Search results for "Dependence"
showing 10 items of 2462 documents
Global analysis of nuclear PDFs – latest developments
2013
Abstract In this review talk I discuss the latest developments in the DGLAP-based global analysis of nuclear parton distribution functions (nPDFs), focusing on the recent EPS09, nCTEQ and DSSZ global fits. I also briefly review the recent analysis for assigning a spatial dependence to the globally analysed nPDFs, resulting in the new sets EPS09s and EKS98s (“s” for spatial). With these, one can now compute nuclear hard-process cross sections and estimate their nPDF-originating uncertainties in different centrality classes for the first time consistently with the global nPDF fits.
Polarized photon measurements of the12C(γ→,pp)and12C(γ→,pn)reactions forEγ=160−350MeV
2001
The ${}^{12}\mathrm{C}(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}},pp)$ and ${}^{12}\mathrm{C}(\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\gamma}},pn)$ reactions have been studied for ${E}_{\ensuremath{\gamma}}=160\ensuremath{-}350$ MeV using linearly polarized photons from the Glasgow tagged photon spectrometer at the Mainz microtron MAMI. Both reaction channels show a negative photon asymmetry $\ensuremath{\Sigma}$ for missing energies ${E}_{m}$ below 70 MeV, where direct emission nucleon pairs is expected. A strong peak at low ${E}_{m}$ is observed in ${\ensuremath{\Sigma}}_{(\ensuremath{\gamma},pp)},$ but not in ${\ensuremath{\Sigma}}_{(\ensuremath{\gamma},pn)}.$ Furth…
Determining the Θ+ quantum numbers through the K+p→π+K+n reaction
2004
Abstract We study the K+p→π+K+n reaction with some kinematics suited to the production of the Θ+ resonance recently observed. We show that, independently of the quantum numbers of the Θ+, a resonance signal is always observed in the K+ forward direction. In addition, we also show how a combined consideration of the strength at the peak, and the angular dependence of polarization observables can help determine the Θ+ quantum numbers using the present reaction.
Nuclear matter effects onJ/ψproduction in asymmetric Cu + Au collisions atsNN=200GeV
2014
We report on J/psi production from asymmetric Cu + Au heavy-ion collisions at root S-NN = 200 GeV at the Relativistic Heavy Ion Collider at both forward (Cu-going direction) and backward (Au-going direction) rapidities. The nuclear modification of J/psi yields in Cu + Au collisions in the Au-going direction is found to be comparable to that inAu + Au collisions when plotted as a function of the number of participating nucleons. In the Cu-going direction, J/psi production shows a stronger suppression. This difference is comparable in magnitude and has the same sign as the difference expected from shadowing effects due to stronger low-x gluon suppression in the larger Au nucleus.
Neutron yields from thick 12C and 9Be targets irradiated by 50 and 65 MeV deuterons
2001
Abstract Absolute intensities, angular distributions and energy spectra of neutrons emitted from thick 12 C and 9 Be targets irradiated with 50 and 65 MeV deuterons, respectively, have been measured. The neutron spectra were measured by time-of-flight (TOF) technique. The detectors provided continuous coverage from 0° to 60° where a significant angular dependence of emitted neutrons was found. The yield of 0.109(10) neutrons/deuteron from the 9 Be target is a factor of two higher than that from the 12 C target, 0.056(6) neutrons/deuteron. The hardness parameters of the neutron spectra are calculated for the radiation damage studies of the silicon devices.
Messung der Spinpolarisation von 900 eV-Elektronen nach elastischer Streuung an Schwermetallfolien in Abh�ngigkeit von der Targettemperatur
1967
900 eV electrons are elastically scattered by solid targets of tungsten, platinum and gold. The angular dependence of the scattered intensity and of spin polarizationP(Θ) is investigated as a function of the target temperature. The influence of hydrogen on the scattering process by a gold target is investigated too.
Schematic and realistic model calculations of the isovector spin monopole excitations in 116In
2012
The excitation of Gamow-Teller (GT) and isovector spin monopole (IVSM) Jπ=1+ modes in 116In by (p,n) and (n,p) charge-exchange reactions on 116Cd and on 116Sn, respectively, is studied within the framework of the quasiparticle random-phase approximation. The calculations have been performed both for schematic and realistic model situations. It appears that the calculated admixture of the IVSM and Gamow-Teller (GT) Jπ=1+ excitations is negligible and that the contribution to the strength above 20 MeV of excitation energy, in 116In, is due to the IVSM (σr2t ±) mode. This result is compared with the recent experimental work that reported a large amount of both (p,n) and (n,p) strength beyond 1…
Neutron-skin effect and centrality dependence of high-pT observables in nuclear collisions
2016
We report on our studies of the neutron-skin effects in high-pT observables at the LHC. We study the impact of the neutron-skin effect on the centrality dependence of inclusive direct photon, highpT hadron and W± production in nuclear collisions at the LHC. The neutron-skin effect refers to the observation that in spherical heavy nuclei, the tail of the neutron distribution extends farther than the distribution of protons, which can affect observables sensitive to electroweak phenomena in very peripheral collisions. We quantify this effect for direct photons, charged hadrons and W bosons as a function of the collision centrality. In the case of direct photons we find that it will be difficu…
Asymptotic Safety in Quantum Einstein Gravity: Nonperturbative Renormalizability and Fractal Spacetime Structure
2007
The asymptotic safety scenario of Quantum Einstein Gravity, the quantum field theory of the spacetime metric, is reviewed and it is argued that the theory is likely to be nonperturbatively renormalizable. It is also shown that asymptotic safety implies that spacetime is a fractal in general, with a fractal dimension of 2 on sub-Planckian length scales.
Extracting the impact parameter dependence of the nPDFs from the EKS98 and EPS09 global fits
2013
As all the globally fitted nuclear PDFs (nPDFs) have been so far impact parameter independent, it has not been possible to calculate the hard process cross sections in different centrality classes consistently with the global analyses. In \cite{Helenius:2012wd} we have offered a solution to this problem by determining two spatially dependent nPDF sets, \texttt{EPS09s} and \texttt{EKS98s}, using the $A$-systematics of the earlier global fits EPS09 and EKS98 and an assumption that the spatial dependence can be written as a power series of the nuclear thickness function. For a data comparison, we have calculated the nuclear modification factor of inclusive neutral pion production in d+Au colli…