arXiv subjects

D. Berninghoff

Publications and source records attributed to D. Berninghoff.

At least 127 records · Page 7Linked to original sources

arXiv2021

Measurement of $C\!P$ observables in $B^\pm \to D^{()} K^\pm$ and $B^\pm \to D^{()} π^\pm$ decays using two-body $D$ final states

Measurements of $C\!P$ observables in $B^\pm \rightarrow D^{(*)} K^\pm$ and $B^\pm \rightarrow D^{(*)} π^\pm$ 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 $Dπ^0$ and $Dγ$ final states are partially reconstructed without inclusion of the neutral pion or photon. Decays of the $D$ meson are reconstructed in the $K^\pm π^\mp$, $K^+K^-$, 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 $B^\pm \to D^* K^\pm$ and $B^\pm \to D^* π^\pm$ with $D \to K^\mp π^\pm$ decays are the first of their kind, and a first observation of the $B^\pm \to (D π^0)_{D^*} π^\pm$ decay is made with a significance of 6.1 standard deviations. All $C\!P$ observables are measured with world-best precision, and in combination with other LHCb results will provide strong constraints on the CKM angle $γ$.

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arXiv2021

Measurement of the CKM angle $γ$ and $B^0_s$-$\bar{B}^0_s$ mixing frequency with $B^0_s \rightarrow D_s^\mp h^\pm π^\pm π^\mp$ decays

The CKM angle $γ$ is measured for the first time from mixing-induced $CP$ violation between $B^0_s \rightarrow D_s^\mp K^\pm π^\pm π^\mp$ and $\bar{B}^0_s \rightarrow D_s^\pm K^\mp π^\mp π^\pm$ decays reconstructed in proton-proton collision data corresponding to an integrated luminosity of 9 ${\rm fb}^{-1}$ recorded with the LHCb detector. A time-dependent amplitude analysis is performed to extract the $CP$-violating weak phase $γ-2β_s$ and, subsequently, $γ$ by taking the $B^0_s$-$\bar{B}^0_s$ mixing phase $β_{s}$ as an external input. The measurement yields $γ= (44 \pm 12)^\circ$ modulo $180^\circ$, where statistical and systematic uncertainties are combined. An alternative model-independent measurement, integrating over the five-dimensional phase space of the decay, yields $γ= (44^{\,+\,20}_{\,-\,13})^\circ$ modulo $180^\circ$. Moreover, the $B^0_s$-$\bar{B}^0_s$ oscillation frequency is measured from the flavour-specific control channel $B^0_s \rightarrow D_s^- π^+ π^+ π^-$ to be $Δm_s = (17.757 \pm 0.007 \,({\rm stat.}) \pm 0.008 \,({\rm syst.})) \text{ps}^{-1}$, consistent with and more precise than the current world-average value.

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arXiv2021

Search for long-lived particles decaying to $e^\pm μ^\mp ν$

Long-lived particles decaying to $e^\pm μ^\mp ν$, with masses between 7 and $50$ GeV/c$^2$ and lifetimes between 2 and $50$ ps, are searched for by looking at displaced vertices containing electrons and muons of opposite charges. The search is performed using $5.4$ fb$^{-1}$ of $pp$ collisions collected with the LHCb detector at a centre-of-mass energy of $\sqrt{s} = 13$ TeV. Three mechanisms of production of long-lived particles are considered: the direct pair production from quark interactions, the pair production from the decay of a Standard-Model-like Higgs boson with a mass of $125$ GeV/c$^2$, and the charged current production from an on-shell $W$ boson with an additional lepton. No evidence of these long-lived states is obtained and upper limits on the production cross-section times branching fraction are set on the different production modes.

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arXiv2021

Observation of a new excited $D_s^+$ meson in $B^0\to D^-D^+K^+π^-$ decays

Using $pp$ collision data corresponding to an integrated luminosity of $5.4\,{\rm fb}^{-1}$ collected with the LHCb detector at a center-of-mass energy of $13\,{\rm TeV}$, the $B^0\to D^-D^+K^+π^-$ 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 $m_R=2591\pm6\pm7\,{\rm MeV}$, $Γ_R=89\pm16\pm12\,{\rm MeV}$ 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.

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arXiv2021

Search for heavy neutral leptons in $W^+\toμ^{+}μ^{\pm}\text{jet}$ decays

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.

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arXiv2021

Search for the rare decay $B^0 \rightarrow J/ψϕ$

A search for the rare decay $B^0 \rightarrow J/ψϕ$ is performed using $pp$ collision data collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 ${\rm fb}^{-1}$. No significant signal of the decay is observed and an upper limit of $1.1 \times 10^{-7}$ at 90% confidence level is set on the branching fraction.

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arXiv2021

Observation of the $B_s^0 \rightarrow D^{\ast \pm} D^{\mp}$ decay

A search for the $B^0_s \!\rightarrow D^{*\pm} D^\mp$ decay is performed using proton-proton collision data at centre-of-mass energies of $7$, $8$ and $13\,\text{TeV}$ collected by the LHCb experiment, corresponding to an integrated luminosity of $9\,\text{fb}^{-1}$. The decay is observed with a high significance and its branching fraction relative to the $B^0 \!\rightarrow D^{*\pm} D^\mp$ decay is measured to be \begin{align*} \frac{\mathcal{B}(B_s^0 \rightarrow D^{\ast \pm} D^{\mp}) }{\mathcal{B}(B^0 \rightarrow D^{\ast \pm} D^{\mp}) } = 0.137 \pm 0.017 \pm 0.002 \pm 0.006 \,, \end{align*} where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the ratio of the $B_s^0$ and $B^0$ hadronisation fractions.

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arXiv2021

Observation of the decay $Λ_b^0\rightarrowχ_{c1}pπ^-$

The Cabibbo-suppressed decay $Λ_b^0\rightarrowχ_{c1}pπ^-$ is observed for the first time using data from proton-proton collisions corresponding to an integrated luminosity of 6fb$^{-1}$, collected with the LHCb detector at a centre-of-mass energy of 13TeV. Evidence for the $Λ_b^0\rightarrowχ_{c2}pπ^-$ decay is also found. Using the $Λ_b^0\rightarrowχ_{c1}pK^-$ decay as normalisation channel, the ratios of branching fractions are measured to be $$\begin{array}{rcl} \frac{ \mathcal{B} (Λ_b^0\rightarrowχ_{c1}pπ^-)}{\mathcal{B} (Λ_b^0\rightarrowχ_{c1}pK^-)} & = & (6.59 \pm 1.01 \pm 0.22 ) \times 10^{-2} \,, \frac{\mathcal{B} (Λ_b^0\rightarrowχ_{c2}pπ^-)}{\mathcal{B} (Λ_b^0\rightarrowχ_{c1}pπ^-)} & = & 0.95 \pm 0.30 \pm 0.04 \pm 0.04 \,, \frac{\mathcal{B} (Λ_b^0\rightarrowχ_{c2}pK^-)}{\mathcal{B} (Λ_b^0\rightarrowχ_{c1}pK^-)} & = & 1.06 \pm 0.05 \pm 0.04 \pm 0.04 \,,\end{array}$$ where the first uncertainty is statistical, the second is systematic and the third is due to the uncertainties in the branching fractions of $χ_{c1,2}\rightarrow J/ψγ$ decays.

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arXiv2021

Study of the lineshape of the $χ_{c1}(3872)$ state

A study of the lineshape of the $χ_{c1}(3872)$ state is made using a data sample corresponding to an integrated luminosity of $3\,$fb$^{-1}$ collected in $pp$ collisions at centre-of-mass energies of 7 and 8\,TeV with the LHCb detector. Candidate $χ_{c1}(3872)$ and $ψ(2S)$ mesons from b-hadron decays are selected in the $ J/ψπ^+ π^-$ decay mode. Describing the {\mbox{lineshape}} with a Breit--Wigner function, the mass splitting between the $χ_{c1}(3872)$ and $ψ(2S)$ states, $Δm$, and the width of the $χ_{c1}(3872)$ state, $Γ_{\mathrm{BW}}$, are determined to be \begin{eqnarray*} Δm & = & 185.598 \pm 0.067 \pm 0.068\, \mathrm{MeV} \,, \\ Γ_{\mathrm{BW}} & = & \phantom{00}1.39\phantom{0} \pm 0.24\phantom{0} \pm 0.10\phantom{0} \mathrm{MeV} \,, \end{eqnarray*} where the first uncertainty is statistical and the second systematic. Using a Flatté-inspired model, the mode and full width at half maximum of the lineshape are determined to be \begin{eqnarray*} \mathrm{mode} & = 3871.69^{\,+\,0.00\,+\,0.05}_{\,-\,0.04\,-\,0.13} &\mathrm{MeV} \\ \mathrm{FWHM} & = 0.22^{\,+\,0.07\,+\,0.11}_{\,-\,0.06\,-\,0.13}& \mathrm{MeV} . \end{eqnarray*} An investigation of the analytic structure of the Flatté amplitude reveals a pole structure, which is compatible with a quasi-bound $D^0\bar{D}^{*0}$ state but a quasi-virtual state is still allowed at the level of $2$ standard deviations.

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arXiv2021

Observation of $CP$ violation in two-body $B_{(\mathrm{s})}^{\,0}$-meson decays to charged pions and kaons

The time-dependent $CP$ asymmetries of $B^0\to π^+π^-$ and $B^0_\mathrm{s}\!\to K^+K^-$ decays are measured using a data sample of $pp$ collisions corresponding to an integrated luminosity of 1.9 fb$^{-1}$, collected with the LHCb detector at a centre-of-mass energy of 13 TeV. The results are \begin{eqnarray*} C_{ππ} & = & -0.311 \pm 0.045 \pm 0.015, \\ S_{ππ} & = & -0.706 \pm 0.042 \pm 0.013, \\ C_{KK} & = & \phantom{-}0.164 \pm 0.034 \pm 0.014, \\ S_{KK} & = & \phantom{-}0.123 \pm 0.034 \pm 0.015, \\ \cal {A}^{\mathrm{ΔΓ}}_{\mathit{KK}} & = & -0.83\phantom{0} \pm 0.05\phantom{0} \pm 0.09, \end{eqnarray*} where the first uncertainties are statistical and the second systematic. The same data sample is used to measure the time-integrated $CP$ asymmetries of $B^0\to K^+π^-$ and $B^0_\mathrm{s}\to K^-π^+$ decays and the results are \begin{eqnarray*} A_{CP}^{B^0} & = & -0.0824 \pm 0.0033 \pm 0.0033, \\ A_{CP}^{B^0_\mathrm{s}} & = & \phantom{-}0.236\phantom{0} \pm 0.013\phantom{0} \pm 0.011. \end{eqnarray*} All results are consistent with earlier measurements. A combination of LHCb measurements provides the first observation of time-dependent $CP$ violation in $B^0_\mathrm{s}$ decays.

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arXiv2021

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

The production of $χ_{c1}(3872)$ 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 $χ_{c1}(3872)$ 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 $χ_{c1}(3872)$ structure as a compact tetraquark. Comparisons with model calculations and implications for the binding energy of the $χ_{c1}(3872)$ state are discussed.

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arXiv2021

Measurement of the CKM angle $γ$ in $B^\pm\to D K^\pm$ and $B^\pm \to D π^\pm$ decays with $D \to K_\mathrm S^0 h^+ h^-$

A measurement of $CP$-violating observables is performed using the decays $B^\pm\to D K^\pm$ and $B^\pm\to D π^\pm$, where the $D$ meson is reconstructed in one of the self-conjugate three-body final states $K_{\mathrm S}π^+π^-$ and $K_{\mathrm S}K^+K^-$ (commonly denoted $K_{\mathrm S} h^+h^-$). The decays are analysed in bins of the $D$-decay phase space, leading to a measurement that is independent of the modelling of the $D$-decay amplitude. The observables are interpreted in terms of the CKM angle $γ$. Using a data sample corresponding to an integrated luminosity of $9\,\text{fb}^{-1}$ collected in proton-proton collisions at centre-of-mass energies of $7$, $8$, and $13\,\text{TeV}$ with the LHCb experiment, $γ$ is measured to be $\left(68.7^{+5.2}_{-5.1}\right)^\circ$. The hadronic parameters $r_B^{DK}$, $r_B^{Dπ}$, $δ_B^{DK}$, and $δ_B^{Dπ}$, which are the ratios and strong-phase differences of the suppressed and favoured $B^\pm$ decays, are also reported.

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arXiv2021

Observation of the $\varLambda^0_b \to \varLambda^+_c K^+ K^- π^-$ decay

The $\varLambda^0_b \to \varLambda^+_c K^+ K^- π^-$ decay is observed for the first time using a data sample of proton-proton collisions at centre-of-mass energies of $\sqrt{s}=7$ and 8 $\rm{TeV}$ collected by the $\mbox{LHCb}$ detector, corresponding to an integrated luminosity of $3{\rm{fb}^{-1}}$. The ratio of branching fractions between the $\varLambda^0_b \to \varLambda^+_c K^+ K^- π^-$ and the $\varLambda^{0}_{b}\to\varLambda^{+}_{c}D^{-}_{s}$ decays is measured to be \begin{equation*} \frac{\mathcal{B} ( \varLambda^0_b \to \varLambda^+_c K^+ K^- π^-) } {\mathcal{B} ( \varLambda^0_b \to \varLambda^+_c D^-_s)} = (9.26 \pm 0.29 \pm 0.46 \pm 0.26)\times10^{-2}, \end{equation*} where the first uncertainty is statistical, the second systematic and the third is due to the knowledge of the $D^-_s \to K^+ K^- π^-$ branching fraction. No structure on the invariant mass distribution of the $\varLambda^+_c K^+$ system is found, consistent with no open-charm pentaquark signature.

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arXiv2021

Measurement of CP violation in the decay $B^{+} \rightarrow K^{+} π^{0}$

A measurement of direct CP violation in the decay $B^{+} \rightarrow K^{+} π^{0}$ is reported using a data sample corresponding to an integrated luminosity of 5.4 $\textrm{fb}^{-1}$, collected with the LHCb experiment at a center-of-mass energy of $\sqrt{s}=13$ TeV. The CP asymmetry is measured to be $0.025 \pm 0.015 \pm 0.006 \pm 0.003$, where the uncertainties are statistical, systematic, and due to an external input, respectively. This is the most precise measurement of the CP asymmetry in the decay $B^{+} \rightarrow K^{+} π^{0}$ and exceeds the precision on the current world average. This direct CP asymmetry is a key input to studies of a long-standing anomaly in $B$ meson decays, known as the $Kπ$-puzzle. The asymmetry is consistent with the previous measurements of this quantity, confirming and significantly enhancing the observed anomalous difference between the direct CP asymmetries of the $B^{0} \rightarrow K^{+} π^{-}$ and $B^{+} \rightarrow K^{+} π^{0}$ decays.

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arXiv2021

First observation of the decay $B_s^0 \to K^-μ^+ν_μ$ and a measurement of $|V_{ub}|/|V_{cb}|$

The first observation of the suppressed semileptonic $B_s^0 \to K^-μ^+ν_μ$ decay is reported. Using a data sample recorded in {\it pp} collisions in 2012 with the LHCb detector, corresponding to an integrated luminosity of 2 $\mathrm{fb}^{-1}$, the branching fraction \mbox{$\mathcal{B}(B_s^0 \to K^-μ^+ν_μ)$} is measured to be $(1.06\pm0.05~(\mathrm{stat})\pm0.08~(\mathrm{syst}))\times 10^{-4}$, where the first uncertainty is statistical and the second one represents the combined systematic uncertainties. The decay $B_s^0 \to D_s^-μ^+ν_μ$, 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 $B_s^0 \to K^-$ and $B_s^0 \to D_s^-$ transitions are employed to determine the ratio of the CKM matrix elements ${|V_{ub}|}/{|V_{cb}|}$ at low and high $B_s^0 \to K^-$ momentum transfer.

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arXiv2021

Measurement of differential $b\bar{b}$- and $c\bar{c}$-dijet cross-sections in the forward region of $pp$ collisions at $\sqrt{s}=13 ~ \mathrm{TeV}$

The inclusive $b \bar{b}$- and $c \bar{c}$-dijet production cross-sections in the forward region of $pp$ collisions are measured using a data sample collected with the LHCb detector at a centre-of-mass energy of 13 TeV in 2016. The data sample corresponds to an integrated luminosity of 1.6 fb$^{-1}$. Differential cross-sections are measured as a function of the transverse momentum and of the pseudorapidity of the leading jet, of the rapidity difference between the jets, and of the dijet invariant mass. A fiducial region for the measurement is defined by requiring that the two jets originating from the two $b$ or $c$ quarks are emitted with transverse momentum greater than 20 GeV$/c$, pseudorapidity in the range $2.2 < η< 4.2$, and with a difference in the azimuthal angle between the two jets greater than 1.5. The integrated $b \bar{b}$-dijet cross-section is measured to be $53.0 \pm 9.7$ nb, and the total $c \bar{c}$-dijet cross-section is measured to be $73 \pm 16$ nb. The ratio between $c \bar{c}$- and $b \bar{b}$-dijet cross-sections is also measured and found to be $1.37 \pm 0.27$. The results are in agreement with theoretical predictions at next-to-leading order.

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arXiv2021

Study of $B^0_s \rightarrow J/ψπ^+π^-K^+K^-$ decays

The decays $B^0_s \rightarrow J/ψπ^+π^- K^+ K^-$ are studied using a data set corresponding to an integrated luminosity of 9fb$^{-1}$, collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13TeV. The decays $B^0_s \rightarrow J/ψK^{\ast0} \bar{K}^{\ast0}$ and $B^0_s \rightarrow χ_{c1}(3872)K^+K^-$, where the $K^+K^-$ pair does not originate from a $ϕ$ meson, are observed for the first time. Precise measurements of the ratios of branching fractions between intermediate $χ_{c1}(3872)ϕ$, $J/ψK^{\ast0}\bar{K}^{\ast0}$, $ψ(2S)ϕ$ and $χ_{c1}(3872)K^+K^-$ states are reported. A structure, denoted as $X(4740)$, is observed in the $J/ψϕ$ mass spectrum and, assuming a Breit-Wigner parameterisation, its mass and width are determined to be \begin{eqnarray*} m_{X(4740)} & = & 4741 \pm 6 \pm 6\,{\mathrm{MeV}}/c^2 \,, \\ Γ_{X(4740)} & = & 53 \pm 15 \pm 11\,{\mathrm{MeV}} \,, \end{eqnarray*} where the first uncertainty is statistical and the second is systematic. In addition, the most precise single measurement of the mass of the $B^0_s$ meson is performed and gives a value of $$ m_{B^0_s} = 5366.98 \pm 0.07 \pm 0.13\,{\mathrm{MeV}}/c^2\,. $$

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arXiv2021

Constraints on the $K^0_{\mathrm{S}}\rightarrowμ^{+}μ^{-}$ branching fraction

A search for the decay $K^0_{\mathrm{S}}\rightarrowμ^{+}μ^{-}$ is performed using proton-proton collision data, corresponding to an integrated luminosity of $5.6\,\text{fb}^{-1}$ and collected with the LHCb experiment during 2016, 2017 and 2018 at a center-of-mass energy of $13\,\mathrm{TeV}$. The observed signal yield is consistent with zero, yielding an upper limit of ${\cal B}(K^0_{\mathrm{S}}\rightarrowμ^{+}μ^{-}) < 2.2 \times 10^{-10}$ at 90% CL. The limit reduces to ${\cal B}(K^0_{\mathrm{S}}\rightarrowμ^{+}μ^{-}) < 2.1 \times 10^{-10}$ at 90% CL once combined with the result from data taken in 2011 and 2012.

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