9645951
Search for resonant top-antitop production in the lepton plus jets decay mode using the full CDF data set.
This Letter reports a search for a narrow resonant state decaying into two W bosons and two b quarks where one W boson decays leptonically and the other decays into a quark-antiquark pair. The search is particularly sensitive to top-antitop resonant production. We use the full data sample of proton-antiproton collisions at a center-of-mass energy of 1.96 TeV collected by the CDF II detector at the Fermilab Tevatron, corresponding to an integrated luminosity of 9.45 fb(-1). No evidence for resonant production is found, and upper limits on the production cross section times branching ratio for a narrow resonant state are extracted. Within a specific benchmark model, we exclude a Z' boson with mass, M(Z'), below 915 GeV/c(2) decaying into a top-antitop pair at the 95% credibility level assuming a Z' boson decay width of Γ(Z') = 0.012 M(Z'). This is the most sensitive search for a narrow qq-initiated tt resonance in the mass region below 750 GeV/c(2).
10189692
Combination of the top-quark mass measurements from the Tevatron collider
We thank the Fermilab staff and technical staffs of the 
participating institutions for their vital contributions and 
acknowledge support from the DOE and NSF (USA), ARC 
(Australia), CNPq, FAPERJ, FAPESP, and FUNDUNESP 
(Brazil), NSERC (Canada), NSC, CAS, and CNSF 
(China), Colciencias (Colombia), MSMT and GACR 
(Czech Republic), the Academy of Finland, CEA, and 
CNRS/IN2P3 (France), BMBF and DFG (Germany), 
DAE and DST (India), SFI (Ireland), INFN (Italy), 
MEXT (Japan), the Korean World Class University 
Program and NRF (Korea), CONACyT (Mexico), FOM 
(Netherlands), MON, NRC KI, and RFBR (Russia), the 
Slovak R&D Agency, the Ministerio de Ciencia e 
Innovacio´n, and Programa Consolider-Ingenio 2010 
(Spain), The Swedish Research Council (Sweden), SNSF 
(Switzerland), STFC and the Royal Society (United 
Kingdom), and the A. P. Sloan Foundation (USA).
118414507
Measurement of branching ratio and $B_s^0$ lifetime in the decay $B_s^0 \rightarrow J/\psi f_0(980)$ at CDF
We present a study of Bs0 decays to the CP-odd final state J/ψ f0(980) with J/ψ → µ+µ- and f0(980) → π+π-. Using pp collision data with an integrated luminosity of 3.8 fb-1 collected by the CDF II detector at the Tevatron we measure a Bs0 lifetime of τ(B0s → J/ψ f0(980)) = 1.70-0.11+0.12(stat) ± 0.03(syst) ps. This is the first measurement of the Bs0} lifetime in a decay to a CP eigenstate and corresponds in the standard model to the lifetime of the heavy Bs0 eigenstate. We also measure the product of branching fractions of B0s → J/ψ f0(980) and f0(980) → π+π- relative to the product of branching fractions of B0s → J/ψφ and φ→K+K- to be Rf0/ψ = 0.257 ± 0.020(stat) ± 0.014(syst), which is the most precise determination of this quantity to date.
123114924
ATLAS measurements of the properties of jets for boosted particle searches
Measurements are presented of the properties of high transverse momentum jets, produced in proton-proton collisions at a center-of-mass energy of root s = 7 TeV. The data correspond to an integrated luminosity of 35 pb(-1) and were collected with the ATLAS detector in 2010. Jet mass, width, eccentricity, planar flow and angularity are measured for jets reconstructed using the anti-k(t) algorithm with distance parameters R 0: 6 and 1.0, with transverse momentum p(T) > 300 GeV and pseudorapidity vertical bar eta vertical bar < 2. The measurements are compared to the expectations of Monte Carlo generators that match leading-logarithmic parton showers to leading-order, or next-to-leading-order, matrix elements. The generators describe the general features of the jets, although discrepancies are observed in some distributions.
122950163
The performance of the CDF luminosity monitor
Abstract We describe the initial performance of the detector used for the luminosity measurement in the CDF experiment in Run II at the Tevatron. The detector consists of low-mass gaseous Cherenkov counters with high light yield (∼100 photoelectrons) and monitors the process of inelastic p p scattering. It allows for several methods of precise luminosity measurements at peak instantaneous luminosities of 2×10 32 cm −2 s −1 , corresponding to an average of six p p interactions per bunch crossing.
12148304
Updated search for the standard model Higgs boson in events with jets and missing transverse energy using the full CDF data set
We present an updated search for the Higgs boson produced in association with a vector boson in the final state with missing transverse energy and two jets. We use the full CDF data set corresponding to an integrated luminosity of 9.45 fb−1 at a proton-antiproton center-of-mass energy of s√=1.96 TeV. New to this analysis is the inclusion of a b-jet identification algorithm specifically optimized for H→bb¯ searches. Across the Higgs boson mass range 90≤mH≤150 GeV/c2, the expected 95% credibility level upper limits on the VH production cross section times the H→bb¯ branching fraction are improved by an average of 14% relative to the previous analysis. At a Higgs boson mass of 125 GeV/c2, the observed (expected) limit is 3.06 (3.33) times the standard model prediction, corresponding to one of the most sensitive searches to date in this final state.
119629909
Is modified gravity required by observations? An empirical consistency test of dark energy models
We apply the technique of parameter splitting to existing cosmological data sets, to check for a generic failure of dark energy models. Given a dark energy parameter, such as the energy density {omega}{sub {lambda}} or equation of state w, we split it into two meta-parameters with one controlling geometrical distances, and the other controlling the growth of structure. Observational data spanning Type Ia Supernovae, the cosmic microwave background (CMB), galaxy clustering, and weak gravitational lensing statistics are fit without requiring the two meta-parameters to be equal. This technique checks for inconsistency between different data sets, as well as for internal inconsistency within any one data set (e.g., CMB or lensing statistics) that is sensitive to both geometry and growth. We find that the cosmological constant model is consistent with current data. Theories of modified gravity generally predict a relation between growth and geometry that is different from that of general relativity. Parameter splitting can be viewed as a crude way to parametrize the space of such theories. Our analysis of current data already appears to put sharp limits on these theories: assuming a flat universe, current data constrain the difference {delta}{omega}{sub {lambda}}={omega}{sub {lambda}}(geom)-{omega}{sub {lambda}}(grow) to be -0.0044{sub -0.0057-0.0119}{sup +0.0058+0.0108} (68%more » and 95% C.L. respectively); allowing the equation of state w to vary, the difference {delta}w=w(geom)-w(grow) is constrained to be 0.37{sub -0.36-0.53}{sup +0.37+1.09}. Interestingly, the region w(grow)>w(geom), which should be generically favored by theories that slow structure formation relative to general relativity, is quite restricted by data already. We find w(grow)<-0.80 at 2{sigma}. As an example, the best-fit flat Dvali-Gabadadze-Porrati model approximated by our parametrization lies beyond the 3{sigma} contour for constraints from all the data sets.« less
118632632
Heavy fragment radioactivity of Pu-238: Si and Mg emission
In addition to its two known hadronic decay modes\char22{}alpha decay (half-life 88 yr) and spontaneous fission (5\ifmmode\times\else\texttimes\fi{}${10}^{10}$ yr)\char22{}we have found that $^{238}\mathrm{Pu}$ also decays by emission of a Mg nucleus (\ensuremath{\sim}2\ifmmode\times\else\texttimes\fi{}${10}^{18}$ yr) and by emission of a Si nucleus (\ensuremath{\sim}6\ifmmode\times\else\texttimes\fi{}${10}^{17}$ yr). This extends to four (the other two being $^{14}\mathrm{C}$ emission and Ne emission) the number of known modes of decay by emission of a fragment of mass between that of an alpha particle and that resulting from fission. The branching ratios relative to alpha decay are the lowest yet observed: \ensuremath{\sim}6\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}17}$ for Mg emission and 1.4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}16}$ for Si emission.
17485528
Periodicities in Solar Coronal Mass Ejections
ABSTRACT Mid-term quasi-periodicities in solar coronal mass ejections (CMEs) during the mostrecent solar maximum cycle 23 are reported here for the ﬁrst time using the four-year data (February 5, 1999 to February 10, 2003) of the Large Angle SpectrometricCoronagraph (LASCO) onboard the Solar and Heliospheric Observatory (SOHO). Inparallel, mid-term quasi-periodicities in solar X-ray ﬂares (class >M5.0) from theGeosynchronous Operational Environment Satellites (GOES) and in daily averages ofAp index for geomagnetic disturbances from the World Data Center (WDC) at theInternationalAssociation for Geomagnetism andAeronomy (IAGA)are alsoexaminedfor the same four-year time span. By Fourier power spectral analyses, the CME dataappears to contain signiﬁcant power peaks at periods of ∼ 358 ± 38, ∼ 272 ± 26,∼ 196±13 days and so forth, while except for the ∼ 259±24-day period, X-ray solarﬂares of class >∼ M5.0 show the familiar Rieger-type quasi-periods at ∼ 157 ± 11,∼ 122± 5, ∼ 98±3 days and shorter ones until ∼ 34±0.5 days. In the data of dailyaverages of Ap index, the two signiﬁcant peaks at periods ∼ 273±26 and ∼ 187±12days (the latter is most prominent) could imply that CMEs (periods at ∼ 272±26and∼ 196 ± 13 days) may be proportionally correlated with quasi-periodic geomagneticstorm disturbances; at the speculative level, the ∼ 138 ± 6-day period might implythat X-ray ﬂares of class >∼ M5.0 (period at ∼ 157±11 days) may drive certain typesof geomagnetic disturbances; and the ∼ 28±0.2-day periodicity is most likely causedby recurrent high-speed solar winds at the Earth’s magnetosphere. For the same threedata sets, we further perform Morlet wavelet analysis to derive period-time contoursand identify wavelet power peaks and timescales at the 99 percent conﬁdence level forcomparisons. Several conceptual aspects of possible equatorially trapped Rossby-typewaves at and beneath the solar photosphere are discussed.Key words: oscillations — space weather — Sun: activities — corona — coronalmass ejections — magnetic ﬁelds
92988039
BEPC AND THE FUTURE PROGRAM AT IHEP
Beijing Electron and Positron Collider (BEPC), a 1.55— 2.8GeV accelerator facility serving for both high energy physics experiment and synchrotron radiation application, was constructed in the years from 1984 to 1988. The BEPC has been operating since 1989, in the meantime the BEPC upgrades were conducted and Beijing Tau-Charm Factory, a 1.5—2.5GeV double-ring collider was designed in the period from 1993 to 1996. In this paper, the BEPC and its current status are briefly introduced, the recent progress and the achieved results of the BEPC upgrade project are presented, and the future program of BTCF/BEPC-II is described.
201820079
SPECTRAL ENERGY DISTRIBUTIONS AND AGE ESTIMATES OF 104 M 31 GLOBULAR CLUSTERS
We present photometry of 104 M31 globular clusters (GCs) and GC candidates in 15 intermediate-band filters of the Beijing–Arizona–Taiwan–Connecticut photometric system. The GCs and GC candidates were selected from the Revised Bologna Catalog (v.3.5). We obtain the cluster ages by comparing the photometric data with up-to-date theoretical synthesis models. The photometric data used are Galaxy Evolution Explorer farand near-ultraviolet and Two Micron All Sky Survey near-infrared JHKs magnitudes, combined with optical photometry. The ages of our sample clusters cover a large range, although most clusters are younger than 10 Gyr. Combined with the ages obtained in our series of previous papers focusing on the M31 GC system, we present the full M31 GC age distribution. The M31 GC system contains populations of young and intermediate-age GCs, as well as the “usual” complement of well-known old GCs, i.e., GCs of similar age as the majority of the Galactic GCs. In addition, young GCs (and GC candidates) are distributed nearly uniformly in radial distance from the center of M31, while most old GCs (and GC candidates) are more strongly concentrated.