1,247 research outputs found
One-neutron knockout from Ni
The single-particle structure of Ni and level structure of Ni
were investigated with the \mbox{Be (Ni,Ni+)} reaction at 73 MeV/nucleon. An inclusive cross
section of 41.4(12) mb was obtained for the reaction, compared to a theoretical
prediction of 85.4 mb, hence only 48(2)% of the theoretical cross section is
exhausted. This reduction in the observed spectroscopic strength is consistent
with that found for lighter well-bound nuclei. One-neutron removal
spectroscopic factors of 0.58(11) to the ground state and 3.7(2) to all excited
states of Ni were deduced.Comment: Phys. Rev. C, accepte
Evolution of the energy spacing in odd-mass K, Cl and P isotopes for
The energy of the first excited state in the neutron-rich N=28 nucleus 45Cl
has been established via in-beam gamma-ray spectroscopy following proton
removal. This energy value completes the systematics of the
E(1/2^+_1)-E(3/2^+_1) level spacing in odd-mass K, Cl and P isotopes for
N=20-28. The results are discussed in the framework of shell-model calculations
in the sd-fp model space. The contribution of the central, spin-orbit and
tensor components is discussed from a calculation based on a proton single-hole
spectrum from G-matrix and pi + rho meson exchange potentials. A composite
model for the proton 0d_{3/2}-1s_{1/2} single-particle energy shift is
presented.Comment: Phys. Rev. C, in pres
Variation with mass of \boldmath{B(E3; 0_1^+ \to 3_1^-)} transition rates in even-mass xenon nuclei
transition matrix elements have been measured for
even-mass Xe nuclei using sub-barrier Coulomb excitation in inverse
kinematics. The trends in energy and
excitation strengths are well reproduced using phenomenological models based on
a strong coupling picture with a soft quadrupole mode and an increasing
occupation of the intruder orbital.Comment: 5 pages, 4 figures, PRC in pres
Search for right-handed W bosons in top quark decay
We present a measurement of the fraction f+ of right-handed W bosons produced
in top quark decays, based on a candidate sample of events in the
lepton+jets decay mode. These data correspond to an integrated luminosity of
230pb^-1, collected by the DO detector at the Fermilab Tevatron
Collider at sqrt(s)=1.96 TeV. We use a constrained fit to reconstruct the
kinematics of the and decay products, which allows for the
measurement of the leptonic decay angle for each event. By comparing
the distribution from the data with those for the expected
background and signal for various values of f+, we find
f+=0.00+-0.13(stat)+-0.07(syst). This measurement is consistent with the
standard model prediction of f+=3.6x10^-4.Comment: Submitted to Physical Review D Rapid Communications 7 pages, 3
figure
Measurement of Semileptonic Branching Fractions of B Mesons to Narrow D** States
Using the data accumulated in 2002-2004 with the DO detector in
proton-antiproton collisions at the Fermilab Tevatron collider with
centre-of-mass energy 1.96 TeV, the branching fractions of the decays B ->
\bar{D}_1^0(2420) \mu^+ \nu_\mu X and B -> \bar{D}_2^{*0}(2460) \mu^+ \nu_\mu X
and their ratio have been measured: BR(\bar{b}->B) \cdot BR(B-> \bar{D}_1^0
\mu^+ \nu_\mu X) \cdot BR(\bar{D}_1^0 -> D*- pi+) =
(0.087+-0.007(stat)+-0.014(syst))%; BR(\bar{b}->B)\cdot BR(B->D_2^{*0} \mu^+
\nu_\mu X) \cdot BR(\bar{D}_2^{*0} -> D*- \pi^+) =
(0.035+-0.007(stat)+-0.008(syst))%; and (BR(B -> \bar{D}_2^{*0} \mu^+ \nu_\mu
X)BR(D2*0->D*- pi+)) / (BR(B -> \bar{D}_1^{0} \mu^+ \nu_\mu X)\cdot
BR(\bar{D}_1^{0}->D*- \pi^+)) = 0.39+-0.09(stat)+-0.12(syst), where the charge
conjugated states are always implied.Comment: submitted to Phys. Rev. Let
Measurement of the Lifetime Difference in the B_s^0 System
We present a study of the decay B_s^0 -> J/psi phi We obtain the CP-odd
fraction in the final state at time zero, R_perp = 0.16 +/- 0.10 (stat) +/-
0.02 (syst), the average lifetime of the (B_s, B_sbar) system, tau (B_s^0)
=1.39^{+0.13}_{-0.16} (stat) ^{+0.01}_{-0.02} (syst) ps, and the relative width
difference between the heavy and light mass eigenstates, Delta Gamma/Gamma =
(Gamma_L - Gamma_H)/Gamma =0.24^{+0.28}_{-0.38} (stat) ^{+0.03}_{-0.04} (syst).
With the additional constraint from the world average of the B_s^0$lifetime
measurements using semileptonic decays, we find tau (B_s^0)= 1.39 +/- 0.06 ~ps
and Delta Gamma/\Gamma = 0.25^{+0.14}_{-0.15}. For the ratio of the B_s^0 and
B^0 lifetimes we obtain tau(B_s^0)/tau(B^0)} = 0.91 +/- 0.09 (stat) +/- 0.003
(syst).Comment: submitted to Phys. Rev. Lett. FERMILAB-PUB-05-324-
Search for Large Extra Spatial Dimensions in Dimuon Production with the D0 Detector
We present the results of a search for the effects of large extra spatial
dimensions in collisions at 1.96 TeV in events
containing a pair of energetic muons. The data correspond to 246 \ipb of
integrated luminosity collected by the \D0 experiment at the Fermilab Tevatron
Collider. Good agreement with the expected background was found, yielding no
evidence for large extra dimensions. We set 95% C.L. lower limits on the
fundamental Planck scale between 0.85 TeV and 1.27 TeV within several
formalisms. These are the most stringent limits achieved in the dimuon channel
to date.Comment: 8 pages, 3 figures, 1 table. Published in Phys. Rev. Lett. Minor
changes in v2 to match the published versio
Search for R-parity violating supersymmetry via the LLE couplings lambda_{121}, lambda_{122} or lambda_{133} in ppbar collisions at sqrt(s)=1.96 TeV
A search for gaugino pair production with a trilepton signature in the
framework of R-parity violating supersymmetry via the couplings lambda_121,
lambda_122, or lambda_133 is presented. The data, corresponding to an
integrated luminosity of L~360/pb, were collected from April 2002 to August
2004 with the D0 detector at the Fermilab Tevatron Collider, at a
center-of-mass energy of sqrt(s)=1.96 TeV. This analysis considers final states
with three charged leptons with the flavor combinations eel, mumul, and eetau
(l=e or mu). No evidence for supersymmetry is found and limits at the 95%
confidence level are set on the gaugino pair production cross section and lower
bounds on the masses of the lightest neutralino and chargino are derived in two
supersymmetric models.Comment: 9 pages, 4 figures (fig2 includes 3 subfigures
Search for W' boson production in the W'->tb decay channel
We present a search for the production of a new heavy gauge boson W' that
decays to a top quark and a bottom quark. We have analyzed 230 pb^{-1} of data
collected with the Dzero detector at the Fermilab Tevatron collider at a
center-of-mass energy of 1.96 TeV. No significant excess of events above the
standard model expectation is found in any region of the final state invariant
mass distribution. We set upper limits on the production cross section of W'
bosons times branching ratio to top quarks at the 95% confidence level for
several different W' boson masses. We exclude masses between 200 GeV and 610
GeV for a W' boson with standard-model-like couplings, between 200 GeV and 630
GeV for a W' boson with right-handed couplings that is allowed to decay to both
leptons and quarks, and between 200 GeV and 670 GeV for a W' boson with
right-handed couplings that is only allowed to decay to quarks.Comment: 9 pages, 6 figures, accepted by Phys. Lett.
A search for W bb and W Higgs production in ppbar collisions at sqrt(s)=1.96 TeV
We present a search for W b \bar{b} production in p \bar{p} collisions at
sqrt{s}=1.96 TeV in events containing one electron, an imbalance in transverse
momentum, and two b-tagged jets. Using 174 pb-1 of integrated luminosity
accumulated by the D0 experiment at the Fermilab Tevatron collider, and the
standard-model description of such events, we set a 95% C.L. upper limit on W b
\bar{b}WH--$135
GeV.Comment: 7 pages, 4 figures, 1 table, submitted to Physical Review Letter
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