arXiv subjects

J. E. Andrews

Publications and source records attributed to J. E. Andrews.

At least 55 records · Page 3Linked to original sources

arXiv2019

Search for the rare decay $B^{+} \rightarrow μ^{+}μ^{-}μ^{+}ν_{μ}$

A search for the rare leptonic decay $B^{+} \rightarrow μ^{+}μ^{-}μ^{+}ν_{μ}$ is performed using proton-proton collision data corresponding to an integrated luminosity of $4.7$ fb$^{-1}$ collected by the LHCb experiment. The search is carried out in the region where the lowest of the two $μ^{+}μ^{-}$ mass combinations is below $980$MeV/c$^{2}$. The data are consistent with the background-only hypothesis and an upper limit of $1.6 \times 10^{-8}$ at 95% confidence level is set on the branching fraction in the stated kinematic region.

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arXiv2019

Measurement of b-hadron fractions in 13 TeV pp collisions

The production fractions of $\overline{B}_s^0$ and $Λ_b^0$ hadrons, normalized to the sum of $B^-$ and $\overline{B}^0$ fractions, are measured in 13 TeV pp collisions using data collected by the LHCb experiment, corresponding to an integrated luminosity of 1.67/fb. These ratios, averaged over the $b$-hadron transverse momenta from 4 to 25 GeV and pseudorapidity from 2 to 5, are $0.122 \pm 0.006$ for $\overline{B}_s^0$, and $0.259 \pm 0.018$ for $Λ_b^0$, where the uncertainties arise from both statistical and systematic sources. The $Λ_b^0$ ratio depends strongly on transverse momentum, while the $\overline{B}_s^0$ ratio shows a mild dependence. Neither ratio shows variations with pseudorapidity. The measurements are made using semileptonic decays to minimize theoretical uncertainties. In addition, the ratio of $D^+$ to $D^0$ mesons produced in the sum of $\overline{B}^0$ and $B^-$ semileptonic decays is determined as $0.359\pm0.006\pm 0.009$, where the uncertainties are statistical and systematic.

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arXiv2019

Measurement of $C\!P$ observables in the process $B^0 \to DK^{*0}$ with two- and four-body $D$ decays

Measurements of $C\!P$ observables in $B^0 \to DK^{*0}$ decays are presented, where $D$ represents a superposition of $D^0$ and $\bar{D}^0$ states. The $D$ meson is reconstructed in the two-body final states $K^+π^-$, $π^+ K^-$, $K^+K^-$ and $π^+π^-$, and, for the first time, in the four-body final states $K^+π^-π^+π^-$, $π^+ K^-π^+π^-$ and $π^+π^-π^+π^-$. The analysis uses a sample of neutral $B$ mesons produced in proton-proton collisions, corresponding to an integrated luminosity of 1.0, 2.0 and 1.8 $\rm fb^{-1}$ collected with the LHCb detector at centre-of-mass energies of $\sqrt{s} = $ 7, 8 and 13 TeV, respectively. First observations of the decays $B^0 \to D(π^+ K^-)K^{*0}$ and $B^0 \to D(π^+π^-π^+π^-)K^{*0}$ are obtained. The measured observables are interpreted in terms of the $C\!P$-violating weak phase $γ$.

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arXiv2019

Measurement of the $CP$-violating phase $ϕ_s$ from $B_{s}^{0}\to J/ψπ^+π^-$ decays in 13 TeV $pp$ collisions

Decays of $B_{s}^{0}$ and $\overline{B}{}_{s}^{0}$ mesons into $J/ψπ^+π^-$ final states are studied in a data sample corresponding to 1.9 fb$^{-1}$ of integrated luminosity collected with the LHCb detector in 13 TeV $pp$ collisions. A time-dependent amplitude analysis is used to determine the final-state resonance contributions, the $CP$-violating phase $ϕ_s=-0.057\pm 0.060\pm 0.011$ rad, the decay-width difference between the heavier mass $B_{s}^{0}$ eigenstate and the $B^{0}$ meson of $-0.050\pm 0.004\pm 0.004$ ps$^{-1}$, and the $CP$-violating parameter $|λ|=1.01_{-0.06}^{+0.08}\pm0.03$, where the first uncertainty is statistical and the second systematic. These results are combined with previous LHCb measurements in the same decay channel using 7 TeV and 8 TeV $pp$ collisions obtaining $ϕ_s =0.002\pm0.044\pm0.012$ rad, and $|λ| =0.949\pm0.036\pm0.019$.

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arXiv2019

Precision measurement of the $Λ_c^+$, $Ξ_c^+$ and $Ξ_c^0$ baryon lifetimes

We report measurements of the lifetimes of the $Λ_c^+$, $Ξ_c^+$ and $Ξ_c^0$ charm baryons using proton-proton collision data at center-of-mass energies of 7 and 8\tev, corresponding to an integrated luminosity of 3.0 fb$^{-1}$, collected by the LHCb experiment. The charm baryons are reconstructed through the decays $Λ_c^+\to pK^-π^+$, $Ξ_c^+\to pK^-π^+$ and $Ξ_c^0\to pK^-K^-π^+$, and originate from semimuonic decays of beauty baryons. The lifetimes are measured relative to that of the $D^+$ meson, and are determined to be \begin{align*} τ_{Λ_c^+} &= 203.5\pm1.0\pm1.3\pm1.4~{\rm fs}, \newline τ_{Ξ_c^+} &= 456.8\pm3.5\pm2.9\pm3.1~{\rm fs}, \newline τ_{Ξ_c^0} &= 154.5\pm1.7\pm1.6\pm1.0~{\rm fs}, \end{align*} where the uncertainties are statistical, systematic, and due to the uncertainty in the $D^+$ lifetime. The measurements are approximately 3--4 times more precise than the current world average values. The $Λ_c^+$ and $Ξ_c^+$ lifetimes are in agreement with previous measurements; however, the $Ξ_c^0$ baryon lifetime is approximately 3.3 standard deviations larger than the world average value.

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arXiv2019

Near-threshold $D\bar{D}$ spectroscopy and observation of a new charmonium state

Using proton-proton collision data, corresponding to an integrated luminosity of 9$fb^{-1}$, collected with the~LHCb detector between 2011 and 2018, a new narrow charmonium state, the $X(3842)$ resonance, is observed in the decay modes $X(3842)\rightarrow D^0\bar{D}^0$ and $X(3842)\rightarrow D^+D^-$. The mass and the natural width of this state are measured to be \begin{eqnarray*} m_{X(3842)} & = & 3842.71 \pm 0.16 \pm 0.12 MeV/c^2\,, Γ_{X(3842)} & = & 2.79 \pm 0.51 \pm 0.35 MeV\,, \end{eqnarray*} where the first uncertainty is statistical and the~second is systematic. The observed mass and narrow natural width suggest the~interpretation of the new state as the~unobserved spin\nobreakdash-3 $ψ_3\mathrm{\left(1^3D_3\right)}$ charmonium state. In addition, prompt hadroproduction of the $ψ(3770)$~and $χ_{c2}(3930)$ states is observed for the first time, and the parameters of these~states are measured to be \begin{eqnarray*} m_{ψ(3770)} & = & 3778.1 \pm 0.7 \pm 0.6 MeV/c^2\,, m_{χ_{c2}(3930)} & = & 3921.9 \pm 0.6 \pm 0.2 MeV/c^2\,, Γ_{χ_{c2}(3930)} & = &36.6 \pm 1.9 \pm 0.9 MeV\,, \end{eqnarray*} where the first uncertainty is statistical and the~second is systematic.

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arXiv2019

The aspherical explosion of the Type IIP SN 2017gmr

Type IIP supernovae (SNe IIP), which represent the most common class of core-collapse (CC) SNe, show a rapid increase in continuum polarization just after entering the tail phase. This feature can be explained by a highly asymmetric helium core, which is exposed when the hydrogen envelope becomes transparent. Here we report the case of a SN IIP (SN~2017gmr) that shows an unusually early rise of the polarization, $\gtrsim 30$ days before the start of the tail phase. This implies that SN~2017gmr is an SN IIP that has very extended asphericity. The asymmetries are not confined to the helium core, but reach out to a significant part of the outer hydrogen envelope, hence clearly indicating a marked intrinsic diversity in the aspherical structure of CC explosions. These observations provide new constraints on the explosion mechanism, where viable models must be able to produce such extended deviations from spherical symmetry, and account for the observed geometrical diversity.

astro-ph.HE↗

arXiv2019

First observation of the radiative decay $Λ_{b}^{0} \to Λγ$

The radiative decay $Λ_{b}^{0} \to Λγ$ is observed for the first time using a data sample of proton-proton collisions corresponding to an integrated luminosity of $1.7\,fb^{-1}$ collected by the LHCb experiment at a center-of-mass energy of $13\,TeV$. Its branching fraction is measured exploiting the $B^{0} \to K^{*0} γ$ decay as a normalization mode and is found to be $\mathcal{B}(Λ_{b}^{0} \to Λγ)= (7.1 \pm 1.5 \pm 0.6 \pm 0.7) \times 10^{-6}$, where the quoted uncertainties are statistical, systematic and systematic from external inputs, respectively. This is the first observation of a radiative decay of a beauty baryon.

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arXiv2019

Searches After Gravitational-waves Using ARizona Observatories (SAGUARO): System Overview and First Results from Advanced LIGO/Virgo's Third Observing Run

We present Searches After Gravitational-waves Using ARizona Observatories (SAGUARO), a comprehensive effort dedicated to the discovery and characterization of optical counterparts to gravitational wave (GW) events. SAGUARO utilizes ground-based facilities ranging from 1.5m to 10m in diameter, located primarily in the Northern Hemisphere. We provide an overview of SAGUARO's telescopic resources, pipeline for transient detection, and database for candidate visualization. We describe SAGUARO's discovery component, which utilizes the $5$~deg$^2$ field-of-view optical imager on the Mt. Lemmon 1.5m telescope, reaching limits of $\approx 21.3$~AB mag while rapidly tiling large areas. We also describe the follow-up component of SAGUARO, used for rapid vetting and monitoring of optical candidates. With the onset of Advanced LIGO/Virgo's third observing run, we present results from the first three SAGUARO searches following the GW events S190408an, S190425z and S190426c, which serve as a valuable proof-of-concept of SAGUARO. We triggered and searched 15, 60 and 60 deg$^{2}$ respectively, 17.6, 1.4 and 41.8 hrs after the initial GW alerts. We covered 7.8, 3.0 and 5.1\% of the total probability within the GW event localizations, reaching 3$σ$ limits of 19.8, 21.3 and 20.8 AB mag, respectively. Although no viable counterparts associated with these events were found, we recovered 6 known transients and ruled out 5 potential candidates. We also present Large Binocular Telescope spectroscopy of PS19eq/SN2019ebq, a promising kilonova candidate that was later determined to be a supernova. With the ability to tile large areas and conduct detailed follow-up, SAGUARO represents a significant addition to GW counterpart searches.

astro-ph.HE↗

arXiv2019

Amplitude analysis of the $B_{(s)} \to K^{0} \overline{K}^{0}$ decays and measurement of the branching fraction of the $B \to K^{0} \overline{K}^{0}$ decay

The $B^0 \to K^{*0} \overline{K}^{*0}$ and $B^0_s \to K^{*0} \overline{K}^{*0}$ decays are studied using proton-proton collision data corresponding to an integrated luminosity of 3fb$^{-1}$. An untagged and time-integrated amplitude analysis of $B^0_{(s)} \to (K^+π^-)(K^-π^+) $ decays in two-body invariant mass regions of 150 MeV$/c^2$ around the $K^{*0}$ mass is performed. A stronger longitudinal polarisation fraction in the ${B^0 \to K^{*0} \overline{K}^{*0}}$ decay, ${f_L = 0.724 \pm 0.051 \,({\rm stat}) \pm 0.016 \,({\rm syst})}$, is observed as compared to ${f_L = 0.240 \pm 0.031 \,({\rm stat}) \pm 0.025 \,({\rm syst})}$ in the ${B^0_s\to K^{*0} \overline{K}^{*0}}$ decay. The ratio of branching fractions of the two decays is measured and used to determine $\mathcal{B}(B^0 \to K^{*0} \overline{K}^{*0}) = (8.0 \pm 0.9 \,({\rm stat}) \pm 0.4 \,({\rm syst})) \times 10^{-7}$.

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arXiv2019

Amplitude analysis of $B^{0}_{s} \rightarrow K^{0}_{\textrm{S}} K^{\pm}π^{\mp}$ decays

The first untagged decay-time-integrated amplitude analysis of $B^{0}_{s} \rightarrow K^{0}_{\textrm{S}} K^{\pm}π^{\mp}$ decays is performed using a sample corresponding to $3.0\,$fb$^{-1}$ of $pp$ collision data recorded with the LHCb detector during 2011 and 2012. The data are described with an amplitude model that contains contributions from the intermediate resonances $K^{*}(892)^{0,+}$, $K^*_2(1430)^{0,+}$ and $K^*_0(1430)^{0,+}$, and their charge conjugates. Measurements of the branching fractions of the decay modes $B^{0}_{s} \rightarrow K^{*}(892)^{\pm}K^{\mp}$ and $B^{0}_{s} \rightarrow K^{*}(892)^{0}\kern 0.2em\overline{\kern -0.2em K}{}^{0}, \kern 0.2em\overline{\kern -0.2em K}{}^{*}(892)^{0}K^{0}$ are in agreement with, and more precise than, previous results. The decays $B^{0}_{s} \rightarrow K^*_0(1430)^{\pm} K^{\mp}$ and $B^{0}_{s} \rightarrow K^{*}_{0}(1430)^{0}\kern 0.2em\overline{\kern -0.2em K}{}^{0}, \kern 0.2em\overline{\kern -0.2em K}{}^{*}_{0}(1430)^{0}K^{0}$ are observed for the first time, each with significance over 10 standard deviations.

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arXiv2019

Measurement of the branching fraction and $C\!P$ asymmetry in $B^{+}\rightarrow J/ψρ^{+}$ decays

The branching fraction and direct $C\!P$ asymmetry of the decay $B^{+}\rightarrow J/ψρ^{+}$ are measured using proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV, corresponding to a total integrated luminosity of 3$\mbox{fb}^{-1}$. The following results are obtained: \begin{align} \mathcal{B}(B^{+}\rightarrow J/ψρ^{+}) &= (3.81 ^{+0.25}_{-0.24} \pm 0.35) \times 10^{-5}, \nonumber \\ \mathcal{A}^{C\!P} (B^{+}\rightarrow J/ψρ^{+}) &= -0.045^{+0.056}_{-0.057} \pm 0.008, \nonumber \end{align} where the first uncertainties are statistical and the second systematic. Both measurements are the most precise to date.

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arXiv2019

Measurement of the mass difference between neutral charm-meson eigenstates

We report a measurement of the mass difference between neutral charm-meson eigenstates using a novel approach that enhances sensitivity to this parameter. We use $2.3\times 10^6$ $D^0\to K_S^0π^+π^-$ decays reconstructed in proton-proton collisions collected by the \lhcb experiment in 2011 and 2012. Allowing for $CP$ violation in mixing and in the interference between mixing and decay, we measure the $CP$-averaged normalized mass difference $x_{CP} = \left[2.7\pm1.6\text{(stat)}\pm0.4\text{(syst)}\right]\times10^{-3}$ and the $CP$-violating parameter $Δx = \left[-0.53\pm0.70\text{(stat)}\pm0.22\text{(syst)}\right]\times10^{-3}$. The results are consistent with $CP$ symmetry. These determinations are the most precise from a single experiment and, combined with current world-average results, yield the first evidence that the masses of the neutral charm-meson eigenstates differ.

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arXiv2019

Observation of an excited $B_c^+$ state

Using $pp$ collision data corresponding to an integrated luminosity of $8.5\,\mathrm{fb}^{-1}$ recorded by the LHCb experiment at centre-of-mass energies of $\sqrt{s} = 7$, $8$ and $13\mathrm{\,Te\kern -0.1em V}$, the observation of an excited $B_c^+$ state in the $B_c^+π^+π^-$ invariant-mass spectrum is reported. The observed peak has a mass of $6841.2 \pm 0.6 {\,\rm (stat)\,} \pm 0.1 {\,\rm (syst)\,} \pm 0.8\,(B_c^+) \mathrm{\,MeV}/c^2$, where the last uncertainty is due to the limited knowledge of the $B_c^+$ mass. It is consistent with expectations of the $B_c^{*}(2^{3}S_{1})^+$ state reconstructed without the low-energy photon from the $B_c^{*}(1^{3}S_{1})^+ \to B_c^+ γ$ decay following $B_c^{*}(2^{3}S_{1})^+ \to B_c^{*}(1^{3}S_{1})^+ π^+ π^-$. A second state is seen with a global (local) statistical significance of $2.2\,σ$ ($3.2\,σ$) and a mass of $6872.1 \pm 1.3 {\,\rm (stat)\,} \pm 0.1 {\,\rm (syst)\,} \pm 0.8\,(B_c^+) \mathrm{\,MeV}/c^2$, and is consistent with the $B_c(2^{1}S_{0})^+$ state. These mass measurements are the most precise to date.

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arXiv2019

Measurement of the relative $B^{-} \!\rightarrow D^{0} / D^{*0} / D^{**0} μ^{-} \overlineν_μ$ branching fractions using $B^{-}$ mesons from $\overline{B}{}_{s2}^{*0}$ decays

The decay of the narrow resonance $\overline{B}{}_{s2}^{*0}\!\rightarrow B^- K^+$ can be used to determine the $B^-$ momentum in partially reconstructed decays without any assumptions on the decay products of the $B^-$ meson. This technique is employed for the first time to distinguish contributions from $D^0$, $D^{*0}$, and higher-mass charmed states ($D^{**0}$) in semileptonic $B^-$ decays by using the missing-mass distribution. The measurement is performed using a data sample corresponding to an integrated luminosity of 3.0 fb${}^{-1}$ collected with the LHCb detector in $pp$ collisions at center-of-mass energies of 7 and 8 TeV. The resulting branching fractions relative to the inclusive $B^- \!\rightarrow D^0 X μ^- \overlineν_μ$ are $f_{D^0} = \mathcal{B}( B^- \rightarrow D^0μ^-\overlineν_μ)/\mathcal{B}( B^- \rightarrow D^0 X μ^- \overlineν_μ) = 0.25 \pm 0.06$, $f_{D^{**0}} = \mathcal{B}( B^- \rightarrow ( D^{**0} \rightarrow D^0 X)μ^-\overlineν_μ)/\mathcal{B}( B^- \rightarrow D^0 X μ^- \overlineν_μ) = 0.21 \pm 0.07$, with $f_{D^{*0}} = 1 - f_{D^0} - f_{D^{**0}}$ making up the remainder.

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arXiv2019

Observation of $C\!P$ violation in charm decays

A search for charge-parity ($C\!P$) violation in $D^0 \to K^- K^+$ and $D^0 \to π^- π^+$ decays is reported, using $pp$ collision data corresponding to an integrated luminosity of 6 $\mathrm{fb}^{-1}$ collected at a center-of-mass energy of 13 TeV with the LHCb detector. The flavor of the charm meson is inferred from the charge of the pion in $D^*(2010)^+ \to D^0 π^+$ decays or from the charge of the muon in $\overline{B} \to D^0 μ^-\barν_μX$ decays. The difference between the $C\!P$ asymmetries in $D^0 \to K^- K^+$ and $D^0 \to π^- π^+$ decays is measured to be $ΔA_{C\!P} = [ -18.2 \pm 3.2\,(\rm stat.) \pm 0.9\,(\rm syst.) ] \times 10^{-4}$ for $π$-tagged and $ΔA_{C\!P} = [ -9 \pm 8\,(\rm stat.) \pm 5\,(\rm syst.) ] \times 10^{-4} $ for $μ$-tagged $D^0$ mesons. Combining these with previous LHCb results leads to $$ΔA_{C\!P} = ( -15.4 \pm 2.9) \times 10^{-4},$$ where the uncertainty includes both statistical and systematic contributions. The measured value differs from zero by more than five standard deviations. This is the first observation of $C\!P$ violation in the decay of charm hadrons.

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arXiv2019

Study of the $B^0\to ρ(770)^0 K^*(892)^0$ decay with an amplitude analysis of $B^0\to (π^+π^-) (K^+π^-)$ decays

An amplitude analysis of ${B^0\to (π^+π^-) (K^+π^-)}$ decays is performed in the two-body invariant mass regions ${300 < m(π^+π^-)<1100}$ MeV/$c^2$, accounting for the $ρ^0$, $ω$, $f_0(500)$, $f_0(980)$ and $f_0(1370)$ resonances, and ${750 < m(K^+π^-)<1200}$ MeV/$c^2$, which is dominated by the $K^{*}(892)^0$ meson. The analysis uses 3 fb$^{-1}$ of proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The $CP$ averages and asymmetries are measured for the magnitudes and phase differences of the contributing amplitudes. The $CP$-averaged longitudinal polarisation fractions of the vector-vector modes are found to be $\tilde{f}^0_{ρK^{*}} = 0.164 \pm 0.015 \pm 0.022$ and $\tilde{f}^0_{ωK^{*}} = 0.68 \pm 0.17 \pm 0.16$, and their $CP$ asymmetries, $\mathcal{A}^0_{ρK^{*}} = -0.62 \pm 0.09 \pm 0.09$ and $\mathcal{A}^0_{ωK^{*}} = -0.13 \pm 0.27 \pm 0.13$, where the first uncertainty is statistical and the second systematic.

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arXiv2019

Search for $CP$ violation in $D_s^+\to K_S^0 π^+$, $D^+\to K_S^0 K^+$ and $D^+\to ϕπ^+$ decays

A search for charge-parity ($CP$) violation in Cabibbo-suppressed $D_s^+\to K_S^0 π^+$, $D^+\to K_S^0 K^+$ and $D^+\to ϕπ^+$ decays is reported using proton-proton collision data, corresponding to an integrated luminosity of 3.8 fb$^{-1}$, collected at a center-of-mass energy of 13 TeV with the LHCb detector. High-yield samples of kinematically and topologically similar Cabibbo-favored $D_{(s)}^+$ decays are analyzed to subtract nuisance asymmetries due to production and detection effects, including those induced by $CP$ violation in the neutral kaon system. The results are \begin{align*} \mathcal{A}_{CP}(D_s^+\to K_S^0 π^+) &=\left(\phantom{-}1.3\phantom{0}\pm1.9\phantom{0}\pm0.5\phantom{0}\right)\times10^{-3},\\ \mathcal{A}_{CP}(D^+\to K_S^0 K^+) &=\left(-0.09\pm0.65\pm0.48\right)\times10^{-3},\\ \mathcal{A}_{CP}(D^+\to ϕπ^+) &=\left(\phantom{-}0.05\pm0.42\pm0.29\right)\times10^{-3}, \end{align*} where the first uncertainties are statistical and the second systematic. They are the most precise measurements of these quantities to date, and are consistent with $CP$ symmetry.

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