| 1. |
- Aamodt, K., et al.
(author)
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The ALICE experiment at the CERN LHC
- 2008
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In: Journal of Instrumentation. - 1748-0221. ; 3:S08002
-
Research review (peer-reviewed)abstract
- ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries, Its overall dimensions are 16 x 16 x 26 m(3) with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008.
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| 2. |
- Yu, G., et al.
(author)
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Structures, electronic states, photoluminescence, and carrier transport properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles
- 2005
-
In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 127:17, s. 6335-6346
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Research review (peer-reviewed)abstract
- The excellent electroluminescent (EL) properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles, 1-methyl-1,2,3,4,5-pentaphenylsilole (MPPS), and 1,1,2,3,4,5-hexaphenylsilole (HPS) have been found. Despite some studies devoted to these materials, very little is known about the real origin of their unique EL properties. Therefore, we investigated the structures, photoluminescence (PL), and charge carrier transport properties of 1,1-disubstituted 2,3,4,5-tetraphenylsiloles as well as the effect of substituents on these characteristics. The single crystals of the three siloles involving 1,1-dimethyl-2,3,4,5-tetraphenylsilole (DMTPS), MPPS, and HIPS were grown and their crystal structures were determined by X-ray diffraction. Three siloles have nonplanar molecular structures. The substituents at 1,1-positions enhance the steric hindrance and have predominant influence on the twisted degree of phenyl groups at ring carbons. This nonplanar structure reduces the intermolecular interaction and the likelihood of excimer formation, and increases PL efficiency in the solid state. The silole films show high fluorescence quantum yields (75-85%), whereas their dilute solutions exhibit a faint emission. The electronic structures of the three siloles were investigated using quantum chemical calculations. The highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs) are mainly localized on the silole ring and two phenyl groups at 2,5-positions in all cases, while the LUMOs have a significant orbital density at two exocyclic Si-C bonds. The extremely theoretical studies of luminescent properties were carried out. We calculated the nonradiative decay rate of the first excited state as well as the radiative one. It is found that the faint emission of DMTPS in solutions mainly results from the huge nonradiative decay rate. In solid states, molecular packing can remarkably restrict the intramolecular rotation of the peripheral side phenyl ring, which has a large contribution to the nonradiative transition process. This explains why the 1,1-disubstituted 2,3,4,5-tetraphenylsiloles in the thin films exhibit high fluorescence quantum yields. The charge carrier mobilities of the MPPS and HPS films were measured using a transient EL technique. We obtained a mobility of 2.1 x 10(-6) cm(2)/V(.)s in the MPPS film at an electric field of 1.2 x 10(6) V/cm. This mobility is comparable to that of Alq(3), which is one of the most extensively used electron transport materials in organic light-emitting diodes (LEDs), at the same electric field. The electron mobility of the HPS film is about similar to 1.5 times higher than that of the MPPS film. To the best of our knowledge, this kind of material is one of the most excellent emissive materials that possess both high charge carrier mobility and high PL efficiency in the solid states simultaneously. The excellent EL performances of MPPS and HPS are presumably ascribed to these characteristics.
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| 3. |
- Abazov, V. M., et al.
(author)
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Determination of the strong coupling constant from the inclusive jet cross section in pp collisions at s=1.96 TeV
- 2009
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In: PHYS REV D. - 1550-7998 .- 1550-2368. ; 80, s. 111107-
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Journal article (peer-reviewed)abstract
- We determine the strong coupling constant alpha(s) and its energy dependence from the p(T) dependence of the inclusive jet cross section in pp collisions at s=1.96 TeV. The strong coupling constant is determined over the transverse momentum range 50 < p(T)< 145 GeV. Using perturbative QCD calculations to order O(alpha(3)(s)) combined with O(alpha(4)(s)) contributions from threshold corrections, we obtain alpha(s)(M-Z)=0.1161(-0.0048)(+0.0041). This is the most precise result obtained at a hadron-hadron collider.
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| 4. |
- Abazov, V. M., et al.
(author)
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Evidence for the Decay B-s(0)->(DsDs(*))-D-(*) and a Measurement of Delta Gamma(CP)(s)/Gamma(s)
- 2009
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:9, s. 091801-
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Journal article (peer-reviewed)abstract
- We search for the semi-inclusive process B-s(0)->(DsDs(*))-D-(*) using 2.8 fb(-1) of pp collisions at s=1.96 TeV recorded by the D0 detector operating at the Fermilab Tevatron Collider. We observe 26.6 +/- 8.4 signal events with a significance above background of 3.2 standard deviations yielding a branching ratio of B(B-s(0)->(DsDs(*))-D-(*))=0.035 +/- 0.010(stat.)+/- 0.011(syst.). Under certain theoretical assumptions, these double-charm final states saturate CP-even eigenstates in the B-s(0) decays resulting in a width difference of Delta Gamma(CP)(s)/Gamma(s)=0.072 +/- 0.021(stat.)+/- 0.022(syst.).
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| 5. |
- Abazov, V. M., et al.
(author)
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Measurement of sigma(p(p)over-bar -> Z plus X)Br(Z -> tau(+)tau(-)) at root s=1.96 TeV
- 2009
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 670:4-5, s. 292-299
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Journal article (peer-reviewed)abstract
- We present a measurement of the cross section for Z boson production times the branching fraction to tau lepton pairs sigma(p (p) over bar -> Z + X)Br(Z -> tau(+)tau(-)) in p (p) over bar collisions at root s = 1.96 TeV. The measurement is performed in the channel in which one tau lepton decays into a muon and neutrinos. and the other tau lepton decays hadronically or into an electron and neutrinos. The data sample corresponds to an integrated luminosity of 1.0 fb(-1) collected with the DO detector at the Fermilab Tevatron Collider. The sample contains 1511 candidate events with an estimated 20% background from jets or muons misidentified as tau leptons. We obtain sigma . Br = 240 +/- 8 (star) +/- 12 (sys) +/- 15 (lum) pb, which is consistent with the standard model prediction.
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| 6. |
- Abazov, V. M., et al.
(author)
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Measurement of the Angular and Lifetime Parameters of the Decays B-d(0) -> J/psi K*(0) and B-s(0) -> J/psi phi
- 2009
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:3, s. 032001-:102, s. 032001-
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Journal article (peer-reviewed)abstract
- We present measurements of the linear polarization amplitudes and the strong relative phases that describe the flavor-untagged decays B-d(0) --> J/psi K*(0) and B-s(0) --> J/psi phi in the transversity basis. We also measure the mean lifetime (tau) over bar (s) of the B-s(0) mass eigenstates and the lifetime ratio (tau) over bar (s)/tau(d). The analyses are based on approximately 2.8 fb(-1) of data recorded with the D0 detector. From our measurements of the angular parameters we conclude that there is no evidence for a deviation from flavor SU( 3) symmetry for these decays and that the factorization assumption is not valid for the B-d(0) --> J/psi K*(0) decay.
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| 7. |
- Abazov, V. M., et al.
(author)
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Measurement of the top quark mass in final states with two leptons
- 2009
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In: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 80, s. 092006-
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Journal article (peer-reviewed)abstract
- We present measurements of the top quark mass (m(t)) in tt candidate events with two final state leptons using 1 fb(-1) of data collected by the D0 experiment. Our data sample is selected by requiring two fully identified leptons or by relaxing one lepton requirement to an isolated track if at least one jet is tagged as a b jet. The top quark mass is extracted after reconstructing the event kinematics under the tt hypothesis using two methods. In the first method, we integrate over expected neutrino rapidity distributions, and in the second we calculate a weight for the possible top quark masses based on the observed particle momenta and the known parton distribution functions. We analyze 83 candidate events in the data and obtain m(t)=176.2 +/- 4.8(stat)+/- 2.1(sys) GeV and m(t)=173.2 +/- 4.9(stat)+/- 2.0(sys) GeV for the two methods, respectively. Accounting for correlations between the two methods, we combine the measurements to obtain m(t)=174.7 +/- 4.4(stat)+/- 2.0(sys) GeV.
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| 8. |
- Abazov, V. M., et al.
(author)
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Observation of ZZ Production in p(p)over-bar Collisions at root s=1.96 TeV
- 2008
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 101:17, s. 171803-:101, s. 171803-
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Journal article (peer-reviewed)abstract
- We present an observation for ZZ -> l(+) l(-) l'(+) l'(-) (l, l' =e or mu) production in p (p) over bar collisions at a center-of-mass energy of root s = 1.96 TeV. Using 1.7 fb(-1) of data collected by the D0 experiment at the Fermilab Tevatron Collider, we observe three candidate events with an expected background of 0.14(-0.02)(+0.03) events. The significance of this observation is 5.3 standard deviations. The combination of D0 results in this channel, as well as in ZZ -> l(+) l(-) v (v) over bar yields a significance of 5.7 standard deviations and a combined cross section of sigma(ZZ) = 1.60 +/- 0.63(stat)(-0.17)(+0.16)(syst) pb.
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| 9. |
- Abazov, V. M., et al.
(author)
-
Search for a scalar or vector particle decaying into Z gamma in p(p)over-bar collisions at root s=1.96 TeV
- 2009
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 671:3, s. 349-355
-
Journal article (peer-reviewed)abstract
- We present a search for a narrow scalar or vector resonance decaying into Z gamma with a subsequent Z boson decay into a pair of electrons or moons. The data for this search were collected with the D circle divide detecror at the Fermilab Tevatron p (p) over bar collider at a center of mass energy root s = 1.96 TeV. Using 1.1 (1.0) fb(-1) of data, we observe 49 (50) candidate events in the electron (muon) channel, in good agreement with the standard model prediction. From the combination of both channels, we derive 95% C.L. upper limits on the cross section times branching fraction (sigma x B) into Z gamma. These limits range from 0.19 (0.20) pb for a scalar (vector) resonance mass of 600 GeV/c(2) to 2.5 (3.1) pb for a mass of 140 GeV/c(2).
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| 10. |
- Abazov, V. M., et al.
(author)
-
Search for Anomalous Top-Quark Couplings with the D0 Detector
- 2009
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:9, s. 092002-
-
Journal article (peer-reviewed)abstract
- Anomalous Wtb couplings modify the angular correlations of the top-quark decay products and change the single top-quark production cross section. We present limits on anomalous top-quark couplings by combining information from W boson helicity measurements in top-quark decays and anomalous coupling searches in the single top-quark final state. We set limits on right-handed vector couplings as well as left-handed and right-handed tensor couplings based on about 1 fb(-1) of data collected by the D0 experiment.
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| 11. |
- Abazov, V. M., et al.
(author)
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Search for Associated W and Higgs Boson Production in p(p)over-bar Collisions at root s=1.96 TeV
- 2009
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:5, s. 051803-:102, s. 051803-
-
Journal article (peer-reviewed)abstract
- We present results of a search for WH -> l nu b (b) over bar production in p (p) over bar collisions based on the analysis of 1.05 fb(-1) of data collected by the D0 experiment at the Fermilab Tevatron, using a neural network for separating the signal from backgrounds. No signal-like excess is observed, and we set 95% C. L. upper limits on the WH production cross section multiplied by the branching ratio for H -> b (b) over bar for Higgs boson masses between 100 and 150 GeV. For a mass of 115 GeV, we obtain an observed (expected) limit of 1.5 (1.4) pb, a factor of 11.4 (10.7) times larger than the standard model prediction.
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| 12. |
- Abazov, V. M., et al.
(author)
-
Search for charged Higgs bosons in top quark decays
- 2009
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 682:3, s. 278-286
-
Journal article (peer-reviewed)abstract
- We present a search for charged Higgs bosons in top quark decays. We analyze the e + jets, mu + jets, ee, e mu, mu mu, tau e and tau mu final states from top quark pair production events, using data from about 1 fb (1) of integrated luminosity recorded by the DO experiment at the Fermilab Tevatron Collider. We consider different scenarios of possible charged Higgs boson decays, one where the charged Higgs boson decays purely hadronically into a charm and a strange quark, another where it decays into a tau lepton and a tau neutrino and a third one where both decays appear. We extract limits on the branching ratio B(t -> H(+)b) for all these models. We use two methods, one where the t (t) over bar production cross section is fixed, and one where the cross section is fitted simultaneously with B(t -> H(+)b). Based on the extracted limits, we exclude regions in the charged Higgs boson mass and tan beta parameter space for different scenarios of the minimal supersymmetric standard model.
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| 13. |
- Abazov, V. M., et al.
(author)
-
Search for Large Extra Spatial Dimensions in the Dielectron and Diphoton Channels in p(p)over-bar Collisions at root s=1.96 TeV
- 2009
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:5, s. 051601-:102, s. 051601-
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Journal article (peer-reviewed)abstract
- We report on a search for large extra spatial dimensions in the dielectron and diphoton channels using a data sample of 1: 05 fb(-1) of p (p) over bar collisions at a center-of-mass energy of 1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider. The invariant mass spectrum of the data agrees well with the prediction of the standard model. We find the most restrictive 95% C. L. lower limits on the effective Planck scale between 2.1 and 1.3 TeV for 2 to 7 extra dimensions.
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| 14. |
- Abazov, V. M., et al.
(author)
-
Search for Neutral Higgs Bosons at High tan beta in the b(h/H/A) -> b tau(+)tau(-) Channel
- 2009
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:5, s. 051804-:102, s. 051804-
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Journal article (peer-reviewed)abstract
- The first search in p (p) over bar collisions at root s = 1.96 TeV for the production of neutral Higgs bosons in association with bottom quarks and decaying in two tau leptons is presented. The cross section for this process is enhanced in many extensions of the standard model, such as its minimal supersymmetric extension (MSSM) at large tan beta. The data, corresponding to an integrated luminosity of 328 pb(-1), were collected with the D0 detector at the Fermilab Tevatron Collider. An upper limit is set on the production cross section of neutral Higgs bosons in the mass range of 90 to 150 GeV, and this limit is used to exclude part of the MSSM parameter space.
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| 15. |
- Abazov, V. M., et al.
(author)
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Search for pair production of second generation scalar leptoquarks
- 2009
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 671:2, s. 224-232
-
Journal article (peer-reviewed)abstract
- We report on a search for the pair production of second generation scalar leptoquarks (LQ) in p (p) over bar collisions at the center of mass energy root s- = 1.96 TeV using a data set corresponding to an integrated luminosity of 1.0 fb(-1) collected with the D empty set experiment at the Fermilab Tevatron Collider. Topologies arising from the LQ (LQ) over bar -> mu q nu q and LQ (LQ) over bar -> mu q mu q decay modes are investigated. No excess of data over the standard model prediction is observed and upper limits on the leptoquark pair production cross section are derived at the 95% C.L. as a function of the leptoquark mass and the branching fraction beta for the decay LQ -> mu q. These are interpreted as lower limits on the leptoquark mass as a function of beta. For beta = 1 (0.5), scalar second generation leptoquarks with masses up to 316 GeV (270 GeV) are excluded.
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| 16. |
- Abazov, V. M., et al.
(author)
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Search for scalar neutrino superpartners in e+mu final states in p(p)over-bar collisions at root s=1.96 TeV
- 2008
-
In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 100:24, s. 241803-:100, s. 241803-
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Journal article (peer-reviewed)abstract
- We report a search for R-parity-violating production and decay of sneutrino particles in the e mu final state with 1.04 +/- 0.06 fb(-1) of data collected with the D-0 detector at the Fermilab Tevatron Collider in 2002-2006. Good agreement between the data and the standard model prediction is observed. With no evidence for new physics, we set limits on the R-parity-violating couplings lambda'(311) and lambda(312) as a function of the sneutrino mass.
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| 17. |
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| 18. |
- Li, P. L., et al.
(author)
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Preparation of aligned Ca3Co2O6 nanorods and their steplike magnetization
- 2007
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In: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 91:4, s. 042505-
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Journal article (peer-reviewed)abstract
- Well-aligned Ca3Co2O6 nanorods (similar to 300 nm in length and similar to 40 nm in diameter) on Si substrates are prepared by pulsed laser deposition. The steplike magnetization feature as identified in bulk Ca3Co2O6 can be retained in the nanorods in spite of the enhanced distortion of the magnetically ordered spin chains due to the finite size effect. The out-of-plane magnetization value is slightly larger than the in-plane value, which shows the small magnetic anisotropy. An additional distinct transition at 54 K associated with the spin frustration is revealed, different from the bulk samples. (C) 2007 American Institute of Physics.
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| 19. |
- Yin, Hong, et al.
(author)
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Preliminary Analysis of Drought/Flood Events in Early-Summer over the Central Shaanxi Plain during the Past 500 Years
- 2007
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In: Journal of Nanjing Institute of Meteorology. ; 30:1, s. 51-56
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Journal article (peer-reviewed)abstract
- In this study, the variation characteristics of extreme drought and flood events during the past 500 yearswere analyzed using the early2summer dryness indices series reconstructed by tree ring width chronologies of Huashan Pine samp led at the HuashanMountain. Comparisons between the dryness indices and the Palmer indices show that the dryness indices could be used to figure out the drought and flood events in the central Shaanxi p lain. There were 18 extreme droughts and 11 extreme floods events in earlysummer detected in this area during the past 500 years. Most of the events could be found in the historical documents, excep t that a flood event was detected from the dryness index but a drought event was recorded in the historical documents in A. D. 1521. There are also four eventswhich have no corresponding records in the historical documents in A. D. 1513, 1574, 1675 and 1945, respectively. Nine continuous drought periods and ten continuous flood periods are significant in the past 500 years. The drought and flood events occurred with high frequency in the sixteenth and the nineteenth centuries, but were less in the seventeenth and eighteenth centuries. The drought events are obviousmore than the flood events in the twentieth century
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| 20. |
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| 21. |
- Yu, X., et al.
(author)
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Association of UCP2 - 866 G/A polymorphism with chronic inflammatory diseases
- 2009
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In: Genes and Immunity. - : Springer Science and Business Media LLC. - 1466-4879 .- 1476-5470. ; 10:6, s. 601-605
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Journal article (peer-reviewed)abstract
- We reported earlier that two mitochondrial gene polymorphisms, UCP2 -866 G/A (rs659366) and mtDNA nt13708 G/A (rs28359178), are associated with multiple sclerosis (MS). Here we aim to investigate whether these functional polymorphisms contribute to other eight chronic inflammatory diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Wegener' granulomatosis (WG), Churg-Strauss syndrome (CSS), Crohn's disease (CD), ulcerative colitis (UC), primary sclerosing cholangitis (PSC) and psoriasis. Compared with individual control panels, the UCP2 -866 G/A polymorphism was associated with RA and SLE, and the mtDNA nt13708 G/A polymorphism with RA. Compared with combined controls, the UCP2 -866 G/A polymorphism was associated with SLE, WG, CD and UC. When all eight disease panels and the original MS panel were combined in a meta-analysis, the UCP2 was associated with chronic inflammatory diseases in terms of either alleles (odds ratio (OR)=0.91, 95% confidence interval (95% CI): 0.86-0.96), P=0.0003) or genotypes (OR=0.88, (95% CI: 0.82-0.95), P=0.0008), with the -866A allele associated with a decreased risk to diseases. As the -866A allele increases gene expression, our findings suggest a protective role of the UCP2 protein in chronic inflammatory diseases.
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