Towards an Understanding of the New Charm and Charm-Strange Mesons

The observation of the D_{sJ}^*(2317), D_{sJ}(2460), and SELEX D^*_{sJ}(2632) states with properties differing considerably from what was expected has led to a renewed interest in hadron spectroscopy. In addition to these states, non-strange partners of the D_{sJ} states have also been observed. Understanding the D_0^* and D_1' states can provide important insights into the D_{sJ} states. In this contribution I examine quark model predictions for the D_0^* and D_1' states and discuss experimental measurements that can shed light on them. I find that these states are well described as the broad, j=1/2 non-strange charmed P-wave mesons. In the latter part of this writeup I discuss the c bar{s} possibilities for the SELEX D^*_{sJ}(2632) and measurements that can shed light on it.Comment: Talk presented at the 1st Meeting of the APS Topical Group on Hadronic Physics (Fermilab, Oct 24-26, 2004). 4 pages uses jpcon

Leptoquark Production and Identification at High Energy Lepton Colliders

Leptoquarks can be produced in substantial numbers for masses very close to the collider centre of mass energy in $e^+e^-$, $e\gamma$, and $\mu^+\mu^-$ collisions due to the quark content of the photon resulting in equivalently high discovery limits. Using polarization asymmetries in an $e\gamma$ collider the ten different types of leptoquarks listed by Buchm\"uller, R\"uckl and Wyler can be distinquished from one another for leptoquark masses essentially up to the kinematic limit. Thus, if a leptoquark were discovered, an $e\gamma$ collider could play a crucial role in determining its origins.Comment: LaTex file uses aipproc.sty, epsfig, and rotating. 9 pages with 8 postscript figures. Talk given at 20th Annual MRST (Montreal-Rochester-Syracuse-Toronto) Meeting on High-Energy Physics: MRST 98: Toward the Theory of Everything, Montreal, Canada, 13-15 May 199

Absence of hyperuniformity in amorphous hard-sphere packings of nonvanishing complexity

We relate the structure factor $S(\mathbf{k} \to \mathbf{0})$ in a system of jammed hard spheres of number density $\rho$ to its complexity per particle $\Sigma(\rho)$ by the formula $S(\mathbf{k} \to \mathbf{0})=-1/ [\rho^2\Sigma''(\rho)+2\rho\Sigma'(\rho)]$. We have verified this formula for the case of jammed disks in a narrow channel, for which it is possible to find $\Sigma(\rho)$ and $S(\mathbf{k})$ analytically. Hyperuniformity, which is the vanishing of $S(\mathbf{k} \to \mathbf{0})$, will therefore not occur if the complexity is nonzero. An example is given of a jammed state of hard disks in a narrow channel which is hyperuniform when generated by dynamical rules that produce a non-extensive complexity.Comment: 5 pages, 3 figure

Understanding the ideal glass transition: Lessons from an equilibrium study of hard disks in a channel

We use an exact transfer-matrix approach to compute the equilibrium properties of a system of hard disks of diameter $\sigma$ confined to a two-dimensional channel of width $1.95\,\sigma$ at constant longitudinal applied force. At this channel width, which is sufficient for next-nearest-neighbor disks to interact, the system is known to have a great many jammed states. Our calculations show that the longitudinal force (pressure) extrapolates to infinity at a well-defined packing fraction $\phi_K$ that is less than the maximum possible $\phi_{\rm max}$, the latter corresponding to a buckled crystal. In this quasi-one-dimensional problem there is no question of there being any \emph{real} divergence of the pressure at $\phi_K$. We give arguments that this avoided phase transition is a structural feature -- the remnant in our narrow channel system of the hexatic to crystal transition -- but that it has the phenomenology of the (avoided) ideal glass transition. We identify a length scale $\tilde{\xi}_3$ as our equivalent of the penetration length for amorphous order: In the channel system, it reaches a maximum value of around $15\,\sigma$ at $\phi_K$, which is larger than the penetration lengths that have been reported for three dimensional systems. It is argued that the $\alpha$-relaxation time would appear on extrapolation to diverge in a Vogel-Fulcher manner as the packing fraction approaches $\phi_K$.Comment: 17 pages, 16 figure