We report first measurements of e+e- pair production in the mass region 0.4 between 40 and 60 MeV/c. The absolute cross section of the excess depends weakly on centrality, while those from a ...theoretical model calculation incorporating an in-medium broadened ρ spectral function and radiation from a quark gluon plasma or hadronic cocktail contributions increase dramatically with an increasing number of participant nucleons. Model calculations of photon-photon interactions generated by the initial projectile and target nuclei describe the observed excess yields but fail to reproduce the p$\mathbb 2\atop{T}$ distributions.
A new experiment SPASCHARM devoted to a systematic study of polarization phenomena in hadron-hadron interactions in the energy range 10-70 GeV is under preparation at IHEP (Protvino). The physical ...observables will be single-spin asymmetries, hyperon polarizations and spin-density matrix elements. A universal setup will detect and identify various neutral and charge particles in the full azimuthal angle and a wide polar angle range. A polarized target is used to measure the SSA. The SPASCHARM sub-detectors are being designed and constructed now. The possibility of obtaining a polarized proton beam for the SPASCHARM experiment from Lambda decays is under study.
The STAR Collaboration reports measurements of the longitudinal double-spin asymmetry, ALL, for neutral pions produced at forward directions in polarized proton-proton collisions, at a center-of-mass ...energy of 510 GeV. Results are given for transverse momenta in the range 2
We present the first measurements of the longitudinal double-spin asymmetry ALL for dijets with at least one jet reconstructed within the pseudorapidity range 0.8<η<1.8. The dijets were measured in ...polarized pp collisions at a center-of-mass energy s=200 GeV. Values for ALL are determined for several distinct event topologies, defined by the jet pseudorapidities, and span a range of parton momentum fraction x down to x~0.01. The measured asymmetries are found to be consistent with the predictions of global analyses that incorporate the results of previous RHIC measurements. They will provide new constraints on Δg(x) in this poorly constrained region when included in future global analyses.
The Panda experiment is a key experiment at FAIR – European Facility for Antiproton and Ion Research, which is in the development stage in Darmstadt (Germany). The physical program of the experiment ...is focused on the search for exotic particles, research on hadron spectroscopy, the structure of nucleons, nuclear-matter effects, hypernuclei, and in other areas. New experimental forms of matter predicted by theory – glueballs and hybrids – are of great interest. They have not yet been observed. The PANDA facility will be assembled in the storage ring of the HESR antiproton beam. Antiprotons with energy from 1.5 to 15 GeV will be accumulated in the ring. Up to 2·10
7
interactions/sec are expected on the internal hydrogen (cluster or corpuscular) target. In addition to the high luminosity of the experiment (2·10
32
cm
–2
·sec
–1
), the beam will be monochromatic. Because of stochastic and electronic cooling, pulsed stretching of the beam is expected to be at the level 10
–4
–10
–5
, which makes it possible to measure the mass of the particles with record high resolution 100 keV. Domestic institutes are participating in the development of the PANDA facility.
Here, rapidity-odd directed flow measurements at midrapidity are presented for Λ, $\bar{Λ}$, K±, K$0\atop{s}$ and Φ at √sNN = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4 and 200 GeV in Au+Au collisions ...recorded by the STAR detector at the Relativistic Heavy Ion Collider. These measurements greatly expand the scope of data available to constrain models with differing prescriptions for the equation of state of quantum chromodynamics. Results show good sensitivity for testing a picture where flow is assumed to be imposed before hadron formation and the observed particles are assumed to form via coalescence of 3 constituent quarks. Lastly, the pattern of departure from a coalescence-inspired sum-rule can be a valuable new tool for probing the collision dynamics.
We report on the effects of radiation on the light output of lead tungstate crystals. The crystals were irradiated by pure, intense high-energy electron and hadron beams as well as by a mixture of ...hadrons, neutrons and gammas. The crystals were manufactured in Bogoroditsk, Apatity (both Russia), and Shanghai (China). These studies were carried out at the 70-GeV proton accelerator in Protvino.
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