The Kaon B-parameter from Quenched Domain-Wall QCD

We present numerical results for the kaon B-parameter, B_K, determined in the quenched approximation of lattice QCD. Our simulations are performed using domain-wall fermions and the renormalization group improved, DBW2 gauge action which combine to give quarks with good chiral symmetry at finite lattice spacing. Operators are renormalized non-perturbatively using the RI/MOM scheme. We study scaling by performing the simulation on two different lattices with a^{-1} = 1.982(30) and 2.914(54) GeV. We combine this quenched scaling study with an earlier calculation of B_K using two flavors of dynamical, domain-wall quarks at a single lattice spacing to obtain B_K(MS,NDR,mu=2GeV)=0.563(21)(39)(30), were the first error is statistical, the second systematic (without quenching errors) and the third estimates the error due to quenching.Comment: 77 pages, 44 figures, to be published in Phys. Rev.

Hysteresis of spectral evolution in the soft state of black-hole binary LMC X-3

We report the discovery of hysteresis between the x-ray spectrum and luminosity of black-hole binary LMC X-3. Our observations, with the Proportional Counter Array on the Rossi X-ray Timing Explorer, took place entirely within the soft spectral state, dominated by a spectral component that was fitted well with a multicolor disk blackbody. A power-law component was seen only during times when the luminosity of the disk blackbody was declining. The x-ray luminosity at these times was comparable to that seen in transient systems (x-ray novae) when they return to the hard state at the end of an outburst. Our observations may represent partial transitions to the hard state; complete transitions have been seen in this system by Wilms et al. (2001). If they are related to the soft-to-hard transition in transients, then they demonstrate that hysteresis effects can appear without a full state transition. We discuss these observations in the context of earlier observations of hysteresis within the hard state of binaries 1E 1740.7-2942 and GRS 1758-258 and in relation to published explanations of hysteresis in transients.Comment: 14 pages, 6 figures, accepted by The Astrophysical Journa

Using tasks to explore teacher knowledge in situation-specific contexts

This article was published in the journal, Journal of Mathematics Teacher Education [© Springer] and the original publication is available at www.springerlink.comResearch often reports an overt discrepancy between theoretically/out-of context expressed teacher beliefs about mathematics and pedagogy and actual practice. In order to explore teacher knowledge in situation-specific contexts we have engaged mathematics teachers with classroom scenarios (Tasks) which: are hypothetical but grounded on learning and teaching issues that previous research and experience have highlighted as seminal; are likely to occur in actual practice; have purpose and utility; and, can be used both in (pre- and in-service) teacher education and research through generating access to teachers’ views and intended practices. The Tasks have the following structure: reflecting upon the learning objectives within a mathematical problem (and solving it); examining a flawed (fictional) student solution; and, describing, in writing, feedback to the student. Here we draw on the written responses to one Task (which involved reflecting on solutions of x+x−1=0 of 53 Greek in-service mathematics teachers in order to demonstrate the range of teacher knowledge (mathematical, didactical and pedagogical) that engagement with these tasks allows us to explore

Survival probability in diffractive Higgs production in high density QCD

In this paper, the contribution of hard processes described by the BFKL pomeron exchange, is taken into account by calculating the first enhanced diagram. The survival probability is estimated, using the ratio of the first enhanced diagram and the single pomeron amplitude, taking into account all essential pomeron loop diagrams in the toy model of Mueller. The triple pomeron vertex is calculated explicitly in the momentum representation. This calculation is used for estimating the survival probability, It turns out that the survival probability is small, at $0.4$. Hard pomeron re-scattering processes contribute substantially to the survival probability.Comment: 28 pages, 7 figure

Angular Dependence of the High-Magnetic-Field Phase Diagram of URu2Si2

We present measurements of the magnetoresistivity RHOxx of URu2Si2 single crystals in high magnetic fields up to 60 T and at temperatures from 1.4 K to 40 K. Different orientations of the magnetic field have been investigated permitting to follow the dependence on Q of all magnetic phase transitions and crossovers, where Q is the angle between the magnetic field and the easy-axis c. We find out that all magnetic transitions and crossovers follow a simple 1/cos(Q) -law, indicating that they are controlled by the projection of the field on the c-axis

Detecting Higgs Boson Decay to Neutralinos at Hadron Supercolliders

We examine prospects for detecting the neutral Higgs bosons of minimal supersymmetric models (MSSM) when their decays into neutralino pairs are kinematically allowed. The best signature appears to be H_h,H_p\to\tz_2\tz_2\to 4\ell +\eslt. We argue that Standard Model contributions to this signature are negligible, and examine regions of MSSM parameter space where the four lepton mode should be observable at the Large Hadron Collider. The same signal can also come from continuum neutralino pair production. We propose a set of cuts to illustrate that the neutralino decay mode of the Higgs bosons provides a viable signal over a substantial range of model parameters, and show that it may be separable from continuum neutralino production if sufficient integrated luminosity can be accumulated.Comment: 15 pages (REVTEX), 7 figures available by regular mail, FSU-HEP-940204, UH-511-781-9

Associated Higgs Production in the MSSM

We investigate the inclusive production of the Higgs bosons of the minimal supersymmetric model with a heavy quark pair, ($t {\bar t}$ and $b {\bar b}$), in e^+e^- collisions at high energies, $\sqrt{s}=500 GeV$ and $\sqrt{s}=1 TeV$. The ${\cal O}(\alpha_s)$ QCD radiative corrections are included and the dependence of the production rates on the parameters of the MSSM is explored. The associated production of a Higgs boson with a $b {\bar b}$ pair receives large resonant contributions and can have a significant rate

Before sailing on a domain-wall sea

We discuss the very different roles of the valence-quark and the sea-quark residual masses ($m_{res}^v$ and $m_{res}^s$) in dynamical domain-wall fermions simulations. Focusing on matrix elements of the effective weak hamiltonian containing a power divergence, we find that $m_{res}^v$ can be a source of a much bigger systematic error. To keep all systematic errors due to residual masses at the 1% level, we estimate that one needs $a m_{res}^s \le 10^{-3}$ and $a m_{res}^v \le 10^{-5}$, at a lattice spacing $a\sim 0.1$ fm. The practical implications are that (1) optimal use of computer resources calls for a mixed scheme with different domain-wall fermion actions for the valence and sea quarks; (2) better domain-wall fermion actions are needed for both the sea and the valence sectors.Comment: latex, 25 pages. Improved discussion in appendix, including correction of some technical mistakes; ref. adde