| 1. |
- Aaltonen, T., et al.
(författare)
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Tevatron Run II combination of the effective leptonic electroweak mixing angle
- 2018
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Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 97:11
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Tidskriftsartikel (refereegranskat)abstract
- Drell-Yan lepton pairs produced in the process p (p) over bar -> l(+)l(-) + X through an intermediate gamma*/Z boson have an asymmetry in their angular distribution related to the spontaneous symmetry breaking of the electroweak force and the associated mixing of its neutral gauge bosons. The CDF and D0 experiments have measured the effective-leptonic electroweak mixing parameter sin(2) theta(lept)(eff) using electron and muon pairs selected from the full Tevatron proton-antiproton data sets collected in 2001-2011, corresponding to 9-10 fb(-1) of integrated luminosity. The combination of these measurements yields the most precise result from hadron colliders, sin(2)theta(lept)(eff) = 0.23148 +/- 0.00033. This result is consistent with, and approaches in precision, the best measurements from electron-positron colliders. The standard model inference of the on-shell electroweak mixing parameter sin(2) theta(W), or equivalently the W-boson mass M-W, using the ZFITTER software package yields sin(2) theta(W) = 0.22324 +/- 0.00033 or equivalently, M-W = 80.367 +/- 0.017 GeV/c(2).
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| 2. |
- Aaltonen, T., et al.
(författare)
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Combined Forward-Backward Asymmetry Measurements in Top-Antitop Quark Production at the Tevatron
- 2018
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Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 120:4
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Tidskriftsartikel (refereegranskat)abstract
- The CDF and D0 experiments at the Fermilab Tevatron have measured the asymmetry between yields of forward- and backward-produced top and antitop quarks based on their rapidity difference and the asymmetry between their decay leptons. These measurements use the full data sets collected in proton-antiproton collisions at a center-of-mass energy of root s = 1.96 TeV. We report the results of combinations of the inclusive asymmetries and their differential dependencies on relevant kinematic quantities. The combined inclusive asymmetry is A(FB)(t (t) over bar) = 0.128 +/- 0.025. The combined inclusive and differential asymmetries are consistent with recent standard model predictions.
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| 3. |
- Abazov, V. M., et al.
(författare)
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B-s(0) lifetime measurement in the CP-odd decay channel B-s(0) -> J/Psi f(0)(980)
- 2016
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Ingår i: PHYSICAL REVIEW D. - 2470-0010. ; 94:1
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Tidskriftsartikel (refereegranskat)abstract
- The lifetime of the B-s(0) meson is measured in the decay channel B-s(0) -> J/Psi pi(+)pi(-) with 880 <= M pi+pi- <= 1080 MeV/c(2), which is mainly a CP-odd state and dominated by the f(0)(980) resonance. In 10.4 fb(-1) of data collected with the D0 detector in Run II of the Tevatron, the lifetime of the B-s(0) meson is measured to be tau(B-s(0)) = 1.70 +/- 0.14(stat) +/- 0.05(syst) ps. Neglecting CP violation in B-s(0)/(B) over bar (0)(s) mixing, the measurement can be translated into the width of the heavy mass eigenstate of the B-s(0), Gamma(H) = 0.59 +/- 0.05(stat) +/- 0.02(syst) ps(-1).
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| 4. |
- Abazov, V. M., et al.
(författare)
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Combination of D0 measurements of the top quark mass
- 2017
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Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 95:11
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Tidskriftsartikel (refereegranskat)abstract
- We present a combination of measurements of the top quark mass by the D0 experiment in the lepton + jets and dilepton channels. We use all the data collected in Run I (1992-1996) at root s = 1.8 TeV and Run II (2001-2011) at root s = 1.96 TeV of the Tevatron p (p) over bar collider, corresponding to integrated luminosities of 0.1 fb(-1) and 9.7 fb(-1), respectively. The combined result is: m(t) = 174.95 +/- 0.40(stat)+/- 0.64(syst) GeV = 174.95 +/- 0.75 GeV.
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| 5. |
- Abazov, V. M., et al.
(författare)
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Evidence for a B-s(0)pi(+/-) State
- 2016
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 117:2
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Tidskriftsartikel (refereegranskat)abstract
- We report evidence for a narrow structure, X(5568), in the decay sequence X(5568) -> B-s(0)pi(+/-), B-s(0) -> J/psi phi, J/psi -> mu(+)mu(-), phi -> K+K-. This is evidence for the first instance of a hadronic state with valence quarks of four different flavors. The mass and natural width of this state are measured to be m = 5567.8 +/- 2.9(stat)(-1.9)(+0.9) (syst) MeV/c(2) and Gamma = 21.9 +/- 6.4(stat)(-2.5)(+5.0) (syst) MeV/c(2). If the decay is X(5568) -> B-s*pi(+/-). B-s(0)gamma pi(+/-) with an unseen gamma, m(X(5568)) will be shifted up by m(B-s*) - m(B-s(0)) similar to 49 MeV/c(2). This measurement is based on 10.4 fb(-1) of p (p) over bar collision data at root s = 1.96 TeV collected by the D0 experiment at the Fermilab Tevatron collider.
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| 6. |
- Abazov, V. M., et al.
(författare)
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Evidence for Z(c)(+/-)(3900) in semi-inclusive decays of b-flavored hadrons
- 2018
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Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 98:5
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Tidskriftsartikel (refereegranskat)abstract
- We present evidence for the exotic charged charmoniumlike state Z(c)(+/-)(3900) decaying to J/psi pi(+/-) in semi-inclusive weak decays of b-flavored hadrons. The signal is correlated with a parent J/psi pi(+)pi(-) system in the invariant-mass range 4.2-4.7 GeV that would include the exotic structure Y(4260). The study is based on 10.4 fb(-1) of p (p) over bar collision data collected by the D0 experiment at the Fermilab Tevatron collider.
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| 7. |
- Abazov, V. M., et al.
(författare)
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Measurement of the direct CP violating charge asymmetry in B-+/- -> mu(+/-)nu D-mu(0) decays
- 2017
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Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 95:3
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Tidskriftsartikel (refereegranskat)abstract
- We present the first measurement of the CP violating charge asymmetry in B-+/- -> mu(+/-)nu D-mu(0) decays using the full Run II integrated luminosity of 10.4 fb(-1) in proton-antiproton collisions collected with the D0 detector at the Fermilab Tevatron Collider. We measure a difference in the yield of B- and B+ mesons in these decays by fitting the reconstructed invariant mass distributions. This results in an asymmetry of A(mu D0) = [-0.14 +/- 0.20] %, which is consistent with standard model predictions.
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| 8. |
- Abazov, V. M., et al.
(författare)
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Measurement of the Effective Weak Mixing Angle in p¯p→Z/γ∗→ℓ+ℓ− Events
- 2018
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 120:24
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Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the effective weak mixing angle parameter sin(2)theta(l)(eff) in p (p) over bar -> Z/gamma* -> mu(+)mu(-) events at a center-of-mass energy of 1.96 TeV, collected by the D0 detector at the Fermilab Tevatron Collider and corresponding to 8.6 fb(-1) of integrated luminosity. The measured value of sin(2)theta(l)(eff)[mu mu] = 0.23016 +/- 0.00064 is further combined with the result from the D0 measurement in p (p) over bar -> Z/gamma* -> e(+)e(-) events, resulting in sin(2)theta(l)(eff)[comb] = 0.23095 +/- 0.00040. This combined result is the most precise measurement from a single experiment at a hadron collider and is the most precise determination using the coupling of the Z/gamma* to light quarks.
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| 9. |
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| 10. |
- Abazov, V. M., et al.
(författare)
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Measurement of the top quark mass using the matrix element technique in dilepton final states
- 2016
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Ingår i: PHYSICAL REVIEW D. - 2470-0010. ; 94:3
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Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the top quark mass in p (p) over bar collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. The data were collected by the D0 experiment corresponding to an integrated luminosity of 9.7 fb(-1). The matrix element technique is applied to t (t) over bar events in the final state containing leptons (electrons or muons) with high transverse momenta and at least two jets. The calibration of the jet energy scale determined in the lepton + jets final state of t (t) over bar decays is applied to jet energies. This correction provides a substantial reduction in systematic uncertainties. We obtain a top quark mass of m(t) = 173.93 +/- 1.84 GeV.
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| 11. |
- Abazov, V. M., et al.
(författare)
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Measurement of top quark polarization in t(t)over-bar lepton+jets final states
- 2017
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Ingår i: PHYSICAL REVIEW D. - 2470-0010. ; 95:1
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Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of top quark polarization in t (t) over bar pair production in p (p) over bar collisions at root s = 1.96 TeV using data corresponding to 9.7 fb(-1) of integrated luminosity recorded with the D0 detector at the Fermilab Tevatron Collider. We consider final states containing a lepton and at least three jets. The polarization is measured through the distribution of lepton angles along three axes: the beam axis, the helicity axis, and the transverse axis normal to the t (t) over bar production plane. This is the first measurement of top quark polarization at the Tevatron using lepton + jet final states and the first measurement of the transverse polarization in t (t) over bar production. The observed distributions are consistent with standard model predictions of nearly no polarization.
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| 12. |
- Abazov, V. M., et al.
(författare)
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Study of the X-+/-(5568) state with semileptonic decays of the B-s(0) meson
- 2018
-
Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 97:9
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of the X-+/-(5568) using semileptonic decays of the B-s(0) meson using the full run II integrated luminosity of 10.4 fb(-1) in proton-antiproton collisions at a center of mass energy of 1.96 TeV collected with the DO detector at the Fermilab Tevatron Collider. We report evidence for a narrow structure, X-+/-(5568), in the decay sequence X-+/-(5568) -> B-s(0) pi(+/-) where B-s(0)-> mu(-/+) (DsX)-X-+/-, D-s(+/-)-> phi pi(+/-)which is consistent with the previous measurement by the DO Collaboration in the hadronic decay mode, X-+/-(5568) -> B-s(0)pi(+/-) where B-s(0 )-> J/psi phi. The mass and width of this state are measured using a combined fit of the hadronic and semileptonic data, yielding m = 5566.9(-3.1)(+3.2)(stat)(-1.2)(+0.6)(syst) MeV/c(2), Gamma = 18.6(-6.1)(+7.9)(stat)(-3.8)(+3.5) (syst) McV/c(2) with a significance of 6.7 sigma.
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| 13. |
- Willerslev, E, et al.
(författare)
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Fifty thousand years of arctic vegetation change and megafauna diet
- 2014
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 506:7486, s. 47-47
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Tidskriftsartikel (refereegranskat)abstract
- Although it is generally agreed that the Arctic flora is among the youngest and least diverse on Earth, the processes that shaped it are poorly understood. Here we present 50 thousand years (kyr) of Arctic vegetation history, derived from the first large-scale ancient DNA metabarcoding study of circumpolar plant diversity. For this interval we also explore nematode diversity as a proxy for modelling vegetation cover and soil quality, and diets of herbivorous megafaunal mammals, many of which became extinct around 10 kyr bp (before present). For much of the period investigated, Arctic vegetation consisted of dry steppe-tundra dominated by forbs (non-graminoid herbaceous vascular plants). During the Last Glacial Maximum (25–15 kyr bp), diversity declined markedly, although forbs remained dominant. Much changed after 10 kyr bp, with the appearance of moist tundra dominated by woody plants and graminoids. Our analyses indicate that both graminoids and forbs would have featured in megafaunal diets. As such, our findings question the predominance of a Late Quaternary graminoid-dominated Arctic mammoth steppe.
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| 14. |
- Gizaw, A., et al.
(författare)
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Colonization and diversification in the African 'sky islands': insights from fossil-calibrated molecular dating of Lychnis (Caryophyllaceae)
- 2016
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 211:2, s. 719-734
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Tidskriftsartikel (refereegranskat)abstract
- The flora on the isolated high African mountains or 'sky islands' is remarkable for its peculiar adaptations, local endemism and striking biogeographical connections to remote parts of the world. Ages of the plant lineages and the timing of their radiations have frequently been debated but remain contentious as there are few estimates based on explicit models and fossil-calibrated molecular clocks. We used the plastid region maturaseK (matK) and a Caryophylloflora paleogenica fossil to infer the age of the genus Lychnis, and constructed a data set of three plastid (matK; a ribosomal protein S16 (rps16); and an intergenic spacer (psbE-petL)) and two nuclear (internal transcribed spacer (ITS) and a region spanning exon 18-24 in the second largest subunit of RNA polymerase II (RPB2)) loci for joint estimation of the species tree and divergence time of the African representatives. The time of divergence of the African high-altitude Lychnis was placed in the late Miocene to early Pliocene. A single speciation event was inferred in the early Pliocene; subsequent speciation took place sporadically from the late Pliocene to the middle Pleistocene. We provide further support for a Eurasian origin of the African 'sky islands' floral elements, which seem to have been recruited via dispersals at different times: some old, as in Lychnis, and others very recent. We show that dispersal and diversification within Africa play an important role in shaping these isolated plant communities.
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| 15. |
- Epp, L. S., et al.
(författare)
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New environmental metabarcodes for analysing soil DNA: potential for studying past and present ecosystems
- 2012
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Ingår i: Molecular Ecology. - 0962-1083. ; 21:8, s. 1821-1833
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Tidskriftsartikel (refereegranskat)abstract
- Metabarcoding approaches use total and typically degraded DNA from environmental samples to analyse biotic assemblages and can potentially be carried out for any kinds of organisms in an ecosystem. These analyses rely on specific markers, here called metabarcodes, which should be optimized for taxonomic resolution, minimal bias in amplification of the target organism group and short sequence length. Using bioinformatic tools, we developed metabarcodes for several groups of organisms: fungi, bryophytes, enchytraeids, beetles and birds. The ability of these metabarcodes to amplify the target groups was systematically evaluated by (i) in silico PCRs using all standard sequences in the EMBL public database as templates, (ii) in vitro PCRs of DNA extracts from surface soil samples from a site in Varanger, northern Norway and (iii) in vitro PCRs of DNA extracts from permanently frozen sediment samples of late-Pleistocene age (similar to 16 00050 000 years bp) from two Siberian sites, Duvanny Yar and Main River. Comparison of the results from the in silico PCR with those obtained in vitro showed that the in silico approach offered a reliable estimate of the suitability of a marker. All target groups were detected in the environmental DNA, but we found large variation in the level of detection among the groups and between modern and ancient samples. Success rates for the Pleistocene samples were highest for fungal DNA, whereas bryophyte, beetle and bird sequences could also be retrieved, but to a much lesser degree. The metabarcoding approach has considerable potential for biodiversity screening of modern samples and also as a palaeoecological tool.
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| 16. |
- Jørgensen, Tine, et al.
(författare)
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A comparative study of ancient sedimentary DNA, pollen and macrofossils from permafrost sediments of Northern Siberia reveals long-term vegetational stability
- 2012
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Ingår i: Molecular Ecology. - 0962-1083. ; 21:8, s. 1989-2003
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in Undetermined Although ancient DNA from sediments (sedaDNA) has been used to investigate past ecosystems, the approach has never been directly compared with the traditional methods of pollen and macrofossil analysis. We conducted a comparative survey of 18 ancient permafrost samples spanning the Late Pleistocene (4612.5 thousand years ago), from the Taymyr Peninsula in northern Siberia. The results show that pollen, macrofossils and sedaDNA are complementary rather than overlapping and, in combination, reveal more detailed information on plant palaeocommunities than can be achieved by each individual approach. SedaDNA and macrofossils share greater overlap in plant identifications than with pollen, suggesting that sedaDNA is local in origin. These two proxies also permit identification to lower taxonomic levels than pollen, enabling investigation into temporal changes in species composition and the determination of indicator species to describe environmental changes. Combining data from all three proxies reveals an area continually dominated by a mosaic vegetation of tundra-steppe, pioneer and wet-indicator plants. Such vegetational stability is unexpected, given the severe climate changes taking place in the Northern Hemisphere during this time, with changes in average annual temperatures of >22 degrees C. This may explain the abundance of ice-age mammals such as horse and bison in Taymyr Peninsula during the Pleistocene and why it acted as a refugium for the last mainland woolly mammoth. Our finding reveals the benefits of combining sedaDNA, pollen and macrofossil for palaeovegetational reconstruction and adds to the increasing evidence suggesting large areas of the Northern Hemisphere remained ecologically stable during the Late Pleistocene.
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| 17. |
- Parducci, Laura, et al.
(författare)
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Glacial Survival of Boreal Trees in Northern Scandinavia
- 2012
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 335:6072, s. 1083-1086
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Tidskriftsartikel (refereegranskat)abstract
- It is commonly believed that trees were absent in Scandinavia during the last glaciation and first recolonized the Scandinavian Peninsula with the retreat of its ice sheet some 9000 years ago. Here, we show the presence of a rare mitochondrial DNA haplotype of spruce that appears unique to Scandinavia and with its highest frequency to the west-an area believed to sustain ice-free refugia during most of the last ice age. We further show the survival of DNA from this haplotype in lake sediments and pollen of Trondelag in central Norway dating back similar to 10,300 years and chloroplast DNA of pine and spruce in lake sediments adjacent to the ice-free Andoya refugium in northwestern Norway as early as similar to 22,000 and 17,700 years ago, respectively. Our findings imply that conifer trees survived in ice-free refugia of Scandinavia during the last glaciation, challenging current views on survival and spread of trees as a response to climate changes.
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