6,357 research outputs found
The improved nuclear parton distributions
In this paper we propose an improvement of the EKS nuclear parton
distributions for the small x region of high energy processes, where the
perturbative high parton density effects cannot be disregarded. We analyze the
behavior of the ratios and and verify that at small x
they are strongly modified when compared to the EKS predictions. The
implications of our results for the heavy ion collisions in RHIC and LHC are
discussed.Comment: 16 pages, 2 figure
Breakdown of the static picture of defect energetics in halide perovskites: the case of the Br vacancy in CsPbBr3
We consider the Br vacancy in CsPbBr3 as a prototype for the impact of
structural dynamics on defect energetics in halide perovskites (HaPs). Using
first-principles molecular dynamics based on density functional theory, we find
that the static picture of defect energetics breaks down; the energy of the Br
vacancy level is found to be intrinsically dynamic, oscillating by as much as 1
eV on the ps time scale at room temperature. These significant energy
fluctuations are correlated with the distance between the neighboring Pb atoms
across the vacancy and with the electrostatic potential at these Pb atomic
sites. We expect this unusually strong coupling of structural dynamics and
defect energetics to bear important implications for both experimental and
theoretical analysis of defect characteristics in HaPs. It may also hold
significant ramifications for carrier transport and defect tolerance in this
class of photovoltaic materials.Comment: 5 figures, 1 tabl
Pseudocercospora opuntiae sp. nov., the causal organism of cactus leaf spot in Mexico.
Pseudocercospora opuntiae is newly described from Opuntia spp. from Mexico, where it causes a serious disease of this host. Although P. opuntiae is morphologically similar to other members of the genus with pigmented conidia and conidiophores, and unthickened, not darkened conidiogenous scars, DNA sequence data of the ITS region revealed that it clusters distant from other species of Pseudocercospora within Mycosphaerella. These data support the assumption that Pseudocereospora is paraphyletic within Mycosphaerella
Nuclear shadowing from exclusive quarkonium photoproduction at the BNL RHIC and CERN LHC
The photonuclear production of vector mesons in ultraperipheral heavy ion
collisions is investigated within the collinear approach using different
parameterizations for the nuclear gluon distribution. The integrated cross
section and the rapidity distribution for the () process are computed for energies of RHIC and LHC. A comparison with
the recent PHENIX data on coherent production of mesons is also
presented. We demonstrate that the study of the exclusive quarkonium
photoproduction can be used to constrain the nuclear effects in the gluon
distribution.Comment: 8 pages, 4 figures, 2 tables. Version to be published in Physical
Review
Effective potential at finite temperature in a constant magnetic field I: Ring diagrams in a scalar theory
We study symmetry restoration at finite temperature in the theory of a
charged scalar field interacting with a constant, external magnetic field. We
compute the finite temperature effective potential including the contribution
from ring diagrams. We show that in the weak field case, the presence of the
field produces a stronger first order phase transition and that the temperature
for the onset of the transition is lower, as compared to the case without
magnetic field.Comment: Expanded comments, 4 figures added. Conclusions unchanged. Version to
match published pape
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