Advances in High Energy Physics
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Open Access journal
ISSN (Print) 1687-7357 - ISSN (Online) 1687-7365
Published by Hindawi Publishing Corporation [344 journals] [SJR: 1.297] [H-I: 7]
- Influence of Neutral Currents on Electron and Gamma Polarizations in the
Abstract: The differential cross section of electron inelastic scattering by nuclei followed by γ radiation is calculated using the multipole decomposition of the hadronic currents and by taking into account the longitudinal polarization of the initial electron and the circular polarization of the γ radiation. We performed the analysis of the angular and energy dependence of the degree of electron and photon polarization which can yield information on values of weak neutral currents parameters.
PubDate: Thu, 05 Jun 2014 07:36:23 +000
- Dark Atoms and Dark Radiation
PubDate: Wed, 04 Jun 2014 09:25:18 +000
- Dynamics of Interacting Tachyonic Teleparallel Dark Energy
Abstract: We consider a tachyon scalar field which is nonminimally coupled to gravity in the framework of teleparallel gravity. We analyze the phase-space of the model, known as tachyonic teleparallel dark energy, in the presence of an interaction between dark energy and background matter. We find that although there exist some late-time accelerated attractor solutions, there is no scaling attractor. So, unfortunately interacting tachyonic teleparallel dark energy cannot alleviate the coincidence problem.
PubDate: Tue, 03 Jun 2014 12:37:15 +000
- Black Holes Physics
PubDate: Wed, 28 May 2014 12:00:51 +000
- Constraints on Light Neutrino Parameters Derived from the Study of
Neutrinoless Double Beta Decay
Abstract: The study of the neutrinoless double beta decay mode can provide us with important information on the neutrino properties, particularly on the electron neutrino absolute mass. In this work we revise the present constraints on the neutrino mass parameters derived from the decay analysis of the experimentally interesting nuclei. We use the latest results for the phase space factors (PSFs) and nuclear matrix elements (NMEs), as well as for the experimental lifetime limits. For the PSFs we use values computed with an improved method reported very recently. For the NMEs we use values chosen from the literature on a case-by-case basis, taking advantage of the consensus reached by the community on several nuclear ingredients used in their calculation. Thus, we try to restrict the range of spread of the NME values calculated with different methods and, hence, to reduce the uncertainty in deriving limits for the Majorana neutrino mass parameter. Our results may be useful to have an updated image on the present neutrino mass sensitivities associated with measurements for different isotopes and to better estimate the range of values of the neutrino masses that can be explored in the future double beta decay (DBD) experiments.
PubDate: Wed, 28 May 2014 11:00:15 +000
- Anomalous -Factors for Charged Leptons in a Fractional Coarse-Grained
Abstract: We here propose to extend the concept of helicity to include it in a fractional scenario and we write down the left- and the right-handed Weyl equations from first principles in this extended framework. Next, by coupling the different fractional Weyl sectors by means of a mass parameter, we arrive at the fractional version of Dirac's equation which, whenever coupled to an external electromagnetic field and reduced to the nonrelativistic regime, yields a fractional Pauli-type equation. From the latter, we are able to present an explicit expression for the gyromagnetic ratio of charged fermions in terms of the fractionality parameter. We then focus our efforts to relate the coarse-grained property of space-time to fractionality and to the () anomalies of the different leptonic species.
PubDate: Sun, 25 May 2014 12:54:31 +000
- Study of and Decays via QCD Sum Rules
Abstract: We present the calculation of the form factor of the and decays in the frame work of QCD sum rules. We also find branching ratio = which is in agreement with the experimental data. Furthermore, we estimate the MeV, where experimental bound for full width of is MeV.
PubDate: Sun, 25 May 2014 12:16:41 +000
- The Statistical Properties of Spin-One DKP Oscillator under an External
Magnetic Field in Noncommutative Space
Abstract: The spin-one Duffin-Kemmer-Petiau oscillator in uniform magnetic field is studied in noncommutative formalism. The corresponding energy is obtained and thereby the corresponding thermal properties are obtained for both commutative and noncommutative cases.
PubDate: Thu, 22 May 2014 12:40:22 +000
- Testing General Relativistic Predictions with the LAGEOS Satellites
Abstract: The spacetime around Earth is a good environment in order to perform tests of gravitational theories. According to Einstein’s view of gravitational phenomena, the Earth mass-energy content curves the surrounding spacetime in a peculiar way. This (relatively) quiet dynamical environment enables a good reconstruction of geodetic satellites (test masses) orbit, provided that high-quality tracking data are available. This is the case of the LAGEOS satellites, built and launched mainly for geodetic and geodynamical purposes, but equally good for fundamental physics studies. A review of these studies is presented, focusing on data, models, and analysis strategies. Some recent and less recent results are presented. All of them indicate general relativity theory as a very good description of gravitational phenomena, at least in the studied environment.
PubDate: Thu, 22 May 2014 08:54:22 +000
- Nonlocal Quantum Effects in Cosmology
Abstract: Since it is commonly believed that the observed large-scale structure of the universe is an imprint of quantum fluctuations existing at the very early stage of its evolution, it is reasonable to pose the question: do the effects of quantum nonlocality, which are well established now by the laboratory studies, manifest themselves also in the early universe' We try to answer this question by utilizing the results of a few experiments, namely, with the superconducting multi-Josephson-junction loops and the ultracold gases in periodic potentials. Employing a close analogy between the above-mentioned setups and the simplest one-dimensional Friedmann-Robertson-Walker cosmological model, we show that the specific nonlocal correlations revealed in the laboratory studies might be of considerable importance also in treating the strongly nonequilibrium phase transitions of Higgs fields in the early universe. Particularly, they should substantially reduce the number of topological defects (e.g., domain walls) expected due to independent establishment of the new phases in the remote spatial regions. This gives us a hint on resolving a long-standing problem of the excessive concentration of topological defects, inconsistent with observational constraints. The same effect may be also relevant to the recent problem of the anomalous behavior of cosmic microwave background fluctuations at large angular scales.
PubDate: Thu, 22 May 2014 06:47:45 +000
- Cardy-Verlinde Formula and Its Self-Gravitational Corrections for Regular
Abstract: We check the consistency of the entropy of Bardeen and Ayón Beato-García-Bronnikov black holes with the entropy of particular conformal field theory via Cardy-Verlinde formula. We also compute the first-order semiclassical corrections of this formula due to self-gravitational effects by modifying pure extensive and Casimir energy in the context of Keski-Vakkuri, Kraus and Wilczek analysis. It is concluded that the correction term remains positive for both black holes, which leads to the violation of the holographic bound.
PubDate: Wed, 21 May 2014 00:00:00 +000
- On Teleparallel Quantum Gravity in Schwarzschild Space-Time
Abstract: We present the quantization process for Schwarzschild space-time in the context of Teleparallel gravity. In order to achieve such a goal we use the Weyl formalism that establishes a well-defined correspondence between classical quantities which are realized by functions and quantum ones which are realized by operators. In the process of quantization we introduce a fundamental constant that is used to construct what we call the quantum of matter by the imposition of periodic conditions over the eigenfunction.
PubDate: Wed, 21 May 2014 00:00:00 +000
- On Two-Ridge Structure in Two-Particle Azimuthal Correlations in
Proton-Lead Collisions at Large Hadron Collider Energy
Abstract: Two-particle azimuthal correlations are studied in the framework of a multisource thermal model. Each source is assumed to produce many particles. Each particle pair measured in final state is considered to be produced at two emission points (subsources) in a single or two sources. The first emission point corresponds to the production of “trigger” particle and the second one corresponds to that of “associated” particle. There are oscillations and other interactions between the two emission points. In the rest frame of the “associated” particle's emission point, the oscillations and other interactions cause the momentum of the “trigger” particle to depart from the original value. The modelling results are in agreement with the experimental data of proton-lead (p-Pb) collisions at = 5.02 TeV, one of the Large Hadron Collider energies, measured by the ALICE and ATLAS Collaborations.
PubDate: Tue, 20 May 2014 00:00:00 +000
- On Particle Production in Lead-Gold Collision and Azimuthal Anisotropy at
Top SPS Energy
Abstract: In a multisource thermal model, we analyze the dependence of elliptic flow on the transverse momentum . The model results are compared with the data of , , , and measured in Pb + Au collisions at top SPS energy, 17.3 GeV. It is found that the azimuthal anisotropy in the evolution process of high-energy collisions is correlated highly to the number of participant nucleons.
PubDate: Sun, 18 May 2014 08:23:43 +000
- Study on the Neutrino Oscillation with a Next Generation Medium-Baseline
Abstract: For over fifty years, reactor experiments have played an important role in neutrino physics, in both discoveries and precision measurements. One of the methods to verify the existence of neutrino is the observation of neutrino oscillation phenomena. Electron antineutrinos emitted from a reactor provide the measurement of the small mixing angle , providing rich programs of neutrino properties, detector development, nuclear monitoring, and application. Using reactor neutrinos, future reactor neutrino experiments, more precise measurements of ,, and mass hierarchy will be explored. The precise measurement of would be crucial for measuring the CP violation parameters at accelerators. Therefore, reactor neutrino physics will assist in the complete understanding of the fundamental nature and implications of neutrino masses and mixing. In this paper, we investigated several characteristics of RENO-50, which is a future medium-baseline reactor neutrino oscillation experiment, by using the GloBES simulation package.
PubDate: Mon, 12 May 2014 07:51:53 +000
- Hawking-Unruh Hadronization and Strangeness Production in High Energy
Abstract: The thermal multihadron production observed in different high energy collisions poses many basic problems: why do even elementary, and hadron-hadron, collisions show thermal behaviour' Why is there in such interactions a suppression of strange particle production' Why does the strangeness suppression almost disappear in relativistic heavy ion collisions' Why in these collisions is the thermalization time less than fm/c' We show that the recently proposed mechanism of thermal hadron production through Hawking-Unruh radiation can naturally answer the previous questions. Indeed, the interpretation of quark (q)-antiquark () pairs production, by the sequential string breaking, as tunneling through the event horizon of colour confinement leads to thermal behavior with a universal temperature, Mev, related to the quark acceleration, a, by . The resulting temperature depends on the quark mass and then on the content of the produced hadrons, causing a deviation from full equilibrium and hence a suppression of strange particle production in elementary collisions. In nucleus-nucleus collisions, where the quark density is much bigger, one has to introduce an average temperature (acceleration) which dilutes the quark mass effect and the strangeness suppression almost disappears.
PubDate: Sun, 11 May 2014 07:08:46 +000
- State-Space Geometry, Statistical Fluctuations, and Black Holes in String
Abstract: We study the state-space geometry of various extremal and nonextremal black holes in string theory. From the notion of the intrinsic geometry, we offer a state-space perspective to the black hole vacuum fluctuations. For a given black hole entropy, we explicate the intrinsic geometric meaning of the statistical fluctuations, local and global stability conditions, and long range statistical correlations. We provide a set of physical motivations pertaining to the extremal and nonextremal black holes, namely, the meaning of the chemical geometry and physics of correlation. We illustrate the state-space configurations for general charge extremal black holes. In sequel, we extend our analysis for various possible charge and anticharge nonextremal black holes. From the perspective of statistical fluctuation theory, we offer general remarks, future directions, and open issues towards the intrinsic geometric understanding of the vacuum fluctuations and black holes in string theory.
PubDate: Wed, 07 May 2014 09:02:44 +000
- Entanglement in a QFT Model of Neutrino Oscillations
Abstract: Tools of quantum information theory can be exploited to provide a convenient description of the phenomena of particle mixing and flavor oscillations in terms of entanglement, a fundamental quantum resource. We extend such a picture to the domain of quantum field theory where, due to the nontrivial nature of flavor neutrino states, the presence of antiparticles provides additional contributions to flavor entanglement. We use a suitable entanglement measure, the concurrence, that allows extracting the two-mode (flavor) entanglement from the full multimode, multiparticle flavor neutrino states.
PubDate: Mon, 05 May 2014 07:47:24 +000
- Analysis of Scalar Field Cosmology with Phase Space Deformations
Abstract: Phase space deformations on scalar field cosmology are studied. The deformation is introduced by modifying the symplectic structure of the minisuperspace variables. The effects of the deformation are studied in the “C-frame” and the “NC-frame.” In order to remove the ambiguities of working on different frames, a new principle is introduced. When we impose that both frames should be physically equivalent, we conclude that the only possibility for this model, is to have an effective cosmological constant . Finally we bound the parameter space for and .
PubDate: Wed, 30 Apr 2014 14:06:57 +000
- The WArP Experiment: A Double-Phase Argon Detector for Dark Matter
Abstract: Cryogenic noble liquids emerged in the previous decade as one of the best media to perform WIMP dark matter searches, in particular due to the possibility to scale detector volumes to multiton sizes. The WArP experiment was then developed as one of the first to implement the idea of coupling Argon in liquid and gas phase, in order to discriminate -interactions from nuclear recoils and then achieve reliable background rejection. Since its construction, other projects spawned, employing Argon and Xenon and following its steps. The WArP 100l detector was assembled in 2008 at the Gran Sasso National Laboratories (LNGS), as the final step of a years-long R&D programme, aimed at characterising the technology of Argon in double phase for dark matter detection. Though it never actually performed a physics run, a technical run was taken in 2011, to characterise the detector response.
PubDate: Wed, 30 Apr 2014 12:01:12 +000
- Application of AdS/CFT in Nuclear Physics
Abstract: We review some recent progress in studying the nuclear physics especially nucleon-nucleon (NN) force within the gauge-gravity duality, in context of noncritical string theory. Our main focus is on the holographic QCD model based on the AdS6 background. We explain the noncritical holography model and obtain the vector-meson spectrum and pion decay constant. Also, we study the NN interaction in this frame and calculate the nucleonmeson coupling constants. A further topic covered is a toy model for calculating the light nuclei potential. In particular, we calculate the light nuclei binding energies and also excited energies of some available excited states. We compare our results with the results of other nuclear models and also with the experimental data. Moreover, we describe some other issues which are studied using the gauge-gravity duality.
PubDate: Wed, 30 Apr 2014 08:37:50 +000
- Thomas-Fermi Model in the Presence of Natural Cutoffs
Abstract: It has been revealed, in the context of quantum gravity candidates, that measurement of position cannot be done with arbitrary precision and there is a finite resolution of space-time points. This leads naturally to a minimal measurable length of the order of Planck length. Also, in the context of newly proposed doubly special relativity theories, a test particle’s momentum cannot be arbitrarily imprecise leading nontrivially to a maximal momentum for a test particle. These two natural cutoffs affects most of quantum field theoretic arguments in the spirit of condensed matter physics. Here we focus on the role of these natural cutoffs on Thomas-Fermi theory in condensed matter physics. We show how quantum gravity effects can play important role phenomenologically in many-body interactions of solids.
PubDate: Mon, 28 Apr 2014 08:53:03 +000
- Warm Inflation with Nonminimal Derivative Coupling
Abstract: We study the effects of the nonminimal derivative coupling on the dissipative dynamics of the warm inflation where the scalar field is nonminimally coupled to gravity via its kinetic term. We present a detailed calculation of the cosmological perturbations in this setup. We use the recent observational data from the joint data set of WMAP9 + BAO + and also the Planck satellite data to constrain our model parameters for natural and chaotic inflation potentials. We study also the levels of non-Gaussianity in this warm inflation model and we confront the result with recent observational data from the Planck satellite.
PubDate: Sun, 27 Apr 2014 11:48:34 +000
- Amplifying the Hawking Signal in BECs
Abstract: We consider simple models of Bose-Einstein condensates to study analog pair-creation effects, namely, the Hawking effect from acoustic black holes and the dynamical Casimir effect in rapidly time-dependent backgrounds. We also focus on a proposal by Cornell to amplify the Hawking signal in density-density correlators by reducing the atoms’ interactions shortly before measurements are made.
PubDate: Sun, 27 Apr 2014 00:00:00 +000
- Computational Methods for High Energy Physics
PubDate: Thu, 24 Apr 2014 09:44:56 +000
- Gamma-Ray Effects of Dark Forces in Dark Matter Clumps
Abstract: Existence of new gauge U(1) symmetry possessed by dark matter (DM) particles implies the existence of a new Coulomb-like interaction, which leads to Sommerfeld-Gamow-Sakharov enhancement of dark matter annihilation at low relative velocities. We discuss a possibility to put constraints on such dark forces of dark matter from the observational data on the gamma radiation in our Galaxy. Gamma-rays are supposed to originate from annihilation of DM particles in the small scale clumps, in which annihilation rate is supposed to be enhanced, besides higher density, due to smaller relative velocities v of DM particles. For possible cross sections, mass of annihilating particles, masses of clumps, and the contribution of annihilating particles in the total DM density we constrain the strength of new dark long range forces from comparison of predicted gamma-ray signal with Fermi/LAT data on unidentified point-like gamma-ray sources (PGS) as well as on diffuse -radiation. Both data on diffuse radiation and data on PGS put lower constraints on annihilation cross section at any dark interaction constant, where diffuse radiation provides stronger constraint at smaller clump mass. Density of annihilating DM particles is conventionally supposed to be defined by the frozen annihilation processes in early Universe.
PubDate: Wed, 23 Apr 2014 11:56:17 +000
- Quantum Tunnelling for Hawking Radiation from Both Static and Dynamic
Abstract: The paper deals with Hawking radiation from both a general static black hole and a nonstatic spherically symmetric black hole. In case of static black hole, tunnelling of nonzero mass particles is considered and due to complicated calculations, quantum corrections are calculated only up to the first order. The results are compared with those for massless particles near the horizon. On the other hand, for dynamical black hole, quantum corrections are incorporated using the Hamilton-Jacobi method beyond semiclassical approximation. It is found that different order correction terms satisfy identical differential equation and are solved by a typical technique. Finally, using the law of black hole mechanics, a general modified form of the black hole entropy is obtained considering modified Hawking temperature.
PubDate: Wed, 23 Apr 2014 11:34:53 +000
- Pseudorapidity Distribution of Charged Particles and Square Speed of Sound
Abstract: Pseudorapidity distributions of charged particles produced in proton-proton () or proton-antiproton () collisions over an energy range from 0.053 to 7 TeV are studied by using the four-component Landau hydrodynamic model. The results calculated by the model are in agreement with the experimental data of the UA5, PHOBOS, UA1, P238, CDF, ALICE, and CMS Collaborations which present orderly from low to high energies. According to the distribution widths of different components, the values and some features of square speed of sound parameter for “participant” and “spectator” quark components are obtained. It is shown that the speed of sound for “participant” quark components agrees approximately with that for “spectator” quark components in the error ranges. The present work is useful for studying nucleus-nucleus collisions in the related energy range.
PubDate: Tue, 22 Apr 2014 09:04:32 +000
- New Directions in Direct Dark Matter Searches
Abstract: I present the status of direct dark matter detection with specific attention to the experimental results and their phenomenological interpretation in terms of dark matter interactions. In particular I review a new and more general approach to study signals in this field based on nonrelativistic operators which parametrize more efficiently the dark matter-nucleus interactions in terms of a very limited number of relevant degrees of freedom. Then I list the major experimental results, pointing out the main uncertainties that affect the theoretical interpretation of the data. Finally, since the underlying theory that describes both the dark matter and the standard model fields is unknown, I address the uncertainties coming from the nature of the interaction. In particular, the phenomenology of a class of models in which the interaction between dark matter particles and target nuclei is of a long range type is discussed.
PubDate: Wed, 16 Apr 2014 11:45:13 +000
- Decaying Dark Atom Constituents and Cosmic Positron Excess
Abstract: We present a scenario where dark matter is in the form of dark atoms that can accommodate the experimentally observed excess of positrons in PAMELA and AMS-02 while being compatible with the constraints imposed on the gamma-ray ux from Fermi/LAT. This scenario assumes that the dominant component of dark matter is in the form of a bound state between a helium nucleus and a particle and a small component is in the form of a WIMP-like dark atom compatible with direct searches in underground detectors. One of the constituents of this WIMP-like state is a metastable particle with a mass of 1 TeV or slightly below that by decaying to , and produces the observed positron excess. These decays can naturally take place via GUT interactions. If it exists, such a metastable particle can be found in the next run of LHC. The model predicts also the ratio of leptons over baryons in the universe to be close to .
PubDate: Wed, 16 Apr 2014 11:00:35 +000