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Time-resolved pump-probe experiments at the LCLS (open access)

Time-resolved pump-probe experiments at the LCLS

The first time-resolved x-ray/optical pump-probe experiments at the SLAC Linac Coherent Light Source (LCLS) used a combination of feedback methods and post-analysis binning techniques to synchronize an ultrafast optical laser to the linac-based x-ray laser. Transient molecular nitrogen alignment revival features were resolved in time-dependent x-ray-induced fragmentation spectra. These alignment features were used to find the temporal overlap of the pump and probe pulses. The strong-field dissociation of x-ray generated quasi-bound molecular dications was used to establish the residual timing jitter. This analysis shows that the relative arrival time of the Ti:Sapphire laser and the x-ray pulses had a distribution with a standard deviation of approximately 120 fs. The largest contribution to the jitter noise spectrum was the locking of the laser oscillator to the reference RF of the accelerator, which suggests that simple technical improvements could reduce the jitter to better than 50 fs.
Date: August 12, 2011
Creator: Glownia, James; Cryan, J.; Andreasson, J.; Belkacem, A.; Berrah, N.; Blaga, C. L. et al.
Object Type: Article
System: The UNT Digital Library
Transverse Beam Polarizationas an Alternate View into New Physics at CLIC (open access)

Transverse Beam Polarizationas an Alternate View into New Physics at CLIC

In e{sup +}e{sup -} collisions, transverse beam polarization can be a useful tool in studying the properties of particles associated with new physics beyond the Standard Model(SM). However, unlike in the case of measurements associated with longitudinal polarization, the formation of azimuthal asymmetries used to probe this physics in the case of transverse polarization requires both e{sup {+-}} beams to be simultaneously polarized. In this paper we discuss the further use of transverse polarization as a probe of new physics models at a high energy, {radical}s = 3 TeV version of CLIC. In particular, we show (i) how measurements of the sign of these asymmetries is sufficient to discriminate the production of spin-0 supersymmetric states from the spin-1/2 Kaluza-Klein excitations of Universal Extra Dimensions. Simultaneously, the contribution to this asymmetry arising from the potentially large SM W{sup +}W{sup -} background can be made negligibly small. We then show (ii) how measurements of such asymmetries and their associated angular distributions on the peak of a new resonant Z{prime}-like state can be used to extract precision information on the Z{prime} couplings to the SM fermions.
Date: August 12, 2011
Creator: Rizzo, Thomas G.
Object Type: Article
System: The UNT Digital Library
Two-Dimensional Dirac Fermions in a Topological Insulator: Transport in the Quantum Limit (open access)

Two-Dimensional Dirac Fermions in a Topological Insulator: Transport in the Quantum Limit

Pulsed magnetic fields of up to 55T are used to investigate the transport properties of the topological insulator Bi{sub 2}Se{sub 3} in the extreme quantum limit. For samples with a bulk carrier density of n = 2.9 x 10{sup 16} cm{sup -3}, the lowest Landau level of the bulk 3D Fermi surface is reached by a field of 4T. For fields well beyond this limit, Shubnikov-de Haas oscillations arising from quantization of the 2D surface state are observed, with the {nu} = 1 Landau level attained by a field of {approx} 35T. These measurements reveal the presence of additional oscillations which occur at fields corresponding to simple rational fractions of the integer Landau indices.
Date: August 12, 2011
Creator: Analytis, J. G.; McDonald, R. D.; Riggs, S. C.; Chu, J.-H.; Boebinger, G. S. & Fisher, I. R.
Object Type: Article
System: The UNT Digital Library
Unusual Layer-Dependent Charge Distribution, Collective Mode Coupling, and Superconductivity in Multilayer Cuprate Ba2Ca3Cu4O8F2 (open access)

Unusual Layer-Dependent Charge Distribution, Collective Mode Coupling, and Superconductivity in Multilayer Cuprate Ba2Ca3Cu4O8F2

Low energy ultrahigh momentum resolution angle resolved photoemission spectroscopy study on four-layer self-doped high T{sub c} superconductor Ba{sub 2}Ca{sub 3}Cu{sub 4}O{sub 8}F{sub 2} (F0234) revealed fine structure in the band dispersion, identifying the unconventional association of hole and electron doping with the inner and outer CuO{sub 2} layers, respectively. For the states originating from two inequivalent CuO{sub 2} layers, different energy scales are observed in dispersion kinks associated with the collective mode coupling, with the larger energy scale found in the electron (n-) doped state which also has stronger coupling strength. Given the earlier finding that the superconducting gap is substantially larger along the n-type Fermi surface, our observations connect the mode coupling energy and strength with magnitude of the pairing gap.
Date: August 12, 2011
Creator: Chen, Yulin; /SLAC /Stanford U., Phys. Dept. /LBL, Berkeley; Iyo, Akira; /JRCAT, Tsukuba /Tsukuba Coll. Tech.; Yang, Wanli; /LBL, Berkeley et al.
Object Type: Article
System: The UNT Digital Library

[V. Lane Rawlins speaks at UNT Summer 2011 Commencement]

Photograph of UNT President V. Lane Rawlins speaking at the Sumer 2011 Commencement held in the Coliseum (Super Pit). Rawlins is standing behind a podium, facing to the left of the camera. He is wearing doctoral regalia.
Date: August 12, 2011
Creator: Chaney, Ken
Object Type: Photograph
System: The UNT Digital Library
Waste Acceptance Testing of Secondary Waste Forms: Cast Stone, Ceramicrete and DuraLith (open access)

Waste Acceptance Testing of Secondary Waste Forms: Cast Stone, Ceramicrete and DuraLith

To support the selection of a waste form for the liquid secondary wastes from WTP, Washington River Protection Solutions has initiated secondary-waste-form testing work at Pacific Northwest National Laboratory (PNNL). In anticipation of a down-selection process for a waste form for the Solidification Treatment Unit to be added to the ETF, PNNL is conducting tests on four candidate waste forms to evaluate their ability to meet potential waste acceptance criteria for immobilized secondary wastes that would be placed in the IDF. All three waste forms demonstrated compressive strengths above the minimum 3.45 MPa (500 psi) set as a target for cement-based waste forms. Further, none of the waste forms showed any significant degradation in compressive strength after undergoing thermal cycling (30 cycles in a 10 day period) between -40 C and 60 C or water immersion for 90 days. The three leach test methods are intended to measure the diffusion rates of contaminants from the waste forms. Results are reported in terms of diffusion coefficients and a leachability index (LI) calculated based on the diffusion coefficients. A smaller diffusion coefficient and a larger LI are desired. The NRC, in its Waste Form Technical Position (NRC 1991), provides recommendations and guidance …
Date: August 12, 2011
Creator: Mattigod, Shas V.; Westsik, Joseph H.; Chung, Chul-Woo; Lindberg, Michael J. & Parker, Kent E.
Object Type: Report
System: The UNT Digital Library
Women in the United States Congress: 1917-2011 (open access)

Women in the United States Congress: 1917-2011

This report identifies the names, committee assignments, dates of service, and (for Representatives) congressional districts of the 276 women who have served in Congress.
Date: August 12, 2011
Creator: Manning, Jennifer E. & Shogan, Colleen J.
Object Type: Report
System: The UNT Digital Library
The Z Charmoniumlike Mesons (open access)

The Z Charmoniumlike Mesons

A brief review of the experimental situation concerning the electrically charged charmoniumlike meson candidates, Z{sup -}, is presented. The Belle Collaboration reported peaks in the {psi}{prime}{pi}{sup -} and {chi}{sub c1}{pi}{sup -} invariant mass distributions in B {yields} {psi}{prime}{pi}{sup -}K and B {yields} {chi}{sub c1}{pi}{sup -}K, respectively. If these peaks are meson resonances, they would have a minimal quark substructure of c{bar c}d{bar u} and be unmistakeably exotic. However, even though the Belle signals have more than 5{sigma} statistical significance, the experimental situation remains uncertain in that none of these peaks have yet been confirmed by other experiments. An analysis by the BABAR Collaboration of B {yields} {psi}{prime}{pi}{sup -}K neither confirms nor contradicts the Belle claim for the Z(4430){sup -} {yields} {psi}{prime}{pi}{sup -}. In the BABAR analysis, B {yields} J/{psi}{pi}{sup -}K decays were also studied, and no evidence for Z(4430){sup -} {yields} J/{psi}{pi}{sup -} was found. In this paper, we review and compare Belle and BABAR results on searches for charged charmonium-like states.
Date: August 12, 2011
Creator: Gabareen Mokhtar, Arafat & Olsen, Stephen Lars
Object Type: Article
System: The UNT Digital Library