Testing general relativity using higher-order modes of gravitational waves from binary black holes

Recently, strong evidence was found for the presence of higher-order modes in the gravitational wave signals GW190412 and GW190814, which originated from compact binary coalescences with significantly asymmetric component masses. This has opened up the possibility of new tests of general relativity by looking at the way in which the higher-order modes are related to the basic signal. Here we further develop a test which assesses whether the amplitudes of subdominant harmonics are consistent with what is predicted by general relativity. To this end we incorporate a state-of-the-art waveform model with higher-order modes and precessing spins into a Bayesian parameter estimation and model selection framework. The analysis methodology is tested extensively through simulations. We investigate to what extent deviations in the relative amplitudes of the harmonics will be measurable depending on the properties of the source, and we map out correlations between our testing parameters and the inclination of the source with respect to the observer. Finally, we apply the test to GW190412 and GW190814, finding no evidence for violations of general relativity

The GstLAL template bank for spinning compact binary mergers in the second observation run of Advanced LIGO and Virgo

We describe the methods used to construct the aligned-spin template bank of gravitational waveforms used by the GstLAL-based inspiral pipeline to analyze data from the second observing run of Advanced LIGO and Virgo. The bank expands upon the parameter space covered during the first observing run, including coverage for merging compact binary systems with total mass between 2 $\mathrm{M}_{\odot}$ and 400 $\mathrm{M}_{\odot}$ and mass ratios between 1 and 97.989. Thus the systems targeted include merging neutron star-neutron star systems, neutron star-black hole binaries, and black hole-black hole binaries expanding into the intermediate-mass range. Component masses less than 2 $\mathrm{M}_{\odot}$ have allowed (anti-)aligned spins between $\pm0.05$ while component masses greater than 2 $\mathrm{M}_{\odot}$ have allowed (anti-)aligned between $\pm0.999$. The bank placement technique combines a stochastic method with a new grid-bank method to better isolate noisy templates, resulting in a total of 677,000 templates.Comment: 9 pages, 13 figure

Performance of the Electromagnetic Pixel Calorimeter Prototype EPICAL-2

The first evaluation of an ultra-high granularity digital electromagnetic calorimeter prototype using 1.0-5.8 GeV/c electrons is presented. The $25\times10^6$ pixel detector consists of 24 layers of ALPIDE CMOS MAPS sensors, with a pitch of around 30~$\mu$m, and has a depth of almost 20 radiation lengths of tungsten absorber. Ultra-thin cables allow for a very compact design. The properties that are critical for physics studies are measured: electromagnetic shower response, energy resolution and linearity. The stochastic energy resolution is comparable with the state-of-the art resolution for a Si-W calorimeter, with data described well by a simulation model using GEANT and Allpix$^2$. The performance achieved makes this technology a good candidate for use in the ALICE FoCal upgrade, and in general demonstrates the strong potential for future applications in high-energy physics.Comment: 30 pages, 19 figures, submitted to JINS

Results from the EPICAL-2 ultra-high granularity electromagnetic calorimeter prototype

A prototype of a new type of calorimeter has been designed and constructed, based on a silicon–tungsten sampling design using pixel sensors with digital readout. It makes use of the ALPIDE sensor developed for the ALICE Inner Tracking System (ITS) upgrade. A binary readout is possible due to the pixel size of ≈ 30 × 30 μ m 2 . This prototype has been successfully tested with cosmic muons and with test beams at DESY and the CERN SPS. We report on performance results obtained at DESY, showing good energy resolution and linearity, and compare to detailed MC simulations. Also shown are preliminary results of the high-energy performance as measured at the SPS. The two-shower separation capabilities are discussed

Inclusive quarkonium production in pp collisions at √s = 5.02 TeV

This article reports on the inclusive production cross section of several quarkonium states, J / ψ, ψ(2 S) , Υ (1 S) , Υ (2 S) , and Υ (3 S) , measured with the ALICE detector at the LHC, in pp collisions at s=5.02 TeV. The analysis is performed in the dimuon decay channel at forward rapidity (2.5 < y< 4). The integrated cross sections and transverse-momentum (pT) and rapidity (y) differential cross sections for J / ψ, ψ(2 S) , Υ (1 S) , and the ψ(2 S) -to-J / ψ cross section ratios are presented. The integrated cross sections, assuming unpolarized quarkonia, are: σJ / ψ (pT< 20 GeV/c) = 5.88 ± 0.03 ± 0.34μb, σψ ( 2 S ) (pT< 12 GeV/c) = 0.87 ± 0.06 ± 0.10μb, σΥ ( 1 S ) (pT< 15 GeV/c) = 45.5 ± 3.9 ± 3.5 nb, σΥ (2 S) (pT< 15 GeV/c) = 22.4 ± 3.2 ± 2.7 nb, and σΥ (3 S) (pT< 15 GeV/c) = 4.9 ± 2.2 ± 1.0 nb, where the first (second) uncertainty is the statistical (systematic) one. For the first time, the cross sections of the three Υ states, as well as the ψ(2 S) one as a function of pTand y, are measured at s=5.02 TeV at forward rapidity. These measurements also significantly extend the J / ψpTreach and supersede previously published results. A comparison with ALICE measurements in pp collisions at s=2.76, 7, 8, and 13 TeV is presented and the energy dependence of quarkonium production cross sections is discussed. Finally, the results are compared with the predictions from several production models

Publisher Correction: Direct observation of the dead-cone effect in quantum chromodynamics (Nature, (2022), 605, 7910, (440-446), 10.1038/s41586-022-04572-w)

In the version of this article initially published, there was a typographical error in the first sentence following the “Exposing the dead cone” heading, now reading, “The measurements of R(θ), in the three radiator (charmquark) energy intervals 5 < ERadiator < 10 GeV, 10 < ERadiator < 20 GeV and 20 < ERadiator < 35 GeV…,” where “35 GeV” initially appeared as “3 GeV.” The error has been corrected in the HTML and PDF versions of the article. *A list of authors and their affiliations appears online

Nonorthogonal wavelet transformation for reconstructing gravitational wave signals

Detections of gravitational-wave signals from compact binary coalescences have enabled us to study extreme astrophysical phenomena and explore fundamental physics. A crucial requisite for these studies is to have accurate signal models with characteristic morphologies, which have been challenging for many decades, and researchers are still endeavoring to incorporate important physics. Therefore, morphology-independent methods have been developed for identifying a signal and its reconstruction. The reconstructed signal allows us to test the agreement between the observed signal and the waveform posterior samples from parameter estimation. These methods model observed signals using a nearly orthogonal wavelet basis in the frame of continuous wavelet transformation. Here, we propose log-uniform scales to construct the wavelets, which are are highly redundant (nonorthogonal) compared to the conventional octave scales but more efficient for reconstructing the signals at high frequencies. And we introduce a semi-model-dependent reconstruction method using the posterior samples of the events, where we model the signal using Gabor-Morlet wavelets with log-uniform scales. We demonstrate the ability to detect deviation using a numerical simulation of an eccentric binary black hole merger, where the signal in the data does not belong to the search template waveform manifold. Finally, we apply this method to each binary black hole merger event in GWTC-1. We have found that the signal produced by the GW150914 event has 96% agreement with the waveform posterior samples. As the detector sensitivity improves and the detected population of black hole mergers grows, we expect the proposed method will provide even stronger tests

Erratum: Azimuthal Anisotropy of KS0 and Λ+Λ¯ Production at Midrapidity from Au+Au Collisions at √sNN=130 GeV [Phys. Rev. Lett. 89, 132301 (2002)]

In this erratum we report on a correction to the measurement of azimuthal anisotropy v2 as a function of transverse momentum pt for KS0 at midrapidity in Au+Au collisions at (Farmula Presented). In Fig. 3 of this Letter, v2 for K0S at pt=1.4 GeV/c was mistakenly plotted with a factor 10 smaller statistical error than was actually determined (v2=0.0996±0.0010). Figure 3 in this erratum shows v2 for K0S at pt=1.4 GeV/c with the correct statistical error (v2=0.0996±0.010). The statistical uncertainties of the other data points in the figure are not affected by this mistake. The essential physics implication of the figure is unchanged after the correction. The physics discussions and conclusions of the Letter remain the same

Model-based Cross-correlation Search for Gravitational Waves from the Low-mass X-Ray Binary Scorpius X-1 in LIGO O3 Data

We present the results of a model-based search for continuous gravitational waves from the low-mass X-ray binary Scorpius X-1 using LIGO detector data from the third observing run of Advanced LIGO and Advanced Virgo. This is a semicoherent search that uses details of the signal model to coherently combine data separated by less than a specified coherence time, which can be adjusted to balance sensitivity with computing cost. The search covered a range of gravitational-wave frequencies from 25 to 1600 Hz, as well as ranges in orbital speed, frequency, and phase determined from observational constraints. No significant detection candidates were found, and upper limits were set as a function of frequency. The most stringent limits, between 100 and 200 Hz, correspond to an amplitude h0 of about 10−25 when marginalized isotropically over the unknown inclination angle of the neutron star's rotation axis, or less than 4 × 10−26 assuming the optimal orientation. The sensitivity of this search is now probing amplitudes predicted by models of torque balance equilibrium. For the usual conservative model assuming accretion at the surface of the neutron star, our isotropically marginalized upper limits are close to the predicted amplitude from about 70 to 100 Hz; the limits assuming that the neutron star spin is aligned with the most likely orbital angular momentum are below the conservative torque balance predictions from 40 to 200 Hz. Assuming a broader range of accretion models, our direct limits on gravitational-wave amplitude delve into the relevant parameter space over a wide range of frequencies, to 500 Hz or more