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Measurement of $CP$ violation parameters in $B^0 \to D K^{*0}$ decays

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Abstract

An analysis of B0->D K*0 decays is presented, where D represents an admixture of D0 and D0b mesons reconstructed in four separate final states: K-pi+, pi-K+, K+K- and pi+pi-. The data sample corresponds to 3.0fb-1 of proton-proton collision, collected by the LHCb experiment. Measurements of several observables are performed, including CP asymmetries. The most precise determination is presented of rB(DK*0), the magnitude of the ratio of the amplitudes of the decay B0->D K+ pi- with a b->u or a b->c transition, in a K pi mass region of +/-50 MeV/c2 around the K*(892) mass and for an absolute value of the cosine of the K*0 helicity angle larger than 0.4.

Figures and captions

Feynman diagrams of {\it(left)} $ B ^0 \rightarrow D ^0 K ^{*0} $ and {\it (right)} $ B ^0 \rightarrow \overline{ D }{} {}^0 K ^{*0} $.

feynma[..].pdf [1 MiB]
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Background-subtracted $ K ^{*0} \rightarrow K ^+ \pi ^- $ invariant mass for $ B ^0 \rightarrow D ( K ^+ \pi ^- ) K ^{*0} $ signal candidates. The data (points) and the fit described in the text (solid line) are shown. The dashed line represents the $ K ^{*0} $ signal and the filled area the non- $ K ^{*0}$ contribution to the $ B ^0 \rightarrow D K ^{*0} $ signal. The vertical dotted lines indicate the invariant mass region used in the analysis.

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kstarmm_1.pdf

Distributions of (top left) $ D (\pi ^- K ^+ ) \overline{ K }{} {}^{*0} $, (top right) $ D (\pi ^+ K ^- ) K ^{*0} $, (bottom left) $ D ( K ^- \pi ^+ ) \overline{ K }{} {}^{*0} $ and (bottom right) $ D ( K ^+ \pi ^- ) K ^{*0} $ invariant mass. The data (black points) and the fitted invariant mass model (thick solid line) are shown. The PDFs corresponding to the different species are indicated in the legend: the $ B ^0 $ signal, the $ B ^0_ s $ signal, combinatorial background, $ B ^0 \rightarrow D \rho^0$ background, partially reconstructed $ B ^0_ s \rightarrow D ^* \overline{ K }{} {}^{*0} $ and $ B ^0 \rightarrow D ^* K ^{*0} $ backgrounds.

b0bar_[..].pdf [1 MiB]
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b0bar_os_massfit_final_3.pdf
b0_os_[..].pdf [1 MiB]
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b0_os_massfit_final_3.pdf
b0bar_[..].pdf [1 MiB]
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b0bar_ss_massfit_final_3.pdf
b0_ss_[..].pdf [1 MiB]
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b0_ss_massfit_final_3.pdf

Distributions of (top left) $ D ( K ^+ K ^- ) \overline{ K }{} {}^{*0} $, (top right) $ D ( K ^+ K ^- ) K ^{*0} $, (bottom left) $ D (\pi ^+ \pi ^- ) \overline{ K }{} {}^{*0} $ and (bottom right) $ D (\pi ^+ \pi ^- ) K ^{*0} $ invariant mass. The data (black points) and the fitted invariant mass model (thick solid line) are shown. The PDFs corresponding to the different species are indicated in the legend: the $ B ^0 $ signal, the $ B ^0_ s $ signal, combinatorial background, $ B ^0 \rightarrow D \rho^0$ background and partially reconstructed $ B ^0_ s \rightarrow D ^* \overline{ K }{} {}^{*0} $ and $ B ^0 \rightarrow D ^* K ^{*0} $ backgrounds.

b0bar_[..].pdf [1 MiB]
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b0bar_kk_massfit_final_3.pdf
b0_kk_[..].pdf [1 MiB]
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b0_kk_massfit_final_3.pdf
b0bar_[..].pdf [1 MiB]
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b0bar_pipi_massfit_final_3.pdf
b0_pip[..].pdf [1 MiB]
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b0_pipi_massfit_final_3.pdf

$p$-value as a function of $r_{ B }$, for $\kappa=0.95\pm0.03$. The horizontal dashed lines represent the $1\sigma$ and $2\sigma$ confidence levels and the vertical dotted line represents the obtained central value.

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rb_scan_1d.pdf

Two-dimensional projections of the $p$-value in $(r_B,\delta_B,\gamma )$ parameter space onto (left) $r_{ B }$ and $\gamma$ and (right) $\delta_{ B }$ and $\gamma$, for $\kappa=0.95\pm0.03$. The contours are the $n\sigma$ profile likelihood contours, where $\Delta\chi^2 = n^2$ with $n = 1$ (black), 2 (medium grey), and 3 (light gray), corresponding to 39.4%, 86.5% and 98.9% confidence level, respectively. The vertical line and hashed band represent the best-fit value of $\gamma $ and the 68.3% confidence level interval by Ref. [3].

newcon[..].pdf [1 MiB]
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newcontour_gamma_rb.pdf
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newcontour_gamma_deltab.pdf

Animated gif made out of all figures.

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Tables and captions

Yields of signal candidates with their statistical uncertainties.

Table_1.pdf [51 KiB]
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Table_1.pdf

Uncertainties in the observables. All model-related systematic uncertainties are added in quadrature and the result is shown as one source of systematic uncertainty. The presence of `--' indicates that the source of uncertainty does not affect the observable.

Table_2.pdf [55 KiB]
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Table_2.pdf

Supplementary Material [file]

Supplementary material full pdf

supple[..].pdf [74 KiB]
supplementary.pdf

Created on 09 December 2018.Citation count from INSPIRE on 09 December 2018.