67 research outputs found
Measurement of the p-pbar -> Wgamma + X cross section at sqrt(s) = 1.96 TeV and WWgamma anomalous coupling limits
The WWgamma triple gauge boson coupling parameters are studied using p-pbar
-> l nu gamma + X (l = e,mu) events at sqrt(s) = 1.96 TeV. The data were
collected with the DO detector from an integrated luminosity of 162 pb^{-1}
delivered by the Fermilab Tevatron Collider. The cross section times branching
fraction for p-pbar -> W(gamma) + X -> l nu gamma + X with E_T^{gamma} > 8 GeV
and Delta R_{l gamma} > 0.7 is 14.8 +/- 1.6 (stat) +/- 1.0 (syst) +/- 1.0 (lum)
pb. The one-dimensional 95% confidence level limits on anomalous couplings are
-0.88 < Delta kappa_{gamma} < 0.96 and -0.20 < lambda_{gamma} < 0.20.Comment: Submitted to Phys. Rev. D Rapid Communication
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt{s} = 1.96 TeV using Kinematic Characteristics of Lepton + Jets Events
We present a measurement of the top quark pair ttbar production cross section
in ppbar collisions at a center-of-mass energy of 1.96 TeV using 230 pb**{-1}
of data collected by the DO detector at the Fermilab Tevatron Collider. We
select events with one charged lepton (electron or muon), large missing
transverse energy, and at least four jets, and extract the ttbar content of the
sample based on the kinematic characteristics of the events. For a top quark
mass of 175 GeV, we measure sigma(ttbar) = 6.7 {+1.4-1.3} (stat) {+1.6- 1.1}
(syst) +/-0.4 (lumi) pb, in good agreement with the standard model prediction.Comment: submitted to Phys.Rev.Let
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Lepton + Jets Events with Lifetime b-tagging
We present a measurement of the top quark pair () production cross
section () in collisions at TeV
using 230 pb of data collected by the D0 experiment at the Fermilab
Tevatron Collider. We select events with one charged lepton (electron or muon),
missing transverse energy, and jets in the final state. We employ
lifetime-based b-jet identification techniques to further enhance the
purity of the selected sample. For a top quark mass of 175 GeV, we
measure pb, in
agreement with the standard model expectation.Comment: 7 pages, 2 figures, 3 tables Submitted to Phys.Rev.Let
Measurement of the ratios of the Z/G* + >= n jet production cross sections to the total inclusive Z/G* cross section in ppbar collisions at sqrt(s) = 1.96 TeV
We present a study of events with Z bosons and jets produced at the Fermilab
Tevatron Collider in ppbar collisions at a center of mass energy of 1.96 TeV.
The data sample consists of nearly 14,000 Z/G* -> e+e- candidates corresponding
to the integrated luminosity of 0.4 fb-1 collected using the D0 detector.
Ratios of the Z/G* + >= n jet cross sections to the total inclusive Z/G* cross
section have been measured for n = 1 to 4 jet events. Our measurements are
found to be in good agreement with a next-to-leading order QCD calculation and
with a tree-level QCD prediction with parton shower simulation and
hadronization.Comment: 7 pages, 2 figures, slightly modified, submitted to Phys. Lett.
Measurement of the Isolated Photon Cross Section in p-pbar Collisions at sqrt{s}=1.96 TeV
The cross section for the inclusive production of isolated photons has been
measured in p anti-p collisions at sqrt{s}=1.96 TeV with the D0 detector at the
Fermilab Tevatron Collider. The photons span transverse momenta 23 to 300 GeV
and have pseudorapidity |eta|<0.9. The cross section is compared with the
results from two next-to-leading order perturbative QCD calculations. The
theoretical predictions agree with the measurement within uncertainties.Comment: 7 pages, 5 figures, submitted to Phys.Lett.
Competition between Allowed and First-Forbidden β Decay: The Case of Hg 208 → Tl 208
6 pags., 4 figs., 1 tab.The β decay of Hg208 into the one-proton hole, one neutron-particle Tl81208127 nucleus was investigated at CERN-ISOLDE. Shell-model calculations describe well the level scheme deduced, validating the proton-neutron interactions used, with implications for the whole of the N>126, Z<82 quadrant of neutron-rich nuclei. While both negative and positive parity states with spin 0 and 1 are expected within the Qβ window, only three negative parity states are populated directly in the β decay. The data provide a unique test of the competition between allowed Gamow-Teller and Fermi, and first-forbidden β decays, essential for the understanding of the nucleosynthesis of heavy nuclei in the rapid neutron capture process. Furthermore, the observation of the parity changing 0+→0-β decay where the daughter state is core excited is unique, and can provide information on mesonic corrections of effective operators.This work was supported by the European Union
under Contracts No. 262010 (ENSAR) and No. 654002
(ENSAR2), the Science and Technology Facilities
Council (UK), the German BMBF under Contract
No. 05P18PKCIA and “Verbundprojekt 05P2018,” the
MINECO Projects No. FPA2015-65035-P, No. RTI2018-
098868-B-I00, No. FPA2015-64969-P, and No. FPA2017-
87568-P (Spain), FWO-Vlaanderen (Belgium), GOA/
2015/010 (BOF KU Leuven), the Excellence of Science
programme (EOS-FWO), the Interuniversity Attraction
Poles Programme initiated by the Belgian Science Policy
Office (BriX network P7/12), the Romanian IFA project
CERN-RO/ISOLDE and the Polish National Science
Centre under Contracts No. UMO-2015/18/M/ST2/00523
and No. UMO-2019/33/N/ST2/03023. P. H. R. and
S. M. J. acknowledge support from the UK Department
for Business, Energy and Industrial Strategy via the
National Measurement Office. Zs. P. acknowledges support
from the ExtreMe Matter Institute EMMI at the GSI
Helmholtzzentrum fr Schwerionenforschung, Darmstadt,
Germa
First -decay spectroscopy of and new -decay branches of
19 pags., 14 figs., 3 tabs.The decay of the neutron-rich and was investigated experimentally in order to provide new insights into the nuclear structure of the tin isotopes with magic proton number above the shell. The -delayed -ray spectroscopy measurement was performed at the ISOLDE facility at CERN, where indium isotopes were selectively laser-ionized and on-line mass separated. Three -decay branches of were established, two of which were observed for the first time. Population of neutron-unbound states decaying via rays was identified in the two daughter nuclei of and , at excitation energies exceeding the neutron separation energy by 1 MeV. The -delayed one- and two-neutron emission branching ratios of were determined and compared with theoretical calculations. The -delayed one-neutron decay was observed to be dominant -decay branch of even though the Gamow-Teller resonance is located substantially above the two-neutron separation energy of . Transitions following the decay of are reported for the first time, including rays tentatively attributed to . In total, six new levels were identified in on the basis of the coincidences observed in the and decays. A transition that might be a candidate for deexciting the missing neutron single-particle state in was observed in both decays and its assignment is discussed. Experimental level schemes of and are compared with shell-model predictions. Using the fast timing technique, half-lives of the , and levels in were determined. From the lifetime of the state measured for the first time, an unexpectedly large transition strength was deduced, which is not reproduced by the shell-model calculations.M.P.-S. acknowledges the funding support from the Polish National Science Center under Grants No.
2019/33/N/ST2/03023 and No. 2020/36/T/ST2/00547 (Doctoral scholarship ETIUDA). J.B. acknowledges
support from the Universidad Complutense de Madrid under the Predoctoral Grant No. CT27/16-
CT28/16. This work was partially funded by the Polish National Science Center under Grants No.
2020/39/B/ST2/02346, No. 2015/18/E/ST2/00217, and No. 2015/18/M/ST2/00523, by the Spanish
government via Projects No. FPA2017-87568-P, No. RTI2018-098868-B-I00, No. PID2019-104390GB-I00,
and No. PID2019-104714GB-C21, by the U.K. Science and Technology Facilities Council (STFC), the German BMBF
under Contract No. 05P18PKCIA, by the Portuguese FCT under the Projects No. CERN/FIS-PAR/0005/2017, and
No. CERN/FIS-TEC/0003/2019, and by the Romanian IFA Grant CERN/ISOLDE. The research leading to these
results has received funding from the European Union’s Horizon 2020 research and innovation programme under
Grant Agreement No. 654002. M.Str. acknowledges the funding from the European Union’s Horizon 2020 research
and innovation program under Grant Agreement No. 771036 (ERC CoG MAIDEN). J.P. acknowledges support from the
Academy of Finland (Finland) with Grant No. 307685. Work at the University of York was supported under STFC Grants
No. ST/L005727/1 and No. ST/P003885/1
Search for single top quark production in ppbar collisions at sqrt(s)=1.96 TeV
We present a search for electroweak production of single top quarks in the
s-channel and t-channel using neural networks for signal-background separation.
We have analyzed 230 pb of data collected with the D0 detector at the
Fermilab Tevatron Collider at a center-of-mass energy of 1.96 TeV and find no
evidence for a single top quark signal. The resulting 95% confidence level
upper limits on the single top quark production cross sections are 6.4 pb in
the s-channel and 5.0 pb in the t-channel.Comment: 9 pages, 4 figure
Measurement of the Lambda^0_b lifetime in the decay Lambda^0_b -> J/psi Lambda^0 with the D0 Detector
We present measurements of the Lambda^0_b lifetime in the exclusive decay
channel Lambda^0_{b}->J/psi Lambda^0, with J/psi to mu+ mu- and Lambda^0 to p
pi-, the B^0 lifetime in the decay B^0 -> J/psi K^0_S with J/psi to mu+ mu- and
K^0_S to pi+ pi-, and the ratio of these lifetimes. The analysis is based on
approximately 250 pb^{-1} of data recorded with the D0 detector in pp(bar)
collisions at sqrt{s}=1.96 TeV. The Lambda^0_b lifetime is determined to be
tau(Lambda^0_b) = 1.22 +0.22/-0.18 (stat) +/- 0.04 (syst) ps, the B^0 lifetime
tau(B^0) = 1.40 +0.11/-0.10 (stat) +/- 0.03 (syst) ps, and the ratio
tau(Lambda^0_b)/tau(B^0) = 0.87 +0.17/-0.14 (stat) +/- 0.03 (syst). In contrast
with previous measurements using semileptonic decays, this is the first
determination of the Lambda^0_b lifetime based on a fully reconstructed decay
channel.Comment: 7 pages, 4 figures, Submitted to Physical Review Letters, v2: Added
FNAL Pub-numbe
Measurement of the WW production cross section in p anti-p collisions at s**(1/2) = 1.96 TeV
We present a measurement of the W boson pair-production cross section in p
anti-p collisions at a center-of-mass energy of sqrt{s}=1.96 TeV. The data,
collected with the Run II DO detector, correspond to an integrated luminosity
of 224-252 pb^-1 depending on the final state (ee, emu or mumu). We observe 25
candidates with a background expectation of
8.1+/-0.6(stat)+/-0.6(syst)+/-0.5(lum) events. The probability for an upward
fluctuation of the background to produce the observed signal is 2.3x10^-7,
equivalent to 5.2 standard deviations.The measurement yields a cross section of
13.8+4.3/-3.8(stat)+1.2/-0.9(syst)+/-0.9(lum) pb, in agreement with predictions
from the standard model.Comment: submitted to PR
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