Exclusive J/ψJ/\psi and Υ\Upsilon photoproduction and the low xx gluon

We study exclusive vector meson photoproduction, $\gamma p \to V + p$ with $V=J/\psi$ or $\Upsilon$, at NLO in collinear factorisation, in order to examine what may be learnt about the gluon distribution at very low $x$. We examine the factorisation scale dependence of the predictions. We argue that, using knowledge of the NLO corrections, terms enhanced by a large $\ln(1/\xi)$ can be reabsorbed in the LO part by a choice of the factorisation scale. (In these exclusive processes $\xi$ takes the role of Bjorken-$x$.) Then, the scale dependence coming from the remaining NLO contributions has no $\ln(1/\xi)$ enhancements. As a result, we find that predictions for the amplitude of $\Upsilon$ production are stable to within about $\pm 15\%$. This will allow data for the exclusive process $p p \to p\Upsilon p$ at the LHC, particularly from LHCb, to be included in global parton analyses to constrain the gluon PDF down to $x\sim 10^{-5}$. Moreover, the study of exclusive $J/\psi$ photoproduction indicates that the gluon density found in the recent global PDF analyses is too small at low $x$ and low scales.Comment: 21 pages, 6 figures. Text significantly improved, references added, version to be published in J.Phys.

Short-term Response of Holcus lanatus L. (Common Velvetgrass) to Chemical and Manual Control at Yosemite National Park, USA

One of the highest priority invasive species at both Yosemite and Sequoia and Kings Canyon national parks is Holcus lanatus L. (common velvetgrass), a perennial bunchgrass that invades mid-elevation montane meadows. Despite velvetgrass being a high priority species, there is little information available on control techniques. The goal of this project was to evaluate the short-term response of a single application of common chemical and manual velvetgrass control techniques. The study was conducted at three montane sites in Yosemite National Park. Glyphosate spotspray treatments were applied at 0.5, 1.0, 1.5, and 2.0% concentrations, and compared with hand pulling to evaluate effects on cover of common velvetgrass, cover of other plant species, and community species richness. Posttreatment year 1 cover of common velvetgrass was 12.1% 6 1.6 in control plots, 6.3% 6 1.5 averaged over the four chemical treatments (all chemical treatments performed similarly), and 13.6% 6 1.7 for handpulled plots. This represents an approximately 50% reduction in common velvetgrass cover in chemically- treated plots recoded posttreatment year 1 and no statistically significant reduction in hand pulled plots compared with controls. However, there was no treatment effect in posttreatment year 2, and all herbicide application rates performed similarly. In addition, there were no significant treatment effects on nontarget species or species richness. These results suggest that for this level of infestation and habitat type, (1) one year of hand pulling is not an effective control method and (2) glyphosate provides some level of control in the short-term without impact to nontarget plant species, but the effect is temporary as a single year of glyphosate treatment is ineffective over a twoyear period

Patient perceptions regarding benefits of single visit scale and polish : a randomised controlled trial

Peer reviewedPublisher PD

Measurement of the azimuthal angle dependence of inclusive jet yields in Pb+Pb collisions at √sNN=2.76 TeV with the ATLAS detector

Measurements of the variation of inclusive jet suppression as a function of relative azimuthal angle, Δϕ, with respect to the elliptic event plane provide insight into the path-length dependence of jet quenching. ATLAS has measured the Δϕ dependence of jet yields in 0.14  nb-1 of √sNN=2.76  TeV Pb+Pb collisions at the LHC for jet transverse momenta pT>45  GeV in different collision centrality bins using an underlying event subtraction procedure that accounts for elliptic flow. The variation of the jet yield with Δϕ was characterized by the parameter, v2jet, and the ratio of out-of-plane (Δϕ∼π/2) to in-plane (Δϕ∼0) yields. Nonzero v2jet values were measured in all centrality bins for pT<160  GeV. The jet yields are observed to vary by as much as 20% between in-plane and out-of-plane directions

Measurement of the production cross section of prompt J/ψ mesons in association with a W± boson in pp collisions at p s = 7 TeV with the ATLAS detector

The process pp → W±J/ψ provides a powerful probe of the production mechanism of charmonium in hadronic collisions, and is also sensitive to multiple parton interactions in the colliding protons. Using the 2011 ATLAS dataset of 4.5 fb-1 of p s = 7TeV pp collisions at the LHC, the first observation is made of the production of W± + prompt J/ events in hadronic collisions, using W± → μ and J/ψ → μ+μ-. A yield of 27.4±7.5 -6.5 W± + prompt J/ψ events is observed, with a statistical significance of 5.1. The production rate as a ratio to the inclusive W± boson production rate is measured, and the double parton scattering contribution to the cross section is estimated

Representation-theoretic derivation of the Temperley-Lieb-Martin algebras

Explicit expressions for the Temperley-Lieb-Martin algebras, i.e., the quotients of the Hecke algebra that admit only representations corresponding to Young diagrams with a given maximum number of columns (or rows), are obtained, making explicit use of the Hecke algebra representation theory. Similar techniques are used to construct the algebras whose representations do not contain rectangular subdiagrams of a given size.Comment: 12 pages, LaTeX, to appear in J. Phys.

Turning the Quantum Group Invariant XXZ Spin-Chain Hermitian: A Conjecture on the Invariant Product

This is a continuation of a previous joint work with Robert Weston on the quantum group invariant XXZ spin-chain (math-ph/0703085). The previous results on quasi-Hermiticity of this integrable model are briefly reviewed and then connected with a new construction of an inner product with respect to which the Hamiltonian and the representation of the Temperley-Lieb algebra become Hermitian. The approach is purely algebraic, one starts with the definition of a positive functional over the Temperley-Lieb algebra whose values can be computed graphically. Employing the Gel'fand-Naimark-Segal (GNS) construction for C*-algebras a self-adjoint representation of the Temperley-Lieb algebra is constructed when the deformation parameter q lies in a special section of the unit circle. The main conjecture of the paper is the unitary equivalence of this GNS representation with the representation obtained in the previous paper employing the ideas of PT-symmetry and quasi-Hermiticity. An explicit example is presented.Comment: 12 page

The Effective Potential, the Renormalisation Group and Vacuum Stability

We review the calculation of the the effective potential with particular emphasis on cases when the tree potential or the renormalisation-group-improved, radiatively corrected potential exhibits non-convex behaviour. We illustrate this in a simple Yukawa model which exhibits a novel kind of dimensional transmutation. We also review briefly earlier work on the Standard Model. We conclude that, despite some recent claims to the contrary, it can be possible to infer reliably that the tree vacuum does not represent the true ground state of the theory.Comment: 23 pages; 5 figures; v2 includes minor changes in text and additional reference