13881872
A history of the gamma-ray burst flux at the Earth from Galactic globular clusters
Nearby gamma-ray bursts (GRBs) are likely to have represented a significant threat to life on the Earth. Recent observations suggest that a significant source of such bursts is compact binary mergers in globular clusters. This link between globular clusters and GRBs o ers the possibility to find time intervals in the past with higher probabilities of a nearby burst, by tracing globular cluster orbits back in time. Here we show that the expected flux from such bursts is not flat over the past 550 Myr but rather exhibits three broad peaks, at 70, 180 and 340 Myr ago. The main source for nearby GRBs for all three time intervals is the globular cluster 47 Tuc, a consequence of its large mass and high stellar encounter rate, as well as the fact that it is one of the globular clusters which comes quite close to the Sun. Mass extinction events indeed coincide with all three time intervals found in this study, although a chance coincidence is quite likely. Nevertheless, the identified time intervals can be used as a guide to search for specific signatures of GRBs in the geological record around these times.
119298416
Radio jets and galaxies as cosmic string probes
The lensing effect of a cosmic string is studied, and some new methods are proposed to detect the cosmic string. The technique for using jets as extended gravitational lensing probes was first explored by Kronberg. We use the “alignment-breaking parameter” ηG as a sensitive indicator of gravitational distortion by a wiggly cosmic string. Then, we applied the non-constant deflection angle to jets, and ηG of a specific jet is just related to the projected slope of the jet. At least three jets in the sample of Square Kilometer Array (SKA) would have significant signals (ηG > 10°) if the wiggly infinite cosmic string existed. The distortion of elliptical object is also studied and used to do a statistical research on the directions of axes and ellipticities of galaxies. In the direction of the string, we find that galaxies appear to be more elliptical for an observer and the distribution of apparent ellipticity changes correspondingly. The ellipticity distribution of current SDSS spiral sample has the signal-to-noise ratio up to 8.48 which is large enough for astronomical observations. The future survey, such as Large Synoptic Survey Telescope (LSST) and Dark Energy Survey (DES) would weaken the requirement of special geometry in the data processing. As a result, all kinds of distributions, including ellipticity axis distribution, would serve as probes to detect wiggly strings in the near future. In brief, if a wiggly cosmic string existed, these signals would be convenient to be observed with the future weak lensing survey or other surveys in the deep space. If there was no lensing signal in these distributions, it would give the upper limit of the abundance of infinite strings.
15590324
Evidence for periodicities in the extinction record? Response to Melott & Bambach [arXiv:1307.1884]
In a recent paper, we applied time series analysis methods to study the possible influence of the solar motion through the Galaxy on terrestrial extinction (Feng & Bailer-Jones 2013). We drew conclusions about the relative probabilities of how well different models explain the geological extinction record. We found no strong evidence for either a periodicity in the extinction record or for a link between the solar orbit and this extinction record. In response to this, Melott & Bambach (2013) dedicate the majority of their article to criticizing our analysis. Their main objection is to evidence-based model comparison. Here we deal with their criticisms one by one, and show that they are largely misplaced, leaving our conclusions unaffected. The bottom line is that although one can get a periodic model at some period to fit the extinction data, there are other models which explain the data better.
118918841
Short-range force between two Higgs bosons
The S-wave scattering length and the effective range of the Higgs boson in Standard Model are studied using effective-field-theory approach. After incorporating the first-order electroweak correction, the short-range force between two Higgs bosons remains weakly attractive for M-H = 126 GeV. It is interesting to find that the force range is about two order-of-magnitude larger than the Compton wavelength of the Higgs boson, almost comparable with the typical length scale of the strong interaction. (C) 2014 The Authors. Published by Elsevier B.V.
121501552
Exclusive decay of Υ into J/ψ+$χ_{c0,1,2}$
117848095
${\mathcal O}(\alpha_s)$ corrections to $e^+e^-\rightarrow J/\psi+\eta_{c2}(\chi_{c1}^\prime)$ at $B$ factories
We investigate the O(alpha(s)) correction to e(+)e(-) -> J/psi + eta(c2) in the NRQCD factorization approach. A detailed comparative study between e(+)e(-) -> J/psi + eta(c2), and e(+)e(-) -> J/psi + chi(c1)', at the B factory energy is also carried out. After incorporating the O(alpha(s)) correction, we predict the cross section for the former process to be around 0.3 fb, while that of the latter is about 6 times greater. The outgoing J/psi is found to be dominantly transversely polarized in the former process, while longitudinally polarized in the latter. These features may provide valuable guidance for the Belle 2 experiment to establish the chi(c1)', or eta(c2) states. In the Appendix, we also identify the coefficients of the double logarithms of form 1n(2)(s/m(c)(2)) associated with all the relevant next -to -leading -order Feynman diagrams, for the helicity-suppressed double-charmonium production channels e(+)e(-) -> J/psi + eta(c2) and e(+)e(-) -> J/psi + chi(c0,1,2).