Gravitational wave astronomy stays pitch-black (up to now)

No electromagnetic counterparts from optical wavelengths...

We present a search for an electromagnetic counterpart of the gravitational wave source GW151226. Using the Pan-STARRS1 telescope we mapped out 290 square degrees in the optical i_ps filter over a period starting 11.45hr after the LIGO information release (49.48hr after the GW trigger) and lasting for a further 28 days. We typically reached sensitivity limits of i_ps=20.3-20.8 and covered 26.5% of the LIGO probability skymap. We supplemented this with ATLAS survey data, reaching 31% of the probability region to shallower depths of m~19. We found 49 extragalactic transients (that are not obviously AGN), including a faint transient in a galaxy at 7Mpc (a luminous blue variable outburst) plus a rapidly decaying M-dwarf flare. Spectral classification of 20 other transient events showed them all to be supernovae. We found an unusual transient, PS15dpn, with an explosion date temporally coincident with GW151226 which evolved into a type Ibn supernova. The redshift of the transient is secure at z=0.1747 +/- 0.0001 and we find it unlikely to be linked, since the luminosity distance has a negligible probability of being consistent with that of GW151226. In the 290 square degrees surveyed we therefore do not find a likely counterpart. However we show that our survey strategy would be sensitive to Neutron Star-Nentron Star mergers producing kilonovae at D < 100 Mpc, which is promising for future LIGO/Virgo searches.

A search for an optical counterpart to the gravitational wave event GW151226

S. J. Smartt et al, (Submitted on 15 Jun 2016)

 ... to gamma ray ones

We present the Fermi Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) observations of the LIGO binary black hole merger event GW151226 and candi- date LVT151012. No candidate electromagnetic counterparts were detected by either the GBM or LAT. We present a detailed analysis of the GBM and LAT data over a range of timescales from seconds to years, using automated pipelines and new techniques for char- acterizing the upper limits across a large area of the sky. Due to the partial GBM and LAT coverage of the large LIGO localization regions at the trigger times for both events, differences in source distances and masses, as well as the uncertain degree to which emission from these sources could be beamed, these non-detections cannot be used to constrain the variety of theoretical models recently applied to explain the candidate GBM counterpart to GW150914.

Searching the Gamma-ray Sky for Counterparts to Gravitational Wave Sources: Fermi GBM and LAT Observations of LVT151012 and GW151226

J. L. Racusin et al, (Submitted on 15 Jun 2016)

GW151226 : Second direct detection (first replication) of a gravitational wave detection !

Live : https://iframe.dacast.com/b/59062/c/268750 !

The first available animation !

The Paper !

We report the observation of a gravitational-wave signal produced by the coalescence of two stellar-mass black holes. The signal, GW151226, was observed by the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) on December 26, 2015 at 03:38:53 UTC. The signal was initially identified within 70 s by an online matched-filter search targeting binary coalescences. Subsequent off-line analyses recovered GW151226 with a network signal-to-noise ratio of 13 and a significance greater than 5σ. The signal persisted in the LIGO frequency band for approximately 1 s, increasing in frequency and amplitude over about 55 cycles from 35 to 450 Hz, and reached a peak gravitational strain of 3.4±0.7±0.9×10^-22. The inferred source-frame initial black hole masses are 14.2±8.3±3.7M_⊙ and 7.5±2.3±2.3M_⊙, and the final black hole mass is 20.8±6.1±1.7M_⊙. We find that at least one of the component black holes has spin greater than 0.2. This source is located at a luminosity distance of 440±180±190 Mpc corresponding to a redshift of 0.09±0.03 ±0.04 . All uncertainties define a 90% credible interval. This second gravitational-wave observation provides improved constraints on stellar populations and on deviations from general relativity

GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence B. P. Abbott et al.* (LIGO Scientific Collaboration and Virgo Collaboration) (Received 31 May 2016; published 15 June 2016) 

Higgs times seven (minus one) / sept moins une fois le boson de Higgs

750 GeV = 6×125 GeV!

The first LHC data about pp collisions at √ s = 13 TeV agree with the Standard Model (SM), except for a hint of an excess in pp → γγ peaked at invariant mass around 750 GeV [1]. We denote the new resonance with the symbol {digamma}, used in archaic greek as the digamma letter and later as the number 6 ≈ Mz/Mh, but disappeared twice... unlike many other anomalies that disappeared, the γγ excess cannot be caused by a systematic issue, neither experimental nor theoretical. Theoretically, the SM background is dominated by tree-level qq̅→ γγ scatterings, which cannot make a γγ resonance [See {below} for a attempt of finding a Standard Model interpretation.] Experimentally, one just needs to identify two photons and measure their energy and direction. The γγ excess is either the biggest statistical fluctuation since decades, or the main discovery.

Interpreting the 750 GeV digamma excess: a review

Alessandro Strumia

(Submitted on 30 May 2016)

750 GeV scalar boson = (6 top quarks + 6 antitop quarks) bound state?

We shall here explore the possibility that the diphoton excess in the inclusive γγ spectrum, recently found by the ATLAS and CMS collaborations [1, 2], with a mass of 750 GeV can be a bound state of particles already present in the Standard Model, namely a bound state of 6 top + 6 antitop quarks. Thus we would need no new fundamental particles, interactions or free parameters beyond the Standard Model to explain this peak, which otherwise looks like “new physics”!  

For several years we have worked on the somewhat controversial idea [3, 4, 5, 6, 7, 8] that the exchange of Higgses and gluons between 6 top and 6 antitop quarks provides sufficiently strong attraction between these quarks for a very light (compared to the mass of 12 top quarks) bound state S to be formed. The 6 tops + 6 antitops are all supposed to be in the 1s state in the atomic physics notation and, because of there being just 3 colors and 2 spin states for a top-quark, this is the maximum number allowed in the 1s shell. 

Further speculations around this bound state were mostly built up under the assumption of a hoped for new principle – the multiple point principle [9, 10, 11] – from which we actually predicted the mass of the Higgs boson long before it was found [12]. This principle says that there shall be several phases of space (i.e. several vacua) with the same energy density. One of these should have a condensate of the bound states S. It was even speculated then that such a condensate – or new vacuum – could form the interior of balls, containing highly compressed ordinary matter, which make up the dark matter [13, 14, 15]. Thus the discovery, if confirmed, of the bound state S could support a theory, in which dark matter could be incorporated into a pure Standard Model theory, only adding the multiple point principle, which predicts the values of coupling constants but otherwise without new physics.

Production and Decay of 750 Gev state of 6 top and 6 anti top quarks

Colin D. Froggatt, Holger B. Nielsen

(Submitted on 12 May 2016)