A single fast radio burst localized to a massive galaxy at cosmological distance

Fast radio bursts (FRBs) are brief radio emissions from distant astronomical sources. Some are known to repeat, but most are single bursts. Nonrepeating FRB observations have had insufficient positional accuracy to localize them to an individual host galaxy. We report the interferometric localization of the single-pulse FRB 180924 to a position 4 kiloparsecs from the center of a luminous galaxy at redshift 0.3214. The burst has not been observed to repeat. The properties of the burst and its host are markedly different from those of the only other accurately localized FRB source. The integrated electron column density along the line of sight closely matches models of the intergalactic medium, indicating that some FRBs are clean probes of the baryonic component of the cosmic web.

Prognostic value of autoantibodies (auto-AB) in melanoma patients (pts) in the EORTC 18952 trial of adjuvant interferon (IFN) compared to observation (obs)

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Background: Appearance of auto-AB during IFN-adjuvant therapy is a prognostic factor in melanoma pts. We evaluated this in the EORTC 18952 trial including pts without IFN. Methods: Anti-cardiolipin (C) anti-thyreoglobulin (T) and anti- nuclear (N) AB levels of serial samples between 0 and 48 months (mt) were assessed centrally. Prognostic impact of CTN on relapse-free survival (RFS) was assessed by 3 methods: 1) usual Cox model (lead-time bias); 2) Cox Time dependent model using the latest positive CTN value; 3) Cox Time dependent model using the latest any CTN value. Results: In 278 pts the presence of auto-AB at any time was determined. Among them, 187 pts (43 stage IIb, 144 stage III), Obs (32) or 13-mt-IFN (80) or 25-mt-IFN (75), had their initial auto- AB status assessed: 60 (32%) were CTN-positive (pos) (similar % in 3 arms) and 127 (68%) were CTN-negative (neg). Of these 127 pts, during the study, at least once, the following became CTN-pos: Obs (7/24=29%), 13-mt-IFN (19/55=36%), 25-mt-IFN (20/48=42%); 1-yr conversion rate was 23%, 34% and 38% in the 3 arms respectively; 2-yr rate was 23%, 46% and 61%. Median follow-up = 4.2 yrs. Relapse occurred in 122/187 pts. Median RFS = 2.1 years. In the 187 pts with a known initial CTN-status, using the classical Cox model the hazard ratio (HR) of those who were/became CTN-pos vs the others, was 0.50. In order to overcome the Lead Time Bias, the Cox time dependent model was used: the HR for pts with at least one pos CTN-status vs always CTN-neg was 0.63 and for those with the latest CTN-status pos vs those with latest CTN-status neg was 0.87. All analyses were adjusted for # of pos nodes. Results were similar when only IFN pts or Obs only pts were considered (test for interaction: P>0.50), or when all pts (278) or only pts CTN-neg at randomization (127) were assessed. Initial CTN status known. Conclusions: We could not confirm presence or appearance of auto-AB as a strong prognostic factor in melanoma pts and did not find a strong interaction with IFN therapy.

[Table: see text] [Table: see text]

Measurement of the tensor structure function b1 of the deuteron

The Hermes experiment has investigated the tensor spin structure of the deuteron using the 27.6 GeV/c positron beam of DESY HERA. The use of a tensor-polarized deuteron gas target with only a negligible residual vector polarization enabled the first measurement of the tensor asymmetry A(d)zz and the tensor structure function b(d)1 for average values of the Bjorken variable 0.01< <x> <0.45 and of the negative of the squared four-momentum transfer 0.5 GeV2 < <Q2> <5 GeV2. The quantities A(d)zz and b(d)1 are found to be nonzero. The rise of b(d)1 for decreasing values of x can be interpreted to originate from the same mechanism that leads to nuclear shadowing in unpolarized scattering.

Single-spin asymmetries in semi-inclusive deep-inelastic scattering on a transversely polarized hydrogen target

Single-spin asymmetries for semi-inclusive electroproduction of charged pions in deep-inelastic scattering of positrons are measured for the first time with transverse target polarization. The asymmetry depends on the azimuthal angles of both the pion (phi) and the target spin axis (phi(S)) about the virtual-photon direction and relative to the lepton scattering plane. The extracted Fourier component sin((phi+phi(S))(pi)(UT) is a signal of the previously unmeasured quark transversity distribution, in conjunction with the Collins fragmentation function, also unknown. The component sin((phi-phi(S)(pi)(UT) arises from a correlation between the transverse polarization of the target nucleon and the intrinsic transverse momentum of quarks, as represented by the previously unmeasured Sivers distribution function. Evidence for both signals is observed, but the Sivers asymmetry may be affected by exclusive vector meson production.

Flavor decomposition of the sea-quark helicity distributions in the nucleon from semiinclusive deep inelastic scattering

Double-spin asymmetries of semiinclusive cross sections for the production of identified pions and kaons have been measured in deep inelastic scattering of polarized positrons on a polarized deuterium target. Five helicity distributions including those for three sea quark flavors were extracted from these data together with reanalyzed previous data for identified pions from a hydrogen target. These distributions are consistent with zero for all three sea flavors. A recently predicted flavor asymmetry in the polarization of the light quark sea appears to be disfavored by the data.

Evidence for quark-hadron duality in the proton spin asymmetry A1

Spin-dependent lepton-nucleon scattering data have been used to investigate the validity of the concept of quark-hadron duality for the spin asymmetry A1. Longitudinally polarized positrons were scattered off a longitudinally polarized hydrogen target for values of Q2 between 1.2 and 12 GeV2 and values of W2 between 1 and 4 GeV2. The average double-spin asymmetry in the nucleon resonance region is found to agree with that measured in deep-inelastic scattering at the same values of the Bjorken scaling variable x. This finding implies that the description of A1 in terms of quark degrees of freedom is valid also in the nucleon resonance region for values of Q2 above 1.6 GeV2.

Q2 dependence of nuclear transparency for exclusive rho0 production

Exclusive coherent and incoherent electroproduction of the rho(0) meson from 1H and 14N targets has been studied at the HERMES experiment as a function of coherence length (l(c)), corresponding to the lifetime of hadronic fluctuations of the virtual photon, and squared four-momentum of the virtual photon (-Q2). The ratio of 14N to 1H cross sections per nucleon, called nuclear transparency, was found to increase (decrease) with increasing l(c) for coherent (incoherent) rho(0) electroproduction. For fixed l(c), a rise of nuclear transparency with Q2 is observed for both coherent and incoherent rho(0) production, which is in agreement with theoretical calculations of color transparency.

Measurement of the high energy two-body deuteron photodisintegration differential cross section

The first measurements of the d(gamma,p)n differential cross section at forward angles and photon energies above 4 GeV were performed at the Thomas Jefferson National Accelerator Facility (JLab). The results indicate evidence of an angular dependent scaling threshold. Results at straight theta(cm) = 37 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 4 GeV, while those at 70 degrees are consistent with the constituent counting rules for E(gamma) greater, similar 1.5 GeV.

Evidence for a single-spin azimuthal asymmetry in semi-inclusive pion electroproduction

Single-spin asymmetries for semi-inclusive pion production in deep-inelastic scattering have been measured for the first time. A significant target-spin asymmetry of the distribution in the azimuthal angle straight phi of the pion relative to the lepton scattering plane was formed for pi(+) electroproduction on a longitudinally polarized hydrogen target. The corresponding analyzing power in the sinstraight phi moment of the cross section is 0.022+/-0.005+/-0.003. This result can be interpreted as the effect of terms in the cross section involving chiral-odd spin distribution functions in combination with a chiral-odd fragmentation function that is sensitive to the transverse polarization of the fragmenting quark.