Showing papers by "Timothy Evans published in 2021"

Observation of Gravitational Waves from Two Neutron Star–Black Hole Coalescences

Abstract: We report the observation of gravitational waves from two compact binary coalescences in LIGO’s and Virgo’s third observing run with properties consistent with neutron star–black hole (NSBH) binaries. The two events are named GW200105_162426 and GW200115_042309, abbreviated as GW200105 and GW200115; the first was observed by LIGO Livingston and Virgo and the second by all three LIGO–Virgo detectors. The source of GW200105 has component masses 8.9−1.5+1.2 and 1.9−0.2+0.3M⊙ , whereas the source of GW200115 has component masses 5.7−2.1+1.8 and 1.5−0.3+0.7M⊙ (all measurements quoted at the 90% credible level). The probability that the secondary’s mass is below the maximal mass of a neutron star is 89%–96% and 87%–98%, respectively, for GW200105 and GW200115, with the ranges arising from different astrophysical assumptions. The source luminosity distances are 280−110+110 and 300−100+150Mpc , respectively. The magnitude of the primary spin of GW200105 is less than 0.23 at the 90% credible level, and its orientation is unconstrained. For GW200115, the primary spin has a negative spin projection onto the orbital angular momentum at 88% probability. We are unable to constrain the spin or tidal deformation of the secondary component for either event. We infer an NSBH merger rate density of 45−33+75Gpc−3yr−1 when assuming that GW200105 and GW200115 are representative of the NSBH population or 130−69+112Gpc−3yr−1 under the assumption of a broader distribution of component masses.

A gravitational-wave measurement of the Hubble constant following the second observing run of Advanced LIGO and Virgo

Abstract: This paper presents the gravitational-wave measurement of the Hubble constant (H 0) using the detections from the first and second observing runs of the Advanced LIGO and Virgo detector network. The presence of the transient electromagnetic counterpart of the binary neutron star GW170817 led to the first standard-siren measurement of H 0. Here we additionally use binary black hole detections in conjunction with galaxy catalogs and report a joint measurement. Our updated measurement is H 0 = km s−1 Mpc−1 (68.3% of the highest density posterior interval with a flat-in-log prior) which is an improvement by a factor of 1.04 (about 4%) over the GW170817-only value of km s−1 Mpc−1. A significant additional contribution currently comes from GW170814, a loud and well-localized detection from a part of the sky thoroughly covered by the Dark Energy Survey. With numerous detections anticipated over the upcoming years, an exhaustive understanding of other systematic effects are also going to become increasingly important. These results establish the path to cosmology using gravitational-wave observations with and without transient electromagnetic counterparts.

Upper limits on the isotropic gravitational-wave background from Advanced LIGO and Advanced Virgo’s third observing run

Abstract: We report results of a search for an isotropic gravitational-wave background (GWB) using data from Advanced LIGO’s and Advanced Virgo’s third observing run (O3) combined with upper limits from the earlier O1 and O2 runs. Unlike in previous observing runs in the advanced detector era, we include Virgo in the search for the GWB. The results of the search are consistent with uncorrelated noise, and therefore we place upper limits on the strength of the GWB. We find that the dimensionless energy density Ω GW ≤ 5.8 × 10 − 9 at the 95% credible level for a flat (frequency-independent) GWB, using a prior which is uniform in the log of the strength of the GWB, with 99% of the sensitivity coming from the band 20–76.6 Hz; Ω GW ( f ) ≤ 3.4 × 10 − 9 at 25 Hz for a power-law GWB with a spectral index of 2 / 3 (consistent with expectations for compact binary coalescences), in the band 20–90.6 Hz; and Ω GW ( f ) ≤ 3.9 × 10 − 10 at 25 Hz for a spectral index of 3, in the band 20–291.6 Hz. These upper limits improve over our previous results by a factor of 6.0 for a flat GWB, 8.8 for a spectral index of 2 / 3 , and 13.1 for a spectral index of 3. We also search for a GWB arising from scalar and vector modes, which are predicted by alternative theories of gravity; we do not find evidence of these, and place upper limits on the strength of GWBs with these polarizations. We demonstrate that there is no evidence of correlated noise of magnetic origin by performing a Bayesian analysis that allows for the presence of both a GWB and an effective magnetic background arising from geophysical Schumann resonances. We compare our upper limits to a fiducial model for the GWB from the merger of compact binaries, updating the model to use the most recent data-driven population inference from the systems detected during O3a. Finally, we combine our results with observations of individual mergers and show that, at design sensitivity, this joint approach may yield stronger constraints on the merger rate of binary black holes at z ≳ 2 than can be achieved with individually resolved mergers alone.

Evidence of a J/psi Lambda structure and observation of excited Xi(-) states in the Xi(-)(b) -> J/psi Lambda K- decay

Abstract: First evidence of a structure in the $J/\psi{\Lambda}$ invariant mass distribution is obtained from an amplitude analysis of$\Xi_b^-{\rightarrow}J/\psi{\Lambda}K^-$ decays. The observed structure is consistent with being due to a charmonium pentaquark with strangeness with a significance of $3.1\sigma$ including systematic uncertainties and look-elsewhere effect. Its mass and width are determined to be $4458.8\pm2.9^{+4.7}_{-1.1}$ MeV and $17.3\pm6.5^{+8.0}_{-5.7}$ MeV, respectively, where the quoted uncertainties are statistical and systematic. The structure is also consistent with being due to two resonances. In addition, the narrow excited $\Xi^-$ states, $\Xi(1690)^-$ and $\Xi(1820)^-$, are seen for the first time in a $\Xi^-_b$ decay, and their masses and widths are measured with improved precision. The analysis is performed using $pp$ collision data corresponding to a total integrated luminosity of 9 fb$^{-1}$, collected with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV.

LIGO Detector Characterization in the Second and Third Observing Runs

Abstract: The characterization of the Advanced LIGO detectors in the second and third observing runs has increased the sensitivity of the instruments, allowing for a higher number of detectable gravitational-wave signals, and provided confirmation of all observed gravitational-wave events. In this work, we present the methods used to characterize the LIGO detectors and curate the publicly available datasets, including the LIGO strain data and data quality products. We describe the essential role of these datasets in LIGO–Virgo Collaboration analyses of gravitational-waves from both transient and persistent sources and include details on the provenance of these datasets in order to support analyses of LIGO data by the broader community. Finally, we explain anticipated changes in the role of detector characterization and current efforts to prepare for the high rate of gravitational-wave alerts and events in future observing runs.

Test of lepton universality in beauty-quark decays

Abstract: The Standard Model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Previous measurements have shown a wide range of particle decays are consistent with this principle of lepton universality. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton-proton collision data collected with the LHCb detector at CERN's Large Hadron Collider. The measurements are of processes in which a beauty meson transforms into a strange meson with the emission of either an electron and a positron, or a muon and an antimuon. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the Standard Model, such as a new fundamental interaction between quarks and leptons.

Observation of new resonances decaying to $J/\psi K^+$ and $J/\psi \phi$

Abstract: The first observation of exotic states with a new quark content c c ¯ u s ¯ decaying to the J / ψ K + final state is reported with high significance from an amplitude analysis of the B + → J / ψ ϕ K + decay. The analysis is carried out using proton-proton collision data corresponding to a total integrated luminosity of 9 fb - 1 collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV. The most significant state, Z c s ( 4000 ) + , has a mass of 4003 ± 6 - 14 + 4 MeV , a width of 131 ± 15 ± 26 MeV , and spin parity J P = 1 + , where the quoted uncertainties are statistical and systematic, respectively. A new 1 + X ( 4685 ) state decaying to the J / ψ ϕ final state is also observed with high significance. In addition, the four previously reported J / ψ ϕ states are confirmed and two more exotic states, Z c s ( 4220 ) + and X ( 4630 ) , are observed with significance exceeding 5 standard deviations.

Constraints on Cosmic Strings Using Data from the Third Advanced LIGO–Virgo Observing Run

Abstract: We search for gravitational-wave signals produced by cosmic strings in the Advanced LIGO and Virgo full O3 dataset Search results are presented for gravitational waves produced by cosmic string loop features such as cusps, kinks, and, for the first time, kink-kink collisions A template-based search for short-duration transient signals does not yield a detection We also use the stochastic gravitational-wave background energy density upper limits derived from the O3 data to constrain the cosmic string tension Gμ as a function of the number of kinks, or the number of cusps, for two cosmic string loop distribution models Additionally, we develop and test a third model that interpolates between these two models Our results improve upon the previous LIGO-Virgo constraints on Gμ by 1 to 2 orders of magnitude depending on the model that is tested In particular, for the one-loop distribution model, we set the most competitive constraints to date: Gμ≲4×10^{-15} In the case of cosmic strings formed at the end of inflation in the context of grand unified theories, these results challenge simple inflationary models

All-sky search in early O3 LIGO data for continuous gravitational-wave signals from unknown neutron stars in binary systems

Abstract: Rapidly spinning neutron stars are promising sources of continuous gravitational waves. Detecting such a signal would allow probing of the physical properties of matter under extreme conditions. A significant fraction of the known pulsar population belongs to binary systems. Searching for unknown neutron stars in binary systems requires specialized algorithms to address unknown orbital frequency modulations. We present a search for continuous gravitational waves emitted by neutron stars in binary systems in early data from the third observing run of the Advanced LIGO and Advanced Virgo detectors using the semicoherent, GPU-accelerated, binaryskyhough pipeline. The search analyzes the most sensitive frequency band of the LIGO detectors, 50–300 Hz. Binary orbital parameters are split into four regions, comprising orbital periods of three to 45 days and projected semimajor axes of two to 40 light seconds. No detections are reported. We estimate the sensitivity of the search using simulated continuous wave signals, achieving the most sensitive results to date across the analyzed parameter space.

Search for anisotropic gravitational-wave backgrounds using data from Advanced LIGO and Advanced Virgo's first three observing runs

Abstract: We report results from searches for anisotropic stochastic gravitational-wave backgrounds using data from the first three observing runs of the Advanced LIGO and Advanced Virgo detectors. For the first time, we include Virgo data in our analysis and run our search with a new efficient pipeline called pystoch on data folded over one sidereal day. We use gravitational-wave radiometry (broadband and narrow band) to produce sky maps of stochastic gravitational-wave backgrounds and to search for gravitational waves from point sources. A spherical harmonic decomposition method is employed to look for gravitational-wave emission from spatially-extended sources. Neither technique found evidence of gravitational-wave signals. Hence we derive 95% confidence-level upper limit sky maps on the gravitational-wave energy flux from broadband point sources, ranging from F α , Θ < ( 0.013 – 7.6 ) × 10 − 8 erg cm − 2 s − 1 Hz − 1 , and on the (normalized) gravitational-wave energy density spectrum from extended sources, ranging from Ω α , Θ < ( 0.57 – 9.3 ) × 10 − 9 sr − 1 , depending on direction ( Θ ) and spectral index ( α ). These limits improve upon previous limits by factors of 2.9–3.5. We also set 95% confidence level upper limits on the frequency-dependent strain amplitudes of quasimonochromatic gravitational waves coming from three interesting targets, Scorpius X-1, SN 1987A and the Galactic Center, with best upper limits range from h 0 < ( 1.7 – 2.1 ) × 10 − 25 , a factor of ≥ 2.0 improvement compared to previous stochastic radiometer searches.

Observation of the decay $\Lambda_b^0\rightarrow\chi_{c1}p\pi^-$

Abstract: The Cabibbo-suppressed decay $ {\Lambda}_{\mathrm{b}}^0 $→ χ$_{c1}$pπ$^{−}$ is observed for the first time using data from proton-proton collisions corresponding to an integrated luminosity of 6 fb$^{−1}$, collected with the LHCb detector at a centre-of-mass energy of 13 TeV. Evidence for the $ {\Lambda}_{\mathrm{b}}^0 $→ χ$_{c2}$pπ$^{−}$ decay is also found. Using the $ {\Lambda}_{\mathrm{b}}^0 $→ χ$_{c1}$pK$^{−}$ decay as normalisation channel, the ratios of branching fractions are measured to be$ {\displaystyle \begin{array}{c}\frac{\mathcal{B}\left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1}{\mathrm{p}\uppi}^{-}\right)}{\mathcal{B}\left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1}{\mathrm{p}\mathrm{K}}^{-}\right)}=\left(6.59\pm 1.01\pm 0.22\right)\times {10}^{-2},\\ {}\frac{\mathcal{B}\left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}2}{\mathrm{p}\uppi}^{-}\right)}{\mathcal{B}\left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1}{\mathrm{p}\uppi}^{-}\right)}=0.95\pm 0.30\pm 0.04\pm 0.04,\\ {}\frac{\mathcal{B}\left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}2}{\mathrm{p}\mathrm{K}}^{-}\right)}{\mathcal{B}\left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1}{\mathrm{p}\mathrm{K}}^{-}\right)}=1.06\pm 0.05\pm 0.04\pm 0.04,\end{array}} $where the first uncertainty is statistical, the second is systematic and the third is due to the uncertainties in the branching fractions of χ$_{c1,2}$→ J/ψγ decays.[graphic not available: see fulltext]

Angular analysis of the rare decay B s 0 $$ {B}_s^0 $$ → ϕμ + μ −

Abstract: An angular analysis of the rare decay $$ {B}_s^0 $$ → ϕμ+μ− is presented, using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 8.4 fb−1. The observables describing the angular distributions of the decay $$ {B}_s^0 $$ → ϕμ+μ− are determined in regions of q2, the square of the dimuon invariant mass. The results are consistent with Standard Model predictions.

Reducing scattered light in LIGO's third observing run

Abstract: Noise due to scattered light has been a frequent disturbance in the Advanced LIGO gravitational wave detectors, hindering the detection of gravitational waves. The non stationary scatter noise caused by low frequency motion can be recognized as arches in the time-frequency plane of the gravitational wave channel. In this paper, we characterize the scattering noise for LIGO's third observing run O3 from April, 2019 to March, 2020. We find at least two different populations of scattering noise and we investigate the multiple origins of one of them as well as its mitigation. We find that relative motion between two specific surfaces is strongly correlated with the presence of scattered light and we implement a technique to reduce this motion. We also present an algorithm using a witness channel to identify the times this noise can be present in the detector.

Observation of multiplicity-dependent prompt $\chi_{c1}(3872)$ and $\psi(2S)$ production in $pp$ collisions

Abstract: The production of χc1(3872) and ψ(2S) hadrons is studied as a function of charged particle multiplicity in pp collisions at a center-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 2 fb-1. For both states, the fraction that is produced promptly at the collision vertex is found to decrease as charged particle multiplicity increases. The ratio of χc1(3872) to ψ(2S) cross sections for promptly produced particles is also found to decrease with multiplicity, while no significant dependence on multiplicity is observed for the equivalent ratio of particles produced away from the collision vertex in b-hadron decays. This behavior is consistent with a calculation that models the χc1(3872) structure as a compact tetraquark. Comparisons with model calculations and implications for the binding energy of the χc1(3872) state are discussed.

Branching Fraction Measurements of the Rare Bs0 →φμ+μ- And Bs0 → f2′ (1525)μ+μ- Decays

Abstract: The branching fraction of the rare B s 0 → ϕ μ + μ - decay is measured using data collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to integrated luminosities of 1, 2, and 6 fb - 1 , respectively. The branching fraction is reported in intervals of q 2 , the square of the dimuon invariant mass. In the q 2 region between 1.1 and 6.0 GeV 2 / c 4 , the measurement is found to lie 3.6 standard deviations below a standard model prediction based on a combination of light cone sum rule and lattice QCD calculations. In addition, the first observation of the rare B s 0 → f 2 ′ ( 1525 ) μ + μ - decay is reported with a statistical significance of 9 standard deviations and its branching fraction is determined.

Diving below the Spin-down Limit: Constraints on Gravitational Waves from the Energetic Young Pulsar PSR J0537-6910

Abstract: We present a search for quasi-monochromatic gravitational-wave signals from the young, energetic X-ray pulsar PSR J0537−6910 using data from the second and third observing runs of LIGO and Virgo. The search is enabled by a contemporaneous timing ephemeris obtained using Neutron star Interior Composition Explorer (NICER) data. The NICER ephemeris has also been extended through 2020 October and includes three new glitches. PSR J0537−6910 has the largest spin-down luminosity of any pulsar and exhibits fRequent and strong glitches. Analyses of its long-term and interglitch braking indices provide intriguing evidence that its spin-down energy budget may include gravitational-wave emission from a time-varying mass quadrupole moment. Its 62 Hz rotation frequency also puts its possible gravitational-wave emission in the most sensitive band of the LIGO/Virgo detectors. Motivated by these considerations, we search for gravitational-wave emission at both once and twice the rotation frequency from PSR J0537−6910. We find no signal, however, and report upper limits. Assuming a rigidly rotating triaxial star, our constraints reach below the gravitational-wave spin-down limit for this star for the first time by more than a factor of 2 and limit gravitational waves from the l = m = 2 mode to account for less than 14% of the spin-down energy budget. The fiducial equatorial ellipticity is constrained to less than about 3 ×10−5, which is the third best constraint for any young pulsar.

Environmental Noise in Advanced LIGO Detectors

Abstract: The sensitivity of the Advanced LIGO detectors to gravitational waves can be affected by environmental disturbances external to the detectors themselves. Since the transition from the former initial LIGO phase, many improvements have been made to the equipment and techniques used to investigate these environmental effects. These methods have aided in tracking down and mitigating noise sources throughout the first three observing runs of the advanced detector era, keeping the ambient contribution of environmental noise below the background noise levels of the detectors. In this paper we describe the methods used and how they have led to the mitigation of noise sources, the role that environmental monitoring has played in the validation of gravitational wave events, and plans for future observing runs.

Angular Analysis of the B^{+}→K^{*+}μ^{+}μ^{-} Decay

Abstract: We present an angular analysis of the B^{+}→K^{*+}(→K_{S}^{0}π^{+})μ^{+}μ^{-} decay using 9 fb^{-1} of pp collision data collected with the LHCb experiment. For the first time, the full set of CP-averaged angular observables is measured in intervals of the dimuon invariant mass squared. Local deviations from standard model predictions are observed, similar to those in previous LHCb analyses of the isospin-partner B^{0}→K^{*0}μ^{+}μ^{-} decay. The global tension is dependent on which effective couplings are considered and on the choice of theory nuisance parameters.

Searches for continuous gravitational waves from young supernova remnants in the early third observing run of Advanced LIGO and Virgo

Abstract: We present results of three wide-band directed searches for continuous gravitational waves from 15 young supernova remnants in the first half of the third Advanced LIGO and Virgo observing run. We use three search pipelines with distinct signal models and methods of identifying noise artifacts. Without ephemerides of these sources, the searches are conducted over a frequency band spanning from 10~Hz to 2~kHz. We find no evidence of continuous gravitational radiation from these sources. We set upper limits on the intrinsic signal strain at 95% confidence level in sample sub-bands, estimate the sensitivity in the full band, and derive the corresponding constraints on the fiducial neutron star ellipticity and $r$-mode amplitude. The best 95% confidence constraints placed on the signal strain are $7.7\times 10^{-26}$ and $7.8\times 10^{-26}$ near 200~Hz for the supernova remnants G39.2--0.3 and G65.7+1.2, respectively. The most stringent constraints on the ellipticity and $r$-mode amplitude reach $\lesssim 10^{-7}$ and $ \lesssim 10^{-5}$, respectively, at frequencies above $\sim 400$~Hz for the closest supernova remnant G266.2--1.2/Vela Jr.

Observation of a new Ξb0 state

Abstract: Using a proton-proton collision data sample collected by the LHCb experiment, corresponding to an integrated luminosity of 8.5 fb − 1 , the observation of a new excited Ξ 0 b resonance decaying to the Ξ − b π + final state is presented. The state, referred to as Ξ b ( 6227 ) 0 , has a measured mass and natural width of m ( Ξ b ( 6227 ) 0 ) = 6227 . 1 + 1.4 − 1.5 ± 0.5 MeV and Γ ( Ξ b ( 6227 ) 0 ) = 18 . 6 + 5.0 − 4.1 ± 1.4 MeV , where the uncertainties are statistical and systematic. The production rate of the Ξ b ( 6227 ) 0 state relative to that of the Ξ − b baryon in the kinematic region 2 < η < 5 and p T < 30 GeV is measured to be f Ξ b ( 6227 ) 0 f Ξ − b B ( Ξ b ( 6227 ) 0 → Ξ − b π + ) = 0.045 ± 0.008 ± 0.004 , where B ( Ξ b ( 6227 ) 0 → Ξ − b π + ) is the branching fraction of the decay, and f Ξ b ( 6227 ) 0 and f Ξ − b represent fragmentation fractions. Improved measurements of the mass and natural width of the previously observed Ξ b ( 6227 ) − state, along with the mass of the Ξ − b baryon, are also reported. Both measurements are significantly more precise than, and consistent with, previously reported values.

Constraints on dark photon dark matter using data from LIGO's and Virgo's third observing run

Abstract: We present a search for dark photon dark matter that could couple to gravitational-wave interferometers using data from Advanced LIGO and Virgo's third observing run. To perform this analysis, we use two methods, one based on cross-correlation of the strain channels in the two nearly aligned LIGO detectors, and one that looks for excess power in the strain channels of the LIGO and Virgo detectors. The excess power method optimizes the Fourier Transform coherence time as a function of frequency, to account for the expected signal width due to Doppler modulations. We do not find any evidence of dark photon dark matter with a mass between $m_{\rm A} \sim 10^{-14}-10^{-11}$ eV/$c^2$, which corresponds to frequencies between 10-2000 Hz, and therefore provide upper limits on the square of the minimum coupling of dark photons to baryons, i.e. $U(1)_{\rm B}$ dark matter. For the cross-correlation method, the best median constraint on the squared coupling is $\sim1.31\times10^{-47}$ at $m_{\rm A}\sim4.2\times10^{-13}$ eV/$c^2$; for the other analysis, the best constraint is $\sim 1.2\times 10^{-47}$ at $m_{\rm A}\sim 5.7\times 10^{-13}$ eV/$c^2$. These limits improve upon those obtained in direct dark matter detection experiments by a factor of $\sim100$ for $m_{\rm A}\sim [2-4]\times 10^{-13}$ eV/$c^2$.

First Observation of the Decay Bs0 →K-μ+νμ and a Measurement of |Vub | / |Vcb |

Abstract: The first observation of the suppressed semileptonic B_{s}^{0}→K^{-}μ^{+}ν_{μ} decay is reported. Using a data sample recorded in pp collisions in 2012 with the LHCb detector, corresponding to an integrated luminosity of 2 fb^{-1}, the branching fraction B(B_{s}^{0}→K^{-}μ^{+}ν_{μ}) is measured to be [1.06±0.05(stat)±0.08(syst)]×10^{-4}, where the first uncertainty is statistical and the second one represents the combined systematic uncertainties. The decay B_{s}^{0}→D_{s}^{-}μ^{+}ν_{μ}, where D_{s}^{-} is reconstructed in the final state K^{+}K^{-}π^{-}, is used as a normalization channel to minimize the experimental systematic uncertainty. Theoretical calculations on the form factors of the B_{s}^{0}→K^{-} and B_{s}^{0}→D_{s}^{-} transitions are employed to determine the ratio of the Cabibbo-Kobayashi-Maskawa matrix elements |V_{ub}|/|V_{cb}| at low and high B_{s}^{0}→K^{-} momentum transfer.

Observation of a New Excited D_{s}^{+} Meson in B^{0}→D^{-}D^{+}K^{+}π^{-} Decays.

Abstract: Using pp collision data corresponding to an integrated luminosity of 5.4 fb^{-1} collected with the LHCb detector at a center-of-mass energy of 13 TeV, the B^{0}→D^{-}D^{+}K^{+}π^{-} decay is studied. A new excited D_{s}^{+} meson is observed decaying into the D^{+}K^{+}π^{-} final state with large statistical significance. The pole mass and width, and the spin parity of the new state are measured with an amplitude analysis to be m_{R}=2591±6±7 MeV, Γ_{R}=89±16±12 MeV, and J^{P}=0^{-}, where the first uncertainty is statistical and the second systematic. Fit fractions for all components in the amplitude analysis are also reported. The new resonance, denoted as D_{s0}(2590)^{+}, is a strong candidate to be the D_{s}(2^{1}S_{0})^{+} state, the radial excitation of the pseudoscalar ground-state D_{s}^{+} meson.

Constraints from LIGO O3 data on gravitational-wave emission due to r-modes in the glitching pulsar PSR J0537-6910

Abstract: We present a search for continuous gravitational-wave emission due to r-modes in the pulsar PSR J0537-6910 using data from the LIGO-Virgo Collaboration observing run O3. PSR J0537-6910 is a young energetic X-ray pulsar and is the most frequent glitcher known. The inter-glitch braking index of the pulsar suggests that gravitational-wave emission due to r-mode oscillations may play an important role in the spin evolution of this pulsar. Theoretical models confirm this possibility and predict emission at a level that can be probed by ground-based detectors. In order to explore this scenario, we search for r-mode emission in the epochs between glitches by using a contemporaneous timing ephemeris obtained from NICER data. We do not detect any signals in the theoretically expected band of 86-97 Hz, and report upper limits on the amplitude of the gravitational waves. Our results improve on previous amplitude upper limits from r-modes in J0537-6910 by a factor of up to 3 and place stringent constraints on theoretical models for r-mode driven spin-down in PSR J0537-6910, especially for higher frequencies at which our results reach below the spin-down limit defined by energy conservation.

Measurement of CP observables in B±→D(∗)K± and B±→D(∗)π± decays using two-body D final states

Abstract: Measurements of CP observables in B± → D(*)K± and B± → D(*)π± decays are presented, where D(∗) indicates a neutral D or D∗ meson that is an admixture of meson and anti-meson states. Decays of the D(∗) meson to the Dπ0 and Dγ final states are partially reconstructed without inclusion of the neutral pion or photon. Decays of the D meson are reconstructed in the K±π∓, K+K−, and π+π− final states. The analysis uses a sample of charged B mesons produced in proton-proton collisions and collected with the LHCb experiment, corresponding to integrated luminosities of 2.0, 1.0, and 5.7 fb−1 taken at centre-of-mass energies of 7, 8, and 13 TeV, respectively. The measurements of partially reconstructed B± → D(*)K± and B± → D(∗)π± with D → K∓π± decays are the first of their kind, and a first observation of the B± → (Dπ0)D∗π± decay is made with a significance of 6.1 standard deviations. All CP observables are measured with world-best precision, and in combination with other LHCb results will provide strong constraints on the CKM angle γ. [Figure not available: see fulltext.]

Observation of the Mass Difference between Neutral Charm-Meson Eigenstates.

Abstract: A measurement of mixing and C P violation in neutral charm mesons is performed using data reconstructed in proton-proton collisions collected by the LHCb experiment from 2016 to 2018, corresponding to an integrated luminosity of 5.4 fb - 1 . A total of 30.6 million D 0 → K S 0 π + π - decays are analyzed using a method optimized for the measurement of the mass difference between neutral charm-meson eigenstates. Allowing for C P violation in mixing and in the interference between mixing and decay, the mass and decay-width differences are measured to be x C P = [ 3.97 ± 0.46 ( stat ) ± 0.29 ( syst ) ] × 1 0 - 3 and y C P = [ 4.59 ± 1.20 ( stat ) ± 0.85 ( syst ) ] × 1 0 - 3 , respectively. The C P -violating parameters are measured as Δ x = [ - 0.27 ± 0.18 ( stat ) ± 0.01 ( syst ) ] × 1 0 - 3 and Δ y = [ 0.20 ± 0.36 ( stat ) ± 0.13 ( syst ) ] × 1 0 - 3 . This is the first observation of a nonzero mass difference in the D 0 meson system, with a significance exceeding seven standard deviations. The data are consistent with C P symmetry and improve existing constraints on the associated parameters.

Search for the doubly heavy baryons Omega(0)(bc) and Xi(0)(bc) decaying to Lambda(+)(c)pi(-) and Xi(+)(c)pi-

Abstract: The first search for the doubly heavy \begin{document}$ {{{{\varOmega}_{bc}^{0}}}} $\end{document} baryon and a search for the \begin{document}$ {{{{\varXi}_{bc}^{0}}}} $\end{document} baryon are performed using \begin{document}$ pp $\end{document} collision data collected via the \begin{document}$ {\rm{LHCb}} $\end{document} experiment from 2016 to 2018 at a centre-of-mass energy of \begin{document}$ 13 \;{\rm{TeV}} $\end{document} , corresponding to an integrated luminosity of 5.2 \begin{document}$ \;{\rm{f}}{{\rm{b}}^{ - 1}} $\end{document} . The baryons are reconstructed via their decays to \begin{document}$ {{{{\varLambda}^+_c}}} {{{{\pi}^-}}} $\end{document} and \begin{document}$ {{{{\varXi}^+_c}}} {{{{\pi}^-}}} $\end{document} . No significant excess is found for invariant masses between 6700 and 7300 \begin{document}$ \;{\rm{MeV}}/{c^2} $\end{document} , in a rapidity range from 2.0 to 4.5 and a transverse momentum range from 2 to 20 \begin{document}$ \;{\rm{MeV}}/{c} $\end{document} . Upper limits are set on the ratio of the \begin{document}$ {{{{\varOmega}_{bc}^{0}}}} $\end{document} and \begin{document}$ {{{{\varXi}_{bc}^{0}}}} $\end{document} production cross-section times the branching fraction to \begin{document}$ {{{{\varLambda}^+_c}}}{{{{\pi}^-}}} $\end{document} ( \begin{document}$ {{{{\varXi}^+_c}}}{{{{\pi}^-}}} $\end{document} ) relative to that of the \begin{document}$ {{{{\varLambda}^0_b}}} $\end{document} ( \begin{document}$ {{{{\varXi}_{b}^{0}}}} $\end{document} ) baryon, for different lifetime hypotheses, at 95% confidence level. The upper limits range from \begin{document}$ 0.5\times10^{-4} $\end{document} to \begin{document}$ 2.5\times10^{-4} $\end{document} for the \begin{document}$ {{{{{{{{\varOmega}_{bc}^{0}}}}{{\rightarrow }}{{{{\varLambda}^+_c}}}{{{{\pi}^-}}}}}}} $\end{document} ( \begin{document}$ {{{{{{{{\varXi}_{bc}^{0}}}}{{\rightarrow }}{{{{\varLambda}^+_c}}}{{{{\pi}^-}}}}}}} $\end{document} ) decay, and from \begin{document}$ 1.4\times10^{-3} $\end{document} to \begin{document}$ 6.9\times10^{-3} $\end{document} for the \begin{document}$ {{{{{{{{\varOmega}_{bc}^{0}}}}{{\rightarrow }}{{{{\varXi}^+_c}}}{{{{\pi}^-}}}}}}} $\end{document} ( \begin{document}$ {{{{{{{{\varXi}_{bc}^{0}}}}{{\rightarrow }}{{{{\varXi}^+_c}}}{{{{\pi}^-}}}}}}} $\end{document} ) decay, depending on the considered mass and lifetime of the \begin{document}$ {{{{\varOmega}_{bc}^{0}}}} $\end{document} ( \begin{document}$ {{{{\varXi}_{bc}^{0}}}} $\end{document} ) baryon.

LIGO’s quantum response to squeezed states

Abstract: Gravitational Wave interferometers achieve their profound sensitivity by combining a Michelson interferometer with optical cavities, suspended masses, and now, squeezed quantum states of light. These states modify the measurement process of the LIGO, VIRGO and GEO600 interferometers to reduce the quantum noise that masks astrophysical signals; thus, improvements to squeezing are essential to further expand our gravitational view of the universe. Further reducing quantum noise will require both lowering decoherence from losses as well more sophisticated manipulations to counter the quantum back-action from radiation pressure. Both tasks require fully understanding the physical interactions between squeezed light and the many components of km-scale interferometers. To this end, data from both LIGO observatories in observing run three are expressed using frequency-dependent metrics to analyze each detector's quantum response to squeezed states. The response metrics are derived and used to concisely describe physical mechanisms behind squeezing's simultaneous interaction with transverse-mode selective optical cavities and the quantum radiation pressure noise of suspended mirrors. These metrics and related analysis are broadly applicable for cavity-enhanced optomechanics experiments that incorporate external squeezing, and -- for the first time -- give physical descriptions of every feature so far observed in the quantum noise of the LIGO detectors.

Search for heavy neutral leptons in W+→μ+μ±jet decays

Abstract: A search is performed for heavy neutrinos in the decay of a W boson into two muons and a jet. The data set corresponds to an integrated luminosity of approximately $$3.0\, \text {fb} ^{-1} $$ of proton–proton collision data at centre-of-mass energies of 7 and $$8\, \text {TeV} $$ collected with the LHCb experiment. Both same-sign and opposite-sign muons in the final state are considered. Data are found to be consistent with the expected background. Upper limits on the coupling of a heavy neutrino with the Standard Model neutrino are set at $$95\%$$ confidence level in the heavy-neutrino mass range from 5 to $$50\, \text {GeV/}c^2 $$ . These are of the order of $$10^{-3}$$ for lepton-number-conserving decays and of the order of $$10^{-4}$$ for lepton-number-violating heavy-neutrino decays.