Search results for "Fysiikka"
showing 10 items of 1348 documents
Technology Impact on Neutron-Induced Effects in SDRAMs : A Comparative Study
2021
International audience; This study analyses the response of synchronous dynamic random access memories to neutron irradiation. Three different generations of the same device with different node sizes (63, 72, and 110 nm) were characterized under an atmospheric-like neutron spectrum at the ChipIr beamline in the Rutherford Appleton Laboratories, UK. The memories were tested with a reduced refresh rate to expose more single-event upsets and under similar conditions provided by a board specifically developed for this type of study in test facilities. The board has also been designed to be used as a nanosatellite payload in order to perform similar tests. The neutron-induced failures were studi…
Plasmon mass scale in two dimensional classical nonequilibrium gauge theory
2018
We study the plasmon mass scale in weakly coupled strongly interacting nonabelian gauge theory in a two dimensional configuration that mimics the boost invariant initial color fields in a heavy ion collision. We numerically measure the plasmon mass scale using three different methods: a Hard Thermal Loop (HTL) expression involving the quasiparticle spectrum constructed from Coulomb gauge field correlators, an effective dispersion relation and the measurement of oscillations between electric and magnetic energies after introducing a spatially uniform perturbation to the electric field. We find that the hard thermal loop expression and the uniform electric field measurement are in rough agree…
Two-photon transitions of charmonia on the light front
2022
We investigate the two-photon transitions $H_{c\bar c} \to \gamma^*\gamma$ of the charmonium system in light-front dynamics. The light-front wave functions were obtained from solving the effective Hamiltonian based on light-front holography and one-gluon exchange interaction within the basis light-front quantization approach. We compute the two-photon transition form factors as well as the two-photon decay widths for S- and P-wave charmonia, $\eta_c$ and $\chi_{cJ}$ and their excitations. Without introducing any free parameters, our predictions are in good agreement with the recent experimental measurements by BaBar and Belle, shedding light on the relativistic nature of charmonium.
Nuclear geometry at high energy from exclusive vector meson production
2022
We show that when saturation effects are included one obtains a good description of the exclusive $\mathrm{J}/\psi$ production spectra in ultra peripheral lead-lead collisions as recently measured by the ALICE Collaboration at the LHC. As exclusive spectra are sensitive to the spatial distribution of nuclear matter at small Bjorken-$x$, this implies that gluon saturation effects modify the impact parameter profile of the target as we move towards small $x$. In addition to saturation effects, we find a preference for larger nuclear strong-interaction radii compared to the typical charge radius. We demonstrate the role of finite photon transverse momentum and the interference between the case…
Exclusive production of light vector mesons at next-to-leading order in the dipole picture
2022
Exclusive production of light vector mesons in deep inelastic scattering is calculated at next-to-leading order in the dipole picture in the limit of high photon virtuality. The resulting expression is free of any divergences and suitable for numerical evaluations. The higher-order corrections are found to be numerically important, but they can be mostly captured by the nonperturbative fit parameters describing the initial condition for the small-$x$ evolution of the dipole scattering amplitude. The vector meson production cross section is shown to depend only weakly on the meson distribution amplitude and the factorization scale. We also present phenomenological comparisons of our result t…
Signatures of gluon saturation from structure-function measurements
2022
We study experimentally observable signals for nonlinear QCD dynamics in deep inelastic scattering (DIS) at small Bjorken variable $x$ and moderate virtuality $Q^2$, by quantifying differences between the linear Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution and nonlinear evolution with the Balitsky-Kovchegov (BK) equation. To remove the effect of the parametrization freedom in the initial conditions of both equations, we first match the predictions for the DIS structure functions $F_2$ and $F_{\rm L}$ from both frameworks in a region in $x,Q^2$ where both frameworks should provide an accurate description of the relevant physics. The differences in the dynamics are then quanti…
Rapidity dependence of initial state geometry and momentum correlations in p+Pb collisions
2022
Event geometry and initial state correlations have been invoked as possible explanations of long range azimuthal correlations observed in high multiplicity p+p and p+Pb collisions. We study the rapidity dependence of initial state momentum correlations and event-by-event geometry in $\sqrt{s}=5.02~\rm{TeV}$ p+Pb collisions within the 3+1D IP-Glasma model~\cite{Schenke:2016ksl}, where the longitudinal structure is governed by JIMWLK rapidity evolution of the incoming nuclear gluon distributions. We find that the event geometry is correlated across large rapidity intervals whereas initial state momentum correlations are relatively short range in rapidity. Based on our results, we discuss impl…
Flow correlations from a hydrodynamics model with dynamical freeze-out and initial conditions based on perturbative QCD and saturation
2022
We extend the applicability of the hydrodynamics, perturbative QCD and saturation -based EKRT (Eskola-Kajantie-Ruuskanen-Tuominen) framework for ultrarelativistic heavy-ion collisions to peripheral collisions by introducing dynamical freeze-out conditions. As a new ingredient compared to the previous EKRT computations we also introduce a non-zero bulk viscosity. We compute various hadronic observables and flow correlations, including normalized symmetric cumulants, mixed harmonic cumulants and flow-transverse momentum correlations, and compare them against measurements from the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC). We demonstrate that the inclu…
Light-front wavefunctions of mesons by design
2022
AbstractWe develop a mechanism to build the light-front wavefunctions (LFWFs) of meson bound states on a small-sized basis function representation. Unlike in a standard Hamiltonian formalism, the Hamiltonian in this method is implicit, and the information of the system is carried directly by the functional form and adjustable parameters of the LFWFs. In this work, we model the LFWFs for four charmonium states, $$\eta _c$$ η c , $$J/\psi $$ J / ψ , $$\psi '$$ ψ ′ , and $$\psi (3770)$$ ψ ( 3770 ) as superpositions of orthonormal basis functions. We choose the basis functions as eigenfunctions of an effective Hamiltonian, which has a longitudinal confining potential in addition to the transver…
Two-neutrino ββ decay of 136Xe to the first excited 0+ state in 136Ba
2023
We calculate the nuclear matrix element for the two-neutrino $\beta\beta$ decay of $^{136}$Xe into the first excited $0^+$ state of $^{136}$Ba. We use different many-body methods: the quasiparticle random-phase approximation (QRPA) framework, the nuclear shell model, the interacting boson model (IBM-2), and an effective field theory (EFT) for $\beta$ and $\beta\beta$ decays. While the QRPA suggests a decay rate at the edge of current experimental limits, the shell model points to a half-life about two orders of magnitude longer. The predictions of the IBM-2 and the EFT lie in between, and the latter provides systematic uncertainties at leading order. An analysis of the running sum of the nu…