Revisiting the holographic dark energy in a non-flat universe: alternative model and cosmological parameter constraintsZhang, Jing-Fei;Zhao, Ming-Ming;Cui, Jing-Lei;Zhang, Xin
doi: 10.1140/epjc/s10052-014-3178-7pmid: N/A
Abstract We propose an alternative model for the holographic dark energy in a non-flat universe. This new model differs from the previous one in that the IR length cutoff \(L\) is taken to be exactly the event horizon size in a non-flat universe, which is more natural and theoretically/conceptually concordant with the model of holographic dark energy in a flat universe. We constrain the model using the recent observational data including the type Ia supernova data from SNLS3, the baryon acoustic oscillation data from 6dF, SDSS-DR7, BOSS-DR11, and WiggleZ, the cosmic microwave background data from Planck, and the Hubble constant measurement from HST. In particular, since some previous studies have shown that the color–luminosity parameter \(\beta \) of supernovae is likely to vary during the cosmic evolution, we also consider such a case that \(\beta \) in SNLS3 is time-varying in our data fitting. Compared to the constant \(\beta \) case, the time-varying \(\beta \) case reduces the value of \(\chi ^2\) by about 35 and results in that \(\beta \) deviates from a constant at about 5\(\sigma \) level, well consistent with the previous studies. For the parameter \(c\) of the holographic dark energy, the constant \(\beta \) fit gives \(c=0.65\pm 0.05\) and the time-varying \(\beta \) fit yields \(c=0.72\pm 0.06\). In addition, an open universe is favored (at about 2\(\sigma \)) for the model by the current data. A preprint version of the article is available at ArXiv.
Conserved charges of black holes in Weyl and Einstein–Gauss–Bonnet gravitiesPeng, Jun-Jin
doi: 10.1140/epjc/s10052-014-3156-0pmid: N/A
Abstract An off-shell generalization of the Abbott–Deser–Tekin (ADT) conserved charge was recently proposed by Kim et al. They achieved this by introducing off-shell Noether currents and potentials. In this paper, we construct the crucial off-shell Noether current by the variation of the Bianchi identity for the expression of EOM, with the help of the property of Killing vector. Our Noether current, which contains an additional term that is just one half of the Lie derivative of a surface term with respect to the Killing vector, takes a different form in comparison with the one in their work. Then we employ the generalized formulation to calculate the quasi-local conserved charges for the most general charged spherically symmetric and the dyonic rotating black holes with AdS asymptotics in four-dimensional conformal Weyl gravity, as well as the charged spherically symmetric black holes in arbitrary dimensional Einstein–Gauss–Bonnet gravity coupled to Maxwell or nonlinear electrodynamics in AdS spacetime. Our results confirm those obtained through other methods in the literature. A preprint version of the article is available at ArXiv.
A flexible scintillation light apparatus for rare event searchesBonvicini, V.;Capelli, S.;Cremonesi, O.;Cucciati, G.;Gironi, L.;Pavan, M.;Previtali, E.;Sisti, M.
doi: 10.1140/epjc/s10052-014-3151-5pmid: N/A
Abstract Compelling experimental evidences of neutrino oscillations and their implication that neutrinos are massive particles have given neutrinoless double beta decay (\(\beta \beta 0\nu \)) a central role in astroparticle physics. In fact, the discovery of this elusive decay would be a major breakthrough, unveiling that neutrino and antineutrino are the same particle and that the lepton number is not conserved. It would also impact our efforts to establish the absolute neutrino mass scale and, ultimately, understand elementary particle interaction unification. All current experimental programs to search for \(\beta \beta 0\nu \) are facing with the technical and financial challenge of increasing the experimental mass while maintaining incredibly low levels of spurious background. The new concept described in this paper could be the answer which combines all the features of an ideal experiment: energy resolution, low cost mass scalability, isotope choice flexibility and many powerful handles to make the background negligible. The proposed technology is based on the use of arrays of silicon detectors cooled to 120 K to optimize the collection of the scintillation light emitted by ultra-pure crystals. It is shown that with a 54 kg array of natural CaMoO\(_4\) scintillation detectors of this type it is possible to yield a competitive sensitivity on the half-life of the \(\beta \beta 0\nu \) of \(^{100}\)Mo as high as \(\sim \) \(10^{24}\) years in only 1 year of data taking. The same array made of \(^{40}\)Ca\(^{\mathrm {nat}}\)MoO\(_4\) scintillation detectors (to get rid of the continuous background coming from the two neutrino double beta decay of \(^{48}\)Ca) will instead be capable of achieving the remarkable sensitivity of \(\sim \) \(10^{25}\) years on the half-life of \(^{100}\)Mo \(\beta \beta 0\nu \) in only 1 year of measurement. A preprint version of the article is available at ArXiv.
Three-dimensional photograph of electron tracks through a plastic scintillatorFilipenko, Mykhaylo;Iskhakov, Timur;Hufschmidt, Patrick;Anton, Gisela;Campbell, Michael;Gleixner, Thomas;Leuchs, Gerd;Tick, Timo;Vallerga, John;Wagenpfeil, Michael;Michel, Thilo
doi: 10.1140/epjc/s10052-014-3131-9pmid: N/A
Abstract The reconstruction of particle trajectories makes it possible to distinguish between different types of charged particles. In high-energy physics, where trajectories are rather long (several meters), large size trackers must be used to achieve sufficient position resolution. However, in low-background experiments like the search for neutrinoless double beta decay, tracks are rather short (some mm to several cm, depending on the detector in use) and three-dimensional trajectories could only be resolved in gaseous time-projection chambers so far. For detectors of a large volume of around one cubic meter (large in the scope of neutrinoless double beta search) and therefore large drift distances (several decimeters to 1 m), this technique is limited by diffusion and repulsion of charge carriers. In this work we present a “proof-of-principle” experiment for a new method of the three-dimensional tracking of charged particles by scintillation light: we used a setup consisting of a scintillator, mirrors, lenses, and a novel imaging device (the hybrid photon detector) in order to image two projections of electron tracks through the scintillator. We took data at the T-22 beamline at DESY with relativistic electrons with a kinetic energy of 5 GeV and from this data successfully reconstructed their three-dimensional propagation path in the scintillator. With our setup we achieved a position resolution in the range of 170–248 µm. A preprint version of the article is available at ArXiv.
Angular distribution and forward–backward asymmetry of the Higgs-boson decay to photon and lepton pairKorchin, Alexander Yu.;Kovalchuk, Vladimir A.
doi: 10.1140/epjc/s10052-014-3141-7pmid: N/A
Abstract The Higgs-boson decay \(h \rightarrow \gamma \ell ^+ \ell ^-\) for various lepton states \(\ell = (e, \, \mu , \, \tau )\) is analyzed. The differential decay width and forward–backward asymmetry are calculated as functions of the dilepton invariant mass in a model where the Higgs boson interacts with leptons and quarks via a mixture of scalar and pseudoscalar couplings. These couplings are partly constrained from data on the decays to leptons, \(h \rightarrow \ell ^+ \ell ^-\), and quarks \(h \rightarrow q \bar{q} \) (where \(q = (c, \, b)\)), while the Higgs couplings to the top quark are chosen from the two-photon and two-gluon decay rates. Nonzero values of the forward–backward asymmetry will manifest effects of new physics in the Higgs sector. The decay width and asymmetry integrated over the dilepton invariant mass are also presented. A preprint version of the article is available at ArXiv.
Holographic superconductors in a rotating spacetimeLin, Kai;Abdalla, E.
doi: 10.1140/epjc/s10052-014-3144-4pmid: N/A
Abstract We consider holographic superconductors in a rotating black string spacetime. In view of the mandatory introduction of the \(A_\varphi \) component of the vector potential we are left with three equations to be solved. Their solutions show that the rotation parameter \(a\) influences the critical temperature \(T_\mathrm{c}\) and the conductivity \(\sigma \) in a simple but non-trivial way. A preprint version of the article is available at ArXiv.
Quasinormal modes of Lovelock black holesPrasobh, C. B.;Kuriakose, V. C.
doi: 10.1140/epjc/s10052-014-3136-4pmid: N/A
Abstract The quasinormal modes of metric perturbations in asymptotically flat black hole spacetimes in the Lovelock model are calculated for different spacetime dimensions and higher orders of curvature. It is analytically established that in the asymptotic limit \(l\rightarrow \infty \), the imaginary parts of the quasinormal frequencies become constant for tensor, scalar as well as vector perturbations. Numerical calculation shows that this indeed is the case. Also, the real and imaginary parts of the quasinormal modes are seen to increase as the order of the theory \(k\) increases. The real part of the modes decreases as the spacetime dimension \(d\) increases, indicating the presence of lower frequency modes in higher dimensions. Also, it is seen that the modes are roughly isospectral at very high values of the spacetime dimension \(d\). A preprint version of the article is available at ArXiv.
Electroweak radiative corrections to $$W^+W^-\gamma $$ W + ...Chen, Chong;Ma, Wen-Gan;Zhang, Ren-You;Zhang, Yu;Chen, Liang-Wen;Guo, Lei
doi: 10.1140/epjc/s10052-014-3166-ypmid: N/A
Abstract We provide and discuss the precision predictions for the \(W^+W^-\gamma \) production at the ILC including the full electroweak (EW) one-loop corrections and high order initial state radiation (ISR) contributions in the standard model. The dependence of the leading order (LO) and EW corrected cross sections on the colliding energy is investigated. We find that the EW correction suppresses the LO cross section significantly, and the ISR effect beyond \({\mathcal O}(\alpha )\) is important near the threshold, but it is negligible in the high energy region. We provide the LO and EW corrected distributions of the transverse momenta and rapidities of final \(W^-\)-boson and photon as well as the \(W\)-pair invariant mass. From the various kinematic distributions, we find that the EW correction strongly depends on the final state phase space. We investigate the leptonic decays of the final W-boson pair by adopting the narrow width approximation, and we find that the final produced photon and leptons can be well separated from each other. A preprint version of the article is available at ArXiv.