Viral RNA exported from the coronavirus replication organelle is likely to be mediated by a crown-shaped molecular pore.
A gateway to the cytosol
Coronaviruses transform host cell membranes into ...peculiar double-membrane vesicles that have long been thought to accommodate viral genome replication. However, because these compartments appeared to be completely sealed, it has remained unknown how the newly made viral RNA could be exported to the cytosol for translation and packaging into new virions. Wolff
et al.
used cryo–electron microscopy to identify a molecular pore that spans the double membrane (see the Perspective by Unchwaniwala and Ahlquist). Six copies of a large coronavirus transmembrane protein formed the core of this structure, which may constitute a viral RNA export channel and provide a target for future antiviral interventions.
Science
, this issue p.
1395
; see also p.
1306
Coronavirus genome replication is associated with virus-induced cytosolic double-membrane vesicles, which may provide a tailored microenvironment for viral RNA synthesis in the infected cell. However, it is unclear how newly synthesized genomes and messenger RNAs can travel from these sealed replication compartments to the cytosol to ensure their translation and the assembly of progeny virions. In this study, we used cellular cryo–electron microscopy to visualize a molecular pore complex that spans both membranes of the double-membrane vesicle and would allow export of RNA to the cytosol. A hexameric assembly of a large viral transmembrane protein was found to form the core of the crown-shaped complex. This coronavirus-specific structure likely plays a key role in coronavirus replication and thus constitutes a potential drug target.
We present the observation of doubly-produced $J/\psi$ mesons with the D0 detector at Fermilab in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV. The production cross section for both singly and ...doubly-produced $J/\psi$ mesons is measured using a sample with an integrated luminosity of 8.1~fb$^{-1}$. For the first time, the double $J/\psi$ production cross section is separated into contributions due to single and double parton scatterings. Using these measurements, we determine the effective cross section \sigteff, a parameter characterizing an effective spatial area of the parton-parton interactions and related to the parton spatial density inside the nucleon.
The compatibility of
W
-boson mass measurements performed by the ATLAS, LHCb, CDF, and D0 experiments is studied using a coherent framework with theory uncertainty correlations. The measurements are ...combined using a number of recent sets of parton distribution functions (PDF), and are further combined with the average value of measurements from the Large Electron–Positron collider. The considered PDF sets generally have a low compatibility with a suite of global rapidity-sensitive Drell–Yan measurements. The most compatible set is CT18 due to its larger uncertainties. A combination of all
m
W
measurements yields a value of
m
W
=
80
,
394.6
±
11.5
MeV with the CT18 set, but has a probability of compatibility of 0.5% and is therefore disfavoured. Combinations are performed removing each measurement individually, and a 91% probability of compatibility is obtained when the CDF measurement is removed. The corresponding value of the
W
boson mass is
80
,
369.2
±
13.3
MeV, which differs by
3.6
σ
from the CDF value determined using the same PDF set.
ZFITTER is a Fortran program for the calculation of fermion pair production and radiative corrections at high energy
e
+
e
−
colliders; it is also suitable for other applications where electroweak ...radiative corrections appear.
ZFITTER is based on a semi-analytical approach to the calculation of radiative corrections in the Standard Model. We present a summary of new features of the
ZFITTER program version 6.42 compared to version 6.21. The most important additions are: (i) some higher-order QED corrections to fermion pair production, (ii) electroweak one-loop corrections to atomic parity violation, (iii) electroweak one-loop corrections to
ν
¯
e
ν
e
production, (iv) electroweak two-loop corrections to the
W boson mass and the effective weak mixing angle.
Title of program:
ZFITTER version 6.42 (18 May 2005)
Catalogue identifier:ADMJ_v2_0
Program summary URL:
http://cpc.cs.qub.ac.uk/summaries/ADMJ_v2_0
Authors of original program: D. Bardin, P. Christova, M. Jack, L. Kalinovskaya, A. Olshevski, S. Riemann, T. Riemann
Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland
Reference for
ZFITTER version 6.21:
D. Bardin et al., Comput. Phys. Comm. 133 (2001) 229–395
Operating system:
UNIX/LINUX, program tested under, e.g.,
HP-UX and
PC/Linux
Programming language used:
FORTRAN 77
High speed storage required: <2 MB
No. of lines in distributed program, including test data, etc.:29 164
No. of bytes in distributed program, including test data, etc.:185 824
Distribution format:tar.gz
Does the new version supersede the previous version:Yes
Nature of the physical problem: Fermion pair production is an important reaction for precision tests of the Standard Model, at LEP/SLC and future linear colliders at higher energies. For this purpose, QED, electroweak and QCD radiative corrections have to be calculated with high precision, including higher order effects. Multi parameter fits used to extract model parameters from experimental measurements require a program of sufficient flexibility and high calculational speed.
ZFITTER combines these two aspects by employing analytical integrations of matrix elements and at most one-dimensional numerical integration, as well as a variety of flags defining the physics content used. The calculated predictions are typically at the per mille precision level, sometimes better.
Method of solution: Numerical integration of analytical formulae.
Reasons for new version:Addition of substantial material into the code: covering of more reactions; more accurate description of existing reactions.
Summary of revisions:New parts for predicting atomic parity violation and for neutrino pair production; more accurate higher order QED corrections for fermion pair production; two-loop corrections to the predictions of
W mass and of the weak mixing angle.
Restrictions on the complexity of the problem: Fermion pair production is described below the top quark pair production threshold. Photonic corrections are taken into account with simple cuts on photon energy, or the energies and acollinearity of the two fermions, and
one fermion production angle. The treatment of Bhabha scattering is less advanced.
Typical running time: On a Pentium IV PC installation (2.8 GHz) using g77 under Linux 2.4.21, approximately 23 s are needed to run the standard test of subroutine
ZFTEST. This result is for a
default/recommended setting of the input parameters, with
all corrections in the Standard Model switched
on.
ZFTEST computes 12 cross-sections and cross-section asymmetries for 8 energies with 5 interfaces, i.e. about 360 cross-sections in 23 s.
We present a measurement of the fundamental parameter of the standard model, the weak mixing angle sin2θℓeff which determines the relative strength of weak and electromagnetic interactions, in ...pp¯→Z/γ*→e+e- events at a center of mass energy of 1.96 TeV, using data corresponding to 9.7 fb-1 of integrated luminosity collected by the D0 detector at the Fermilab Tevatron. The effective weak mixing angle is extracted from the forward-backward charge asymmetry as a function of the invariant mass around the Z boson pole. The measured value of sin2θℓeff=0.23147±0.00047 is the most precise measurement from light quark interactions to date, with a precision close to the best LEP and SLD results.
Here, the inclusive cross section of top quark-antiquark pairs produced in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV is measured in the lepton+jets and dilepton decay channels. The data sample ...corresponds to 9.7 fb-1 of integrated luminosity recorded with the D0 detector during Run II of the Fermilab Tevatron Collider. Employing multivariate analysis techniques we measure the cross section in the two decay channels and we perform a combined cross section measurement. For a top quark mass of 172.5 GeV, we measure a combined inclusive top quark-antiquark pair production cross section of σ$t\bar{t}$=7.26±0.13(stat)$+0.57\atop{-0.50}$(syst) pb which is consistent with standard model predictions. We also perform a likelihood fit to the measured and predicted top quark mass dependence of the inclusive cross section, which yields a measurement of the pole mass of the top quark. The extracted value is mt=172.8±1.1(theo)$+3.3\atop{-3.1}$(exp) GeV.
We present measurements of the cross sections for the two main production modes of single top quarks in pp¯ collisions at s=1.96 TeV in the Run II data collected with the D0 detector at the Fermilab ...Tevatron Collider, corresponding to an integrated luminosity of 9.7 fb−1. The s-channel cross section is measured to be σ(pp¯→tb+X)=1.10−0.31+0.33 pb with no assumptions on the value of the t-channel cross section. Similarly, the t-channel cross section is measured to be σ(pp¯→tqb+X)=3.07−0.49+0.54 pb. We also measure the s+t combined cross section as σ(pp¯→tb+X,tqb+X)=4.11−0.55+0.60 pb and set a lower limit on the CKM matrix element |Vtb|>0.92 at 95% C.L., assuming mt=172.5 GeV. The probability to measure a cross section for the s channel at the observed value or higher in the absence of signal is 1.0×10−4, corresponding to a significance of 3.7 standard deviations.
We present a measurement of the correlation between the spins of t and t¯ quarks produced in proton–antiproton collisions at the Tevatron Collider at a center-of-mass energy of 1.96 TeV. We apply a ...matrix element technique to dilepton and single-lepton+jets final states in data accumulated with the D0 detector that correspond to an integrated luminosity of 9.7 fb−1. The measured value of the correlation coefficient in the off-diagonal basis, Ooff=0.89±0.22(stat+syst), is in agreement with the standard model prediction, and represents evidence for a top–antitop quark spin correlation difference from zero at a level of 4.2 standard deviations.
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