Advances in High Energy Physics
[SJR: 1.334] [H-I: 12] [14 followers] Follow
Open Access journal
ISSN (Print) 1687-7357 - ISSN (Online) 1687-7365
Published by Hindawi Publishing Corporation [406 journals]
- Chiral Perturbation Theory for Three-Flavour Lattice QCD with Isospin
Abstract: An important tool for the analysis of results of numerical simulations of lattice QCD is chiral perturbation theory. In the Wilson chiral perturbation theory the effects of the finite lattice spacing are taken into account. In recent years the effects of isospin splitting on the masses of hadrons have been investigated in the Monte Carlo simulations. Correspondingly, in this paper we derive the expansions of the masses of the pseudoscalar mesons in chiral perturbation theory at next-to-leading order for twisted mass lattice QCD with three light quark flavours, taking the mass difference between the up- and downquarks into account. The results include terms up to orders in the quark masses, in the mass splitting between up- and downquarks, and in the lattice spacing, respectively.
PubDate: Wed, 18 May 2016 11:50:13 +000
- The Phase Transition of Higher Dimensional Charged Black Holes
Abstract: We have studied phase transitions of higher dimensional charge black hole with spherical symmetry. We calculated the local energy and local temperature and find that these state parameters satisfy the first law of thermodynamics. We analyze the critical behavior of black hole thermodynamic system by taking state parameters of black hole thermodynamic system, in accordance with considering the state parameters of van der Waals system, respectively. We obtain the critical point of black hole thermodynamic system and find that the critical point is independent of the dual independent variables we selected. This result for asymptotically flat space is consistent with that for AdS spacetime and is intrinsic property of black hole thermodynamic system.
PubDate: Mon, 16 May 2016 11:29:50 +000
- Searching for Minimum in Dependence of Squared Speed-of-Sound on Collision
Abstract: Experimental results of the rapidity distributions of negatively charged pions produced in proton-proton (-) and beryllium-beryllium (Be-Be) collisions at different beam momentums, measured by the NA61/SHINE Collaboration at the super proton synchrotron (SPS), are described by a revised (three-source) Landau hydrodynamic model. The squared speed-of-sound parameter is then extracted from the width of rapidity distribution. There is a local minimum (knee point) which indicates a softest point in the equation of state (EoS) appearing at about GeV/ (or 8.8 GeV) in excitation function (the dependence of on incident beam momentum (or center-of-mass energy)). This knee point should be related to the searching for the onset of quark deconfinement and the critical point of quark-gluon plasma (QGP) phase transition.
PubDate: Thu, 12 May 2016 14:07:05 +000
- Aspects of Screening and Confinement in a Topologically Massive
Abstract: By using the gauge-invariant but path-dependent variables formalism, we consider a recently proposed topologically massive Chern-Simons-Higgs theory in dimensions. In particular, we inspect the impact of a Chern-Simons mixing term between two Abelian gauge fields on physical observables. We pursue our investigation by analyzing the model in two different situations. In the first case, where we integrate the massive excitation and consider an effective model for the massless field, we show that the interaction energy contains a linear term leading to the confinement of static charge probes along with a screening contribution. In the second situation, where the massless field can be exactly integrated with its constraint duly taken into account, the interesting feature is that the resulting effective model describes a purely screening phase, without any trace of a confining regime.
PubDate: Thu, 12 May 2016 10:33:36 +000
- Comparative Multifractal Detrended Fluctuation Analysis of Heavy Ion
Interactions at a Few GeV to a Few Hundred GeV
Abstract: We have studied the multifractality of pion emission process in 16O-AgBr interactions at 2.1 AGeV and 60 AGeV, 12C-AgBr and 24Mg-AgBr interactions at 4.5 AGeV, and 32S-AgBr interactions at 200 AGeV using Multifractal Detrended Fluctuation Analysis (MFDFA) method which is capable of extracting the actual multifractal property filtering out the average trend of fluctuation. The analysis reveals that the pseudorapidity distribution of the shower particles is multifractal in nature for all the interactions; that is, pion production mechanism has inbuilt multiscale self-similarity property. We have employed MFDFA method for randomly generated events for 32S-AgBr interactions at 200 AGeV. Comparison of expt. results with those obtained from randomly generated data set reveals that the source of multifractality in our data is the presence of long range correlation. Comparing the results obtained from different interactions, it may be concluded that strength of multifractality decreases with projectile mass for the same projectile energy and for a particular projectile it increases with energy. The values of ordinary Hurst exponent suggest that there is long range correlation present in our data for all the interactions.
PubDate: Tue, 10 May 2016 16:22:49 +000
- Thermodynamical Study of FRW Universe in Quasi-Topological Theory
Abstract: By applying the unified first law of thermodynamics on the apparent horizon of FRW universe, we get the entropy relation for the apparent horizon in quasi-topological gravity theory. Throughout the paper, the results of considering the Hayward-Kodama and Cai-Kim temperatures are also addressed. Our study shows that whenever there is no energy exchange between the various parts of cosmos, we can get an expression for the apparent horizon entropy in quasi-topological gravity, which is in agreement with other attempts that followed different approaches. The effects of a mutual interaction between the various parts of cosmos on the apparent horizon entropy as well as the validity of second law of thermodynamics in quasi-topological gravity are perused.
PubDate: Tue, 10 May 2016 06:46:55 +000
- Magnetic Hexadecapole Transitions and Neutrino-Nuclear Responses in
Abstract: Neutrino-nuclear responses in the form of squares of nuclear matrix elements, NMEs, are crucial for studies of neutrino-induced processes in nuclei. In this work we investigate magnetic hexadecapole (M4) NMEs in medium-heavy nuclei. The experimentally derived NMEs, (M4), deduced from observed M4 transition half-lives are compared with the single-quasiparticle (QP) NMEs, (M4), and the microscopic quasiparticle-phonon model (MQPM) NMEs (M4). The experimentally derived M4 NMEs are found to be reduced by a coefficient with respect to (M4) and by with respect to (M4). The M4 NMEs are reduced a little by the quasiparticle-phonon correlations of the MQPM wave functions but mainly by other nucleonic and nonnucleonic correlations which are not explicitly included in the MQPM. The found reduction rates are of the same order of magnitude as those for magnetic quadrupole transitions and Gamow-Teller (GT) and spin-dipole (SD) transitions. The impacts of the found reduction coefficients on the magnitudes of the NMEs involved in astroneutrino interactions and neutrinoless double beta decays are discussed.
PubDate: Mon, 09 May 2016 10:57:05 +000
- Corrections to the Jet Quenching Parameter
Abstract: A calculation of corrections to the jet quenching parameter from AdS/CFT correspondence is presented. It is shown that these corrections will increase or decrease the jet quenching parameter depending on the coefficients of the high curvature terms.
PubDate: Sun, 08 May 2016 12:36:25 +000
- Geometric Algebra Techniques in Flux Compactifications
Abstract: We study “constrained generalized Killing (s)pinors,” which characterize supersymmetric flux compactifications of supergravity theories. Using geometric algebra techniques, we give conceptually clear and computationally effective methods for translating supersymmetry conditions into differential and algebraic constraints on collections of differential forms. In particular, we give a synthetic description of Fierz identities, which are an important ingredient of such problems. As an application, we show how our approach can be used to efficiently treat compactification of M-theory on eight manifolds and prove that we recover results previously obtained in the literature.
PubDate: Wed, 27 Apr 2016 12:45:48 +000
- On Dynamical Net-Charge Fluctuations within a Hadron Resonance Gas
Abstract: The dynamical net-charge fluctuations () in different particle ratios , , and are calculated from the hadron resonance gas (HRG) model and compared with STAR central Au+Au collisions at GeV and NA49 central Pb+Pb collisions at GeV. The three charged particle ratios (, and ) are determined as total and average of opposite and average of the same charges. We find an excellent agreement between the HRG calculations and the experimental measurements, especially from STAR beam energy scan (BES) program, while the strange particles in the NA49 experiment at lower Super Proton Synchrotron (SPS) energies are not reproduced by the HRG approach. We conclude that the utilized HRG version seems to take into consideration various types of correlations including strong interactions through the heavy resonances and their decays especially at BES energies.
PubDate: Wed, 27 Apr 2016 12:21:39 +000
- Study of Time Evolution for Approximation of Two-Body Spinless Salpeter
Equation in Presence of Time-Dependent Interaction
Abstract: We approximate the two-body spinless Salpeter equation with the one which is valid in heavy quarks limit. We consider the resulting semirelativistic equation in a time-dependent formulation. We use the Lewis-Riesenfeld dynamical invariant method and series solution to obtain the solutions of the differential equation. We have also done some calculations in order to derive the time evolution operator for the considered problem.
PubDate: Wed, 27 Apr 2016 09:24:47 +000
- An Effective Method to Accurately Calculate the Phase Space Factors for
Abstract: Accurate calculations of the electron phase space factors are necessary for reliable predictions of double-beta decay rates and for the analysis of the associated electron angular and energy distributions. We present an effective method to calculate these phase space factors that takes into account the distorted Coulomb field of the daughter nucleus, yet it allows one to easily calculate the phase space factors with good accuracy relative to the most exact methods available in the recent literature.
PubDate: Wed, 27 Apr 2016 09:17:23 +000
- Study of Strange Charmed Meson Family Using HQET
Abstract: Recently LHCb predicted spin 1 and spin 3 states and which are studied through their strong decays and are assigned to fit the and states in the charm spectroscopy. In this paper, using the heavy quark effective theory, we state that assigning as the mixing of states is rather a better justification to its observed experimental values than a pure state. We study its decay modes variation with hadronic coupling constant and the mixing angle . We appoint spin 3 state as the missing state and also study its decay channel behavior with coupling constant . To appreciate the above results, we check the variation of decay modes for their spin partners states, that is, and , with their masses and strong coupling constant, that is, and . Our calculation using HQET approach gives mixing angle of the state for to lie in the range ( radians radians). Our calculation for coupling constant values gives to lie within value range of and to be 0.40. We expect from experiments to observe this mixing angle to verify our results.
PubDate: Tue, 26 Apr 2016 12:34:33 +000
- Investigation of Pionic Contribution in the Lepton and Antilepton
Production Cross Section in p-Cu and p-Pt Collision
Abstract: For detailed explanation of the experimental results of lepton production cross section in hadronic collisions such as nucleon-nucleon or nucleon-nuclei, it is of great importance to use quarks and sea quarks distribution function inside free and bound nucleons. In this paper, the role of pion cloud inside the nucleus in the structure function of Cu and Pt nuclei and the EMC ratio of these nuclei were investigated by using harmonic oscillator model. Then, in the framework of the Drell-Yan process and conventional nuclear theory, GRV’s quarks distribution functions and pionic quarks distribution functions were used to calculate lepton and antilepton production cross section in p-Cu and p-Pt scattering. From the results and based on the mentioned model, by considering pionic contribution, the theoretical results are improved.
PubDate: Sun, 24 Apr 2016 13:54:29 +000
- Testing an Inflation Model with Nonminimal Derivative Coupling in the
Light of Planck 2015 Data
Abstract: We study the dynamics of a generalized inflationary model in which both the scalar field and its derivatives are coupled with the gravity. We consider a general form of the nonminimal derivative coupling in order to have a complete treatment of the model. By expanding the action up to the second order in perturbation, we study the spectrum of the primordial modes of the perturbations. Also, by expanding the action up to the third order and considering the three-point correlation functions, the amplitude of the non-Gaussianity of the primordial perturbations is studied in both equilateral and orthogonal configurations. Finally, by adopting some sort of potentials, we compare the model in hand with the Planck 2015 released observational data and obtain some constraints on the model’s parameters space. As an important result, we show that the nonminimal couplings help to make models of chaotic inflation that would otherwise be in tension with Planck data, in better agreement with the data. This model is consistent with observation at weak coupling limit.
PubDate: Thu, 21 Apr 2016 09:24:27 +000
- The Use of Low Temperature Detectors for Direct Measurements of the Mass
of the Electron Neutrino
Abstract: Recent years have witnessed many exciting breakthroughs in neutrino physics. The detection of neutrino oscillations has proved that neutrinos are massive particles, but the assessment of their absolute mass scale is still an outstanding challenge in today particle physics and cosmology. Since low temperature detectors were first proposed for neutrino physics experiments in 1984, there has been tremendous technical progress: today this technique offers the high energy resolution and scalability required to perform competitive experiments challenging the lowest electron neutrino masses. This paper reviews the thirty-year effort aimed at realizing calorimetric measurements with sub-eV neutrino mass sensitivity using low temperature detectors.
PubDate: Thu, 21 Apr 2016 08:40:17 +000
- Thermal Condensate Structure and Cosmological Energy Density of the
Abstract: The aim of this paper is to study thermal vacuum condensate for scalar and fermion fields. We analyze the thermal states at the temperature of the cosmic microwave background (CMB) and we show that the vacuum expectation value of the energy momentum tensor density of photon fields reproduces the energy density and pressure of the CMB. We perform the computations in the formal framework of the Thermo Field Dynamics. We also consider the case of neutrinos and thermal states at the temperature of the neutrino cosmic background. Consistency with the estimated lower bound of the sum of the active neutrino masses is verified. In the boson sector, nontrivial contribution to the energy of the universe is given by particles of masses of the order of 10−4 eV compatible with the ones of the axion-like particles. The fractal self-similar structure of the thermal radiation is also discussed and related to the coherent structure of the thermal vacuum.
PubDate: Mon, 18 Apr 2016 06:24:41 +000
- The Minimal Length and the Shannon Entropic Uncertainty Relation
Abstract: In the framework of the generalized uncertainty principle, the position and momentum operators obey the modified commutation relation , where is the deformation parameter. Since the validity of the uncertainty relation for the Shannon entropies proposed by Beckner, Bialynicki-Birula, and Mycielski (BBM) depends on both the algebra and the used representation, we show that using the formally self-adjoint representation, that is, and , where , the BBM inequality is still valid in the form as well as in ordinary quantum mechanics. We explicitly indicate this result for the harmonic oscillator in the presence of the minimal length.
PubDate: Sun, 17 Apr 2016 07:42:07 +000
- Neutrinoless Double Beta Decay: 2015 Review
Abstract: The discovery of neutrino masses through the observation of oscillations boosted the importance of neutrinoless double beta decay (). In this paper, we review the main features of this process, underlining its key role from both the experimental and theoretical point of view. In particular, we contextualize the in the panorama of lepton number violating processes, also assessing some possible particle physics mechanisms mediating the process. Since the existence is correlated with neutrino masses, we also review the state of the art of the theoretical understanding of neutrino masses. In the final part, the status of current experiments is presented and the prospects for the future hunt for are discussed. Also, experimental data coming from cosmological surveys are considered and their impact on expectations is examined.
PubDate: Thu, 14 Apr 2016 15:23:55 +000
- Analytic Approximation of Energy Resolution in Cascaded Gaseous Detectors
Abstract: An approximate formula has been derived for gain fluctuations in cascaded gaseous detectors such as Gas Electron Multipliers (GEMs), based on the assumption that the charge collection, avalanche formation, and extraction steps are independent cascaded processes. In order to test the approximation experimentally, a setup involving a standard GEM layer has been constructed to measure the energy resolution for 5.9 keV gamma particles. The formula reasonably traces both the charge collection and the extraction process dependence of the energy resolution. Such analytic approximation for gain fluctuations can be applied to multi-GEM detectors where it aids the interpretation of measurements as well as simulations.
PubDate: Thu, 14 Apr 2016 12:14:46 +000
- Comparing the Tsallis Distribution with and without Thermodynamical
Description in Collisions
Abstract: We compare two types of Tsallis distribution, that is, with and without thermodynamical description, using the experimental data from the STAR, PHENIX, ALICE, and CMS Collaborations on the rapidity and energy dependence of the transverse momentum spectra in collisions. Both of them can fit the particle spectra well. We show that the Tsallis distribution with thermodynamical description gives lower temperatures than the ones without it. The extra factor (transverse mass) in the Tsallis distribution with thermodynamical description plays an important role in the discrepancies between the two types of Tsallis distribution. But for the heavy particles, the choice to use or (transverse energy) in the Tsallis distribution becomes more crucial.
PubDate: Sun, 10 Apr 2016 11:30:48 +000
- On the Compatibility of the Diboson Excess with a -Initiated Composite
Abstract: We propose that recent results by ATLAS and CMS searching for heavy resonances decaying into bosons could be a first hint of a new sector of pure gauge confining physics, possibly linked to the origin of the Higgs as a Composite Higgs. The lightest resonances (glueballs) of this new sector would be neutral, spin-zero, and spin-two, and their behaviour would resemble that of a radion and a massive graviton of extra dimensions. We outline how 13 TeV LHC data could be used to improve sensitivity on this scenario, as well as future characterization during the 13 TeV LHC run.
PubDate: Wed, 06 Apr 2016 07:53:05 +000
- QCD Thermodynamics and Magnetization in Nonzero Magnetic Field
Abstract: In nonzero magnetic field, the magnetic properties and thermodynamics of the quantum-chromodynamic (QCD) matter are studied in the hadron resonance gas and the Polyakov linear-sigma models and compared with recent lattice calculations. Both models are fairly suited to describe the degrees of freedom in the hadronic phase. The partonic ones are only accessible by the second model. It is found that the QCD matter has paramagnetic properties, which monotonically depend on the temperature and are not affected by the hadron-quark phase transition. Furthermore, raising the magnetic field strength increases the thermodynamic quantities, especially in the hadronic phase, but reduces the critical temperature, that is, inverse magnetic catalysis.
PubDate: Mon, 04 Apr 2016 15:05:11 +000
- Noncommutative Wormhole Solutions in Einstein Gauss-Bonnet Gravity
Abstract: We explore static spherically symmetric wormhole solutions in the framework of -dimensional Einstein Gauss-Bonnet gravity. Our objective is to find out wormhole solutions that satisfy energy conditions. For this purpose, we consider two frameworks such as Gaussian distributed and Lorentzian distributed noncommutative geometry. Taking into account constant redshift function, we obtain solutions in the form of shape function. The fifth and sixth dimensional solutions with positive as well as negative Gauss-Bonnet coefficient are discussed. Also, we check the equilibrium condition for the wormhole solutions with the help of generalized Tolman-Oppenheimer-Volkoff equation. It is interesting to mention here that we obtain fifth dimensional stable wormhole solutions in both distributions that satisfy the energy conditions.
PubDate: Mon, 04 Apr 2016 09:16:50 +000
- Study of Decays with QCD Factorization Approach
Abstract: Motivated by the -physics experiments at running LHC and upcoming SuperKEKB/Belle-II, the nonleptonic ( and ) weak decays are studied within QCD factorization framework. The observables of these decay modes are first predicted. It is found that the tree-dominated and CKM-favored decays have the largest branching fractions and thus are hopefully to be measured. The decays are dominated by the longitudinal polarization states. In addition, associating with the relevant meson decays, some interesting phenomena and relations are discussed in detail; for example, , and .
PubDate: Thu, 31 Mar 2016 17:34:09 +000
- The Mixed Phase of Charged AdS Black Holes
Abstract: We study the mixed phase of charged AdS black hole and radiation when the total energy is fixed below the threshold to produce a stable charged black hole branch. The coexistence conditions for the charged AdS black hole and radiation are derived for the generic case when radiation particles carry charge. The phase diagram of the mixed phase is demonstrated for both fixed potential and charge ensemble. In the dual gauge picture, they correspond to the mixed phase of quark-gluon plasma (QGP) and hadron gas in the fixed chemical potential and density ensemble, respectively. In the nuclei and heavy-ion collisions at intermediate energies, the mixed phase of exotic QGP and hadron gas could be produced. The mixed phase will condense and evaporate into the hadron gas as the fireball expands.
PubDate: Wed, 30 Mar 2016 11:35:34 +000
- Supersymmetric Quantum Mechanics and Topology
Abstract: Supersymmetric quantum mechanical models are computed by the path integral approach. In the limit, the integrals localize to the zero modes. This allows us to perform the index computations exactly because of supersymmetric localization, and we will show how the geometry of target space enters the physics of sigma models resulting in the relationship between the supersymmetric model and the geometry of the target space in the form of topological invariants. Explicit computation details are given for the Euler characteristics of the target manifold and the index of Dirac operator for the model on a spin manifold.
PubDate: Mon, 28 Mar 2016 16:23:18 +000
- Relationship between Fujikawa’s Method and the Background Field
Method for the Scale Anomaly
Abstract: We show the equivalence between Fujikawa’s method for calculating the scale anomaly and the diagrammatic approach to calculating the effective potential via the background field method, for an symmetric scalar field theory. Fujikawa’s method leads to a sum of terms, each one superficially in one-to-one correspondence with a vacuum diagram of the 1-loop expansion. From the viewpoint of the classical action, the anomaly results in a breakdown of the Ward identities due to scale-dependence of the couplings, whereas, in terms of the effective action, the anomaly is the result of the breakdown of Noether’s theorem due to explicit symmetry breaking terms of the effective potential.
PubDate: Thu, 17 Mar 2016 12:49:00 +000
- Transition Form Factors of in QCD
Abstract: The form factors of the semileptonic decay are calculated by using the QCD sum rule technique. The results obtained are then used to estimate the decay widths of this transition in all lepton channels. The orders of decay rates indicate that this transition is accessible at LHC for all lepton channels.
PubDate: Thu, 17 Mar 2016 08:37:28 +000
- Comparative Aspects of Spin-Dependent Interaction Potentials for Spin-1/2
and Spin-1 Matter Fields
Abstract: This paper sets out to establish a comparative study between classes of spin- and velocity-dependent potentials for spin-1/2 and spin-1 matter currents/sources in the nonrelativistic regime. Both (neutral massive) scalar and vector particles are considered to mediate the interactions between (pseudo-)scalar sources or (pseudo-)vector currents. Though our discussion is more general, we contemplate specific cases in which our results may describe the electromagnetic interaction with a massive (Proca-type) photon exchanged between two spin-1/2 or two spin-1 carriers. We highlight the similarities and peculiarities of the potentials for the two different types of charged matter and also focus our attention on the comparison between the particular aspects of two different field representations for spin-1 matter particles. We believe that our results may contribute to a further discussion of the relation between charge, spin, and extensibility of elementary particles.
PubDate: Wed, 16 Mar 2016 12:50:37 +000