Advances in High Energy Physics
[SJR: 1.334] [H-I: 12] [13 followers] Follow
Open Access journal
ISSN (Print) 1687-7357 - ISSN (Online) 1687-7365
Published by Hindawi Publishing Corporation [403 journals]
- Quasi-Normal Modes: The “Electrons” of Black Holes as
“Gravitational Atoms”' Implications for the Black Hole
Abstract: Some recent important results on black hole (BH) quantum physics concerning the BH effective state and the natural correspondence between Hawking radiation and BH quasi-normal modes (QNMs) are reviewed, clarified, and refined. Such a correspondence permits one to naturally interpret QNMs as quantum levels in a semiclassical model. This is a model of BH somewhat similar to the historical semiclassical model of the structure of a hydrogen atom introduced by Bohr in 1913. In a certain sense, QNMs represent the “electron” which jumps from a level to another one and the absolute values of the QNMs frequencies, “triggered” by emissions (Hawking radiation) and absorption of particles, represent the energy “shells” of the “gravitational hydrogen atom.” Important consequences on the BH information puzzle are discussed. In fact, it is shown that the time evolution of this “Bohr-like BH model” obeys a time dependent Schrödinger equation which permits the final BH state to be a pure quantum state instead of a mixed one. Thus, information comes out in BH evaporation in agreement with the assumption by ’t Hooft that Schröedinger equations can be used universally for all dynamics in the universe. We also show that, in addition, our approach solves the entanglement problem connected with the information paradox.
PubDate: Tue, 19 May 2015 10:14:28 +000
- A Study of Transverse Momentum Distributions of Jets Produced in -, -,
-Au, Au-Au, and Pb-Pb Collisions at High Energies
Abstract: The transverse momentum distributions of jets produced in -, -, -Au, Au-Au, and Pb-Pb collisions at high energies with different selected conditions are analyzed by using a multisource thermal model. The multicomponent (mostly two-component) Erlang distribution used in our description is in good agreement with the experimental data measured by the STAR, D0, CDF II, ALICE, ATLAS, and CMS Collaborations. Related parameters are extracted from the transverse momentum distributions and some information on different interacting systems is obtained. In the two-component Erlang distribution, the first component has usually two or more sources which are contributed by strong scattering interactions between two quarks or more quarks and gluons, while the second component has mostly two sources which are contributed by harder head-on scattering between two quarks.
PubDate: Tue, 19 May 2015 09:01:49 +000
- Effect of Generalized Uncertainty Principle on Main-Sequence Stars and
Abstract: This paper addresses the effect of generalized uncertainty principle, emerged from different approaches of quantum gravity within Planck scale, on thermodynamic properties of photon, nonrelativistic ideal gases, and degenerate fermions. A modification in pressure, particle number, and energy density are calculated. Astrophysical objects such as main-sequence stars and white dwarfs are examined and discussed as an application. A modification in Lane-Emden equation due to a change in a polytropic relation caused by the presence of quantum gravity is investigated. The applicable range of quantum gravity parameters is estimated. The bounds in the perturbed parameters are relatively large but they may be considered reasonable values in the astrophysical regime.
PubDate: Mon, 18 May 2015 13:11:59 +000
- Neutrino Physics in the Frontiers of Intensities and Very High
PubDate: Sun, 17 May 2015 13:20:51 +000
- High Energy Neutrino Emission from Astrophysical Jets in the Galaxy
Abstract: We address simulated neutrino emission originated from astrophysical jets of compact objects within the Galaxy. These neutrinos are of high energies ( of the order up to a few TeV) and for their observation specialized instruments are in operation, both on Earth and in orbit. Furthermore, some next generation telescopes and detector facilities are in the process of design and construction. The jet flow simulations are performed using the modern PLUTO hydrocode in its relativistic magnetohydrodynamic version. One of the main ingredients of the present work is the presence of a toroidal magnetic field that confines the jet flow and furthermore greatly affects the distribution of the high energy neutrinos.
PubDate: Thu, 14 May 2015 14:15:26 +000
- Null Geodesics and Strong Field Gravitational Lensing in a String Cloud
Abstract: This paper is devoted to studying two interesting issues of a black hole with string cloud background. Firstly, we investigate null geodesics and find unstable orbital motion of particles. Secondly, we calculate deflection angle in strong field limit. We then find positions, magnifications, and observables of relativistic images for supermassive black hole at the galactic center. We conclude that string parameter highly affects the lensing process and results turn out to be quite different from the Schwarzschild black hole.
PubDate: Thu, 14 May 2015 11:41:20 +000
- HepSim: A Repository with Predictions for High-Energy Physics Experiments
Abstract: A file repository for calculations of cross sections and kinematic distributions using Monte Carlo generators for high-energy collisions is discussed. The repository is used to facilitate effective preservation and archiving of data from theoretical calculations and for comparisons with experimental data. The HepSim data library is publicly accessible and includes a number of Monte Carlo event samples with Standard Model predictions for current and future experiments. The HepSim project includes a software package to automate the process of downloading and viewing online Monte Carlo event samples. Data streaming over a network for end-user analysis is discussed.
PubDate: Thu, 14 May 2015 05:55:44 +000
- Electron Capture Cross Sections for Stellar Nucleosynthesis
Abstract: In the first stage of this work, we perform detailed calculations for the cross sections of the electron capture on nuclei under laboratory conditions. Towards this aim we exploit the advantages of a refined version of the proton-neutron quasiparticle random-phase approximation (pn-QRPA) and carry out state-by-state evaluations of the rates of exclusive processes that lead to any of the accessible transitions within the chosen model space. In the second stage of our present study, we translate the abovementioned -capture cross sections to the stellar environment ones by inserting the temperature dependence through a Maxwell-Boltzmann distribution describing the stellar electron gas. As a concrete nuclear target we use the 66Zn isotope, which belongs to the iron group nuclei and plays prominent role in stellar nucleosynthesis at core collapse supernovae environment.
PubDate: Wed, 13 May 2015 14:27:10 +000
- Asymmetric Velocity Distributions from Halo Density Profiles in the
Abstract: We show how to obtain the energy distribution f(E) in our vicinity starting from WIMP density profiles in a self-consistent way by employing the Eddington approach and adding reasonable angular momentum dependent terms in the expression of the energy. We then show how we can obtain the velocity dispersions and the asymmetry parameter β in terms of the parameters describing the angular momentum dependence. From this expression, for f(E), we proceed to construct an axially symmetric WIMP a velocity distribution, which, for a gravitationally bound system, automatically has a velocity upper bound and is characterized by the same asymmetriy β. This approach is tested and clarified by constructing analytic expressions in a simple model, with adequate structure. We then show how such velocity distributions can be used in determining the event rates, including modulation, in both the standard and the directional WIMP searches.
PubDate: Wed, 13 May 2015 07:47:42 +000
- Standard and Nonstandard Neutrino-Nucleus Reactions Cross Sections and
Event Rates to Neutrino Detection Experiments
Abstract: In this work, we explore -nucleus processes from a nuclear theory point of view and obtain results with high confidence level based on accurate nuclear structure cross sections calculations. Besides cross sections, the present study includes simulated signals expected to be recorded by nuclear detectors and differential event rates as well as total number of events predicted to be measured. Our original cross sections calculations are focused on measurable rates for the standard model process, but we also perform calculations for various channels of the nonstandard neutrino-nucleus reactions and come out with promising results within the current upper limits of the corresponding exotic parameters. We concentrate on the possibility of detecting (i) supernova neutrinos by using massive detectors like those of the GERDA and SuperCDMS dark matter experiments and (ii) laboratory neutrinos produced near the spallation neutron source facilities (at Oak Ridge National Lab) by the COHERENT experiment. Our nuclear calculations take advantage of the relevant experimental sensitivity and employ the severe bounds extracted for the exotic parameters entering the Lagrangians of various particle physics models and specifically those resulting from the charged lepton flavour violating experiments (Mu2e and COMET experiments).
PubDate: Wed, 13 May 2015 07:03:02 +000
- A CaMoO4 Crystal Low Temperature Detector for the AMoRE Neutrinoless
Double Beta Decay Search
Abstract: We report the development of a CaMoO4 crystal low temperature detector for the AMoRE neutrinoless double beta decay search experiment. The prototype detector cell was composed of a 216 g CaMoO4 crystal and a metallic magnetic calorimeter. An overground measurement demonstrated FWHM resolution of 6–11 keV for full absorption gamma peaks. Pulse shape discrimination was clearly demonstrated in the phonon signals, and 7.6 of discrimination power was found for the and separation. The phonon signals showed rise-times of about 1 ms. It is expected that the relatively fast rise-time will increase the rejection efficiency of two-neutrino double beta decay pile-up events which can be one of the major background sources in searches.
PubDate: Tue, 12 May 2015 12:56:33 +000
- Convoluted -Signals on 114Cd Isotope from Astrophysical and Laboratory
Abstract: At first, we evaluate scattering cross sections of low, and intermediate-energy neutrinos scattered off the 114 Cd isotope, the most abundant Cd isotope present also in the COBRA detector (CdTe and CdZnTe materials) which aims to search for double beta decay events and neutrino observations at Gran Sasso laboratory (LNGS). The coherent -nucleus channel addressed here is the dominant reaction channel of the neutral current -nucleus scattering. Our -nucleus cross sections (calculated with a refinement of the quasiparticle random-phase approximation, QRPA) refer to the transitions for -energies MeV. Subsequently, simulated -signals on 114 Cd isotope are derived. Towards this purpose, the required folded cross section comes out of simulation techniques by employing several low, and intermediate-energy neutrino distributions of the astrophysical -sources, like the solar, supernova, and Earth neutrinos, as well as the laboratory neutrinos, the reactor neutrinos, the pion-muon stopped neutrinos, and the β-beam neutrinos.
PubDate: Tue, 12 May 2015 08:52:57 +000
- Vacuum Expectation Value Profiles of the Bulk Scalar Field in the
Generalized Randall-Sundrum Model
Abstract: In the generalized Randall-Sundrum warped brane-world model the cosmological constant induced on the visible brane can be positive or negative. In this paper we investigate profiles of vacuum expectation value of the bulk scalar field under general Dirichlet and Neumann boundary conditions in the generalized warped brane-world model. We show that the VEV profiles generally depend on the value of the brane cosmological constant. We find that the VEV profiles of the bulk scalar field for a visible brane with negative cosmological constant and positive tension are quite distinct from those of Randall-Sundrum model. In addition we show that the VEV profiles for a visible brane with large positive cosmological constant are also different from those of the Randall-Sundrum model. We also verify that Goldberger and Wise mechanism can work under nonzero Dirichlet boundary conditions in the generalized Randall-Sundrum model.
PubDate: Tue, 28 Apr 2015 06:21:55 +000
- Is the Free Vacuum Energy Infinite'
Abstract: Considering the fundamental cutoff applied by the uncertainty relations’ limit on virtual particles’ frequency in the quantum vacuum, it is shown that the vacuum energy density is proportional to the inverse of the fourth power of the dimensional distance of the space under consideration and thus the corresponding vacuum energy automatically regularized to zero value for an infinitely large free space. This can be used in regularizing a number of unwanted infinities that happen in the Casimir effect, the cosmological constant problem, and so on without using already known mathematical (not so reasonable) techniques and tricks.
PubDate: Mon, 27 Apr 2015 12:57:18 +000
- Balance Function in High-Energy Collisions
Abstract: Aspects and implications of the balance functions (BF) in high-energy physics are reviewed. The various calculations and measurements depending on different quantities, for example, system size, collisions centrality, and beam energy, are discussed. First, the different definitions including advantages and even short-comings are highlighted. It is found that BF, which are mainly presented in terms of relative rapidity, and relative azimuthal and invariant relative momentum, are sensitive to the interaction centrality but not to the beam energy and can be used in estimating the hadronization time and the hadron-quark phase transition. Furthermore, the quark chemistry can be determined. The chemical evolution of the new-state-of-matter, the quark-gluon plasma, and its temporal-spatial evolution, femtoscopy of two-particle correlations, are accessible. The production time of positive-negative pair of charges can be determined from the widths of BF. Due to the reduction in the diffusion time, narrowed widths refer to delayed hadronization. It is concluded that BF are powerful tools characterizing hadron-quark phase transition and estimating some essential properties.
PubDate: Thu, 23 Apr 2015 10:44:37 +000
- Quantum Probes of Timelike Naked Singularities in -Dimensional Power-Law
Abstract: The formation of naked singularities in -dimensional power-law spacetimes in linear Einstein-Maxwell and Einstein-scalar theories sourced by azimuthally symmetric electric field and a self-interacting real scalar field, respectively, are considered in view of quantum mechanics. Quantum test fields obeying the Klein-Gordon and Dirac equations are used to probe the classical timelike naked singularities developed at . We show that when the classically singular spacetimes probed with scalar waves, the considered spacetimes remain singular. However, the spinorial wave probe of the singularity in the metric of a self-interacting real scalar field remains quantum regular. The notable outcome in this study is that the quantum regularity/singularity cannot be associated with the energy conditions.
PubDate: Sun, 19 Apr 2015 17:00:27 +000
- Will There Be Future Deceleration' A Study of Particle Creation
Mechanism in Nonequilibrium Thermodynamics
Abstract: The paper deals with nonequilibrium thermodynamics based on adiabatic particle creation mechanism with the motivation of considering it as an alternative choice to explain the recent observed accelerating phase of the universe. Using Friedmann’s equations, it is shown that the deceleration parameter () can be obtained from the knowledge of the particle production rate (). Motivated by thermodynamical point of view, cosmological solutions are evaluated for the particle creation rates in three cosmic phases, namely, inflation, matter dominated era, and present late time acceleration. The deceleration parameter () is expressed as a function of the redshift parameter (), and its variation is presented graphically. Also, statefinder analysis has been presented graphically in three different phases of the universe. Finally, two noninteracting fluids with different particle creation rates are considered as cosmic substratum, and deceleration parameter () is evaluated. Whether more than one transition of is possible or not is examined by graphical representations.
PubDate: Wed, 08 Apr 2015 06:15:04 +000
- Decays with the QCD Factorization Approach
Abstract: We studied the nonleptonic , decays with the QCD factorization approach. It is found that the Cabibbo favored processes of , , are the promising decay channels with branching ratio larger than 1%, which should be observed earlier by the LHCb collaboration.
PubDate: Sun, 05 Apr 2015 15:58:41 +000
- Global Properties in High Energy Collisions
PubDate: Thu, 26 Mar 2015 06:40:52 +000
- Transverse Momentum Distributions of Hadrons Produced in Pb-Pb Collisions
at LHC Energy TeV
Abstract: The transverse momentum spectra of several types of hadrons, , , , , , , , , , and produced in most central Pb-Pb collisions at LHC energy TeV have been studied at midrapidity () using an earlier proposed unified statistical thermal freeze-out model. The calculated results are found to be in good agreement with the experimental data measured by the ALICE experiment at LHC. The model calculation fits provide the thermal freeze-out conditions in terms of the temperature and collective flow effect parameters for different particle species. Interestingly the model parameter fits to the experimental data reveal stronger collective flow in the system and lesser freeze-out temperatures of the different particle species as compared to Au-Au collisions at RHIC. The strong increase of the collective flow appears to be a consequence of the increasing particle density at LHC. The model used incorporates a longitudinal as well as transverse hydrodynamic flow. The chemical potential has been assumed to be nearly equal to zero for the bulk of the matter owing to high degree of nuclear transparency effect at such collision energies. The contributions from heavier decay resonances are also taken into account.
PubDate: Wed, 25 Mar 2015 12:35:10 +000
- Search for Long-Range Correlations in Relativistic Heavy-Ion Collisions at
Abstract: Long-range correlations are searched for by analysing the experimental data on 16O-AgBr and 32S-AgBr collisions at 200 A GeV/c and the results are compared with the predictions of a multi phase transport (AMPT) model. The findings reveal that the observed forward-backward (F-B) multiplicity correlations are mainly of short range in nature. The range of F-B correlations are observed to extend with increasing projectile mass. The observed extended range of F-B correlations might be due to overall multiplicity fluctuations arising because of nuclear geometry. The findings are not sufficient for making any definite conclusions regarding the presence of long-range correlations.
PubDate: Wed, 25 Mar 2015 12:18:55 +000
- Tsallis Statistical Interpretation of Transverse Momentum Spectra in
High-Energy pA Collisions
Abstract: In Tsallis statistics, we investigate charged pion and proton production for pCu and pPb interactions at 3, 8, and 15 GeV/c. Two versions of Tsallis distribution are implemented in a multisource thermal model. A comparison with experimental data of the HARP-CDP group shows that they both can reproduce the transverse momentum spectra, but the improved form gives a better description. It is also found that the difference between q and q′ is small when the temperature T = T′ for the same incident momentum and angular interval, and the value of q is greater than q′ in most cases.
PubDate: Wed, 25 Mar 2015 11:16:53 +000
- Charged Particle, Photon Multiplicity, and Transverse Energy Production in
High-Energy Heavy-Ion Collisions
Abstract: We review the charged particle and photon multiplicities and transverse energy production in heavy-ion collisions starting from few GeV to TeV energies. The experimental results of pseudorapidity distribution of charged particles and photons at different collision energies and centralities are discussed. We also discuss the hypothesis of limiting fragmentation and expansion dynamics using the Landau hydrodynamics and the underlying physics. Meanwhile, we present the estimation of initial energy density multiplied with formation time as a function of different collision energies and centralities. In the end, the transverse energy per charged particle in connection with the chemical freeze-out criteria is discussed. We invoke various models and phenomenological arguments to interpret and characterize the fireball created in heavy-ion collisions. This review overall provides a scope to understand the heavy-ion collision data and a possible formation of a deconfined phase of partons via the global observables like charged particles, photons, and the transverse energy measurement.
PubDate: Wed, 25 Mar 2015 08:45:54 +000
- On Extraction of Chemical Potentials of Quarks from Particle Transverse
Momentum Spectra in High Energy Collisions
Abstract: We present two methods to extract the chemical potentials of quarks in high energy collisions. The first method is based on the ratios of negatively/positively charged particles, and the temperatures extracted from the transverse momentum spectra of related hadrons are needed. The second method is based on the chemical potentials of some particles, and we also need the transverse momentum spectra of related hadrons. To extract the quark chemical potentials, we would like to propose experimental collaborations to measure simultaneously not only the transverse momentum spectra of , , , , , and , but also those of , , , and (even those of , , and ) in high energy nuclear collisions.
PubDate: Wed, 25 Mar 2015 08:19:30 +000
- Axially Symmetric-dS Solution in Teleparallel Gravity Theories
Abstract: We apply a tetrad field with six unknown functions to Einstein field equations. Exact vacuum solution, which represents axially symmetric-dS spacetime, is derived. We multiply the tetrad field of the derived solution by a local Lorentz transformation which involves a generalization of the angle and get a new tetrad field. Using this tetrad, we get a differential equation from the scalar torsion . Solving this differential equation we obtain a solution to the gravity theories under certain conditions on the form of and its first derivatives. Finally, we calculate the scalars of Riemann Christoffel tensor, Ricci tensor, Ricci scalar, torsion tensor, and its contraction to explain the singularities associated with this solution.
PubDate: Tue, 24 Mar 2015 13:41:00 +000
- Coupled Scalar Fields Oscillons and Breathers in Some Lorentz Violating
Abstract: We discuss the impact of the breaking of the Lorentz symmetry on the usual oscillons, the so-called flat-top oscillons, and the breathers. Our analysis is performed by using a Lorentz violation scenario rigorously derived in the literature. We show that the Lorentz violation is responsible for the origin of a kind of deformation of the configuration, where the field configuration becomes oscillatory in a localized region near its maximum value. Furthermore, we show that the Lorentz breaking symmetry produces a displacement of the oscillon along the spatial direction; the same feature is present in the case of breathers. We also show that the effect of a Lorentz violation in the flat-top oscillon solution is responsible by the shrinking of the flat-top. Furthermore, we find analytically the outgoing radiation; this result indicates that the amplitude of the outgoing radiation is controlled by the Lorentz breaking parameter, in such a way that this oscillon becomes more unstable than its symmetric counterpart; however, it still has a long living nature.
PubDate: Wed, 18 Mar 2015 10:10:57 +000
- Analytical Calculation of Stored Electrostatic Energy per Unit Length for
an Infinite Charged Line and an Infinitely Long Cylinder in the Framework
of Born-Infeld Electrostatics
Abstract: More than 80 years ago, Born-Infeld electrodynamics was proposed in order to remove the point charge singularity in Maxwell electrodynamics. In this work, after a brief introduction to Lagrangian formulation of Abelian Born-Infeld model in the presence of an external source, we obtain the explicit forms of Gauss’s law and the energy density of an electrostatic field for Born-Infeld electrostatics. The electric field and the stored electrostatic energy per unit length for an infinite charged line and an infinitely long cylinder in Born-Infeld electrostatics are calculated. Numerical estimations in this paper show that the nonlinear corrections to Maxwell electrodynamics are considerable only for strong electric fields. We present an action functional for Abelian Born-Infeld model with an auxiliary scalar field in the presence of an external source. This action functional is a generalization of the action functional which was presented by Tseytlin in his studies on low energy dynamics of D-branes (Nucl. Phys. B469, 51 (1996); Int. J. Mod. Phys. A 19, 3427 (2004)). Finally, we derive the symmetric energy-momentum tensor for Abelian Born-Infeld model with an auxiliary scalar field.
PubDate: Tue, 17 Mar 2015 13:43:35 +000
- The Quantum Effects Role on Weibel Instability Growth Rate in Dense Plasma
Abstract: The Weibel instability is one of the basic plasma instabilities that plays an important role in stopping the hot electrons and energy deposition mechanism. In this paper, combined effect of the density gradient and quantum effects on Weibel instability growth rate is investigated. The results have shown that, by increasing the quantum parameter, for large wavelengths, the Weibel instability growth rate shrinks to zero. In the large wavelengths limit, the analysis shows that quantum effects and density gradient tend to stabilize the Weibel instability. The density perturbations have decreased the growth rate of Weibel instability in the near corona fuel, . In the small wavelengths limit, for the density gradient, , the tunneling quantum effects increase anisotropy in the phase space. The quantum tunneling effect leads to an unexpected increase in the Weibel instability growth rate.
PubDate: Sun, 15 Mar 2015 13:02:21 +000
- Retracted: Extracting the QCD Cutoff Parameter Using the Bernstein
Polynomials and the Truncated Moments
PubDate: Thu, 12 Mar 2015 07:23:10 +000
- Cosmological Evolution of Pilgrim Dark Energy in Gravity
Abstract: We analyze the behavior of pilgrim dark energy with Hubble horizon in gravity. We reconstruct the models through correspondence phenomenon by assuming two values of pilgrim dark energy parameter . We evaluate the equation of state parameter which shows evolution of the universe in the quintessence, vacuum, and phantom phase for both cases of and give favor the pilgrim dark energy phenomenon. Also, squared speed of sound exhibits the stability of model for both cases of . The also provides freezing and thawing regions in this scenario. In this framework, the plane also corresponds to different dark energy scenarios.
PubDate: Tue, 10 Mar 2015 14:16:36 +000