Advances in High Energy Physics
[SJR: 1.334] [H-I: 12] [11 followers] Follow
Open Access journal
ISSN (Print) 1687-7357 - ISSN (Online) 1687-7365
Published by Hindawi Publishing Corporation [403 journals]
- Diffractive Bremsstrahlung in Hadronic Collisions
Abstract: Production of heavy photons (Drell-Yan), gauge bosons, Higgs bosons, and heavy flavors, which is treated within the QCD parton model as a result of hard parton-parton collision, can be considered a bremsstrahlung process in the target rest frame. In this review, we discuss the basic features of the diffractive channels of these processes in the framework of color dipole approach. The main observation is a dramatic breakdown of diffractive QCD factorisation due to the interplay between soft and hard interactions, which dominates these processes. This observation is crucial for phenomenological studies of diffractive reactions in high energy hadronic collisions.
PubDate: Tue, 25 Aug 2015 07:56:42 +000
- Corrigendum to “Null Geodesics and Strong Field Gravitational
Lensing in a String Cloud Background”
PubDate: Tue, 18 Aug 2015 14:14:54 +000
- Torsion Wave Solutions in Yang-Mielke Theory of Gravity
Abstract: The approach of metric-affine gravity initially distinguishes it from Einstein’s general relativity. Using an independent affine connection produces a theory with 10 + 64 unknowns. We write down the Yang-Mills action for the affine connection and produce the Yang-Mills equation and the so-called complementary Yang-Mills equation by independently varying with respect to the connection and the metric, respectively. We call this theory the Yang-Mielke theory of gravity. We construct explicit spacetimes with pp-metric and purely axial torsion and show that they represent a solution of Yang-Mills theory. Finally we compare these spacetimes to existing solutions of metric-affine gravity and present future research possibilities.
PubDate: Wed, 12 Aug 2015 06:51:38 +000
- Study on the Weak Decays
Abstract: Motivated by the prospects of the potential particle at high-luminosity heavy-flavor experiments, we studied the weak decays, where = , , . The nonfactorizable contributions to hadronic matrix elements are taken into consideration with the QCDF approach. It is found that the CKM-favored decay has branching ratio of , which might be measured promisingly by the future experiments.
PubDate: Mon, 10 Aug 2015 06:42:57 +000
- Scattering State of Klein-Gordon Particles by -Parameter Hyperbolic
Abstract: The one-dimensional Klein-Gordon equation for equal vector and scalar -parameter hyperbolic Poschl-Teller potential is solved in terms of the hypergeometric functions. We calculate in detail the solutions of the scattering and bound states. By virtue of the conditions of equation of continuity of the wave functions, we obtained explicit expressions for the reflection and transmission coefficients and energy equation for the bound state solutions.
PubDate: Sun, 09 Aug 2015 12:56:15 +000
- Fermion Fields in BTZ Black Hole Space-Time and Entanglement Entropy
Abstract: We study the entanglement entropy of fermion fields in BTZ black hole space-time and calculate prefactor of the leading and subleading terms and logarithmic divergence term of the entropy using the discretized model. The leading term is the standard Bekenstein-Hawking area law and subleading term corresponds to first quantum corrections in black hole entropy. We also investigate the corrections to entanglement entropy for massive fermion fields in BTZ space-time. The mass term does not affect the area law.
PubDate: Wed, 05 Aug 2015 05:54:53 +000
- Can Tsallis Distribution Fit All the Particle Spectra Produced at RHIC and
Abstract: The Tsallis distribution has been tested to fit all the particle spectra at mid-rapidity from central events produced in d + Au, Cu + Cu, and Au + Au collisions at RHIC and p + Pb, Pb + Pb collisions at LHC. Even though there are strong medium effects in Cu + Cu and Au + Au collisions, the results show that the Tsallis distribution can be used to fit most of particle spectra in the collisions studied except in Au + Au collisions where some deviations are seen for proton and at low . In addition, as the Tsallis distribution can only fit part of the particle spectra produced in Pb + Pb collisions where is up to 20 GeV/c, a new formula with one more fitting degree of freedom is proposed in order to reproduce the entire region.
PubDate: Wed, 29 Jul 2015 11:18:56 +000
- On Pseudorapidity Distribution and Speed of Sound in High Energy Heavy Ion
Collisions Based on a New Revised Landau Hydrodynamic Model
Abstract: We propose a new revised Landau hydrodynamic model to study systematically the pseudorapidity distributions of charged particles produced in heavy ion collisions over an energy range from a few GeV to a few TeV per nucleon pair. The interacting system is divided into three sources, namely, the central, target, and projectile sources, respectively. The large central source is described by the Landau hydrodynamic model and further revised by the contributions of the small target/projectile sources. The modeling results are in agreement with the available experimental data at relativistic heavy ion collider, large hadron collider, and other energies for different centralities. The value of square speed of sound parameter in different collisions has been extracted by us from the widths of rapidity distributions. Our results show that, in heavy ion collisions at energies of the two colliders, the central source undergoes a phase transition from hadronic gas to quark-gluon plasma liquid phase; meanwhile, the target/projectile sources remain in the state of hadronic gas. The present work confirms that the quark-gluon plasma is of liquid type rather than being of a gas type.
PubDate: Wed, 29 Jul 2015 09:58:52 +000
- Quantum Gravitational Spectroscopy
PubDate: Tue, 28 Jul 2015 13:54:19 +000
- Radiative Corrections to from Three Generations of Majorana Neutrinos and
Abstract: We study the radiative corrections to the mass of the lightest Higgs boson of the MSSM from three generations of Majorana neutrinos and sneutrinos. The spectrum of the MSSM is augmented by three right handed neutrinos and their supersymmetric partners. A seesaw mechanism of type I is used to generate the physical neutrino masses and oscillations that we require to be in agreement with present neutrino data. We present a full one-loop computation of these Higgs mass corrections and analyze in full detail their numerical size in terms of both the MSSM and the new (s)neutrino parameters. A critical discussion on the different possible renormalization schemes and their implications, in particular concerning decoupling, is included.
PubDate: Tue, 28 Jul 2015 11:55:28 +000
- Light of Planck-2015 on Noncanonical Inflation
Abstract: Slow-roll inflationary scenario is considered in noncanonical scalar field model supposing a power-law function for kinetic term and using two formalisms. In the first approach, the potential is picked out as a power-law function, that is, the most common approach in studying inflation. Hamilton-Jacobi approach is selected as the second formalism, so that the Hubble parameter is introduced as a function of scalar field instead of the potential. Employing the last observational data, the free parameters of the model are constrained, and the predicted form of the potential and attractor behavior of the model are studied in detail.
PubDate: Tue, 28 Jul 2015 08:53:18 +000
- Geometrical Method for Thermal Instability of Nonlinearly Charged BTZ
Abstract: We consider three-dimensional BTZ black holes with three models of nonlinear electrodynamics as source. Calculating heat capacity, we study the stability and phase transitions of these black holes. We show that Maxwell, logarithmic, and exponential theories yield only type one phase transition which is related to the root(s) of heat capacity, whereas, for correction form of nonlinear electrodynamics, heat capacity contains two roots and one divergence point. Next, we use geometrical approach for studying classical thermodynamical behavior of the system. We show that Weinhold and Ruppeiner metrics fail to provide fruitful results and the consequences of the Quevedo approach are not completely matched to the heat capacity results. Then, we employ a new metric for solving this problem. We show that this approach is successful and all divergencies of its Ricci scalar and phase transition points coincide. We also show that there is no phase transition for uncharged BTZ black holes.
PubDate: Mon, 27 Jul 2015 08:23:56 +000
- Energy and Momentum of Bianchi Type Universes
Abstract: We obtain the energy and momentum of the Bianchi type universes using different prescriptions for the energy-momentum complexes in the framework of general relativity. The energy and momentum of the Bianchi universes are found to be zero for the parameter of the metric. The vanishing of these results supports the conjecture of Tryon that the universe must have a zero net value for all conserved quantities. This also supports the work of Nathan Rosen with the Robertson-Walker metric. Moreover, it raises an interesting question: “Why is the case so special'”
PubDate: Mon, 27 Jul 2015 07:04:17 +000
- Spin and Pseudospin Symmetry in Generalized Manning-Rosen Potential
Abstract: Spin and pseudospin symmetric Dirac spinors and energy relations are obtained by solving the Dirac equation with centrifugal term for a new suggested generalized Manning-Rosen potential which includes the potentials describing the nuclear and molecular structures. To solve the Dirac equation the Nikiforov-Uvarov method is used and also applied the Pekeris approximation to the centrifugal term. Energy eigenvalues for bound states are found numerically in the case of spin and pseudospin symmetry. Besides, the data attained in the present study are compared with the results obtained in the previous studies and it is seen that our data are consistent with the earlier ones.
PubDate: Wed, 22 Jul 2015 11:17:22 +000
- Energy Conditions of Built-In Inflation Models in Gravitational Theories
Abstract: We examine the validity of energy conditions of built-in inflation models in gravitational theories. For this purpose, we formulate the inequalities of energy conditions by assuming the flat and nonflat Friedmann-Robertson-Walker (FRW) universe. We find the feasible constraints on the constants of integration and evaluate their possible ranges graphically for the consistency of these energy conditions for flat, closed, and open universes. We constrain the constants of integration for flat space-time from the inflation epoch while the closed and open universe constants are constrained from late universe.
PubDate: Thu, 16 Jul 2015 05:54:27 +000
- Resonance and Associated Production at Future Higgs Boson Factory: ILC and
Abstract: We study the prospects of the model with an additional boson to be a Higgs boson factory at high-energy and high-luminosity linear electron positron colliders, such as the ILC and CLIC, through the Higgs-strahlung process , including both the resonant and the nonresonant effects. We evaluate the total cross section of and we calculate the total number of events for integrated luminosities of 500–2000 fb−1 and center of mass energies between 500 and 3000 GeV. We find that the total number of expected events can reach 106, which is a very optimistic scenario and it would be possible to perform precision measurements for both and Higgs boson in future high-energy colliders experiments.
PubDate: Mon, 13 Jul 2015 11:54:51 +000
- Vacuum Condensate, Geometric Phase, Unruh Effect, and Temperature
Abstract: In our previous work the possibility to use the Aharonov-Anandan invariant as a tool in the analysis of disparate systems has been shown, including Hawking and Unruh effects, as well as graphene physics and thermal states. We show that the vacuum condensation, characterizing such systems, is also related with geometric phases and we analyze the properties of the geometric phase of systems represented by mixed state and undergoing a nonunitary evolution. In particular, we consider two-level atoms accelerated by an external potential and interacting with a thermal state. We propose the realization of Mach-Zehnder interferometers which can prove the existence of the Unruh effect and can allow very precise measurements of temperature.
PubDate: Tue, 07 Jul 2015 12:17:59 +000
- Beam Purity for Light Dark Matter Search in Beam Dump Experiments
Abstract: This paper reviews the search for light dark matter in beam dump experiments with a special emphasis on the necessity of beam purity for precise background rejection at the sensitivities aimed at these experiments. As a case study we cite the P348 experiment which has test beam time in Fall 2015 at the SPS H4 beam line at CERN and aims to search for the gauge boson, , which as per one model of dark matter mediates a weak interaction between ordinary matter and dark matter via mixing of these “dark photons” with ordinary photon. The experiment aims to probe the still unexplored area of mixing strength and masses MeV by using 10–300 GeV electron beam from the CERN SPS. This paper presents the simulation results for rejection of background due to beam impurity, by tracking the incoming particles with Micromegas detectors at a level <.
PubDate: Thu, 02 Jul 2015 11:42:50 +000
- On Productions of Net-Baryons in Central Au-Au Collisions at RHIC Energies
Abstract: The transverse momentum and rapidity distributions of net-baryons (baryons minus antibaryons) produced in central gold-gold (Au-Au) collisions at 62.4 and 200 GeV are analyzed in the framework of a multisource thermal model. Each source in the model is described by the Tsallis statistics to extract the effective temperature and entropy index from the transverse momentum distribution. The two parameters are used as input to describe the rapidity distribution and to extract the rapidity shift and contribution ratio. Then, the four types of parameters are used to structure some scatter plots of the considered particles in some three-dimensional (3D) spaces at the stage of kinetic freeze-out, which are expected to show different characteristics for different particles and processes. The related methodology can be used in the analyses of particle production and event holography, which are useful for us to better understand the interacting mechanisms.
PubDate: Mon, 29 Jun 2015 12:34:13 +000
- Virial Theorem for Nonrelativistic Quantum Fields in Spatial Dimensions
Abstract: The virial theorem for nonrelativistic complex fields in spatial dimensions and with arbitrary many-body potential is derived, using path-integral methods and scaling arguments recently developed to analyze quantum anomalies in low-dimensional systems. The potential appearance of a Jacobian due to a change of variables in the path-integral expression for the partition function of the system is pointed out, although in order to make contact with the literature most of the analysis deals with the case. The virial theorem is recast into a form that displays the effect of microscopic scales on the thermodynamics of the system. From the point of view of this paper the case usually considered, , is not natural, and the generalization to the case is briefly presented.
PubDate: Mon, 22 Jun 2015 13:21:24 +000
- Comparing Particle Productions at RHIC and LHC Energies
PubDate: Thu, 18 Jun 2015 08:04:24 +000
- Noether Gauge Symmetry of Dirac Field in (2 + 1)-Dimensional Gravity
Abstract: We consider a gravitational theory including a Dirac field that is nonminimally coupled to gravity in 2 + 1 dimensions. Noether gauge symmetry approach can be used to fix the form of coupling function and the potential of the Dirac field and to obtain a constant of motion for the dynamical equations. In the context of (2 + 1)-dimensional gravity, we investigate cosmological solutions of the field equations using these forms obtained by the existence of Noether gauge symmetry. In this picture, it is shown that, for the nonminimal coupling case, the cosmological solutions indicate both an early-time inflation and late-time acceleration for the universe.
PubDate: Mon, 15 Jun 2015 14:08:25 +000
- Production of Kaon and in Nucleus-Nucleus Collisions at Ultrarelativistic
Energy from a Blast-Wave Model
Abstract: The particle production of Kaon and is studied in nucleus-nucleus collisions at relativistic energy based on a chemical equilibrium blast-wave model. The transverse momentum spectra of Kaon and at the kinetic freeze-out stage from our model are in good agreement with the experimental results. The kinetic freeze-out parameters of temperature and radial flow parameter are presented for the FOPI, RHIC, and LHC energies. And the resonance decay effect is also discussed. The systematic study for beam energy dependence of the strangeness particle production will help us to better understand the properties of the matter created in heavy-ion collisions at the kinetic freeze-out stage.
PubDate: Sun, 14 Jun 2015 08:53:21 +000
- Pion Transverse Momentum Spectrum, Elliptic Flow, and Interferometry in
the Granular Source Model for RHIC and LHC Heavy Ion Collisions
Abstract: We systematically investigate the pion transverse momentum spectrum, elliptic flow, and Hanbury-Brown-Twiss (HBT) interferometry in the granular source model for the heavy ion collisions of Au-Au at GeV and Pb-Pb at TeV with different centralities. The granular source model can well reproduce the experimental results of the heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). We examine the parameters involved in the granular source model. The experimental data of the momentum spectrum, elliptic flow, and HBT radii for the two collision energies and different centralities impose very strict constraints on the model parameters. They exhibit certain regularities for collision centrality and energy. The space-time structure and expansion velocities of the granular sources for the heavy ion collisions at the RHIC and LHC energies with different centralities are investigated.
PubDate: Wed, 10 Jun 2015 13:29:39 +000
- Recognizing Critical Behavior amidst Minijets at the Large Hadron Collider
Abstract: The transition from quarks to hadrons in a heavy-ion collision at high energy is usually studied in two different contexts that involve very different transverse scales: local and nonlocal. Models that are concerned with the spectra and azimuthal anisotropy belong to the former, that is, hadronization at a local point in space, such as the recombination model. The nonlocal problem has to do with quark-hadron phase transition where collective behavior through near-neighbor interaction can generate patterns of varying sizes in the space. The two types of problems are put together in this paper both as brief reviews separately and to discuss how they are related to each other. In particular, we ask how minijets produced at LHC can affect the investigation of multiplicity fluctuations as signals of critical behavior. It is suggested that the existing data from LHC have sufficient multiplicities in small intervals to make the observation of distinctive features of clustering of soft particles, as well as voids, feasible that characterize the critical behavior at phase transition from quarks to hadrons, without any ambiguity posed by the clustering of jet particles.
PubDate: Wed, 10 Jun 2015 09:39:07 +000
- The Unified Hydrodynamics and the Pseudorapidity Distributions in Heavy
Ion Collisions at BNL-RHIC and CERN-LHC Energies
Abstract: The charged particles produced in nucleus-nucleus collisions are divided into two parts. One is from the hot and dense matter created in collisions. The other is from leading particles. The hot and dense matter is assumed to expand according to unified hydrodynamics and freezes out into charged particles from a space-like hypersurface with a fixed proper time of . The leading particles are conventionally taken as the particles which inherit the quantum numbers of colliding nucleons and carry off most of incident energy. The rapidity distributions of the charged particles from these two parts are formulated analytically, and a comparison is made between the theoretical results and the experimental measurements performed in Au-Au and Pb-Pb collisions at the respective BNL-RHIC and CERN-LHC energies. The theoretical results are well consistent with experimental data.
PubDate: Wed, 10 Jun 2015 07:03:54 +000
- Transverse Momentum Spectra of and at Midrapidity in + Au, Cu + Cu, and
Collisions at GeV
Abstract: We analyze transverse momentum spectra of and at midrapidity in + Au, Cu + Cu, and collisions at GeV in the formworks of Tsallis statistics and Boltzmann statistics, respectively. Both of them can describe the transverse momentum spectra and extract the thermodynamics parameters of matter evolution in the collisions. The parameters are helpful for us to understand the thermodynamics factors of the particle production.
PubDate: Tue, 09 Jun 2015 17:06:15 +000
- Properties of Full Jet in High-Energy Heavy-Ion Collisions from Parton
Abstract: The properties of fully reconstructed jet are investigated in p + p and Pb + Pb collisions at = 2.76 TeV within a multiphase transport (AMPT) model with both partonic scatterings and hadronic rescatterings. A large transverse momentum () asymmetry of dijet or photon-jet arises from the strong interactions between jet and partonic matter. The -dependent jet fragmentation function in Pb + Pb collisions is decomposed into two contributions from different jet hadronization mechanisms, that is, fragmentation versus coalescence. The medium modification of differential jet shape displays that the jet energy is redistributed towards a larger radius owing to jet-medium interactions in heavy-ion collisions. Jet triangular azimuthal anisotropy coefficient, , which shows a smaller magnitude than the elliptic coefficient , decreases more quickly with increasing jet , which can be attributed to a path-length effect of jet energy loss. All of these properties of full jet are consistent with the jet energy loss mechanism in a stronglyinteracting partonic matter in high-energy heavy-ion collisions.
PubDate: Tue, 09 Jun 2015 14:26:03 +000
- Azimuthally Integrated HBT Parameters for Charged Pions in Nucleus-Nucleus
Interactions versus Collision Energy
Abstract: The energy dependence of spatiotemporal characteristics of particle emission region is studied for charged pions produced in nuclear collisions. No dramatic change is observed for the HBT parameters with increasing of the center-of-mass (c.m.) energy per nucleon-nucleon pair, , for of a few GeV to a few TeV. The emission duration is obtained to be almost independent of the c.m. energy within the measurement uncertainties. The analytic function is suggested for a smooth approximation of the energy dependence of the main HBT parameters. The fits demonstrate reasonable agreement with the experimental data. Predictions are made for future LHC and FCC experiments.
PubDate: Tue, 09 Jun 2015 13:34:01 +000
- Freeze-Out Parameters in Heavy-Ion Collisions at AGS, SPS, RHIC, and LHC
Abstract: We review the chemical and kinetic freeze-out conditions in high energy heavy-ion collisions for AGS, SPS, RHIC, and LHC energies. Chemical freeze-out parameters are obtained using produced particle yields in central collisions while the corresponding kinetic freeze-out parameters are obtained using transverse momentum distributions of produced particles. For chemical freeze-out, different freeze-out scenarios are discussed such as single and double/flavor dependent freeze-out surfaces. Kinetic freeze-out parameters are obtained by doing hydrodynamic inspired blast wave fit to the transverse momentum distributions. The beam energy and centrality dependence of transverse energy per charged particle multiplicity are studied to address the constant energy per particle freeze-out criteria in heavy-ion collisions.
PubDate: Tue, 09 Jun 2015 13:33:17 +000