[en] The APS photoinjector drive laser system has been in operation since 1999 and is achieving a performance level exceeding the requirement of stable operation of the LEUTL FEL system. One remarkable number is the UV energy stability of better than 2% rms, sometimes less than 1% rms. This report summarizes the operation experience of the laser system and the improvements made along the way. We also outline the route of upgrade of the system and some frontier laser research and development opportunities in ultrabright electron beam generation

[en] CTCP, an innovative TCP congestion control algorithm developed by Microsoft, is evaluated and compared to HSTCP and StandardTCP. Tests were performed on the production Internet from Stanford Linear Accelerator Center (SLAC) to various geographically located hosts to give a broad overview of the performances. We find that certain issues were apparent during testing (not directly related to the congestion control algorithms) which may skew results. With this in mind, we find that CTCP performed similarly to HSTCP across a multitude of different network environments. However, to improve the fairness and to reduce the impact of CTCP upon existing StandardTCP traffic, two areas of further research were investigated. Algorithmic additions to CTCP for burst control to reduce the aggressiveness of its cwnd increments demonstrated beneficial improvements in both fairness and throughput over the original CTCP algorithm. Similarly, auto-tuning algorithms were investigated to dynamically adapt CTCP flows to their network conditions for optimal performance. Whilst the effects of these auto-tuning algorithms when used in addition to burst control showed little to no benefit to fairness nor throughput for the limited number of network paths tested, one of the auto-tuning algorithms performed such that there was negligible impact upon StandardTCP. With these improvements, CTCP was found to perform better than HSTCP in terms of fairness and similarly in terms of throughput under the production environments tested

[en] The pseudogap region of the phase diagram is an important unsolved puzzle in the field of high-transition-temperature (high-T_c) superconductivity, characterized by anomalous physical properties. There are open questions about the number of distinct phases and the possible presence of a quantum-critical point underneath the superconducting dome. The picture has remained unclear because there has not been conclusive evidence for a new type of order. Neutron scattering measurements for YBa₂Cu₃O_6+δ (YBCO) resulted in contradictory claims of no and weak magnetic order, and the interpretation of muon spin relaxation measurements on YBCO and of circularly polarized photoemission experiments on Bi₂Sr₂CaCu₂O_8+δ has been controversial. Here we use polarized neutron diffraction to demonstrate for the model superconductor HgBa₂CuO_4+δ (Hg1201) that the characteristic temperature T* marks the onset of an unusual magnetic order. Together with recent results for YBCO, this observation constitutes a demonstration of the universal existence of such a state. The findings appear to rule out theories that regard T* as a crossover temperature rather than a phase transition temperature. Instead, they are consistent with a variant of previously proposed charge-current-loop order that involves apical oxygen orbitals, and with the notion that many of the unusual properties arise from the presence of a quantum-critical point.

[en] In order to develop high spatial resolution and readout speed vertex detectors for the future International Linear Collider (ILC), fast CMOS Monolithic Active Pixel Sensors (MAPS) are studied on this work. Two prototypes of MAPS, MIMOSA 8 and MIMOSA 16, based on the same micro-electronic architecture were developed in CMOS processes with different thickness of epitaxial layer. The size of pixel matrix is 32 x 128: 8 columns of the pixel array are readout directly with analog outputs and the other 24 columns are connected to the column level auto-zero discriminators. The Correlated Double Sampling (CDS) structures are successfully implemented inside pixel and discriminator. The photo diode type pixels with different diode sizes are used in these prototypes. With a ⁵⁵Fe X-ray radioactive source, the important parameters, such as Temporal Noise, Fixed Pattern Noise (FPN), Signal-to-Noise Ratio (SNR), Charge-to-Voltage conversion Factor (CVF) and Charge Collection Efficiency (CCE), are studied as function of readout speed and diode size. For MIMOSA 8, the effect of fast neutrons irradiation is also. Two beam tests campaigns were made: at DESY with a 5 GeV electrons beam and at CERN with a 180 GeV pions beam. Detection Efficiency and Spatial Resolution are studied in function of the discriminator threshold. For these two parameters, the influences of diode size and SNR of the central pixel of a cluster are also discussed. In order to improve the spatial resolution of the digital outputs, a very compact (25 μm x 1 mm) and low consumption (300 μW) column level ADC is designed in AMS 0.35 μm OPTO process. Based on successive approximation architecture, the auto-offset cancellation structure is integrated. A new column level auto-zero discriminator using static latch is also designed. (author)

[en] A graphical method to obtain the general multi-pion correlation functions for a partially coherent pion source is proposed. In an application of this technique, the general four-pion correlation function is obtained for the first time. A modified Gaussian model for a partially coherent source is proposed. The three-pion and four-pion correlation function, and the relation between two-pion, three-pion and four-pion coherence factors for the partially coherent Gaussian source are given. The general forms of the coherence factors and the correlation functions of higher order multi-pion interference are revealed. The Gamow correction factor for Coulomb repulsion between three negative pions in the final state is derived. Methods of data analysis for three pions and pure pion triplets are designed. The details of these methods are discussed. In multi-pion events, the effect of higher order multi-pion interference on the coherence factors for two pion and three pion analyses is studied. The principal result is that, in n-pion interferometry, the distortion of the n-pion coherence factor mainly comes from the (n + 1) pion-multiplet interference. The distortion of the coherence factor becomes a serious problem in data analysis only in the situation where the pion source has a small radius and low temperature. Finally, the data analyses for three LBL streamer chamber experiments are performed. The fitted pion source parameters from two pion and three pion analyses are quite consistent with each other

[en] In this paper we introduce a new algorithm, the cascaded parameter scan method, to efficiently carry out the scan over magnet parameters in the safety analysis for storage ring top-off injection. In top-off safety analysis, one must track particles populating phase space through a beamline containing magnets and apertures and clearly demonstrate that for all possible magnet settings and errors, all particles are lost on scrapers within the properly shielded region. In the usual approach, the number of tracking runs increases exponentially with the number of magnet settings. In the cascaded parameter scan method, the number of tracking runs only increases linearly. This reduction of exponential to linear dependence on the number of set-points, greatly reduces the required computation time and allows one to more densely populate phase space and to increase the number of set-points scanned for each magnet. An example of applying this approach to analyze an NSLS-II beamline, the damping wiggler beamline, is also given.

[en] The APS photoinjector drive laser system has been in operation since 1999 and is achieving a performance level exceeding the requirement of stable operation of the LEUTL FEL system. One remarkable number is the UV energy stability of better than 2% rms, sometimes less than 1% rms. This report summarizes the operation experience of the laser system and the improvements made along the way. We also outline the route of upgrade of the system and some frontier laser research and development opportunities in ultrabright electron beam generation

[en] We argue that the collinear factorization of the fragmentation functions in high energy hadron and nuclei collisions breaks down at transverse momenta k_T (le) Q_s/g due to high parton densities in the colliding hadrons and/or nuclei. We calculate, at next-to-leading order in projectile parton density and to all orders in target parton density, the double-inclusive cross-section for production of a pair of gluons in the scalar J^PC = 0⁺⁺ channel. Using the low energy theorems of QCD we find the inclusive cross-section for π-meson production.

[en] Using a simple harmonic oscillator wave function for deuteron it is possible to give an analytic solution in closed form for p-d elastic scattering. It has the advantage of displaying clearly all the contributions separately (D-wave, spin flip etc.). It can also fit experimental data

[en] Under R parity, the lightest supersymmetric particle (LSP) is stable and may serve as a good dark matter candidate. The R parity can be naturally introduced with a gauge origin at the TeV scale. We go over why a TeV scale B-L gauge extension of the minimal supersymmetric standard model is one of the most natural, if not demanded, low energy supersymmetric models. In the presence of a TeV scale Abelian gauge symmetry, the (predominantly) right-handed sneutrino LSP can be a good dark matter candidate. Its identification at the LHC is challenging because it does not carry any standard model charge. We show how we can use the correlation between the LHC experiments (dilepton resonance signals) and the direct dark matter search experiments (such as CDMS and XENON) to identify the right-handed sneutrino LSP dark matter in the B-L extended minimal supersymmetric standard model.