On the design of experiments to study extreme field limits
We propose experiments on the collision of high intensity electromagnetic pulses with electron bunches and on the collision of multiple electromagnetic pulses for studying extreme field limits in the nonlinear interaction of electromagnetic waves. The effects of nonlinear QED will be revealed in these laser plasma experiments.

title: Mono-Energetic Beams from Laser Plasma Interactions
abstract: A laser driven wakefield accelerator has been tuned to produce high energy electron bunches with low emittance and energy spread by extending the interaction length using a plasma channel. Wakefield accelerators support gradients thousands of times those achievable in RF accelerators, but short acceleration distance, limited by diffraction, has resulted in low energy beams with 100% electron energy spread. In the present experiments on the L’OASIS laser, the relativistically intense drive pulse was guided over 10 diffraction ranges by a plasma channel. At a drive pulse power of 9 TW, electrons were trapped from the plasma and beams of percent energy spread containing > 200 pC charge above 80 MeV and with normalized emittance estimated at < 2 π-mm-mrad were produced. Data and simulations (VORPAL code) show the high quality bunch was formed when beam loading turned off injection after initial trapping, and when the particles were extracted as they dephased from the wake. Up to 4 TW was guided without trapping, potentially providing a platform for controlled injection. The plasma channel technique forms the basis of a new class of accelerators, with high gradients and high beam quality.

title: High Quality Electron Bunches up to 1 GeV from Laser Wakefield Acceleration at LBNL
abstract: Experiments at the LOASIS laboratory of LBNL have demonstrated production of 100 MeV to 1 GeV electron bunches with low energy spread and low divergence from laser wakefield acceleration. The radiation pressure of a 10 TW laser pulse, guided over 10 diffraction ranges by a few‐mm long plasma density channel, was used to drive an intense plasma wave (wakefield), producing electron bunches with energies on the order of 100 MeV and acceleration gradients on the order of 100 GV/m. Beam energy was increased from 100 MeV to 1 GeV by using a few‐cm long guiding channel at lower density, driven by a 40 TW laser, demonstrating the anticipated scaling to higher beam energies. Particle simulations indicate that the low energy spread beams were produced from self‐trapped electrons through the interplay of trapping, loading, and dephasing. Other experiments and simulations are also underway to control injection of particles into the wake, and hence improve beam quality and stability further.

title: Design considerations for a laser‐plasma linear collider
abstract: Design considerations for a next‐generation electron‐positron linear collider based on laser‐plasma‐accelerators are discussed. Several of the advantages and challenges of laser‐plasma‐based accelerator technology are addressed. An example of the parameters for a 1 TeV laser‐plasma‐based collider is presented.

title: Generation of single pulse particle beams in a plasma channel by laser injection in laser wakefield accelerators
abstract: A laser injection mechanism that generates a single pulse, high quality beam is described. In the past, different all-optical injection schemes for the generation of ultrashort electron bunches were proposed. A very promising scheme proposed by E. Esarey [E. Esarey, R.F. Hubbard, W.P. Leemans A. Ting and P. Sprangle,"  (1997)] uses the collision of two counterpropagation laser pulses to inject particles. However, the results of ours 2D particle-in-cell (PIC) simulations have shown that in addition to the bunch created by pulse collision, a train of pulses is also generated by a different mechanism. In this paper we show that is possible to achieve a single pulse, high quality beam if the generation of the plasma wakefield takes place in a channel and particles are injected by a phase-kick mechanism [J. Cary at this conference]. We have performed 2D PIC simulations of our proposed injection scheme using the code VORPAL [C. Nieter at this conference]. We have obtained a high quality 11 MeV., 6 fs. single electron bunch with energy spread of 4% and emittance of 0.01/spl pi/ - mm - mrad.

title: Long-range persistence of femtosecond modulations on laser-plasma-accelerated electron beams.
abstract: Laser plasma accelerators have produced femtosecond electron bunches with a relative energy spread ranging from 100% to a few percent. Simulations indicate that the measured energy spread can be dominated by a correlated spread, with the slice spread significantly lower. Measurements of coherent optical transition radiation are presented for broad-energy-spread beams with laser-induced density and momentum modulations. The long-range (meter-scale) observation of coherent optical transition radiation indicates that the slice energy spread is below the percent level to preserve the modulations.

title: Confining force and running coupling with twelve fundamental and two sextet fermions
abstract: We investigate two models of much recent interest in lattice Beyond Standard Model studies: N_f=2 fermions in the 2-index symmetric (sextet) representation, and N_f=12 fermions in the fundamental representation, both with SU(3) gauge symmetry. We present results at fixed lattice spacing for the static fermion potential and force as measured via lattice simulations. We show indications that both models are confining in the chiral limit and that neither theory is conformal. This is consistent with our findings for the mass spectrum, which indicate that chiral symmetry is spontaneously broken in both theories.

title: Lattice simulations with eight flavors of domain wall fermions in SU(3) gauge theory
abstract: We study an SU(3) gauge theory with Nf=8 degenerate flavors of light fermions in the fundamental representation. Using the domain wall fermion formulation, we investigate the light hadron spectrum, chiral condensate and electroweak S parameter. We consider a range of light fermion masses on two lattice volumes at a single gauge coupling chosen so that IR scales approximately match those from our previous studies of the two- and six-flavor systems. Our results for the Nf=8 spectrum suggest spontaneous chiral symmetry breaking, though fits to the fermion mass dependence of spectral quantities do not strongly disfavor the hypothesis of mass-deformed infrared conformality. Compared to Nf=2 we observe a significant enhancement of the chiral condensate relative to the symmetry breaking scale F, similar to the situation for Nf=6. The reduction of the S parameter, related to parity doubling in the vector and axial-vector channels, is also comparable to our six-flavor results.

title: Probing technicolor theories with staggered fermions
abstract: One exciting possibility of new physics beyond the Standard Model is that the fundamental Higgs sector is replaced by a strongly-interacting gauge theory, known as technicolor. A viable theory must break chiral symmetry dynamically, like in QCD, to generate Goldstone bosons which become the longitudinal components of the W ± and Z. By measuring the eigenvalues of the Dirac operator, one can determine if chiral symmetry is in fact spontaneously broken. We simulate SU(3) gauge theory with ns = 2 and 3 staggered flavors in the fundamental representation, corresponding to Nf = 8 and 12 flavors in the continuum limit. Although our first findi ngs show that both theories are consistent with dynamically broken chiral symmetry and QCD-like behavior, flavor breaking effects in the spectrum may require further c larifications before final conclusions can be drawn. We also compare various improved staggered actions, to suppress this potentially large flavor breaking.

title: Lattice calculation of composite dark matter form factors
abstract: Composite dark matter candidates, which can arise from new strongly-coupled sectors, are well-motivated and phenomenologically interesting, particularly in the context of asymmetric generation of the relic density. In this work, we employ lattice calculations to study the electromagnetic form factors of electroweak-neutral dark-matter baryons for a three-color, QCD-like theory with Nf = 2 and 6 degenerate fermions in the fundamental representation. We calculate the (connected) charge radius and anomalous magnetic moment, both of which can play a significant role for direct detection of composite dark matter. We find minimal Nf dependence in these quantities. We generate mass-dependent cross-sections for dark matter-nucleon interactions and use them in conjunction with experimental results from XENON100, excluding dark matter candidates of this type with masses below 10 TeV.

title: Composite bosonic baryon dark matter on the lattice: SU(4) baryon spectrum and the effective Higgs interaction
abstract: We present the spectrum of baryons in a new SU(4) gauge theory with fundamental fermion constituents. The spectrum of these bosonic baryons is of significant interest for composite dark matter theories. Here, we compare the spectrum and properties of SU(3) and SU(4) baryons, and then compute the dark-matter direct detection cross section via Higgs boson exchange for TeV-scale composite dark matter arising from a confining SU(4) gauge sector. Comparison with the latest LUX results leads to tight bounds on the fraction of the constituent-fermion mass that may arise from electroweak symmetry breaking. Lattice calculations of the dark matter mass spectrum and the Higgs-dark matter coupling are performed on quenched $16^{3} \times 32$, $32^{3} \times 64$, $48^{3} \times 96$, and $64^{3} \times128$ lattices with three different lattice spacings, using Wilson fermions with moderate to heavy pseudoscalar meson masses. Our results lay a foundation for future analytic and numerical study of composite baryonic dark matter.