123445006
Status of LHAASO updates from ARGO-YBJ
Abstract The Large High Altitude Air Shower Observatory (LHAASO) is a multipurpose project with a complex detector array for high energy gamma ray and cosmic ray detection. The array of 1 km 2 is composed of five types of detectors to measure shower arrival direction, total number of secondary particles, muon content, Cherenkov image and high energy gamma rays near shower core, respectively. The main scientific goals are (1) searching for galactic cosmic ray origins by extensive spectroscopy investigations of gamma ray sources above 30 TeV; (2) all sky survey for gamma ray sources at energies higher than 300 GeV; (3) energy spectrum and composition measurements of cosmic rays over a wide range covering knees with fixed energy scale and known fluxes for all species at the low energy end. In this paper, the progress on relevant detector developments is reported, including constructions of prototype detectors at Tibet site and coincidence operation with the ARGO-YBJ resistive plat chamber full coverage array at 4300 m a.s.l. The energy spectrum of cosmic ray hydrogen and Helium nuclei up to 0.8 PeV is reported as the first piece of physics measurements by the LHAASO experiment.
119160554
THE ARGO-YBJ EXPERIMENT PROGRESSES AND FUTURE EXTENSION
Gamma ray source detection above 30 TeV is an encouraging approach for finding galactic cosmic ray origins. All sky survey for gamma ray sources using wide field of view detector is essential for population accumulation for various types of sources above 100 GeV. To target the goals, the ARGO-YBJ experiment has been established. Significant progresses have been made in the experiment. A large air shower detector array in an area of 1 km2 is proposed to boost the sensitivity. Hybrid detections with multi-techniques will allow a good discrimination between different types of primary particles, including photons and protons, thus enable an energy spectrum measurement for individual species. Fluorescence light detector array will extend the spectrum measurement to 100 PeV and higher where the second knee is located. An energy scale determined by balloon experiments at 10 TeV will be propagated to ultra high energy cosmic ray experiments.
119533729
Color mutation model of soft interaction in high energy hadronic collisions
A comprehensive model, called ECOMB (eikonal color mutation branching), is proposed to describe multiparticle production by soft interaction. It incorporates the eikonal formalism, parton model, color mutation, branching, and recombination. The physics is conceptually opposite to the dynamics that underlies the fragmentation of a string. The partons are present initially in an hadronic collision; they form a single, large, color-neutral cluster until color mutation of the quarks leads to a fission of the cluster into two color-neutral subclusters. The mutation and branching processes continue until only q{bar q} pairs are left in each small cluster. The model contains self-similar dynamics and exhibits scaling behavior in the factorial moments. It can satisfactorily reproduce the intermittency data that no other model has been able to fit. {copyright} {ital 1999} {ital The American Physical Society}
7826756
Fluctuations and entropy indices of QCD parton showers.
The branching processes in parton showers are studied in perturbative QCD for both quark and gluon jets. The emphasis is on the nature of fluctuations of both the parton multiplicities and the spatial patterns of the final states. Effective measures of such fluctuations are calculated from the data obtained by Monte Carlo simulations. The entropy indices are used to characterize chaoticity. Both running and fixed couplings are considered. The fixed coupling case is used to study the onset of chaos. Implications of the results are discussed. {copyright} {ital 1996 The American Physical Society.}
119433367
The Composition of Cosmic Rays at the Knee
The observation of a small change in spectral slope, or knee in the fluxes of cosmic rays near energies 10 15 eV has caused much speculation since its discovery over 40 years ago. The origin of this feature remains unknown. A small workshop to review some modern experimental measurements of this region was held at the Adler Planetarium in Chicago, USA in June 2000. This paper summarizes the results presented at this workshop and the discussion of their interpretation in the context of hadronic models of atmospheric air showers. 2002 Elsevier Science B.V. All rights reserved.
123063882
Direct evidence of the interplanetary magnetic field effect on the cosmic ray shadow by the sun
The Tibet air-shower array, being successively operated at an altitude of 4300 m above sea level since 1990, has detected the shadows of the Sun and Moon in the 10 TeV cosmic-ray flux. In particular, the shadow of the Sun was observed in the direction significantly away from the apparent solar position, under the influence of the solar and interplanetary magnetic fields. A further analysis shows that the shadows by cosmic rays coming from the away and toward field sectors in the interplanetary space are shifted in opposite directions to one another according to the polarity of the fields. This is the first direct observation of the influence of the interplanetary magnetic field on the shadow's displacement
118380186
Numerical evolution of multiple black holes with accurate initial data
We present numerical evolutions of three equal-mass black holes using the moving puncture approach. We calculate puncture initial data for three black holes solving the constraint equations by means of a high-order multigrid elliptic solver. Using these initial data, we show the results for three black hole evolutions with sixth-order waveform convergence. We compare results obtained with the BAM and AMSS- N C KU codes with previous results. The approximate analytic solution to the Hamiltonian constraint used in previous simulations of three black holes leads to different dynamics and waveforms. We present some numerical experiments showing the evolution of four black holes and the resulting gravitational waveform.
119209594
Constructing EOB dynamics with numerical energy flux for intermediate-mass-ratio inspirals
A new scheme for computing dynamical evolutions and gravitational radiations for intermediatemass-ratio inspirals (IMRIs) based on an effective one-body (EOB) dynamics plus Teukolsky perturbation theory is built in this paper. In the EOB framework, the dynamics essentially affects the resulted gravitational waveform for binary compact star system. This dynamics includes two parts. One is the conservative part which comes from effective one-body reduction. The other part is the gravitational back reaction which contributes to the shrinking process of the inspiral of binary compact star system. Previous works used analytical waveform to construct this back reaction term. Since the analytical form is based on post-Newtonian expansion, the consistency of this term is always checked by numerical energy flux. Here we directly use numerical energy flux by solving the Teukolsky equation via the frequency-domain method to construct this back reaction term. And the conservative correction to the leading order terms in mass-ratio is included in the deformed-Kerr metric and the EOB Hamiltonian. We try to use this method to simulate not only quasi-circular adiabatic inspiral but also the nonadiabatic plunge phase. For several different spinning black holes, we demonstrate and compare the resulted dynamical evolutions and gravitational waveforms.
122607999
From binary black hole simulation to triple black hole simulation
Black hole systems are among the most promising sources for a gravitational wave detection project. Now, China is planning to construct a space-based laser interferometric detector as a follow-on mission of LISA in the near future. Aiming to provide some theoretical support to this detection project on the numerical relativity side, we focus on black hole systems simulation in this work. Considering the globular galaxy, multiple black hole systems also likely to exist in our universe and play a role as a source for the gravitational wave detector we are considering. We will give a progress report in this paper on our black hole system simulation. More specifically, we will present triple black hole simulation together with binary black hole simulation. On triple black hole simulations, one novel perturbational method is proposed.
8231444
Hawking Radiation from Spherically Symmetrical Gravitational Collapse to an Extremal R-N Black Hole for a Charged Scalar Field*
Si-Jie Gao has recently investigated Hawking radiation from spherically symmetrical gravitational collapse to an extremal R-N black hole for a real scalar field. Especially he estimated the upper bound for the expected number of particles in any wave packet belonging to H-out spontaneously produced from the state \0>(in), which confirms the traditional belief that extremal black holes do not radiate particles. Making some modifications, we demonstrate that the analysis can go through for a charged scalar field.
120027918
SPIN EXPANSION FOR HEAD-ON COLLISION OF TWO BLACK HOLES
The spin expansion technique proposed in [L. Boyel, M. Kesden and S. Nissanke, Phys. Rev. Lett.100 (2008) 151101] is very powerful to analyze the relation between the initial state of binary black hole and the final state of the merged black hole. But this technique needs orbital angular momentum to determine the third direction of a triad. Without this triad we cannot get the decomposed components of the involved quantities, and the spin expansion breaks down. The head-on collision of two black holes, whose orbital angular momentum vanishes, falls into this case. In this paper we propose a new method to construct a triad for spin expansion technique. With this new method, we get the same set of equations as in the above-mentioned paper. Furthermore, we use numerical simulations to illustrate the validity of our new method for the head-on collision of two black holes.