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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Measurement of CP violation in $B_s^0\to J/\psi \phi$ decays using the full CDF data set

We report on the final measurement of the CP-violating $B_s^0$ mixing phase $\beta_s^{J/ψφ}$ in √s = 1.96 TeV proton-antiproton collisions collected with the Collider Detector at the Fermilab Tevatron collider. Using a sample corresponding to 9.6 fb -1 of integrated luminosity, we fit the decay-time evolution of $B_s^0$ → J/ψ (→ μ + μ - ) φ (→ K + K ₋ ) decays in which the b-quark content at production and the CP parity of the final state are identified. The interference of decays with and without mixing renders the $B_s^0$ mixing phase observable. The phase is determined to be -0.06 < $\beta_s^{J/ψφ}$ < 0.30 at 68% confidence level. The decay-width difference between heavy and light $B_s^0$ eigenstates, and the average $B_s^0$ lifetime are also determined to be ΔΓ s = 0.068 ± 0.027 ps -1 and $\tau_s$ = 1.528 ± 0.021 ps, respectively. These results are among the world’s most precise from a single experiment, and compatible with standard model predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Central exclusive π{sup +}π{sup −} production in pp{sup ¯} collisions at √(s)=0.9 and 1.96 TeV at CDF

Exclusive π{sup +}π{sup −} production in proton-antiproton collisions at √(s)=0.9 and 1.96 TeV in the Collider Detector at Fermilab has been measured. Events with exactly two particles with opposite charge, in |η(π)| < 1.3, with no other particles detected in |η(π)| < 5.9, were selected. We require the central π{sup +}π{sup −} state to have rapidity |y(ππ)| < 1. The data are expected to be dominated by double pomeron exchange. Therefore, the quantum numbers of the central state are constrained. The data show resonance structures attributed to the f{sub 0} and f{sub 2} mesons. The results are valuable for light hadron spectroscopy, and for understanding the nature of the pomeron in a region between non-perturbative and perturbative QCD.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

z {approx} 7 GALAXY CANDIDATES FROM NICMOS OBSERVATIONS OVER THE HDF-SOUTH AND THE CDF-SOUTH AND HDF-NORTH GOODS FIELDS

We use {approx}88 arcmin{sup 2} of deep ({approx}>26.5 mag at 5{sigma}) NICMOS data over the two GOODS fields and the HDF-South to conduct a search for bright z {approx}> 7 galaxy candidates. This search takes advantage of an efficient preselection over 58 arcmin{sup 2} of NICMOS H{sub 160}-band data where only plausible z {approx}> 7 candidates are followed up with NICMOS J{sub 110}-band observations. {approx}248 arcmin{sup 2} of deep ground-based near-infrared data ({approx}>25.5 mag, 5{sigma}) are also considered in the search. In total, we report 15 z{sub 850}-dropout candidates over this area-7 of which are new to these search fields. Two possible z {approx} 9 J{sub 110}-dropout candidates are also found, but seem unlikely to correspond to z {approx} 9 galaxies (given the estimated contamination levels). The present z {approx} 9 search is used to set upper limits on the prevalence of such sources. Rigorous testing is undertaken to establish the level of contamination of our selections by photometric scatter, low-mass stars, supernovae, and spurious sources. The estimated contamination rate of our z {approx} 7 selection is {approx}24%. Through careful simulations, the effective volume available to our z {approx}> 7 selections is estimated and used to establish constraints on the volume density of luminous (L*{sub z{sub ={sub 3}}}, or {approx}-21 mag) galaxies from these searches. We find that the volume density of luminous star-forming galaxies at z {approx} 7 is 13{sup +8}{sub -5} times lower than at z {approx} 4 and >25 times lower (1{sigma}) at z {approx} 9 than at z {approx} 4. This is the most stringent constraint yet available on the volume density of {approx}>L*{sub z{sub ={sub 3}}} galaxies at z {approx} 9. The present wide-area, multi-field search limits cosmic variance to {approx}<20%. The evolution we find at the bright end of the UV LF is similar to that found from recent Subaru Suprime-Cam, HAWK-I or ERS WFC3/IR searches. The present paper also includes a complete summary of our final z {approx} 7 z{sub 850}-dropout sample (18 candidates) identified from all NICMOS observations to date (over the two GOODS fields, the HUDF, galaxy clusters).

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

THE X-RAY STAR FORMATION STORY AS TOLD BY LYMAN BREAK GALAXIES IN THE 4 Ms CDF-S

We present results from deep X-ray stacking of >4000 high-redshift galaxies from z Almost-Equal-To 1 to 8 using the 4 Ms Chandra Deep Field-South data, the deepest X-ray survey of the extragalactic sky to date. The galaxy samples were selected using the Lyman break technique based primarily on recent Hubble Space Telescope ACS and WFC3 observations. Based on such high specific star formation rates (sSFRs): log SFR/M {sub *} > -8.7, we expect that the observed properties of these Lyman break galaxies (LBGs) are dominated by young stellar populations. The X-ray emission in LBGs, eliminating individually detected X-ray sources (potential active galactic nucleus), is expected to be powered by X-ray binaries and hot gas. We find, for the first time, evidence of evolution in the X-ray/SFR relation. Based on X-ray stacking analyses for z < 4 LBGs (covering {approx}90% of the universe's history), we find that the 2-10 keV X-ray luminosity evolves weakly with redshift (z) and SFR as log L {sub X} = 0.93log (1 + z) + 0.65log SFR + 39.80. By comparing our observations with sophisticated X-ray binary population synthesis models, we interpret that the redshift evolution of L {sub X}/SFR is driven by metallicity evolution in high mass X-ray binaries, likely the dominant population in these high sSFR galaxies. We also compare these models with our observations of X-ray luminosity density (total 2-10 keV luminosity per Mpc{sup 3}) and find excellent agreement. While there are no significant stacked detections at z {approx}> 5, we use our upper limits from 5 {approx}< z {approx}< 8 LBGs to constrain the supermassive black hole accretion history of the universe around the epoch of reionization.

79 ASTRONOMY AND ASTROPHYSICS↗