The large-scale distribution of neutral hydrogen in the Universe will be luminous through its 21 cm emission. Here, for the first time, we use the auto-power spectrum of 21 cm intensity fluctuations to constrain neutral hydrogen fluctuations at z ∼ 0.8. Our data were acquired with the Green Bank Telescope and span the redshift range 0.6 < z < 1 over two fields totalling ≈ 41 deg 2 and 190 h of radio integration time. The dominant synchrotron foregrounds exceed the signal by ∼ 10 3 , but have fewer degrees of freedom and can be removed efficiently. Even in the presence of residual foregrounds, the auto-power can still be interpreted as an upper bound on the 21 cm signal. Our previous measurements of the cross-correlation of 21 cm intensity and the WiggleZ galaxy survey provide a lower bound. Through a Bayesian treatment of signal and foregrounds, we can combine both fields in auto-and cross-power into a measurement of Ω HI b HI = [0.62 +0.23 −0.15 ] × 10 −3 at 68% confidence with 9% systematic calibration uncertainty, where Ω HI is the neutral hydrogen (H I) fraction and b HI is the H I bias parameter. We describe observational challenges with the present data set and plans to overcome them.
We have calculated the magnetic moment of the recently observed Θ + pentaquark in the framework of the light cone QCD sum rules using the photon distribution amplitudes. We find that µ Θ + = (0.12 ± 0.06)µ N , which is quite small. We also compare our result with predictions of other groups.
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