+, A1,dπ−, A1,dK+, A1,dK− measured in polarised deep inelastic muon–deuteron scattering. The full deuteron statistics COMPASS (years 2002–2004 2006) has used. data cover range Q2>1(GeV/c)2 0.004<x<0.3. Both are found good agreement with previous measurements....
We present the results of spin asymmetries ${A}_{1}$ proton and deuteron in kinematic region extending down to $x=6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ ${Q}^{2}=0.01{\mathrm{GeV}}^{2}.$ The data were taken with a dedicated low x trigger, which required hadron detection addition scattered muon, so as reduce background at x. complement our previous measurements two sets are consistent overlap region. No significant effects found newly explored
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...
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 gluon polarisation in the nucleon has been determined by detecting charm production via D0 meson decay to charged K and π polarised muon scattering off a longitudinally deuteron target. data were taken COMPASS Collaboration at CERN between 2002 2006 correspond an integrated luminosity of 2.8 fb−1. dominant underlying process is photon–gluon fusion cc¯ pair. A leading order QCD approach gives average 〈Δg/g〉x=−0.49±0.27(stat)±0.11(syst) scale μ2≈13(GeV/c)2 momentum fraction 〈x〉≈0.11....
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...