University of Warsaw

About: University of Warsaw is a education organization based out in Warsaw, Poland. It is known for research contribution in the topics: Population & Large Hadron Collider. The organization has 20832 authors who have published 56617 publications receiving 1185084 citations. The organization is also known as: Uniwersytet Warszawski & Warsaw University.

Directed and elliptic flow of charged pions and protons in Pb + Pb collisions at 40A and 158A GeV

Abstract: Directed and elliptic flow measurements for charged pions and protons are reported as a function of transverse momentum, rapidity, and centrality for 40A and 158A GeV Pb+Pb collisions, as recorded by the NA49 detector. Both the standard method of correlating particles with an event plane and the cumulant method of studying multiparticle correlations are used. In the standard method the directed flow is corrected for conservation of momentum. In the cumulant method elliptic flow is reconstructed from genuine four-, six-, and eight-particle correlations, showing the first unequivocal evidence for collective motion in A+A collisions at SPS energies.

ASASSN-14ae: a tidal disruption event at 200 Mpc

Abstract: ASASSN-14ae is a candidate tidal disruption event (TDE) found at the centre of SDSS J11084011+3405522 (d ≃ 200 Mpc) by the All-Sky Automated Survey for Supernovae (ASAS-SN) We present ground-based and Swift follow-up photometric and spectroscopic observations of the source, finding that the transient had a peak luminosity of L ≃ 8 × 1043 erg s−1 and a total integrated energy of E ≃ 17 × 1050 erg radiated over the ∼5 months of observations presented The blackbody temperature of the transient remains roughly constant at T ∼ 20 000 K while the luminosity declines by nearly 15 orders of magnitude during this time, a drop that is most consistent with an exponential, L ∝ e-t/t 0 with t0 ≃ 39 d The source has broad Balmer lines in emission at all epochs as well as a broad He ii feature emerging in later epochs We compare the colour and spectral evolution to both supernovae and normal AGN to show that ASASSN-14ae does not resemble either type of object and conclude that a TDE is the most likely explanation for our observations At z = 00436, ASASSN-14ae is the lowest-redshift TDE candidate discovered at optical/UV wavelengths to date, and we estimate that ASAS-SN may discover 01–3 of these events every year in the future

Variation-perturbation treatment of the hydrogen bond between water molecules

Abstract: The hydrogen-bond energy of two water molecules has been calculated as a sum of the electrostatic, exchange, induction and dispersion contributions, neglecting the electron correlation within the free monomers. The last two contributions have been evaluated by applying a variation-perturbation procedure and making use of an extensive basis set of contracted gaussian functions. It has been shown that the sum of the electrostatic, exchange and induction energies is very close to the binding energy obtained within the SCF scheme. The dispersion contribution to the hydrogen-bond energy amounts to about 2 kcal/mole and causes substantial reduction of the equilibrium distance of the oxygen atoms. The minimum of the total energy is attained at 2·86 A and its depth is equal to 5·8 kcal/mole. These values are consistent with the experimental results.

Neutron density distributions deduced from antiprotonic atoms.

Abstract: The differences between neutron and proton density distributions at large nuclear radii in stable nuclei were determined. Two experimental methods were applied: nuclear spectroscopy analysis of the antiproton annihilation residues one mass unit lighter than the target mass and the measurements of strong-interaction effects on antiprotonic x rays. Assuming the validity of two-parameter Fermi neutron and proton distributions at these large radii, the conclusions are that the two experiments are consistent with each other and that for neutron rich nuclei it is mostly the neutron diffuseness which increases and not the half-density radius. The obtained neutron and proton rms radii differences are in agreement with previous results.