arXiv subjects

A. Battig

Publications and source records attributed to A. Battig.

241 records · Page 14Linked to original sources

arXiv2019

Observation of the doubly Cabibbo-suppressed decay $Ξ_{c}^{+}\to pϕ$

The doubly Cabibbo-suppressed decay $Ξ_{c}^{+}\to pϕ$ with $ϕ\to K^{+}K^{-}$ is observed for the first time, with a statistical significance of more than fifteen standard deviations. The data sample used in this analysis corresponds to an integrated luminosity of 2 fb$^{-1}$ recorded with the LHCb detector in $pp$ collisions at a centre-of-mass energy of 8 TeV. The ratio of branching fractions between the decay $Ξ_{c}^{+}\to pϕ$ and the singly Cabibbo-suppressed decay $Ξ_{c}^{+}\to pK^{-}π^{+}$ is measured to be \begin{equation*} \frac{\mathcal{B}(Ξ_{c}^{+}\to pϕ)}{\mathcal{B}(Ξ_{c}^{+}\to pK^{-}π^{+})} = (19.8 \pm 0.7 \pm 0.9 \pm 0.2) \times 10^{-3}, \end{equation*} where the first uncertainty is statistical, the second systematic and the third due to the knowledge of the $ϕ\to K^{+}K^{-}$ branching fraction.

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arXiv2019

Measurement of the branching fractions of the decays $D^+\rightarrow K^-K ^+K^+$, $D^+\rightarrow π^-π^+K^+$ and $D^+_s\rightarrow π^-K^+K^+$

The branching fractions of the doubly Cabibbo-suppressed decays $D^+\rightarrow K^-K^+K^+$, $D^+\rightarrow π^-π^+K^+$ and $D^+_s\rightarrowπ^-K^+K^+$ are measured using the decays $D^+\rightarrow K^-π^+π^+$ and $D^+_s\rightarrow K^-K^+π^+$ as normalisation channels. The measurements are performed using proton-proton collision data collected with the LHCb detector at a centre-of-mass energy of 8 TeV, corresponding to an integrated luminosity of 2.0 fb$^{-1}$. The results are \begin{align} \frac {\mathcal{B}(D^+\rightarrow K^-K^+K^+)} {\mathcal{B}(D^+\rightarrow K^-π^+π^+)}& = (6.541 \pm 0.025 \pm 0.042) \times 10^{-4},\nonumber \frac {\mathcal{B}(D^+\rightarrow π^-π^+K^+)} {\mathcal{B}(D^+\rightarrow K^-π^+π^+)}& = (5.231 \pm 0.009 \pm 0.023) \times 10^{-3}, \nonumber \frac {\mathcal{B}(D^+_s\rightarrowπ^-K^+K^+)} {\mathcal{B}(D^+_s\rightarrow K^-K^+π^+)}& = (2.372 \pm 0.024 \pm 0.025) \times 10^{-3},\nonumber \end{align} where the uncertainties are statistical and systematic, respectively. These are the most precise measurements up to date.

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arXiv2019

Measurement of $B^+$, $B^0$ and $Λ_b^0$ production in $p\mkern 1mu\mathrm{Pb}$ collisions at $\sqrt{s_\mathrm{NN}}=8.16\,{\rm TeV}$

The production of $B^+$, $B^0$ and $Λ_b^0$ hadrons is studied in proton-lead collisions at a centre-of-mass energy per nucleon pair of $\sqrt{s_\mathrm{NN}}=8.16\,{\rm TeV}$ recorded with the LHCb detector at the LHC. The measurement uses a dataset corresponding to an integrated luminosity of $12.2\pm0.3\,\mathrm{nb}^{-1}$ for the case where the proton beam is projected into the LHCb detector (corresponding to measuring hadron production at positive rapidity) and $18.6\pm0.5\,\mathrm{nb}^{-1}$ for the lead beam projected into the LHCb detector (corresponding to measuring hadron production at negative rapidity). Nuclear effects are probed through double-differential cross-sections, forward-to-backward cross-section ratios and nuclear modification factors of the beauty hadrons. The double-differential cross-sections are measured as a function of the beauty-hadron transverse momentum and rapidity in the nucleon-nucleon centre-of-mass frame. Forward-to-backward cross-section ratios and nuclear modification factors indicate a significant nuclear suppression at positive rapidity. The ratio of $Λ_b^0$ over $B^0$ production cross-sections is reported and is consistent with the corresponding measurement in $pp$~collisions.

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arXiv2019

Measurement of the mass and production rate of $Ξ_b^-$ baryons

The first measurement of the production rate of $Ξ_b^-$ baryons in $pp$ collisions relative to that of $Λ_b^0$ baryons is reported, using data samples collected by the LHCb experiment, and corresponding to integrated luminosities of $1$, $2$ and $1.6$ fb$^{-1}$ at $\sqrt{s}=7,~8$ and $13$ TeV, respectively. In the kinematic region $2 < η< 6$ and $p_{\rm T}<20$ GeV/$c$, we measure \begin{align*} \frac{f_{Ξ_b^-}}{f_{Λ_b^0}}\frac{\mathcal{B}(Ξ_b^-\to J/ψΞ^-)}{\mathcal{B}(Λ_b^0\to J/ψΛ)} &= (10.8\pm0.9\pm0.8)\times10^{-2}~~[\sqrt{s}=7,8~{\rm TeV}],\\ \frac{f_{Ξ_b^-}}{f_{Λ_b^0}}\frac{\mathcal{B}(Ξ_b^-\to J/ψΞ^-)}{\mathcal{B}(Λ_b^0\to J/ψΛ)} &= (13.1\pm1.1\pm1.0)\times10^{-2}~~[\sqrt{s}=13~{\rm TeV}], \end{align*} where $f_{Ξ_b^-}$ and $f_{Λ_b^0}$ are the fragmentation fractions of $b$ quarks into $Ξ_b^-$ and $Λ_b^0$ baryons, respectively, ${\mathcal{B}}$ represents branching fractions, and the uncertainties are due to statistical and experimental systematic sources. The values of $f_{Ξ_b^-}/f_{Λ_b^0}$ are obtained by invoking SU(3) symmetry in the $Ξ_b^-\to JψΞ^-$ and $Λ_b^0\to J/ψΛ$ decays. Production asymmetries between $Ξ_b^-$ and $\barΞ_b^+$ baryons are also reported. The mass of the $Ξ_b^-$ baryon is also measured relative to that of the $Λ_b^0$ baryon, from which it is found that \begin{align*} m(Ξ_b^-) &= 5796.70\pm0.39\pm0.15\pm0.17~{\rm MeV}/c^2, \end{align*} where the last uncertainty is due to the precision on the known $Λ_b^0$ mass. This result represents the most precise determination of the $Ξ_b^-$ mass.

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arXiv2019

Search for $CP$ violation through an amplitude analysis of $D^0 \rightarrow K^+ K^- π^+ π^-$ decays

A search for $CP$ violation in the Cabibbo-suppressed $D^0 \rightarrow K^+ K^- π^+ π^-$ decay mode is performed using an amplitude analysis. The measurement uses a sample of $pp$ collisions recorded by the LHCb experiment during 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb$^{-1}$. The $D^0$ mesons are reconstructed from semileptonic $b$-hadron decays into $D^0μ^- X$ final states. The selected sample contains more than 160000 signal decays, allowing the most precise amplitude modelling of this $D^0$ decay to date. The obtained amplitude model is used to perform the search for $CP$ violation. The result is compatible with $CP$ symmetry, with a sensitivity ranging from 1% to 15% depending on the amplitude considered.

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arXiv2019

Measurement of the charm-mixing parameter $y_{CP}$

A measurement of the charm-mixing parameter $y_{CP}$ using $D^0 \to K^+ K^-$, $D^0 \to π^+ π^-$, and $D^0 \to K^- π^+$ decays is reported. The $D^0$ mesons are required to originate from semimuonic decays of $B^-$ and $\overline{B}^0$ mesons. These decays are partially reconstructed in a data set of proton-proton collisions at center-of-mass energies of 7 and 8 TeV collected with the LHCb experiment and corresponding to an integrated luminosity of 3 fb$^{-1}$. The $y_{CP}$ parameter is measured to be $(0.57 \pm 0.13(\rm{stat.}) \pm 0.09(\rm{syst.}))\%$, in agreement with, and as precise as, the current world-average value.

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arXiv2018

Evidence for an $η_c(1S) π^-$ resonance in $B^0 \to η_c(1S) K^+π^-$ decays

A Dalitz plot analysis of $B^0 \to η_c(1S) K^+π^-$ decays is performed using data samples of $pp$ collisions collected with the LHCb detector at centre-of-mass energies of $\sqrt{s}=7,~8$ and $13$ TeV, corresponding to a total integrated luminosity of $4.7~\text{fb}^{-1}$. A satisfactory description of the data is obtained when including a contribution representing an exotic $η_c(1S) π^-$ resonant state. The significance of this exotic resonance is more than three standard deviations, while its mass and width are $4096 \pm 20~^{+18}_{-22}$ MeV and $152 \pm 58~^{+60}_{-35}$ MeV, respectively. The spin-parity assignments $J^P=0^+$ and $J^{P}=1^-$ are both consistent with the data. In addition, the first measurement of the $B^0 \to η_c(1S) K^+π^-$ branching fraction is performed and gives $\displaystyle \mathcal{B}(B^0 \to η_c(1S) K^+π^-) = (5.73 \pm 0.24 \pm 0.13 \pm 0.66) \times 10^{-4}$, where the first uncertainty is statistical, the second systematic, and the third is due to limited knowledge of external branching fractions.

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