arXiv subjects

X. Cai

Publications and source records attributed to X. Cai.

At least 865 records · Page 48Linked to original sources

arXiv2012

Precision measurement of the branching fractions of J/psi -> pi+pi-pi0 and psi' -> pi+pi-pi0

We study the decays of the J/psi and psi' mesons to pi+pi-pi0 using data samples at both resonances collected with the BES III detector in 2009. We measure the corresponding branching fractions with unprecedented precision and provide mass spectra and Dalitz plots. The branching fraction for J/psi -> pi+pi-pi0 is determined to be (2.137 +- 0.004 (stat.) +0.058-0.056 (syst.) +0.027-0.026 (norm.))*10-2, and the branching fraction for psi' -> pi+pi-pi0 is measured as (2.14 +- 0.03 (stat.) +0.08-0.07 (syst.) +0.09-0.08 (norm.))*10-4. The J/psi decay is found to be dominated by an intermediate rho(770) state, whereas the psi' decay is dominated by di-pion masses around 2.2 GeV/c2, leading to strikingly different Dalitz distributions.

hep-ex↗

arXiv2011

The beam energy measurement system for the Beijing electron-positron collider

The beam energy measurement system (BEMS) for the upgraded Beijing electron-positron collider BEPC-II is described. The system is based on measuring the energies of Compton back-scattered photons. The relative systematic uncertainty of the electron and positron beam energy determination is estimated as 2 \cdot 10^{-5}. The relative uncertainty of the beam's energy spread is about 6 %.

physics.acc-ph↗

arXiv2007

The forget-remember mechanism for 2-state spreading

A new mechanism, the forget-remember mechanism, is proposed for studying the spreading process in 2-state model. Such mechanism exhibits behaviors of message spreading influenced by some kinds of functions about time and history caring about the individuals of the spreading system, holding message or being out of message. To demonstrate the mechanism, both linear and exponential forms for forget-function and remember-function are simulated and show that a great impact on the saturation of message-spreading and the relative phase transformation.

nlin.AO↗

arXiv2006

A repair strategy to the attacked random and scale-free networks

With a simple attack and repair evolution model, we investigate the stability and structural changes of the Erdos-Renyi random graphs (RG) and Barabasi-Albert scale-free (SF) networks. We introduce a new quantity, invulnerability I(s), to describe the stability of the system. We find that both RG and SF networks can evolve to a stationary state. The stationary value I_c has a power-law dependence on the repair probability p_re. We also analyze the effects of the repair strategy to the attack tolerance of the networks. We observe that there is a threshold, (k_max)_c, for the maximum degree. The maximum degree k_max at time s will be no smaller than (k_max)_c. We give further information on the evolution of the networks by comparing the changes of the topological parameters, such as degree distribution P(k), average degree , shortest path length L, clustering coefficient C, assortativity r, under the initial and stationary states.

cond-mat.stat-mech↗

arXiv2005

Detrended fluctuation analysis on the correlations of complex networks under attack and repair strategy

We analyze the correlation properties of the Erdos-Renyi random graph (RG) and the Barabasi-Albert scale-free network (SF) under the attack and repair strategy with detrended fluctuation analysis (DFA). The maximum degree k_max, representing the local property of the system, shows similar scaling behaviors for random graphs and scale-free networks. The fluctuations are quite random at short time scales but display strong anticorrelation at longer time scales under the same system size N and different repair probability p_re. The average degree , revealing the statistical property of the system, exhibits completely different scaling behaviors for random graphs and scale-free networks. Random graphs display long-range power-law correlations. Scale-free networks are uncorrelated at short time scales; while anticorrelated at longer time scales and the anticorrelation becoming stronger with the increase of p_re.

cond-mat.stat-mech↗

arXiv2005

Stability of complex networks under the evolution of attack and repair

With a simple attack and repair evolution model, we investigate and compare the stability of the Erdos-Renyi random graphs (RG) and Barabasi-Albert scale-free (SF) networks. We introduce a new quantity, invulnerability I(s), to describe the stability of the system. We find that both RG and SF networks can evolve to a stationary state. The stationary value Ic has a power-law dependence on the average degree _rg for RG networks; and an exponential relationship with the repair probability p_sf for SF networks. We also discuss the topological changes of RG and SF networks between the initial and stationary states. We observe that the networks in the stationary state have smaller average degree but larger clustering coefficient C and stronger assortativity r.

cond-mat.stat-mech↗

arXiv2005

Stability in the evolution of random networks

With a simple model, we study the evolution of random networks under attack and reconstruction. We introduce a new quality, invulnerability I(s), to describe the stability of the system. We find that the network can evolve to a stationary state. The stationary value I_c has a power-law dependence on the initial average degree , with the slope is about -1.485. In the stationary state, the degree distribution is a normal distribution, rather than a typical Poisson distribution for general random graphs. The clustering coefficient in the stationary state is much larger than that in the initial state. The stability of the network depends only on the initial average degree , which increases rapidly with the decrease of .

cond-mat.dis-nn↗

arXiv2003

Statistical Analysis of Airport Network of China

Through the study of airport network of China (ANC), composed of 128 airports (nodes) and 1165 flights (edges), we show the topological structure of ANC conveys two characteristics of small worlds, a short average path length (2.067) and a high degree of clustering (0.733). The cumulative degree distributions of both directed and undirected ANC obey two-regime power laws with different exponents, i.e., the so-called Double Pareto Law. In-degrees and out-degrees of each airport have positive correlations, whereas the undirected degrees of adjacent airports have significant linear anticorrelations. It is demonstrated both weekly and daily cumulative distributions of flight weights (frequencies) of ANC have power-law tails. Besides, the weight of any given flight is proportional to the degrees of both airports at the two ends of that flight. It is also shown the diameter of each sub-cluster (consisting of an airport and all those airports to which it is linked) is inversely proportional to its density of connectivity. Efficiency of ANC and of its sub-clusters are measured through a simple definition. In terms of that, the efficiency of ANC's sub-clusters increases as the density of connectivity does. ANC is found to have an efficiency of 0.484.

cond-mat.stat-mech↗

arXiv2002

Hawking Radiation of Dirac Particles in an Arbitrarily Accelerating Kinnersley Black Hole

Quantum thermal effect of Dirac particles in an arbitrarily accelerating Kinnersley black hole is investigated by using the method of generalized tortoise coordinate transformation. Both the location and the temperature of the event horizon depend on the advanced time and the angles. The Hawking thermal radiation spectrum of Dirac particles contains a new term which represents the interaction between particles with spin and black holes with acceleration. This spin-acceleration coupling effect is absent from the thermal radiation spectrum of scalar particles.

gr-qc↗

arXiv2001

Quantum Thermal Effect of Dirac Particles in a Non-uniformly Rectilinearly Accelerating Black Hole with Electronic Charge, Magnetic Charge and Cosmological Constant

The Hawking radiation of Dirac particles in an arbitrarily rectilinearly accelerating Kinnersley black hole with electro-magnetic charge and cosmological constant is investigated by using method of the generalized tortoise coordinate transformation. Both the location and the temperature of the event horizon depend on the time and the polar angle. The Hawking thermal radiation spectrum of Dirac particles is also derived. PACS numbers: 04.70.Dy, 97.60.Lf

gr-qc↗

arXiv2001

Hawking Radiation of Photons in a Vaidya-de Sitter Black Hole

Hawking evaporation of photons in a Vaidya-de Sitter black hole is investigated by using the method of generalized tortoise coordinate transformation. Both the location and the temperature of the event horizon depend on the time. It is shown that Hawking radiation of photons exists only for the complex Maxwell scalar $ϕ_0$ in the advanced Eddington-Finkelstein coordinate system. This asymmetry of Hawking radiation for different components of Maxwell fields probably arises from the asymmetry of spacetime in the advanced Eddington-Finkelstein coordinate system. It is shown that the black body radiant spectrum of photons resembles that of Klein-Gordon particles. PACS numbers: 04.70.Dy, 97.60.Lf

gr-qc↗

arXiv2001

Hawking Radiation of a Non-stationary Kerr-Newman Black Hole: Spin-Rotation Coupling Effect

Hawking evaporation of Klein-Gordon and Dirac particles in a non-stationary Kerr-Newman space-time is investigated by using a method of generalized tortoise coordinate transformation. The location and the temperature of the event horizon of a non-stationary Kerr-Newman black hole are derived. It is shown that the temperature and the shape of the event horizon depend not only on the time but also on the angle. However, the Fermionic spectrum of Dirac particles displays a new spin-rotation coupling effect which is absent from that of Bosonic distribution of scalar particles. The character of this effect is its obvious dependence on different helicity states of particles spin-1/2. PACS numbers: 04.70.Dy, 97.60.Lf

gr-qc↗

arXiv2001

Addendum: Hawking Radiation of Photons in a Variable-mass Kerr Black Hole

Hawking evaporation of photons in a variable-mass Kerr space-time is investigated by using a method of the generalized tortoise coordinate transformation. The blackbody radiant spectrum of photons displays a new spin-rotation coupling effect obviously dependent on different helicity states of photons.

gr-qc↗

arXiv2001

No New Quantum Thermal Effect of Dirac Particles in a Charged Vaidya - de Sitter Black Hole

It is shown that Hawking radiation of Dirac particles does not exist for $P_1, Q_2$ components but for $P_2, Q_1$ components in a charged Vaidya - de Sitter black hole. Both the location and the temperature of the event horizon change with time. The thermal radiation spectrum of Dirac particles is the same as that of Klein-Gordon particles. Our result demonstrates that there is no new quantum effect in the thermal radiation of Dirac particles in any spherically symmetry black holes.

hep-th↗

arXiv2001

Non-existence of New Quantum Ergosphere Effect of a Vaidya-type Black Hole

Hawking evaporation of Dirac particles and scalar fields in a Vaidya-type black hole is investigated by the method of generalized tortoise coordinate transformation. It is shown that Hawking radiation of Dirac particles does not exist for $P_1, Q_2$ components but for $P_2, Q_1$ components in any Vaidya-type black holes. Both the location and the temperature of the event horizon change with time. The thermal radiation spectrum of Dirac particles is the same as that of Klein-Gordon particles. We demonstrates that there is no new quantum ergosphere effect in the thermal radiation of Dirac particles in any spherically symmetry black holes.

gr-qc↗

arXiv2001

Massive Complex Scalar Field in a Kerr-Sen Black Hole Background: Exact Solution of Wave Equation and Hawking Radiation

The separated radial part of a massive complex scalar wave equation in the Kerr-Sen geometry is shown to satisfy the generalized spheroidal wave equation which is, in fact, a confluent Heun equation up to a multiplier. The Hawking evaporation of scalar particles in the Kerr-Sen black hole background is investigated by the Damour-Ruffini-Sannan's method. It is shown that quantum thermal effect of the Kerr-Sen black hole has the same characteras that of the Kerr-Newman black hole.

gr-qc↗

arXiv2001

Understanding $K/π$ ratio distribution in the mixed events

The event mixing method is analyzed for the study of the event-by-event $K/π$ ratio distribution. It is shown that there exists some correlation between the kaon and pion multiplicities in the mixed events. The $K/π$ ratio distributions in the mixed events for different sets of real events are shown. The dependence of the distributions on the mean $K/π$ ratio, mean and variance of multiplicity distribution in the real events is investigated systematically. The effect of imperfect particle identification on the $K/π$ ratio distribution in the mixed event is also considered.

hep-ph↗

arXiv2001

Influence of statistical fluctuations on $K/π$ ratios in relativistic heavy ion collisions

The influence of pure statistical fluctuations on $K/π$ ratio is investigated in an event-by-event way. Poisson and the modified negative binomial distributions are used as the multiplicity distributions since they both have statistical background. It is shown that the distributions of the ratio in these cases are Gaussian, and the mean and relative variance are given analytically.

hep-ph↗