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A Measurement of the Semileptonic Branching Fraction of the B_s Meson

Description: We report a measurement of the inclusive semileptonic branching fraction of the B{sub s} meson using data collected with the BABAR detector in the center-of-mass energy region above the {gamma}(4S) resonance. We use the inclusive yield of {phi} mesons and the {phi} yield in association with a high-momentum lepton to perform a simultaneous measurement of the semileptonic branching fraction and the production rate of B{sub s} mesons relative to all B mesons as a function of center-of-mass energy. The inclusive semileptonic branching fraction of the B{sub s} meson is determined to be {Beta}(B{sub s} {yields} {ell}{nu}X) = 9.5{sub -2.0}{sup +2.5}(stat){sub -1.9}{sup +1.1}(syst)%, where {ell} indicates the average of e and {mu}.
Date: June 12, 2012
Creator: Lees, J.P.; Poireau, V.; Tisserand, V.; Garra Tico, J.; Grauges, E.; Martinelli, M. et al.
Partner: UNT Libraries Government Documents Department

Measurement of the Time-Dependent CP Asymmetry of Partially Reconstructed B0 to D*+D*- Decays

Description: We present a new measurement of the time-dependent CP asymmetry of B{sup 0} {yields}D*{sup +}D*{sup -} decays using (471 {+-} 5) million B{bar B} pairs collected with the BABAR detector at the PEP-II B Factory at the SLAC National Accelerator Laboratory. Using the technique of partial reconstruction, we measure the time-dependent CP asymmetry parameters S = -0.34 {+-} 0.12 {+-} 0.05 and C = +0:15 {+-} 0.09 {+-} 0.04. Using the value for the CP-odd fraction R{perpendicular} = 0.158 {+-} 0.028 {+-} 0.006, previously measured by BABAR with fully reconstructed B{sup 0} {yields} D{sup *+}D{sup *-} events, we extract the CP-even components S{sub +} = -0.49 {+-} 0.18 {+-} 0.07 {+-} 0.04 and C{sub +} = +0.15 {+-} 0.09 {+-} 0.04. In each case, the first uncertainty is statistical and the second is systematic; the third uncertainty on S{sub +} is the contribution from the uncertainty on R{perpendicular}. The measured value of the CP-even component S{sub +} is consistent with the value of sin 2{beta} measured in b {yields} (c{bar c})s transitions, and with the Standard Model expectation of small penguin contributions.
Date: August 13, 2012
Creator: Lees, J. P.
Partner: UNT Libraries Government Documents Department

Quarkonium Physics at a Fixed-Target Experiment Using the LHC Beams

Description: We outline the many quarkonium-physics opportunities offered by a multi-purpose fixed-target experiment using the p and Pb LHC beams extracted by a bent crystal. This provides an integrated luminosity of 0.5 fb{sup -1} per year on a typical 1cm-long target. Such an extraction mode does not alter the performance of the collider experiments at the LHC. With such a high luminosity, one can analyse quarkonium production in great details in pp, pd and pA collisions at {radical}s{sub NN} {approx_equal} 115 GeV and at {radical}s{sub NN} {approx_equal} 72 GeV in PbA collisions. In a typical pp (pA) run, the obtained quarkonium yields per unit of rapidity are 2-3 orders of magnitude larger than those expected at RHIC and about respectively 10 (70) times larger than for ALICE. In PbA, they are comparable. By instrumenting the target-rapidity region, the large negative-x{sub F} domain can be accessed for the first time, greatly extending previous measurements by Hera-B and E866. Such analyses should help resolving the quarkonium-production controversies and clear the way for gluon PDF extraction via quarkonium studies. The nuclear target-species versatility provides a unique opportunity to study nuclear matter and the features of the hot and dense matter formed in PbA collisions. A polarised proton target allows the study of transverse-spin asymmetries in J/{Psi} and {Upsilon} production, providing access to the gluon and charm Sivers functions.
Date: April 9, 2012
Creator: Lansberg, J.P.; /Orsay, IPN; Brodsky, S.J.; /SLAC; Fleuret, F.; Polytechnique, /Ecole et al.
Partner: UNT Libraries Government Documents Department

Resonant Enhancement of Charge Density Wave Diffraction in the Rare-Earth Tri-Tellurides

Description: We performed resonant soft X-ray diffraction on known charge density wave (CDW) compounds, rare earth tri-tellurides. Near the M{sub 5} (3d - 4f) absorption edge of rare earth ions, an intense diffraction peak is detected at a wavevector identical to that of CDW state hosted on Te{sub 2} planes, indicating a CDW-induced modulation on the rare earth ions. Surprisingly, the temperature dependence of the diffraction peak intensity demonstrates an exponential increase at low temperatures, vastly different than that of the CDW order parameter. Assuming 4f multiplet splitting due to the CDW states, we present a model to calculate X-ray absorption spectrum and resonant profile of the diffraction peak, agreeing well with experimental observations. Our results demonstrate a situation where the temperature dependence of resonant X-ray diffraction peak intensity is not directly related to the intrinsic behavior of the order parameter associated with the electronic order, but is dominated by the thermal occupancy of the valence states.
Date: May 15, 2012
Creator: Lee, W.S.; Sorini, A.P.; Yi, M.; Chuang, Y.D.; Moritz, B.; Yang, W.L. et al.
Partner: UNT Libraries Government Documents Department

RF Gun Photocathode Research at SLAC

Description: LCLS is presently operating with a third copper photocathode in the original rf gun, with a quantum efficiency (QE) of {approx}1 x 10{sup -4} and projected emittance {gamma}{var_epsilon}{sub x,y} = 0.45 {micro}m at 250 pC bunch charge. The spare LCLS gun is installed in the SLAC Accelerator Structure Test Area (ASTA), fully processed to high rf power. As part of a wider photocathode R and D program, a UV laser system and additional gun diagnostics are being installed at ASTA to measure QE, QE lifetime, and electron beam emittance under a variety of operating conditions. The near-term goals are to test and verify the spare photocathode production/installation sequence, including transfer from the final holding chamber to the rf gun. Mid- and longer-term goals include development of a rigorous understanding of plasma and laser-assisted surface conditioning and investigation of new, high-QE photocathode materials. In parallel, an x-ray photoemission spectroscopy station is nearing completion, to analyze Cu photocathode surface chemistry. In this paper we review the status and anticipated operating parameters of ASTA and the spectroscopy test chamber.
Date: May 16, 2012
Creator: Jongewaard, E.; Akre, R.; Brachmann, A.; Corbett, J.; Gilevich, S.; Grouev, K. et al.
Partner: UNT Libraries Government Documents Department