Pionic couplings to the lowest heavy-light mesons of positive and negative parity

We present the method and compute the strong couplings of the lowest and first orbitally excited heavy-light mesons to a soft pion in the static heavy quark limit on the lattice. Besides the usual g^ and \~g couplings, we were able to make the first computation of the coupling h using the relevant radial distributions. Our results are obtained from the simulations of QCD with Nf=2 light Wilson-Clover quarks, combined with the improved static quark actions. The hierarchy among couplings that emerges from our study is \~g < g^ < h.Comment: 22 pages, 6 figure

Design, implementation and evaluation of a QoS-aware transport protocol

In the context of a reconfigurable transport protocol framework, we propose a QoS-aware Transport Protocol (QSTP), specifically designed to operate over QoS-enabled networks with bandwidth guarantee. QSTP combines QoS-aware TFRC congestion control mechanism, which takes into account the network-level bandwidth reservations, with a Selective ACKnowledgment (SACK) mechanism in order to provide a QoS-aware transport service that fill the gap between QoS enabled network services and QoS constraint applications. We have developed a prototype of this protocol in the user-space and conducted a large range of measurements to evaluate this proposal under various network conditions. Our results show that QSTP allows applications to reach their negotiated QoS over bandwidth guaranteed networks, such as DiffServ/AF network, where TCP fails. This protocol appears to be the first reliable protocol especially designed for QoS network architectures with bandwidth guarantee

The effect of in-plane magnetic field on the spin Hall effect in Rashba-Dresselhaus system

In a two-dimensional electron gas with Rashba and Dresselhaus spin-orbit couplings, there are two spin-split energy surfaces connected with a degenerate point. Both the energy surfaces and the topology of the Fermi surfaces can be varied by an in-plane magnetic field. We find that, if the chemical potential falls between the bottom of the upper band and the degenerate point, then simply by changing the direction of the magnetic field, the magnitude of the spin Hall conductivity can be varied by about 100 percent. Once the chemical potential is above the degenerate point, the spin Hall conductivity becomes the constant $e/8\pi$, independent of the magnitude and direction of the magnetic field. In addition, we find that the in-plane magnetic field exerts no influence on the charge Hall conductivity.Comment: 11 pages, 3 figures, to be published on Phys. Rev.

The Magnetic Structure of Light Nuclei from Lattice QCD

Lattice QCD with background magnetic fields is used to calculate the magnetic moments and magnetic polarizabilities of the nucleons and of light nuclei with $A\le4$, along with the cross-section for the $M1$ transition $np\rightarrow d\gamma$, at the flavor SU(3)-symmetric point where the pion mass is $m_\pi\sim 806$ MeV. These magnetic properties are extracted from nucleon and nuclear energies in six uniform magnetic fields of varying strengths. The magnetic moments are presented in a recent Letter. For the charged states, the extraction of the polarizability requires careful treatment of Landau levels, which enter non-trivially in the method that is employed. The nucleon polarizabilities are found to be of similar magnitude to their physical values, with $\beta_p=5.22(+0.66/-0.45)(0.23) \times 10^{-4}$ fm$^3$ and $\beta_n=1.253(+0.056/-0.067)(0.055) \times 10^{-4}$ fm$^3$, exhibiting a significant isovector component. The dineutron is bound at these heavy quark masses and its magnetic polarizability, $\beta_{nn}=1.872(+0.121/-0.113)(0.082) \times 10^{-4}$ fm$^3$ differs significantly from twice that of the neutron. A linear combination of deuteron scalar and tensor polarizabilities is determined by the energies of the $j_z=\pm 1$ deuteron states, and is found to be $\beta_{d,\pm 1}=4.4(+1.6/-1.5)(0.2) \times 10^{-4}$ fm$^3$. The magnetic polarizabilities of the three-nucleon and four-nucleon systems are found to be positive and similar in size to those of the proton, $\beta_{^{3}\rm He}=5.4(+2.2/-2.1)(0.2) \times 10^{-4}$ fm$^3$, $\beta_{^{3}\rm H}=2.6(1.7)(0.1) \times 10^{-4}$ fm$^3$, $\beta_{^{4}\rm He}=3.4(+2.0/-1.9)(0.2) \times 10^{-4}$ fm$^3$. Mixing between the $j_z=0$ deuteron state and the spin-singlet $np$ state induced by the background magnetic field is used to extract the short-distance two-nucleon counterterm, ${\bar L}_1$, of the pionless effective theory for $NN$ systems (equivalent to the meson-exchange current contribution in nuclear potential models), that dictates the cross-section for the $np\to d\gamma$ process near threshold. Combined with previous determinations of NN scattering parameters, this enables an ab initio determination of the threshold cross-section at these unphysical masses.Comment: 49 pages, 24 figure

Unitary Limit of Two-Nucleon Interactions in Strong Magnetic Fields

Two-nucleon systems are shown to exhibit large scattering lengths in strong magnetic fields at unphysical quark masses, and the trends toward the physical values indicate that such features may exist in nature. Lattice QCD calculations of the energies of one and two nucleons systems are performed at pion masses of $m_\pi\sim 450$ and 806 MeV in uniform, time-independent magnetic fields of strength {\bf B}| \sim 10^{19}$-$10^{20}$ Gauss to determine the response of these hadronic systems to large magnetic fields. Fields of this strength may exist inside magnetars and in peripheral relativistic heavy ion collisions, and the unitary behavior at large scattering lengths may have important consequences for these systems.Comment: Accepted journal versio

Ab initio calculation of the np→dγnp \to d \gamma radiative capture process

Lattice QCD calculations of two-nucleon systems are used to isolate the short-distance two-body electromagnetic contributions to the radiative capture process $np \to d\gamma$, and the photo-disintegration processes $\gamma^{(\ast)} d \to np$. In nuclear potential models, such contributions are described by phenomenological meson-exchange currents, while in the present work, they are determined directly from the quark and gluon interactions of QCD. Calculations of neutron-proton energy levels in multiple background magnetic fields are performed at two values of the quark masses, corresponding to pion masses of $m_\pi \sim 450$ and 806 MeV, and are combined with pionless nuclear effective field theory to determine these low-energy inelastic processes. Extrapolating to the physical pion mass, a cross section of $\sigma^{lqcd}(np\to d\gamma)=332.4({\tiny \begin{array}{l}+5.4 \\ - 4.7\end{array}})\ mb$ is obtained at an incident neutron speed of $v=2,200\ m/s$, consistent with the experimental value of$\sigma^{expt}(np \to d\gamma) = 334.2(0.5)\ mb$

Magnetic structure of light nuclei from lattice QCD

Lattice QCD with background magnetic fields is used to calculate the magnetic moments and magnetic polarizabilities of the nucleons and of light nuclei with A \u3c = 4, along with the cross section for the M1 transition np - \u3e d gamma, at the flavor SU(3)-symmetric point where the pion mass is m(pi) similar to 806 MeV. These magnetic properties are extracted from nucleon and nuclear energies in six uniform magnetic fields of varying strengths. The magnetic moments are presented in a recent article [S. Beane et al., Phys. Rev. Lett. 113, 252001 (2014)]. For the charged states, the extraction of the polarizability requires careful treatment of Landau levels, which enter nontrivially in the method that is employed. The nucleon polarizabilities are found to be of similar magnitude to their physical values, with beta(p) = 5.22((+0.66)(-0.45))(0.23) x 10(-4) fm(3) and beta(n) = 1.253((+0.056)(-0.067))(0.055) x 10(-4) fm(3), exhibiting a significant isovector component. The dineutron is bound at these heavy quark masses, and its magnetic polarizability, beta(nn) = 1.872((+0.121)(-0.113))(0.082) x 10(-4) fm(3), differs significantly from twice that of the neutron. A linear combination of deuteron scalar and tensor polarizabilities is determined by the energies of the j(z) = +/- 1 deuteron states and is found to be beta(d, +/- 1) = 4.4((+1.6)(-1.5))(0.2) x 10(-4) fm(3). The magnetic polarizabilities of the three-nucleon and four-nucleon systems are found to be positive and similar in size to those of the proton, beta(3He) = 5.4((+2.2)(-2.1))(0.2) x 10(-4) fm(3), beta(3H) = 2.6(1.7)(0.1) x 10(-4) fm(3), and beta(4He) = 3.4((+2.0)(-1.9))(0.2) x 10(-4) fm(3). Mixing between the j(z) = 0 deuteron state and the spin-singlet np state induced by the background magnetic field is used to extract the short-distance two-nucleon counterterm, (L) over bar (1), of the pionless effective theory for NN systems (equivalent to the meson-exchange current contribution in nuclear potential models) that dictates the cross section for the np - \u3e d gamma process near threshold. Combined with previous determinations of NN scattering parameters, this enables an ab initio determination of the threshold cross section at these unphysical masses

Perturbative SO(10) Grand Unification

We consider a phenomenologically viable SO(10) grand unification model of the unification scale $M_G$ around $10^{16}$ GeV which reproduces the MSSM at low energy and allows perturbative calculations up to the Planck scale $M_P$ or the string scale $M_{st}$. Both requirements strongly restrict a choice of Higgs representations in a model. We propose a simple SO(10) model with a set of Higgs representations $\{2 \times {\bf 10} + {\bf \bar{16}} + {\bf 16} + {\bf 45} \}$ and show its phenomenological viability. This model can indeed reproduce the low-energy experimental data relating the charged fermion masses and mixings. Neutrino oscillation data can be consistently incorporated in the model, leading to the right-handed neutrino mass scale $M_R \simeq M_G^2/M_P$. Furthermore, there exists a parameter region which results the proton life time consistent with the experimental results.Comment: 14 pages, no figure, section5 was slightly modifie

Ab initio Calculation of the np -\u3e d gamma Radiative Capture Process

Lattice QCD calculations of two-nucleon systems are used to isolate the short-distance two-body electromagnetic contributions to the radiative capture process np - \u3e d gamma, and the photo-disintegration processes gamma(*)d - \u3e np. In nuclear potential models, such contributions are described by phenomenological meson-exchange currents, while in the present work, they are determined directly from the quark and gluon interactions of QCD. Calculations of neutron-proton energy levels in multiple background magnetic fields are performed at two values of the quark masses, corresponding to pion masses of m(pi) similar to 450 and 806MeV, and are combined with pionless nuclear effective field theory to determine the amplitudes for these low-energy inelastic processes. At m(pi) similar to 806 MeV, using only lattice QCD inputs, a cross section sigma(806 MeV) similar to 17 mb is found at an incident neutron speed of v = 2,200 m/s. Extrapolating the short-distance contribution to the physical pion mass and combining the result with phenomenological scattering information and one-body couplings, a cross section of sigma(lqcd)(np - \u3e d gamma) = 334.9((+5.2)(-5.4)) mb is obtained at the same incident neutron speed, consistent with the experimental value of sigma(expt)(np - \u3e d gamma) = 334.2(0.5) mb

URBAN HPAC AND A SIMPLE URBAN DISPERSION MODEL COMPARED WITH THE JOINT URBAN 2003 (JU2003) FIELD DATA

The Hazard Prediction and Assessment Capability (HPAC) dispersion model is widely used by the U.S. Department of Defense and the results of previous evaluations have been presented at Harmonization conferences. The version of its diagnostic wind model that is applied to urban areas has been significantly updated to remove biases in wind speed estimates, requiring reevaluations with urban tracer data sets such as the Joint Urban 2003 (JU2003) data base. For comparison purposes, a simple Gaussian-format urban dispersion model has been run for the same JU2003 data base. The simple urban model has previously been evaluated with the Madison Square Garden 2005 (MSG05) data. The evaluations focus on 30-minute averaged (1) arc maximum concentrations and (2) concentrations paired in space. It is shown that the revisions to the diagnostic wind model in urban HPAC have resulted in improved performance. Similar good performance is found for the simple urban dispersion model, although it has more errors for off-centerline and upwind receptors in the downtown area