Study of elementary reactions with the hades dielectron spectrometer

Results obtained with the HADES dielectron spectrometer at GSI are discussed, with emphasis on dilepton production in elementary reactions.Díaz Medina, José, [email protected] ; Gil Ortiz, Alejandro, [email protected]

In-Medium Effects on K0 Mesons in Relativistic Heavy-Ion Collisions

We present the transverse momentum spectra and rapidity distributions of $\pi^{-}$ and K$^0_S$ in Ar+KCl reactions at a beam kinetic energy of 1.756 A GeV measured with the spectrometer HADES. The reconstructed K$^0_S$ sample is characterized by good event statistics for a wide range in momentum and rapidity. We compare the experimental $\pi^{-}$ and K$^0_S$ distributions to predictions by the IQMD model. The model calculations show that K$^0_S$ at low tranverse momenta constitute a particularly well suited tool to investigate the kaon in-medium potential. Our K$^0_S$ data suggest a strong repulsive in-medium K$^0$ potential of about 40 MeV strength.Comment: 10 pages, 10 figures, accepted by Phys. Rev.

Meson and di-electron production with HADES

The HADES experiment, installed at GSI, Darmstadt, measures di-electron production in A+A, p/pi+N and p/pi+A collisions. Here, the pi0 and eta Dalitz decays have been reconstructed in the exclusive p+p reaction at 2.2 GeV to form a reference cocktail for long-lived di-electron sources. In the C+C reaction at 1 and 2 GeV/u, these long-lived sources have been subtracted from the measured inclusive e+e- yield to exhibit the signal from the early phase of the collision. The results suggest that resonances play an important role in dense nuclear matter.Comment: Invited plenary talk at the 10th International Workshop On Meson Production, Properties And Interaction (MESON 2008) 6-10 Jun 2008, Cracow, Polan

Revista de Vertebrados de la Estación Biológica de Doñaña

Comportamiento reproductor del camaleón común (Chamaeleo chamaeleon L.) en el sur de EspañaDistribución de los reptiles en la provincia de Granada (SE. Península Ibérica)Datos sobre la reproducción y el crecimientode Psammodromus hispanicus Fitzinger, 1826 en un medio adehesado de la España CentralVariación en la colocación y orientación del nido del Alzacola (Cercotrichas galactotes) en dos especies de árbolesOrganización de la comunidad de aves reproductora en las landas montanas del País Vasco AtlánticoEcología de una población ibérica de lobos (Canis Lupus)Etude biométrique des Crosidures (Soricidae, Insectivora) de la región de Massa (Souss, Maroe).Variación geográfica del género Eliomys en la Península IbéricaTendencias gregarias del Ciervo (Cervus elaphus) en Doñana.Data on the autumn diet of the red deer (Cervus elaphus L. 1758) in the Montes de Toledo (Central Spain)Nota sobre la coexistencia de Hyla arborea (L. 1758E Hyla meridionalis (Boettger 1874) rn rl Valle del TiétarCalendario reproductivo y tamaño de las puesta en el galápago leproso, Mauremys leprosa (Shweigger, 1812), en Doñana, HuelvaPelícola (Felicola) inaqualis Piager, 1880 (MALLOPHAGA:TRICHODECTIDAE) parásito deE Herpestes ichneumon L (CARNIVORA: HERPESTIDAE)Abundancia y amplitud de los desplazamientos de Apodemus sylvaticus en cuatro biotopos de Doñana que difieren en cobertura vegetalPeer reviewe

Dilepton production in pp and CC collisions with HADES

Dilepton production has been measured with HADES, the "High Acceptance DiElectron Spectrometer". In pp collisions at 2.2GeV kinetic beam energy, exclusive eta production and the Dalitz decay eta -> gamma e+e- has been reconstructed. The electromagnetic form factor is well in agreement with existing data. In addition, an inclusive e+e- spectrum from the C+C reaction at 2AGeV is presented and compared with a thermal model.Comment: 11 pages, 3 figures, proceedings of the IVth International Conference on Quarks and Nuclear Physics, Madrid, June 5th-10th, submitted to Eur.Phys.J.

PMAS integral field spectroscopy of luminous infrared galaxies. I.- The atlas

In this paper we present PMAS optical (3800-7200A) IFS of the northern hemisphere portion of a volume-limited sample of 11 LIRGs. The PMAS observations typically cover the central ~5kpc and are complemented with HST/NICMOS images. For most LIRGs in our sample, the peaks of the continuum and gas (e.g., Halpha, [NII]) emissions coincide, unlike what is observed in local, strongly interacting ULIRGs. The only exceptions are galaxies with circumnuclear rings of star formation where the most luminous Halpha emitting regions are found in the rings rather than in the nuclei, and the displacements are well understood in terms of differences in the stellar populations. A large fraction of the nuclei of these LIRGs are classified as LINER and intermediate LINER/HII, or composite objects. The excitation conditions of the integrated emission depend on the relative contributions of HII regions and the diffuse emission to the line emission over the PMAS FoV. Galaxies dominated by high surface-brightness HII regions show integrated HII-like excitation. A few galaxies show slightly larger integrated [NII]/Halpha and [SII]/Halpha line ratios than the nuclear ones, probably because of more contribution from the diffuse emission. The Halpha velocity fields over the central few kpc are generally consistent, at least to first order, with rotational motions. The velocity fields of most LIRGs are similar to those of disk galaxies, in contrast to the highly perturbed fields of most local, strongly interacting ULIRGs. The peak of the Halpha velocity dispersion coincides with the position of the nucleus and is likely to be tracing mass. All these results are similar to the properties of z~1 LIRGs, and they highlight the importance of detailed studies of flux-limited samples of local LIRGs. (Abridged)Comment: Accepted for publication in Astronomy and Astrophysic

Precise measurement of the top quark mass in the dilepton channel at D0

We measure the top quark mass (mt) in ppbar collisions at a center of mass energy of 1.96 TeV using dilepton ttbar->W+bW-bbar->l+nubl-nubarbbar events, where l denotes an electron, a muon, or a tau that decays leptonically. The data correspond to an integrated luminosity of 5.4 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider. We obtain mt = 174.0 +- 1.8(stat) +- 2.4(syst) GeV, which is in agreement with the current world average mt = 173.3 +- 1.1 GeV. This is currently the most precise measurement of mt in the dilepton channel.Comment: 7 pages, 4 figure

Search for new fermions ("quirks") at the Fermilab Tevatron Collider

We report results of a search for particles with anomalously high ionization in events with a high transverse energy jet and large missing transverse energy in $2.4$ fb$^{-1}$ of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron $p\bar{p}$ collider. Production of such particles (quirks) is expected in scenarios with extra QCD-like {\it SU(N)} sectors, and this study is the first dedicated search for such signatures. We find no evidence of a signal and set a lower mass limit of 107 ~GeV for the mass of a charged quirk with strong dynamics scale $\Lambda$ in the range from 10 keV to 1 MeV.Comment: submitted to Phys. Rev. Letter

Direct measurement of the mass difference between top and antitop quarks

We present a direct measurement of the mass difference between top and antitop quarks (dm) in lepton+jets top-antitop final states using the "matrix element" method. The purity of the lepton+jets sample is enhanced for top-antitop events by identifying at least one of the jet as originating from a b quark. The analyzed data correspond to 3.6 fb-1 of proton-antiproton collisions at 1.96 TeV acquired by D0 in Run II of the Fermilab Tevatron Collider. The combination of the e+jets and mu+jets channels yields dm = 0.8 +/- 1.8 (stat) +/- 0.5 (syst) GeV, which is in agreement with the standard model expectation of no mass difference.Comment: submitted to Phys. Rev.

Hyperon production in Ar+KCl collisions at 1.76A GeV

We present transverse momentum spectra, rapidity distribution and multiplicity of Lambda-hyperons measured with the HADES spectrometer in the reaction Ar(1.76A GeV)+KCl. The yield of Xi- is calculated from our previously reported Xi-/(Lambda+Sigma0) ratio and compared to other strange particle multiplicities. Employing a strangeness balance equation the multiplicities of the yet unmeasured charged Sigma hyperons can be estimated. Finally a statistical hadronization model is used to fit the yields of pi-, K+, K0s, K-, phi, Lambda and Xi-. The resulting chemical freeze-out temperature of T=(76+-2) MeV is compared to the measured slope parameters obtained from fits to the transverse mass distributions of the particles