6,857 research outputs found
d+Au Collisions at STAR
STAR has measured forward pi^0 production in p+p and d+Au collisions at
sqrt{s_{NN}}=200 GeV. The p+p yield generally agrees with NLO pQCD
calculations. The d+Au yield is strongly suppressed at =4.0, well below
shadowing expectations. Exploratory measurements of azimuthal correlations
between forward pi^0 and mid-rapidity charged hadrons show a recoil peak in p+p
that is suppressed in d+Au at low pion energy. These observations are
qualitatively consistent with a saturation picture of the low-x gluon structure
of heavy nuclei. Future measurements to elucidate the dynamics underlying these
observations are also described.Comment: 4 pages, 3 figures. To appear in proceedings of DIS200
Computing Matveev's complexity via crystallization theory: the boundary case
The notion of Gem-Matveev complexity has been introduced within
crystallization theory, as a combinatorial method to estimate Matveev's
complexity of closed 3-manifolds; it yielded upper bounds for interesting
classes of such manifolds. In this paper we extend the definition to the case
of non-empty boundary and prove that for each compact irreducible and
boundary-irreducible 3-manifold it coincides with the modified Heegaard
complexity introduced by Cattabriga, Mulazzani and Vesnin. Moreover, via
Gem-Matveev complexity, we obtain an estimation of Matveev's complexity for all
Seifert 3-manifolds with base and two exceptional fibers and,
therefore, for all torus knot complements.Comment: 27 pages, 14 figure
Global analysis of muon decay measurements
We have performed a global analysis of muon decay measurements to establish
model-independent limits on the space-time structure of the muon decay matrix
element. We find limits on the scalar, vector and tensor coupling of right- and
left-handed muons to right- and left-handed electrons. The limits on those
terms that involve the decay of right-handed muons to left-handed electrons are
more restrictive than in previous global analyses, while the limits on the
other non-standard model interactions are comparable. The value of the Michel
parameter eta found in the global analysis is -0.0036 \pm 0.0069, slightly more
precise than the value found in a more restrictive analysis of a recent
measurement. This has implications for the Fermi coupling constant G_F.Comment: 5 pages, 3 table
Comparing the reaction profiles of single iron catalytic sites in enzymes and in reticular frameworks for methane-to-methanol oxidation
The design of synthetic inorganic catalysts mimicking the first coordination spheres of enzymatic cofactors often results in lower yields and selectivity than their biological counterparts. In this study, we exploit Kohn-Sham density functional methods to compare the reaction profiles of four single iron-based catalysts for the direct oxidation of methane to methanol: two biomimetic models based on two enzymes (cytochrome P450 and taurine dioxygenase [TauD]) and two synthetic reticular frameworks (iron-BEA zeolite and tri-iron oxo-center-based metal-organic framework). Both the biomimetic and inorganic catalysts show almost zero selectivity toward methanol for methane conversions >1% at ambient temperature. This study highlights that iron's first coordination shell can influence selectivity toward methanol but to a limited extent. In the absence of methanol protection strategies, high selectivity can be reached only by mimicking the reaction microenvironment of enzymes beyond the first coordination shell of iron
Astrophysical S factor for the radiative capture 12N(p,gamma)13O determined from the 14N(12N,13O)13C proton transfer reaction
The cross section of the radiative proton capture reaction on the drip line
nucleus 12N was investigated using the Asymptotic Normalization Coefficient
(ANC) method. We have used the 14N(12N,13O)13C proton transfer reaction at 12
MeV/nucleon to extract the ANC for 13O -> 12N + p and calculate from it the
direct component of the astrophysical S factor of the 12N(p,gamma)13O reaction.
The optical potentials used and the DWBA analysis of the proton transfer
reaction are discussed. For the entrance channel, the optical potential was
inferred from an elastic scattering measurement carried out at the same time
with the transfer measurement. From the transfer, we determined the square of
the ANC, C^2(13Og.s.) = 2.53 +/- 0.30 fm-1, and hence a value of 0.33(4) keVb
was obtained for the direct astrophysical S factor at zero energy. Constructive
interference at low energies between the direct and resonant captures leads to
an enhancement of Stotal(0) = 0.42(5) keVb. The 12N(p,gamma)13O reaction was
investigated in relation to the evolution of hydrogen-rich massive Population
III stars, for the role that it may play in the hot pp-chain nuclear burning
processes, possibly occurring in such objects.Comment: 15 pages, 10 figures, 3 tables submitted to Phys. Rev.
Resonant electron heating and molecular phonon cooling in single C junctions
We study heating and heat dissipation of a single \c60 molecule in the
junction of a scanning tunneling microscope (STM) by measuring the electron
current required to thermally decompose the fullerene cage. The power for
decomposition varies with electron energy and reflects the molecular resonance
structure. When the STM tip contacts the fullerene the molecule can sustain
much larger currents. Transport simulations explain these effects by molecular
heating due to resonant electron-phonon coupling and molecular cooling by
vibrational decay into the tip upon contact formation.Comment: Accepted in Phys. Rev. Let
How unique is the Asymptotic Normalisation Coefficient (ANC) method?
The asymptotic normalisation coefficients (ANC) for the vertex B
Be + p is deduced from a set of different proton transfer reactions at
different energies. This set should ensure the peripheral character of the
reaction and availability of data for the elastic channels. The problems
associated with the characteristics of the data and the analysis are discussed.
For a subgroup of the set of available data, the uniqueness property of the
extracted ANC is fulfilled. However, more measurements are needed before a
definite conclusion can be drawn.Comment: 19 pages, 11 figures, to be published in Phys Rev
Fragmentation Barriers of Toroidal and Bubble Nuclei
Journals published by the American Physical Society can be found at http://publish.aps.org/With an improved Boltzmann-Uehling-Uhlenbeck model, the deformation energy surfaces in reactions leading to the formation of toroidal and bubble nuclei are examined for central Mo-92+Mo-92 collisions. We found that the potential maximum, or the fragmentation barrier, occurs at times close to the times when these exotic shapes are formed. However, due to the dynamics of large amplitude compression and expansion, the fragmentation barriers are significantly higher than those estimated from the liquid-drop models
Sex-disaggregated data confirm serum ferritin as an independent predictor of disease severity both in male and female COVID-19 patients
Sex-disaggregated data confirm serum ferritin as an independent predictor of disease severity both in male and female COVID-19 patients
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