Physical Information in the Thermal Continuum Dilepton Spectra

We consider the intermediate mass continuum of dileptons (between $\phi$ and $J/\psi$) in ultrarelativistic heavy--ion collisions. The thermal signal depends essentially on thermodynamic state parameters of the hottest parton stage as $(\tau_i\lambda^q_iT_i^3)^2$ convoluted with an involved detector acceptance function. A refined analysis of the transverse pair momentum spectrum at fixed dilepton transverse mass can reveal the maximum temperature of parton matter.Comment: 3 LaTeX pages including eps figures, contribution to the Erice School on Nuclear Physics 1998 (to be published in "Progress in Particle and Nuclear Physics"

Dileptons and photons from central heavy-ion collisions at CERN-SPS

A unique parameterization of secondary (thermal) dilepton and photon yields in heavy-ion experiments at CERN-SPS is proposed. Adding those thermal yields to background contributions the spectral shapes of the CERES/NA45, NA38, NA50, HELIOS/3 and WA98 data from experiments with lead and sulfur beams can be well described.A unique parameterization of secondary (thermal) dilepton and photon yields in heavy-ion experiments at CERN-SPS is proposed. Adding those thermal yields to background contributions the spectral shapes of the CERES/NA45, NA38, NA50, HELIOS/3 and WA98 data from experiments with lead and sulfur beams can be well described

Is there a unique thermal source of dileptons in Pb(158 AGeV) + Au, Pb reactions?

An analysis of the dilepton measurements in the reactions Pb(158 A$\cdot$GeV) + Au, Pb points to a unique thermal source contributing to the invariant mass and transverse momentum spectra. Effects of the flow pattern are discussed.Comment: 7 LaTeX pages including eps figure

Energy loss of quarks in deconfined matter at RHIC: photon-tagged jets, single electron and dilepton spectra from open charm

We report a first attempt (i) to derive constraints on the energy loss of charm quarks in a deconfined medium from the recent PHENIX data of single-electron transverse momentum spectra and (ii) to estimate the resulting suppression of dileptons from correlated semi-leptonic decays of open charmed mesons. The momentum imbalance of photon-tagged light-quark jets is also considered.Comment: contribution to Quark Matter 2002, Nantes, France, July 18 - 24, 200

Dynamics of Quark-Gluon-Plasma Instabilities in Discretized Hard-Loop Approximation

Non-Abelian plasma instabilities have been proposed as a possible explanation for fast isotropization of the quark-gluon plasma produced in relativistic heavy-ion collisions. We study the real-time evolution of these instabilities in non-Abelian plasmas with a momentum-space anisotropy using a hard-loop effective theory that is discretized in the velocities of hard particles. We extend our previous results on the evolution of the most unstable modes, which are constant in directions transverse to the direction of anisotropy, from gauge group SU(2) to SU(3). We also present first full 3+1-dimensional simulation results based on velocity-discretized hard loops. In contrast to the effectively 1+1-dimensional transversely constant modes we find subexponential behaviour at late times.Comment: 30 pages, 16 figures. v3 typos fixe

In-medium spectral change of omega mesons as a probe of QCD four-quark condensate

Within QCD sum rules at finite baryon density we show the crucial role of four-quark condensates for the in-medium modification of the omega meson spectral function. In particular, such a global property as the sign of the in-medium omega meson mass shift is found to be governed by a parameter which describes the strength of the density dependence of the four-quark condensate beyond mean-field approximation. To study self-consistently the broadening of the omega meson resonance we employ a hadron spectral function based on the omega meson propagator delivered by an effective chiral Lagrangian. Measurements of the omega meson spectral change in heavy-ion collisions with the HADES detector can reveal the yet unknown density dependence of the four-quark condensate

Chromodynamic Weibel instabilities in relativistic nuclear collisions

Employing a previously derived formulation, and extending the treatment from purely transverse modes to wave vectors having a longitudinal component, we discuss the prospects for the occurrence of Weibel-type color-current filamentation in high-energy nuclear collisions. Numerical solutions of the dispersion equation for a number of scenarios relevant to RHIC and LHC suggest that modes with (predominantly transverse) wave numbers of several hundred MeV may become moderately agitated during the early collision stage. The emergence of filamentation helps to speed up the equilibration of the parton plasma and it may lead to non-statistical azimuthal patterns in the hadron final state.Comment: 11 pages, RevTex, 13 (e)ps files (revised for PRC

Electron and vibration structure of fluorine-containing polyamide film under high energetic electron irradiation

Influence of high energetic electron irradiation (Еᵢ = 1.8 МеV) on the electron and vibrational properties of fluorine containing polyamide films was studied. Nature of electron transitions and vibration bands in Raman and IR-absorption spectra in the initial state of the film was determined by quantum-chemical calculations. Results of optical absorption, Raman scattering and IR-absorption showed that irradiation of the film with dose of 1 MGy does not lead to significant changes of electron and vibrational structure. Increase of the dose to 3 MGy influences the intensity of vibration bands in Raman and IR-absorption spectra. Films that were transparent in the initial state became yellow-colored and fragile after the irradiation.Приведено дослідження впливу опромінення плівок фторвмісного поліаміду високоенергетичними електронами (Еᵢ = 1,8 МеВ) на його електронну та коливну структуру. За допомогою квантово-хімічних розрахунків встановлено природу електронних переходів та смуг КРС, а також ІЧ-поглинання у вихідному стані. Результати оптичного та ІЧ-поглинаннь, раманівського розсіяння світла показують, що дані плівки при дозі 1 МГр зберігають свою електронну та коливну структуру. Збільшення дози до 3 МГр призводить до зміни інтенсивностей коливних мод у спектрах раманівського розсіяння та ІЧ-поглинання. При даній дозі плівки втрачають прозорість, набуваючи жовтого кольору, і стають крихкими.Приведены исследования влияния облучения пленок фторсодержащего полиамида высокоэнергетическими электронами (Еᵢ = 1,8 МэВ) на его электронную и колебательную структуру. С помощью квантово-химических расчетов установлена природа электронных переходов и полос КРС, а также ИК-поглощения в исходном состоянии. Результаты оптического и ИК-поглощения, рамановского рассеяния света показывают, что данные пленки при дозе 1 МГр сохраняют свою электронную и колебательную структуру. Увеличение дозы до 3 МГр приводит к изменению интенсивностей колеблющихся мод в спектрах рамановского рассеяния и ИК-поглощения. При данной дозе пленки теряют прозрачность, приобретая желтый цвет, и становятся хрупкими

Irradiation-induced changes in vibration structure of films of squaraine dye

Influence of high energetic electron irradiation (Еₑ = 1.8 МеV) on the vibration properties of the squaraine dye film was studied. Quantum-chemical calculations were applied for determination of vibration bands in Raman spectra of the squaraine dye molecule. Results of Raman scattering of the film showed that its irradiation with dose of 1 MGy leads to shift of vibration bands positions by 2…6 cm⁻¹, appearance of background due to knocking of the atoms from the squaraine dye molecules. But all vibration modes at this dose are still present that points on possibility of functioning of the squaraine film in solar elements at this dose.Розглянуто вплив високоенергетичного електронного опромінення (Еₑ = 1,8 МеВ) на коливні властивості плівки зі сквараїнового барвника. За допомогою квантово-хімічних розрахунків встановлено коливні смуги у спектрі комбінаційного розсіяння світла молекули сквараїнового барвника. Результати комбінаційного розсіяння світла плівки показують, що її опромінення з дозою 1 МГр приводить до зсуву положень коливних мод на 2…6 cм⁻¹, появи радіаційного фону внаслідок вибивання атомів з каркасу молекул сквараїнових барвників. Проте, при цій дозі всі коливні моди зберігаються, що вказує на можливість функціонування сквараїнових плівок у сонячних елементах.Рассмотрено влияние высокоэнергетического электронного облучения (Еₑ = 1,8 МэВ) на колебательные свойства пленки из сквараинового красителя. С помощью квантово-химических расчетов определены колебательные полосы в спектре комбинационного рассеяния света молекулы сквараинового красителя. Результаты комбинационного рассеяния света пленки показали, что облучение с дозой 1 MГр приводит к смещению положений колебательных мод на 2…6 cм⁻¹, появлению радиационного фона вследствие выбивания атомов с каркаса молекул сквараиновых красителей. Но при данной дозе все колебания сохраняются, что указывает на возможность функционирования сквараиновых пленок в солнечных элементах

Dileptons, Charm and Bottom in Relativistic Heavy-Ion Collisions

The relation of the thermal dilepton signal from deconfined matter, resulting in central ultra-relativistic heavy-ion collisions at RHIC and LHC energies, to the background yields from the Drell-Yan process and correlated semileptonic decays of open charm and bottom mesons is analyzed. We demonstrate that very stringent kinematical cuts offer a chance to identify the thermal signal in the continuum region.Comment: 8 LaTeX pages including eps figures, contribution to the Erice School on Nuclear Physics 1998 (to be published in "Progress in Particle and Nuclear Physics"