A time-delay determination from VLA light curves of the CLASS gravitational lens B1600+434

We present Very Large Array (VLA) 8.5-GHz light curves of the two lens images of the Cosmic Lens All Sky Survey (CLASS) gravitational lens B1600+434. We find a nearly linear decrease of 18-19% in the flux densities of both lens images over a period of eight months (February-October) in 1998. Additionally, the brightest image A shows modulations up to 11% peak-to-peak on scales of days to weeks over a large part of the observing period. Image B varies significantly less on this time scale. We conclude that most of the short-term variability in image A is not intrinsic source variability, but is most likely caused by microlensing in the lens galaxy. The alternative, scintillation by the ionized Galactic ISM, is shown to be implausible based on its strong opposite frequency dependent behavior compared with results from multi-frequency WSRT monitoring observations (Koopmans & de Bruyn 1999). From these VLA light curves we determine a median time delay between the lens images of 47^{+5}_{-6} d (68%) or 47^{+12}_{-9} d (95%). We use two different methods to derive the time delay; both give the same result within the errors. We estimate an additional systematic error between -8 and +7 d. If the mass distribution of lens galaxy can be described by an isothermal model (Koopmans, de Bruyn & Jackson 1998), this time delay would give a value for the Hubble parameter, H_0=57^{+14}_{-11} (95% statistical) ^{+26}_{-15} (systematic) km/s/Mpc (Omega_m=1 and Omega_Lambda=0). Similarly, the Modified-Hubble-Profile mass model would give H_0=74^{+18}_{-15} (95% statistical) ^{+22}_{-22} (systematic) km/s/Mpc. For Omega_m=0.3 and Omega_Lambda=0.7, these values increase by 5.4%. ... (ABRIDGED)Comment: 14 pages, 6 figures, accepted for publication in Astronomy & Astrophysics (Figs 1 and 3 with degraded resolution

A chemical ionization mass spectrometer for continuous underway shipboard analysis of dimethylsulfide in near-surface seawater

A compact, low-cost atmospheric pressure, chemical ionization mass spectrometer ("mini-CIMS") has been developed for continuous underway shipboard measurements of dimethylsulfide (DMS) in seawater. The instrument was used to analyze DMS in air equilibrated with flowing seawater across a porous Teflon membrane equilibrator. The equilibrated gas stream was diluted with air containing an isotopically-labeled internal standard. DMS is ionized at atmospheric pressure via proton transfer from water vapor, then declustered, mass filtered via quadrupole mass spectrometry, and detected with an electron multiplier. The instrument described here is based on a low-cost residual gas analyzer (Stanford Research Systems), which has been modified for use as a chemical ionization mass spectrometer. The mini-CIMS has a gas phase detection limit of 220 ppt DMS for a 1 min averaging time, which is roughly equivalent to a seawater DMS concentration of 0.1 nM DMS at 20°C. The mini-CIMS has the sensitivity, selectivity, and time response required for underway measurements of surface ocean DMS over the full range of oceanographic conditions. The simple, robust design and relatively low cost of the instrument are intended to facilitate use in process studies and surveys, with potential for long-term deployment on research vessels, ships of opportunity, and large buoys

Search for the Rare Decays B 0 s → e + e − and B 0 → e + e −

A search for the decays Bs0→e+e- and B0→e+e- is performed using data collected with the LHCb experiment in proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV, corresponding to integrated luminosities of 1, 2, and 2 fb-1, respectively. No signal is observed. Assuming no contribution from B0→e+e- decays, an upper limit on the branching fraction B(Bs0→e+e-)&lt;9.4(11.2)×10-9 is obtained at 90(95)% confidence level. If no Bs0→e+e- contribution is assumed, a limit of B(B0→e+e-)&lt;2.5(3.0)×10-9 is determined at 90(95)% confidence level. These upper limits are more than one order of magnitude lower than the previous values.</p

Observation of New Ξ 0 c Baryons Decaying to Λ + c K −

The Λc+K- mass spectrum is studied with a data sample of pp collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 5.6 fb-1 collected by the LHCb experiment. Three Ξc0 states are observed with a large significance and their masses and natural widths are measured to be m[Ξc(2923)0]=2923.04±0.25±0.20±0.14 MeV, Γ[Ξc(2923)0]=7.1±0.8±1.8 MeV, m[Ξc(2939)0]=2938.55±0.21±0.17±0.14 MeV, Γ[Ξc(2939)0]=10.2±0.8±1.1 MeV, m[Ξc(2965)0]=2964.88±0.26±0.14±0.14 MeV, Γ[Ξc(2965)0]=14.1±0.9±1.3 MeV, where the uncertainties are statistical, systematic, and due to the limited knowledge of the Λc+ mass. The Ξc(2923)0 and Ξc(2939)0 baryons are new states. The Ξc(2965)0 state is in the vicinity of the known Ξc(2970)0 baryon; however, their masses and natural widths differ significantly

Study of the ψ2(3823) and χc1(3872) states in B+ → (J/ψπ+π−)K+ decays

The decays B+→ J/ψπ+π−K+ are studied using a data set corresponding to an integrated luminosity of 9 fb−1 collected with the LHCb detector in proton-proton collisions between 2011 and 2018. Precise measurements of the ratios of branching fractions with the intermediate ψ2(3823), χc1(3872) and ψ(2S) states are reported. The values areBB+→ψ2(3823)K+×Bψ2(3823)→J/ψπ+π−BB+→χc1(3872)K+×Bχc1(3872)→J/ψπ+π−=(3.56±0.67±0.11)×10−2,BB+→ψ2(3823)K+×Bψ2(3823)→J/ψπ+π−BB+→ψ(2S)K+×Bψ(2S)→J/ψπ+π−=(1.31±0.25±0.04)×10−3,BB+→χc1(3872)K+×Bχc1(3872)→J/ψπ+π−BB+→ψ(2S)K+×Bψ(2S)→J/ψπ+π−=(3.69±0.07±0.06)×10−2, where the first uncertainty is statistical and the second is systematic. The decay of B+→ ψ2(3823)K+ with ψ2(3823) → J/ψπ+π− is observed for the first time with a significance of 5.1 standard deviations. The mass differences between the ψ2(3823), χc1(3872) and ψ(2S) states are measured to be mχc1(3872)−mψ2(3823)=47.50±0.53±0.13MeV/c2,mψ2(3823)−mψ2(2S)=137.98±0.53±0.14MeV/c2,mχc1(3872)−mψ2(2S)=185.49±0.06±0.03MeV/c2, resulting in the most precise determination of the χc1(3872) mass. The width of the ψ2(3823) state is found to be below 5.2 MeV at 90% confidence level. The Breit-Wigner width of the χc1(3872) state is measured to be Γχc1(3872)BW=0.96−0.18+0.19±0.21MeV which is inconsistent with zero by 5.5 standard deviations. [Figure not available: see fulltext.

Observation of a new baryon state in the Λ0bπ+π− mass spectrum

A new baryon state is observed in the Λb0π+π− mass spectrum with high significance using a data sample of pp collisions, collected with the LHCb detector at centre-of-mass energies s = 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb−1. The mass and natural width of the new state are measured to be m=6072.3±2.9±0.6±0.2MeV,Γ=72±11±2MeV, where the first uncertainty is statistical and the second systematic. The third uncertainty for the mass is due to imprecise knowledge of the Λb0 baryon mass. The new state is consistent with the first radial excitation of the Λb0 baryon, the Λb(2S)0 resonance. Updated measurements of the masses and the upper limits on the natural widths of the previously observed Λb(5912)0 and Λb(5920)0 states are also reported. [Figure not available: see fulltext.

First Observation of Excited Ω − b States

We report four narrow peaks in the Ξb0K- mass spectrum obtained using pp collisions at center-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb-1 recorded by the LHCb experiment. Referring to these states by their mass, the mass values are m[ωb(6316)-]=6315.64±0.31±0.07±0.50 MeV, m[ωb(6330)-]=6330.30±0.28±0.07±0.50 MeV, m[ωb(6340)-]=6339.71±0.26±0.05±0.50 MeV, m[ωb(6350)-]=6349.88±0.35±0.05±0.50 MeV, where the uncertainties are statistical, systematic, and the last is due to the knowledge of the Ξb0 mass. The natural widths of the three lower mass states are consistent with zero, and the 90% confidence-level upper limits are determined to be Γ[ωb(6316)-]<2.8 MeV, Γ[ωb(6330)-]<3.1 MeV and Γ[ωb(6340)-]<1.5 MeV. The natural width of the ωb(6350)- peak is 1.4-0.8+1.0±0.1 MeV, which is 2.5σ from zero and corresponds to an upper limit of 2.8 MeV. The peaks have local significances ranging from 3.6σ to 7.2σ. After accounting for the look-elsewhere effect, the significances of the ωb(6316)- and ωb(6330)- peaks are reduced to 2.1σ and 2.6σ, respectively, while the two higher mass peaks exceed 5σ. The observed peaks are consistent with expectations for excited ωb- resonances

Search for the lepton flavour violating decay B+ → K+μ−τ+ using B∗0s2 decays

A search is presented for the lepton flavour violating decay B+ → K+μ−τ+ using a sample of proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of 9 fb−1. The τ leptons are selected inclusively, primarily via decays with a single charged particle. The four-momentum of the τ lepton is determined by using B+ mesons from Bs2∗0→B+K− decays. No significant excess is observed, and an upper limit is set on the branching fraction ℬ(B+ → K+μ−τ+) < 3.9 × 10−5 at 90 % confidence level. The obtained limit is comparable to the world-best limit. [Figure not available: see fulltext.]

Measurement of C P -Averaged Observables in the B 0 → K * 0 μ + μ − Decay

An angular analysis of the B0→K*0(→K+π−)μ+μ− decay is presented using a dataset corresponding to an integrated luminosity of 4.7  fb−1 of pp collision data collected with the LHCb experiment. The full set of CP-averaged observables are determined in bins of the invariant mass squared of the dimuon system. Contamination from decays with the K+π− system in an S-wave configuration is taken into account. The tension seen between the previous LHCb results and the standard model predictions persists with the new data. The precise value of the significance of this tension depends on the choice of theory nuisance parameters

Precision measurement of the B+c meson mass

A precision measurement of the Bc+ meson mass is performed using proton- proton collision data collected with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to a total integrated luminosity of 9.0 fb−1. The Bc+ mesons are reconstructed via the decays Bc+→ J/ψπ+, Bc+→ J/ψπ+π−π+, Bc+→J/ψpp¯π+, Bc+→J/ψDs+, Bc+→ J/ψ D0K+ and Bc+→Bs0π+. Combining the results of the individual decay channels, the Bc+ mass is measured to be 6274.47 ± 0.27 (stat) ± 0.17 (syst) MeV/c2. This is the most precise measurement of the Bc+ mass to date. The difference between the Bc+ and Bs0 meson masses is measured to be 907.75 ± 0.37 (stat) ± 0.27 (syst) MeV/c. [Figure not available: see fulltext.