Increasing the Astrophysical Reach of the Advanced Virgo Detector via the Application of Squeezed Vacuum States of Light

Current interferometric gravitational-wave detectors are limited by quantum noise over a wide range of their measurement bandwidth. One method to overcome the quantum limit is the injection of squeezed vacuum states of light into the interferometer’s dark port. Here, we report on the successful application of this quantum technology to improve the shot noise limited sensitivity of the Advanced Virgo gravitational-wave detector. A sensitivity enhancement of up to 3.2±0.1  dB beyond the shot noise limit is achieved. This nonclassical improvement corresponds to a 5%–8% increase of the binary neutron star horizon. The squeezing injection was fully automated and over the first 5 months of the third joint LIGO-Virgo observation run O3 squeezing was applied for more than 99% of the science time. During this period several gravitational-wave candidates have been recorded

Direct photon elliptic flow in Pb-Pb collisions at root s(NN)=2.76 TeV

The elliptic flow of inclusive and direct photons was measured at mid-rapidity in two centrality classes 0-20% and 20-40% in Pb-Pb collisions at root s(NN) = 2.76 TeV by ALICE. Photons were detected with the highly segmented electromagnetic calorimeter PHOS and via conversions in the detector material with the e(broken vertical bar)e pairs reconstructed in the central tracking system. The results of the two methods were combined and the direct-photon elliptic flow was extracted in the transverse momentum range 0.9 < p(T) < 6.2 GeV/c. A comparison to RHIC data shows a similar magnitude of the measured direct-photon elliptic flow. Hydrodynamic and transport model calculations are systematically lower than the data, but are found to be compatible. (C) 2018 The Author. Published by Elsevier B.V.Peer reviewe

Higher moment fluctuations of identified particle distributions from ALICE

Cumulants of conserved charges fluctuations are regarded as a potential tool to study the criticality in the QCD phase diagram and to determine the freeze-out parameters in a model-independent way. At LHC energies, the measurements of the ratio of the net-baryon (net-proton) cumulants can be used to test the lattice QCD predictions. In this work, we present the first measurements of cumulants of the net-proton number distributions up to $4^{th}$ order in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 and 5.02 TeV as a function of collision centrality. We compare our cumulant ratios results with the STAR experiment net-proton results measured in the first phase of the Beam Energy Scan program at RHIC. The results can be used to obtain the chemical freeze-out parameters at LHC.Comment: 4 pages, 3 figures, Proceedings of XXVIIth International Conference on Ultrarelativistic Nucleus-Nucleus Collisions (Quark Matter 2018

Spin alignment measurements using vector mesons with ALICE detector at the LHC

We present new measurements related to spin alignment of K*(0) vector mesons at mid-rapidity for Pb-Pb collisions at root s(NN) = 2.76 and 5.02 TeV. The spin alignment measurements are carried out with respect to production plane and 2nd order event plane. At low p(T) the spin density matrix element rho(00) for K*(0) is found to have values slightly below 1/3, while it is consistent with 1/3, i.e. no spin alignment, at high p(T). Similar values of rho(00) are observed with respect to both production plane and event plane. Within statistical and systematic uncertainties, rho(00) values are also found to be independent of root s(NN). rho(00) also shows centrality dependence with maximum deviation from 1/3 for mid-central collisions with respect to both the kinematic planes. The measurements for K*(0) in pp collisions at root s = 13 TeV and for K-s(0) (a spin 0 hadron) in 20-40\% central Pb-Pb collisions at root s(NN) = 2.76 TeV are consistent with no spin alignment

Muon physics at forward rapidity with the ALICE detector upgrade

ALICE is the experiment specifically designed to study the Quark-Gluon Plasma (QGP) in heavy-ion collisions at the CERN LHC. The ALICE detector will be upgraded during the Long Shutdown 2, planned for 2019-2020, in order to cope with the maximum interaction rate of 50 kHz of Pb-Pb collisions foreseen for Runs 3 and 4. The ambitious programme of high-precision measurements, expected for muon physics after 2020, requires an upgrade of the front-end and readout electronics of the existing Muon Spectrometer. This concerns the Cathode Pad Chambers (CPC) used for tracking and the Resistive Plate Chambers (RPC) used for triggering and for muon identification. The Muon Forward Tracker (MFT), an internal tracker added in front of the front absorber of the existing Muon Spectrometer, is also part of the ALICE detector upgrade programme. It is based on an assembly of circular planes made of Monolithic Active Pixel Sensors (MAPS), covering the pseudorapidity range 2.5 < eta < 3.6. The MFT will improve present measurements and enable new ones. A selection of results from physics performance studies will be presented, together with an overview of the technical aspects of the upgrade project

Measuring (KSK +/-)-K-0 interactions using pp collisions at root s=7 TeV

We present the first measurements of femtoscopic correlations between the K-S(0) and K-+/- particles in pp collisions at root s = 7 TeV measured by the ALICE experiment. The observed femtoscopic correlations are consistent with final-state interactions proceeding solely via the a(0)(980) resonance. The extracted kaon source radius and correlation strength parameters for (KSK-)-K-0 are found to be equal within the experimental uncertainties to those for (KSK+)-K-0. Results of the present study are compared with those from identical-kaon femtoscopic studies also performed with pp collisions at root s = 7 TeV by ALICE and with a (KSK +/-)-K-0 measurement in Pb-Pb collisions at root s(NN) = 2.76 TeV. Combined with the Pb-Pb results, our pp analysis is found to be compatible with the interpretation of the a (980) having a tetraquark structure instead of that of a diquark. (C) 2018 Published by Elsevier B.V.Peer reviewe

Light (anti-)nuclei production and elliptic flow at the LHC with ALICE

Results on the production of stable light nuclei, including deuterons, He-3, He-4 and the corresponding anti-nuclei, in Pb-Pb collisions at root s(NN) = 2.76 TeV and root s(NN) = 5.02 TeV are presented and compared with theoretical predictions and with the results in small systems to provide insight into the production mechanisms of (anti-)nuclei at colliders. The experimental results are presented giving a critical view of their comparison to the expectations from coalescence and hydrodynamic models that aim at describing both the p(T)-spectra and the elliptic flow

Open heavy-flavour production and elliptic flow in p-Pb collisions at the LHC with ALICE

Measurements of open heavy flavour production in p-A collisions allow the investigation of Cold Nuclear Matter effects. In addition, they are an important tool for a complementary investigation of the long-range correlations found in small systems in the light flavour sector. In this work, production measurements of D mesons at mid-rapidity in p-Pb collisions at root S-NN = 5.02 TeV are reported. Production yields are also reported for the heavy-flavour hadron decay electrons at central rapidity at root(SNN) = 5.02 and 8.16 TeV. The elliptic flow (nu(2)) of heavy-flavour hadron decay electrons in high multiplicity p-Pb collisions at root(SNN) = 5.02 TeV is found to be positive with a significance larger than 5 sigma

Search for eccentric binary black hole mergers with Advanced LIGO and Advanced Virgo during their first and second observing runs

When formed through dynamical interactions, stellar-mass binary black holes (BBHs) may retain eccentric orbits (e > 0.1 at 10 Hz) detectable by ground-based gravitational-wave detectors. Eccentricity can therefore be used to differentiate dynamically formed binaries from isolated BBH mergers. Current template-based gravitational-wave searches do not use waveform models associated with eccentric orbits, rendering the search less efficient for eccentric binary systems. Here we present the results of a search for BBH mergers that inspiral in eccentric orbits using data from the first and second observing runs (O1 and O2) of Advanced LIGO and Advanced Virgo. We carried out the search with the coherent WaveBurst algorithm, which uses minimal assumptions on the signal morphology and does not rely on binary waveform templates. We show that it is sensitive to binary mergers with a detection range that is weakly dependent on eccentricity for all bound systems. Our search did not identify any new binary merger candidates. We interpret these results in light of eccentric binary formation models. We rule out formation channels with rates greater than about 100 Gpc−3 yr−1 for e > 0.1, assuming a black hole mass spectrum with a power-law index less than about 2

A joint fermi-gbm and ligo/virgo analysis of compact binary mergers from the first and second gravitational-wave observing runs

We present results from offline searches of Fermi Gamma-ray Burst Monitor (GBM) data for gamma-ray transients coincident with the compact binary coalescences observed by the gravitational-wave (GW) detectors Advanced LIGO and Advanced Virgo during their first and second observing runs. In particular, we perform follow-up for both confirmed events and low significance candidates reported in the LIGO/Virgo catalog GWTC-1. We search for temporal coincidences between these GW signals and GBM-triggered gamma-ray bursts (GRBs). We also use the GBM Untargeted and Targeted subthreshold searches to find coincident gamma-rays below the onboard triggering threshold. This work implements a refined statistical approach by incorporating GW astrophysical source probabilities and GBM visibilities of LIGO/Virgo sky localizations to search for cumulative signatures of coincident subthreshold gamma-rays. All search methods recover the short gamma-ray burst GRB 170817A occurring ∼1.7 s after the binary neutron-star merger GW170817. We also present results from a new search seeking GBM counterparts to LIGO single-interferometer triggers. This search finds a candidate joint event, but given the nature of the GBM signal and localization, as well as the high joint false alarm rate of 1.1 10-6 Hz, we do not consider it an astrophysical association. We find no additional coincidences