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 [356 journals] [SJR: 1.297] [H-I: 7]
- The Low-Scale Approach to Neutrino Masses
Abstract: In this short review we revisit the broad landscape of low-scale models of neutrino mass generation, with view on their phenomenological potential. This includes signatures associated to direct neutrino mass messenger production at the LHC, as well as messenger-induced lepton flavor violation processes. We also briefly comment on the presence of WIMP cold dark matter candidates.
PubDate: Thu, 14 Aug 2014 13:46:34 +000
- Dihadron Azimuthal Correlations in 200 GeV Au-Au and
2.76 TeV Pb-Pb Collisions
Abstract: In a multisource thermal model, we detailedly show dihadron azimuthal correlations for 20–40% and 50–80% in Au-Au collisions at GeV and over a centrality range from 10–15% to 70–80% in Pb-Pb collisions at TeV. The model can approximately describe the azimuthal correlations of particles produced in the collisions. The amplitude of the corresponding source is magnified, and the source translates along the direction. The factor , in most cases, increases with the increase of the centrality in Pb-Pb collisions at TeV.
PubDate: Wed, 13 Aug 2014 12:08:31 +000
- Analytical Solution of the Schrödinger Equation with Spatially
Varying Effective Mass for Generalised Hylleraas Potential
Abstract: We have obtained exact solution of the effective mass Schrödinger equation for the generalised Hylleraas potential. The exact bound state energy eigenvalues and corresponding eigenfunctions are presented. The bound state eigenfunctions are obtained in terms of the hypergeometric functions. Results are also given for the special case of potential parameter.
PubDate: Mon, 11 Aug 2014 00:00:00 +000
- Transport Coefficients for Holographic Hydrodynamics at Finite Energy
Abstract: We investigate the relations between black hole thermodynamics and holographic transport coefficients in this paper. The formulae for DC conductivity and diffusion coefficient are verified for electrically single-charged black holes. We examine the correctness of the proposed expressions by taking charged dilatonic and single-charged STU black holes as two concrete examples, and compute the flows of conductivity and diffusion coefficient by solving the linear order perturbation equations. We then check the consistence by evaluating the Brown-York tensor at a finite radial position. Finally, we find that the retarded Green functions for the shear modes can be expressed easily in terms of black hole thermodynamic quantities and transport coefficients.
PubDate: Sun, 10 Aug 2014 09:04:26 +000
- Rough Mirror as a Quantum State Selector: Analysis and Design
Abstract: We report analysis of rough mirrors used as the gravitational state selectors in neutron beam and similar experiments. The key to mirror properties is its roughness correlation function (CF) which is extracted from the precision optical scanning measurements of the surface profile. To identify CF in the presence of fluctuation-driven fat tails, we perform numerical experiments with computer-generated random surfaces with the known CF. These numerical experiments provide a reliable identification procedure which we apply to the actual rough mirror. The extracted CF allows us to make predictions for ongoing GRANIT experiments. We also propose a radically new design for rough mirrors based on Monte Carlo simulations for the 1D Ising model. The implementation of this design provides a controlled environment with predictable scattering properties.
PubDate: Mon, 04 Aug 2014 11:42:13 +000
- Performance of Water-Based Liquid Scintillator: An Independent Analysis
Abstract: The water-based liquid scintillator (WbLS) is a new material currently under development. It is based on the idea of dissolving the organic scintillator in water using special surfactants. This material strives to achieve the novel detection techniques by combining the Cerenkov rings and scintillation light, as well as the total cost reduction compared to pure liquid scintillator (LS). The independent light yield measurement analysis for the light yield measurements using three different proton beam energies (210 MeV, 475 MeV, and 2000 MeV) for water, two different WbLS formulations (0.4% and 0.99%), and pure LS conducted at Brookhaven National Laboratory, USA, is presented. The results show that a goal of ~100 optical photons/MeV, indicated by the simulation to be an optimal light yield for observing both the Cerenkov ring and the scintillation light from the proton decay in a large water detector, has been achieved.
PubDate: Thu, 24 Jul 2014 11:39:57 +000
- Quantized Ultracold Neutrons in Rough Waveguides: GRANIT Experiments and
Abstract: We apply our general theory of transport in systems with random rough boundaries to gravitationally quantized ultracold neutrons in rough waveguides as in GRANIT experiments (ILL, Grenoble). We consider waveguides with roughness in both two and one dimensions (2D and 1D). In the biased diffusion approximation the depletion times for the gravitational quantum states can be easily expressed via each other irrespective of the system parameters. The calculation of the exit neutron count reduces to evaluation of a single constant which contains a complicated integral of the correlation function of surface roughness. In the case of 1D roughness (random grating) this constant is calculated analytically for common types of the correlation functions. The results obey simple scaling relations which are slightly different in 1D and 2D. We predict the exit neutron count for the new GRANIT cell.
PubDate: Wed, 23 Jul 2014 09:27:48 +000
- In-Pile 4He Source for UCN Production at the ESS
Abstract: ESS will be a premier neutron source facility. Unprecedented neutron beam intensities are ensured by spallation reactions of a 5 MW, 2.0 GeV proton beam impinging on a tungsten target equipped with advanced moderators. The work presented here aims at investigating possibilities for installing an ultra cold neutron (UCN) source at the ESS. One consequence of using the recently proposed flat moderators is that they take up less space than the moderators originally foreseen and thus leave more freedom to design a UCN source, close to the spallation hotspot. One of the options studied is to place a large 4He UCN source in a through-going tube which penetrates the shielding below the target. First calculations of neutron flux available for UCN production are given, along with heat-load estimates. It is estimated that the flux can give rise to a UCN production at a rate of up to UCN/s. A production in this range potentially allows for a number of UCN experiments to be carried out at unprecedented precision, including, for example, quantum gravitational spectroscopy with UCNs which rely on high phase-space density.
PubDate: Wed, 23 Jul 2014 08:26:15 +000
- Proposal to Search for a Dark Photon in Positron on Target Collisions at
Abstract: Photon-like particles are predicted in many extensions of the Standard Model. They have interactions similar to the photon, are vector bosons, and can be produced together with photons. The present paper proposes a search for such particles in the process in a positron-on-target experiment, exploiting the positron beam of the DANE linac at the Laboratori Nazionali di Frascati, INFN. In one year of running a sensitivity in the relative interaction strength down to ~10−6 is achievable, in the mass region from 2.5 MeV. The proposed experimental setup and the analysis technique are discussed.
PubDate: Tue, 22 Jul 2014 12:04:23 +000
- Heavy Scalar, Vector, and Axial-Vector Mesons in Hot and Dense Nuclear
Abstract: In this work we shall investigate the mass modifications of scalar mesons (; ), vector mesons (; ), and axial-vector mesons (; ) at finite density and temperature of the nuclear medium. The above mesons are modified in the nuclear medium through the modification of quark and gluon condensates. We will find the medium modification of quark and gluon condensates within chiral SU(3) model through the medium modification of scalar-isoscalar fields and at finite density and temperature. These medium modified quark and gluon condensates will further be used through QCD sum rules for the evaluation of in-medium properties of the above mentioned scalar, vector, and axial vector mesons. We will also discuss the effects of density and temperature of the nuclear medium on the scattering lengths of the above scalar, vector, and axial-vector mesons. The study of the medium modifications of the above mesons may be helpful for understanding their production rates in heavy-ion collision experiments. The results of present investigations of medium modifications of scalar, vector, and axial-vector mesons at finite density and temperature can be verified in the compressed baryonic matter (CBM) experiment of FAIR facility at GSI, Germany.
PubDate: Tue, 22 Jul 2014 11:23:37 +000
- Emission of Protons and Charged Pions in p + Cu and p + Pb Collisions at
3, 8, and 15 GeV/c
Abstract: We present an analysis of proton and charged pion transverse momentum spectra of and reactions at 3, 8, and 15 GeV/c in the framework of a multisource thermal model. The spectra are compared closely with the experimental data of HARP-CDP at all angular intervals. The result shows that the widths of the particle distributions in both and collisions decrease with increasing the angle for the same incident momentum.
PubDate: Sun, 20 Jul 2014 06:28:10 +000
- Common Behaviors of Spinor-Type Instantons in 2D Thirring and 4D Gursey
Abstract: We investigate two examples of conformal invariant pure spinor fermionic models, which admit particle-like solutions of the classical field equations. For different dimensions and quantum spinor numbers, the vector field visualizations of the models are constructed to provide a better understanding of the spinor-type instanton dynamics in phase space. The hierarchical cluster analysis method investigations of the models are also presented. Finally, the autocorrelation and power spectrum graphs of models are constructed and frequencies of motions are defined.
PubDate: Thu, 17 Jul 2014 10:07:40 +000
- On Finite Interquark Potential in Driven by a Minimal Length
Abstract: We address the effect of a quantum gravity induced minimal length on a physical observable for three-dimensional Yang-Mills. Our calculation is done within stationary perturbation theory. Interestingly enough, we find an ultraviolet finite interaction energy, which contains a regularized logarithmic function and a linear confining potential. This result highlights the role played by the new quantum of length in our discussion.
PubDate: Thu, 17 Jul 2014 00:00:00 +000
- Gaseous Detector with Sub-keV Threshold to Study Neutrino Scattering at
Low Recoil Energies
Abstract: Gaseous detector with a sub-keV electron equivalent threshold is a very perspective tool for the precision measurement of the neutrino magnetic moment and for observing coherent scattering of neutrinos on nuclei. The progress in the development of low noise electronics makes it possible to register the rare events at the threshold less than 100 eV. The construction of the gaseous detector is given and the typical pulses with amplitudes of a few eV observed on a bench scale installation are presented. The possible implications for future experiments are discussed.
PubDate: Tue, 15 Jul 2014 12:27:49 +000
- Scattering and Bound States of Duffin-Kemmer-Petiau Particles for
-Parameter Hyperbolic Pöschl-Teller Potential
Abstract: The Duffin-Kemmer-Petiau (DKP) equation in the presence of a scalar potential is solved in one spatial dimension for the vector -parameter Hyperbolic Pöschl-Teller (HPT) potential. In obtaining complete solutions we used the weak interaction approach and took the scalar and vector potentials in a correlated form. By looking at the asymptotic behaviors of the solutions, we identify the bound and scattering states. We calculate transmission () and reflection () probability densities and analyze their dependence on the potential shape parameters. Also we investigate the dependence of energy eigenvalues of the bound states on the potential shape parameters.
PubDate: Mon, 14 Jul 2014 12:11:09 +000
- Theory of Neutrino-Atom Collisions: The History, Present Status, and BSM
Abstract: An overview of the current theoretical studies on neutrino-atom scattering processes is presented. The ionization channel of these processes, which is studied in experiments searching for neutrino magnetic moments, is brought into focus. Recent developments in the theory of atomic ionization by impact of reactor antineutrinos are discussed. It is shown that the stepping approximation is well applicable for the data analysis practically down to the ionization threshold.
PubDate: Thu, 10 Jul 2014 08:42:21 +000
- Dirac Particle for the Position Dependent Mass in the Generalized
Asymmetric Woods-Saxon Potential
Abstract: The one-dimensional Dirac equation with position dependent mass in the generalized asymmetric Woods-Saxon potential is solved in terms of the hypergeometric functions. The transmission and reflection coefficients are obtained by considering the one-dimensional electric current density for the Dirac particle and the equation describing the bound states is found by utilizing the continuity conditions of the obtained wave function. Also, by using the generalized asymmetric Woods-Saxon potential solutions, the scattering states are found out without making calculation for the Woods-Saxon, Hulthen, cusp potentials, and so forth, which are derived from the generalized asymmetric Woods-Saxon potential and the conditions describing transmission resonances and supercriticality are achieved. At the same time, the data obtained in this work are compared with the results achieved in earlier studies and are observed to be consistent.
PubDate: Thu, 10 Jul 2014 00:00:00 +000
- Chemical Potentials of Quarks Extracted from Particle Transverse Momentum
Distributions in Heavy Ion Collisions at RHIC Energies
Abstract: In the framework of a multisource thermal model, the transverse momentum distributions of charged particles produced in nucleus-nucleus (A-A) and deuteron-nucleus (d-A) collisions at relativistic heavy ion collider (RHIC) energies are investigated by a two-component revised Boltzmann distribution. The calculated results are in agreement with the PHENIX experimental data. It is found that the source temperature increases obviously with increase of the particle mass and incident energy, but it does not show an obvious change with the collision centrality. Then, the values of chemical potentials for up, down, and strange quarks can be obtained from the antiparticle to particle yield ratios in a wide transverse momentum range. The relationship between the chemical potentials of quarks and the transverse momentum with different centralities is investigated, too.
PubDate: Tue, 08 Jul 2014 09:18:48 +000
- Transverse Momentum and Pseudorapidity Distributions of Charged Particles
and Spatial Shapes of Interacting Events in Pb-Pb Collisions at
Abstract: The transverse momentum and pseudorapidity distributions of charged particles produced in Pb-Pb collisions with different centrality intervals at center-of-mass energy per nucleon pair TeV have been analyzed by using the improved multisource thermal model in which the whole interacting system and then the sources are described by the Tsallis statistics. The modelling results are in agreement with experimental data of the ALICE Collaboration. The rapidity distributions of charged particles are obtained according to the extracted parameter values. The shapes of interacting events (the dispersion plots of charged particles) are given in the momentum, rapidity, velocity, and coordinate spaces. Meanwhile, the event shapes in different spaces consisted by different transverse quantities and longitudinal quantities are presented.
PubDate: Mon, 07 Jul 2014 07:51:29 +000
- Eta Prime Gluonic Contribution to the Nucleon Self-Energy in an Effective
Abstract: We estimate a possible gluonic contribution to the self-energy of a nucleon in an effective theory. The couplings of the topological charge density to nucleons give rise to OZI violating -nucleon interactions. The one-loop self-energy of nucleon arising due to these interactions is studied using a heavy baryon chiral perturbation theory. The divergences have been removed using appropriate form factors. The nontrivial structure of the QCD vacuum has also been taken into account. The numerical results are sensitive to the choice of the regulator to a nonnegligible extent. We get the total contribution to the nucleon mass coming from its interaction with the topological charge density % of the nucleon mass.
PubDate: Mon, 07 Jul 2014 00:00:00 +000
- Analytical BPS Maxwell-Higgs Vortices
Abstract: We have established a prescription for the calculation of analytical vortex solutions in the context of generalized Maxwell-Higgs models whose overall dynamics is controlled by two positive functions of the scalar field, namely, and . We have also determined a natural constraint between these functions and the Higgs potential , allowing the existence of axially symmetric Bogomol'nyi-Prasad-Sommerfield (BPS) solutions possessing finite energy. Furthermore, when the generalizing functions are chosen suitably, the nonstandard BPS equations can be solved exactly. We have studied some examples, comparing them with the usual Abrikosov-Nielsen-Olesen (ANO) solution. The overall conclusion is that the analytical self-dual vortices are well-behaved in all relevant sectors, strongly supporting the consistency of the respective generalized models. In particular, our results mimic well-known properties of the usual (numerical) configurations, as localized energy density, while contributing to the understanding of topological solitons and their description by means of analytical methods.
PubDate: Wed, 02 Jul 2014 09:31:45 +000
- Anomalous Couplings in Collision at the LHC
Abstract: We have examined the constraints on the anomalous couplings through the process at the LHC by considering four forward detector acceptances: , , , and , where with and the energies of the photon and of the incoming proton, respectively. The sensitivity bounds on the anomalous couplings have been obtained at the 95% confidence level in a model independent effective Lagrangian approach. We have found that the bounds on these couplings can be highly improved compared to current experimental bounds.
PubDate: Wed, 02 Jul 2014 08:35:50 +000
- Exact Solutions of the Dirac Hamiltonian on the Sphere under Hyperbolic
Abstract: Two-dimensional massless Dirac Hamiltonian under the influence of hyperbolic magnetic fields is mentioned in curved space. Using a spherical surface parameterization, the Dirac operator on the sphere is presented and the system is given as two supersymmetric partner Hamiltonians which coincides with the position dependent mass Hamiltonians. We introduce two ansatzes for the component of the vector potential to acquire effective solvable models, which are Rosen-Morse II potential and the model given Midya and Roy, whose bound states are Jacobi type polynomials, and we adapt our work to these special models under some parameter restrictions. The energy spectrum and the eigenvectors are found for Rosen-Morse II potential. On the other hand, complete solutions are given for the second system. The vector and the effective potentials with their eigenvalues are sketched for each system.
PubDate: Tue, 01 Jul 2014 11:44:53 +000
- Astronomical Signatures of Dark Matter
Abstract: Several independent astronomical observations in different wavelength bands reveal the existence of much larger quantities of matter than what we would deduce from assuming a solar mass to light ratio. They are very high velocities of individual galaxies within clusters of galaxies, higher than expected rotation rates of stars in the outer regions of galaxies, 21 cm line studies indicative of increasing mass to light ratios with radius in the halos of spiral galaxies, hot gaseous X-ray emitting halos around many elliptical galaxies, and clusters of galaxies requiring a much larger component of unseen mass for the hot gas to be bound. The level of gravitational attraction needed for the spatial distribution of galaxies to evolve from the small perturbations implied by the very slightly anisotropic cosmic microwave background radiation to its current web-like configuration requires much more mass than is observed across the entire electromagnetic spectrum. Distorted shapes of galaxies and other features created by gravitational lensing in the images of many astronomical objects require an amount of dark matter consistent with other estimates. The unambiguous detection of dark matter and more recently evidence for dark energy has positioned astronomy at the frontier of fundamental physics as it was in the 17th century.
PubDate: Thu, 26 Jun 2014 00:00:00 +000
- The Annual Modulation Signature for Dark Matter: DAMA/LIBRA-Phase1 Results
Abstract: The results obtained with the total exposure of 1.04 ton × yr collected by DAMA/LIBRA-phase1 deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. during 7 annual cycles are summarized. The DAMA/LIBRA-phase1 and the former DAMA/NaI data (cumulative exposure 1.33 ton × yr, corresponding to 14 annual cycles) give evidence at 9.3 σ C.L. for the presence of Dark Matter (DM) particles in the galactic halo, on the basis of the exploited model independent DM annual modulation signature by using highly radiopure NaI(Tl) target. The modulation amplitude of the single-hit events in the (2–6) keV energy interval is cpd/kg/keV; the measured phase is days and the measured period is yr; values are in a good well in agreement with those expected for DM particles. No systematic or side reactions able to mimic the exploited DM signature have been found or suggested by anyone over more than a decade. Some of the perspectives of the presently running DAMA/LIBRA-phase2 are outlined.
PubDate: Tue, 24 Jun 2014 00:00:00 +000
- Experimental Tests of Quantum Gravity and Exotic Quantum Field Theory
PubDate: Mon, 23 Jun 2014 12:16:27 +000
- Remarks on the Spin-One Duffin-Kemmer-Petiau Equation in the Presence of
Nonminimal Vector Interactions in Dimensions
Abstract: We point out a misleading treatment in the recent literature regarding analytical solutions for nonminimal vector interaction for spin-one particles in the context of the Duffin-Kemmer-Petiau (DKP) formalism. In those papers, the authors use improperly the nonminimal vector interaction endangering in their main conclusions. We present a few properties of the nonminimal vector interactions and also present the correct equations to this problem. We show that the solution can be easily found by solving Schrödinger-like equations. As an application of this procedure, we consider spin-one particles in presence of a nonminimal vector linear potential.
PubDate: Thu, 19 Jun 2014 12:47:50 +000
- Nuclear Stopping in Central Au+Au Collisions at RHIC Energies
Abstract: Nuclear stopping in central Au+Au collisions at relativistic heavy-ion collider (RHIC) energies is studied in the framework of a cascade mode and the modified ultrarelativistic quantum molecular dynamics (UrQMD) transport model. In the modified mode, the mean field potentials of both formed and “preformed” hadrons (from string fragmentation) are considered. It is found that the nuclear stopping is increasingly influenced by the mean-field potentials in the projectile and target regions with the increase of the reaction energy. In the central region, the calculations of the cascade model considering the modifying factor can describe the experimental data of the PHOBOS collaboration.
PubDate: Tue, 17 Jun 2014 09:02:29 +000
- Neutrinos as Probes of Lorentz Invariance
Abstract: Neutrinos can be used to search for deviations from exact Lorentz invariance. The worldwide experimental program in neutrino physics makes these particles a remarkable tool to search for a variety of signals that could reveal minute relativity violations. This paper reviews the generic experimental signatures of the breakdown of Lorentz symmetry in the neutrino sector.
PubDate: Mon, 16 Jun 2014 06:29:53 +000
- Constraints on Heavy Neutrino and SUSY Parameters Derived from the Study
of Neutrinoless Double Beta Decay
Abstract: New constraints on the lepton number violating (LNV) parameters are derived from the analysis of the neutrinoless double beta () decay in the hypothesis that this process would occur through the exchange of heavy neutrinos and/or SUSY particles. For derivation, we use new values of both phase space factors (PSFs) and nuclear matrix elements (NMEs) calculated with numerical codes developed recently, as well as the most recent experimental lifetimes. The NMEs are computed with a shell model (ShM) code for , , and nuclei, while at present similar ShM results are available only for the first nucleus. We compare our results with similar ones from literature, obtained with ShM, QRPA, and IBM-2 methods, and conclude that more results are needed for a relevant analysis on the validity of NMEs associated with these decay mechanisms.
PubDate: Mon, 16 Jun 2014 00:00:00 +000