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Träfflista för sökning "WFRF:(Böhmer A. C.) "

Sökning: WFRF:(Böhmer A. C.)

  • Resultat 1-10 av 12
  • [1]2Nästa
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1.
  • Abelev, B, et al. (författare)
  • Exclusive J/ψ Photoproduction off Protons in Ultraperipheral p-Pb Collisions at sqrt[s_{NN}]=5.02 TeV.
  • 2014
  • Ingår i: Physical Review Letters. - American Physical Society. - 1079-7114. ; 113:23
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the first measurement at the LHC of exclusive J/ψ photoproduction off protons, in ultraperipheral proton-lead collisions at sqrt[s_{NN}]=5.02 TeV. Events are selected with a dimuon pair produced either in the rapidity interval, in the laboratory frame, 2.5<y<4 (p-Pb) or -3.6<y<-2.6 (Pb-p), and no other particles observed in the ALICE acceptance. The measured cross sections σ(γ+p→J/ψ+p) are 33.2±2.2(stat)±3.2(syst)±0.7(theor) nb in p-Pb and 284±36(stat)_{-32}^{+27}(syst)±26(theor) nb in Pb-p collisions. We measure this process up to about 700 GeV in the γp center of mass, which is a factor of two larger than the highest energy studied at HERA. The data are consistent with a power law dependence of the J/ψ photoproduction cross section in γp energies from about 20 to 700 GeV, or equivalently, from Bjorken x scaling variable between ∼2×10^{-2} and ∼2×10^{-5}, thus indicating no significant change in the gluon density behavior of the proton between HERA and LHC energies.
2.
  • Abelev, B, et al. (författare)
  • Measurement of Prompt D-Meson Production in p-Pb Collisions at sqrt[s_{NN}]=5.02 TeV.
  • 2014
  • Ingår i: Physical Review Letters. - American Physical Society. - 1079-7114. ; 113:23
  • Tidskriftsartikel (refereegranskat)abstract
    • The p_{T}-differential production cross sections of the prompt charmed mesons D^{0}, D^{+}, D^{*+}, and D_{s}^{+} and their charge conjugate in the rapidity interval -0.96<y_{cms}<0.04 were measured in p-Pb collisions at a center-of-mass energy sqrt[s_{NN}]=5.02 TeV with the ALICE detector at the LHC. The nuclear modification factor R_{pPb}, quantifying the D-meson yield in p-Pb collisions relative to the yield in pp collisions scaled by the number of binary nucleon-nucleon collisions, is compatible within the 15%-20% uncertainties with unity in the transverse momentum interval 1<p_{T}<24 GeV/c. No significant difference among the R_{pPb} of the four D-meson species is observed. The results are described within uncertainties by theoretical calculations that include initial-state effects. The measurement adds experimental evidence that the modification of the momentum spectrum of D mesons observed in Pb-Pb collisions with respect to pp collisions is due to strong final-state effects induced by hot partonic matter.
3.
  • Davies, Gail, et al. (författare)
  • Study of 300,486 individuals identifies 148 independent genetic loci influencing general cognitive function
  • 2018
  • Ingår i: Nature Communications. - Nature Publishing Group. - 2041-1723. ; 9:1
  • Tidskriftsartikel (refereegranskat)abstract
    • General cognitive function is a prominent and relatively stable human trait that is associated with many important life outcomes. We combine cognitive and genetic data from the CHARGE and COGENT consortia, and UK Biobank (total N = 300,486; age 16-102) and find 148 genome-wide significant independent loci (P &amp;lt; 5 × 10-8) associated with general cognitive function. Within the novel genetic loci are variants associated with neurodegenerative and neurodevelopmental disorders, physical and psychiatric illnesses, and brain structure. Gene-based analyses find 709 genes associated with general cognitive function. Expression levels across the cortex are associated with general cognitive function. Using polygenic scores, up to 4.3% of variance in general cognitive function is predicted in independent samples. We detect significant genetic overlap between general cognitive function, reaction time, and many health variables including eyesight, hypertension, and longevity. In conclusion we identify novel genetic loci and pathways contributing to the heritability of general cognitive function.
4.
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5.
  • Maierbeck, P., et al. (författare)
  • Structure of 55Ti from relativistic one-neutron knockout
  • 2009
  • Ingår i: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 675:1, s. 22-27
  • Tidskriftsartikel (refereegranskat)abstract
    • Results are presented from a one-neutron knockout reaction at relativistic energies on 56Ti using the GSI FRS as a two-stage magnetic spectrometer and the Miniball array for gamma-ray detection. Inclusive and exclusive longitudinal momentum distributions and cross-sections were measured enabling the determination of the orbital angular momentum of the populated states. First-time observation of the 955(6) keV -hole state in 55Ti is reported. The measured data for the first time proves that the ground state of 55Ti is a 1/2- state, in agreement with shell-model calculations using the GXPF1A interaction that predict a sizable N=34 gap in 54Ca.
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6.
  • Schwertel, S., et al. (författare)
  • One-neutron knockout from Sc51-55
  • 2012
  • Ingår i: European Physical Journal A. - 1434-601X .- 1434-6001. ; 48:Dec., s. 191
  • Tidskriftsartikel (refereegranskat)abstract
    • Results are presented from a one-neutron knockout experiment at relativistic energies of approximate to 420 A MeV on Sc51-55 using the GSI Fragment Separator as a two-stage magnetic spectrometer and the Miniball array for gamma-ray detection. Inclusive longitudinal momentum distributions and cross-sections were measured enabling the determination of the contributions corresponding to knockout from the nu p(1/2), nu p(3/2), (L = 1) and nu f(7/2), nu f(5/2) (L = 3) neutron orbitals. The observed L = 1 and L = 3 contributions are compared with theoretical cross-sections using eikonal knockout theory and spectroscopic factors from shell model calculations using the GXPF1A interaction. The measured inclusive knockout cross-sections generally follow the trends expected theoretically and given by the spectroscopic strength predicted from the shell model calculations. However, the deduced L = 1 cross-sections are generally 30-40% higher while the L = 3 contributions are about a factor of two smaller than predicted. This points to a promotion of neutrons from the nu f(7/2) to the nu p(3/2) orbital indicating a weakening of the N = 28 shell gap in these nuclei. While this is not predicted for the phenomenological GXPF1A interaction such a weakening is predicted by recent calculations using realistic low-momentum interactions V-lowk obtained by evolving a chiral N3LO nucleon-nucleon potential.
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7.
  • Cortina-Gil, D., et al. (författare)
  • CALIFA, a Dedicated Calorimeter for the R3B/FAIR
  • 2014
  • Ingår i: Nuclear Data Sheets. - 1095-9904 .- 0090-3752. ; 120, s. 99-101
  • Konferensbidrag (refereegranskat)abstract
    • The R3B experiment (Reactions with Relativistic Radioactive Beams) at FAIR (Facility for Antiproton and Ion Research) is a versatile setup dedicated to the study of reactions induced by high-energy radioactive beams. It will provide kinematically complete measurements with high efficiency, acceptance and resolution, making possible a broad physics program with rare-isotopes. CALIFA (CALorimeter for In-Flight detection of gamma-rays and high energy charged pArticles), is a complex detector based on scintillation crystals, that will surround the target of the R3B experiment. CALIFA will act as a total absorption gamma-calorimeter and spectrometer, as well as identifier of charged particles from target residues. This versatility is its most challenging requirement, demanding a huge dynamic range, to cover from low energy gamma-rays up to 300 MeV protons. This fact, along with the high-energy of the beams determine the conceptual design of the detector, presented in this paper, together with the technical solutions proposed for its construction.
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8.
  • Maierbeck, P., et al. (författare)
  • Probing the single particle structure around Ca-54 with one-neutron knock-out
  • 2008
  • Ingår i: AIP Conference Proceedings. - 1551-7616 .- 0094-243X. ; 1012, s. 89-93
  • Konferensbidrag (refereegranskat)abstract
    • The nuclei Ca-47 and Ti-55 were populated in one-neutron knock-out reactions at relativistic energies. Momentum distributions of the residual nuclei as well as gamma-ray spectra were measured at the GSI fragment separator (FRS). Preliminary results of the ongoing analysis including cross sections and spin/parity assignments are presented.
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9.
  • Rossi, D., et al. (författare)
  • Measurement of the dipole polarizability of the unstable neutron-rich nucleus Ni68
  • 2013
  • Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 111:24
  • Tidskriftsartikel (refereegranskat)abstract
    • The E1 strength distribution in Ni68 has been investigated using Coulomb excitation in inverse kinematics at the RB3-LAND setup and by measuring the invariant mass in the one- and two-neutron decay channels. The giant dipole resonance and a low-lying peak (pygmy dipole resonance) have been observed at 17.1(2) and 9.55(17) MeV, respectively. The measured dipole polarizability is compared to relativistic random phase approximation calculations yielding a neutron-skin thickness of 0.17(2) fm. A method and analysis applicable to neutron-rich nuclei has been developed, allowing for a precise determination of neutron skins in nuclei as a function of neutron excess.
10.
  • Rossi, D., et al. (författare)
  • Coulomb excitation of exotic nuclei at the R3B-LAND setup
  • 2013
  • Ingår i: Journal of Physics: Conference Series. - 17426588 .- 17426596. ; 420:1
  • Konferensbidrag (refereegranskat)abstract
    • Exotic Ni isotopes have been measured at the R3B-LAND setup at GSI in Darmstadt, using Coulomb excitation in inverse kinematics at beam energies around 500 MeV/u. As the experimental setup allows kinematically complete measurements, the excitation energy was reconstructed using the invariant mass method. The GDR and additional low-lying strength have been observed in 68Ni, the latter exhausting 4.1(1.9)% of the E1 energy-weighted sum rule. Also, the branching ratio for the non-statistical decay of the excited 68Ni nuclei was measured and amounts to 24(4)%.
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