arXiv subjects

C. Burr

Publications and source records attributed to C. Burr.

At least 91 records · Page 5Linked to original sources

arXiv2017

Measurement of the ratio of branching fractions and difference in $CP$ asymmetries of the decays $B^+\to J/ψπ^+$ and $B^+\to J/ψK^+$

The ratio of branching fractions and the difference in $CP$ asymmetries of the decays $B^+\to J/ψπ^+$ and $B^+\to J/ψK^+$ are measured using a data sample of $pp$ collisions collected by the LHCb experiment, corresponding to an integrated luminosity of $3~{{\,\mbox{fb}^{-1}}}$ at centre-of-mass energies of 7 and $8~\mathrm{\,Te\kern -0.1em V}$. The results are \begin{equation*} {\mathcal{B}(B^+\to J/ψπ^+)\over\mathcal{B}(B^+\to J/ψK^+)}=(3.83\pm0.03\pm0.03)\times10^{-2}\,, \end{equation*} \begin{equation*} \mathcal{A}^{CP}(B^+\to J/ψπ^+)-\mathcal{A}^{CP}(B^+\to J/ψK^+)=(1.82\pm0.86\pm0.14)\times10^{-2}, \end{equation*} where the first uncertainties are statistical and the second are systematic. Combining this result with a recent LHCb measurement of $\mathcal{A}^{CP}(B^+\to J/ψK^+)$ provides the most precise estimate to date of $CP$ violation in the decay $B^+\to J/ψπ^+$, \begin{equation*} \mathcal{A}^{CP}(B^+\to J/ψπ^+) =(1.91\pm0.89\pm0.16)\times10^{-2}. \end{equation*}

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arXiv2017

Observation of the annihilation decay mode $B^{0}\to K^{+}K^{-}$

A search for the $B^{0}\to K^{+}K^{-}$ decay is performed using $pp$-collision data collected by LHCb. The data set corresponds to integrated luminosities of 1 and 2 fb$^{-1}$ at center-of-mass energies of 7 and 8 TeV, respectively. This decay is observed for the first time, with a significance of more than five standard deviations. The analysis also results in an improved measurement of the branching fraction for the $B_s^0\to π^+π^-$ decay. The measured branching fractions are $BR(B^0\to K^+K^-) = (7.80 \pm 1.27 \pm 0.81 \pm 0.21) \times 10^{-8}$ and $BR(B_s^0\toπ^+π^-) = (6.91 \pm 0.54 \pm 0.63 \pm 0.19 \pm 0.40) \times 10^{-7}$. The first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the $B^0\to K^+π^-$ branching fraction used as a normalization. For the $B_s^0$ mode, the fourth accounts for the uncertainty on the ratio of the probabilities for $b$ quarks to hadronize into $B_s^0$ and $B^0$ mesons.

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arXiv2017

First experimental study of photon polarization in radiative $B^{0}_{s}$ decays

The polarization of photons produced in radiative $B^{0}_{s}$ decays is studied for the first time. The data are recorded by the LHCb experiment in $pp$ collisions corresponding to an integrated luminosity of 3fb$^{-1}$ at center-of-mass energies of $7$ and $8$TeV. A time-dependent analysis of the $B^{0}_{s} \to ϕγ$ decay rate is conducted to determine the parameter ${\mathcal{A}}^Δ$, which is related to the ratio of right- over left-handed photon polarization amplitudes in $b \to s γ$ transitions. A value of ${\mathcal{A}}^Δ=-0.98^{\,+0.46\,+0.23}_{\,-0.52\,-0.20}$ is measured. This result is consistent with the Standard Model prediction within two standard deviations.

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arXiv2017

Observation of $B^+\rightarrow J/ψ3π^+ 2π^-$ and $B^+\rightarrow ψ(2S) π^+π^+π^-$ decays

The decays $B^+\rightarrow J/ψ3π^+ 2π^-$ and $B^+\rightarrow ψ(2S) π^+π^+π^-$ are observed for the first time using a data sample corresponding to an integrated luminosity of $3.0fb^{-1}$, collected by the LHCb experiment in proton-proton collisions at the centre-of-mass energies of 7 and 8 TeV. The branching fractions relative to that of $B^+ \rightarrow ψ(2S)K^+$ are measured to be \begin{eqnarray*} \frac {\mathcal{B}\left(B^+\rightarrow J/ψ3π^+ 2π^- \right)} {\mathcal{B}\left(B^+ \rightarrow ψ(2S)K^+ \right)} & = & \left(1.88\pm0.17\pm0.09\right)\times10^{-2}, \frac {\mathcal{B}\left(B^+\rightarrow ψ(2S) π^+π^+π^- \right)} {\mathcal{B}\left(B^+ \rightarrow ψ(2S)K^+ \right)} & = & \left(3.04\pm0.50\pm0.26\right)\times10^{-2}, \end{eqnarray*} where the first uncertainties are statistical and the second are systematic.

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arXiv2017

Observation of the decay $Ξ_b^- \to p K^-K^-$

Decays of the $Ξ_b^-$ and $Ω_b^-$ baryons to the charmless final states $p h^{-}h^{\prime -}$, where $h^{(\prime)}$ denotes a kaon or pion, are searched for with the LHCb detector. The analysis is based on a sample of proton-proton collision data collected at centre-of-mass energies $\sqrt{s} = 7$ and $8 TeV$, corresponding to an integrated luminosity of $3 {\rm fb}^{-1}$. The decay $Ξ_b^- \to p K^-K^-$ is observed with a significance of $8.7$ standard deviations, and evidence at the level of $3.4$ standard deviations is found for the $Ξ_b^- \to p K^-π^-$ decay. Results are reported, relative to the $B^-\to K^+K^-K^-$ normalisation channel, for the products of branching fractions and $b$-hadron production fractions. The branching fractions of $Ξ_b^- \to p K^-π^-$ and $Ξ_b^- \to p π^-π^-$ relative to $Ξ_b^- \to p K^-K^-$ decays are also measured.

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arXiv2017

Measurement of forward $t\overline{t}$, $W+b\overline{b}$ and $W+c\overline{c}$ production in $pp$ collisions at $\sqrt{s}=8$ TeV

The production of $t\overline{t}$, $W+b\overline{b}$ and $W+c\overline{c}$ is studied in the forward region of proton-proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98 $\pm$ 0.02 $\mbox{fb}^{-1}$. The $W$ bosons are reconstructed in the decays $W\rightarrow\ellν$, where $\ell$ denotes muon or electron, while the $b$ and $c$ quarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions.

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arXiv2017

Search for structure in the $B_s^0π^\pm$ invariant mass spectrum

The $B_s^0π^\pm$ invariant mass distribution is investigated in order to search for possible exotic meson states. The analysis is based on a data sample recorded with the LHCb detector corresponding to $3$ fb$^{-1}$ of $pp$ collision data at $\sqrt{s} = 7$ and $8$ TeV. No significant excess is found, and upper limits are set on the production rate of the claimed $X(5568)$ state within the LHCb acceptance. Upper limits are also set as a function of the mass and width of a possible exotic meson decaying to the $B_s^0π^\pm$ final state. The same limits also apply to a possible exotic meson decaying through the chain $B_s^{*0}π^\pm$, $B_s^{*0} \to B_s^0 γ$ where the photon is excluded from the reconstructed decays.

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arXiv2017

Search for the suppressed decays $B^{+}\rightarrow K^{+}K^{+}π^{-}$ and $B^{+}\rightarrow π^{+}π^{+}K^{-}$

A search is made for the highly-suppressed B meson decays $B^{+}\rightarrow K^{+}K^{+}π^{-}$ and $B^{+}\rightarrow π^{+}π^{+}K^{-}$ using a data sample corresponding to an integrated luminosity of 3.0 $fb^{-1}$ collected by the LHCb experiment in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. No evidence is found for the decays, and upper limits at 90\% confidence level are determined to be $\mathcal{B}(B^{+}\rightarrow K^{+}K^{+}π^{-}) < 1.1\times 10^{-8}$ and $\mathcal{B}(B^{+}\rightarrow π^{+}π^{+}K^{-}) < 4.6\times 10^{-8}$.

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arXiv2017

Search for the $C\!P$-violating strong decays $η\to π^+π^-$ and $η^\prime(958) \to π^+π^-$

A search for the $C\!P$-violating strong decays $η\to π^+π^-$ and $η^\prime(958) \to π^+π^-$ has been performed using approximately $2.5 \times 10^{7}$ events of each of the decays $D^+ \to π^+π^+π^-$ and $D_s^+ \to π^+π^+π^-$, recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0 fb$^{-1}$ of $pp$ collision data recorded during LHC Run 1 and 0.3 fb$^{-1}$ recorded in Run 2. No evidence is seen for $D^+_{(s)} \to π^+ η^{(\prime)}$ with $η^{(\prime)} \to π^+π^-$, and upper limits at 90% confidence level are set on the branching fractions, $\mathcal{B}(η\to π^+π^-) < 1.6 \times 10^{-5}$ and $\mathcal{B}(η^\prime \to π^+π^-) < 1.8 \times 10^{-5}$. The limit for the $η$ decay is comparable with the existing one, while that for the $η^\prime$ is a factor of three smaller than the previous limit.

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arXiv2017

Measurement of the $B_{s}^{0} \rightarrow J/ψη$ lifetime

Using a data set corresponding to an integrated luminosity of $3 fb^{-1}$, collected by the LHCb experiment in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV, the effective lifetime in the $B^0_s \rightarrow J/ψη$ decay mode, $τ_{\textrm{eff}}$, is measured to be $τ_{\textrm{eff}} = 1.479 \pm 0.034~\textrm{(stat)} \pm 0.011 ~\textrm{(syst)}$ ps. Assuming $CP$ conservation, $τ_{\textrm{eff}}$ corresponds to the lifetime of the light $B_s^0$ mass eigenstate. This is the first measurement of the effective lifetime in this decay mode.

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arXiv2017

Measurement of the $B^{\pm}$ production asymmetry and the $CP$ asymmetry in $B^{\pm} \to J/ψK^{\pm}$ decays

The $B^{\pm}$ meson production asymmetry in $pp$ collisions is measured using $B^+ \to \bar{D}^0 π^+$ decays. The data were recorded by the LHCb experiment during Run 1 of the LHC at centre-of-mass energies of $\sqrt{s}=$ 7 and 8 TeV. The production asymmetries, integrated over transverse momenta in the range $2 < p_{\rm T} < 30$ GeV/$c$, and rapidities in the range $2.1 < y < 4.5$, are measured to be \begin{align*} \mathcal{A}_{\rm prod}(B^+,\sqrt{s}=7~{\rm TeV}) &= (-0.41 \pm 0.49 \pm 0.10) \times 10^{-2},\\ \mathcal{A}_{\rm prod}(B^+,\sqrt{s}=8~{\rm TeV}) &= (-0.53 \pm 0.31 \pm 0.10) \times 10^{-2}, \end{align*} where the first uncertainties are statistical and the second are systematic. These production asymmetries are used to correct the raw asymmetries of $B^{+} \to J/ψK^{+}$ decays, thus allowing a measurement of the $CP$ asymmetry, \begin{equation*} \mathcal{A}_{CP} = (0.09 \pm 0.27 \pm 0.07) \times 10^{-2}. \end{equation*}

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arXiv2017

Amplitude analysis of $B^+\to J/ψϕK^+$ decays

The first full amplitude analysis of $B^+\to J/ψϕK^+$ with $J/ψ\toμ^+μ^-$, $ϕ\to K^+K^-$ decays is performed with a data sample of 3 fb$^{-1}$ of $pp$ collision data collected at $\sqrt{s}=7$ and $8$ TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into $ϕK^+$, and four $J/ψϕ$ structures are observed, each with significance over $5$ standard deviations. The quantum numbers of these structures are determined with significance of at least $4$ standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed $X(4140)$ state. The model includes significant contributions from a number of expected kaon excitations, including the first observation of the $K^{*}(1680)^+\toϕK^+$ transition.

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arXiv2017

Observation of $J/ψϕ$ structures consistent with exotic states from amplitude analysis of $B^+\to J/ψϕK^+$ decays

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arXiv2017

First study of the CP-violating phase and decay-width difference in $B_s^0\toψ(2S)ϕ$ decays

A time-dependent angular analysis of $B_s^0\toψ(2S)ϕ$ decays is performed using data recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0\invfb collected during Run 1 of the LHC. The CP-violating phase and decay-width difference of the $B_s^0$ system are measured to be $ϕ_s = 0.23^{+0.29}_{-0.28} \pm 0.02$ rad and $ΔΓ_s = 0.066^{+0.041}_{-0.044} \pm 0.007$ ps$^{-1}$, respectively, where the first uncertainty is statistical and the second systematic. This is the first time that $ϕ_s$ and $ΔΓ_s$ have been measured in a decay containing the $ψ(2S)$ resonance.

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arXiv2017

Observation of the decay $B^0_s \to ϕπ^+π^-$ and evidence for $B^0 \to ϕπ^+π^-$

The first observation of the rare decay$B^0_s \to ϕπ^+π^-$ and evidence for $B^0 \to ϕπ^+π^-$ are reported, using $pp$ collision data recorded by the LHCb detector at centre-of-mass energies $\sqrt{s} = 7$ and 8~TeV, corresponding to an integrated luminosity of $3{\mbox{\,fb}^{-1}}$. The branching fractions in the $π^+π^-$ invariant mass range $400<m(π^+π^-)<1600{\mathrm{\,Me\kern -0.1em V\!/}c^2}$ are $[3.48\pm 0.23\pm 0.17\pm 0.35]\times 10^{-6}$ and $[1.82\pm 0.25\pm 0.41\pm 0.14]\times 10^{-7}$ for $B^0_s \to ϕπ^+π^-$ and $B^0 \to ϕπ^+π^-$ respectively, where the uncertainties are statistical, systematic and from the normalisation mode $B^0_s \to ϕϕ$. A combined analysis of the $π^+π^-$ mass spectrum and the decay angles of the final-state particles identifies the exclusive decays $B^0_s \to ϕf_0(980) $, $B_s^0 \to ϕf_2(1270) $, and $B^0_s \to ϕρ^0$ with branching fractions of $[1.12\pm 0.16^{+0.09}_{-0.08}\pm 0.11]\times 10^{-6}$, $[0.61\pm 0.13^{+0.12}_{-0.05}\pm 0.06]\times 10^{-6}$ and $[2.7\pm 0.7\pm 0.2\pm 0.2]\times 10^{-7}$, respectively.

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arXiv2017

Measurement of $CP$ violation in $B^0 \!\rightarrow D^+ D^-$ decays

The $CP$ violation observables $S$ and $C$ in the decay channel $B^0 \!\rightarrow D^+ D^-$ are determined from a sample of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 3 fb$^{-1}$. The observable $S$ describes $CP$ violation in the interference between mixing and the decay amplitude, and $C$ parametrizes direct $CP$ violation in the decay. The following values are obtained from a flavor-tagged, decay-time-dependent analysis: \begin{align*} S &= -0.54 \, ^{+0.17}_{-0.16} \, \text{(stat)} \pm 0.05 \, \text{(syst)}\,,\newline C &= \phantom{-}0.26 \, ^{+0.18}_{-0.17} \, \text{(stat)} \pm 0.02 \, \text{(syst)}\,. \end{align*} These values provide evidence for $CP$ violation at a significance level of 4.0 standard deviations. The phase shift due to higher-order Standard Model corrections is constrained to a small value of \begin{align*} Δϕ= -0.16\,^{+0.19}_{-0.21}\,\text{rad}\,. \end{align*}

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arXiv2016

Differential branching fraction and angular moments analysis of the decay $B^0 \to K^+ π^- μ^+ μ^-$ in the $K^*_{0,2}(1430)^0$ region

Measurements of the differential branching fraction and angular moments of the decay $B^0 \to K^+ π^- μ^+ μ^-$ in the $K^+π^-$ invariant mass range $1330<m(K^+ π^-)<1530~MeV/c^2$ are presented. Proton-proton collision data are used, corresponding to an integrated luminosity of 3 $fb^{-1}$ collected by the LHCb experiment. Differential branching fraction measurements are reported in five bins of the invariant mass squared of the dimuon system, $q^2$, between 0.1 and 8.0 $GeV^2/c^4$. For the first time, an angular analysis sensitive to the S-, P- and D-wave contributions of this rare decay is performed. The set of 40 normalised angular moments describing the decay is presented for the $q^2$ range 1.1--6.0 $GeV^2/c^4$.

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arXiv2016

Measurement of the CKM angle $γ$ from a combination of LHCb results

A combination of measurements sensitive to the CKM angle $γ$ from LHCb is performed. The inputs are from analyses of time-integrated $B^{+}\rightarrow DK^+$, $B^{0} \rightarrow D K^{*0}$, $B^{0} \rightarrow D K^+ π^-$ and $B^{+} \rightarrow D K^+π^+π^-$ tree-level decays. In addition, results from a time-dependent analysis of $B_{s}^{0} \rightarrow D_{s}^{\mp}K^{\pm}$ decays are included. The combination yields $γ= (72.2^{+6.8}_{-7.3})^\circ$, where the uncertainty includes systematic effects. The 95.5% confidence level interval is determined to be $γ\in [55.9,85.2]^\circ$. A second combination is investigated, also including measurements from $B^{+} \rightarrow D π^+$ and $B^{+} \rightarrow D π^+π^-π^+$ decays, which yields compatible results.

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