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In this paper, we describe the design, construction and performance of an apparatus installed in the Aberdeen Tunnel laboratory in Hong Kong for studying spallation neutrons induced by cosmic-ray muons under a vertical rock overburden of 611 meter water equivalent (m.w.e.). The apparatus comprises of six horizontal layers of plastic-scintillator hodoscopes for determining the direction and position of the incident cosmic-ray muons. Sandwiched between the hodoscope planes is a neutron detector filled with 650 kg of liquid scintillator doped with about 0.06% of Gadolinium by weight for improving the efficiency of detecting the spallation neutrons. Performance of the apparatus is also presented.

We report an improved measurement of the neutrino mixing angle $\theta_{13}$ from the Daya Bay Reactor Neutrino Experiment. We exclude a zero value for $\sin^22\theta_{13}$ with a significance of 7.7 standard deviations. Electron antineutrinos from six reactors of 2.9 GW$_{\rm th}$ were detected in six antineutrino detectors deployed in two near (flux-weighted baselines of 470 m and 576 m) and one far (1648 m) underground experimental halls. Using 139 days of data, 28909 (205308) electron antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to the expected number of antineutrinos assuming no oscillations at the far hall is $0.944\pm 0.007({\rm stat.}) \pm 0.003({\rm syst.})$. An analysis of the relative rates in six detectors finds $\sin^22\theta_{13}=0.089\pm 0.010({\rm stat.})\pm0.005({\rm syst.})$ in a three-neutrino framework., Comment: 21 pages, 24 figures. Submitted to and accepted by Chinese Physics C. Two typos were corrected. Description improved

The Daya Bay Reactor Neutrino Experiment has measured a non-zero value for the neutrino mixing angle $\theta_{13}$ with a significance of 5.2 standard deviations. Antineutrinos from six 2.9 GW$_{\rm th}$ reactors were detected in six antineutrino detectors deployed in two near (flux-weighted baseline 470 m and 576 m) and one far (1648 m) underground experimental halls. With a 43,000 ton-GW_{\rm th}-day livetime exposure in 55 days, 10416 (80376) electron antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to expected number of antineutrinos at the far hall is $R=0.940\pm 0.011({\rm stat}) \pm 0.004({\rm syst})$. A rate-only analysis finds $\sin^22\theta_{13}=0.092\pm 0.016({\rm stat})\pm0.005({\rm syst})$ in a three-neutrino framework., Comment: 5 figures. Version to appear in Phys. Rev. Lett

The Daya Bay Reactor Neutrino Experiment is designed to determine precisely the neutrino mixing angle $\theta_{13}$ with a sensitivity better than 0.01 in the parameter sin$^22\theta_{13}$ at the 90% confidence level. To achieve this goal, the collaboration will build eight functionally identical antineutrino detectors. The first two detectors have been constructed, installed and commissioned in Experimental Hall 1, with steady data-taking beginning September 23, 2011. A comparison of the data collected over the subsequent three months indicates that the detectors are functionally identical, and that detector-related systematic uncertainties exceed requirements., Comment: 24 pages, 36 figures

An energy-minimal simulation is proposed to study the patterns and mechanical properties of elastically crumpled wires in two dimensions. We varied the bending rigidity and stretching modulus to measure the energy allocation, size-mass exponent, and the stiffness exponent. The mass exponent is shown to be universal at value $D_{M}=1.33$. We also found that the stiffness exponent $\alpha =-0.25$ is universal, but varies with the plasticity parameters $s$ and $\theta_{p}$. These numerical findings agree excellently with the experimental results.

A pressure chamber is designed to study the crumpling process under an ambient force. The compression force and its resulting radius for the ball obey a power law with an exponent that is independent of the thickness and initial size of the sheet. However, the exponent is found to be material-dependent and less than the universal value, 0.25, claimed by the previous simulations. The power law behavior disappears at high pressure when the compressibility drops discontinuously, which is suggestive of a jammed state.

The Hele-Shaw experiment is performed with a circular invasion to study the scaling and dynamic behavior of the interface. We did not find any universal power law. The time exponent varies with the range of scale, as has been reported in the literature but not captured by existing models. We ascribe this distinct difference from the planar injection to the fact that our interface size grows with time. This renders the old geometries being constantly pushed apart to leave rooms for new features. As a result, the amplitude of the interface spectrum will decrease with the angular momentum, different from that of a white noise commonly assumed for the planar injection. Due to the moving boundary, the existing Kardar-Parisi-Zhang and Edwards-Wilkinson (EW) equations can no longer be applied. We propose a modified EW equation that not only conserves the fluid volume, but is also capable of predicting all the above features. Two phenomenological coefficients are introduced to represent the competing trend of instability and smoothness. Their dependence on the microscopic parameters are determined from dimensional arguments, and their estimated values conform with the experiments., Comment: 6 pages, 6 figures

We analysis the radial equations for massive Dirac fields in Schwarzschild black hole spacetimes. Different approximation formulae under the WKB scheme are developed for the transmission probability ${\cal T}$ of the radial wavefunction with $E^{2}\gg V_{m}$, $E^{2}\approx V_{m}$, and $E^{2}\ll V_{m}$, where $E$ is the energy of the field and $V_{m}$ is the maximum value of the effective potential. Explicit results of ${\cal T}$ in these approximations are given for various values of $E$, the mass $m$, and the angular momentum parameter $\kappa$ of the fields. We also discuss the dependence of ${\cal T}$ on these parameters., Comment: 21 pages, 8 figures

In this paper, we report an experimental realization of quantum switch using nuclear spins and magnetic resonant pulses. The nuclear spins of H and C in carbon-13 labelled chloroform are used to carry the information, then nuclear magnetic resonance pulses are applied to perform either bypass or cross function to achieve the switching. Compared with a traditional space or time domain switch, this switching architecture is much more scalable, therefore a high throughput switching device can be built simply by increasing the number of I/O ports. In addition, it can be used not only as a device to switch classical information, but also a building block of quantum information networks., Comment: 4 pages, 5 figures, LaTex, IEEEims.cls

The effect of quenched disorder on the low-energy and low-temperature properties of various two- and three-dimensional Heisenberg models is studied by a numerical strong disorder renormalization group method. For strong enough disorder we have identified two relevant fixed points, in which the gap exponent, omega, describing the low-energy tail of the gap distribution, P(Delta) ~ Delta^omega is independent of disorder, the strength of couplings and the value of the spin. The dynamical behavior of non-frustrated random antiferromagnetic models is controlled by a singlet-like fixed point, whereas for frustrated models the fixed point corresponds to a large spin formation and the gap exponent is given by omega ~ 0. Another type of universality classes is observed at quantum critical points and in dimerized phases but no infinite randomness behavior is found, in contrast to one-dimensional models., Comment: 11 pages RevTeX, eps-figs included, language revised

The effect of quenched disorder on the low-energy properties of various antiferromagnetic spin ladder models is studied by a numerical strong disorder renormalization group method and by density matrix renormalization. For strong enough disorder the originally gapped phases with finite topological or dimer order become gapless. In these quantum Griffiths phases the scaling of the energy, as well as the singularities in the dynamical quantities are characterized by a finite dynamical exponent, z, which varies with the strength of disorder. At the phase boundaries, separating topologically distinct Griffiths phases the singular behavior of the disordered ladders is generally controlled by an infinite randomness fixed point., Comment: 11 pages, 15 figures, PRB accepted for publication

Light curves of 3C 279 are presented in optical (R-band), X-rays (RXTE/PCA), and gamma rays (CGRO/EGRET) for 1999 Jan-Feb and 2000 Jan-Mar. During both of those epochs the gamma-ray levels were high, and all three observed bands demonstrated substantial variation, on time scales as short as one day. Correlation analyses provided no consistent pattern, although a rather significant optical/gamma-ray correlation was seen in 1999, with a gamma-ray lag of ~2.5 days, and there are other suggestions of correlations in the light curves. For comparison, correlation analysis is also presented for the gamma-ray and X-ray light curves during the large gamma ray flare in 1996 Feb and the two gamma-bright weeks leading up to it; the correlation at that time was strong, with a gamma-ray/X-ray offset of no more than 1 day., Comment: 20 pages, including 7 figures; accepted by The Astrophysical Journal

We study the critical behavior of Ising quantum magnets with broadly distributed random couplings (J), such that $P(\ln J) \sim |\ln J|^{-1-\alpha}$, $\alpha>1$, for large $|\ln J|$ (L\'evy flight statistics). For sufficiently broad distributions, $\alpha<\alpha_c$, the critical behavior is controlled by a line of fixed points, where the critical exponents vary with the L\'evy index, $\alpha$. In one dimension, with $\alpha_c=2$, we obtaind several exact results through a mapping to surviving Riemann walks. In two dimensions the varying critical exponents have been calculated by a numerical implementation of the Ma-Dasgupta-Hu renormalization group method leading to $\alpha_c \approx 4.5$. Thus in the region $2<\alpha<\alpha_c$, where the central limit theorem holds for $|\ln J|$ the broadness of the distribution is relevant for the 2d quantum Ising model., Comment: 10pages, 13figures, final form

The quantum critical behavior and the Griffiths-McCoy singularities of random quantum Ising ferromagnets are studied by applying a numerical implementation of the Ma-Dasgupta-Hu renormalization group scheme. We check the procedure for the analytically tractable one-dimensional case and apply our code to the quasi-one-dimensional double chain. For the latter we obtain identical critical exponents as for the simple chain implying the same universality class. Then we apply the method to the two-dimensional case for which we get estimates for the exponents that are compatible with a recent study in the same spirit., Comment: 10 pages LaTeX, eps-figures and PTP-macros included. Proceedings of the ICCP5, Kanazawa (Japan), 1999

In current theoretical models of the blazar subclass of active galaxies, the broadband emission consists of two components: a low-frequency synchrotron component with a peak in the IR to X-ray band, and a high-frequency inverse Compton component with a peak in the gamma-ray band. In such models, the gamma-ray spectral index should be correlated with the location of the low-energy peak, with flatter gamma-ray spectra expected for blazars with synchrotron peaks at higher photon energies and vice versa. Using the EGRET-detected blazars as a sample, we examine this correlation and possible uncertainties in its construction., Comment: 17 pages including 1 figure, accepted for publication in The Astrophysical Journal

A beam test of GLAST (Gamma-ray Large Area Space Telescope) components was performed at the Stanford Linear Accelerator Center in October, 1997. These beam test components were simple versions of the planned flight hardware. Results on the performance of the tracker, calorimeter, and anti-coincidence charged particle veto are presented., Comment: 39 pages, 21 figures

We examine the constraints imposed by reparametrization invariance on heavy-baryon chiral perturbation theory (HBChPT). We study the case of 3 flavors and consider both the strong and weak ($|\Delta S| =1$) interaction sector. Some of the parameters in the HBChPT Lagrangian are fixed as a consequence of reparametrization invariance. We discuss the consequences for the calculation of hyperon weak radiative decays in HBChPT., Comment: 8 pages, Latex, no figures

We calculate long distance contributions to $K\to\pi\nu\bar{\nu}\,,\ \pi\pi\nu\bar{\nu}$, and $\pi\pi\pi\nu\bar{\nu}$ modes within the framework of chiral perturbation theory. We find that these contributions to decay rates of $K\to \pi\nu\bar{\nu}$ and $K\to \pi\pi\nu\bar{\nu}$ in the chiral logarithmic approximation are at least seven orders of magnitude suppressed relative to those from the short distance parts. The long distance effects in this class of decays are therefore negligible., Comment: 13 pages, LaTeX file

We show that the magnetic moments of the octet baryons can be fitted to an accuracy of 1.5 percent by a phenomenological Lagrangian in which SU(3) breaking corrections appear only linearly. This is in contrast to conventional chiral perturbation theory in which corrections non-analytic in SU(3) breaking dominate and tend to spoil the agreement with the data. Motivated by this observation, we propose a modified scheme for chiral perturbation theory that gives rise to a similar linear breaking of SU(3) symmetry. (Pacs 13.40.Em, 14.20.-c, 11.30.Rd), Comment: 7 pages of Latex, no figures, version to be published in Chin. J. Phys. (Taipei) (1997)

We investigate the leading-order amplitudes for weak radiative decays of hyperons in chiral perturbation theory. We consistently include contributions from the next-to-leading order weak-interaction Lagrangian. It is shown that due to these terms Hara's theorem is violated. The data for the decays of charged hyperons can be easily accounted for. However, at this order in the chiral expansion, the four amplitudes for the decays of neutral hyperons satisfy relations which are in disagreement with the data. The asymmetry parameters for all the decays can not be accounted for without higher-order terms. We shortly comment on the effect of the 27-plet part of the weak interaction., Comment: 8 pages of REVTeX and using macro-package "feynman.tex" (available at http://xxx.lanl.gov/ftp/hep-ph/papers/macros) for the 2 figures

We study the long distance contribution to $K^+\to\pi^+\nu\bar{\nu$ by using chiral perturbation theory. We find that the tree level $O(P^2)$ contribution vanishes identically without assuming the large $N_c$ limit. The leading contribution arises from the one-loop amplitude, which is $O(P^4)$ in the chiral power counting. The branching ratio of the long distance contribution is found to be of order $10^{-7}$ smaller compared with that of short distance one and hence is completely negligible., Comment: 8 pages, LaTeX file

We derive the vertices of five-meson and seven-meson anomaly processes from the four dimensional expansion form of Wess-Zumino term. Using these vertices we calculate the amplitude, both the finite part and divergent part, of {$K^+ K^- \rightarrow \pi^0 \pi^+ \pi^-$} to one loop and renormalize the lagrangian. The divergent part agrees with the result derived from path integral approach. Contribution from counter terms is estimated by using the vector meson dominance model. Test of the vertex in the $t$-channel of $K^- P\rightarrow\Sigma^0\pi^0\pi^+\pi^-$ near the threshold is discussed. We find that the amplitudes arising from chiral loop and counter terms are of opposite sign and the counter term amplitude is about twice the loop amplitude., Comment: 13 pages, latex, 7 figures unencoded and can be obtained by request

We examine the general lagrangian for baryon chiral perturbation theory with SU(3) flavor symmetry, up to the next-to-leading order. We consider both the strong and the weak interaction. The inverse of the baryon mass is treated as an additional small expansion parameter, and heavy fermion effective field theory techniques are employed to provide a consistent expansion scheme. A detailed account is given on the restrictions imposed on the lagrangian by the various symmetries. Corrections due to the finite baryon mass are also discussed., Comment: 9 pages LaTeX. Requires REVTeX macro package. No figures

Motivated by the observation of the decay $\bar{B}\to \bar{K}^*\gamma$ by CLEO, we have systematically analyzed the two-body weak radiative decays of bottom and charmed hadrons. There exist two types of weak radiative decays: One proceeds through the short-distance $b\to s\gamma$ transition and the other occurs through $W$-exchange accompanied by a photon emission. Effective Lagrangians are derived for the $W$-exchange bremsstrahlung processes at the quark level and then applied to various weak electromagnetic decays of heavy hadrons. Predictions for the branching ratios of $\bar{B}^0\to D^{*0} \gamma,~\Lambda_b^0\to\Sigma_c^0\gamma,~\Xi_b^0\to \Xi_c^0\gamma$ and $\Xi_b^0\to\xip_c^0\gamma$ are given. In particular, we found ${\cal B}(\bar{B}^0 \to D^{*0}\gamma)\approx 0.9\times 10^{-6}$. Order of magnitude estimates for the weak radiative decays of charmed hadrons: $~D^0\to \bar{K}^{*0}\gamma,~\Lambda_c^+\to\Sigma^+\gamma$ and $\Xi_c^0\to\Xi^0\gamma$ are also presented. Within this approach, the decay asymmetry for antitriplet to antitriplet heavy baryon weak radiative transitions is uniquely predicted by heavy quark symmetry. The electromagnetic penguin contribution to $\Lambda_b^0\to\Lambda\gamma$ is estimated by two different methods and its branching ratio is found to be of order $1\times 10^{-5}$. We conclude that weak radiative decays of bottom hadrons are dominated by the short-distance $b\to s\gamma$ mechanism., Comment: 28 pages + 3 figures (not included), CLNS 94/1278, IP-ASTP-04-94. [Main changes in this revised version: (i) Sect 2 and subsection 4.1 are revised, (ii) A MIT bag method for calculating the decay rate of $Lambda_b \to\Lambda+gamma$ is presented, (iii) All predictions are updated using the newly available 1994 Particle Data Group, and (iv) Appendix and subsections 3.3 and 4.4 are deleted.]

We give the amplitude for $\gamma\gamma \rightarrow \pi^+\pi^-\pi^0$ in leading order chiral perturbation theory. For the case of real photons we calculate the total and differential cross section. Furthermore, we give the dependence of the total cross section on the invariant mass of one of the photons., Comment: 8 pages LaTeX with Feynman.tex (2 postscript figures in separate file), NCUHEP 94-04

We study both CP conserving and violating contributions to the decay $K_L\to\pi^+\pi^-\nu\bar{\nu}$. We find that the decay branching ratio is dominated by the CP conserving part. In the standard CKM model, we estimate that for $m_t\sim 174\ GeV$, the branching ratio due to the CP conserving (violating) contributions can be as large as $4.4 \times 10^{-13}$ ($1.0\times 10^{-14}$)., Comment: 15 pages (LaTex), 3 figures (not included), NHCU-HEP-94-04

In previous publications we have analyzed the strong and electromagnetic decays of heavy mesons and heavy baryons in a formalism which incorporates heavy-quark and chiral symmetries. There are two possible symmetry-breaking effects on the chiral dynamics of heavy hadrons: the finite-mass effects from light quarks and the $1/ m_Q$ corrections from heavy quarks. In the present paper, chiral-symmetry-breaking effects are studied and applications to various strong and radiative decays of heavy hadrons are illustrated. SU(3) violations induced by chiral loops in the radiative decays of charmed mesons and charmed baryons are compared with those predicted by the constituent quark model. In particular, available data for $D^*$ decays favor values of the parameters in chiral perturbation theory which give predictions for $D^*$ decays close to the quark model results except for the $D^{*+}_s$. Implications are discussed., Comment: PHYZZX, 56 pages and 8 figures (available upon request), CLNS 93/1189, IP-ASTP-01-93

In earlier publications we have analyzed the strong and radiative decays of heavy hadrons in a formalism which incorporates both heavy-quark and chiral symmetries. In particular, we have derived a heavy-hadron chiral Lagrangian whose coupling constants are related by the heavy-quark flavor-spin symmetry arising from the QCD Lagrangian with infinitely massive quarks. In this paper, we re-examine the structure of the above chiral Lagrangian by including the effects of $1/m_Q$ corrections in the heavy quark effective theory. The relations among the coupling constants, originally derived in the heavy-quark limit, are modified by heavy quark symmetry breaking interactions in QCD. Some of the implications are discussed., Comment: PHYZZX, 45 pages, 1 figure (not included), CLNS 93/1192, IP-ASTP-02-93, ITP-SB-93-04

We study in detail the prediction for the semileptonic decays $\bar{B} \to D (D^*) \pi \ell \bar{\nu}$ by heavy quark and chiral symmetry. The branching ratio for $\bar{B} \to D \pi \ell \bar{\nu}$ is quite significant, as big as $(0.5-1)\%$. The branching ratio for $\bar{B} \to D^* \pi \ell \bar{\nu}$ is only of order $10^{-4}-10^{-5}$. Numerical results for various single particle spectra and their dependence on the pion momentum cutoff schemes are presented in a series of figures, as are the model independent ratios for differential rates of $D$ and $D^*$. We also study the parity-violation effects on the decay rates for different polarization states of the $D^*$. Figures may be obtained by anonymous FTP from strange.tn.cornell.edu in the directory pub/CLNS931204, or by email from the author., Comment: 28 pages, 23 figs (FTP from author), LaTeX, Typos corrected in Eq. 4.9c (factor of 2), Eq. A.4, and Tables II & III. No change in content, results, or figures. CLNS93/1204, IP-ASTP-15-93

The radiative decays of heavy mesons and heavy baryons are studied in a formalism which incorporates both the heavy quark symmetry and the chiral symmetry. The chiral Lagrangians for the electromagnetic interactions of heavy hadrons consist of two pieces: one from gauging electromagnetically the strong-interaction chiral Lagrangian, and the other from the anomalous magnetic moment interactions of the heavy baryons and mesons. Due to the heavy quark spin symmetry, the latter contains only one independent coupling constant in the meson sector and two in the baryon sector. These coupling constants only depend on the light quarks and can be calculated in the nonrelativistic quark model. However, the charm quark is not heavy enough and the contribution from its magnetic moment must be included. Applications to the radiative decays $D^\ast \rightarrow D \gamma~,~B^\ast \rightarrow B \gamma~,~ \Xi^\prime_c \rightarrow \Xi_c \gamma~, \Sigma_c \rightarrow \Lambda_c \gamma$ and $\Sigma_c \rightarrow \Lambda_c \pi \gamma$ are given. Together with our previous results on the strong decay rates of $D^\ast \rightarrow D \pi$ and $\Sigma_c \rightarrow \Lambda_c \pi$, predictions are obtained for the total widths and branching ratios of $D^\ast$ and $\Sigma_c$. The decays $\Sigma^+_c \rightarrow \Lambda^+_c \pi^0 \gamma $ and $\Sigma^0_c \rightarrow \Lambda^+_c \pi^- \gamma $ are discussed to illustrate the important roles played by both the heavy quark symmetry and the chiral symmetry., Comment: 30 pages (one figure, available on request), CLNS 92/1158 and IP-ASTP-13-92