Spin-Orbit and Tensor Forces in Heavy-quark Light-quark Mesons: Implications of the New Ds state at 2.32 GeV

We consider the spectroscopy of heavy-quark light-quark mesons with a simple model based on the non-relativistic reduction of vector and scalar exchange between fermions. Four forces are induced: the spin-orbit forces on the light and heavy quark spins, the tensor force, and a spin-spin force. If the vector force is Coulombic, the spin-spin force is a contact interaction, and the tensor force and spin-orbit force on the heavy quark to order $1/m_1m_2$ are directly proportional. As a result, just two independent parameters characterize these perturbations. The measurement of the masses of three p-wave states suffices to predict the mass of the fourth. This technique is applied to the $D_s$ system, where the newly discovered state at 2.32 GeV provides the third measured level, and to the $D$ system. The mixing of the two $J^P=1^+$ p-wave states is reflected in their widths and provides additional constraints. The resulting picture is at odds with previous expectations and raises new puzzles.Comment: 6 pages, 1 figur

Changes Found on Run-In and Scuffed Surfaces of Steel Chrome Plate, and Cast Iron

A study was made of run-in and scuffed steel, chrome-plate, and cast-iron surfaces. X-ray and electron diffraction techniques, micro-hardness determinations, and microscopy were used. Surface changes varied and were found to include three classes: chemical reaction, hardening, and crystallite-size alteration. The principal chemical reactions were oxidation and carburization

Four-quark state in QCD

The spectra of some 0++ four-quark states, which are composed of \bar qq pairs, are calculated in QCD. The light four-quark states are calculated using the traditional sum rules while four-quark states containing one heavy quark are computed in HQET. For constructing the interpolating currents, different couplings of the color and spin inside the \bar qq pair are taken into account. It is found that the spin and color combination has little effect on the mass of the four-quark states.Comment: 10 pages, 4 ps figures, Late

Testing the Noncommutative Standard Model at a Future Photon Collider

Extensions of the Standard Model of elementary particle physics to noncommutative geometries have been proposed as a low energy limit of string models. Independent of this motivation, one may consider such a model as an effective field theory with higher-dimensional operators containing an antisymmetric rank-two background field. We study the signals of such a Noncommutative Standard Model (NCSM) and analyze the discovery potential of a future photon collider, considering angular distributions in fermion pair production.Comment: 13 pages RevTeX, Feynman diagrams and figures included, references added, typographical errors in Feynman rules corrected (all results remain unchangend, since correct Feynman rules were used in the calculations), to appear in Phys. Rev.

LOFAR discovery of a 700-kpc remnant radio galaxy at low redshift

Remnant radio galaxies represent the final dying phase of radio galaxy evolution, in which the jets are no longer active. Due to their rarity in flux limited samples and the difficulty of identification, this dying phase remains poorly understood and the luminosity evolution largely unconstrained. Here we present the discovery and detailed analysis of a large (700 kpc) remnant radio galaxy with a low surface brightness that has been identified in LOFAR images at 150 MHz. By combining LOFAR data with new follow-up Westerbork observations and archival data at higher frequencies, we investigated the source morphology and spectral properties from 116 to 4850 MHz. By modelling the radio spectrum we probed characteristic timescales of the radio activity. The source has a relatively smooth, diffuse, amorphous appearance together with a very weak central compact core which is associated with the host galaxy located at z=0.051. From our ageing and morphological analysis it is clear that the nuclear engine is currently switched off or, at most, active at a very low power state. The host galaxy is currently interacting with another galaxy located at a projected separation of 15 kpc and a radial velocity offset of 300 km/s. This interaction may have played a role in the triggering and/or shut down of the radio jets. The spectral shape of this remnant radio galaxy differs from the majority of the previously identified remnant sources, which show steep or curved spectra at low to intermediate frequencies. In light of this finding and in preparation for new-generation deep low-frequency surveys, we discuss the selection criteria to be used to select representative samples of these sources.Comment: 10 pages, 6 figures, 5 tables, A&A accepte

Properties of the Strange Axial Mesons in the Relativized Quark Model

We studied properties of the strange axial mesons in the relativized quark model. We calculated the $K_1$ decay constant in the quark model and showed how it can be used to extract the $K_1 (^3P_1) - K_1 (^1P_1)$ mixing angle ($\theta_K$) from the weak decay $\tau \to K_1 \nu_\tau$. The ratio $BR(\tau \to \nu_\tau K_1 (1270))/BR(\tau\to \nu_\tau K_1(1400))$ is the most sensitive measurement and also the most reliable since the largest of the theoretical uncertainties factor out. However the current bounds extracted from the TPC/Two-Gamma collaboration measurements are rather weak: we typically obtain $-30^o \lesssim \theta_K \lesssim 50^o$ at 68\% C.L. We also calculated the strong OZI-allowed decays in the pseudoscalar emission model and the flux-tube breaking model and extracted a $^3P_1 - ^1P_1$ mixing angle of $\theta_K \simeq 45^o$. Our analysis also indicates that the heavy quark limit does not give a good description of the strange mesons.Comment: Revised version to be published in Phys. Rev. D. Minor changes. Latex file uses revtex version 3 and epsfig, 4 postcript figures are attached. The full postcript version with embedded figures is available at ftp://ftp.physics.carleton.ca/pub/theory/godfrey/ocipc9512.ps.

On the Absence of an Exponential Bound in Four Dimensional Simplicial Gravity

We have studied a model which has been proposed as a regularisation for four dimensional quantum gravity. The partition function is constructed by performing a weighted sum over all triangulations of the four sphere. Using numerical simulation we find that the number of such triangulations containing $V$ simplices grows faster than exponentially with $V$. This property ensures that the model has no thermodynamic limit.Comment: 8 pages, 2 figure

Phenomenological Study of Strong Decays of Heavy Hadrons in Heavy Quark Effective Theory

The application of the tensor formalism of the heavy quark effective theory (HQET) at leading order to strong decays of heavy hadrons is presented. Comparisons between experimental and theoretical predictions of ratios of decay rates for B mesons, D mesons and kaons are given. The application of HQET to strange mesons presents some encouraging results. The spin-flavor symmetry is used to predict some decay rates that have not yet been measured.Comment: 10 page