Finite-Size Effects and Scaling for the Thermal QCD Deconfinement Phase Transition within the Exact Color-Singlet Partition Function

We study the finite-size effects for the thermal QCD Deconfinement Phase Transition (DPT), and use a numerical finite size scaling analysis to extract the scaling exponents characterizing its scaling behavior when approaching the thermodynamic limit. For this, we use a simple model of coexistence of hadronic gas and color-singlet Quark Gluon Plasma (QGP) phases in a finite volume. The Color-Singlet Partition Function (CSPF) of the QGP cannot be exactly calculated and is usually derived within the saddle point approximation. When we try to do calculations with such an approximate CSPF, a problem arises in the limit of small temperatures and/or volumes (VT3<<1), requiring then additional approximations if we want to carry out calculations. We propose in this work a new method for an accurate calculation of any quantity of the finite system, without explicitly calculating the CSPF itself and without any approximation. By probing the behavior of some useful thermodynamic response functions on the hole range of temperature, it turns out that in a finite size system, all singularities in the thermodynamic limit are smeared out and the transition point is shifted away. A numerical finite size scaling analysis of the obtained data allows us to determine the scaling exponents of the QCD DPT. Our results expressing the equality between their values and the space dimensionality is a consequence of the singularity characterizing a first order phase transition and agree very well with the predictions of other FSS theoretical approaches and with the results of both lattice QCD and Monte Carlo models calculations.Comment: 09 pages, 11 Postscript figure

Three-party qutrit-state sharing

A three-party scheme for securely sharing an arbitrary unknown single-qutrit state is presented. Using a general Greenberger-Horne-Zeilinger (GHZ) state as the quantum channel among the three parties, the quantum information (i.e., the qutrit state) from the sender can be split in such a way that the information can be recovered if and only if both receivers collaborate. Moreover, the generation of the scheme to multi-party case is also sketched.Comment: 7 page

Relationship between structural changes, hydrogen content and annealing in stacks of ultrathin Si/Ge amorphous layers

Amorphous Si, Ge and SiGe alloys are often doped with H in order to passivate the dangling bonds. However, H is not stable against light soaking and heat treatments yielding degradation of the electrical-optical properties. We present results on the structural instability, as a function of annealing, caused by H in multilayers (MLs) of alternating 3 nm thick a-Si and a-Ge layers deposited by sputtering. H was added at flow rates of 0.4, 0.8, 1.5, 3 and 6 ml/min. By ERDA it was seen that for flow rates &#8805;1.5 ml/min the effective H content incorporated in the samples saturates at &#8764;16 at. %. IR optical absorbance shows that mostly Si and Ge monohydrides form. Annealing was done at 673 K for times of 1 to 10 h. The evolution of the properties of the MLs as a function of annealing and H content was followed by IR optical absorbance, TEM, AFM, ERDA. With increasing annealing time/temperature and H content the surface morphology degrades with formation of bubbles and craters whose size and density increase up to 9 &#956;m and 6.7x105 cm-2 for a H flow rate of 6 ml/min. The signal of Ge-H and Si-H complexes almost completely vanish in the IR absorbance spectra upon annealing indicating that H is released to the lattice. This supports the conclusion that it is the released H that produces the bubbles and the craters when the H bubbles blow up because of a too high internal pressure. ERDA experiments performed on single layers of a-Si and a-Ge, showing a faster H released from a-Si than from a-Ge, and energy filtered TEM (EFTEM) maps, showing larger broadening of the a-Si layers in the ML structure, suggest that upon annealing H is first released from a-Si layers. This is in agreement with published data reporting on the lower binding energy of Si-H with respect to Ge-H in amorphous materials

Near-threshold production of omega mesons in the pn -> d omega reaction

The first measurement of the p n -> d omega total cross section has been achieved at mean excess energies of Q = 28 and 57 MeV by using a deuterium cluster-jet target. The momentum of the fast deuteron was measured in the ANKE spectrometer at COSY-Juelich and that of the slow "spectator" proton p(sp) from the p d -> p(sp) d omega reaction in a silicon telescope placed close to the target. The cross sections lie above those measured for p p -> p p omega but seem to be below theoretical predictions.Comment: 7 pages, 8 figures; second approach to describe the background has been added; results changed insignificantly, EPJ in pres

Proton driver optimization for new generation neutrino superbeams to search for sub-leading numu->nue oscillations (θ13\theta_{13} angle)

We perform a systematic study of particle production and neutrino yields for different incident proton energies $E_p$ and baselines $L$, with the aim of optimizing the parameters of a neutrino beam for the investigation of $\theta_{13}$-driven neutrino oscillations in the $\Delta m^2$ range allowed by Superkamiokande results. We study the neutrino energy spectra in the ``relevant'' region of the first maximum of the oscillation at a given baseline $L$. We find that to each baseline $L$ corresponds an ``optimal'' proton energy $E_p$ which minimizes the required integrated proton intensity needed to observe a fixed number of oscillated events. In addition, we find that the neutrino event rate in the relevant region scales approximately linearly with the proton energy. Hence, baselines $L$ and proton energies $E_p$ can be adjusted and the performance for neutrino oscillation searches will remain approximately unchanged provided that the product of the proton energy times the number of protons on target remains constant. We apply these ideas to the specific cases of 2.2, 4.4, 20, 50 and 400 GeV protons. We simulate focusing systems that are designed to best capture the secondary pions of the ``optimal'' energy. We compute the expected sensitivities to $\sin^22\theta_{13}$ for the various configurations by assuming the existence of new generation accelerators able to deliver integrated proton intensities on target times the proton energy of the order of ${\cal O}(5\times 10^{23})\rm\ GeV\times\rm pot/year$.Comment: 39 pages, 17 figure

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