Occam’s Reader: The First Library-Developed Ebook Interlibrary Loan System

An ebook interlibrary loan system called “Occam’s Reader” was developed through collaboration among libraries of the Greater Western Library Alliance. The first of its kind, Occam’s Reader has proved to be a great success due in no small measure to thorough planning, testing, implementation and development through 2012 to 2104. A new version of the system, Occam’s Reader 2.0 is planned for later in 2015. As libraries band together to accomplish a collaborative goal, there really is nothing that can hold them bac

Book Raider: Connecting Patrons of Texas Tech University Libraries with Resources Anytime, Anywhere

Given the mandate of Texas Tech University to expand its research mission, Texas Tech University Libraries developed new library services through the Book Raider project that allows patrons to use mobile apps to check library holdings and to order materials through interlibrary loan. Library literature shows an increasing desire among patrons to use this type of technology and suggests an open door exists for librarians to create these new modes of access and delivery. Book Raider, a collaborative project of several departments of Texas Tech University Libraries, involved the development of various types of apps across several technology platforms, a project that grows in popularity among students and faculty of the University

Evidence for a Nonplanar Amplituhedron

The scattering amplitudes of planar N = 4 super-Yang-Mills exhibit a number of remarkable analytic structures, including dual conformal symmetry and logarithmic singularities of integrands. The amplituhedron is a geometric construction of the integrand that incorporates these structures. This geometric construction further implies the amplitude is fully specified by constraining it to vanish on spurious residues. By writing the amplitude in a dlog basis, we provide nontrivial evidence that these analytic properties and “zero conditions” carry over into the nonplanar sector. This suggests that the concept of the amplituhedron can be extended to the nonplanar sector of N = 4 super-Yang-Mills theory

Logarithmic Singularities and Maximally Supersymmetric Amplitudes

The dual formulation of planar =4 super-Yang-Mills scattering amplitudes makes manifest that the integrand has only logarithmic singularities and no poles at infinity. Recently, Arkani-Hamed, Bourjaily, Cachazo and Trnka conjectured the same singularity properties hold to all loop orders in the nonplanar sector as well. Here we conjecture that to all loop orders these constraints give us the key integrand level analytic information contained in dual conformal symmetry. We also conjecture that to all loop orders, while N=8 supergravity has poles at infinity, at least at four points it has only logarithmic singularities at finite locations. We provide nontrivial evidence for these conjectures. For the three-loop four-point N=4 super-Yang-Mills amplitude, we explicitly construct a complete basis of diagram integrands that has only logarithmic singularities and no poles at infinity. We then express the complete amplitude in terms of the basis diagrams, with the coefficients determined by unitarity. We also give examples at three loops showing how to make the logarithmic singularity properties manifest via d log forms. We give additional evidence at four and five loops supporting the nonplanar logarithmic singularity conjecture. Furthermore, we present a variety of examples illustrating that these constraints are more restrictive than dual conformal symmetry. Our investigations show that the singularity structures of planar and nonplanar integrands in N=4 super-Yang-Mills are strikingly similar. While it is not clear how to extend either dual conformal symmetry or a dual formulation to the nonplanar sector, these results suggest that related concepts might exist and await discovery. Finally, we describe the singularity structure of N=8 supergravity at three loops and beyond

Bounds on fourth generation induced Lepton Flavour Violating double insertions in Supersymmetry

We derive bounds on leptonic double mass insertions of the type $\delta^{l}_{i4} \delta^{l}_{4j}$ in four generational MSSM, using the present limits on $l_i \to l_j + \gamma$. Two main features distinguish the rates of these processes in MSSM4 from MSSM3 : (a) tan$\beta$ is restricted to be very small $\lesssim 3$ and (b) the large masses for the fourth generation leptons. In spite of small $\tan\beta$, there is an enhancement in amplitudes with $llrr$($\delta_{i4}^{ll}\delta_{4j}^{rr}$) type insertions which pick up the mass of the fourth generation lepton, $m_{\tau'}$. We find these bounds to be at least two orders of magnitude more stringent than those in MSSM3.Comment: Latex, 15 pages and 7 figures, Published versio

CHY representations for gauge theory and gravity amplitudes with up to three massive particles

We show that a wide class of tree-level scattering amplitudes involving scalars, gauge bosons, and gravitons, up to three of which may be massive, can be expressed in terms of a Cachazo-He-Yuan representation as a sum over solutions of the scattering equations. These amplitudes, when expressed in terms of the appropriate kinematic invariants, are independent of the masses and therefore identical to the corresponding massless amplitudes.Comment: 20 pages, 1 figure; v2: minor typos corrected, published versio

Four Generations: SUSY and SUSY Breaking

We revisit four generations within the context of supersymmetry. We compute the perturbativity limits for the fourth generation Yukawa couplings and show that if the masses of the fourth generation lie within reasonable limits of their present experimental lower bounds, it is possible to have perturbativity only up to scales around 1000 TeV. Such low scales are ideally suited to incorporate gauge mediated supersymmetry breaking, where the mediation scale can be as low as 10-20 TeV. The minimal messenger model, however, is highly constrained. While lack of electroweak symmetry breaking rules out a large part of the parameter space, a small region exists, where the fourth generation stau is tachyonic. General gauge mediation with its broader set of boundary conditions is better suited to accommodate the fourth generation.Comment: 27 pages, 5 figure

Theory and phenomenology of two-Higgs-doublet models

We discuss theoretical and phenomenological aspects of two-Higgs-doublet extensions of the Standard Model. In general, these extensions have scalar mediated flavour changing neutral currents which are strongly constrained by experiment. Various strategies are discussed to control these flavour changing scalar currents and their phenomenological consequences are analysed. In particular, scenarios with natural flavour conservation are investigated, including the so-called type I and type II models as well as lepton-specific and inert models. Type III models are then discussed, where scalar flavour changing neutral currents are present at tree level, but are suppressed by either specific ansatze for the Yukawa couplings or by the introduction of family symmetries. We also consider the phenomenology of charged scalars in these models. Next we turn to the role of symmetries in the scalar sector. We discuss the six symmetry-constrained scalar potentials and their extension into the fermion sector. The vacuum structure of the scalar potential is analysed, including a study of the vacuum stability conditions on the potential and its renormalization-group improvement. The stability of the tree level minimum of the scalar potential in connection with electric charge conservation and its behaviour under CP is analysed. The question of CP violation is addressed in detail, including the cases of explicit CP violation and spontaneous CP violation. We present a detailed study of weak basis invariants which are odd under CP. A careful study of spontaneous CP violation is presented, including an analysis of the conditions which have to be satisfied in order for a vacuum to violate CP. We present minimal models of CP violation where the vacuum phase is sufficient to generate a complex CKM matrix, which is at present a requirement for any realistic model of spontaneous CP violation.Comment: v3: 180 pages, 506 references, new chapter 7 with recent LHC results; referee comments taken into account; submitted to Physics Report

Physics searches at the LHC

With the LHC up and running, the focus of experimental and theoretical high energy physics will soon turn to an interpretation of LHC data in terms of the physics of electroweak symmetry breaking and the TeV scale. We present here a broad review of models for new TeV-scale physics and their LHC signatures. In addition, we discuss possible new physics signatures and describe how they can be linked to specific models of physics beyond the Standard Model. Finally, we illustrate how the LHC era could culminate in a detailed understanding of the underlying principles of TeV-scale physics.Comment: 184 pages, 55 figures, 14 tables, hundreds of references; scientific feedback is welcome and encouraged. v2: text, references and Overview Table added; feedback still welcom